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GCC(1)				      GNU				GCC(1)

NAME
       gcc - GNU project C and C++ compiler

SYNOPSIS
       gcc [-c|-S|-E] [-std=standard]
	   [-g]	[-pg] [-Olevel]
	   [-Wwarn...] [-Wpedantic]
	   [-Idir...] [-Ldir...]
	   [-Dmacro[=defn]...] [-Umacro]
	   [-foption...] [-mmachine-option...]
	   [-o outfile]	[@file]	infile...

       Only the	most useful options are	listed here; see below for the
       remainder.  g++ accepts mostly the same options as gcc.

DESCRIPTION
       When you	invoke GCC, it normally	does preprocessing, compilation,
       assembly	and linking.  The "overall options" allow you to stop this
       process at an intermediate stage.  For example, the -c option says not
       to run the linker.  Then	the output consists of object files output by
       the assembler.

       Other options are passed	on to one or more stages of processing.	 Some
       options control the preprocessor	and others the compiler	itself.	 Yet
       other options control the assembler and linker; most of these are not
       documented here,	since you rarely need to use any of them.

       Most of the command-line	options	that you can use with GCC are useful
       for C programs; when an option is only useful with another language
       (usually	C++), the explanation says so explicitly.  If the description
       for a particular	option does not	mention	a source language, you can use
       that option with	all supported languages.

       The usual way to	run GCC	is to run the executable called	gcc, or
       machine-gcc when	cross-compiling, or machine-gcc-version	to run a
       specific	version	of GCC.	 When you compile C++ programs,	you should
       invoke GCC as g++ instead.

       The gcc program accepts options and file	names as operands.  Many
       options have multi-letter names;	therefore multiple single-letter
       options may not be grouped: -dv is very different from -d -v.

       You can mix options and other arguments.	 For the most part, the	order
       you use doesn't matter.	Order does matter when you use several options
       of the same kind; for example, if you specify -L	more than once,	the
       directories are searched	in the order specified.	 Also, the placement
       of the -l option	is significant.

       Many options have long names starting with -f or	with -W---for example,
       -fmove-loop-invariants, -Wformat	and so on.  Most of these have both
       positive	and negative forms; the	negative form of -ffoo is -fno-foo.
       This manual documents only one of these two forms, whichever one	is not
       the default.

       Some options take one or	more arguments typically separated either by a
       space or	by the equals sign (=) from the	option name.  Unless
       documented otherwise, an	argument can be	either numeric or a string.
       Numeric arguments must typically	be small unsigned decimal or
       hexadecimal integers.  Hexadecimal arguments must begin with the	0x
       prefix.	Arguments to options that specify a size threshold of some
       sort may	be arbitrarily large decimal or	hexadecimal integers followed
       by a byte size suffix designating a multiple of bytes such as "kB" and
       "KiB" for kilobyte and kibibyte,	respectively, "MB" and "MiB" for
       megabyte	and mebibyte, "GB" and "GiB" for gigabyte and gigibyte,	and so
       on.  Such arguments are designated by byte-size in the following	text.
       Refer to	the NIST, IEC, and other relevant national and international
       standards for the full listing and explanation of the binary and
       decimal byte size prefixes.

OPTIONS
   Option Summary
       Here is a summary of all	the options, grouped by	type.  Explanations
       are in the following sections.

       Overall Options
	   -c	-S   -E	  -o file -dumpbase dumpbase  -dumpbase-ext auxdropsuf
	   -dumpdir  dumppfx   -x  language  -v	  -###	  --help[=class[,...]]
	   --target-help    --version	-pass-exit-codes   -pipe   -specs=file
	   -wrapper	@file	   -ffile-prefix-map=old=new	 -fplugin=file
	   -fplugin-arg-name=arg			-fdump-ada-spec[-slim]
	   -fada-spec-parent=unit  -fdump-go-spec=file

       C Language Options
	   -ansi		 -std=standard			-fgnu89-inline
	   -fpermitted-flt-eval-methods=standard       -aux-info      filename
	   -fallow-parameterless-variadic-functions   -fno-asm	  -fno-builtin
	   -fno-builtin-function   -fgimple -fhosted  -ffreestanding -fopenacc
	   -fopenacc-dim=geom	 -fopenmp     -fopenmp-simd    -fms-extensions
	   -fplan9-extensions			       -fsso-struct=endianness
	   -fallow-single-precision  -fcond-mismatch  -flax-vector-conversions
	   -fsigned-bitfields	     -fsigned-char	  -funsigned-bitfields
	   -funsigned-char

       C++ Language Options
	   -fabi-version=n	    -fno-access-control	       -faligned-new=n
	   -fargs-in-order=n	-fchar8_t    -fcheck-new   -fconstexpr-depth=n
	   -fconstexpr-cache-depth=n		      -fconstexpr-loop-limit=n
	   -fconstexpr-ops-limit=n		       -fno-elide-constructors
	   -fno-enforce-eh-specs   -fno-gnu-keywords   -fno-implicit-templates
	   -fno-implicit-inline-templates		-fno-implement-inlines
	   -fmodule-header[=kind]	   -fmodule-only	  -fmodules-ts
	   -fmodule-implicit-inline			      -fno-module-lazy
	   -fmodule-mapper=specification	       -fmodule-version-ignore
	   -fms-extensions	-fnew-inheriting-ctors	    -fnew-ttp-matching
	   -fno-nonansi-builtins       -fnothrow-opt	   -fno-operator-names
	   -fno-optional-diags	-fpermissive  -fno-pretty-templates  -fno-rtti
	   -fsized-deallocation			  -ftemplate-backtrace-limit=n
	   -ftemplate-depth=n	 -fno-threadsafe-statics      -fuse-cxa-atexit
	   -fno-weak	       -nostdinc++	   -fvisibility-inlines-hidden
	   -fvisibility-ms-compat			-fext-numeric-literals
	   -flang-info-include-translate[=header]
	   -flang-info-include-translate-not   -flang-info-module-cmi[=module]
	   -stdlib=libstdc++,libc++ -Wabi-tag  -Wcatch-value   -Wcatch-value=n
	   -Wno-class-conversion       -Wclass-memaccess     -Wcomma-subscript
	   -Wconditionally-supported			  -Wno-conversion-null
	   -Wctad-maybe-unsupported			   -Wctor-dtor-privacy
	   -Wno-delete-incomplete -Wdelete-non-virtual-dtor  -Wdeprecated-copy
	   -Wdeprecated-copy-dtor	  -Wno-deprecated-enum-enum-conversion
	   -Wno-deprecated-enum-float-conversion   -Weffc++    -Wno-exceptions
	   -Wextra-semi	  -Wno-inaccessible-base  -Wno-inherited-variadic-ctor
	   -Wno-init-list-lifetime		     -Winvalid-imported-macros
	   -Wno-invalid-offsetof			   -Wno-literal-suffix
	   -Wno-mismatched-new-delete -Wmismatched-tags	-Wmultiple-inheritance
	   -Wnamespaces	      -Wnarrowing      -Wnoexcept      -Wnoexcept-type
	   -Wnon-virtual-dtor	   -Wpessimizing-move	    -Wno-placement-new
	   -Wplacement-new=n	  -Wrange-loop-construct      -Wredundant-move
	   -Wredundant-tags   -Wreorder	   -Wregister	-Wstrict-null-sentinel
	   -Wno-subobject-linkage      -Wtemplates    -Wno-non-template-friend
	   -Wold-style-cast	-Woverloaded-virtual	  -Wno-pmf-conversions
	   -Wsign-promo	     -Wsized-deallocation      -Wsuggest-final-methods
	   -Wsuggest-final-types       -Wsuggest-override	-Wno-terminate
	   -Wuseless-cast	 -Wno-vexing-parse	 -Wvirtual-inheritance
	   -Wno-virtual-move-assign				    -Wvolatile
	   -Wzero-as-null-pointer-constant

       Objective-C and Objective-C++ Language Options
	   -fconstant-string-class=class-name	-fgnu-runtime	-fnext-runtime
	   -fno-nil-receivers	-fobjc-abi-version=n	-fobjc-call-cxx-cdtors
	   -fobjc-direct-dispatch  -fobjc-exceptions -fobjc-gc -fobjc-nilcheck
	   -fobjc-std=objc1				      -fno-local-ivars
	   -fivar-visibility=[public|protected|private|package]
	   -freplace-objc-classes  -fzero-link	-gen-decls  -Wassign-intercept
	   -Wno-property-assign-default	   -Wno-protocol     -Wobjc-root-class
	   -Wselector -Wstrict-selector-match -Wundeclared-selector

       Diagnostic Message Formatting Options
	   -fmessage-length=n			    -fdiagnostics-plain-output
	   -fdiagnostics-show-location=[once|every-line]
	   -fdiagnostics-color=[auto|never|always]
	   -fdiagnostics-urls=[auto|never|always]
	   -fdiagnostics-format=[text|json]	  -fno-diagnostics-show-option
	   -fno-diagnostics-show-caret		  -fno-diagnostics-show-labels
	   -fno-diagnostics-show-line-numbers	     -fno-diagnostics-show-cwe
	   -fdiagnostics-minimum-margin-width=width
	   -fdiagnostics-parseable-fixits	  -fdiagnostics-generate-patch
	   -fdiagnostics-show-template-tree		       -fno-elide-type
	   -fdiagnostics-path-format=[none|separate-events|inline-events]
	   -fdiagnostics-show-path-depths		      -fno-show-column
	   -fdiagnostics-column-unit=[display|byte]
	   -fdiagnostics-column-origin=origin

       Warning Options
	   -fsyntax-only   -fmax-errors=n   -Wpedantic	 -pedantic-errors   -w
	   -Wextra   -Wall   -Wabi=n  -Waddress	 -Wno-address-of-packed-member
	   -Waggregate-return -Walloc-size-larger-than=byte-size  -Walloc-zero
	   -Walloca				-Walloca-larger-than=byte-size
	   -Wno-aggressive-loop-optimizations		    -Warith-conversion
	   -Warray-bounds	    -Warray-bounds=n	       -Wno-attributes
	   -Wattribute-alias=n	 -Wno-attribute-alias	-Wno-attribute-warning
	   -Wbool-compare  -Wbool-operation  -Wno-builtin-declaration-mismatch
	   -Wno-builtin-macro-redefined	   -Wc90-c99-compat   -Wc99-c11-compat
	   -Wc11-c2x-compat   -Wc++-compat    -Wc++11-compat	-Wc++14-compat
	   -Wc++17-compat   -Wc++20-compat  -Wcast-align   -Wcast-align=strict
	   -Wcast-function-type	  -Wcast-qual  -Wchar-subscripts   -Wclobbered
	   -Wcomment	 -Wconversion	   -Wno-coverage-mismatch     -Wno-cpp
	   -Wdangling-else	       -Wdate-time	       -Wno-deprecated
	   -Wno-deprecated-declarations			  -Wno-designated-init
	   -Wdisabled-optimization	       -Wno-discarded-array-qualifiers
	   -Wno-discarded-qualifiers	-Wno-div-by-zero    -Wdouble-promotion
	   -Wduplicated-branches	 -Wduplicated-cond	  -Wempty-body
	   -Wno-endif-labels	 -Wenum-compare	   -Wenum-conversion   -Werror
	   -Werror=*	       -Wexpansion-to-defined		-Wfatal-errors
	   -Wfloat-conversion	   -Wfloat-equal      -Wformat	    -Wformat=2
	   -Wno-format-contains-nul			-Wno-format-extra-args
	   -Wformat-nonliteral	     -Wformat-overflow=n     -Wformat-security
	   -Wformat-signedness	      -Wformat-truncation=n	  -Wformat-y2k
	   -Wframe-address			 -Wframe-larger-than=byte-size
	   -Wno-free-nonheap-object			   -Wno-if-not-aligned
	   -Wno-ignored-attributes			  -Wignored-qualifiers
	   -Wno-incompatible-pointer-types -Wimplicit	-Wimplicit-fallthrough
	   -Wimplicit-fallthrough=n	    -Wno-implicit-function-declaration
	   -Wno-implicit-int   -Winit-self    -Winline	   -Wno-int-conversion
	   -Wint-in-bool-context		      -Wno-int-to-pointer-cast
	   -Wno-invalid-memory-model	 -Winvalid-pch	    -Wjump-misses-init
	   -Wlarger-than=byte-size   -Wlogical-not-parentheses	  -Wlogical-op
	   -Wlong-long	-Wno-lto-type-mismatch	-Wmain	 -Wmaybe-uninitialized
	   -Wmemset-elt-size			      -Wmemset-transposed-args
	   -Wmisleading-indentation   -Wmissing-attributes    -Wmissing-braces
	   -Wmissing-field-initializers		    -Wmissing-format-attribute
	   -Wmissing-include-dirs   -Wmissing-noreturn	  -Wno-missing-profile
	   -Wno-multichar	    -Wmultistatement-macros	     -Wnonnull
	   -Wnonnull-compare		       -Wnormalized=[none|id|nfc|nfkc]
	   -Wnull-dereference	   -Wno-odr	-Wopenmp-simd	 -Wno-overflow
	   -Woverlength-strings	   -Wno-override-init-side-effects    -Wpacked
	   -Wno-packed-bitfield-compat	    -Wpacked-not-aligned      -Wpadded
	   -Wparentheses	-Wno-pedantic-ms-format	       -Wpointer-arith
	   -Wno-pointer-compare	     -Wno-pointer-to-int-cast	  -Wno-pragmas
	   -Wno-prio-ctor-dtor		 -Wredundant-decls	    -Wrestrict
	   -Wno-return-local-addr    -Wreturn-type   -Wno-scalar-storage-order
	   -Wsequence-point    -Wshadow	    -Wshadow=global	-Wshadow=local
	   -Wshadow=compatible-local			      -Wno-shadow-ivar
	   -Wno-shift-count-negative		     -Wno-shift-count-overflow
	   -Wshift-negative-value    -Wno-shift-overflow    -Wshift-overflow=n
	   -Wsign-compare     -Wsign-conversion	    -Wno-sizeof-array-argument
	   -Wsizeof-array-div -Wsizeof-pointer-div  -Wsizeof-pointer-memaccess
	   -Wstack-protector	 -Wstack-usage=byte-size     -Wstrict-aliasing
	   -Wstrict-aliasing=n	    -Wstrict-overflow	   -Wstrict-overflow=n
	   -Wstring-compare    -Wno-stringop-overflow	-Wno-stringop-overread
	   -Wno-stringop-truncation
	   -Wsuggest-attribute=[pure|const|noreturn|format|malloc]    -Wswitch
	   -Wno-switch-bool	      -Wswitch-default		 -Wswitch-enum
	   -Wno-switch-outside-range	-Wno-switch-unreachable	   -Wsync-nand
	   -Wsystem-headers	   -Wtautological-compare	 -Wtrampolines
	   -Wtrigraphs	 -Wtsan	  -Wtype-limits	    -Wundef    -Wuninitialized
	   -Wunknown-pragmas	   -Wunsuffixed-float-constants	      -Wunused
	   -Wunused-but-set-parameter		     -Wunused-but-set-variable
	   -Wunused-const-variable		     -Wunused-const-variable=n
	   -Wunused-function	  -Wunused-label       -Wunused-local-typedefs
	   -Wunused-macros	  -Wunused-parameter	    -Wno-unused-result
	   -Wunused-value  -Wunused-variable  -Wno-varargs   -Wvariadic-macros
	   -Wvector-operation-performance  -Wvla   -Wvla-larger-than=byte-size
	   -Wno-vla-larger-than	   -Wvolatile-register-var     -Wwrite-strings
	   -Wzero-length-bounds

       Static Analyzer Options
	   -fanalyzer	  -fanalyzer-call-summaries    -fanalyzer-checker=name
	   -fno-analyzer-feasibility		       -fanalyzer-fine-grained
	   -fanalyzer-state-merge			-fanalyzer-state-purge
	   -fanalyzer-transitivity		      -fanalyzer-verbose-edges
	   -fanalyzer-verbose-state-changes	    -fanalyzer-verbosity=level
	   -fdump-analyzer  -fdump-analyzer-stderr   -fdump-analyzer-callgraph
	   -fdump-analyzer-exploded-graph	-fdump-analyzer-exploded-nodes
	   -fdump-analyzer-exploded-nodes-2   -fdump-analyzer-exploded-nodes-3
	   -fdump-analyzer-feasibility			  -fdump-analyzer-json
	   -fdump-analyzer-state-purge		    -fdump-analyzer-supergraph
	   -Wno-analyzer-double-fclose		     -Wno-analyzer-double-free
	   -Wno-analyzer-exposure-through-output-file  -Wno-analyzer-file-leak
	   -Wno-analyzer-free-of-non-heap	     -Wno-analyzer-malloc-leak
	   -Wno-analyzer-mismatching-deallocation  -Wno-analyzer-null-argument
	   -Wno-analyzer-null-dereference -Wno-analyzer-possible-null-argument
	   -Wno-analyzer-possible-null-dereference
	   -Wno-analyzer-shift-count-negative
	   -Wno-analyzer-shift-count-overflow
	   -Wno-analyzer-stale-setjmp-buffer -Wno-analyzer-tainted-array-index
	   -Wanalyzer-too-complex
	   -Wno-analyzer-unsafe-call-within-signal-handler
	   -Wno-analyzer-use-after-free
	   -Wno-analyzer-use-of-pointer-in-stale-stack-frame
	   -Wno-analyzer-use-of-uninitialized-value
	   -Wno-analyzer-write-to-const	-Wno-analyzer-write-to-string-literal

       C and Objective-C-only Warning Options
	   -Wbad-function-cast				-Wmissing-declarations
	   -Wmissing-parameter-type   -Wmissing-prototypes    -Wnested-externs
	   -Wold-style-declaration  -Wold-style-definition -Wstrict-prototypes
	   -Wtraditional			      -Wtraditional-conversion
	   -Wdeclaration-after-statement  -Wpointer-sign

       Debugging Options
	   -g  -glevel	-gdwarf	 -gdwarf-version -ggdb	 -grecord-gcc-switches
	   -gno-record-gcc-switches    -gstabs	   -gstabs+	-gstrict-dwarf
	   -gno-strict-dwarf	   -gas-loc-support	   -gno-as-loc-support
	   -gas-locview-support	     -gno-as-locview-support	 -gcolumn-info
	   -gno-column-info    -gdwarf32    -gdwarf64	 -gstatement-frontiers
	   -gno-statement-frontiers		     -gvariable-location-views
	   -gno-variable-location-views	       -ginternal-reset-location-views
	   -gno-internal-reset-location-views		       -ginline-points
	   -gno-inline-points	 -gvms	   -gxcoff     -gxcoff+	    -gz[=type]
	   -gsplit-dwarf	   -gdescribe-dies	    -gno-describe-dies
	   -fdebug-prefix-map=old=new			 -fdebug-types-section
	   -fno-eliminate-unused-debug-types	  -femit-struct-debug-baseonly
	   -femit-struct-debug-reduced	   -femit-struct-debug-detailed[=spec-
	   list]			   -fno-eliminate-unused-debug-symbols
	   -femit-class-debug-always		      -fno-merge-debug-strings
	   -fno-dwarf2-cfi-asm -fvar-tracking  -fvar-tracking-assignments

       Optimization Options
	   -faggressive-loop-optimizations -falign-functions[=n[:m:[n2[:m2]]]]
	   -falign-jumps[=n[:m:[n2[:m2]]]]    -falign-labels[=n[:m:[n2[:m2]]]]
	   -falign-loops[=n[:m:[n2[:m2]]]]		   -fno-allocation-dce
	   -fallow-store-data-races	-fassociative-math	-fauto-profile
	   -fauto-profile[=path]    -fauto-inc-dec	-fbranch-probabilities
	   -fcaller-saves     -fcombine-stack-adjustments     -fconserve-stack
	   -fcompare-elim	    -fcprop-registers		-fcrossjumping
	   -fcse-follow-jumps	    -fcse-skip-blocks	    -fcx-fortran-rules
	   -fcx-limited-range	-fdata-sections	    -fdce     -fdelayed-branch
	   -fdelete-null-pointer-checks				-fdevirtualize
	   -fdevirtualize-speculatively	   -fdevirtualize-at-ltrans	 -fdse
	   -fearly-inlining	    -fipa-sra	     -fexpensive-optimizations
	   -ffat-lto-objects  -ffast-math   -ffinite-math-only	 -ffloat-store
	   -fexcess-precision=style	-ffinite-loops	   -fforward-propagate
	   -ffp-contract=style		  -ffunction-sections		-fgcse
	   -fgcse-after-reload	  -fgcse-las   -fgcse-lm   -fgraphite-identity
	   -fgcse-sm  -fhoist-adjacent-loads  -fif-conversion -fif-conversion2
	   -findirect-inlining				    -finline-functions
	   -finline-functions-called-once		      -finline-limit=n
	   -finline-small-functions  -fipa-modref   -fipa-cp	-fipa-cp-clone
	   -fipa-bit-cp	 -fipa-vrp  -fipa-pta  -fipa-profile  -fipa-pure-const
	   -fipa-reference   -fipa-reference-addressable -fipa-stack-alignment
	   -fipa-icf	  -fira-algorithm=algorithm	 -flive-patching=level
	   -fira-region=region	   -fira-hoist-pressure	   -fira-loop-pressure
	   -fno-ira-share-save-slots		    -fno-ira-share-spill-slots
	   -fisolate-erroneous-paths-dereference
	   -fisolate-erroneous-paths-attribute			      -fivopts
	   -fkeep-inline-functions		       -fkeep-static-functions
	   -fkeep-static-consts			    -flimit-function-alignment
	   -flive-range-shrinkage	-floop-block	    -floop-interchange
	   -floop-strip-mine	-floop-unroll-and-jam	  -floop-nest-optimize
	   -floop-parallelize-all  -flra-remat	-flto  -flto-compression-level
	   -flto-partition=alg	   -fmerge-all-constants     -fmerge-constants
	   -fmodulo-sched			 -fmodulo-sched-allow-regmoves
	   -fmove-loop-invariants     -fno-branch-count-reg	-fno-defer-pop
	   -fno-fp-int-builtin-inexact			     -fno-function-cse
	   -fno-guess-branch-probability      -fno-inline      -fno-math-errno
	   -fno-peephole	-fno-peephole2	      -fno-printf-return-value
	   -fno-sched-interblock      -fno-sched-spec	     -fno-signed-zeros
	   -fno-toplevel-reorder			    -fno-trapping-math
	   -fno-zero-initialized-in-bss			  -fomit-frame-pointer
	   -foptimize-sibling-calls	 -fpartial-inlining	  -fpeel-loops
	   -fpredictive-commoning -fprefetch-loop-arrays  -fprofile-correction
	   -fprofile-use      -fprofile-use=path    -fprofile-partial-training
	   -fprofile-values   -fprofile-reorder-functions    -freciprocal-math
	   -free	      -frename-registers	      -freorder-blocks
	   -freorder-blocks-algorithm=algorithm	-freorder-blocks-and-partition
	   -freorder-functions				-frerun-cse-after-loop
	   -freschedule-modulo-scheduled-loops		       -frounding-math
	   -fsave-optimization-record		      -fsched2-use-superblocks
	   -fsched-pressure   -fsched-spec-load	   -fsched-spec-load-dangerous
	   -fsched-stalled-insns-dep[=n]	     -fsched-stalled-insns[=n]
	   -fsched-group-heuristic	       -fsched-critical-path-heuristic
	   -fsched-spec-insn-heuristic			-fsched-rank-heuristic
	   -fsched-last-insn-heuristic		   -fsched-dep-count-heuristic
	   -fschedule-fusion	    -fschedule-insns	     -fschedule-insns2
	   -fsection-anchors  -fselective-scheduling   -fselective-scheduling2
	   -fsel-sched-pipelining	    -fsel-sched-pipelining-outer-loops
	   -fsemantic-interposition    -fshrink-wrap	-fshrink-wrap-separate
	   -fsignaling-nans			   -fsingle-precision-constant
	   -fsplit-ivs-in-unroller	    -fsplit-loops	 -fsplit-paths
	   -fsplit-wide-types	  -fsplit-wide-types-early	-fssa-backprop
	   -fssa-phiopt	  -fstdarg-opt	  -fstore-merging    -fstrict-aliasing
	   -fthread-jumps   -ftracer   -ftree-bit-ccp  -ftree-builtin-call-dce
	   -ftree-ccp	  -ftree-ch   -ftree-coalesce-vars    -ftree-copy-prop
	   -ftree-dce	 -ftree-dominator-opts	 -ftree-dse    -ftree-forwprop
	   -ftree-fre	-fcode-hoisting	-ftree-loop-if-convert	-ftree-loop-im
	   -ftree-phiprop			      -ftree-loop-distribution
	   -ftree-loop-distribute-patterns		   -ftree-loop-ivcanon
	   -ftree-loop-linear	 -ftree-loop-optimize	 -ftree-loop-vectorize
	   -ftree-parallelize-loops=n	    -ftree-pre	    -ftree-partial-pre
	   -ftree-pta	 -ftree-reassoc	    -ftree-scev-cprop	   -ftree-sink
	   -ftree-slsr	-ftree-sra -ftree-switch-conversion  -ftree-tail-merge
	   -ftree-ter	-ftree-vectorize   -ftree-vrp  -funconstrained-commons
	   -funit-at-a-time	    -funroll-all-loops		-funroll-loops
	   -funsafe-math-optimizations	       -funswitch-loops	      -fipa-ra
	   -fvariable-expansion-in-unroller   -fvect-cost-model	  -fvpt	 -fweb
	   -fwhole-program   -fwpa   -fuse-linker-plugin -fzero-call-used-regs
	   --param name=value -O  -O0  -O1  -O2	 -O3  -Os  -Ofast  -Og

       Program Instrumentation Options
	   -p	  -pg	   -fprofile-arcs      --coverage      -ftest-coverage
	   -fprofile-abs-path	   -fprofile-dir=path	    -fprofile-generate
	   -fprofile-generate=path			-fprofile-info-section
	   -fprofile-info-section=name			   -fprofile-note=path
	   -fprofile-prefix-path=path		       -fprofile-update=method
	   -fprofile-filter-files=regex		 -fprofile-exclude-files=regex
	   -fprofile-reproducible=[multithreaded|parallel-runs|serial]
	   -fsanitize=style    -fsanitize-recover     -fsanitize-recover=style
	   -fasan-shadow-offset=number		 -fsanitize-sections=s1,s2,...
	   -fsanitize-undefined-trap-on-error			-fbounds-check
	   -fcf-protection=[full|branch|return|none|check]   -fstack-protector
	   -fstack-protector-all		      -fstack-protector-strong
	   -fstack-protector-explicit				 -fstack-check
	   -fstack-limit-register=reg		      -fstack-limit-symbol=sym
	   -fno-stack-limit   -fsplit-stack -fvtable-verify=[std|preinit|none]
	   -fvtv-counts		  -fvtv-debug		-finstrument-functions
	   -finstrument-functions-exclude-function-list=sym,sym,...
	   -finstrument-functions-exclude-file-list=file,file,...

       Preprocessor Options
	   -Aquestion=answer  -A-question[=answer] -C  -CC  -Dmacro[=defn] -dD
	   -dI	   -dM	   -dN	    -dU	    -fdebug-cpp	     -fdirectives-only
	   -fdollars-in-identifiers			-fexec-charset=charset
	   -fextended-identifiers		       -finput-charset=charset
	   -flarge-source-files			    -fmacro-prefix-map=old=new
	   -fmax-include-depth=depth -fno-canonical-system-headers  -fpch-deps
	   -fpch-preprocess	     -fpreprocessed	       -ftabstop=width
	   -ftrack-macro-expansion		   -fwide-exec-charset=charset
	   -fworking-directory -H  -imacros file  -include file	-M   -MD   -MF
	   -MG	 -MM   -MMD  -MP  -MQ  -MT -Mno-modules	-no-integrated-cpp  -P
	   -pthread  -remap -traditional  -traditional-cpp  -trigraphs -Umacro
	   -undef -Wp,option  -Xpreprocessor option

       Assembler Options
	   -Wa,option  -Xassembler option

       Linker Options
	   object-file-name	-fuse-ld=linker	    -llibrary	 -nostartfiles
	   -nodefaultlibs   -nolibc   -nostdlib	 -e  entry  --entry=entry -pie
	   -pthread  -r	 -rdynamic -s	-static	  -static-pie	-static-libgcc
	   -static-libstdc++ -static-libasan  -static-libtsan  -static-liblsan
	   -static-libubsan   -shared	-shared-libgcc	 -symbolic  -T	script
	   -Wl,option  -Xlinker	option -u symbol  -z keyword

       Directory Options
	   -Bprefix  -Idir  -I-	-idirafter dir -imacros	file   -imultilib  dir
	   -iplugindir=dir  -iprefix file -iquote dir  -isysroot dir  -isystem
	   dir	   -iwithprefix	    dir	    -iwithprefixbefore	  dir	 -Ldir
	   -no-canonical-prefixes  --no-sysroot-suffix -nostdinc   -nostdinc++
	   --sysroot=dir

       Code Generation Options
	   -fcall-saved-reg	-fcall-used-reg	   -ffixed-reg	  -fexceptions
	   -fnon-call-exceptions   -fdelete-dead-exceptions    -funwind-tables
	   -fasynchronous-unwind-tables			       -fno-gnu-unique
	   -finhibit-size-directive  -fcommon  -fno-ident  -fpcc-struct-return
	   -fpic     -fPIC     -fpie	 -fPIE	   -fno-plt   -fno-jump-tables
	   -fno-bit-tests      -frecord-gcc-switches	   -freg-struct-return
	   -fshort-enums    -fshort-wchar   -fverbose-asm    -fpack-struct[=n]
	   -fleading-underscore	  -ftls-model=model  -fstack-reuse=reuse_level
	   -ftrampolines		    -ftrapv		       -fwrapv
	   -fvisibility=[default|internal|hidden|protected]
	   -fstrict-volatile-bitfields	-fsync-libcalls

       Developer Options
	   -dletters  -dumpspecs  -dumpmachine	-dumpversion  -dumpfullversion
	   -fcallgraph-info[=su,da]  -fchecking	  -fchecking=n	-fdbg-cnt-list
	   -fdbg-cnt=counter-value-list		       -fdisable-ipa-pass_name
	   -fdisable-rtl-pass_name	    -fdisable-rtl-pass-name=range-list
	   -fdisable-tree-pass_name	   -fdisable-tree-pass-name=range-list
	   -fdump-debug	  -fdump-earlydebug  -fdump-noaddr   -fdump-unnumbered
	   -fdump-unnumbered-links  -fdump-final-insns[=file]	-fdump-ipa-all
	   -fdump-ipa-cgraph	      -fdump-ipa-inline	       -fdump-lang-all
	   -fdump-lang-switch			    -fdump-lang-switch-options
	   -fdump-lang-switch-options=filename	-fdump-passes  -fdump-rtl-pass
	   -fdump-rtl-pass=filename	-fdump-statistics      -fdump-tree-all
	   -fdump-tree-switch			    -fdump-tree-switch-options
	   -fdump-tree-switch-options=filename		-fcompare-debug[=opts]
	   -fcompare-debug-second -fenable-kind-pass -fenable-kind-pass=range-
	   list	      -fira-verbose=n	   -flto-report	      -flto-report-wpa
	   -fmem-report-wpa	    -fmem-report	  -fpre-ipa-mem-report
	   -fpost-ipa-mem-report     -fopt-info	     -fopt-info-options[=file]
	   -fprofile-report	 -frandom-seed=string	     -fsched-verbose=n
	   -fsel-sched-verbose				  -fsel-sched-dump-cfg
	   -fsel-sched-pipelining-verbose	 -fstats	 -fstack-usage
	   -ftime-report				 -ftime-report-details
	   -fvar-tracking-assignments-toggle			      -gtoggle
	   -print-file-name=library		       -print-libgcc-file-name
	   -print-multi-directory  -print-multi-lib  -print-multi-os-directory
	   -print-prog-name=program   -print-search-dirs   -Q	-print-sysroot
	   -print-sysroot-headers-suffix      -save-temps      -save-temps=cwd
	   -save-temps=obj  -time[=file]

       Machine-Dependent Options
	   AArch64   Options   -mabi=name     -mbig-endian     -mlittle-endian
	   -mgeneral-regs-only	-mcmodel=tiny	-mcmodel=small	-mcmodel=large
	   -mstrict-align      -mno-strict-align     -momit-leaf-frame-pointer
	   -mtls-dialect=desc	  -mtls-dialect=traditional    -mtls-size=size
	   -mfix-cortex-a53-835769		       -mfix-cortex-a53-843419
	   -mlow-precision-recip-sqrt			  -mlow-precision-sqrt
	   -mlow-precision-div			   -mpc-relative-literal-loads
	   -msign-return-address=scope	-mbranch-protection=none|standard|pac-
	   ret[+leaf  +b-key]|bti  -mharden-sls=opts  -march=name   -mcpu=name
	   -mtune=name		-moverride=string	   -mverbose-cost-dump
	   -mstack-protector-guard=guard    -mstack-protector-guard-reg=sysreg
	   -mstack-protector-guard-offset=offset	   -mtrack-speculation
	   -moutline-atomics

	   Adapteva Epiphany Options -mhalf-reg-file  -mprefer-short-insn-regs
	   -mbranch-cost=num  -mcmove  -mnops=num   -msoft-cmpsf  -msplit-lohi
	   -mpost-inc	 -mpost-modify	  -mstack-offset=num   -mround-nearest
	   -mlong-calls	     -mshort-calls	 -msmall16	-mfp-mode=mode
	   -mvect-double	-max-vect-align=num	 -msplit-vecmove-early
	   -m1reg-reg

	   AMD GCN Options -march=gpu -mtune=gpu -mstack-size=bytes

	   ARC	Options	  -mbarrel-shifter    -mjli-always   -mcpu=cpu	  -mA6
	   -mARC600    -mA7    -mARC700	 -mdpfp	  -mdpfp-compact   -mdpfp-fast
	   -mno-dpfp-lrsr -mea	-mno-mpy  -mmul32x16  -mmul64  -matomic	-mnorm
	   -mspfp  -mspfp-compact  -mspfp-fast	-msimd	 -msoft-float	-mswap
	   -mcrc   -mdsp-packa	 -mdvbf	  -mlock   -mmac-d16  -mmac-24	-mrtsc
	   -mswape -mtelephony	-mxy   -misize	 -mannotate-align   -marclinux
	   -marclinux_prof	-mlong-calls	   -mmedium-calls      -msdata
	   -mirq-ctrl-saved  -mrgf-banked-regs	 -mlpc-width=width    -G   num
	   -mvolatile-cache   -mtp-regno=regno -malign-call  -mauto-modify-reg
	   -mbbit-peephole   -mno-brcc	-mcase-vector-pcrel   -mcompact-casesi
	   -mno-cond-exec   -mearly-cbranchsi  -mexpand-adddi  -mindexed-loads
	   -mlra   -mlra-priority-none	-mlra-priority-compact	mlra-priority-
	   noncompact	 -mmillicode  -mmixed-code   -mq-class	 -mRcq	 -mRcw
	   -msize-level=level -mtune=cpu  -mmultcost=num  -mcode-density-frame
	   -munalign-prob-threshold=probability	 -mmpy-option=multo  -mdiv-rem
	   -mcode-density  -mll64  -mfpu=fpu  -mrf16  -mbranch-index

	   ARM	   Options     -mapcs-frame	 -mno-apcs-frame    -mabi=name
	   -mapcs-stack-check	   -mno-apcs-stack-check      -mapcs-reentrant
	   -mno-apcs-reentrant	      -mgeneral-regs-only	-msched-prolog
	   -mno-sched-prolog  -mlittle-endian	-mbig-endian   -mbe8	-mbe32
	   -mfloat-abi=name	   -mfp16-format=name	     -mthumb-interwork
	   -mno-thumb-interwork	   -mcpu=name	   -march=name	    -mfpu=name
	   -mtune=name	     -mprint-tune-info	   -mstructure-size-boundary=n
	   -mabort-on-noreturn -mlong-calls  -mno-long-calls -msingle-pic-base
	   -mno-single-pic-base	    -mpic-register=reg	   -mnop-fun-dllimport
	   -mpoke-function-name	  -mthumb   -marm   -mflip-thumb  -mtpcs-frame
	   -mtpcs-leaf-frame			   -mcaller-super-interworking
	   -mcallee-super-interworking	   -mtp=name	 -mtls-dialect=dialect
	   -mword-relocations	  -mfix-cortex-m3-ldrd	    -munaligned-access
	   -mneon-for-64bits	   -mslow-flash-data	  -masm-syntax-unified
	   -mrestrict-it      -mverbose-cost-dump      -mpure-code	-mcmse
	   -mfix-cmse-cve-2021-35465 -mfdpic

	   AVR	   Options     -mmcu=mcu      -mabsdata	     -maccumulate-args
	   -mbranch-cost=cost  -mcall-prologues	  -mgas-isr-prologues	-mint8
	   -mdouble=bits  -mlong-double=bits  -mn_flash=size   -mno-interrupts
	   -mmain-is-OS_task	-mrelax	   -mrmw    -mstrict-X	  -mtiny-stack
	   -mfract-convert-truncate	    -mshort-calls	  -nodevicelib
	   -nodevicespecs -Waddr-space-convert	-Wmisspelled-isr

	   Blackfin	   Options	  -mcpu=cpu[-sirevision]	 -msim
	   -momit-leaf-frame-pointer		  -mno-omit-leaf-frame-pointer
	   -mspecld-anomaly	   -mno-specld-anomaly	       -mcsync-anomaly
	   -mno-csync-anomaly	 -mlow-64k     -mno-low64k    -mstack-check-l1
	   -mid-shared-library	-mno-id-shared-library	 -mshared-library-id=n
	   -mleaf-id-shared-library    -mno-leaf-id-shared-library  -msep-data
	   -mno-sep-data      -mlong-calls	-mno-long-calls	     -mfast-fp
	   -minline-plt	 -mmulticore  -mcorea  -mcoreb	-msdram	-micplb

	   C6X	 Options   -mbig-endian	   -mlittle-endian   -march=cpu	 -msim
	   -msdata=sdata-type

	   CRIS	Options	-mcpu=cpu  -march=cpu  -mtune=cpu  -mmax-stack-frame=n
	   -metrax4    -metrax100    -mpdebug	 -mcc-init   -mno-side-effects
	   -mstack-align   -mdata-align	  -mconst-align	  -m32-bit    -m16-bit
	   -m8-bit    -mno-prologue-epilogue   -melf	-maout	  -sim	 -sim2
	   -mmul-bug-workaround	 -mno-mul-bug-workaround

	   CR16	Options	-mmac -mcr16cplus  -mcr16c -msim   -mint32   -mbit-ops
	   -mdata-model=model

	   C-SKY    Options    -march=arch     -mcpu=cpu   -mbig-endian	   -EB
	   -mlittle-endian    -EL   -mhard-float    -msoft-float     -mfpu=fpu
	   -mdouble-float   -mfdivdu  -mfloat-abi=name	-melrw	-mistack  -mmp
	   -mcp	 -mcache  -msecurity   -mtrust	-mdsp	-medsp	 -mvdsp	 -mdiv
	   -msmart    -mhigh-registers	 -manchor  -mpushpop   -mmultiple-stld
	   -mconstpool	  -mstack-size	  -mccrt   -mbranch-cost=n    -mcse-cc
	   -msched-prolog -msim

	   Darwin      Options	   -all_load	  -allowable_client	 -arch
	   -arch_errors_fatal	  -arch_only	   -bind_at_load       -bundle
	   -bundle_loader	  -client_name		-compatibility_version
	   -current_version    -dead_strip    -dependency-file	   -dylib_file
	   -dylinker_install_name	      -dynamic		   -dynamiclib
	   -exported_symbols_list	   -filelist	       -flat_namespace
	   -force_cpusubtype_ALL			 -force_flat_namespace
	   -headerpad_max_install_names	  -iframework	 -image_base	 -init
	   -install_name	   -keep_private_externs	 -multi_module
	   -multiply_defined	    -multiply_defined_unused	   -noall_load
	   -no_dead_strip_inits_and_terms    -nofixprebinding	  -nomultidefs
	   -noprebind	    -noseglinkedit	-pagezero_size	      -prebind
	   -prebind_all_twolevel_modules   -private_bundle   -read_only_relocs
	   -sectalign  -sectobjectsymbols   -whyload   -seg1addr   -sectcreate
	   -sectobjectsymbols	 -sectorder   -segaddr	  -segs_read_only_addr
	   -segs_read_write_addr   -seg_addr_table    -seg_addr_table_filename
	   -seglinkedit	 -segprot  -segs_read_only_addr	 -segs_read_write_addr
	   -single_module	-static	      -sub_library	 -sub_umbrella
	   -twolevel_namespace	-umbrella  -undefined -unexported_symbols_list
	   -weak_reference_mismatches	-whatsloaded	-F    -gused	-gfull
	   -mmacosx-version-min=version	-mkernel  -mone-byte-bool

	   DEC	  Alpha	   Options    -mno-fp-regs     -msoft-float	-mieee
	   -mieee-with-inexact	     -mieee-conformant	   -mfp-trap-mode=mode
	   -mfp-rounding-mode=mode  -mtrap-precision=mode    -mbuild-constants
	   -mcpu=cpu-type    -mtune=cpu-type   -mbwx	-mmax	 -mfix	 -mcix
	   -mfloat-vax	   -mfloat-ieee	   -mexplicit-relocs	  -msmall-data
	   -mlarge-data	-msmall-text  -mlarge-text -mmemory-latency=time

	   eBPF	   Options   -mbig-endian   -mlittle-endian   -mkernel=version
	   -mframe-limit=bytes -mxbpf

	   FR30	Options	-msmall-model  -mno-lsim

	   FT32	Options	-msim  -mlra  -mnodiv  -mft32b	-mcompress  -mnopm

	   FRV Options -mgpr-32	  -mgpr-64   -mfpr-32	-mfpr-64  -mhard-float
	   -msoft-float	 -malloc-cc   -mfixed-cc  -mdword  -mno-dword -mdouble
	   -mno-double	-mmedia	  -mno-media   -mmuladd	  -mno-muladd  -mfdpic
	   -minline-plt	    -mgprel-ro	   -multilib-library-pic   -mlinked-fp
	   -mlong-calls	 -malign-labels	-mlibrary-pic  -macc-4	-macc-8	-mpack
	   -mno-pack	   -mno-eflags	     -mcond-move	-mno-cond-move
	   -moptimize-membar	  -mno-optimize-membar	   -mscc      -mno-scc
	   -mcond-exec	  -mno-cond-exec    -mvliw-branch     -mno-vliw-branch
	   -mmulti-cond-exec	  -mno-multi-cond-exec	    -mnested-cond-exec
	   -mno-nested-cond-exec  -mtomcat-stats -mTLS	-mtls -mcpu=cpu

	   GNU/Linux Options -mglibc  -muclibc	 -mmusl	  -mbionic   -mandroid
	   -tno-android-cc  -tno-android-ld

	   H8/300  Options  -mrelax   -mh   -ms	 -mn  -mexr  -mno-exr  -mint32
	   -malign-300

	   HPPA	    Options	 -march=architecture-type      -mcaller-copies
	   -mdisable-fpregs   -mdisable-indexing  -mfast-indirect-calls	 -mgas
	   -mgnu-ld    -mhp-ld	-mfixed-range=register-range   -mjump-in-delay
	   -mlinker-opt	  -mlong-calls	-mlong-load-store  -mno-disable-fpregs
	   -mno-disable-indexing       -mno-fast-indirect-calls	      -mno-gas
	   -mno-jump-in-delay	  -mno-long-load-store	 -mno-portable-runtime
	   -mno-soft-float   -mno-space-regs	-msoft-float	 -mpa-risc-1-0
	   -mpa-risc-1-1   -mpa-risc-2-0   -mportable-runtime  -mschedule=cpu-
	   type	  -mspace-regs	 -msio	 -mwsio	  -munix=unix-std    -nolibdld
	   -static  -threads

	   IA-64  Options  -mbig-endian	  -mlittle-endian   -mgnu-as  -mgnu-ld
	   -mno-pic -mvolatile-asm-stop	 -mregister-names  -msdata  -mno-sdata
	   -mconstant-gp		-mauto-pic		  -mfused-madd
	   -minline-float-divide-min-latency
	   -minline-float-divide-max-throughput	      -mno-inline-float-divide
	   -minline-int-divide-min-latency  -minline-int-divide-max-throughput
	   -mno-inline-int-divide		     -minline-sqrt-min-latency
	   -minline-sqrt-max-throughput	    -mno-inline-sqrt	  -mdwarf2-asm
	   -mearly-stop-bits -mfixed-range=register-range  -mtls-size=tls-size
	   -mtune=cpu-type	 -milp32       -mlp64	  -msched-br-data-spec
	   -msched-ar-data-spec	 -msched-control-spec  -msched-br-in-data-spec
	   -msched-ar-in-data-spec   -msched-in-control-spec  -msched-spec-ldc
	   -msched-spec-control-ldc	    -msched-prefer-non-data-spec-insns
	   -msched-prefer-non-control-spec-insns
	   -msched-stop-bits-after-every-cycle
	   -msched-count-spec-in-critical-path
	   -msel-sched-dont-check-control-spec	 -msched-fp-mem-deps-zero-cost
	   -msched-max-memory-insns-hard-limit	 -msched-max-memory-insns=max-
	   insns

	   LM32	     Options	  -mbarrel-shift-enabled      -mdivide-enabled
	   -mmultiply-enabled -msign-extend-enabled  -muser-enabled

	   M32R/D  Options  -m32r2   -m32rx    -m32r   -mdebug	 -malign-loops
	   -mno-align-loops	 -missue-rate=number	  -mbranch-cost=number
	   -mmodel=code-size-model-type	  -msdata=sdata-type   -mno-flush-func
	   -mflush-func=name -mno-flush-trap  -mflush-trap=number -G num

	   M32C	Options	-mcpu=cpu  -msim  -memregs=number

	   M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000  -m68020
	   -m68020-40	-m68020-60   -m68030  -m68040 -m68060  -mcpu32	-m5200
	   -m5206e  -m528x  -m5307  -m5407 -mcfv4e  -mbitfield	 -mno-bitfield
	   -mc68000   -mc68020	-mnobitfield  -mrtd  -mno-rtd  -mdiv  -mno-div
	   -mshort -mno-short  -mhard-float   -m68881	-msoft-float   -mpcrel
	   -malign-int	     -mstrict-align	 -msep-data	 -mno-sep-data
	   -mshared-library-id=n  -mid-shared-library	-mno-id-shared-library
	   -mxgot  -mno-xgot  -mlong-jump-table-offsets

	   MCore    Options    -mhardlit     -mno-hardlit    -mdiv    -mno-div
	   -mrelax-immediates	  -mno-relax-immediates	      -mwide-bitfields
	   -mno-wide-bitfields	   -m4byte-functions	  -mno-4byte-functions
	   -mcallgraph-data -mno-callgraph-data	 -mslow-bytes  -mno-slow-bytes
	   -mno-lsim	-mlittle-endian	    -mbig-endian      -m210	 -m340
	   -mstack-increment

	   MeP	Options	 -mabsdiff  -mall-opts	-maverage  -mbased=n  -mbitops
	   -mc=n  -mclip  -mconfig=name	 -mcop	-mcop32	 -mcop64  -mivc2  -mdc
	   -mdiv   -meb	  -mel	 -mio-volatile	 -ml   -mleadz	 -mm  -mminmax
	   -mmult   -mno-opts	-mrepeat    -ms	   -msatur    -msdram	 -msim
	   -msimnovec  -mtf -mtiny=n

	   MicroBlaze	Options	 -msoft-float	-mhard-float   -msmall-divides
	   -mcpu=cpu -mmemcpy  -mxl-soft-mul  -mxl-soft-div  -mxl-barrel-shift
	   -mxl-pattern-compare	 -mxl-stack-check  -mxl-gp-opt	 -mno-clearbss
	   -mxl-multiply-high	     -mxl-float-convert	       -mxl-float-sqrt
	   -mbig-endian	  -mlittle-endian   -mxl-reorder   -mxl-mode-app-model
	   -mpic-data-is-text-relative

	   MIPS	 Options  -EL	-EB   -march=arch   -mtune=arch	-mips1	-mips2
	   -mips3  -mips4  -mips32  -mips32r2  -mips32r3  -mips32r5  -mips32r6
	   -mips64    -mips64r2	   -mips64r3	-mips64r5   -mips64r6  -mips16
	   -mno-mips16		 -mflip-mips16		-minterlink-compressed
	   -mno-interlink-compressed -minterlink-mips16	 -mno-interlink-mips16
	   -mabi=abi   -mabicalls   -mno-abicalls -mshared  -mno-shared	 -mplt
	   -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64  -mfp32  -mfpxx	-mfp64
	   -mhard-float	      -msoft-float	-mno-float	-msingle-float
	   -mdouble-float     -modd-spreg	-mno-odd-spreg	    -mabs=mode
	   -mnan=encoding   -mdsp    -mno-dsp	 -mdspr2    -mno-dspr2	 -mmcu
	   -mmno-mcu -meva  -mno-eva -mvirt  -mno-virt -mxpa   -mno-xpa	 -mcrc
	   -mno-crc   -mginv	-mno-ginv  -mmicromips	 -mno-micromips	 -mmsa
	   -mno-msa    -mloongson-mmi	  -mno-loongson-mmi	-mloongson-ext
	   -mno-loongson-ext  -mloongson-ext2	-mno-loongson-ext2  -mfpu=fpu-
	   type	      -msmartmips	 -mno-smartmips	       -mpaired-single
	   -mno-paired-single	-mdmx	-mno-mdmx  -mips3d   -mno-mips3d  -mmt
	   -mno-mt  -mllsc  -mno-llsc -mlong64	-mlong32  -msym32   -mno-sym32
	   -Gnum       -mlocal-sdata	   -mno-local-sdata	-mextern-sdata
	   -mno-extern-sdata	  -mgpopt	-mno-gopt      -membedded-data
	   -mno-embedded-data			      -muninit-const-in-rodata
	   -mno-uninit-const-in-rodata		       -mcode-readable=setting
	   -msplit-addresses	   -mno-split-addresses	     -mexplicit-relocs
	   -mno-explicit-relocs				 -mcheck-zero-division
	   -mno-check-zero-division	  -mdivide-traps       -mdivide-breaks
	   -mload-store-pairs	-mno-load-store-pairs  -mmemcpy	   -mno-memcpy
	   -mlong-calls	  -mno-long-calls -mmad	 -mno-mad  -mimadd  -mno-imadd
	   -mfused-madd	  -mno-fused-madd   -nocpp   -mfix-24k	  -mno-fix-24k
	   -mfix-r4000	    -mno-fix-r4000	-mfix-r4400	-mno-fix-r4400
	   -mfix-r5900	   -mno-fix-r5900    -mfix-r10000      -mno-fix-r10000
	   -mfix-rm7000	    -mno-fix-rm7000    -mfix-vr4120    -mno-fix-vr4120
	   -mfix-vr4130	     -mno-fix-vr4130	  -mfix-sb1	  -mno-fix-sb1
	   -mflush-func=func	      -mno-flush-func	     -mbranch-cost=num
	   -mbranch-likely     -mno-branch-likely    -mcompact-branches=policy
	   -mfp-exceptions	     -mno-fp-exceptions		-mvr4130-align
	   -mno-vr4130-align  -msynci  -mno-synci -mlxc1-sxc1	-mno-lxc1-sxc1
	   -mmadd4     -mno-madd4    -mrelax-pic-calls	  -mno-relax-pic-calls
	   -mmcount-ra-address -mframe-header-opt  -mno-frame-header-opt

	   MMIX	Options	 -mlibfuncs   -mno-libfuncs   -mepsilon	  -mno-epsilon
	   -mabi=gnu	   -mabi=mmixware	-mzero-extend	    -mknuthdiv
	   -mtoplevel-symbols  -melf   -mbranch-predict	   -mno-branch-predict
	   -mbase-addresses	    -mno-base-addresses		 -msingle-exit
	   -mno-single-exit

	   MN10300  Options  -mmult-bug	   -mno-mult-bug   -mno-am33	-mam33
	   -mam33-2   -mam34  -mtune=cpu-type -mreturn-pointer-on-d0 -mno-crt0
	   -mrelax  -mliw  -msetlb

	   Moxie Options -meb  -mel  -mmul.x  -mno-crt0

	   MSP430 Options -msim	 -masm-hex  -mmcu=  -mcpu=   -mlarge   -msmall
	   -mrelax -mwarn-mcu -mcode-region=  -mdata-region= -msilicon-errata=
	   -msilicon-errata-warn=     -mhwmult=	     -minrt	 -mtiny-printf
	   -mmax-inline-shift=

	   NDS32   Options   -mbig-endian    -mlittle-endian	-mreduced-regs
	   -mfull-regs -mcmov  -mno-cmov -mext-perf  -mno-ext-perf -mext-perf2
	   -mno-ext-perf2  -mext-string	 -mno-ext-string -mv3push  -mno-v3push
	   -m16bit   -mno-16bit	 -misr-vector-size=num	-mcache-block-size=num
	   -march=arch -mcmodel=code-model -mctor-dtor	-mrelax

	   Nios	  II  Options  -G  num	 -mgpopt=option	  -mgpopt   -mno-gpopt
	   -mgprel-sec=regexp  -mr0rel-sec=regexp -mel	-meb -mno-bypass-cache
	   -mbypass-cache	 -mno-cache-volatile	      -mcache-volatile
	   -mno-fast-sw-div   -mfast-sw-div  -mhw-mul	-mno-hw-mul  -mhw-mulx
	   -mno-hw-mulx	      -mno-hw-div	-mhw-div       -mcustom-insn=N
	   -mno-custom-insn	 -mcustom-fpu-cfg=name	   -mhal      -msmallc
	   -msys-crt0=name  -msys-lib=name -march=arch	-mbmx  -mno-bmx	 -mcdx
	   -mno-cdx

	   Nvidia PTX Options -m64  -mmainkernel  -moptimize

	   OpenRISC Options  -mboard=name   -mnewlib   -mhard-mul   -mhard-div
	   -msoft-mul	-msoft-div  -msoft-float  -mhard-float	-mdouble-float
	   -munordered-float -mcmov  -mror  -mrori  -msext  -msfimm  -mshftimm

	   PDP-11 Options -mfpu	 -msoft-float	-mac0	-mno-ac0   -m40	  -m45
	   -m10	 -mint32   -mno-int16  -mint16	-mno-int32 -msplit  -munix-asm
	   -mdec-asm  -mgnu-asm	 -mlra

	   picoChip	  Options	-mae=ae_type	    -mvliw-lookahead=N
	   -msymbol-as-address	-mno-inefficient-warnings

	   PowerPC Options See RS/6000 and PowerPC Options.

	   PRU Options -mmcu=mcu  -minrt  -mno-relax  -mloop -mabi=variant

	   RISC-V    Options   -mbranch-cost=N-instruction   -mplt    -mno-plt
	   -mabi=ABI-string  -mfdiv   -mno-fdiv	 -mdiv	 -mno-div  -march=ISA-
	   string    -mtune=processor-string	-mpreferred-stack-boundary=num
	   -msmall-data-limit=N-bytes	 -msave-restore	     -mno-save-restore
	   -mshorten-memrefs	     -mno-shorten-memrefs	-mstrict-align
	   -mno-strict-align	     -mcmodel=medlow	       -mcmodel=medany
	   -mexplicit-relocs	 -mno-explicit-relocs	 -mrelax    -mno-relax
	   -mriscv-attribute	   -mmo-riscv-attribute	     -malign-data=type
	   -mbig-endian	     -mlittle-endian	+-mstack-protector-guard=guard
	   -mstack-protector-guard-reg=reg
	   +-mstack-protector-guard-offset=offset

	   RL78	Options	-msim	-mmul=none   -mmul=g13	 -mmul=g14   -mallregs
	   -mcpu=g10	 -mcpu=g13     -mcpu=g14     -mg10     -mg13	 -mg14
	   -m64bit-doubles  -m32bit-doubles  -msave-mduc-in-interrupts

	   RS/6000  and	  PowerPC   Options   -mcpu=cpu-type   -mtune=cpu-type
	   -mcmodel=code-model	   -mpowerpc64	   -maltivec	  -mno-altivec
	   -mpowerpc-gpopt	   -mno-powerpc-gpopt	      -mpowerpc-gfxopt
	   -mno-powerpc-gfxopt	-mmfcrf	  -mno-mfcrf   -mpopcntb  -mno-popcntb
	   -mpopcntd   -mno-popcntd  -mfprnd   -mno-fprnd  -mcmpb    -mno-cmpb
	   -mhard-dfp	    -mno-hard-dfp      -mfull-toc	 -mminimal-toc
	   -mno-fp-in-toc     -mno-sum-in-toc	 -m64	  -m32	   -mxl-compat
	   -mno-xl-compat   -mpe  -malign-power	  -malign-natural -msoft-float
	   -mhard-float	  -mmultiple   -mno-multiple   -mupdate	   -mno-update
	   -mavoid-indexed-addresses		  -mno-avoid-indexed-addresses
	   -mfused-madd	    -mno-fused-madd	-mbit-align	-mno-bit-align
	   -mstrict-align   -mno-strict-align	-mrelocatable -mno-relocatable
	   -mrelocatable-lib  -mno-relocatable-lib -mtoc   -mno-toc   -mlittle
	   -mlittle-endian    -mbig   -mbig-endian  -mdynamic-no-pic   -mswdiv
	   -msingle-pic-base		-mprioritize-restricted-insns=priority
	   -msched-costly-dep=dependence_type	    -minsert-sched-nops=scheme
	   -mcall-aixdesc     -mcall-eabi      -mcall-freebsd	  -mcall-linux
	   -mcall-netbsd     -mcall-openbsd    -mcall-sysv    -mcall-sysv-eabi
	   -mcall-sysv-noeabi  -mtraceback=traceback_type  -maix-struct-return
	   -msvr4-struct-return	   -mabi=abi-type    -msecure-plt    -mbss-plt
	   -mlongcall	     -mno-longcall	  -mpltseq	   -mno-pltseq
	   -mblock-move-inline-limit=num      -mblock-compare-inline-limit=num
	   -mblock-compare-inline-loop-limit=num  -mno-block-ops-unaligned-vsx
	   -mstring-compare-inline-limit=num	-misel	  -mno-isel   -mvrsave
	   -mno-vrsave -mmulhw	 -mno-mulhw  -mdlmzb   -mno-dlmzb  -mprototype
	   -mno-prototype  -msim  -mmvme  -mads	 -myellowknife	-memb  -msdata
	   -msdata=opt	 -mreadonly-in-sdata   -mvxworks    -G	 num   -mrecip
	   -mrecip=opt	  -mno-recip   -mrecip-precision  -mno-recip-precision
	   -mveclibabi=type  -mfriz  -mno-friz	-mpointers-to-nested-functions
	   -mno-pointers-to-nested-functions		   -msave-toc-indirect
	   -mno-save-toc-indirect     -mpower8-fusion	   -mno-mpower8-fusion
	   -mpower8-vector   -mno-power8-vector	 -mcrypto   -mno-crypto	 -mhtm
	   -mno-htm   -mquad-memory    -mno-quad-memory	  -mquad-memory-atomic
	   -mno-quad-memory-atomic -mcompat-align-parm	-mno-compat-align-parm
	   -mfloat128		  -mno-float128		   -mfloat128-hardware
	   -mno-float128-hardware     -mgnu-attribute	    -mno-gnu-attribute
	   -mstack-protector-guard=guard       -mstack-protector-guard-reg=reg
	   -mstack-protector-guard-offset=offset   -mprefixed	 -mno-prefixed
	   -mpcrel  -mno-pcrel	-mmma -mno-mmma	-mrop-protect -mno-rop-protect
	   -mprivileged	-mno-privileged

	   RX Options -m64bit-doubles  -m32bit-doubles	 -fpu	-nofpu	-mcpu=
	   -mbig-endian-data	 -mlittle-endian-data	 -msmall-data	 -msim
	   -mno-sim	 -mas100-syntax	       -mno-as100-syntax       -mrelax
	   -mmax-constant-size=	  -mint-register=  -mpid  -mallow-string-insns
	   -mno-allow-string-insns  -mjsr   -mno-warn-multiple-fast-interrupts
	   -msave-acc-in-interrupts

	   S/390   and	 zSeries   Options   -mtune=cpu-type   -march=cpu-type
	   -mhard-float	     -msoft-float	-mhard-dfp	 -mno-hard-dfp
	   -mlong-double-64    -mlong-double-128  -mbackchain	-mno-backchain
	   -mpacked-stack   -mno-packed-stack  -msmall-exec    -mno-small-exec
	   -mmvcle  -mno-mvcle -m64  -m31  -mdebug  -mno-debug	-mesa  -mzarch
	   -mhtm       -mvx	 -mzvector     -mtpf-trace	-mno-tpf-trace
	   -mtpf-trace-skip  -mno-tpf-trace-skip -mfused-madd  -mno-fused-madd
	   -mwarn-framesize  -mwarn-dynamicstack  -mstack-size	 -mstack-guard
	   -mhotpatch=halfwords,halfwords

	   Score  Options -meb	-mel -mnhwloop -muls -mmac -mscore5  -mscore5u
	   -mscore7  -mscore7d

	   SH Options -m1  -m2	-m2e -m2a-nofpu	 -m2a-single-only  -m2a-single
	   -m2a	 -m3   -m3e  -m4-nofpu	  -m4-single-only    -m4-single	   -m4
	   -m4a-nofpu	-m4a-single-only   -m4a-single	 -m4a	-m4al -mb  -ml
	   -mdalign   -mrelax  -mbigtable   -mfmovd   -mrenesas	  -mno-renesas
	   -mnomacsave	    -mieee	 -mno-ieee	 -mbitops      -misize
	   -minline-ic_invalidate    -mpadstruct    -mprefergot	    -musermode
	   -multcost=number	    -mdiv=strategy	 -mdivsi3_libfunc=name
	   -mfixed-range=register-range		    -maccumulate-outgoing-args
	   -matomic-model=atomic-model	    -mbranch-cost=num	   -mzdcbranch
	   -mno-zdcbranch	-mcbranch-force-delay-slot	  -mfused-madd
	   -mno-fused-madd     -mfsca	  -mno-fsca	-mfsrra	    -mno-fsrra
	   -mpretend-cmove  -mtas

	   Solaris 2 Options  -mclear-hwcap   -mno-clear-hwcap	 -mimpure-text
	   -mno-impure-text -pthreads

	   SPARC  Options  -mcpu=cpu-type  -mtune=cpu-type -mcmodel=code-model
	   -mmemory-model=mem-model  -m32   -m64   -mapp-regs	 -mno-app-regs
	   -mfaster-structs    -mno-faster-structs   -mflat   -mno-flat	 -mfpu
	   -mno-fpu	 -mhard-float	   -msoft-float	     -mhard-quad-float
	   -msoft-quad-float -mstack-bias  -mno-stack-bias -mstd-struct-return
	   -mno-std-struct-return  -munaligned-doubles	-mno-unaligned-doubles
	   -muser-mode	-mno-user-mode -mv8plus	 -mno-v8plus  -mvis   -mno-vis
	   -mvis2   -mno-vis2	-mvis3	 -mno-vis3  -mvis4  -mno-vis4  -mvis4b
	   -mno-vis4b  -mcbcond	  -mno-cbcond	-mfmaf	 -mno-fmaf    -mfsmuld
	   -mno-fsmuld	-mpopc	 -mno-popc   -msubxc   -mno-subxc -mfix-at697f
	   -mfix-ut699	-mfix-ut700  -mfix-gr712rc -mlra  -mno-lra

	   System V Options -Qy	 -Qn  -YP,paths	 -Ym,dir

	   TILE-Gx    Options	 -mcpu=CPU     -m32	-m64	  -mbig-endian
	   -mlittle-endian -mcmodel=code-model

	   TILEPro Options -mcpu=cpu  -m32

	   V850	  Options   -mlong-calls    -mno-long-calls    -mep    -mno-ep
	   -mprolog-function  -mno-prolog-function  -mspace  -mtda=n   -msda=n
	   -mzda=n	 -mapp-regs	   -mno-app-regs       -mdisable-callt
	   -mno-disable-callt -mv850e2v3  -mv850e2  -mv850e1  -mv850es -mv850e
	   -mv850   -mv850e3v5	-mloop	 -mrelax   -mlong-jumps	  -msoft-float
	   -mhard-float	-mgcc-abi -mrh850-abi -mbig-switch

	   VAX Options -mg  -mgnu  -munix

	   Visium   Options  -mdebug   -msim   -mfpu   -mno-fpu	  -mhard-float
	   -msoft-float	    -mcpu=cpu-type	-mtune=cpu-type	     -msv-mode
	   -muser-mode

	   VMS	Options	 -mvms-return-codes   -mdebug-main=prefix   -mmalloc64
	   -mpointer-size=size

	   VxWorks Options -mrtp  -non-static  -Bstatic	 -Bdynamic -Xbind-lazy
	   -Xbind-now

	   x86 Options -mtune=cpu-type	 -march=cpu-type  -mtune-ctrl=feature-
	   list	      -mdump-tune-features	-mno-default	 -mfpmath=unit
	   -masm=dialect   -mno-fancy-math-387	 -mno-fp-ret-in-387    -m80387
	   -mhard-float	      -msoft-float	-mno-wide-multiply	 -mrtd
	   -malign-double			-mpreferred-stack-boundary=num
	   -mincoming-stack-boundary=num   -mcld    -mcx16    -msahf   -mmovbe
	   -mcrc32 -mmwait -mrecip  -mrecip=opt	-mvzeroupper   -mprefer-avx128
	   -mprefer-vector-width=opt  -mmmx   -msse   -msse2   -msse3  -mssse3
	   -msse4.1  -msse4.2  -msse4	-mavx  -mavx2	-mavx512f   -mavx512pf
	   -mavx512er	  -mavx512cd	 -mavx512vl   -mavx512bw    -mavx512dq
	   -mavx512ifma	  -mavx512vbmi	 -msha	 -maes	-mpclmul    -mfsgsbase
	   -mrdrnd     -mf16c	  -mfma	   -mpconfig	-mwbnoinvd   -mptwrite
	   -mprefetchwt1  -mclflushopt	 -mclwb	  -mxsavec   -mxsaves  -msse4a
	   -m3dnow   -m3dnowa	-mpopcnt   -mabm   -mbmi  -mtbm	 -mfma4	 -mxop
	   -madx  -mlzcnt  -mbmi2  -mfxsr  -mxsave  -mxsaveopt	 -mrtm	 -mhle
	   -mlwp   -mmwaitx    -mclzero	   -mpku   -mthreads   -mgfni	-mvaes
	   -mwaitpkg	 -mshstk     -mmanual-endbr	 -mforce-indirect-call
	   -mavx512vbmi2  -mavx512bf16	-menqcmd  -mvpclmulqdq	-mavx512bitalg
	   -mmovdiri	 -mmovdir64b	  -mavx512vpopcntdq	-mavx5124fmaps
	   -mavx512vnni	  -mavx5124vnniw   -mprfchw   -mrdpid  -mrdseed	 -msgx
	   -mavx512vp2intersect	-mserialize -mtsxldtrk -mamx-tile   -mamx-int8
	   -mamx-bf16  -muintr	-mhreset  -mavxvnni -mcldemote	-mms-bitfields
	   -mno-align-stringops				-minline-all-stringops
	   -minline-stringops-dynamically      -mstringop-strategy=alg	  -mkl
	   -mwidekl   -mmemcpy-strategy=strategy    -mmemset-strategy=strategy
	   -mpush-args	   -maccumulate-outgoing-args	  -m128bit-long-double
	   -m96bit-long-double	      -mlong-double-64	      -mlong-double-80
	   -mlong-double-128   -mregparm=num	-msseregparm  -mveclibabi=type
	   -mvect8-ret-in-mem -mpc32  -mpc64  -mpc80 -mdaz-ftz	-mstackrealign
	   -momit-leaf-frame-pointer   -mno-red-zone  -mno-tls-direct-seg-refs
	   -mcmodel=code-model	 -mabi=name   -maddress-mode=mode  -m32	  -m64
	   -mx32     -m16    -miamcu	-mlarge-data-threshold=num   -msse2avx
	   -mfentry	  -mrecord-mcount	-mnop-mcount	   -m8bit-idiv
	   -minstrument-return=type  -mfentry-name=name	 -mfentry-section=name
	   -mavx256-split-unaligned-load	-mavx256-split-unaligned-store
	   -malign-data=type			 -mstack-protector-guard=guard
	   -mstack-protector-guard-reg=reg
	   -mstack-protector-guard-offset=offset
	   -mstack-protector-guard-symbol=symbol	   -mgeneral-regs-only
	   -mcall-ms2sysv-xlogues		      -mindirect-branch=choice
	   -mfunction-return=choice		    -mindirect-branch-register
	   -mharden-sls=choice -mindirect-branch-cs-prefix -mneeded

	   x86	 Windows   Options  -mconsole	-mcygwin   -mno-cygwin	 -mdll
	   -mnop-fun-dllimport	  -mthread   -municode	  -mwin32    -mwindows
	   -fno-set-stack-executable

	   Xstormy16 Options -msim

	   Xtensa     Options	  -mconst16	 -mno-const16	  -mfused-madd
	   -mno-fused-madd	   -mforce-no-pic	  -mserialize-volatile
	   -mno-serialize-volatile		       -mtext-section-literals
	   -mno-text-section-literals	-mauto-litpools	    -mno-auto-litpools
	   -mtarget-align    -mno-target-align	 -mlongcalls	-mno-longcalls
	   -mabi=abi-type

	   zSeries Options See S/390 and zSeries Options.

   Options Controlling the Kind	of Output
       Compilation can involve up to four stages:  preprocessing,  compilation
       proper,	assembly and linking, always in	that order.  GCC is capable of
       preprocessing and compiling several files either	into several assembler
       input files, or into one	assembler  input  file;	 then  each  assembler
       input file produces an object file, and linking combines	all the	object
       files  (those  newly  compiled,	and  those specified as	input) into an
       executable file.

       For any given input file, the file name suffix determines what kind  of
       compilation is done:

       file.c
	   C source code that must be preprocessed.

       file.i
	   C source code that should not be preprocessed.

       file.ii
	   C++ source code that	should not be preprocessed.

       file.m
	   Objective-C	source code.  Note that	you must link with the libobjc
	   library to make an Objective-C program work.

       file.mi
	   Objective-C source code that	should not be preprocessed.

       file.mm
       file.M
	   Objective-C++ source	code.	Note  that  you	 must  link  with  the
	   libobjc  library  to	make an	Objective-C++ program work.  Note that
	   .M refers to	a literal capital M.

       file.mii
	   Objective-C++ source	code that should not be	preprocessed.

       file.h
	   C, C++, Objective-C or Objective-C++	header file to be turned  into
	   a  precompiled header (default), or C, C++ header file to be	turned
	   into	an Ada spec (via the -fdump-ada-spec switch).

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
	   C++ source code that	must be	preprocessed.  Note that in .cxx,  the
	   last	 two letters must both be literally x.	Likewise, .C refers to
	   a literal capital C.

       file.mm
       file.M
	   Objective-C++ source	code that must be preprocessed.

       file.mii
	   Objective-C++ source	code that should not be	preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
	   C++ header file to be turned	into a precompiled header or Ada spec.

       file.f
       file.for
       file.ftn
	   Fixed form Fortran source code that should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
	   Fixed form Fortran source code that must be preprocessed (with  the
	   traditional preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
	   Free	form Fortran source code that should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
	   Free	 form  Fortran source code that	must be	preprocessed (with the
	   traditional preprocessor).

       file.go
	   Go source code.

       file.brig
	   BRIG	files (binary representation of	HSAIL).

       file.d
	   D source code.

       file.di
	   D interface file.

       file.dd
	   D documentation code	(Ddoc).

       file.ads
	   Ada source code file	that contains a	library	 unit  declaration  (a
	   declaration	of  a  package,	 subprogram,  or generic, or a generic
	   instantiation), or a	library	unit renaming declaration (a  package,
	   generic,  or	subprogram renaming declaration).  Such	files are also
	   called specs.

       file.adb
	   Ada source code file	containing a library unit body	(a  subprogram
	   or package body).  Such files are also called bodies.

       file.s
	   Assembler code.

       file.S
       file.sx
	   Assembler code that must be preprocessed.

       other
	   An object file to be	fed straight into linking.  Any	file name with
	   no recognized suffix	is treated this	way.

       You can specify the input language explicitly with the -x option:

       -x language
	   Specify  explicitly	the  language  for  the	 following input files
	   (rather than	letting	the compiler choose a  default	based  on  the
	   file	 name  suffix).	  This	option	applies	to all following input
	   files until the next	-x option.  Possible values for	language are:

		   c  c-header	cpp-output
		   c++	c++-header  c++-system-header c++-user-header c++-cpp-output
		   objective-c	objective-c-header  objective-c-cpp-output
		   objective-c++ objective-c++-header objective-c++-cpp-output
		   assembler  assembler-with-cpp
		   ada
		   d
		   f77	f77-cpp-input f95  f95-cpp-input
		   go
		   brig

       -x none
	   Turn	off any	specification of a language, so	that subsequent	 files
	   are	handled	 according to their file name suffixes (as they	are if
	   -x has not been used	at all).

       If you only want	some of	the stages of compilation, you can use -x  (or
       filename	 suffixes)  to tell gcc	where to start,	and one	of the options
       -c, -S, or -E to	say where gcc is to stop.  Note	that some combinations
       (for example, -x	cpp-output -E) instruct	gcc to do nothing at all.

       -c  Compile or assemble the source files, but do	not link.  The linking
	   stage simply	is not done.  The ultimate output is in	the form of an
	   object file for each	source file.

	   By default, the object file name for	 a  source  file  is  made  by
	   replacing the suffix	.c, .i,	.s, etc., with .o.

	   Unrecognized	 input	files,	not requiring compilation or assembly,
	   are ignored.

       -S  Stop	after the stage	of compilation proper; do not  assemble.   The
	   output  is  in  the	form  of  an assembler code file for each non-
	   assembler input file	specified.

	   By default, the assembler file name for a source file  is  made  by
	   replacing the suffix	.c, .i,	etc., with .s.

	   Input files that don't require compilation are ignored.

       -E  Stop	after the preprocessing	stage; do not run the compiler proper.
	   The	output	is  in	the form of preprocessed source	code, which is
	   sent	to the standard	output.

	   Input files that don't require preprocessing	are ignored.

       -o file
	   Place the primary output in file file.  This	 applies  to  whatever
	   sort	of output is being produced, whether it	be an executable file,
	   an object file, an assembler	file or	preprocessed C code.

	   If -o is not	specified, the default is to put an executable file in
	   a.out, the object file for source.suffix in source.o, its assembler
	   file	 in  source.s, a precompiled header file in source.suffix.gch,
	   and all preprocessed	C source on standard output.

	   Though -o names only	the primary output, it also affects the	naming
	   of auxiliary	and dump outputs.  See	the  examples  below.	Unless
	   overridden,	both  auxiliary	outputs	and dump outputs are placed in
	   the same directory as the primary output.   In  auxiliary  outputs,
	   the suffix of the input file	is replaced with that of the auxiliary
	   output  file	 type; in dump outputs,	the suffix of the dump file is
	   appended to the input file suffix.  In  compilation	commands,  the
	   base	name of	both auxiliary and dump	outputs	is that	of the primary
	   output;  in	compile	 and  link  commands, the primary output name,
	   minus the executable	suffix,	is combined with the input file	 name.
	   If  both  share  the	 same  base name, disregarding the suffix, the
	   result of the combination is	that base name,	 otherwise,  they  are
	   concatenated, separated by a	dash.

		   gcc -c foo.c	...

	   will	 use  foo.o  as	 the primary output, and place aux outputs and
	   dumps next to it, e.g., aux file  foo.dwo  for  -gsplit-dwarf,  and
	   dump	file foo.c.???r.final for -fdump-rtl-final.

	   If  a  non-linker output file is explicitly specified, aux and dump
	   files by default take the same base name:

		   gcc -c foo.c	-o dir/foobar.o	...

	   will	name aux outputs dir/foobar.* and dump outputs dir/foobar.c.*.

	   A linker output will	instead	prefix aux and dump outputs:

		   gcc foo.c bar.c -o dir/foobar ...

	   will	  generally   name   aux    outputs    dir/foobar-foo.*	   and
	   dir/foobar-bar.*,   and   dump   outputs   dir/foobar-foo.c.*   and
	   dir/foobar-bar.c.*.

	   The one exception to	the above is when the  executable  shares  the
	   base	name with the single input:

		   gcc foo.c -o	dir/foo	...

	   in  which  case  aux	 outputs  are named dir/foo.* and dump outputs
	   named dir/foo.c.*.

	   The location	and the	names of auxiliary and	dump  outputs  can  be
	   adjusted   by   the	options	 -dumpbase,  -dumpbase-ext,  -dumpdir,
	   -save-temps=cwd, and	-save-temps=obj.

       -dumpbase dumpbase
	   This	option sets the	base name for auxiliary	and dump output	files.
	   It  does  not  affect  the  name  of	 the  primary	output	 file.
	   Intermediate	 outputs,  when	preserved, are not regarded as primary
	   outputs, but	as auxiliary outputs:

		   gcc -save-temps -S foo.c

	   saves the (no longer) temporary preprocessed	 file  in  foo.i,  and
	   then	compiles to the	(implied) output file foo.s, whereas:

		   gcc -save-temps -dumpbase save-foo -c foo.c

	   preprocesses	 to  in	 save-foo.i,  compiles	to  save-foo.s (now an
	   intermediate, thus auxiliary	output), and  then  assembles  to  the
	   (implied) output file foo.o.

	   Absent  this	 option,  dump and aux files take their	names from the
	   input file, or  from	 the  (non-linker)  output  file,  if  one  is
	   explicitly  specified:  dump	 output	files (e.g. those requested by
	   -fdump-* options) with the input name suffix, and aux output	 files
	   (those  requested  by  other	 non-dump options, e.g.	"-save-temps",
	   "-gsplit-dwarf", "-fcallgraph-info")	without	it.

	   Similar suffix differentiation of  dump  and	 aux  outputs  can  be
	   attained   for  explicitly-given  -dumpbase	basename.suf  by  also
	   specifying -dumpbase-ext .suf.

	   If dumpbase is explicitly specified with any	 directory  component,
	   any	dumppfx	 specification	(e.g.  -dumpdir	 or  -save-temps=*) is
	   ignored, and	instead	of appending to	it, dumpbase  fully  overrides
	   it:

		   gcc foo.c -c	-o dir/foo.o -dumpbase alt/foo \
		     -dumpdir pfx- -save-temps=cwd ...

	   creates  auxiliary  and  dump outputs named alt/foo.*, disregarding
	   dir/	in -o, the ./ prefix implied by	-save-temps=cwd, and  pfx-  in
	   -dumpdir.

	   When	 -dumpbase  is	specified  in a	command	that compiles multiple
	   inputs, or that compiles and	then links, it may  be	combined  with
	   dumppfx,  as	 specified  under  -dumpdir.  Then, each input file is
	   compiled  using  the	 combined  dumppfx,  and  default  values  for
	   dumpbase and	auxdropsuf are computed	for each input file:

		   gcc foo.c bar.c -c -dumpbase	main ...

	   creates  foo.o and bar.o as primary outputs,	and avoids overwriting
	   the auxiliary and dump outputs by using the dumpbase	as  a  prefix,
	   creating   auxiliary	  and	dump  outputs  named  main-foo.*   and
	   main-bar.*.

	   An empty string specified as	dumpbase avoids	the influence  of  the
	   output  basename in the naming of auxiliary and dump	outputs	during
	   compilation,	computing default values :

		   gcc -c foo.c	-o dir/foobar.o	-dumpbase " ...

	   will	name aux outputs dir/foo.* and dump outputs dir/foo.c.*.  Note
	   how their  basenames	 are  taken  from  the	input  name,  but  the
	   directory still defaults to that of the output.

	   The	empty-string  dumpbase	does not prevent the use of the	output
	   basename for	outputs	during linking:

		   gcc foo.c bar.c -o dir/foobar -dumpbase " -flto ...

	   The compilation of the source files	will  name  auxiliary  outputs
	   dir/foo.*   and   dir/bar.*,	  and  dump  outputs  dir/foo.c.*  and
	   dir/bar.c.*.	 LTO recompilation during linking will use dir/foobar.
	   as the prefix for dumps and auxiliary files.

       -dumpbase-ext auxdropsuf
	   When	forming	the name of an auxiliary (but not a dump) output file,
	   drop	 trailing  auxdropsuf  from  dumpbase  before  appending   any
	   suffixes.   If not specified, this option defaults to the suffix of
	   a default dumpbase,	i.e.,  the  suffix  of	the  input  file  when
	   -dumpbase  is  not  present	in  the	 command  line,	or dumpbase is
	   combined with dumppfx.

		   gcc foo.c -c	-o dir/foo.o -dumpbase x-foo.c -dumpbase-ext .c	...

	   creates dir/foo.o as	 the  main  output,  and  generates  auxiliary
	   outputs  in dir/x-foo.*, taking the location	of the primary output,
	   and dropping	the .c suffix from the dumpbase.  Dump outputs	retain
	   the suffix: dir/x-foo.c.*.

	   This	 option	 is  disregarded  if it	does not match the suffix of a
	   specified dumpbase, except as  an  alternative  to  the  executable
	   suffix  when	 appending  the	linker output base name	to dumppfx, as
	   specified below:

		   gcc foo.c bar.c -o main.out -dumpbase-ext .out ...

	   creates main.out as the primary output, and avoids overwriting  the
	   auxiliary  and  dump	 outputs  by  using  the executable name minus
	   auxdropsuf as a prefix, creating auxiliary outputs named main-foo.*
	   and	main-bar.*   and   dump	  outputs   named   main-foo.c.*   and
	   main-bar.c.*.

       -dumpdir	dumppfx
	   When	 forming  the  name  of	 an auxiliary or dump output file, use
	   dumppfx as a	prefix:

		   gcc -dumpdir	pfx- -c	foo.c ...

	   creates foo.o as the	primary	output,	and  auxiliary	outputs	 named
	   pfx-foo.*,  combining  the  given dumppfx with the default dumpbase
	   derived from	the default primary output, derived in turn  from  the
	   input  name.	  Dump	outputs	 also  take  the  input	 name  suffix:
	   pfx-foo.c.*.

	   If dumppfx is to be used as a directory name, it must  end  with  a
	   directory separator:

		   gcc -dumpdir	dir/ -c	foo.c -o obj/bar.o ...

	   creates  obj/bar.o  as  the	primary	 output, and auxiliary outputs
	   named dir/bar.*, combining  the  given  dumppfx  with  the  default
	   dumpbase  derived  from the primary output name.  Dump outputs also
	   take	the input name suffix: dir/bar.c.*.

	   It defaults to the location of the output file, unless  the	output
	   file	 is  a	special	file like "/dev/null". Options -save-temps=cwd
	   and -save-temps=obj override	this default, just  like  an  explicit
	   -dumpdir option.  In	case multiple such options are given, the last
	   one prevails:

		   gcc -dumpdir	pfx- -c	foo.c -save-temps=obj ...

	   outputs   foo.o,   with   auxiliary	outputs	 named	foo.*  because
	   -save-temps=* overrides the dumppfx given by	the  earlier  -dumpdir
	   option.    It  does	not  matter  that  =obj	 is  the  default  for
	   -save-temps,	nor  that  the	output	directory  is  implicitly  the
	   current directory.  Dump outputs are	named foo.c.*.

	   When	  compiling   from  multiple  input  files,  if	 -dumpbase  is
	   specified, dumpbase,	minus a	auxdropsuf  suffix,  and  a  dash  are
	   appended  to	 (or override, if containing any directory components)
	   an explicit or defaulted dumppfx, so	 that  each  of	 the  multiple
	   compilations	gets differently-named aux and dump outputs.

		   gcc foo.c bar.c -c -dumpdir dir/pfx-	-dumpbase main ...

	   outputs     auxiliary     dumps     to    dir/pfx-main-foo.*	   and
	   dir/pfx-main-bar.*, appending dumpbase- to dumppfx.	 Dump  outputs
	   retain   the	  input	  file	 suffix:   dir/pfx-main-foo.c.*	   and
	   dir/pfx-main-bar.c.*, respectively.	Contrast with the single-input
	   compilation:

		   gcc foo.c -c	-dumpdir dir/pfx- -dumpbase main ...

	   that, applying -dumpbase to a single	source,	does not  compute  and
	   append  a separate dumpbase per input file.	Its auxiliary and dump
	   outputs go in dir/pfx-main.*.

	   When	compiling and  then  linking  from  multiple  input  files,  a
	   defaulted  or  explicitly  specified	 dumppfx  also	undergoes  the
	   dumpbase- transformation above (e.g.	the compilation	of  foo.c  and
	   bar.c  above,  but  without -c).  If	neither	-dumpdir nor -dumpbase
	   are given, the  linker  output  base	 name,	minus  auxdropsuf,  if
	   specified,  or  the	executable  suffix  otherwise,	plus a dash is
	   appended to the  default  dumppfx  instead.	 Note,	however,  that
	   unlike earlier cases	of linking:

		   gcc foo.c bar.c -dumpdir dir/pfx- -o	main ...

	   does	 not  append the output	name main to dumppfx, because -dumpdir
	   is explicitly specified.  The goal is that the explicitly-specified
	   dumppfx may contain the  specified  output  name  as	 part  of  the
	   prefix, if desired; only an explicitly-specified -dumpbase would be
	   combined  with it, in order to avoid	simply discarding a meaningful
	   option.

	   When	compiling and then linking  from  a  single  input  file,  the
	   linker  output  base	 name  will  only  be  appended	to the default
	   dumppfx as above if it does not share the base name with the	single
	   input file name.  This has been  covered  in	 single-input  linking
	   cases  above,  but  not with	an explicit -dumpdir that inhibits the
	   combination,	even if	overridden by -save-temps=*:

		   gcc foo.c -dumpdir alt/pfx- -o dir/main.exe -save-temps=cwd ...

	   Auxiliary outputs are named foo.*, and dump outputs foo.c.*,	in the
	   current   working   directory   as	 ultimately    requested    by
	   -save-temps=cwd.

	   Summing  it	all up for an intuitive	though slightly	imprecise data
	   flow: the primary output name is broken into	a directory part and a
	   basename part; dumppfx is set to the	former,	unless	overridden  by
	   -dumpdir  or	 -save-temps=*,	 and  dumpbase	is  set	to the latter,
	   unless overriden by -dumpbase.  If there  are  multiple  inputs  or
	   linking,  this dumpbase may be combined with	dumppfx	and taken from
	   each	input file.  Auxiliary output names for	each input are	formed
	   by  combining  dumppfx,  dumpbase  minus  suffix, and the auxiliary
	   output suffix; dump output names are	only  different	 in  that  the
	   suffix from dumpbase	is retained.

	   When	 it  comes  to	auxiliary  and dump outputs created during LTO
	   recompilation, a combination	of dumppfx and dumpbase, as  given  or
	   as derived from the linker output name but not from inputs, even in
	   cases  in  which  this  combination	would not otherwise be used as
	   such, is passed down	with a trailing	period replacing the compiler-
	   added dash, if any, as a  -dumpdir  option  to  lto-wrapper;	 being
	   involved  in	 linking,  this	 program  does	not  normally  get any
	   -dumpbase and -dumpbase-ext,	and it ignores them.

	   When	running	sub-compilers, lto-wrapper appends LTO stage names  to
	   the	received dumppfx, ensures it contains a	directory component so
	   that	it overrides any -dumpdir, and passes  that  as	 -dumpbase  to
	   sub-compilers.

       -v  Print  (on  standard	error output) the commands executed to run the
	   stages of compilation.   Also  print	 the  version  number  of  the
	   compiler  driver  program  and of the preprocessor and the compiler
	   proper.

       -###
	   Like	-v except the commands are  not	 executed  and	arguments  are
	   quoted  unless they contain only alphanumeric characters or "./-_".
	   This	is useful for shell scripts to	capture	 the  driver-generated
	   command lines.

       --help
	   Print  (on  the  standard output) a description of the command-line
	   options understood by gcc.  If the -v option	is also	specified then
	   --help is also passed on to the various processes invoked  by  gcc,
	   so  that they can display the command-line options they accept.  If
	   the -Wextra option has also been specified  (prior  to  the	--help
	   option),  then  command-line	 options  that	have  no documentation
	   associated with them	are also displayed.

       --target-help
	   Print (on the standard output)  a  description  of  target-specific
	   command-line	options	for each tool.	For some targets extra target-
	   specific information	may also be printed.

       --help={class|[^]qualifier}[,...]
	   Print  (on  the  standard output) a description of the command-line
	   options understood by the compiler  that  fit  into	all  specified
	   classes and qualifiers.  These are the supported classes:

	   optimizers
	       Display	all  of	 the  optimization  options  supported	by the
	       compiler.

	   warnings
	       Display	all  of	 the  options  controlling  warning   messages
	       produced	by the compiler.

	   target
	       Display	target-specific	 options.   Unlike  the	 --target-help
	       option however,	target-specific	 options  of  the  linker  and
	       assembler  are  not  displayed.	This is	because	those tools do
	       not currently support the extended --help= syntax.

	   params
	       Display the values recognized by	the --param option.

	   language
	       Display the options supported for language, where  language  is
	       the  name  of one of the	languages supported in this version of
	       GCC.  If	an option is supported by all languages, one needs  to
	       select common class.

	   common
	       Display the options that	are common to all languages.

	   These are the supported qualifiers:

	   undocumented
	       Display only those options that are undocumented.

	   joined
	       Display	options	taking an argument that	appears	after an equal
	       sign  in	 the  same  continuous	piece  of   text,   such   as:
	       --help=target.

	   separate
	       Display	options	 taking	an argument that appears as a separate
	       word following the original option, such	as: -o output-file.

	   Thus	for example to display all  the	 undocumented  target-specific
	   switches supported by the compiler, use:

		   --help=target,undocumented

	   The sense of	a qualifier can	be inverted by prefixing it with the ^
	   character,  so  for	example	 to display all	binary warning options
	   (i.e., ones that are	either on or off  and  that  do	 not  take  an
	   argument) that have a description, use:

		   --help=warnings,^joined,^undocumented

	   The	argument  to  --help=  should  not  consist solely of inverted
	   qualifiers.

	   Combining  several  classes	is  possible,  although	 this  usually
	   restricts the output	so much	that there is nothing to display.  One
	   case	 where	it  does  work,	however, is when one of	the classes is
	   target.   For  example,  to	 display   all	 the   target-specific
	   optimization	options, use:

		   --help=target,optimizers

	   The	--help=	 option	 can  be  repeated  on the command line.  Each
	   successive use displays its requested class	of  options,  skipping
	   those  that	have  already  been  displayed.	  If  --help  is  also
	   specified anywhere on the command line then this  takes  precedence
	   over	any --help= option.

	   If  the  -Q	option	appears	on the command line before the --help=
	   option, then	the descriptive	text displayed by --help= is  changed.
	   Instead of describing the displayed options,	an indication is given
	   as  to whether the option is	enabled, disabled or set to a specific
	   value (assuming that	the compiler knows this	at the point where the
	   --help= option is used).

	   Here	is a truncated example from the	ARM port of gcc:

		     % gcc -Q -mabi=2 --help=target -c
		     The following options are target specific:
		     -mabi=				   2
		     -mabort-on-noreturn		   [disabled]
		     -mapcs				   [disabled]

	   The output is sensitive to the  effects  of	previous  command-line
	   options,   so  for  example	it  is	possible  to  find  out	 which
	   optimizations are enabled at	-O2 by using:

		   -Q -O2 --help=optimizers

	   Alternatively you  can  discover  which  binary  optimizations  are
	   enabled by -O3 by using:

		   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
		   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
		   diff	/tmp/O2-opts /tmp/O3-opts | grep enabled

       --version
	   Display the version number and copyrights of	the invoked GCC.

       -pass-exit-codes
	   Normally  the  gcc program exits with the code of 1 if any phase of
	   the compiler	returns	a non-success return  code.   If  you  specify
	   -pass-exit-codes,   the   gcc  program  instead  returns  with  the
	   numerically highest error produced by any phase returning an	 error
	   indication.	 The  C,  C++,	and  Fortran front ends	return 4 if an
	   internal compiler error is encountered.

       -pipe
	   Use pipes rather than temporary files for communication between the
	   various stages of compilation.  This	fails to work on some  systems
	   where  the  assembler  is  unable  to read from a pipe; but the GNU
	   assembler has no trouble.

       -specs=file
	   Process file	after the compiler reads in the	standard  specs	 file,
	   in order to override	the defaults which the gcc driver program uses
	   when	 determining  what  switches  to pass to cc1, cc1plus, as, ld,
	   etc.	 More than one -specs=file can be  specified  on  the  command
	   line, and they are processed	in order, from left to right.

       -wrapper
	   Invoke  all	subcommands  under a wrapper program.  The name	of the
	   wrapper program and its parameters are passed as a comma  separated
	   list.

		   gcc -c t.c -wrapper gdb,--args

	   This	 invokes  all  subprograms  of	gcc under gdb --args, thus the
	   invocation of cc1 is	gdb --args cc1 ....

       -ffile-prefix-map=old=new
	   When	 compiling  files  residing  in	 directory  old,  record   any
	   references to them in the result of the compilation as if the files
	   resided  in	directory  new	instead.   Specifying  this  option is
	   equivalent to specifying all	the individual -f*-prefix-map options.
	   This	can be used to make  reproducible  builds  that	 are  location
	   independent.	 See also -fmacro-prefix-map and -fdebug-prefix-map.

       -fplugin=name.so
	   Load	the plugin code	in file	name.so, assumed to be a shared	object
	   to be dlopen'd by the compiler.  The	base name of the shared	object
	   file	 is  used  to identify the plugin for the purposes of argument
	   parsing  (See  -fplugin-arg-name-key=value  below).	 Each	plugin
	   should define the callback functions	specified in the Plugins API.

       -fplugin-arg-name-key=value
	   Define  an argument called key with a value of value	for the	plugin
	   called name.

       -fdump-ada-spec[-slim]
	   For C and C++ source	and include files, generate corresponding  Ada
	   specs.

       -fada-spec-parent=unit
	   In  conjunction  with  -fdump-ada-spec[-slim]  above,  generate Ada
	   specs as child units	of parent unit.

       -fdump-go-spec=file
	   For	input  files  in  any  language,  generate  corresponding   Go
	   declarations	 in  file.   This generates Go "const",	"type",	"var",
	   and "func" declarations which may be	a useful way to	start  writing
	   a Go	interface to code written in some other	language.

       @file
	   Read	command-line options from file.	 The options read are inserted
	   in  place of	the original @file option.  If file does not exist, or
	   cannot be read, then	the option will	be treated literally, and  not
	   removed.

	   Options   in	 file  are  separated  by  whitespace.	 A  whitespace
	   character may be included in	an option by  surrounding  the	entire
	   option in either single or double quotes.  Any character (including
	   a  backslash)  may  be  included  by	 prefixing the character to be
	   included with a backslash.  The file	may itself contain  additional
	   @file options; any such options will	be processed recursively.

   Compiling C++ Programs
       C++  source files conventionally	use one	of the suffixes	.C, .cc, .cpp,
       .CPP, .c++, .cp,	or .cxx; C++ header files often	use .hh, .hpp, .H,  or
       (for  shared  template  code)  .tcc; and	preprocessed C++ files use the
       suffix .ii.  GCC	recognizes files with these names and compiles them as
       C++ programs even if  you  call	the  compiler  the  same  way  as  for
       compiling C programs (usually with the name gcc).

       However,	the use	of gcc does not	add the	C++ library.  g++ is a program
       that  calls  GCC	 and  automatically  specifies linking against the C++
       library.	 It treats .c, .h and .i files as C++ source files instead  of
       C  source  files	 unless	 -x is used.  This program is also useful when
       precompiling a C	header file  with  a  .h  extension  for  use  in  C++
       compilations.   On  many	 systems,  g++ is also installed with the name
       c++.

       When you	compile	C++  programs,	you  may  specify  many	 of  the  same
       command-line  options  that  you	 use  for  compiling  programs	in any
       language;  or  command-line  options  meaningful	 for  C	 and   related
       languages; or options that are meaningful only for C++ programs.

   Options Controlling C Dialect
       The  following  options	control	the dialect of C (or languages derived
       from C, such as C++, Objective-C	and Objective-C++) that	 the  compiler
       accepts:

       -ansi
	   In  C  mode,	 this  is  equivalent  to -std=c90. In C++ mode, it is
	   equivalent to -std=c++98.

	   This	turns off certain features of GCC that are  incompatible  with
	   ISO C90 (when compiling C code), or of standard C++ (when compiling
	   C++	code), such as the "asm" and "typeof" keywords,	and predefined
	   macros such as "unix" and "vax" that	identify the  type  of	system
	   you are using.  It also enables the undesirable and rarely used ISO
	   trigraph  feature.	For the	C compiler, it disables	recognition of
	   C++ style //	comments as well as the	"inline" keyword.

	   The alternate keywords "__asm__", "__extension__", "__inline__" and
	   "__typeof__"	continue to work despite -ansi.	 You would not want to
	   use them in an ISO C	program, of course, but	it is  useful  to  put
	   them	 in  header  files that	might be included in compilations done
	   with	-ansi.	Alternate predefined macros  such  as  "__unix__"  and
	   "__vax__" are also available, with or without -ansi.

	   The	-ansi  option  does  not cause non-ISO programs	to be rejected
	   gratuitously.  For that, -Wpedantic	is  required  in  addition  to
	   -ansi.

	   The	macro "__STRICT_ANSI__"	is predefined when the -ansi option is
	   used.  Some header files may	notice this  macro  and	 refrain  from
	   declaring certain functions or defining certain macros that the ISO
	   standard  doesn't  call  for; this is to avoid interfering with any
	   programs that might use these names for other things.

	   Functions that are normally built in	 but  do  not  have  semantics
	   defined  by	ISO  C	(such  as "alloca" and "ffs") are not built-in
	   functions when -ansi	is used.

       -std=
	   Determine the language standard.   This option  is  currently  only
	   supported when compiling C or C++.

	   The	compiler  can  accept  several	base standards,	such as	c90 or
	   c++98, and GNU dialects  of	those  standards,  such	 as  gnu90  or
	   gnu++98.   When  a base standard is specified, the compiler accepts
	   all	programs  following  that  standard  plus  those   using   GNU
	   extensions  that do not contradict it.  For example,	-std=c90 turns
	   off certain features	of GCC that are	 incompatible  with  ISO  C90,
	   such	 as  the  "asm"	 and  "typeof"	keywords,  but	not  other GNU
	   extensions that do not have a meaning in ISO	C90, such as  omitting
	   the middle term of a	"?:" expression. On the	other hand, when a GNU
	   dialect  of	a standard is specified, all features supported	by the
	   compiler are	enabled, even when those features change  the  meaning
	   of the base standard.  As a result, some strict-conforming programs
	   may	be rejected.  The particular standard is used by -Wpedantic to
	   identify which features are GNU extensions given  that  version  of
	   the	standard.  For	example	 -std=gnu90 -Wpedantic warns about C++
	   style // comments, while -std=gnu99 -Wpedantic does not.

	   A value for this option must	be provided; possible values are

	   c90
	   c89
	   iso9899:1990
	       Support all ISO	C90  programs  (certain	 GNU  extensions  that
	       conflict	with ISO C90 are disabled). Same as -ansi for C	code.

	   iso9899:199409
	       ISO C90 as modified in amendment	1.

	   c99
	   c9x
	   iso9899:1999
	   iso9899:199x
	       ISO  C99.  This standard	is substantially completely supported,
	       modulo bugs and floating-point issues (mainly but not  entirely
	       relating	 to  optional C99 features from	Annexes	F and G).  See
	       <http://gcc.gnu.org/c99status.html> for more information.   The
	       names c9x and iso9899:199x are deprecated.

	   c11
	   c1x
	   iso9899:2011
	       ISO  C11,  the  2011  revision  of  the	ISO  C standard.  This
	       standard	is substantially completely  supported,	 modulo	 bugs,
	       floating-point  issues  (mainly	but  not  entirely relating to
	       optional	C11 features from Annexes F and	G)  and	 the  optional
	       Annexes	K  (Bounds-checking interfaces)	and L (Analyzability).
	       The name	c1x is deprecated.

	   c17
	   c18
	   iso9899:2017
	   iso9899:2018
	       ISO C17,	the 2017 revision of the ISO C standard	(published  in
	       2018).	This standard is same as C11 except for	corrections of
	       defects (all of which are also applied with -std=c11) and a new
	       value of	"__STDC_VERSION__", and	so is supported	 to  the  same
	       extent as C11.

	   c2x The   next   version   of  the  ISO  C  standard,  still	 under
	       development.  The support for this version is experimental  and
	       incomplete.

	   gnu90
	   gnu89
	       GNU dialect of ISO C90 (including some C99 features).

	   gnu99
	   gnu9x
	       GNU dialect of ISO C99.	The name gnu9x is deprecated.

	   gnu11
	   gnu1x
	       GNU dialect of ISO C11.	The name gnu1x is deprecated.

	   gnu17
	   gnu18
	       GNU dialect of ISO C17.	This is	the default for	C code.

	   gnu2x
	       The   next   version   of  the  ISO  C  standard,  still	 under
	       development, plus GNU extensions.  The support for this version
	       is experimental and incomplete.

	   c++98
	   c++03
	       The 1998	ISO C++	standard plus the 2003	technical  corrigendum
	       and some	additional defect reports. Same	as -ansi for C++ code.

	   gnu++98
	   gnu++03
	       GNU dialect of -std=c++98.

	   c++11
	   c++0x
	       The  2011  ISO C++ standard plus	amendments.  The name c++0x is
	       deprecated.

	   gnu++11
	   gnu++0x
	       GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

	   c++14
	   c++1y
	       The 2014	ISO C++	standard plus amendments.  The name  c++1y  is
	       deprecated.

	   gnu++14
	   gnu++1y
	       GNU dialect of -std=c++14.  The name gnu++1y is deprecated.

	   c++17
	   c++1z
	       The  2017  ISO C++ standard plus	amendments.  The name c++1z is
	       deprecated.

	   gnu++17
	   gnu++1z
	       GNU dialect of -std=c++17.  This	is the default for  C++	 code.
	       The name	gnu++1z	is deprecated.

	   c++20
	   c++2a
	       The   2020  ISO	C++  standard  plus  amendments.   Support  is
	       experimental, and could change in incompatible ways  in	future
	       releases.  The name c++2a is deprecated.

	   gnu++20
	   gnu++2a
	       GNU  dialect of -std=c++20.  Support is experimental, and could
	       change in incompatible  ways  in	 future	 releases.   The  name
	       gnu++2a is deprecated.

	   c++2b
	   c++23
	       The  next  revision  of the ISO C++ standard, planned for 2023.
	       Support is  highly  experimental,  and  will  almost  certainly
	       change in incompatible ways in future releases.

	   gnu++2b
	   gnu++23
	       GNU dialect of -std=c++2b.  Support is highly experimental, and
	       will  almost  certainly	change	in incompatible	ways in	future
	       releases.

       -fgnu89-inline
	   The option -fgnu89-inline tells GCC	to  use	 the  traditional  GNU
	   semantics for "inline" functions when in C99	mode.

	   Using  this option is roughly equivalent to adding the "gnu_inline"
	   function attribute to all inline functions.

	   The option -fno-gnu89-inline	explicitly tells GCC to	 use  the  C99
	   semantics  for  "inline"  when  in  C99  or	gnu99  mode  (i.e., it
	   specifies the default behavior).  This option is not	 supported  in
	   -std=c90 or -std=gnu90 mode.

	   The	    preprocessor      macros	 "__GNUC_GNU_INLINE__"	   and
	   "__GNUC_STDC_INLINE__" may be used to check which semantics are  in
	   effect for "inline" functions.

       -fpermitted-flt-eval-methods=style
	   ISO/IEC   TS	  18661-3   defines   new   permissible	  values   for
	   "FLT_EVAL_METHOD" that indicate that	operations and constants  with
	   a semantic type that	is an interchange or extended format should be
	   evaluated  to  the  precision  and  range  of that type.  These new
	   values are a	superset of those permitted under C99/C11, which  does
	   not	 specify   the	 meaning   of	other	positive   values   of
	   "FLT_EVAL_METHOD".  As such,	code conforming	to C11	may  not  have
	   been	written	expecting the possibility of the new values.

	   -fpermitted-flt-eval-methods	 specifies whether the compiler	should
	   allow only the values of "FLT_EVAL_METHOD" specified	in C99/C11, or
	   the extended	set of values specified	in ISO/IEC TS 18661-3.

	   style is either "c11" or "ts-18661-3" as appropriate.

	   The default	when  in  a  standards	compliant  mode	 (-std=c11  or
	   similar)  is	-fpermitted-flt-eval-methods=c11.  The default when in
	   a	 GNU	 dialect     (-std=gnu11      or      similar)	    is
	   -fpermitted-flt-eval-methods=ts-18661-3.

       -aux-info filename
	   Output  to  the  given  filename  prototyped	 declarations  for all
	   functions declared and/or defined in	a translation unit,  including
	   those  in  header  files.   This  option is silently	ignored	in any
	   language other than C.

	   Besides declarations, the file indicates, in	comments,  the	origin
	   of each declaration (source file and	line), whether the declaration
	   was	implicit,  prototyped  or  unprototyped	(I, N for new or O for
	   old,	respectively, in the first character after the line number and
	   the colon), and whether it came from	a declaration or a  definition
	   (C or F, respectively, in the following character).	In the case of
	   function  definitions,  a  K&R-style	 list of arguments followed by
	   their declarations is also provided,	 inside	 comments,  after  the
	   declaration.

       -fallow-parameterless-variadic-functions
	   Accept variadic functions without named parameters.

	   Although it is possible to define such a function, this is not very
	   useful  as  it is not possible to read the arguments.  This is only
	   supported for C as this construct is	allowed	by C++.

       -fno-asm
	   Do not recognize "asm", "inline" or "typeof"	as a keyword, so  that
	   code	 can use these words as	identifiers.  You can use the keywords
	   "__asm__", "__inline__" and "__typeof__"  instead.	-ansi  implies
	   -fno-asm.

	   In  C++, this switch	only affects the "typeof" keyword, since "asm"
	   and "inline"	are standard  keywords.	  You  may  want  to  use  the
	   -fno-gnu-keywords  flag instead, which has the same effect.	In C99
	   mode	(-std=c99 or -std=gnu99), this switch only affects  the	 "asm"
	   and	"typeof" keywords, since "inline" is a standard	keyword	in ISO
	   C99.

       -fno-builtin
       -fno-builtin-function
	   Don't  recognize  built-in  functions  that	do  not	  begin	  with
	   __builtin_ as prefix.

	   GCC	normally  generates  special  code  to handle certain built-in
	   functions more efficiently; for instance,  calls  to	 "alloca"  may
	   become  single  instructions	 which	adjust the stack directly, and
	   calls to "memcpy" may become	inline copy loops.  The	resulting code
	   is often both smaller and faster, but since the function  calls  no
	   longer  appear as such, you cannot set a breakpoint on those	calls,
	   nor can you change the behavior of the functions by linking with  a
	   different library.  In addition, when a function is recognized as a
	   built-in  function,	GCC may	use information	about that function to
	   warn	about problems with calls to that  function,  or  to  generate
	   more	 efficient  code,  even	 if  the resulting code	still contains
	   calls to that function.   For  example,  warnings  are  given  with
	   -Wformat  for  bad  calls to	"printf" when "printf" is built	in and
	   "strlen" is known not to modify global memory.

	   With	the -fno-builtin-function option only  the  built-in  function
	   function is disabled.  function must	not begin with __builtin_.  If
	   a  function	is  named that is not built-in in this version of GCC,
	   this	  option   is	ignored.    There    is	   no	 corresponding
	   -fbuiltin-function option; if you wish to enable built-in functions
	   selectively	when  using  -fno-builtin  or  -ffreestanding, you may
	   define macros such as:

		   #define abs(n)	   __builtin_abs ((n))
		   #define strcpy(d, s)	   __builtin_strcpy ((d), (s))

       -fgimple
	   Enable parsing of  function	definitions  marked  with  "__GIMPLE".
	   This	 is an experimental feature that allows	unit testing of	GIMPLE
	   passes.

       -fhosted
	   Assert that compilation targets a hosted environment.  This implies
	   -fbuiltin.  A  hosted  environment  is  one	in  which  the	entire
	   standard  library  is  available,  and in which "main" has a	return
	   type	of "int".  Examples are	nearly	everything  except  a  kernel.
	   This	is equivalent to -fno-freestanding.

       -ffreestanding
	   Assert  that	 compilation targets a freestanding environment.  This
	   implies -fno-builtin.  A freestanding environment is	one  in	 which
	   the	standard  library  may	not exist, and program startup may not
	   necessarily be at "main".   The  most  obvious  example  is	an  OS
	   kernel.  This is equivalent to -fno-hosted.

       -fopenacc
	   Enable  handling  of	 OpenACC directives "#pragma acc" in C/C++ and
	   "!$acc" in Fortran.	When  -fopenacc	 is  specified,	 the  compiler
	   generates  accelerated  code	 according  to the OpenACC Application
	   Programming Interface v2.6 <https://www.openacc.org>.  This	option
	   implies  -pthread,  and thus	is only	supported on targets that have
	   support for -pthread.

       -fopenacc-dim=geom
	   Specify default compute dimensions  for  parallel  offload  regions
	   that	 do  not  explicitly  specify.	 The geom value	is a triple of
	   ':'-separated sizes,	in order 'gang', 'worker'  and,	 'vector'.   A
	   size	can be omitted,	to use a target-specific default value.

       -fopenmp
	   Enable  handling  of	 OpenMP	 directives "#pragma omp" in C/C++ and
	   "!$omp" in Fortran.	 When  -fopenmp	 is  specified,	 the  compiler
	   generates parallel code according to	the OpenMP Application Program
	   Interface   v4.5  <https://www.openmp.org>.	 This  option  implies
	   -pthread, and thus is only supported	on targets that	 have  support
	   for -pthread. -fopenmp implies -fopenmp-simd.

       -fopenmp-simd
	   Enable  handling  of	OpenMP's SIMD directives with "#pragma omp" in
	   C/C++ and "!$omp" in	Fortran. Other OpenMP directives are ignored.

       -fgnu-tm
	   When	the option -fgnu-tm is specified, the compiler generates  code
	   for	the  Linux variant of Intel's current Transactional Memory ABI
	   specification document (Revision 1.1, May  6	 2009).	  This	is  an
	   experimental	 feature whose interface may change in future versions
	   of GCC, as the official specification changes.   Please  note  that
	   not all architectures are supported for this	feature.

	   For more information	on GCC's support for transactional memory,

	   Note	 that  the  transactional memory feature is not	supported with
	   non-call exceptions (-fnon-call-exceptions).

       -fms-extensions
	   Accept some non-standard constructs used in Microsoft header	files.

	   In C++ code,	this allows member names in structures to  be  similar
	   to previous types declarations.

		   typedef int UOW;
		   struct ABC {
		     UOW UOW;
		   };

	   Some	 cases	of  unnamed  fields  in	structures and unions are only
	   accepted with this option.

	   Note	that this option is off	for all	targets	except for x86 targets
	   using ms-abi.

       -fplan9-extensions
	   Accept some non-standard constructs used in Plan 9 code.

	   This	 enables  -fms-extensions,   permits   passing	 pointers   to
	   structures  with anonymous fields to	functions that expect pointers
	   to elements of the type of the  field,  and	permits	 referring  to
	   anonymous   fields  declared	 using	a  typedef.	This  is  only
	   supported for C, not	C++.

       -fcond-mismatch
	   Allow conditional expressions with mismatched types in  the	second
	   and	third  arguments.   The	 value	of such	an expression is void.
	   This	option is not supported	for C++.

       -flax-vector-conversions
	   Allow implicit conversions between vectors with  differing  numbers
	   of  elements	and/or incompatible element types.  This option	should
	   not be used for new code.

       -funsigned-char
	   Let the type	"char" be unsigned, like "unsigned char".

	   Each	kind of	machine	has a default for what "char" should  be.   It
	   is  either like "unsigned char" by default or like "signed char" by
	   default.

	   Ideally, a portable program should  always  use  "signed  char"  or
	   "unsigned  char"  when  it  depends on the signedness of an object.
	   But many programs have been written to use plain "char" and	expect
	   it  to  be  signed,	or  expect it to be unsigned, depending	on the
	   machines they were written for.  This option, and its inverse,  let
	   you make such a program work	with the opposite default.

	   The	type  "char"  is  always  a distinct type from each of "signed
	   char" or "unsigned char", even though its behavior is  always  just
	   like	one of those two.

       -fsigned-char
	   Let the type	"char" be signed, like "signed char".

	   Note	 that  this  is	equivalent to -fno-unsigned-char, which	is the
	   negative   form   of	  -funsigned-char.    Likewise,	  the	option
	   -fno-signed-char is equivalent to -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
	   These  options  control  whether a bit-field	is signed or unsigned,
	   when	the declaration	does not use either  "signed"  or  "unsigned".
	   By default, such a bit-field	is signed, because this	is consistent:
	   the basic integer types such	as "int" are signed types.

       -fsso-struct=endianness
	   Set	the  default  scalar storage order of structures and unions to
	   the specified endianness.   The  accepted  values  are  big-endian,
	   little-endian  and  native  for the native endianness of the	target
	   (the	default).  This	option is not supported	for C++.

	   Warning: the	-fsso-struct switch causes GCC to generate  code  that
	   is  not  binary  compatible	with  code generated without it	if the
	   specified endianness	is not the native endianness of	the target.

   Options Controlling C++ Dialect
       This  section  describes	 the  command-line  options  that   are	  only
       meaningful for C++ programs.  You can also use most of the GNU compiler
       options	regardless  of what language your program is in.  For example,
       you might compile a file	firstClass.C like this:

	       g++ -g -fstrict-enums -O	-c firstClass.C

       In this example,	only -fstrict-enums is an option meant	only  for  C++
       programs;  you can use the other	options	with any language supported by
       GCC.

       Some options for	compiling C programs, such as -std, are	also  relevant
       for C++ programs.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
	   Use version n of the	C++ ABI.  The default is version 0.

	   Version  0 refers to	the version conforming most closely to the C++
	   ABI specification.  Therefore, the ABI  obtained  using  version  0
	   will	change in different versions of	G++ as ABI bugs	are fixed.

	   Version  1 is the version of	the C++	ABI that first appeared	in G++
	   3.2.

	   Version 2 is	the version of the C++ ABI that	first appeared in  G++
	   3.4,	and was	the default through G++	4.9.

	   Version  3  corrects	 an  error in mangling a constant address as a
	   template argument.

	   Version 4, which first appeared in G++ 4.5, implements  a  standard
	   mangling for	vector types.

	   Version  5,	which first appeared in	G++ 4.6, corrects the mangling
	   of attribute	const/volatile on function pointer types, decltype  of
	   a plain decl, and use of a function parameter in the	declaration of
	   another parameter.

	   Version  6, which first appeared in G++ 4.7,	corrects the promotion
	   behavior of	C++11  scoped  enums  and  the	mangling  of  template
	   argument  packs,  const/static_cast,	 prefix	++ and --, and a class
	   scope function used as a template argument.

	   Version 7, which first appeared in G++ 4.8, that  treats  nullptr_t
	   as  a  builtin type and corrects the	mangling of lambdas in default
	   argument scope.

	   Version  8,	which  first  appeared	in  G++	 4.9,	corrects   the
	   substitution	  behavior   of	  function   types  with  function-cv-
	   qualifiers.

	   Version 9, which first appeared in G++ 5.2, corrects	the  alignment
	   of "nullptr_t".

	   Version  10,	 which	first  appeared	 in  G++ 6.1, adds mangling of
	   attributes  that  affect  type  identity,  such  as	ia32   calling
	   convention attributes (e.g. stdcall).

	   Version 11, which first appeared in G++ 7, corrects the mangling of
	   sizeof...  expressions  and	operator names.	 For multiple entities
	   with	the  same  name	 within	 a  function,  that  are  declared  in
	   different  scopes,  the  mangling  now  changes  starting  with the
	   twelfth occurrence.	It also	implies	-fnew-inheriting-ctors.

	   Version 12, which first appeared in G++  8,	corrects  the  calling
	   conventions	for empty classes on the x86_64	target and for classes
	   with	only deleted copy/move constructors.  It accidentally  changes
	   the	calling	convention for classes with a deleted copy constructor
	   and a trivial move constructor.

	   Version 13, which first appeared in G++ 8.2,	fixes  the  accidental
	   change in version 12.

	   Version  14,	 which first appeared in G++ 10, corrects the mangling
	   of the nullptr expression.

	   Version 15, which first appeared in G++ 11, changes the mangling of
	   "__alignof__" to be distinct	from that of "alignof",	and  dependent
	   operator names.

	   See also -Wabi.

       -fabi-compat-version=n
	   On  targets	that support strong aliases, G++ works around mangling
	   changes by creating an alias	with the  correct  mangled  name  when
	   defining  a	symbol	with  an  incorrect mangled name.  This	switch
	   specifies which ABI version to use for the alias.

	   With	-fabi-version=0	(the default), this  defaults  to  11  (GCC  7
	   compatibility).   If	 another  ABI  version is explicitly selected,
	   this	defaults to  0.	  For  compatibility  with  GCC	 versions  3.2
	   through 4.9,	use -fabi-compat-version=2.

	   If this option is not provided but -Wabi=n is, that version is used
	   for	compatibility  aliases.	 If this option	is provided along with
	   -Wabi (without the version),	the version from this option  is  used
	   for the warning.

       -fno-access-control
	   Turn	 off  all  access  checking.  This switch is mainly useful for
	   working around bugs in the access control code.

       -faligned-new
	   Enable support for C++17 "new" of types that	require	more alignment
	   than	 "void*	 ::operator  new(std::size_t)"	provides.   A  numeric
	   argument such as "-faligned-new=32" can be used to specify how much
	   alignment  (in  bytes)  is provided by that function, but few users
	   will	need to	override the default of	"alignof(std::max_align_t)".

	   This	flag is	enabled	by default for -std=c++17.

       -fchar8_t
       -fno-char8_t
	   Enable support for "char8_t"	as adopted for C++20.	This  includes
	   the	addition  of  a	new "char8_t" fundamental type,	changes	to the
	   types of UTF-8 string and character literals,  new  signatures  for
	   user-defined	literals, associated standard library updates, and new
	   "__cpp_char8_t" and "__cpp_lib_char8_t" feature test	macros.

	   This	 option	 enables  functions  to	be overloaded for ordinary and
	   UTF-8 strings:

		   int f(const char *);	   // #1
		   int f(const char8_t *); // #2
		   int v1 = f("text");	   // Calls #1
		   int v2 = f(u8"text");   // Calls #2

	   and introduces new signatures for user-defined literals:

		   int operator""_udl1(char8_t);
		   int v3 = u8'x'_udl1;
		   int operator""_udl2(const char8_t*, std::size_t);
		   int v4 = u8"text"_udl2;
		   template<typename T,	T...> int operator""_udl3();
		   int v5 = u8"text"_udl3;

	   The change to the types of  UTF-8  string  and  character  literals
	   introduces  incompatibilities  with	ISO C++11 and later standards.
	   For example,	the following code is well-formed under	ISO C++11, but
	   is ill-formed when -fchar8_t	is specified.

		   char	ca[] = u8"xx";	   // error: char-array	initialized from wide
					   //	     string
		   const char *cp = u8"xx";// error: invalid conversion	from
					   //	     `const char8_t*' to `const	char*'
		   int f(const char*);
		   auto	v = f(u8"xx");	   // error: invalid conversion	from
					   //	     `const char8_t*' to `const	char*'
		   std::string s{u8"xx"};  // error: no	matching function for call to
					   //	     `std::basic_string<char>::basic_string()'
		   using namespace std::literals;
		   s = u8"xx"s;		   // error: conversion	from
					   //	     `basic_string<char8_t>' to	non-scalar
					   //	     type `basic_string<char>' requested

       -fcheck-new
	   Check that the pointer  returned  by	 "operator  new"  is  non-null
	   before  attempting  to modify the storage allocated.	 This check is
	   normally  unnecessary  because  the	C++  standard  specifies  that
	   "operator new" only returns 0 if it is declared "throw()", in which
	   case	 the compiler always checks the	return value even without this
	   option.  In all other cases,	when "operator new"  has  a  non-empty
	   exception specification, memory exhaustion is signalled by throwing
	   "std::bad_alloc".  See also new (nothrow).

       -fconcepts
       -fconcepts-ts
	   Below -std=c++20, -fconcepts	enables	support	for the	C++ Extensions
	   for Concepts	Technical Specification, ISO 19217 (2015).

	   With	 -std=c++20  and  above,  Concepts  are	 part  of the language
	   standard,  so  -fconcepts  defaults	to  on.	  But	the   standard
	   specification  of  Concepts	differs	 significantly from the	TS, so
	   some	constructs that	were allowed in	the TS but didn't make it into
	   the standard	can still be enabled by	-fconcepts-ts.

       -fconstexpr-depth=n
	   Set	the  maximum  nested  evaluation  depth	 for  C++11  constexpr
	   functions  to  n.   A  limit	 is needed to detect endless recursion
	   during constant expression evaluation.  The	minimum	 specified  by
	   the standard	is 512.

       -fconstexpr-cache-depth=n
	   Set	the  maximum  level  of	 nested	 evaluation  depth  for	 C++11
	   constexpr functions that will be cached to n.  This is a  heuristic
	   that	 trades	 off compilation speed (when the cache avoids repeated
	   calculations) against memory	consumption (when the cache grows very
	   large from highly recursive evaluations).  The default is 8.	  Very
	   few	users  are  likely to want to adjust it, but if	your code does
	   heavy constexpr calculations	you might want to experiment  to  find
	   which value works best for you.

       -fconstexpr-loop-limit=n
	   Set	the maximum number of iterations for a loop in C++14 constexpr
	   functions to	n.  A limit is needed to detect	infinite loops	during
	   constant expression evaluation.  The	default	is 262144 (1<<18).

       -fconstexpr-ops-limit=n
	   Set	the  maximum  number  of  operations during a single constexpr
	   evaluation.	Even when number of iterations of  a  single  loop  is
	   limited with	the above limit, if there are several nested loops and
	   each	 of  them has many iterations but still	smaller	than the above
	   limit, or if	in a body of some loop or even outside of a  loop  too
	   many	 expressions  need  to	be  evaluated, the resulting constexpr
	   evaluation might take too long.  The	default	is 33554432 (1<<25).

       -fcoroutines
	   Enable support for the C++ coroutines extension (experimental).

       -fno-elide-constructors
	   The C++ standard  allows  an	 implementation	 to  omit  creating  a
	   temporary  that  is	only  used to initialize another object	of the
	   same	type.  Specifying this option disables that optimization,  and
	   forces  G++ to call the copy	constructor in all cases.  This	option
	   also	causes G++ to call trivial member  functions  which  otherwise
	   would be expanded inline.

	   In  C++17,  the compiler is required	to omit	these temporaries, but
	   this	option still affects trivial member functions.

       -fno-enforce-eh-specs
	   Don't  generate  code  to  check   for   violation	of   exception
	   specifications at run time.	This option violates the C++ standard,
	   but may be useful for reducing code size in production builds, much
	   like	defining "NDEBUG".  This does not give user code permission to
	   throw  exceptions in	violation of the exception specifications; the
	   compiler still optimizes based on the specifications,  so  throwing
	   an unexpected exception results in undefined	behavior at run	time.

       -fextern-tls-init
       -fno-extern-tls-init
	   The	 C++11	 and   OpenMP	standards   allow  "thread_local"  and
	   "threadprivate" variables to	have dynamic (runtime) initialization.
	   To support this, any	use of such a variable goes through a  wrapper
	   function  that performs any necessary initialization.  When the use
	   and definition of the variable are in the  same  translation	 unit,
	   this	 overhead  can	be  optimized  away,  but when the use is in a
	   different translation unit there is significant  overhead  even  if
	   the	variable doesn't actually need dynamic initialization.	If the
	   programmer can be sure that no  use	of  the	 variable  in  a  non-
	   defining TU needs to	trigger	dynamic	initialization (either because
	   the variable	is statically initialized, or a	use of the variable in
	   the	defining  TU  will be executed before any uses in another TU),
	   they	can avoid this overhead	with the -fno-extern-tls-init option.

	   On  targets	that  support	symbol	 aliases,   the	  default   is
	   -fextern-tls-init.	On targets that	do not support symbol aliases,
	   the default is -fno-extern-tls-init.

       -fno-gnu-keywords
	   Do not recognize "typeof" as	a keyword, so that code	can  use  this
	   word	 as  an	 identifier.   You  can	 use  the keyword "__typeof__"
	   instead.  This option is implied by the strict  ISO	C++  dialects:
	   -ansi, -std=c++98, -std=c++11, etc.

       -fno-implicit-templates
	   Never  emit	code  for  non-inline  templates that are instantiated
	   implicitly  (i.e.  by   use);   only	  emit	 code	for   explicit
	   instantiations.   If	 you  use  this	 option, you must take care to
	   structure  your  code  to  include  all  the	  necessary   explicit
	   instantiations to avoid getting undefined symbols at	link time.

       -fno-implicit-inline-templates
	   Don't  emit	code  for implicit instantiations of inline templates,
	   either.  The	default	is  to	handle	inlines	 differently  so  that
	   compiles  with  and	without	 optimization  need  the  same	set of
	   explicit instantiations.

       -fno-implement-inlines
	   To save space, do not emit out-of-line copies of  inline  functions
	   controlled  by "#pragma implementation".  This causes linker	errors
	   if these functions are not inlined everywhere they are called.

       -fmodules-ts
       -fno-modules-ts
	   Enable support for C++20 modules   The -fno-modules-ts  is  usually
	   not	needed,	 as  that is the default.  Even	though this is a C++20
	   feature, it is not currently	implicitly enabled by  selecting  that
	   standard version.

       -fmodule-header
       -fmodule-header=user
       -fmodule-header=system
	   Compile a header file to create an importable header	unit.

       -fmodule-implicit-inline
	   Member  functions  defined  in  their  class	 definitions  are  not
	   implicitly  inline  for  modular  code.   This  is	different   to
	   traditional C++ behavior, for good reasons.	However, it may	result
	   in  a  difficulty  during  code  porting.   This  option makes such
	   function definitions	implicitly inline.  It does  however  generate
	   an  ABI  incompatibility, so	you must use it	everywhere or nowhere.
	   (Such definitions outside  of  a  named  module  remain  implicitly
	   inline, regardless.)

       -fno-module-lazy
	   Disable lazy	module importing and module mapper creation.

       -fmodule-mapper=[hostname]:port[?ident]
       -fmodule-mapper=|program[?ident]	args...
       -fmodule-mapper==socket[?ident]
       -fmodule-mapper=<>[inout][?ident]
       -fmodule-mapper=<in>out[?ident]
       -fmodule-mapper=file[?ident]
	   An  oracle  to  query  for  module  name  to	filename mappings.  If
	   unspecified the CXX_MODULE_MAPPER environment variable is used, and
	   if that is unset, an	in-process default is provided.

       -fmodule-only
	   Only	emit the Compiled  Module  Interface,  inhibiting  any	object
	   file.

       -fms-extensions
	   Disable  Wpedantic  warnings	 about constructs used in MFC, such as
	   implicit int	and getting a pointer  to  member  function  via  non-
	   standard syntax.

       -fnew-inheriting-ctors
	   Enable  the	P0136 adjustment to the	semantics of C++11 constructor
	   inheritance.	 This is part of C++17 but also	 considered  to	 be  a
	   Defect  Report  against  C++11  and C++14.  This flag is enabled by
	   default unless -fabi-version=10 or lower is specified.

       -fnew-ttp-matching
	   Enable the P0522 resolution to Core issue  150,  template  template
	   parameters  and  default  arguments:	 this  allows  a template with
	   default template arguments as an argument for a  template  template
	   parameter  with fewer template parameters.  This flag is enabled by
	   default for -std=c++17.

       -fno-nonansi-builtins
	   Disable built-in declarations of functions that are not mandated by
	   ANSI/ISO C.	 These	include	 "ffs",	 "alloca",  "_exit",  "index",
	   "bzero", "conjf", and other related functions.

       -fnothrow-opt
	   Treat   a  "throw()"	 exception  specification  as  if  it  were  a
	   "noexcept" specification to	reduce	or  eliminate  the  text  size
	   overhead  relative  to  a function with no exception	specification.
	   If the function has	local  variables  of  types  with  non-trivial
	   destructors,	  the	exception  specification  actually  makes  the
	   function smaller because the	EH cleanups for	those variables	can be
	   optimized away.  The	semantic effect	is that	 an  exception	thrown
	   out of a function with such an exception specification results in a
	   call	to "terminate" rather than "unexpected".

       -fno-operator-names
	   Do  not  treat the operator name keywords "and", "bitand", "bitor",
	   "compl", "not", "or"	and "xor" as synonyms as keywords.

       -fno-optional-diags
	   Disable diagnostics that the	standard says a	compiler does not need
	   to issue.  Currently, the only such diagnostic issued by G++	is the
	   one for a name having multiple meanings within a class.

       -fpermissive
	   Downgrade some diagnostics about nonconformant code from errors  to
	   warnings.   Thus, using -fpermissive	allows some nonconforming code
	   to compile.

       -fno-pretty-templates
	   When	an error message refers	to  a  specialization  of  a  function
	   template,  the  compiler  normally  prints  the  signature  of  the
	   template followed by	the template arguments	and  any  typedefs  or
	   typenames  in the signature (e.g. "void f(T)	[with T	= int]"	rather
	   than	"void f(int)") so that it's clear which	template is  involved.
	   When	 an  error  message  refers  to	 a  specialization  of a class
	   template, the compiler omits	any template arguments that match  the
	   default  template  arguments	for that template.  If either of these
	   behaviors make it harder to understand  the	error  message	rather
	   than	easier,	you can	use -fno-pretty-templates to disable them.

       -fno-rtti
	   Disable  generation	of  information	about every class with virtual
	   functions for use by	the C++	run-time type identification  features
	   ("dynamic_cast" and "typeid").  If you don't	use those parts	of the
	   language,  you  can	save some space	by using this flag.  Note that
	   exception handling uses the same information, but G++ generates  it
	   as  needed. The "dynamic_cast" operator can still be	used for casts
	   that	do not require run-time	type information, i.e. casts to	 "void
	   *" or to unambiguous	base classes.

	   Mixing  code	compiled with -frtti with that compiled	with -fno-rtti
	   may not work.  For example, programs	may fail to link  if  a	 class
	   compiled with -fno-rtti is used as a	base for a class compiled with
	   -frtti.

       -fsized-deallocation
	   Enable the built-in global declarations

		   void	operator delete	(void *, std::size_t) noexcept;
		   void	operator delete[] (void	*, std::size_t)	noexcept;

	   as	introduced   in	  C++14.   This	 is  useful  for  user-defined
	   replacement deallocation functions that, for	example, use the  size
	   of  the  object  to	make  deallocation faster.  Enabled by default
	   under -std=c++14 and	above.	The  flag  -Wsized-deallocation	 warns
	   about places	that might want	to add a definition.

       -fstrict-enums
	   Allow the compiler to optimize using	the assumption that a value of
	   enumerated  type  can  only be one of the values of the enumeration
	   (as defined in the C++ standard; basically, a  value	 that  can  be
	   represented	in  the	minimum	number of bits needed to represent all
	   the enumerators).  This assumption may not be valid if the  program
	   uses	a cast to convert an arbitrary integer value to	the enumerated
	   type.

       -fstrong-eval-order
	   Evaluate  member  access, array subscripting, and shift expressions
	   in left-to-right order, and evaluate	 assignment  in	 right-to-left
	   order,  as  adopted for C++17.  Enabled by default with -std=c++17.
	   -fstrong-eval-order=some enables just the ordering of member	access
	   and shift expressions, and is the default without -std=c++17.

       -ftemplate-backtrace-limit=n
	   Set the maximum number of template instantiation notes for a	single
	   warning or error to n.  The default value is	10.

       -ftemplate-depth=n
	   Set the maximum instantiation depth for template classes to	n.   A
	   limit  on  the  template  instantiation  depth  is needed to	detect
	   endless recursions during template class  instantiation.   ANSI/ISO
	   C++	conforming  programs  must not rely on a maximum depth greater
	   than	17 (changed to 1024 in C++11).	The default value is  900,  as
	   the compiler	can run	out of stack space before hitting 1024 in some
	   situations.

       -fno-threadsafe-statics
	   Do not emit the extra code to use the routines specified in the C++
	   ABI	for  thread-safe initialization	of local statics.  You can use
	   this	option to reduce code size slightly in code that doesn't  need
	   to be thread-safe.

       -fuse-cxa-atexit
	   Register  destructors for objects with static storage duration with
	   the "__cxa_atexit" function	rather	than  the  "atexit"  function.
	   This	 option	 is required for fully standards-compliant handling of
	   static destructors, but only	 works	if  your  C  library  supports
	   "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
	   Don't  use  the  "__cxa_get_exception_ptr"  runtime	routine.  This
	   causes "std::uncaught_exception" to be incorrect, but is  necessary
	   if the runtime routine is not available.

       -fvisibility-inlines-hidden
	   This	 switch	 declares  that	 the  user does	not attempt to compare
	   pointers to inline functions	or methods where the addresses of  the
	   two functions are taken in different	shared objects.

	   The	effect	of  this  is  that  GCC	 may, effectively, mark	inline
	   methods with	"__attribute__ ((visibility ("hidden")))" so that they
	   do not appear in the	export table of	a DSO and do not require a PLT
	   indirection when used within	the DSO.   Enabling  this  option  can
	   have	 a  dramatic  effect  on  load	and  link times	of a DSO as it
	   massively reduces the size of the dynamic  export  table  when  the
	   library makes heavy use of templates.

	   The	behavior  of  this switch is not quite the same	as marking the
	   methods as hidden directly,	because	 it  does  not	affect	static
	   variables  local  to	 the  function or cause	the compiler to	deduce
	   that	the function is	defined	in only	one shared object.

	   You may mark	a method as having a visibility	explicitly  to	negate
	   the	effect	of the switch for that method.	For example, if	you do
	   want	to compare pointers to a particular inline method,  you	 might
	   mark	 it as having default visibility.  Marking the enclosing class
	   with	explicit visibility has	no effect.

	   Explicitly instantiated  inline  methods  are  unaffected  by  this
	   option  as  their  linkage  might  otherwise	cross a	shared library
	   boundary.

       -fvisibility-ms-compat
	   This	flag attempts to use visibility	settings  to  make  GCC's  C++
	   linkage model compatible with that of Microsoft Visual Studio.

	   The flag makes these	changes	to GCC's linkage model:

	   1.  It    sets   the	  default   visibility	 to   "hidden",	  like
	       -fvisibility=hidden.

	   2.  Types, but not their members, are not hidden by default.

	   3.  The One Definition Rule is relaxed for types  without  explicit
	       visibility  specifications  that	 are  defined in more than one
	       shared object: those declarations are  permitted	 if  they  are
	       permitted when this option is not used.

	   In  new  code  it  is  better to use	-fvisibility=hidden and	export
	   those  classes  that	 are  intended	to  be	 externally   visible.
	   Unfortunately   it	is   possible	for   code  to	rely,  perhaps
	   accidentally, on the	Visual Studio behavior.

	   Among the consequences  of  these  changes  are  that  static  data
	   members  of	the  same  type	 with  the  same  name	but defined in
	   different shared objects are	different, so changing	one  does  not
	   change  the other; and that pointers	to function members defined in
	   different shared objects may	not compare equal.  When this flag  is
	   given,  it  is a violation of the ODR to define types with the same
	   name	differently.

       -fno-weak
	   Do not use weak symbol support, even	 if  it	 is  provided  by  the
	   linker.   By	 default, G++ uses weak	symbols	if they	are available.
	   This	option exists only for testing,	and should not be used by end-
	   users; it results in	inferior  code	and  has  no  benefits.	  This
	   option may be removed in a future release of	G++.

       -fext-numeric-literals (C++ and Objective-C++ only)
	   Accept  imaginary,  fixed-point,  or	machine-defined	literal	number
	   suffixes as GNU extensions.	When this option is turned  off	 these
	   suffixes   are   treated  as	 C++11	user-defined  literal  numeric
	   suffixes.  This is on by default for	all pre-C++11 dialects and all
	   GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++14.
	   This	option is off by default for ISO  C++11	 onwards  (-std=c++11,
	   ...).

       -nostdinc++
	   Do not search for header files in the standard directories specific
	   to  C++, but	do still search	the other standard directories.	 (This
	   option is used when building	the C++	library.)

       -flang-info-include-translate
       -flang-info-include-translate-not
       -flang-info-include-translate=header
	   Inform of include translation events.  The first will note accepted
	   include  translations,  the	second	will  note  declined   include
	   translations.   The header form will	inform of include translations
	   relating to that specific header.  If header	is of the form	"user"
	   or  "<system>"  it  will  be	 resolved to a specific	user or	system
	   header using	the include path.

       -flang-info-module-cmi
       -flang-info-module-cmi=module
	   Inform of Compiled Module Interface pathnames.  The first will note
	   all read CMI	 pathnames.   The  module  form	 will  not  reading  a
	   specific  module's  CMI.  module may	be a named module or a header-
	   unit	(the latter indicated by either	being  a  pathname  containing
	   directory separators	or enclosed in "<>" or "").

       -stdlib=libstdc++,libc++
	   When	  G++	is  configured	to  support  this  option,  it	allows
	   specification of alternate C++ runtime libraries.  Two options  are
	   available:  libstdc++ (the default, native C++ runtime for G++) and
	   libc++ which	is the C++ runtime installed on	some operating systems
	   (e.g. Darwin	versions from Darwin11 onwards).  The option  switches
	   G++	to  use	 the  headers  from  the specified library and to emit
	   "-lstdc++" or "-lc++" respectively, when a C++ runtime is  required
	   for linking.

       In addition, these warning options have meanings	only for C++ programs:

       -Wabi-tag (C++ and Objective-C++	only)
	   Warn	when a type with an ABI	tag is used in a context that does not
	   have	 that  ABI tag.	 See C++ Attributes for	more information about
	   ABI tags.

       -Wcomma-subscript (C++ and Objective-C++	only)
	   Warn	about  uses  of	 a  comma  expression  within  a  subscripting
	   expression.	 This usage was	deprecated in C++20.  However, a comma
	   expression wrapped in "( )" is not deprecated.  Example:

		   void	f(int *a, int b, int c)	{
		       a[b,c];	   // deprecated
		       a[(b,c)];   // OK
		   }

	   Enabled by default with -std=c++20.

       -Wctad-maybe-unsupported	(C++ and Objective-C++ only)
	   Warn	when performing	class template argument	deduction (CTAD) on  a
	   type	 with  no  explicitly  written deduction guides.  This warning
	   will	point out cases	where CTAD succeeded only because the compiler
	   synthesized the implicit deduction guides, which might not be  what
	   the	programmer  intended.  Certain style guides allow CTAD only on
	   types that specifically "opt-in"; i.e., on types that are  designed
	   to support CTAD.  This warning can be suppressed with the following
	   pattern:

		   struct allow_ctad_t;	// any name works
		   template <typename T> struct	S {
		     S(T) { }
		   };
		   S(allow_ctad_t) -> S<void>; // guide	with incomplete	parameter type will never be considered

       -Wctor-dtor-privacy (C++	and Objective-C++ only)
	   Warn	 when  a  class	seems unusable because all the constructors or
	   destructors in that class are private, and it has  neither  friends
	   nor public static member functions.	Also warn if there are no non-
	   private  methods,  and there's at least one private member function
	   that	isn't a	constructor or destructor.

       -Wdelete-non-virtual-dtor (C++ and Objective-C++	only)
	   Warn	when "delete" is used to destroy an instance of	a  class  that
	   has	virtual	 functions and non-virtual destructor. It is unsafe to
	   delete an instance of a derived class through a pointer to  a  base
	   class  if  the base class does not have a virtual destructor.  This
	   warning is enabled by -Wall.

       -Wdeprecated-copy (C++ and Objective-C++	only)
	   Warn	that the implicit declaration of a copy	 constructor  or  copy
	   assignment  operator	is deprecated if the class has a user-provided
	   copy	constructor or copy assignment	operator,  in  C++11  and  up.
	   This	 warning  is enabled by	-Wextra.  With -Wdeprecated-copy-dtor,
	   also	deprecate if the class has a user-provided destructor.

       -Wno-deprecated-enum-enum-conversion (C++ and Objective-C++ only)
	   Disable the warning	about  the  case  when	the  usual  arithmetic
	   conversions	are  applied  on  operands where one is	of enumeration
	   type	and the	other  is  of  a  different  enumeration  type.	  This
	   conversion was deprecated in	C++20.	For example:

		   enum	E1 { e };
		   enum	E2 { f };
		   int k = f - e;

	   -Wdeprecated-enum-enum-conversion   is   enabled  by	 default  with
	   -std=c++20.	In pre-C++20 dialects, this warning can	be enabled  by
	   -Wenum-conversion.

       -Wno-deprecated-enum-float-conversion (C++ and Objective-C++ only)
	   Disable  the	 warning  about	 the  case  when  the usual arithmetic
	   conversions are applied on operands where  one  is  of  enumeration
	   type	 and  the  other is of a floating-point	type.  This conversion
	   was deprecated in C++20.  For example:

		   enum	E1 { e };
		   enum	E2 { f };
		   bool	b = e <= 3.7;

	   -Wdeprecated-enum-float-conversion  is  enabled  by	default	  with
	   -std=c++20.	 In pre-C++20 dialects,	this warning can be enabled by
	   -Wenum-conversion.

       -Wno-init-list-lifetime (C++ and	Objective-C++ only)
	   Do not warn about uses of "std::initializer_list" that  are	likely
	   to  result in dangling pointers.  Since the underlying array	for an
	   "initializer_list" is handled like a	normal C++  temporary  object,
	   it  is  easy	 to inadvertently keep a pointer to the	array past the
	   end of the array's lifetime.	 For example:

	   *   If a function returns  a	 temporary  "initializer_list",	 or  a
	       local "initializer_list"	variable, the array's lifetime ends at
	       the  end	 of  the return	statement, so the value	returned has a
	       dangling	pointer.

	   *   If a new-expression creates an  "initializer_list",  the	 array
	       only  lives  until the end of the enclosing full-expression, so
	       the "initializer_list" in the heap has a	dangling pointer.

	   *   When an "initializer_list" variable is assigned from  a	brace-
	       enclosed	 initializer list, the temporary array created for the
	       right side of the assignment only lives until the  end  of  the
	       full-expression,	   so	 at    the    next    statement	   the
	       "initializer_list" variable has a dangling pointer.

		       // li's initial underlying array	lives as long as li
		       std::initializer_list<int> li = { 1,2,3 };
		       // assignment changes li	to point to a temporary	array
		       li = { 4, 5 };
		       // now the temporary is gone and	li has a dangling pointer
		       int i = li.begin()[0] //	undefined behavior

	   *   When a list constructor stores the  "begin"  pointer  from  the
	       "initializer_list"  argument,  this doesn't extend the lifetime
	       of the array, so	if a class  variable  is  constructed  from  a
	       temporary  "initializer_list",  the pointer is left dangling by
	       the end of the variable declaration statement.

       -Winvalid-imported-macros
	   Verify all imported macro definitions  are  valid  at  the  end  of
	   compilation.	  This	is  not	 enabled  by  default,	as it requires
	   additional  processing  to  determine.   It	may  be	 useful	  when
	   preparing sets of header-units to ensure consistent macros.

       -Wno-literal-suffix (C++	and Objective-C++ only)
	   Do not warn when a string or	character literal is followed by a ud-
	   suffix  which  does	not begin with an underscore.  As a conforming
	   extension, GCC  treats  such	 suffixes  as  separate	 preprocessing
	   tokens  in order to maintain	backwards compatibility	with code that
	   uses	formatting macros from "<inttypes.h>".	For example:

		   #define __STDC_FORMAT_MACROS
		   #include <inttypes.h>
		   #include <stdio.h>

		   int main() {
		     int64_t i64 = 123;
		     printf("My	int64: %" PRId64"\n", i64);
		   }

	   In this case, "PRId64"  is  treated	as  a  separate	 preprocessing
	   token.

	   This	 option	 also  controls	 warnings  when	a user-defined literal
	   operator is declared	with a literal suffix identifier that  doesn't
	   begin  with	an  underscore.	 Literal suffix	identifiers that don't
	   begin with an underscore are	reserved for future standardization.

	   These warnings are enabled by default.

       -Wno-narrowing (C++ and Objective-C++ only)
	   For C++11 and later standards, narrowing conversions	are  diagnosed
	   by  default,	 as  required by the standard.	A narrowing conversion
	   from	a constant produces an error, and a narrowing conversion  from
	   a  non-constant  produces  a	warning, but -Wno-narrowing suppresses
	   the diagnostic.  Note that this does	 not  affect  the  meaning  of
	   well-formed	code;  narrowing conversions are still considered ill-
	   formed in SFINAE contexts.

	   With	 -Wnarrowing  in  C++98,  warn	when  a	 narrowing  conversion
	   prohibited by C++11 occurs within { }, e.g.

		   int i = { 2.2 }; // error: narrowing	from double to int

	   This	flag is	included in -Wall and -Wc++11-compat.

       -Wnoexcept (C++ and Objective-C++ only)
	   Warn	 when  a  noexcept-expression  evaluates to false because of a
	   call	to a function that does	 not  have  a  non-throwing  exception
	   specification  (i.e.	 "throw()"  or "noexcept") but is known	by the
	   compiler to never throw an exception.

       -Wnoexcept-type (C++ and	Objective-C++ only)
	   Warn	if the C++17 feature making "noexcept" part of a function type
	   changes the mangled name of a symbol	relative to C++14.  Enabled by
	   -Wabi and -Wc++17-compat.

	   As an example:

		   template <class T> void f(T t) { t(); };
		   void	g() noexcept;
		   void	h() { f(g); }

	   In  C++14,  "f"  calls  "f<void(*)()>",  but	 in  C++17  it	 calls
	   "f<void(*)()noexcept>".

       -Wclass-memaccess (C++ and Objective-C++	only)
	   Warn	 when  the destination of a call to a raw memory function such
	   as "memset" or "memcpy" is  an  object  of  class  type,  and  when
	   writing  into  such an object might bypass the class	non-trivial or
	   deleted constructor or copy assignment,  violate  const-correctness
	   or encapsulation, or	corrupt	virtual	table pointers.	 Modifying the
	   representation of such objects may violate invariants maintained by
	   member  functions  of the class.  For example, the call to "memset"
	   below is undefined because it modifies a non-trivial	 class	object
	   and is, therefore, diagnosed.  The safe way to either initialize or
	   clear  the  storage	of  objects  of	 such  types  is  by using the
	   appropriate	constructor  or	 assignment  operator,	 if   one   is
	   available.

		   std::string str = "abc";
		   memset (&str, 0, sizeof str);

	   The	-Wclass-memaccess  option  is  enabled	by  -Wall.  Explicitly
	   casting the pointer to the class object to "void *" or  to  a  type
	   that	 can  be safely	accessed by the	raw memory function suppresses
	   the warning.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
	   Warn	when a class has virtual  functions  and  an  accessible  non-
	   virtual  destructor	itself	or  in	an accessible polymorphic base
	   class, in which case	 it  is	 possible  but	unsafe	to  delete  an
	   instance  of	 a derived class through a pointer to the class	itself
	   or base class.  This	warning	is automatically enabled  if  -Weffc++
	   is specified.

       -Wregister (C++ and Objective-C++ only)
	   Warn	on uses	of the "register" storage class	specifier, except when
	   it  is  part	of the GNU Explicit Register Variables extension.  The
	   use of the "register" keyword as storage class specifier  has  been
	   deprecated  in C++11	and removed in C++17.  Enabled by default with
	   -std=c++17.

       -Wreorder (C++ and Objective-C++	only)
	   Warn	when the order of member initializers given in the  code  does
	   not match the order in which	they must be executed.	For instance:

		   struct A {
		     int i;
		     int j;
		     A(): j (0), i (1) { }
		   };

	   The	compiler rearranges the	member initializers for	"i" and	"j" to
	   match the declaration order of the members, emitting	a  warning  to
	   that	effect.	 This warning is enabled by -Wall.

       -Wno-pessimizing-move (C++ and Objective-C++ only)
	   This	 warning  warns	 when  a  call	to  "std::move"	 prevents copy
	   elision.  A typical scenario	when copy elision can  occur  is  when
	   returning  in  a  function  with  a	class  return  type,  when the
	   expression being returned is	the name of a  non-volatile  automatic
	   object,  and	 is not	a function parameter, and has the same type as
	   the function	return type.

		   struct T {
		   ...
		   };
		   T fn()
		   {
		     T t;
		     ...
		     return std::move (t);
		   }

	   But in this example,	the "std::move"	call prevents copy elision.

	   This	warning	is enabled by -Wall.

       -Wno-redundant-move (C++	and Objective-C++ only)
	   This	warning	warns about redundant calls to "std::move";  that  is,
	   when	 a  move  operation would have been performed even without the
	   "std::move" call.  This happens because the compiler	is  forced  to
	   treat the object as if it were an rvalue in certain situations such
	   as returning	a local	variable, where	copy elision isn't applicable.
	   Consider:

		   struct T {
		   ...
		   };
		   T fn(T t)
		   {
		     ...
		     return std::move (t);
		   }

	   Here,  the  "std::move"  call is redundant.	Because	G++ implements
	   Core	Issue 1579, another example is:

		   struct T { // convertible to	U
		   ...
		   };
		   struct U {
		   ...
		   };
		   U fn()
		   {
		     T t;
		     ...
		     return std::move (t);
		   }

	   In this example, copy elision isn't applicable because the type  of
	   the	expression being returned and the function return type differ,
	   yet G++ treats the return value as if  it  were  designated	by  an
	   rvalue.

	   This	warning	is enabled by -Wextra.

       -Wrange-loop-construct (C++ and Objective-C++ only)
	   This	 warning  warns	when a C++ range-based for-loop	is creating an
	   unnecessary copy.  This can happen when the	range  declaration  is
	   not a reference, but	probably should	be.  For example:

		   struct S { char arr[128]; };
		   void	fn () {
		     S arr[5];
		     for (const	auto x : arr) {	... }
		   }

	   It does not warn when the type being	copied is a trivially-copyable
	   type	whose size is less than	64 bytes.

	   This	 warning also warns when a loop	variable in a range-based for-
	   loop	is initialized with a value of a different type	resulting in a
	   copy.  For example:

		   void	fn() {
		     int arr[10];
		     for (const	double &x : arr) { ... }
		   }

	   In the example above, in every iteration of the  loop  a  temporary
	   value  of  type  "double"  is  created  and destroyed, to which the
	   reference "const double &" is bound.

	   This	warning	is enabled by -Wall.

       -Wredundant-tags	(C++ and Objective-C++ only)
	   Warn	about redundant	class-key and enum-key in references to	 class
	   types  and  enumerated  types  in  contexts	where  the  key	can be
	   eliminated without causing an ambiguity.  For example:

		   struct foo;
		   struct foo *p;   // warn that keyword struct	can be eliminated

	   On the other	hand, in this example there is no warning:

		   struct foo;
		   void	foo ();	  // "hides" struct foo
		   void	bar (struct foo&);  // no warning, keyword struct is necessary

       -Wno-subobject-linkage (C++ and Objective-C++ only)
	   Do not warn if a class type has a base or a field whose  type  uses
	   the anonymous namespace or depends on a type	with no	linkage.  If a
	   type	A depends on a type B with no or internal linkage, defining it
	   in multiple translation units would be an ODR violation because the
	   meaning  of	B  is  different  in each translation unit.  If	A only
	   appears in a	single translation unit, the best way to  silence  the
	   warning  is	to  give  it  internal	linkage	 by  putting  it in an
	   anonymous namespace	as  well.   The	 compiler  doesn't  give  this
	   warning  for	 types	defined	 in  the  main	.C  file, as those are
	   unlikely to	have  multiple	definitions.   -Wsubobject-linkage  is
	   enabled by default.

       -Weffc++	(C++ and Objective-C++ only)
	   Warn	 about violations of the following style guidelines from Scott
	   Meyers' Effective C++ series	of books:

	   *   Define a	 copy  constructor  and	 an  assignment	 operator  for
	       classes with dynamically-allocated memory.

	   *   Prefer initialization to	assignment in constructors.

	   *   Have "operator="	return a reference to *this.

	   *   Don't try to return a reference when you	must return an object.

	   *   Distinguish  between  prefix and	postfix	forms of increment and
	       decrement operators.

	   *   Never overload "&&", "||", or ",".

	   This	option also enables -Wnon-virtual-dtor,	which is also  one  of
	   the	effective C++ recommendations.	However, the check is extended
	   to warn about the lack of virtual  destructor  in  accessible  non-
	   polymorphic bases classes too.

	   When	 selecting  this  option,  be  aware that the standard library
	   headers do not obey all of these guidelines;	use grep -v to	filter
	   out those warnings.

       -Wno-exceptions (C++ and	Objective-C++ only)
	   Disable  the	 warning  about	 the case when an exception handler is
	   shadowed by another handler,	which can point	out a  wrong  ordering
	   of exception	handlers.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
	   Warn	 about	the  use  of  an  uncasted  "NULL"  as sentinel.  When
	   compiling only with GCC this	is a  valid  sentinel,	as  "NULL"  is
	   defined to "__null".	 Although it is	a null pointer constant	rather
	   than	 a  null pointer, it is	guaranteed to be of the	same size as a
	   pointer.  But this use is not portable across different compilers.

       -Wno-non-template-friend	(C++ and Objective-C++ only)
	   Disable warnings when non-template friend  functions	 are  declared
	   within  a  template.	  In  very  old	 versions  of GCC that predate
	   implementation of the ISO standard, declarations such as friend int
	   foo(int), where the name of the friend is an	unqualified-id,	 could
	   be  interpreted  as	a  particular  specialization  of  a  template
	   function; the warning exists	to  diagnose  compatibility  problems,
	   and is enabled by default.

       -Wold-style-cast	(C++ and Objective-C++ only)
	   Warn	 if  an	 old-style  (C-style)  cast to a non-void type is used
	   within  a  C++  program.   The  new-style  casts   ("dynamic_cast",
	   "static_cast",   "reinterpret_cast",	 and  "const_cast")  are  less
	   vulnerable to unintended effects and	much easier to search for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
	   Warn	when a function	declaration hides  virtual  functions  from  a
	   base	class.	For example, in:

		   struct A {
		     virtual void f();
		   };

		   struct B: public A {
		     void f(int);
		   };

	   the "A" class version of "f"	is hidden in "B", and code like:

		   B* b;
		   b->f();

	   fails to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
	   Disable  the	 diagnostic  for  converting a bound pointer to	member
	   function to a plain pointer.

       -Wsign-promo (C++ and Objective-C++ only)
	   Warn	when overload resolution chooses a promotion from unsigned  or
	   enumerated  type to a signed	type, over a conversion	to an unsigned
	   type	of the same size.  Previous versions of	G++ tried to  preserve
	   unsignedness, but the standard mandates the current behavior.

       -Wtemplates (C++	and Objective-C++ only)
	   Warn	 when  a  primary  template  declaration is encountered.  Some
	   coding rules	disallow templates, and	this may be  used  to  enforce
	   that	 rule.	 The  warning is inactive inside a system header file,
	   such	as the STL, so one can	still  use  the	 STL.	One  may  also
	   instantiate or specialize templates.

       -Wno-mismatched-new-delete (C++ and Objective-C++ only)
	   Warn	 for  mismatches  between calls	to "operator new" or "operator
	   delete"  and	 the  corresponding  call   to	 the   allocation   or
	   deallocation	 function.  This includes invocations of C++ "operator
	   delete" with	pointers returned  from	 either	 mismatched  forms  of
	   "operator  new",  or	from other functions that allocate objects for
	   which the "operator delete" isn't a suitable	deallocator,  as  well
	   as  calls  to  other	 deallocation functions	with pointers returned
	   from	"operator new"	for  which  the	 deallocation  function	 isn't
	   suitable.

	   For	example,  the  "delete"	 expression  in	 the function below is
	   diagnosed because it	doesn't	match the  array  form	of  the	 "new"
	   expression  the pointer argument was	returned from.	Similarly, the
	   call	to "free" is also diagnosed.

		   void	f ()
		   {
		     int *a = new int[n];
		     delete a;	 // warning: mismatch in array forms of	expressions

		     char *p = new char[n];
		     free (p);	 // warning: mismatch between new and free
		   }

	   The	related	 option	 -Wmismatched-dealloc	diagnoses   mismatches
	   involving   allocation   and	  deallocation	functions  other  than
	   "operator new" and "operator	delete".

	   -Wmismatched-new-delete is enabled by default.

       -Wmismatched-tags (C++ and Objective-C++	only)
	   Warn	for declarations of structs, classes, and class	templates  and
	   their  specializations  with	a class-key that does not match	either
	   the definition  or  the  first  declaration	if  no	definition  is
	   provided.

	   For	example,  the  declaration  of "struct Object" in the argument
	   list	of "draw" triggers the warning.	 To avoid  it,	either	remove
	   the	redundant  class-key  "struct"	or  replace it with "class" to
	   match its definition.

		   class Object	{
		   public:
		     virtual ~Object ()	= 0;
		   };
		   void	draw (struct Object*);

	   It is not wrong to declare a	class with the class-key  "struct"  as
	   the	example	above shows.  The -Wmismatched-tags option is intended
	   to help achieve a consistent	style of class declarations.  In  code
	   that	 is  intended  to  be  portable	to Windows-based compilers the
	   warning helps prevent unresolved references due to  the  difference
	   in the mangling of symbols declared with different class-keys.  The
	   option  can	be  used  either  on  its  own	or in conjunction with
	   -Wredundant-tags.

       -Wmultiple-inheritance (C++ and Objective-C++ only)
	   Warn	when a class is	defined	with  multiple	direct	base  classes.
	   Some	 coding	 rules	disallow multiple inheritance, and this	may be
	   used	to enforce that	rule.  The warning is inactive inside a	system
	   header file,	such as	the STL, so one	can still use  the  STL.   One
	   may also define classes that	indirectly use multiple	inheritance.

       -Wvirtual-inheritance
	   Warn	 when  a  class	 is  defined with a virtual direct base	class.
	   Some	coding rules disallow multiple inheritance, and	 this  may  be
	   used	to enforce that	rule.  The warning is inactive inside a	system
	   header  file,  such	as the STL, so one can still use the STL.  One
	   may also define classes that	indirectly use virtual inheritance.

       -Wno-virtual-move-assign
	   Suppress warnings about inheriting from a virtual base with a  non-
	   trivial  C++11 move assignment operator.  This is dangerous because
	   if the virtual base is reachable along more than one	 path,	it  is
	   moved  multiple  times,  which  can mean both objects end up	in the
	   moved-from state.  If the move assignment operator  is  written  to
	   avoid  moving  from	a  moved-from  object,	this  warning  can  be
	   disabled.

       -Wnamespaces
	   Warn	when a namespace definition  is	 opened.   Some	 coding	 rules
	   disallow  namespaces,  and  this  may be used to enforce that rule.
	   The warning is inactive inside a system header file,	 such  as  the
	   STL,	 so  one  can  still  use  the	STL.   One  may	also use using
	   directives and qualified names.

       -Wno-terminate (C++ and Objective-C++ only)
	   Disable the warning about a throw-expression	that will  immediately
	   result in a call to "terminate".

       -Wno-vexing-parse (C++ and Objective-C++	only)
	   Warn	 about	the most vexing	parse syntactic	ambiguity.  This warns
	   about  the  cases  when  a  declaration  looks  like	  a   variable
	   definition, but the C++ language requires it	to be interpreted as a
	   function declaration.  For instance:

		   void	f(double a) {
		     int i();	     //	extern int i (void);
		     int n(int(a));  //	extern int n (int);
		   }

	   Another example:

		   struct S { S(int); };
		   void	f(double a) {
		     S x(int(a));   // extern struct S x (int);
		     S y(int());    // extern struct S y (int (*) (void));
		     S z();	    // extern struct S z (void);
		   }

	   The	warning	 will  suggest	options	 how  to  deal	with  such  an
	   ambiguity; e.g., it can suggest removing the	parentheses  or	 using
	   braces instead.

	   This	warning	is enabled by default.

       -Wno-class-conversion (C++ and Objective-C++ only)
	   Do  not  warn  when a conversion function converts an object	to the
	   same	type, to a base	class  of  that	 type,	or  to	void;  such  a
	   conversion function will never be called.

       -Wvolatile (C++ and Objective-C++ only)
	   Warn	 about	deprecated  uses  of  the  "volatile" qualifier.  This
	   includes  postfix  and  prefix  "++"	 and   "--"   expressions   of
	   "volatile"-qualified	types, using simple assignments	where the left
	   operand  is	a "volatile"-qualified non-class type for their	value,
	   compound   assignments   where    the    left    operand    is    a
	   "volatile"-qualified	 non-class type, "volatile"-qualified function
	   return type,	"volatile"-qualified parameter	type,  and  structured
	   bindings of a "volatile"-qualified type.  This usage	was deprecated
	   in C++20.

	   Enabled by default with -std=c++20.

       -Wzero-as-null-pointer-constant (C++ and	Objective-C++ only)
	   Warn	 when  a literal 0 is used as null pointer constant.  This can
	   be useful to	facilitate the conversion to "nullptr" in C++11.

       -Waligned-new
	   Warn	about  a  new-expression  of  a	 type  that  requires  greater
	   alignment   than   the   "alignof(std::max_align_t)"	 but  uses  an
	   allocation function without an explicit alignment  parameter.  This
	   option is enabled by	-Wall.

	   Normally  this  only	 warns	about global allocation	functions, but
	   -Waligned-new=all  also  warns  about   class   member   allocation
	   functions.

       -Wno-placement-new
       -Wplacement-new=n
	   Warn	 about placement new expressions with undefined	behavior, such
	   as constructing an object in	a buffer that is smaller than the type
	   of the object.  For example,	the placement new expression below  is
	   diagnosed  because it attempts to construct an array	of 64 integers
	   in a	buffer only 64 bytes large.

		   char	buf [64];
		   new (buf) int[64];

	   This	warning	is enabled by default.

	   -Wplacement-new=1
	       This is the default warning level of -Wplacement-new.  At  this
	       level  the  warning  is	not issued for some strictly undefined
	       constructs that GCC allows as extensions	for compatibility with
	       legacy code.  For example, the following	 "new"	expression  is
	       not  diagnosed  at  this	 level	even  though  it has undefined
	       behavior	according to the C++ standard because it  writes  past
	       the end of the one-element array.

		       struct S	{ int n, a[1]; };
		       S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
		       new (s->a)int [32]();

	   -Wplacement-new=2
	       At   this  level,  in  addition	to  diagnosing	all  the  same
	       constructs as at	level 1,  a  diagnostic	 is  also  issued  for
	       placement  new expressions that construct an object in the last
	       member of structure whose type is an array of a single  element
	       and  whose  size	 is  less  than	 the  size of the object being
	       constructed.  While the previous	example	 would	be  diagnosed,
	       the  following construct	makes use of the flexible member array
	       extension to avoid the warning at level 2.

		       struct S	{ int n, a[]; };
		       S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
		       new (s->a)int [32]();

       -Wcatch-value
       -Wcatch-value=n (C++ and	Objective-C++ only)
	   Warn	about catch handlers that do not catch	via  reference.	  With
	   -Wcatch-value=1 (or -Wcatch-value for short)	warn about polymorphic
	   class  types	 that  are caught by value.  With -Wcatch-value=2 warn
	   about  all  class  types   that   are   caught   by	 value.	  With
	   -Wcatch-value=3  warn  about	 all  types  that  are	not  caught by
	   reference. -Wcatch-value is enabled by -Wall.

       -Wconditionally-supported (C++ and Objective-C++	only)
	   Warn	for conditionally-supported (C++11 [intro.defs]) constructs.

       -Wno-delete-incomplete (C++ and Objective-C++ only)
	   Do not warn when deleting a pointer to incomplete type,  which  may
	   cause  undefined  behavior  at runtime.  This warning is enabled by
	   default.

       -Wextra-semi (C++, Objective-C++	only)
	   Warn	  about	  redundant   semicolons   after   in-class   function
	   definitions.

       -Wno-inaccessible-base (C++, Objective-C++ only)
	   This	 option	controls warnings when a base class is inaccessible in
	   a class derived from	it due to ambiguity.  The warning  is  enabled
	   by  default.	  Note that the	warning	for ambiguous virtual bases is
	   enabled by the -Wextra option.

		   struct A { int a; };

		   struct B : A	{ };

		   struct C : B, A { };

       -Wno-inherited-variadic-ctor
	   Suppress warnings about use of C++11	inheriting  constructors  when
	   the	base  class  inherited	from has a C variadic constructor; the
	   warning is on by default because the	ellipsis is not	inherited.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
	   Suppress warnings from applying the "offsetof" macro	to  a  non-POD
	   type.   According to	the 2014 ISO C++ standard, applying "offsetof"
	   to a	 non-standard-layout  type  is	undefined.   In	 existing  C++
	   implementations,  however,  "offsetof"  typically  gives meaningful
	   results.  This flag is for  users  who  are	aware  that  they  are
	   writing nonportable code and	who have deliberately chosen to	ignore
	   the warning about it.

	   The	restrictions  on "offsetof" may	be relaxed in a	future version
	   of the C++ standard.

       -Wsized-deallocation (C++ and Objective-C++ only)
	   Warn	about a	definition of an unsized deallocation function

		   void	operator delete	(void *) noexcept;
		   void	operator delete[] (void	*) noexcept;

	   without  a  definition  of  the  corresponding  sized  deallocation
	   function

		   void	operator delete	(void *, std::size_t) noexcept;
		   void	operator delete[] (void	*, std::size_t)	noexcept;

	   or vice versa.  Enabled by -Wextra along with -fsized-deallocation.

       -Wsuggest-final-types
	   Warn	 about	types with virtual methods where code quality would be
	   improved  if	 the  type  were  declared  with  the  C++11   "final"
	   specifier,  or,  if	possible,  declared in an anonymous namespace.
	   This	allows GCC to more aggressively	devirtualize  the  polymorphic
	   calls.  This	warning	is more	effective with link-time optimization,
	   where the information about	the  class  hierarchy  graph  is  more
	   complete.

       -Wsuggest-final-methods
	   Warn	 about virtual methods where code quality would	be improved if
	   the method were declared with the C++11 "final" specifier,  or,  if
	   possible,  its type were declared in	an anonymous namespace or with
	   the "final" specifier.  This	warning	is more	effective  with	 link-
	   time	 optimization, where the information about the class hierarchy
	   graph is  more  complete.  It  is  recommended  to  first  consider
	   suggestions	of  -Wsuggest-final-types  and	then  rebuild with new
	   annotations.

       -Wsuggest-override
	   Warn	about overriding virtual functions that	are  not  marked  with
	   the "override" keyword.

       -Wuseless-cast (C++ and Objective-C++ only)
	   Warn	when an	expression is casted to	its own	type.

       -Wno-conversion-null (C++ and Objective-C++ only)
	   Do  not  warn for conversions between "NULL"	and non-pointer	types.
	   -Wconversion-null is	enabled	by default.

   Options Controlling Objective-C and Objective-C++ Dialects
       (NOTE: This manual does not describe the	Objective-C and	 Objective-C++
       languages themselves.

       This   section	describes  the	command-line  options  that  are  only
       meaningful for Objective-C and Objective-C++ programs.	You  can  also
       use  most  of  the  language-independent	 GNU  compiler	options.   For
       example,	you might compile a file some_class.m like this:

	       gcc -g -fgnu-runtime -O -c some_class.m

       In this example,	-fgnu-runtime is an option meant only for  Objective-C
       and  Objective-C++  programs;  you  can	use the	other options with any
       language	supported by GCC.

       Note that  since	 Objective-C  is  an  extension	 of  the  C  language,
       Objective-C  compilations may also use options specific to the C	front-
       end (e.g., -Wtraditional).  Similarly, Objective-C++  compilations  may
       use C++-specific	options	(e.g., -Wabi).

       Here  is	 a list	of options that	are only for compiling Objective-C and
       Objective-C++ programs:

       -fconstant-string-class=class-name
	   Use class-name as the name of the class  to	instantiate  for  each
	   literal  string  specified  with  the syntax	"@"..."".  The default
	   class name is "NXConstantString" if the GNU runtime is being	 used,
	   and	"NSConstantString"  if	the  NeXT  runtime  is being used (see
	   below).    On   Darwin   (macOS,   MacOS    X)    platforms,	   the
	   -fconstant-cfstrings	  option,   if	also  present,	overrides  the
	   -fconstant-string-class setting and cause "@"..."" literals	to  be
	   laid	  out	as   constant	CoreFoundation	 strings.   Note  that
	   -fconstant-cfstrings	 is   an   alias   for	 the   target-specific
	   -mconstant-cfstrings	equivalent.

       -fgnu-runtime
	   Generate  object  code compatible with the standard GNU Objective-C
	   runtime.  This is the default for most types	of systems.

       -fnext-runtime
	   Generate output compatible with the	NeXT  runtime.	 This  is  the
	   default for NeXT-based systems, including Darwin and	Mac OS X.  The
	   macro "__NEXT_RUNTIME__" is predefined if (and only if) this	option
	   is used.

       -fno-nil-receivers
	   Assume   that   all	 Objective-C  message  dispatches  ("[receiver
	   message:arg]") in this translation unit ensure that the receiver is
	   not "nil".  This allows for more  efficient	entry  points  in  the
	   runtime  to	be used.  This option is only available	in conjunction
	   with	the NeXT runtime and ABI version 0 or 1.

       -fobjc-abi-version=n
	   Use version n of the	Objective-C  ABI  for  the  selected  runtime.
	   This	 option	 is currently supported	only for the NeXT runtime.  In
	   that	case, Version  0  is  the  traditional	(32-bit)  ABI  without
	   support   for  properties  and  other  Objective-C  2.0  additions.
	   Version  1  is  the	traditional  (32-bit)  ABI  with  support  for
	   properties  and  other Objective-C 2.0 additions.  Version 2	is the
	   modern (64-bit) ABI.	 If  nothing  is  specified,  the  default  is
	   Version 0 on	32-bit target machines,	and Version 2 on 64-bit	target
	   machines.

       -fobjc-call-cxx-cdtors
	   For	each Objective-C class,	check if any of	its instance variables
	   is a	C++ object with	a non-trivial  default	constructor.   If  so,
	   synthesize  a special "- (id) .cxx_construct" instance method which
	   runs	 non-trivial  default  constructors  on	 any   such   instance
	   variables,  in  order, and then return "self".  Similarly, check if
	   any	instance  variable  is	a  C++	object	with   a   non-trivial
	   destructor,	 and   if   so,	  synthesize   a   special  "-	(void)
	   .cxx_destruct" method which runs all	such default  destructors,  in
	   reverse order.

	   The	"-  (id)  .cxx_construct" and "- (void)	.cxx_destruct" methods
	   thusly generated only operate on instance variables declared	in the
	   current  Objective-C	 class,	  and	not   those   inherited	  from
	   superclasses.   It is the responsibility of the Objective-C runtime
	   to invoke all such methods in an  object's  inheritance  hierarchy.
	   The	"-  (id)  .cxx_construct"  methods  are	invoked	by the runtime
	   immediately after a new object instance is allocated; the "-	(void)
	   .cxx_destruct" methods are invoked immediately before  the  runtime
	   deallocates an object instance.

	   As  of  this	 writing,  only	 the NeXT runtime on Mac OS X 10.4 and
	   later has support for invoking the "- (id) .cxx_construct"  and  "-
	   (void) .cxx_destruct" methods.

       -fobjc-direct-dispatch
	   Allow  fast	jumps  to  the	message	dispatcher.  On	Darwin this is
	   accomplished	via the	comm page.

       -fobjc-exceptions
	   Enable syntactic  support  for  structured  exception  handling  in
	   Objective-C,	 similar  to  what  is offered by C++.	This option is
	   required to use the	Objective-C  keywords  @try,  @throw,  @catch,
	   @finally and	@synchronized.	This option is available with both the
	   GNU	runtime	and the	NeXT runtime (but not available	in conjunction
	   with	the NeXT runtime on Mac	OS X 10.2 and earlier).

       -fobjc-gc
	   Enable garbage collection (GC)  in  Objective-C  and	 Objective-C++
	   programs.  This option is only available with the NeXT runtime; the
	   GNU	runtime	has a different	garbage	collection implementation that
	   does	not require special compiler flags.

       -fobjc-nilcheck
	   For the NeXT	runtime	with version 2 of the ABI,  check  for	a  nil
	   receiver in method invocations before doing the actual method call.
	   This	 is  the default and can be disabled using -fno-objc-nilcheck.
	   Class methods and super calls are never checked for nil in this way
	   no matter what this flag is	set  to.   Currently  this  flag  does
	   nothing  when  the  GNU  runtime,  or  an older version of the NeXT
	   runtime ABI,	is used.

       -fobjc-std=objc1
	   Conform to the language syntax of  Objective-C  1.0,	 the  language
	   recognized by GCC 4.0.  This	only affects the Objective-C additions
	   to  the  C/C++  language;  it  does not affect conformance to C/C++
	   standards, which is controlled by the separate C/C++	dialect	option
	   flags.   When  this	option	is  used  with	the   Objective-C   or
	   Objective-C++   compiler,   any  Objective-C	 syntax	 that  is  not
	   recognized by GCC 4.0 is rejected.  This is useful if you  need  to
	   make	 sure  that  your  Objective-C code can	be compiled with older
	   versions of GCC.

       -freplace-objc-classes
	   Emit	a special marker instructing ld(1) not to statically  link  in
	   the	resulting  object file,	and allow dyld(1) to load it in	at run
	   time	instead.  This	is  used  in  conjunction  with	 the  Fix-and-
	   Continue  debugging	mode, where the	object file in question	may be
	   recompiled and  dynamically	reloaded  in  the  course  of  program
	   execution,	without	 the  need  to	restart	 the  program  itself.
	   Currently, Fix-and-Continue	functionality  is  only	 available  in
	   conjunction with the	NeXT runtime on	Mac OS X 10.3 and later.

       -fzero-link
	   When	 compiling  for	 the  NeXT  runtime,  the  compiler ordinarily
	   replaces calls to "objc_getClass("...")"  (when  the	 name  of  the
	   class  is  known at compile time) with static class references that
	   get initialized at load time, which improves	run-time  performance.
	   Specifying the -fzero-link flag suppresses this behavior and	causes
	   calls to "objc_getClass("...")"  to be retained.  This is useful in
	   Zero-Link  debugging	 mode,	since  it  allows for individual class
	   implementations to be modified during program execution.   The  GNU
	   runtime  currently  always retains calls to "objc_get_class("...")"
	   regardless of command-line options.

       -fno-local-ivars
	   By default instance variables in Objective-C	can be accessed	as  if
	   they	 were  local  variables	 from  within the methods of the class
	   they're declared in.	 This can lead to shadowing  between  instance
	   variables  and  other  variables  declared  either locally inside a
	   class method	or  globally  with  the	 same  name.   Specifying  the
	   -fno-local-ivars flag disables this behavior	thus avoiding variable
	   shadowing issues.

       -fivar-visibility=[public|protected|private|package]
	   Set	the  default  instance	variable  visibility  to the specified
	   option so that instance variables declared outside the scope	of any
	   access modifier directives default to the specified visibility.

       -gen-decls
	   Dump	interface declarations for all classes seen in the source file
	   to a	file named sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
	   Warn	whenever an Objective-C	assignment is being intercepted	by the
	   garbage collector.

       -Wno-property-assign-default (Objective-C and Objective-C++ only)
	   Do not warn if a property for an Objective-C	object has  no	assign
	   semantics specified.

       -Wno-protocol (Objective-C and Objective-C++ only)
	   If a	class is declared to implement a protocol, a warning is	issued
	   for	every  method  in  the protocol	that is	not implemented	by the
	   class.  The default behavior	is to issue a warning for every	method
	   not	explicitly  implemented	 in  the  class,  even	if  a	method
	   implementation  is  inherited  from the superclass.	If you use the
	   -Wno-protocol option, then methods inherited	 from  the  superclass
	   are	considered  to	be  implemented,  and no warning is issued for
	   them.

       -Wobjc-root-class (Objective-C and Objective-C++	only)
	   Warn	if a class interface lacks a  superclass.  Most	 classes  will
	   inherit  from "NSObject" (or	"Object") for example.	When declaring
	   classes intended to be root classes,	the warning can	be  suppressed
	   by	       marking		their	       interfaces	  with
	   "__attribute__((objc_root_class))".

       -Wselector (Objective-C and Objective-C++ only)
	   Warn	if multiple methods of different types for the	same  selector
	   are	found  during compilation.  The	check is performed on the list
	   of methods in the final  stage  of  compilation.   Additionally,  a
	   check   is	performed   for	  each	 selector   appearing	in   a
	   "@selector(...)"  expression, and a corresponding method  for  that
	   selector  has  been found during compilation.  Because these	checks
	   scan	the method  table  only	 at  the  end  of  compilation,	 these
	   warnings  are not produced if the final stage of compilation	is not
	   reached, for	example	because	an error is found during  compilation,
	   or because the -fsyntax-only	option is being	used.

       -Wstrict-selector-match (Objective-C and	Objective-C++ only)
	   Warn	 if  multiple  methods	with  differing	argument and/or	return
	   types are found for a given selector	 when  attempting  to  send  a
	   message  using this selector	to a receiver of type "id" or "Class".
	   When	this flag is off (which	is the default behavior), the compiler
	   omits such warnings if any differences found	are confined to	 types
	   that	share the same size and	alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
	   Warn	 if  a	"@selector(...)" expression referring to an undeclared
	   selector is found.  A  selector  is	considered  undeclared	if  no
	   method with that name has been declared before the "@selector(...)"
	   expression,	 either	 explicitly  in	 an  @interface	 or  @protocol
	   declaration,	or implicitly in  an  @implementation  section.	  This
	   option  always  performs  its  checks as soon as a "@selector(...)"
	   expression is found,	while -Wselector only performs its  checks  in
	   the	final  stage  of  compilation.	 This also enforces the	coding
	   style convention that methods and selectors must be declared	before
	   being used.

       -print-objc-runtime-info
	   Generate C header describing	the largest structure that  is	passed
	   by value, if	any.

   Options to Control Diagnostic Messages Formatting
       Traditionally,  diagnostic messages have	been formatted irrespective of
       the output device's aspect (e.g.	its width,  ...).   You	 can  use  the
       options	described  below  to  control  the  formatting	algorithm  for
       diagnostic messages, e.g. how  many  characters	per  line,  how	 often
       source  location	 information  should  be  reported.   Note  that  some
       language	front ends may not honor these options.

       -fmessage-length=n
	   Try to format error messages	so that	they fit on lines of  about  n
	   characters.	 If  n	is  zero,  then	no line-wrapping is done; each
	   error message appears on a single line.  This is  the  default  for
	   all front ends.

	   Note	 -  this  option  also	affects	 the display of	the #error and
	   #warning   pre-processor    directives,    and    the    deprecated
	   function/type/variable  attribute.	It does	not however affect the
	   pragma GCC warning and pragma GCC error pragmas.

       -fdiagnostics-plain-output
	   This	option requests	 that  diagnostic  output  look	 as  plain  as
	   possible,  which  may  be  useful  when  running  dejagnu  or other
	   utilities that need to parse	diagnostics output and prefer that  it
	   remain   more  stable  over	time.	-fdiagnostics-plain-output  is
	   currently	 equivalent	to     the     following      options:
	   -fno-diagnostics-show-caret	    -fno-diagnostics-show-line-numbers
	   -fdiagnostics-color=never		      -fdiagnostics-urls=never
	   -fdiagnostics-path-format=separate-events  In  the  future,	if GCC
	   changes  the	  default   appearance	 of   its   diagnostics,   the
	   corresponding  option  to disable the new behavior will be added to
	   this	list.

       -fdiagnostics-show-location=once
	   Only	meaningful in line-wrapping mode.   Instructs  the  diagnostic
	   messages  reporter  to  emit	source location	information once; that
	   is, in case the message is too long to fit  on  a  single  physical
	   line	 and  has  to be wrapped, the source location won't be emitted
	   (as prefix) again, over and over, in	subsequent continuation	lines.
	   This	is the default behavior.

       -fdiagnostics-show-location=every-line
	   Only	meaningful in line-wrapping mode.   Instructs  the  diagnostic
	   messages  reporter to emit the same source location information (as
	   prefix) for physical	lines that result from the process of breaking
	   a message which is too long to fit on a single line.

       -fdiagnostics-color[=WHEN]
       -fno-diagnostics-color
	   Use color in	diagnostics.  WHEN is never,  always,  or  auto.   The
	   default  depends on how the compiler	has been configured, it	can be
	   any	of  the	 above	WHEN  options  or  also	 never	if  GCC_COLORS
	   environment	variable  isn't	 present  in the environment, and auto
	   otherwise.  auto makes GCC use color	only when the  standard	 error
	   is a	terminal, and when not executing in an emacs shell.  The forms
	   -fdiagnostics-color	and  -fno-diagnostics-color  are  aliases  for
	   -fdiagnostics-color=always	   and	    -fdiagnostics-color=never,
	   respectively.

	   The colors are defined by the environment variable GCC_COLORS.  Its
	   value  is a colon-separated list of capabilities and	Select Graphic
	   Rendition (SGR) substrings. SGR commands  are  interpreted  by  the
	   terminal   or   terminal   emulator.	   (See	 the  section  in  the
	   documentation of your text terminal for permitted values and	 their
	   meanings  as	 character  attributes.)   These  substring values are
	   integers in decimal representation and  can	be  concatenated  with
	   semicolons.	Common values to concatenate include 1 for bold, 4 for
	   underline,  5  for  blink, 7	for inverse, 39	for default foreground
	   color, 30 to	37 for foreground colors, 90 to	97 for	16-color  mode
	   foreground  colors,	38;5;0	to 38;5;255 for	88-color and 256-color
	   modes foreground colors, 49 for default background color, 40	to  47
	   for	background  colors,  100  to  107 for 16-color mode background
	   colors, and 48;5;0 to 48;5;255 for  88-color	 and  256-color	 modes
	   background colors.

	   The default GCC_COLORS is

		   error=01;31:warning=01;35:note=01;36:range1=32:range2=34:locus=01:\
		   quote=01:path=01;36:fixit-insert=32:fixit-delete=31:\
		   diff-filename=01:diff-hunk=32:diff-delete=31:diff-insert=32:\
		   type-diff=01;32

	   where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold cyan,
	   32  is  green,  34  is  blue,  01  is bold, and 31 is red.  Setting
	   GCC_COLORS  to  the	empty  string  disables	  colors.    Supported
	   capabilities	are as follows.

	   "error="
	       SGR substring for error:	markers.

	   "warning="
	       SGR substring for warning: markers.

	   "note="
	       SGR substring for note: markers.

	   "path="
	       SGR  substring  for  colorizing paths of	control-flow events as
	       printed via -fdiagnostics-path-format=, such as the identifiers
	       of individual events and	lines indicating interprocedural calls
	       and returns.

	   "range1="
	       SGR substring for first additional range.

	   "range2="
	       SGR substring for second	additional range.

	   "locus="
	       SGR  substring	for   location	 information,	file:line   or
	       file:line:column	etc.

	   "quote="
	       SGR substring for information printed within quotes.

	   "fixit-insert="
	       SGR  substring  for fix-it hints	suggesting text	to be inserted
	       or replaced.

	   "fixit-delete="
	       SGR substring for fix-it	hints suggesting text to be deleted.

	   "diff-filename="
	       SGR substring for filename headers within generated patches.

	   "diff-hunk="
	       SGR substring for the starts of hunks within generated patches.

	   "diff-delete="
	       SGR substring for deleted lines within generated	patches.

	   "diff-insert="
	       SGR substring for inserted lines	within generated patches.

	   "type-diff="
	       SGR  substring  for  highlighting  mismatching	types	within
	       template	arguments in the C++ frontend.

       -fdiagnostics-urls[=WHEN]
	   Use	escape	sequences  to embed URLs in diagnostics.  For example,
	   when	-fdiagnostics-show-option emits	text showing the  command-line
	   option  controlling	a diagnostic, embed a URL for documentation of
	   that	option.

	   WHEN	is never, always, or auto.  auto  makes	 GCC  use  URL	escape
	   sequences  only when	the standard error is a	terminal, and when not
	   executing in	an emacs shell or  any	graphical  terminal  which  is
	   known to be incompatible with this feature, see below.

	   The	default	 depends  on how the compiler has been configured.  It
	   can be any of the above WHEN	options.

	   GCC	    can	     also      be      configured	(via	   the
	   --with-diagnostics-urls=auto-if-env	configure-time option) so that
	   the default is affected by environment  variables.	Under  such  a
	   configuration,  GCC	defaults  to  using auto if either GCC_URLS or
	   TERM_URLS environment variables are present and  non-empty  in  the
	   environment of the compiler,	or never if neither are.

	   However,   even  with  -fdiagnostics-urls=always  the  behavior  is
	   dependent on	those environment variables: If	 GCC_URLS  is  set  to
	   empty  or no, do not	embed URLs in diagnostics.  If set to st, URLs
	   use ST escape sequences.  If	set to bel, the	default, URLs use  BEL
	   escape  sequences.	Any other non-empty value enables the feature.
	   If GCC_URLS is not set, use TERM_URLS as a fallback.	 Note:	ST  is
	   an  ANSI  escape sequence, string terminator	ESC \, BEL is an ASCII
	   character, CTRL-G that usually sounds like a	beep.

	   At this time	GCC tries to detect also  a  few  terminals  that  are
	   known  to  not implement the	URL feature, and have bugs or at least
	   had bugs in some versions that are still  in	 use,  where  the  URL
	   escapes  are	likely to misbehave, i.e. print	garbage	on the screen.
	   That	list is	currently xfce4-terminal, certain known	 to  be	 buggy
	   gnome-terminal  versions, the linux console,	and mingw.  This check
	   can be skipped with the -fdiagnostics-urls=always.

       -fno-diagnostics-show-option
	   By default, each diagnostic emitted includes	 text  indicating  the
	   command-line	 option	that directly controls the diagnostic (if such
	   an option is	known to the diagnostic	 machinery).   Specifying  the
	   -fno-diagnostics-show-option	flag suppresses	that behavior.

       -fno-diagnostics-show-caret
	   By  default,	 each  diagnostic emitted includes the original	source
	   line	and a caret ^ indicating the column.  This  option  suppresses
	   this	information.  The source line is truncated to n	characters, if
	   the -fmessage-length=n option is given.  When the output is done to
	   the	terminal,  the	width  is  limited  to	the width given	by the
	   COLUMNS environment variable	or, if not set,	to the terminal	width.

       -fno-diagnostics-show-labels
	   By	  default,     when	printing     source	code	  (via
	   -fdiagnostics-show-caret),  diagnostics  can	label ranges of	source
	   code	with pertinent information, such as the	types of expressions:

		       printf ("foo %s bar", long_i + long_j);
				    ~^	     ~~~~~~~~~~~~~~~
				     |		    |
				     char *	    long int

	   This	option suppresses the printing of these	labels (in the example
	   above, the vertical bars and	the "char *" and "long int" text).

       -fno-diagnostics-show-cwe
	   Diagnostic	messages   can	 optionally   have    an    associated
	   @url{https://cwe.mitre.org/index.html, CWE} identifier.  GCC	itself
	   only	provides such metadata for some	of the -fanalyzer diagnostics.
	   GCC	plugins	 may  also provide diagnostics with such metadata.  By
	   default, if this information	is present, it will  be	 printed  with
	   the	diagnostic.   This  option  suppresses	the  printing  of this
	   metadata.

       -fno-diagnostics-show-line-numbers
	   By	  default,     when	printing     source	code	  (via
	   -fdiagnostics-show-caret),  a  left margin is printed, showing line
	   numbers.  This option suppresses this left margin.

       -fdiagnostics-minimum-margin-width=width
	   This	option controls	the minimum width of the left  margin  printed
	   by -fdiagnostics-show-line-numbers.	It defaults to 6.

       -fdiagnostics-parseable-fixits
	   Emit	 fix-it	 hints	in  a  machine-parseable  format, suitable for
	   consumption by IDEs.	 For each fix-it, a line will be printed after
	   the relevant	diagnostic, starting with the string  "fix-it:".   For
	   example:

		   fix-it:"test.c":{45:3-45:21}:"gtk_widget_show_all"

	   The	location  is  expressed	 as  a half-open range,	expressed as a
	   count of bytes, starting at byte 1 for the initial column.  In  the
	   above  example, bytes 3 through 20 of line 45 of "test.c" are to be
	   replaced with the given string:

		   00000000011111111112222222222
		   12345678901234567890123456789
		     gtk_widget_showall	(dlg);
		     ^^^^^^^^^^^^^^^^^^
		     gtk_widget_show_all

	   The filename	and replacement	string escape backslash	as  "\\",  tab
	   as  "\t",  newline  as  "\n",  double quotes	as "\"", non-printable
	   characters as octal (e.g. vertical tab as "\013").

	   An empty replacement	string indicates that the given	range is to be
	   removed.  An	empty range  (e.g.  "45:3-45:3")  indicates  that  the
	   string is to	be inserted at the given position.

       -fdiagnostics-generate-patch
	   Print  fix-it  hints	 to  stderr  in	unified	diff format, after any
	   diagnostics are printed.  For example:

		   --- test.c
		   +++ test.c
		   @ -42,5 +42,5 @

		    void show_cb(GtkDialog *dlg)
		    {
		   -  gtk_widget_showall(dlg);
		   +  gtk_widget_show_all(dlg);
		    }

	   The diff may	or may not be colorized, following the same  rules  as
	   for diagnostics (see	-fdiagnostics-color).

       -fdiagnostics-show-template-tree
	   In  the C++ frontend, when printing diagnostics showing mismatching
	   template types, such	as:

		     could not convert 'std::map<int, std::vector<double> >()'
		       from 'map<[...],vector<double>>'	to 'map<[...],vector<float>>

	   the -fdiagnostics-show-template-tree	flag enables printing a	 tree-
	   like	structure showing the common and differing parts of the	types,
	   such	as:

		     map<
		       [...],
		       vector<
			 [double != float]>>

	   The	parts  that  differ  are  highlighted with color ("double" and
	   "float" in this case).

       -fno-elide-type
	   By  default	when  the  C++	frontend  prints  diagnostics  showing
	   mismatching	template  types, common	parts of the types are printed
	   as "[...]" to simplify the error message.  For example:

		     could not convert 'std::map<int, std::vector<double> >()'
		       from 'map<[...],vector<double>>'	to 'map<[...],vector<float>>

	   Specifying the -fno-elide-type flag suppresses that behavior.  This
	   flag	     also      affects	    the	     output	  of	   the
	   -fdiagnostics-show-template-tree flag.

       -fdiagnostics-path-format=KIND
	   Specify  how	 to print paths	of control-flow	events for diagnostics
	   that	have such a path associated with them.

	   KIND	is none, separate-events, or inline-events, the	default.

	   none	means to not print diagnostic paths.

	   separate-events means to print a  separate  "note"  diagnostic  for
	   each	event within the diagnostic.  For example:

		   test.c:29:5:	error: passing NULL as argument	1 to 'PyList_Append' which requires a non-NULL parameter
		   test.c:25:10: note: (1) when	'PyList_New' fails, returning NULL
		   test.c:27:3:	note: (2) when 'i < count'
		   test.c:29:5:	note: (3) when calling 'PyList_Append',	passing	NULL from (1) as argument 1

	   inline-events  means	to print the events "inline" within the	source
	   code.  This view attempts to	consolidate the	events	into  runs  of
	   sufficiently-close  events, printing	them as	labelled ranges	within
	   the source.

	   For example,	the same events	as above might be printed as:

		     'test': events 1-3
		       |
		       |   25 |	  list = PyList_New(0);
		       |      |		 ^~~~~~~~~~~~~
		       |      |		 |
		       |      |		 (1) when 'PyList_New' fails, returning	NULL
		       |   26 |
		       |   27 |	  for (i = 0; i	< count; i++) {
		       |      |	  ~~~
		       |      |	  |
		       |      |	  (2) when 'i <	count'
		       |   28 |	    item = PyLong_FromLong(random());
		       |   29 |	    PyList_Append(list,	item);
		       |      |	    ~~~~~~~~~~~~~~~~~~~~~~~~~
		       |      |	    |
		       |      |	    (3)	when calling 'PyList_Append', passing NULL from	(1) as argument	1
		       |

	   Interprocedural control flow	is shown by  grouping  the  events  by
	   stack  frame,  and  using  indentation to show how stack frames are
	   nested, pushed, and popped.

	   For example:

		     'test': events 1-2
		       |
		       |  133 |	{
		       |      |	^
		       |      |	|
		       |      |	(1) entering 'test'
		       |  134 |	  boxed_int *obj = make_boxed_int (i);
		       |      |			   ~~~~~~~~~~~~~~~~~~
		       |      |			   |
		       |      |			   (2) calling 'make_boxed_int'
		       |
		       +--> 'make_boxed_int': events 3-4
			      |
			      |	 120 | {
			      |	     | ^
			      |	     | |
			      |	     | (3) entering 'make_boxed_int'
			      |	 121 |	 boxed_int *result = (boxed_int	*)wrapped_malloc (sizeof (boxed_int));
			      |	     |					  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
			      |	     |					  |
			      |	     |					  (4) calling 'wrapped_malloc'
			      |
			      +--> 'wrapped_malloc': events 5-6
				     |
				     |	  7 | {
				     |	    | ^
				     |	    | |
				     |	    | (5) entering 'wrapped_malloc'
				     |	  8 |	return malloc (size);
				     |	    |	       ~~~~~~~~~~~~~
				     |	    |	       |
				     |	    |	       (6) calling 'malloc'
				     |
		       <-------------+
		       |
		    'test': event 7
		       |
		       |  138 |	  free_boxed_int (obj);
		       |      |	  ^~~~~~~~~~~~~~~~~~~~
		       |      |	  |
		       |      |	  (7) calling 'free_boxed_int'
		       |
		   (etc)

       -fdiagnostics-show-path-depths
	   This	option provides	additional information when printing  control-
	   flow	paths associated with a	diagnostic.

	   If  this is option is provided then the stack depth will be printed
	   for	      each	  run	      of	 events		within
	   -fdiagnostics-path-format=separate-events.

	   This	 is  intended  for use by GCC developers and plugin developers
	   when	debugging  diagnostics	that  report  interprocedural  control
	   flow.

       -fno-show-column
	   Do  not print column	numbers	in diagnostics.	 This may be necessary
	   if diagnostics are  being  scanned  by  a  program  that  does  not
	   understand the column numbers, such as dejagnu.

       -fdiagnostics-column-unit=UNIT
	   Select  the	units for the column number.  This affects traditional
	   diagnostics (in the absence of -fno-show-column), as	well  as  JSON
	   format diagnostics if requested.

	   The	default	UNIT, display, considers the number of display columns
	   occupied by each character.	This may be larger than	the number  of
	   bytes  required  to	encode	the  character,	 in  the  case	of tab
	   characters, or  it  may  be	smaller,  in  the  case	 of  multibyte
	   characters.	 For  example,	the  character	"GREEK SMALL LETTER PI
	   (U+03C0)" occupies one  display  column,  and  its  UTF-8  encoding
	   requires two	bytes; the character "SLIGHTLY SMILING FACE (U+1F642)"
	   occupies  two display columns, and its UTF-8	encoding requires four
	   bytes.

	   Setting UNIT	to byte	changes	the column  number  to	the  raw  byte
	   count  in  all  cases,  as was traditionally	output by GCC prior to
	   version 11.1.0.

       -fdiagnostics-column-origin=ORIGIN
	   Select the origin  for  column  numbers,  i.e.  the	column	number
	   assigned  to	 the first column.  The	default	value of 1 corresponds
	   to traditional GCC behavior and  to	the  GNU  style	 guide.	  Some
	   utilities  may perform better with an origin	of 0; any non-negative
	   value may be	specified.

       -fdiagnostics-format=FORMAT
	   Select a different format for printing diagnostics.	FORMAT is text
	   or json.  The default is text.

	   The json format consists of a top-level JSON	array containing  JSON
	   objects representing	the diagnostics.

	   The	JSON  is emitted as one	line, without formatting; the examples
	   below have been formatted for clarity.

	   Diagnostics can have	child diagnostics.  For	 example,  this	 error
	   and note:

		   misleading-indentation.c:15:3: warning: this	'if' clause does not
		     guard... [-Wmisleading-indentation]
		      15 |   if	(flag)
			 |   ^~
		   misleading-indentation.c:17:5: note:	...this	statement, but the latter
		     is	misleadingly indented as if it were guarded by the 'if'
		      17 |     y = 2;
			 |     ^

	   might be printed in JSON form (after	formatting) like this:

		   [
		       {
			   "kind": "warning",
			   "locations":	[
			       {
				   "caret": {
				       "display-column": 3,
				       "byte-column": 3,
				       "column": 3,
				       "file": "misleading-indentation.c",
				       "line": 15
				   },
				   "finish": {
				       "display-column": 4,
				       "byte-column": 4,
				       "column": 4,
				       "file": "misleading-indentation.c",
				       "line": 15
				   }
			       }
			   ],
			   "message": "this \u2018if\u2019 clause does not guard...",
			   "option": "-Wmisleading-indentation",
			   "option_url": "https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmisleading-indentation",
			   "children": [
			       {
				   "kind": "note",
				   "locations":	[
				       {
					   "caret": {
					       "display-column": 5,
					       "byte-column": 5,
					       "column": 5,
					       "file": "misleading-indentation.c",
					       "line": 17
					   }
				       }
				   ],
				   "message": "...this statement, but the latter is ..."
			       }
			   ]
			   "column-origin": 1,
		       },
		       ...
		   ]

	   where the "note" is a child of the "warning".

	   A  diagnostic has a "kind".	If this	is "warning", then there is an
	   "option" key	describing the	command-line  option  controlling  the
	   warning.

	   A diagnostic	can contain zero or more locations.  Each location has
	   an  optional	 "label" string	and up to three	positions within it: a
	   "caret" position and	optional "start" and  "finish"	positions.   A
	   position  is	described by a "file" name, a "line" number, and three
	   numbers indicating a	column position:

	   *   "display-column"	counts display columns,	 accounting  for  tabs
	       and multibyte characters.

	   *   "byte-column" counts raw	bytes.

	   *   "column"	 is  equal  to one of the previous two,	as dictated by
	       the -fdiagnostics-column-unit option.

	   All	three  columns	are  relative  to  the	origin	specified   by
	   -fdiagnostics-column-origin,	 which is typically equal to 1 but may
	   be set, for instance, to 0 for compatibility	with  other  utilities
	   that	 number	 columns from 0.  The column origin is recorded	in the
	   JSON	output in the "column-origin" tag.  In the remaining  examples
	   below,  the	extra  column  number  outputs	have  been omitted for
	   brevity.

	   For example,	this error:

		   bad-binary-ops.c:64:23: error: invalid operands to binary + (have 'S' {aka
		      'struct s'} and 'T' {aka 'struct t'})
		      64 |   return callee_4a () + callee_4b ();
			 |	    ~~~~~~~~~~~~ ^ ~~~~~~~~~~~~
			 |	    |		   |
			 |	    |		   T {aka struct t}
			 |	    S {aka struct s}

	   has three locations.	 Its primary location is at the	"+"  token  at
	   column 23.  It has two secondary locations, describing the left and
	   right-hand sides of the expression, which have labels.  It might be
	   printed in JSON form	as:

		       {
			   "children": [],
			   "kind": "error",
			   "locations":	[
			       {
				   "caret": {
				       "column": 23, "file": "bad-binary-ops.c", "line": 64
				   }
			       },
			       {
				   "caret": {
				       "column": 10, "file": "bad-binary-ops.c", "line": 64
				   },
				   "finish": {
				       "column": 21, "file": "bad-binary-ops.c", "line": 64
				   },
				   "label": "S {aka struct s}"
			       },
			       {
				   "caret": {
				       "column": 25, "file": "bad-binary-ops.c", "line": 64
				   },
				   "finish": {
				       "column": 36, "file": "bad-binary-ops.c", "line": 64
				   },
				   "label": "T {aka struct t}"
			       }
			   ],
			   "message": "invalid operands	to binary + ..."
		       }

	   If  a  diagnostic  contains	fix-it hints, it has a "fixits"	array,
	   consisting  of  half-open  intervals,  similar  to  the  output  of
	   -fdiagnostics-parseable-fixits.   For example, this diagnostic with
	   a replacement fix-it	hint:

		   demo.c:8:15:	error: 'struct s' has no member	named 'colour';	did you
		     mean 'color'?
		       8 |   return ptr->colour;
			 |		 ^~~~~~
			 |		 color

	   might be printed in JSON form as:

		       {
			   "children": [],
			   "fixits": [
			       {
				   "next": {
				       "column": 21,
				       "file": "demo.c",
				       "line": 8
				   },
				   "start": {
				       "column": 15,
				       "file": "demo.c",
				       "line": 8
				   },
				   "string": "color"
			       }
			   ],
			   "kind": "error",
			   "locations":	[
			       {
				   "caret": {
				       "column": 15,
				       "file": "demo.c",
				       "line": 8
				   },
				   "finish": {
				       "column": 20,
				       "file": "demo.c",
				       "line": 8
				   }
			       }
			   ],
			   "message": "\u2018struct s\u2019 has	no member named	..."
		       }

	   where the fix-it hint suggests replacing the	text from  "start"  up
	   to  but  not	including "next" with "string"'s value.	 Deletions are
	   expressed via an empty value	for  "string",	insertions  by	having
	   "start" equal "next".

	   If the diagnostic has a path	of control-flow	events associated with
	   it, it has a	"path" array of	objects	representing the events.  Each
	   event object	has a "description" string, a "location" object, along
	   with	 a  "function"	string	and  a "depth" number for representing
	   interprocedural  paths.   The  "function"  represents  the  current
	   function  at	that event, and	the "depth" represents the stack depth
	   relative to some baseline: the higher, the more frames  are	within
	   the stack.

	   For	  example,    the    intraprocedural	example	   shown   for
	   -fdiagnostics-path-format= might have this JSON for its path:

		       "path": [
			   {
			       "depth":	0,
			       "description": "when 'PyList_New' fails,	returning NULL",
			       "function": "test",
			       "location": {
				   "column": 10,
				   "file": "test.c",
				   "line": 25
			       }
			   },
			   {
			       "depth":	0,
			       "description": "when 'i < count'",
			       "function": "test",
			       "location": {
				   "column": 3,
				   "file": "test.c",
				   "line": 27
			       }
			   },
			   {
			       "depth":	0,
			       "description": "when calling 'PyList_Append', passing NULL from (1) as argument 1",
			       "function": "test",
			       "location": {
				   "column": 5,
				   "file": "test.c",
				   "line": 29
			       }
			   }
		       ]

   Options to Request or Suppress Warnings
       Warnings	are diagnostic messages	that report constructions that are not
       inherently erroneous but	that are risky or suggest there	may have  been
       an error.

       The  following  language-independent  options  do  not  enable specific
       warnings	but control the	kinds of diagnostics produced by GCC.

       -fsyntax-only
	   Check the code for syntax errors,  but  don't  do  anything	beyond
	   that.

       -fmax-errors=n
	   Limits  the	maximum	 number	of error messages to n,	at which point
	   GCC bails out rather	than attempting	 to  continue  processing  the
	   source  code.   If  n  is 0 (the default), there is no limit	on the
	   number of error  messages  produced.	  If  -Wfatal-errors  is  also
	   specified, then -Wfatal-errors takes	precedence over	this option.

       -w  Inhibit all warning messages.

       -Werror
	   Make	all warnings into errors.

       -Werror=
	   Make	 the  specified	 warning  into	an error.  The specifier for a
	   warning is appended;	for example -Werror=switch turns the  warnings
	   controlled  by  -Wswitch into errors.  This switch takes a negative
	   form, to be used to	negate	-Werror	 for  specific	warnings;  for
	   example  -Wno-error=switch  makes  -Wswitch warnings	not be errors,
	   even	when -Werror is	in effect.

	   The warning message for  each  controllable	warning	 includes  the
	   option  that	 controls  the	warning.  That option can then be used
	   with	-Werror= and -Wno-error= as described above.  (Printing	of the
	   option  in  the  warning  message  can  be	disabled   using   the
	   -fno-diagnostics-show-option	flag.)

	   Note	 that  specifying  -Werror=foo	automatically  implies	-Wfoo.
	   However, -Wno-error=foo does	not imply anything.

       -Wfatal-errors
	   This	option causes the compiler to abort compilation	on  the	 first
	   error  occurred  rather  than  trying  to  keep  going and printing
	   further error messages.

       You can request many specific warnings with options beginning with  -W,
       for  example  -Wimplicit	 to request warnings on	implicit declarations.
       Each of these  specific	warning	 options  also	has  a	negative  form
       beginning -Wno- to turn off warnings; for example, -Wno-implicit.  This
       manual  lists  only one of the two forms, whichever is not the default.
       For further language-specific options also refer	to C++ Dialect Options
       and Objective-C and Objective-C++ Dialect Options.  Additional warnings
       can be produced by enabling the static analyzer;

       Some options, such as -Wall and -Wextra,	turn on	other options, such as
       -Wunused, which may turn	on further options,  such  as  -Wunused-value.
       The  combined  effect  of  positive  and	 negative  forms  is that more
       specific	options	have priority over less	specific  ones,	 independently
       of  their  position  in	the  command-line.  For	 options  of  the same
       specificity, the	last one takes effect. Options enabled or disabled via
       pragmas take effect as if they appeared at the end of the command-line.

       When   an   unrecognized	  warning   option   is	   requested	(e.g.,
       -Wunknown-warning),  GCC	 emits a diagnostic stating that the option is
       not recognized.	However, if the	-Wno- form is used,  the  behavior  is
       slightly	 different: no diagnostic is produced for -Wno-unknown-warning
       unless other diagnostics	are being produced.  This allows  the  use  of
       new  -Wno- options with old compilers, but if something goes wrong, the
       compiler	warns that an unrecognized option is present.

       The effectiveness of some warnings depends on optimizations also	 being
       enabled.	For example -Wsuggest-final-types is more effective with link-
       time optimization and -Wmaybe-uninitialized does	not warn at all	unless
       optimization is enabled.

       -Wpedantic
       -pedantic
	   Issue all the warnings demanded by strict ISO C and ISO C++;	reject
	   all programs	that use forbidden extensions, and some	other programs
	   that	 do  not  follow  ISO  C  and ISO C++.	For ISO	C, follows the
	   version of the ISO C	standard specified by any -std option used.

	   Valid ISO C and ISO C++ programs should compile  properly  with  or
	   without  this  option  (though  a  rare few require -ansi or	a -std
	   option specifying the required version of ISO C).  However, without
	   this	option,	certain	GNU  extensions	 and  traditional  C  and  C++
	   features  are  supported  as	 well.	 With  this  option,  they are
	   rejected.

	   -Wpedantic does not cause warning messages for use of the alternate
	   keywords whose names	begin and end with __.	This alternate	format
	   can also be used to disable warnings	for non-ISO __intN types, i.e.
	   __intN__.   Pedantic	 warnings  are also disabled in	the expression
	   that	follows	"__extension__".  However, only	 system	 header	 files
	   should  use	these escape routes; application programs should avoid
	   them.

	   Some	users try to use -Wpedantic to check programs for strict ISO C
	   conformance.	 They soon find	that it	does not do  quite  what  they
	   want: it finds some non-ISO practices, but not all---only those for
	   which  ISO  C  requires  a  diagnostic,  and	 some others for which
	   diagnostics have been added.

	   A feature to	report any failure to conform to ISO C might be	useful
	   in some instances, but would	require	considerable  additional  work
	   and	would be quite different from -Wpedantic.  We don't have plans
	   to support such a feature in	the near future.

	   Where the standard specified	with -std represents  a	 GNU  extended
	   dialect of C, such as gnu90 or gnu99, there is a corresponding base
	   standard, the version of ISO	C on which the GNU extended dialect is
	   based.   Warnings from -Wpedantic are given where they are required
	   by the base standard.  (It does not make sense for such warnings to
	   be given only for features not in  the  specified  GNU  C  dialect,
	   since  by definition	the GNU	dialects of C include all features the
	   compiler supports with the given option, and	there would be nothing
	   to warn about.)

       -pedantic-errors
	   Give	an error whenever the base standard (see -Wpedantic)  requires
	   a  diagnostic,  in  some cases where	there is undefined behavior at
	   compile-time	 and  in  some	other  cases  that  do	 not   prevent
	   compilation	of  programs that are valid according to the standard.
	   This	is not equivalent to -Werror=pedantic, since there are	errors
	   enabled  by	this  option  and  not	enabled	by the latter and vice
	   versa.

       -Wall
	   This	enables	all the	warnings about constructions that  some	 users
	   consider  questionable,  and	 that  are easy	to avoid (or modify to
	   prevent the warning), even in conjunction with macros.   This  also
	   enables  some  language-specific  warnings described	in C++ Dialect
	   Options and Objective-C and Objective-C++ Dialect Options.

	   -Wall turns on the following	warning	flags:

	   -Waddress -Warray-bounds=1 (only with -O2)  -Warray-parameter=2  (C
	   and	   Objective-C	   only)    -Wbool-compare    -Wbool-operation
	   -Wc++11-compat  -Wc++14-compat -Wcatch-value	(C++ and Objective-C++
	   only) -Wchar-subscripts -Wcomment -Wduplicate-decl-specifier	(C and
	   Objective-C only) -Wenum-compare (in	C/ObjC;	this is	on by  default
	   in	  C++)	  -Wformat    -Wformat-overflow	   -Wformat-truncation
	   -Wint-in-bool-context   -Wimplicit	(C   and   Objective-C	 only)
	   -Wimplicit-int	 (C	   and	      Objective-C	 only)
	   -Wimplicit-function-declaration   (C	   and	  Objective-C	 only)
	   -Winit-self	(only  for C++)	-Wlogical-not-parentheses -Wmain (only
	   for	C/ObjC	and   unless   -ffreestanding)	 -Wmaybe-uninitialized
	   -Wmemset-elt-size -Wmemset-transposed-args -Wmisleading-indentation
	   (only  for  C/C++)  -Wmissing-attributes -Wmissing-braces (only for
	   C/ObjC)  -Wmultistatement-macros   -Wnarrowing   (only   for	  C++)
	   -Wnonnull	 -Wnonnull-compare     -Wopenmp-simd	 -Wparentheses
	   -Wpessimizing-move	  (only	     for      C++)	-Wpointer-sign
	   -Wrange-loop-construct   (only   for	  C++)	 -Wreorder  -Wrestrict
	   -Wreturn-type  -Wsequence-point  -Wsign-compare   (only   in	  C++)
	   -Wsizeof-array-div  -Wsizeof-pointer-div -Wsizeof-pointer-memaccess
	   -Wstrict-aliasing	       -Wstrict-overflow=1	      -Wswitch
	   -Wtautological-compare	   -Wtrigraphs	       -Wuninitialized
	   -Wunknown-pragmas -Wunused-function	-Wunused-label	-Wunused-value
	   -Wunused-variable   -Wvla-parameter	 (C   and   Objective-C	 only)
	   -Wvolatile-register-var -Wzero-length-bounds

	   Note	that some warning flags	are not	implied	 by  -Wall.   Some  of
	   them	 warn about constructions that users generally do not consider
	   questionable, but which occasionally	you might wish to  check  for;
	   others warn about constructions that	are necessary or hard to avoid
	   in  some  cases,  and  there	is no simple way to modify the code to
	   suppress the	warning. Some of them are enabled by -Wextra but  many
	   of them must	be enabled individually.

       -Wextra
	   This	 enables  some	extra  warning	flags  that are	not enabled by
	   -Wall. (This	option used to be called -W.  The older	name is	 still
	   supported, but the newer name is more descriptive.)

	   -Wclobbered	 -Wcast-function-type	-Wdeprecated-copy  (C++	 only)
	   -Wempty-body	 -Wenum-conversion   (C	  only)	  -Wignored-qualifiers
	   -Wimplicit-fallthrough=3		  -Wmissing-field-initializers
	   -Wmissing-parameter-type (C only) -Wold-style-declaration (C	 only)
	   -Woverride-init    -Wsign-compare	(C    only)   -Wstring-compare
	   -Wredundant-move  (only  for	 C++)  -Wtype-limits   -Wuninitialized
	   -Wshift-negative-value  (in	C++11  to  C++17 and in	C99 and	newer)
	   -Wunused-parameter	 (only	   with	    -Wunused	 or	-Wall)
	   -Wunused-but-set-parameter (only with -Wunused or -Wall)

	   The	option	-Wextra	also prints warning messages for the following
	   cases:

	   *   A pointer is compared against integer zero with "<", "<=", ">",
	       or ">=".

	   *   (C++ only) An enumerator	and a non-enumerator both appear in  a
	       conditional expression.

	   *   (C++ only) Ambiguous virtual bases.

	   *   (C++  only)  Subscripting  an  array  that  has	been  declared
	       "register".

	   *   (C++ only) Taking the address  of  a  variable  that  has  been
	       declared	"register".

	   *   (C++  only)  A  base  class  is	not  initialized  in  the copy
	       constructor of a	derived	class.

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
	   Warn	about code affected by ABI changes.  This includes  code  that
	   may	not  be	 compatible with the vendor-neutral C++	ABI as well as
	   the psABI for the particular	target.

	   Since G++ now defaults to updating the ABI with each	major release,
	   normally -Wabi warns	only about C++ ABI compatibility  problems  if
	   there  is  a	check added later in a release series for an ABI issue
	   discovered since the	 initial  release.   -Wabi  warns  about  more
	   things if an	older ABI version is selected (with -fabi-version=n).

	   -Wabi  can  also  be	 used  with an explicit	version	number to warn
	   about C++ ABI compatibility with a particular -fabi-version	level,
	   e.g.	-Wabi=2	to warn	about changes relative to -fabi-version=2.

	   If  an explicit version number is provided and -fabi-compat-version
	   is not specified, the version number	from this option is  used  for
	   compatibility  aliases.   If	no explicit version number is provided
	   with	this  option,  but  -fabi-compat-version  is  specified,  that
	   version number is used for C++ ABI warnings.

	   Although  an	 effort	 has  been  made to warn about all such	cases,
	   there are probably some cases  that	are  not  warned  about,  even
	   though  G++	is  generating	incompatible  code.  There may also be
	   cases where warnings	are emitted  even  though  the	code  that  is
	   generated is	compatible.

	   You	should	rewrite	 your  code to avoid these warnings if you are
	   concerned about the fact that code generated	 by  G++  may  not  be
	   binary compatible with code generated by other compilers.

	   Known  incompatibilities  in	-fabi-version=2	(which was the default
	   from	GCC 3.4	to 4.9)	include:

	   *   A template with a non-type template parameter of	reference type
	       was mangled incorrectly:

		       extern int N;
		       template	<int &>	struct S {};
		       void n (S<N>) {2}

	       This was	fixed in -fabi-version=3.

	   *   SIMD vector types declared using	"__attribute  ((vector_size))"
	       were  mangled  in  a  non-standard  way that does not allow for
	       overloading of functions	taking vectors of different sizes.

	       The mangling was	changed	in -fabi-version=4.

	   *   "__attribute ((const))" and "noreturn"  were  mangled  as  type
	       qualifiers,  and	 "decltype"  of	a plain	declaration was	folded
	       away.

	       These mangling issues were fixed	in -fabi-version=5.

	   *   Scoped enumerators passed as arguments to a  variadic  function
	       are  promoted  like  unscoped  enumerators, causing "va_arg" to
	       complain.  On most targets this does not	 actually  affect  the
	       parameter  passing  ABI,	as there is no way to pass an argument
	       smaller than "int".

	       Also, the ABI changed the mangling of template argument	packs,
	       "const_cast",  "static_cast", prefix increment/decrement, and a
	       class scope function used as a template argument.

	       These issues were corrected in -fabi-version=6.

	   *   Lambdas in default argument scope were mangled incorrectly, and
	       the ABI changed the mangling of "nullptr_t".

	       These issues were corrected in -fabi-version=7.

	   *   When mangling a function	type with function-cv-qualifiers,  the
	       un-qualified   function	type  was  incorrectly	treated	 as  a
	       substitution candidate.

	       This was	fixed in -fabi-version=8, the default for GCC 5.1.

	   *   "decltype(nullptr)" incorrectly had an alignment	of 1,  leading
	       to  unaligned  accesses.	 Note that this	did not	affect the ABI
	       of a function with a "nullptr_t"	parameter, as parameters  have
	       a minimum alignment.

	       This was	fixed in -fabi-version=9, the default for GCC 5.2.

	   *   Target-specific	attributes that	affect the identity of a type,
	       such as ia32 calling conventions	on a function  type  (stdcall,
	       regparm,	 etc.),	 did  not  affect the mangled name, leading to
	       name collisions when function pointers were  used  as  template
	       arguments.

	       This was	fixed in -fabi-version=10, the default for GCC 6.1.

	   This	option also enables warnings about psABI-related changes.  The
	   known psABI changes at this point include:

	   *   For  SysV/x86-64,  unions with "long double" members are	passed
	       in memory as specified in psABI.	 Prior to GCC  4.4,  this  was
	       not the case.  For example:

		       union U {
			 long double ld;
			 int i;
		       };

	       "union U" is now	always passed in memory.

       -Wchar-subscripts
	   Warn	if an array subscript has type "char".	This is	a common cause
	   of  error,  as programmers often forget that	this type is signed on
	   some	machines.  This	warning	is enabled by -Wall.

       -Wno-coverage-mismatch
	   Warn	if feedback profiles do	not match when using the -fprofile-use
	   option.  If	a  source  file	 is  changed  between  compiling  with
	   -fprofile-generate  and  with  -fprofile-use,  the  files  with the
	   profile feedback can	fail to	match the source file and  GCC	cannot
	   use	the profile feedback information.  By default, this warning is
	   enabled and is treated as an	error.	-Wno-coverage-mismatch can  be
	   used	 to disable the	warning	or -Wno-error=coverage-mismatch	can be
	   used	to disable the error.  Disabling the error  for	 this  warning
	   can	result in poorly optimized code	and is useful only in the case
	   of very minor changes such as bug fixes to an  existing  code-base.
	   Completely disabling	the warning is not recommended.

       -Wno-cpp
	   (C,	Objective-C,  C++,  Objective-C++  and	Fortran	only) Suppress
	   warning messages emitted by "#warning" directives.

       -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
	   Give	a warning when a value of type "float" is implicitly  promoted
	   to  "double".  CPUs with a 32-bit "single-precision"	floating-point
	   unit	 implement  "float"  in	 hardware,  but	 emulate  "double"  in
	   software.   On  such	 a  machine, doing computations	using "double"
	   values is much more expensive because of the	overhead required  for
	   software emulation.

	   It  is  easy	 to accidentally do computations with "double" because
	   floating-point literals  are	 implicitly  of	 type  "double".   For
	   example, in:

		   float area(float radius)
		   {
		      return 3.14159 * radius *	radius;
		   }

	   the	compiler performs the entire computation with "double" because
	   the floating-point literal is a "double".

       -Wduplicate-decl-specifier (C and Objective-C only)
	   Warn	if a declaration has duplicate "const",	"volatile", "restrict"
	   or "_Atomic"	specifier.  This warning is enabled by -Wall.

       -Wformat
       -Wformat=n
	   Check calls to "printf" and "scanf",	etc., to make  sure  that  the
	   arguments  supplied	have  types  appropriate  to the format	string
	   specified, and that the conversions specified in the	format	string
	   make	sense.	This includes standard functions, and others specified
	   by  format  attributes,  in	the  "printf", "scanf",	"strftime" and
	   "strfmon" (an X/Open	extension, not in the C	standard) families (or
	   other  target-specific  families).	Which  functions  are  checked
	   without  format  attributes	having	been  specified	depends	on the
	   standard version selected, and such checks of functions without the
	   attribute specified are disabled by -ffreestanding or -fno-builtin.

	   The formats are checked against the format  features	 supported  by
	   GNU	libc version 2.2.  These include all ISO C90 and C99 features,
	   as well as features from the	Single Unix Specification and some BSD
	   and GNU extensions.	Other library implementations may not  support
	   all	these  features;  GCC  does not	support	warning	about features
	   that	go beyond a particular	library's  limitations.	  However,  if
	   -Wpedantic  is  used	with -Wformat, warnings	are given about	format
	   features  not  in  the  selected  standard  version	(but  not  for
	   "strfmon"  formats,	since  those  are  not in any version of the C
	   standard).

	   -Wformat=1
	   -Wformat
	       Option -Wformat is equivalent to	-Wformat=1, and	-Wno-format is
	       equivalent to -Wformat=0.  Since	-Wformat also checks for  null
	       format  arguments  for several functions, -Wformat also implies
	       -Wnonnull.  Some	aspects	of this	level of format	 checking  can
	       be   disabled   by   the	  options:   -Wno-format-contains-nul,
	       -Wno-format-extra-args, and -Wno-format-zero-length.   -Wformat
	       is enabled by -Wall.

	   -Wformat=2
	       Enable  -Wformat	 plus  additional  format  checks.   Currently
	       equivalent to  -Wformat	-Wformat-nonliteral  -Wformat-security
	       -Wformat-y2k.

       -Wno-format-contains-nul
	   If  -Wformat	 is  specified,	 do not	warn about format strings that
	   contain NUL bytes.

       -Wno-format-extra-args
	   If -Wformat is specified, do	not warn about excess arguments	 to  a
	   "printf" or "scanf" format function.	 The C standard	specifies that
	   such	arguments are ignored.

	   Where  the  unused  arguments  lie  between used arguments that are
	   specified with $ operand number specifications,  normally  warnings
	   are	still given, since the implementation could not	know what type
	   to pass to "va_arg" to skip the unused arguments.  However, in  the
	   case	 of "scanf" formats, this option suppresses the	warning	if the
	   unused  arguments  are  all	pointers,  since   the	 Single	  Unix
	   Specification says that such	unused arguments are allowed.

       -Wformat-overflow
       -Wformat-overflow=level
	   Warn	 about	calls  to  formatted  input/output  functions  such as
	   "sprintf"  and  "vsprintf"  that  might  overflow  the  destination
	   buffer.   When  the	exact  number  of  bytes  written  by a	format
	   directive cannot be determined  at  compile-time  it	 is  estimated
	   based  on  heuristics  that	depend	on  the	 level argument	and on
	   optimization.  While	 enabling  optimization	 will  in  most	 cases
	   improve  the	 accuracy  of the warning, it may also result in false
	   positives.

	   -Wformat-overflow
	   -Wformat-overflow=1
	       Level 1 of -Wformat-overflow  enabled  by  -Wformat  employs  a
	       conservative  approach  that  warns  only about calls that most
	       likely overflow the buffer.  At this level,  numeric  arguments
	       to  format  directives  with unknown values are assumed to have
	       the value of one, and strings of	unknown	length	to  be	empty.
	       Numeric arguments that are known	to be bounded to a subrange of
	       their  type, or string arguments	whose output is	bounded	either
	       by their	directive's precision or by a  finite  set  of	string
	       literals,  are  assumed	to  take on the	value within the range
	       that results in the most	bytes on  output.   For	 example,  the
	       call  to	 "sprintf" below is diagnosed because even with	both a
	       and b equal to  zero,  the  terminating	NUL  character	('\0')
	       appended	 by  the  function  to	the destination	buffer will be
	       written past its	end.  Increasing the size of the buffer	 by  a
	       single  byte  is	sufficient to avoid the	warning, though	it may
	       not be sufficient to avoid the overflow.

		       void f (int a, int b)
		       {
			 char buf [13];
			 sprintf (buf, "a = %i,	b = %i\n", a, b);
		       }

	   -Wformat-overflow=2
	       Level  2	 warns	also  about  calls  that  might	 overflow  the
	       destination  buffer  given  an argument of sufficient length or
	       magnitude.  At level 2, unknown numeric arguments  are  assumed
	       to have the minimum representable value for signed types	with a
	       precision  greater  than	1, and the maximum representable value
	       otherwise.  Unknown string arguments  whose  length  cannot  be
	       assumed	to  be bounded either by the directive's precision, or
	       by a finite set of string literals they may evaluate to,	or the
	       character array	they  may  point  to,  are  assumed  to	 be  1
	       character long.

	       At  level  2, the call in the example above is again diagnosed,
	       but this	time because with a equal to a	32-bit	"INT_MIN"  the
	       first %i	directive will write some of its digits	beyond the end
	       of the destination buffer.  To make the call safe regardless of
	       the  values  of	the two	variables, the size of the destination
	       buffer must be increased	to at least 34	bytes.	 GCC  includes
	       the  minimum  size  of  the  buffer  in	an  informational note
	       following the warning.

	       An alternative to increasing the	size of	the destination	buffer
	       is to constrain the range of  formatted	values.	  The  maximum
	       length  of  string  arguments  can be bounded by	specifying the
	       precision in the	format directive.  When	numeric	 arguments  of
	       format directives can be	assumed	to be bounded by less than the
	       precision   of  their  type,  choosing  an  appropriate	length
	       modifier	to the	format	specifier  will	 reduce	 the  required
	       buffer  size.  For example, if a	and b in the example above can
	       be assumed to be	within the precision of	the "short  int"  type
	       then  using  either  the	 %hi  format  directive	or casting the
	       argument	to "short" reduces the maximum required	 size  of  the
	       buffer to 24 bytes.

		       void f (int a, int b)
		       {
			 char buf [23];
			 sprintf (buf, "a = %hi, b = %i\n", a, (short)b);
		       }

       -Wno-format-zero-length
	   If  -Wformat	 is  specified,	do not warn about zero-length formats.
	   The C standard specifies that zero-length formats are allowed.

       -Wformat-nonliteral
	   If -Wformat is specified, also warn if the format string is	not  a
	   string literal and so cannot	be checked, unless the format function
	   takes its format arguments as a "va_list".

       -Wformat-security
	   If  -Wformat	is specified, also warn	about uses of format functions
	   that	represent possible security problems.  At present, this	 warns
	   about  calls	 to  "printf"  and  "scanf" functions where the	format
	   string is not a string literal and there are	no  format  arguments,
	   as  in  "printf (foo);".  This may be a security hole if the	format
	   string came	from  untrusted	 input	and  contains  %n.   (This  is
	   currently  a	subset of what -Wformat-nonliteral warns about,	but in
	   future warnings may be added	 to  -Wformat-security	that  are  not
	   included in -Wformat-nonliteral.)

       -Wformat-signedness
	   If  -Wformat	 is specified, also warn if the	format string requires
	   an unsigned argument	and the	argument is signed and vice versa.

       -Wformat-truncation
       -Wformat-truncation=level
	   Warn	about  calls  to  formatted  input/output  functions  such  as
	   "snprintf"  and "vsnprintf" that might result in output truncation.
	   When	the exact number of bytes written by a format directive	cannot
	   be determined at compile-time it is estimated based	on  heuristics
	   that	 depend	 on  the  level	 argument  and on optimization.	 While
	   enabling optimization will in most cases improve  the  accuracy  of
	   the	warning,  it  may  also	 result	in false positives.  Except as
	   noted otherwise, the	option uses the	same logic -Wformat-overflow.

	   -Wformat-truncation
	   -Wformat-truncation=1
	       Level 1 of -Wformat-truncation enabled by  -Wformat  employs  a
	       conservative  approach  that  warns only	about calls to bounded
	       functions whose return value  is	 unused	 and  that  will  most
	       likely result in	output truncation.

	   -Wformat-truncation=2
	       Level  2	 warns	also  about  calls  to bounded functions whose
	       return value is used and	that might result in truncation	 given
	       an argument of sufficient length	or magnitude.

       -Wformat-y2k
	   If  -Wformat	 is specified, also warn about "strftime" formats that
	   may yield only a two-digit year.

       -Wnonnull
	   Warn	about passing a	null pointer for arguments marked as requiring
	   a non-null value by the "nonnull" function attribute.

	   -Wnonnull is	included in -Wall and -Wformat.	 It  can  be  disabled
	   with	the -Wno-nonnull option.

       -Wnonnull-compare
	   Warn	 when comparing	an argument marked with	the "nonnull" function
	   attribute against null inside the function.

	   -Wnonnull-compare is	included in -Wall.  It can  be	disabled  with
	   the -Wno-nonnull-compare option.

       -Wnull-dereference
	   Warn	 if  the  compiler  detects  paths  that  trigger erroneous or
	   undefined behavior due  to  dereferencing  a	 null  pointer.	  This
	   option  is only active when -fdelete-null-pointer-checks is active,
	   which is enabled by optimizations in	most targets.	The  precision
	   of the warnings depends on the optimization options used.

       -Winit-self (C, C++, Objective-C	and Objective-C++ only)
	   Warn	 about	uninitialized  variables  that	are  initialized  with
	   themselves.	 Note  this  option  can  only	be   used   with   the
	   -Wuninitialized option.

	   For	example,  GCC  warns  about  "i"  being	 uninitialized	in the
	   following snippet only when -Winit-self has been specified:

		   int f()
		   {
		     int i = i;
		     return i;
		   }

	   This	warning	is enabled by -Wall in C++.

       -Wno-implicit-int (C and	Objective-C only)
	   This	option controls	warnings when a	declaration does not specify a
	   type.  This warning is enabled by default in	C99 and	later dialects
	   of C, and also by -Wall.

       -Wno-implicit-function-declaration (C and Objective-C only)
	   This	option controls	warnings when a	function is used before	 being
	   declared.   This  warning  is  enabled  by default in C99 and later
	   dialects of C, and also by -Wall.  The  warning  is	made  into  an
	   error by -pedantic-errors.

       -Wimplicit (C and Objective-C only)
	   Same	 as  -Wimplicit-int and	-Wimplicit-function-declaration.  This
	   warning is enabled by -Wall.

       -Wimplicit-fallthrough
	   -Wimplicit-fallthrough is the same as -Wimplicit-fallthrough=3  and
	   -Wno-implicit-fallthrough is	the same as -Wimplicit-fallthrough=0.

       -Wimplicit-fallthrough=n
	   Warn	when a switch case falls through.  For example:

		   switch (cond)
		     {
		     case 1:
		       a = 1;
		       break;
		     case 2:
		       a = 2;
		     case 3:
		       a = 3;
		       break;
		     }

	   This	warning	does not warn when the last statement of a case	cannot
	   fall	 through,  e.g.	 when there is a return	statement or a call to
	   function	declared     with     the     noreturn	    attribute.
	   -Wimplicit-fallthrough=   also  takes  into	account	 control  flow
	   statements, such as ifs, and	only warns when	appropriate.  E.g.

		   switch (cond)
		     {
		     case 1:
		       if (i > 3) {
			 bar (5);
			 break;
		       } else if (i < 1) {
			 bar (0);
		       } else
			 return;
		     default:
		       ...
		     }

	   Since there are occasions where  a  switch  case  fall  through  is
	   desirable,	 GCC	provides    an	  attribute,	"__attribute__
	   ((fallthrough))", that is to	be used	along with a null statement to
	   suppress this warning that would normally occur:

		   switch (cond)
		     {
		     case 1:
		       bar (0);
		       __attribute__ ((fallthrough));
		     default:
		       ...
		     }

	   C++17    provides	a    standard	 way	to    suppress	   the
	   -Wimplicit-fallthrough  warning using "[[fallthrough]];" instead of
	   the	GNU  attribute.	   In	C++11	or   C++14   users   can   use
	   "[[gnu::fallthrough]];",  which  is	a  GNU	extension.  Instead of
	   these attributes, it	is also	possible to add	a fallthrough  comment
	   to  silence	the  warning.	The  whole  body of the	C or C++ style
	   comment should match	the given regular  expressions	listed	below.
	   The option argument n specifies what	kind of	comments are accepted:

	   *<-Wimplicit-fallthrough=0 disables the warning altogether.>
	   *<-Wimplicit-fallthrough=1 matches ".*" regular>
	       expression, any comment is used as fallthrough comment.

	   *<-Wimplicit-fallthrough=2 case insensitively matches>
	       ".*falls?[ \t-]*thr(ough|u).*" regular expression.

	   *<-Wimplicit-fallthrough=3 case sensitively matches one of the>
	       following regular expressions:

	       *<"-fallthrough">
	       *<"@fallthrough@">
	       *<"lint -fallthrough[ \t]*">
	       *<"[ \t.!]*(ELSE,? |INTENTIONAL(LY)? )?FALL(S |
	       |-)?THR(OUGH|U)[	\t.!]*(-[^\n\r]*)?">
	       *<"[ \t.!]*(Else,? |Intentional(ly)? )?Fall((s |
	       |-)[Tt]|t)hr(ough|u)[ \t.!]*(-[^\n\r]*)?">
	       *<"[ \t.!]*([Ee]lse,? |[Ii]ntentional(ly)? )?fall(s |
	       |-)?thr(ough|u)[	\t.!]*(-[^\n\r]*)?">
	   *<-Wimplicit-fallthrough=4 case sensitively matches one of the>
	       following regular expressions:

	       *<"-fallthrough">
	       *<"@fallthrough@">
	       *<"lint -fallthrough[ \t]*">
	       *<"[ \t]*FALLTHR(OUGH|U)[ \t]*">
	   *<-Wimplicit-fallthrough=5 doesn't recognize	any comments as>
	       fallthrough comments, only attributes disable the warning.

	   The	comment	 needs	to  be	followed after optional	whitespace and
	   other comments by "case" or "default" keywords or by	a  user	 label
	   that	precedes some "case" or	"default" label.

		   switch (cond)
		     {
		     case 1:
		       bar (0);
		       /* FALLTHRU */
		     default:
		       ...
		     }

	   The -Wimplicit-fallthrough=3	warning	is enabled by -Wextra.

       -Wno-if-not-aligned (C, C++, Objective-C	and Objective-C++ only)
	   Control   if	  warnings   triggered	by  the	 "warn_if_not_aligned"
	   attribute should be issued.	These warnings are enabled by default.

       -Wignored-qualifiers (C and C++ only)
	   Warn	if the return type of a	function has a type qualifier such  as
	   "const".   For ISO C	such a type qualifier has no effect, since the
	   value returned by a function	 is  not  an  lvalue.	For  C++,  the
	   warning  is	only  emitted  for  scalar  types  or  "void".	 ISO C
	   prohibits qualified "void" return types on function definitions, so
	   such	return types  always  receive  a  warning  even	 without  this
	   option.

	   This	warning	is also	enabled	by -Wextra.

       -Wno-ignored-attributes (C and C++ only)
	   This	 option	 controls warnings when	an attribute is	ignored.  This
	   is different	from the -Wattributes option in	that it	warns whenever
	   the compiler	decides	to drop	an attribute, not that	the  attribute
	   is  either  unknown,	 used  in a wrong place, etc.  This warning is
	   enabled by default.

       -Wmain
	   Warn	if the type of "main"  is  suspicious.	 "main"	 should	 be  a
	   function  with  external linkage, returning int, taking either zero
	   arguments, two, or three  arguments	of  appropriate	 types.	  This
	   warning is enabled by default in C++	and is enabled by either -Wall
	   or -Wpedantic.

       -Wmisleading-indentation	(C and C++ only)
	   Warn	 when  the  indentation	of the code does not reflect the block
	   structure.  Specifically, a warning is  issued  for	"if",  "else",
	   "while",  and  "for"	clauses	with a guarded statement that does not
	   use braces, followed	 by  an	 unguarded  statement  with  the  same
	   indentation.

	   In  the  following  example,	 the  call  to	"bar"  is misleadingly
	   indented as if it were guarded by the "if" conditional.

		     if	(some_condition	())
		       foo ();
		       bar ();	/* Gotcha: this	is not guarded by the "if".  */

	   In the case	of  mixed  tabs	 and  spaces,  the  warning  uses  the
	   -ftabstop=	option	 to   determine	 if  the  statements  line  up
	   (defaulting to 8).

	   The warning is not issued for code involving	multiline preprocessor
	   logic such as the following example.

		     if	(flagA)
		       foo (0);
		   #if SOME_CONDITION_THAT_DOES_NOT_HOLD
		     if	(flagB)
		   #endif
		       foo (1);

	   The warning is not issued after a  "#line"  directive,  since  this
	   typically  indicates	 autogenerated code, and no assumptions	can be
	   made	about the layout of the	file that the directive	references.

	   This	warning	is enabled by -Wall in C and C++.

       -Wmissing-attributes
	   Warn	when a declaration of  a  function  is	missing	 one  or  more
	   attributes  that  a	related	 function  is  declared	with and whose
	   absence may adversely  affect  the  correctness  or	efficiency  of
	   generated   code.	For   example,	 the  warning  is  issued  for
	   declarations	 of  aliases  that  use	 attributes  to	 specify  less
	   restrictive	 requirements  than  those  of	their  targets.	  This
	   typically represents	 a  potential  optimization  opportunity.   By
	   contrast,  the  -Wattribute-alias=2 option controls warnings	issued
	   when	the alias is more restrictive than  the	 target,  which	 could
	   lead	 to  incorrect code generation.	 Attributes considered include
	   "alloc_align",  "alloc_size",  "cold",  "const",   "hot",   "leaf",
	   "malloc",	 "nonnull",	"noreturn",	"nothrow",     "pure",
	   "returns_nonnull", and "returns_twice".

	   In C++, the warning is issued when an explicit specialization of  a
	   primary    template	  declared   with   attribute	"alloc_align",
	   "alloc_size", "assume_aligned", "format",  "format_arg",  "malloc",
	   or  "nonnull"  is  declared	without	 it.  Attributes "deprecated",
	   "error", and	"warning" suppress the warning..

	   You can  use	 the  "copy"  attribute	 to  apply  the	 same  set  of
	   attributes  to a declaration	as that	on another declaration without
	   explicitly  enumerating  the	 attributes.  This  attribute  can  be
	   applied to declarations of functions, variables, or types.

	   -Wmissing-attributes	is enabled by -Wall.

	   For example,	since the declaration of the primary function template
	   below  makes	 use  of  both attribute "malloc" and "alloc_size" the
	   declaration of the  explicit	 specialization	 of  the  template  is
	   diagnosed because it	is missing one of the attributes.

		   template <class T>
		   T* __attribute__ ((malloc, alloc_size (1)))
		   allocate (size_t);

		   template <>
		   void* __attribute__ ((malloc))   // missing alloc_size
		   allocate<void> (size_t);

       -Wmissing-braces
	   Warn	 if  an	aggregate or union initializer is not fully bracketed.
	   In the following example, the initializer  for  "a"	is  not	 fully
	   bracketed, but that for "b" is fully	bracketed.

		   int a[2][2] = { 0, 1, 2, 3 };
		   int b[2][2] = { { 0,	1 }, { 2, 3 } };

	   This	warning	is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
	   Warn	if a user-supplied include directory does not exist.

       -Wno-missing-profile
	   This	option controls	warnings if feedback profiles are missing when
	   using  the -fprofile-use option.  This option diagnoses those cases
	   where a new function	or a new file is added between compiling  with
	   -fprofile-generate and with -fprofile-use, without regenerating the
	   profiles.   In  these cases,	the profile feedback data files	do not
	   contain any	profile	 feedback  information	for  the  newly	 added
	   function  or	 file  respectively.   Also,  in the case when profile
	   count data (.gcda) files are	removed, GCC cannot  use  any  profile
	   feedback  information.   In all these cases,	warnings are issued to
	   inform you that a profile generation	step  is  due.	 Ignoring  the
	   warning  can	result in poorly optimized code.  -Wno-missing-profile
	   can be used to disable the warning, but this	is not recommended and
	   should be done only when non-existent profile data is justified.

       -Wno-mismatched-dealloc
	   Warn	for calls to deallocation  functions  with  pointer  arguments
	   returned from from allocations functions for	which the former isn't
	   a  suitable	deallocator.  A	pair of	functions can be associated as
	   matching allocators and deallocators	by use of attribute  "malloc".
	   Unless  disabled  by	the -fno-builtin option	the standard functions
	   "calloc",  "malloc",	 "realloc",  and  "free",  as  well   as   the
	   corresponding forms of C++ "operator	new" and "operator delete" are
	   implicitly  associated as matching allocators and deallocators.  In
	   the following example "mydealloc" is	the deallocator	 for  pointers
	   returned from "myalloc".

		   void	mydealloc (void*);

		   __attribute__ ((malloc (mydealloc, 1))) void*
		   myalloc (size_t);

		   void	f (void)
		   {
		     void *p = myalloc (32);
		     //	...use p...
		     free (p);	 // warning: not a matching deallocator	for myalloc
		     mydealloc (p);   // ok
		   }

	   In	C++,  the  related  option  -Wmismatched-new-delete  diagnoses
	   mismatches involving	either "operator new" or "operator delete".

	   Option -Wmismatched-dealloc is enabled by default.

       -Wmultistatement-macros
	   Warn	about unsafe multiple  statement  macros  that	appear	to  be
	   guarded  by	a  clause  such	 as  "if", "else", "for", "switch", or
	   "while", in which only the  first  statement	 is  actually  guarded
	   after the macro is expanded.

	   For example:

		   #define DOIT	x++; y++
		   if (c)
		     DOIT;

	   will	 increment  "y"	unconditionally, not just when "c" holds.  The
	   can usually be fixed	by wrapping the	macro in a do-while loop:

		   #define DOIT	do { x++; y++; } while (0)
		   if (c)
		     DOIT;

	   This	warning	is enabled by -Wall in C and C++.

       -Wparentheses
	   Warn	if parentheses are omitted in certain contexts,	such  as  when
	   there  is  an  assignment  in  a  context  where  a	truth value is
	   expected, or	when operators	are  nested  whose  precedence	people
	   often get confused about.

	   Also	  warn	if  a  comparison  like	 "x<=y<=z"  appears;  this  is
	   equivalent to "(x<=y	 ?  1  :  0)  <=  z",  which  is  a  different
	   interpretation from that of ordinary	mathematical notation.

	   Also	 warn  for  dangerous  uses  of	the GNU	extension to "?:" with
	   omitted middle operand. When	the condition in the "?": operator  is
	   a  boolean  expression,  the	 omitted  value	 is  always  1.	 Often
	   programmers expect it to be a value computed	inside the conditional
	   expression instead.

	   For C++ this	also warns for some cases of  unnecessary  parentheses
	   in  declarations,  which can	indicate an attempt at a function call
	   instead of a	declaration:

		   {
		     //	Declares a local variable called mymutex.
		     std::unique_lock<std::mutex> (mymutex);
		     //	User meant std::unique_lock<std::mutex>	lock (mymutex);
		   }

	   This	warning	is enabled by -Wall.

       -Wsequence-point
	   Warn	about code  that  may  have  undefined	semantics  because  of
	   violations of sequence point	rules in the C and C++ standards.

	   The	C and C++ standards define the order in	which expressions in a
	   C/C++ program are evaluated in  terms  of  sequence	points,	 which
	   represent  a	partial	ordering between the execution of parts	of the
	   program: those  executed  before  the  sequence  point,  and	 those
	   executed  after  it.	  These	 occur	after the evaluation of	a full
	   expression (one which is not	part of	a  larger  expression),	 after
	   the	evaluation  of the first operand of a "&&", "||", "? :"	or ","
	   (comma) operator, before  a	function  is  called  (but  after  the
	   evaluation  of its arguments	and the	expression denoting the	called
	   function), and in certain other places.  Other than as expressed by
	   the sequence	point rules, the order of evaluation of	subexpressions
	   of an expression is not specified.  All these rules describe	only a
	   partial order rather	than a total order, since, for example,	if two
	   functions are called	within one expression with no  sequence	 point
	   between  them,  the	order in which the functions are called	is not
	   specified.	However,  the  standards  committee  have  ruled  that
	   function calls do not overlap.

	   It  is  not specified when between sequence points modifications to
	   the values of objects take effect.  Programs	whose behavior depends
	   on this have	undefined behavior; the	C and  C++  standards  specify
	   that	 "Between the previous and next	sequence point an object shall
	   have	its stored value modified at most once by the evaluation of an
	   expression.	Furthermore, the prior value shall  be	read  only  to
	   determine  the  value  to  be  stored.".  If	a program breaks these
	   rules, the results on any particular	 implementation	 are  entirely
	   unpredictable.

	   Examples  of	 code  with undefined behavior are "a =	a++;", "a[n] =
	   b[n++]" and "a[i++] = i;".  Some more  complicated  cases  are  not
	   diagnosed  by  this	option,	 and  it  may give an occasional false
	   positive result, but	in general it has been found fairly  effective
	   at detecting	this sort of problem in	programs.

	   The	C++17 standard will define the order of	evaluation of operands
	   in more cases: in particular	it requires that the  right-hand  side
	   of  an  assignment  be  evaluated before the	left-hand side,	so the
	   above examples are no longer	undefined.  But	this option will still
	   warn	about  them,  to  help	people	avoid  writing	code  that  is
	   undefined in	C and earlier revisions	of C++.

	   The	standard is worded confusingly,	therefore there	is some	debate
	   over	the precise meaning of the  sequence  point  rules  in	subtle
	   cases.   Links  to  discussions  of the problem, including proposed
	   formal definitions, may be found  on	 the  GCC  readings  page,  at
	   <http://gcc.gnu.org/readings.html>.

	   This	warning	is enabled by -Wall for	C and C++.

       -Wno-return-local-addr
	   Do not warn about returning a pointer (or in	C++, a reference) to a
	   variable that goes out of scope after the function returns.

       -Wreturn-type
	   Warn	 whenever  a  function	is  defined  with  a  return type that
	   defaults to "int".  Also warn about any "return" statement with  no
	   return value	in a function whose return type	is not "void" (falling
	   off	the end	of the function	body is	considered returning without a
	   value).

	   For C only, warn about a "return" statement with an expression in a
	   function whose return type is "void", unless	the expression type is
	   also	"void".	 As a GNU  extension,  the  latter  case  is  accepted
	   without a warning unless -Wpedantic is used.	 Attempting to use the
	   return  value of a non-"void" function other	than "main" that flows
	   off the end by reaching the closing curly brace that	terminates the
	   function is undefined.

	   Unlike in C,	in C++,	flowing	off the	end of a  non-"void"  function
	   other than "main" results in	undefined behavior even	when the value
	   of the function is not used.

	   This	warning	is enabled by default in C++ and by -Wall otherwise.

       -Wno-shift-count-negative
	   Controls  warnings  if  a shift count is negative.  This warning is
	   enabled by default.

       -Wno-shift-count-overflow
	   Controls warnings if	a shift	count is greater than or equal to  the
	   bit width of	the type.  This	warning	is enabled by default.

       -Wshift-negative-value
	   Warn	if left	shifting a negative value.  This warning is enabled by
	   -Wextra in C99 (and newer) and C++11	to C++17 modes.

       -Wno-shift-overflow
       -Wshift-overflow=n
	   These options control warnings about	left shift overflows.

	   -Wshift-overflow=1
	       This is the warning level of -Wshift-overflow and is enabled by
	       default in C99 and C++11	modes (and newer).  This warning level
	       does  not  warn	about  left-shifting  1	 into  the  sign  bit.
	       (However, in C, such an overflow	is still rejected in  contexts
	       where  an integer constant expression is	required.)  No warning
	       is emitted in C++20 mode	(and newer),  as  signed  left	shifts
	       always wrap.

	   -Wshift-overflow=2
	       This  warning  level  also warns	about left-shifting 1 into the
	       sign bit, unless	C++14 mode (or newer) is active.

       -Wswitch
	   Warn	whenever a "switch" statement has an index of enumerated  type
	   and	lacks  a  "case"  for  one  or more of the named codes of that
	   enumeration.	 (The presence of  a  "default"	 label	prevents  this
	   warning.)  "case" labels outside the	enumeration range also provoke
	   warnings  when  this	 option	 is used (even if there	is a "default"
	   label).  This warning is enabled by -Wall.

       -Wswitch-default
	   Warn	whenever a "switch" statement does not have a "default"	case.

       -Wswitch-enum
	   Warn	whenever a "switch" statement has an index of enumerated  type
	   and	lacks  a  "case"  for  one  or more of the named codes of that
	   enumeration.	 "case"	labels	outside	 the  enumeration  range  also
	   provoke  warnings  when  this  option is used.  The only difference
	   between -Wswitch and	this  option  is  that	this  option  gives  a
	   warning  about  an  omitted	enumeration  code  even	 if there is a
	   "default" label.

       -Wno-switch-bool
	   Do not warn when a "switch" statement has an	index of boolean  type
	   and the case	values are outside the range of	a boolean type.	 It is
	   possible  to	 suppress  this	 warning  by  casting  the controlling
	   expression to a type	other than "bool".  For	example:

		   switch ((int) (a == 4))
		     {
		     ...
		     }

	   This	warning	is enabled by default for C and	C++ programs.

       -Wno-switch-outside-range
	   This	option controls	warnings when a	"switch" case has a value that
	   is outside of its respective	type range.  This warning  is  enabled
	   by default for C and	C++ programs.

       -Wno-switch-unreachable
	   Do  not  warn when a	"switch" statement contains statements between
	   the controlling expression and the first  case  label,  which  will
	   never be executed.  For example:

		   switch (cond)
		     {
		      i	= 15;
		     ...
		      case 5:
		     ...
		     }

	   -Wswitch-unreachable	 does  not  warn  if the statement between the
	   controlling	expression  and	 the  first  case  label  is  just   a
	   declaration:

		   switch (cond)
		     {
		      int i;
		     ...
		      case 5:
		      i	= 5;
		     ...
		     }

	   This	warning	is enabled by default for C and	C++ programs.

       -Wsync-nand (C and C++ only)
	   Warn	  when	 "__sync_fetch_and_nand"  and  "__sync_nand_and_fetch"
	   built-in functions are used.	 These functions changed semantics  in
	   GCC 4.4.

       -Wunused-but-set-parameter
	   Warn	 whenever  a  function parameter is assigned to, but otherwise
	   unused (aside from its declaration).

	   To suppress this warning use	the "unused" attribute.

	   This	warning	is also	enabled	by -Wunused together with -Wextra.

       -Wunused-but-set-variable
	   Warn	whenever a local variable is assigned to, but otherwise	unused
	   (aside from its declaration).  This warning is enabled by -Wall.

	   To suppress this warning use	the "unused" attribute.

	   This	warning	is also	enabled	 by  -Wunused,	which  is  enabled  by
	   -Wall.

       -Wunused-function
	   Warn	 whenever  a  static function is declared but not defined or a
	   non-inline static function is unused.  This warning is  enabled  by
	   -Wall.

       -Wunused-label
	   Warn	 whenever  a  label is declared	but not	used.  This warning is
	   enabled by -Wall.

	   To suppress this warning use	the "unused" attribute.

       -Wunused-local-typedefs (C, Objective-C,	C++ and	Objective-C++ only)
	   Warn	when a typedef locally defined in  a  function	is  not	 used.
	   This	warning	is enabled by -Wall.

       -Wunused-parameter
	   Warn	 whenever  a  function	parameter  is  unused  aside  from its
	   declaration.

	   To suppress this warning use	the "unused" attribute.

       -Wno-unused-result
	   Do not warn if  a  caller  of  a  function  marked  with  attribute
	   "warn_unused_result"	 does not use its return value.	The default is
	   -Wunused-result.

       -Wunused-variable
	   Warn	whenever a local or static variable is unused aside  from  its
	   declaration.	 This  option implies -Wunused-const-variable=1	for C,
	   but not for C++. This warning is enabled by -Wall.

	   To suppress this warning use	the "unused" attribute.

       -Wunused-const-variable
       -Wunused-const-variable=n
	   Warn	whenever a constant static variable is unused aside  from  its
	   declaration.	     -Wunused-const-variable=1	   is	 enabled    by
	   -Wunused-variable for C, but	 not  for  C++.	 In  C	this  declares
	   variable  storage,  but  in	C++  this  is not an error since const
	   variables take the place of "#define"s.

	   To suppress this warning use	the "unused" attribute.

	   -Wunused-const-variable=1
	       This is the warning level that is enabled by  -Wunused-variable
	       for  C.	 It  warns  only  about	 unused	static const variables
	       defined in the main compilation	unit,  but  not	 about	static
	       const variables declared	in any header included.

	   -Wunused-const-variable=2
	       This  warning  level  also  warns  for  unused  constant	static
	       variables in headers (excluding system headers).	 This  is  the
	       warning level of	-Wunused-const-variable	and must be explicitly
	       requested since in C++ this isn't an error and in C it might be
	       harder to clean up all headers included.

       -Wunused-value
	   Warn	 whenever a statement computes a result	that is	explicitly not
	   used. To suppress  this  warning  cast  the	unused	expression  to
	   "void". This	includes an expression-statement or the	left-hand side
	   of  a  comma	expression that	contains no side effects. For example,
	   an  expression  such	 as   "x[i,j]"	 causes	  a   warning,	 while
	   "x[(void)i,j]" does not.

	   This	warning	is enabled by -Wall.

       -Wunused
	   All the above -Wunused options combined.

	   In  order  to get a warning about an	unused function	parameter, you
	   must	either specify	-Wextra	 -Wunused  (note  that	-Wall  implies
	   -Wunused), or separately specify -Wunused-parameter.

       -Wuninitialized
	   Warn	 if  an	object with automatic or allocated storage duration is
	   used	without	having been initialized.  In C++, also warn if a  non-
	   static  reference  or  non-static "const" member appears in a class
	   without constructors.

	   In addition,	passing	a pointer (or  in  C++,	 a  reference)	to  an
	   uninitialized  object to a "const"-qualified	argument of a built-in
	   function known to  read  the	 object	 is  also  diagnosed  by  this
	   warning.  (-Wmaybe-uninitialized is issued for ordinary functions.)

	   If you want to warn about code that uses the	uninitialized value of
	   the variable	in its own initializer,	use the	-Winit-self option.

	   These  warnings  occur  for	individual  uninitialized  elements of
	   structure, union or array variables as well as for  variables  that
	   are	uninitialized  as a whole.  They do not	occur for variables or
	   elements declared "volatile".  Because  these  warnings  depend  on
	   optimization,  the  exact variables or elements for which there are
	   warnings depend on the precise optimization options and version  of
	   GCC used.

	   Note	 that  there  may  be no warning about a variable that is used
	   only	to compute a value that	itself is  never  used,	 because  such
	   computations	 may  be  deleted  by  data  flow  analysis before the
	   warnings are	printed.

       -Wno-invalid-memory-model
	   This	option controls	warnings for invocations of __atomic Builtins,
	   __sync Builtins, and	the C11	atomic generic functions with a	memory
	   consistency argument	that is	either invalid for  the	 operation  or
	   outside the range of	values of the "memory_order" enumeration.  For
	   example,  since  the	"__atomic_store" and "__atomic_store_n"	built-
	   ins are only	defined	for the	 relaxed,  release,  and  sequentially
	   consistent memory orders the	following code is diagnosed:

		   void	store (int *i)
		   {
		     __atomic_store_n (i, 0, memory_order_consume);
		   }

	   -Winvalid-memory-model is enabled by	default.

       -Wmaybe-uninitialized
	   For	an  object  with  automatic  or	allocated storage duration, if
	   there exists	a path from the	function entry to a use	of the	object
	   that	is initialized,	but there exist	some other paths for which the
	   object  is  not  initialized,  the  compiler	 emits a warning if it
	   cannot prove	the uninitialized paths	are not	executed at run	time.

	   In addition,	passing	a pointer (or  in  C++,	 a  reference)	to  an
	   uninitialized  object  to  a	"const"-qualified function argument is
	   also	diagnosed by this warning.   (-Wuninitialized  is  issued  for
	   built-in  functions	known  to  read	 the  object.)	Annotating the
	   function with attribute "access (none)" indicates that the argument
	   isn't used to access	the object and avoids the warning.

	   These warnings are only possible in optimizing compilation, because
	   otherwise GCC does not keep track of	the state of variables.

	   These warnings are made optional because GCC	may  not  be  able  to
	   determine when the code is correct in spite of appearing to have an
	   error.  Here	is one example of how this can happen:

		   {
		     int x;
		     switch (y)
		       {
		       case 1: x = 1;
			 break;
		       case 2: x = 4;
			 break;
		       case 3: x = 5;
		       }
		     foo (x);
		   }

	   If  the  value  of  "y"  is	always	1,  2 or 3, then "x" is	always
	   initialized,	but GCC	doesn't	know this. To  suppress	 the  warning,
	   you need to provide a default case with assert(0) or	similar	code.

	   This	option also warns when a non-volatile automatic	variable might
	   be  changed	by  a  call  to	"longjmp".  The	compiler sees only the
	   calls to "setjmp".  It cannot know where "longjmp" will be  called;
	   in  fact,  a	signal handler could call it at	any point in the code.
	   As a	result,	you may	get a warning even when	there is  in  fact  no
	   problem  because  "longjmp"	cannot	in fact	be called at the place
	   that	would cause a problem.

	   Some	spurious warnings can  be  avoided  if	you  declare  all  the
	   functions you use that never	return as "noreturn".

	   This	warning	is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
	   Warn	 when  a  "#pragma"  directive	is  encountered	 that  is  not
	   understood by GCC.  If this command-line option is  used,  warnings
	   are	even  issued for unknown pragmas in system header files.  This
	   is not the case if the warnings  are	 only  enabled	by  the	 -Wall
	   command-line	option.

       -Wno-pragmas
	   Do not warn about misuses of	pragmas, such as incorrect parameters,
	   invalid   syntax,   or   conflicts	between	  pragmas.   See  also
	   -Wunknown-pragmas.

       -Wno-prio-ctor-dtor
	   Do not warn if a priority from 0 to 100 is used for constructor  or
	   destructor.	The use	of constructor and destructor attributes allow
	   you	to  assign a priority to the constructor/destructor to control
	   its order of	execution before "main"	is called or after it returns.
	   The priority	values must  be	 greater  than	100  as	 the  compiler
	   reserves priority values between 0--100 for the implementation.

       -Wstrict-aliasing
	   This	 option	 is  only active when -fstrict-aliasing	is active.  It
	   warns about code that might break the strict	 aliasing  rules  that
	   the compiler	is using for optimization.  The	warning	does not catch
	   all	cases, but does	attempt	to catch the more common pitfalls.  It
	   is included in -Wall.  It is	equivalent to -Wstrict-aliasing=3

       -Wstrict-aliasing=n
	   This	option is only active when -fstrict-aliasing  is  active.   It
	   warns  about	 code  that might break	the strict aliasing rules that
	   the compiler	is using for optimization.  Higher  levels  correspond
	   to  higher  accuracy	 (fewer	 false positives).  Higher levels also
	   correspond  to  more	 effort,  similar  to  the   way   -O	works.
	   -Wstrict-aliasing is	equivalent to -Wstrict-aliasing=3.

	   Level  1:  Most aggressive, quick, least accurate.  Possibly	useful
	   when	higher levels do not warn but -fstrict-aliasing	 still	breaks
	   the code, as	it has very few	false negatives.  However, it has many
	   false   positives.	Warns  for  all	 pointer  conversions  between
	   possibly incompatible types,	even if	never dereferenced.   Runs  in
	   the front end only.

	   Level  2:  Aggressive, quick, not too precise.  May still have many
	   false positives (not	as many	as level  1  though),  and  few	 false
	   negatives  (but  possibly  more  than level 1).  Unlike level 1, it
	   only	warns when an address is taken.	 Warns about incomplete	types.
	   Runs	in the front end only.

	   Level 3 (default for	-Wstrict-aliasing): Should have	very few false
	   positives and few false negatives.  Slightly	slower than  levels  1
	   or  2  when	optimization  is  enabled.   Takes  care of the	common
	   pun+dereference pattern in the front	end: "*(int*)&some_float".  If
	   optimization	is enabled, it also runs in the	 back  end,  where  it
	   deals  with multiple	statement cases	using flow-sensitive points-to
	   information.	  Only	 warns	 when	the   converted	  pointer   is
	   dereferenced.  Does not warn	about incomplete types.

       -Wstrict-overflow
       -Wstrict-overflow=n
	   This	 option	 is only active	when signed overflow is	undefined.  It
	   warns about	cases  where  the  compiler  optimizes	based  on  the
	   assumption  that signed overflow does not occur.  Note that it does
	   not warn about all cases where the code  might  overflow:  it  only
	   warns  about	cases where the	compiler implements some optimization.
	   Thus	this warning depends on	the optimization level.

	   An optimization that	assumes	that signed overflow does not occur is
	   perfectly safe if the values	of the	variables  involved  are  such
	   that	 overflow  never does, in fact,	occur.	Therefore this warning
	   can easily give a false positive: a warning about code that is  not
	   actually  a	problem.   To  help focus on important issues, several
	   warning levels are defined.	No warnings are	issued for the use  of
	   undefined  signed  overflow	when  estimating how many iterations a
	   loop	requires, in particular	when determining whether a  loop  will
	   be executed at all.

	   -Wstrict-overflow=1
	       Warn  about cases that are both questionable and	easy to	avoid.
	       For example the compiler	simplifies "x +	1 >  x"	 to  1.	  This
	       level  of  -Wstrict-overflow is enabled by -Wall; higher	levels
	       are not,	and must be explicitly requested.

	   -Wstrict-overflow=2
	       Also warn about other cases where a comparison is simplified to
	       a constant.  For	example: "abs (x) >= 0".   This	 can  only  be
	       simplified  when	 signed	integer	overflow is undefined, because
	       "abs (INT_MIN)" overflows to  "INT_MIN",	 which	is  less  than
	       zero.   -Wstrict-overflow  (with	 no  level)  is	 the  same  as
	       -Wstrict-overflow=2.

	   -Wstrict-overflow=3
	       Also warn about other cases where a comparison  is  simplified.
	       For example: "x + 1 > 1"	is simplified to "x > 0".

	   -Wstrict-overflow=4
	       Also  warn about	other simplifications not covered by the above
	       cases.  For example: "(x	* 10) /	5" is simplified to "x * 2".

	   -Wstrict-overflow=5
	       Also warn about cases where the compiler	reduces	the  magnitude
	       of  a constant involved in a comparison.	 For example: "x + 2 >
	       y" is simplified	to "x +	1 >= y".  This is reported only	at the
	       highest warning level because this  simplification  applies  to
	       many  comparisons,  so  this  warning  level gives a very large
	       number of false positives.

       -Wstring-compare
	   Warn	for calls to "strcmp" and "strncmp" whose result is determined
	   to be either	zero or	non-zero in tests for such equality  owing  to
	   the length of one argument being greater than the size of the array
	   the	other  argument	 is  stored  in	 (or  the bound	in the case of
	   "strncmp").	Such calls could be mistakes.  For example,  the  call
	   to  "strcmp"	 below	is diagnosed because its result	is necessarily
	   non-zero irrespective of the	contents of the	array "a".

		   extern char a[4];
		   void	f (char	*d)
		   {
		     strcpy (d,	"string");
		     ...
		     if	(0 == strcmp (a, d))   // cannot be true
		       puts ("a	and d are the same");
		   }

	   -Wstring-compare is enabled by -Wextra.

       -Wno-stringop-overflow
       -Wstringop-overflow
       -Wstringop-overflow=type
	   Warn	for calls to string manipulation functions  such  as  "memcpy"
	   and	"strcpy"  that	are  determined	 to  overflow  the destination
	   buffer.  The	optional argument is one  greater  than	 the  type  of
	   Object  Size	 Checking  to  perform	to  determine  the size	of the
	   destination.	 The argument is meaningful only  for  functions  that
	   operate  on	character arrays but not for raw memory	functions like
	   "memcpy" which always make use of Object Size type-0.   The	option
	   also	 warns	for calls that specify a size in excess	of the largest
	   possible object or at  most	"SIZE_MAX  /  2"  bytes.   The	option
	   produces  the best results with optimization	enabled	but can	detect
	   a small subset of simple buffer overflows even without optimization
	   in calls to the GCC built-in	functions like "__builtin_memcpy" that
	   correspond to the standard functions.   In  any  case,  the	option
	   warns  about	 just  a  subset  of  buffer overflows detected	by the
	   corresponding overflow checking built-ins.  For example, the	option
	   issues a warning for	the "strcpy" call below	because	it  copies  at
	   least  5  characters	 (the  string "blue" including the terminating
	   NUL)	into the buffer	of size	4.

		   enum	Color {	blue, purple, yellow };
		   const char* f (enum Color clr)
		   {
		     static char buf [4];
		     const char	*str;
		     switch (clr)
		       {
			 case blue: str	= "blue"; break;
			 case purple: str = "purple"; break;
			 case yellow: str = "yellow"; break;
		       }

		     return strcpy (buf, str);	 // warning here
		   }

	   Option -Wstringop-overflow=2	is enabled by default.

	   -Wstringop-overflow
	   -Wstringop-overflow=1
	       The -Wstringop-overflow=1 option	 uses  type-zero  Object  Size
	       Checking	 to  determine	the  sizes of destination objects.  At
	       this setting the	option does not	warn for writes	past  the  end
	       of subobjects of	larger objects accessed	by pointers unless the
	       size  of	 the  largest  surrounding  object is known.  When the
	       destination may be one of several objects it is assumed	to  be
	       the  largest  one of them.  On Linux systems, when optimization
	       is enabled at this setting the option warns for the  same  code
	       as  when	 the  "_FORTIFY_SOURCE"	macro is defined to a non-zero
	       value.

	   -Wstringop-overflow=2
	       The -Wstringop-overflow=2  option  uses	type-one  Object  Size
	       Checking	 to  determine	the  sizes of destination objects.  At
	       this setting the	option warns about overflows when  writing  to
	       members	of  the	 largest  complete objects whose exact size is
	       known.  However,	it does	not warn for excessive writes  to  the
	       same  members  of  unknown objects referenced by	pointers since
	       they  may  point	 to  arrays  containing	 unknown  numbers   of
	       elements.  This is the default setting of the option.

	   -Wstringop-overflow=3
	       The  -Wstringop-overflow=3  option  uses	 type-two  Object Size
	       Checking	to determine the sizes	of  destination	 objects.   At
	       this  setting  the  option warns	about overflowing the smallest
	       object or data member.  This is the most	restrictive setting of
	       the option that may result in warnings for safe code.

	   -Wstringop-overflow=4
	       The -Wstringop-overflow=4 option	uses  type-three  Object  Size
	       Checking	 to  determine	the  sizes of destination objects.  At
	       this setting  the  option  warns	 about	overflowing  any  data
	       members,	 and when the destination is one of several objects it
	       uses the	size of	the largest of them to decide whether to issue
	       a warning.  Similarly to	-Wstringop-overflow=3 this setting  of
	       the option may result in	warnings for benign code.

       -Wno-stringop-overread
	   Warn	 for  calls to string manipulation functions such as "memchr",
	   or "strcpy" that are	determined to read past	the end	of the	source
	   sequence.

	   Option -Wstringop-overread is enabled by default.

       -Wno-stringop-truncation
	   Do not warn for calls to bounded string manipulation	functions such
	   as "strncat", "strncpy", and	"stpncpy" that may either truncate the
	   copied string or leave the destination unchanged.

	   In  the  following example, the call	to "strncat" specifies a bound
	   that	is less	than the length	of the source string.	As  a  result,
	   the	copy  of  the  source  will  be	 truncated  and	so the call is
	   diagnosed.  To avoid	the warning use	"bufsize - strlen (buf)	-  1)"
	   as the bound.

		   void	append (char *buf, size_t bufsize)
		   {
		     strncat (buf, ".txt", 3);
		   }

	   As  another	example,  the  following  call to "strncpy" results in
	   copying to "d" just the characters preceding	the  terminating  NUL,
	   without  appending  the  NUL	 to  the  end.	Assuming the result of
	   "strncpy" is	 necessarily  a	 NUL-terminated	 string	 is  a	common
	   mistake,  and  so the call is diagnosed.  To	avoid the warning when
	   the result is not expected  to  be  NUL-terminated,	call  "memcpy"
	   instead.

		   void	copy (char *d, const char *s)
		   {
		     strncpy (d, s, strlen (s));
		   }

	   In  the following example, the call to "strncpy" specifies the size
	   of the destination buffer as	the  bound.   If  the  length  of  the
	   source  string  is equal to or greater than this size the result of
	   the copy will not be	NUL-terminated.	 Therefore, the	call  is  also
	   diagnosed.	To  avoid the warning, specify "sizeof buf - 1"	as the
	   bound and set the last element of the buffer	to "NUL".

		   void	copy (const char *s)
		   {
		     char buf[80];
		     strncpy (buf, s, sizeof buf);
		     ...
		   }

	   In situations where a  character  array  is	intended  to  store  a
	   sequence  of	 bytes	with no	terminating "NUL" such an array	may be
	   annotated with attribute "nonstring"	to avoid this  warning.	  Such
	   arrays,  however,  are  not	suitable  arguments  to	functions that
	   expect "NUL"-terminated strings.  To	help detect accidental misuses
	   of such arrays GCC issues warnings unless it	can prove that the use
	   is safe.

       -Wsuggest-attribute=[pure|const|noreturn|format|cold|malloc]
	   Warn	for cases where	adding an attribute  may  be  beneficial.  The
	   attributes currently	supported are listed below.

	   -Wsuggest-attribute=pure
	   -Wsuggest-attribute=const
	   -Wsuggest-attribute=noreturn
	   -Wmissing-noreturn
	   -Wsuggest-attribute=malloc
	       Warn  about  functions  that might be candidates	for attributes
	       "pure", "const" or "noreturn" or	"malloc".  The	compiler  only
	       warns  for  functions visible in	other compilation units	or (in
	       the case	of "pure" and "const") if it  cannot  prove  that  the
	       function	 returns  normally.  A function	returns	normally if it
	       doesn't contain	an  infinite  loop  or	return	abnormally  by
	       throwing,  calling "abort" or trapping.	This analysis requires
	       option -fipa-pure-const,	which is enabled by default at -O  and
	       higher.	Higher optimization levels improve the accuracy	of the
	       analysis.

	   -Wsuggest-attribute=format
	   -Wmissing-format-attribute
	       Warn  about  function  pointers	that  might  be	candidates for
	       "format"	attributes.  Note these	are only possible  candidates,
	       not  absolute  ones.   GCC  guesses that	function pointers with
	       "format"	  attributes   that   are    used    in	   assignment,
	       initialization,	parameter  passing or return statements	should
	       have a corresponding "format" attribute in the resulting	 type.
	       I.e.  the  left-hand  side of the assignment or initialization,
	       the type	of the parameter variable, or the return type  of  the
	       containing  function  respectively  should also have a "format"
	       attribute to avoid the warning.

	       GCC  also  warns	 about	function  definitions  that  might  be
	       candidates  for	"format"  attributes.	Again,	these are only
	       possible	candidates.   GCC  guesses  that  "format"  attributes
	       might  be  appropriate  for  any	function that calls a function
	       like "vprintf" or "vscanf", but this might not  always  be  the
	       case,  and  some	 functions  for	 which "format"	attributes are
	       appropriate may not be detected.

	   -Wsuggest-attribute=cold
	       Warn about  functions  that  might  be  candidates  for	"cold"
	       attribute.   This  is  based  on	static detection and generally
	       only warns about	functions which	always	leads  to  a  call  to
	       another	"cold"	function  such	as  wrappers of	C++ "throw" or
	       fatal error reporting functions leading to "abort".

       -Walloc-zero
	   Warn	about calls to allocation functions decorated  with  attribute
	   "alloc_size"	that specify zero bytes, including those to the	built-
	   in  forms  of  the  functions  "aligned_alloc", "alloca", "calloc",
	   "malloc", and "realloc".  Because the behavior of  these  functions
	   when	 called	with a zero size differs among implementations (and in
	   the case of "realloc" has been deprecated) relying on it may	result
	   in subtle portability bugs and should be avoided.

       -Walloc-size-larger-than=byte-size
	   Warn	about calls to functions decorated with	attribute "alloc_size"
	   that	attempt	to allocate objects larger than	the  specified	number
	   of bytes, or	where the result of the	size computation in an integer
	   type	 with infinite precision would exceed the value	of PTRDIFF_MAX
	   on the target.  -Walloc-size-larger-than=PTRDIFF_MAX	is enabled  by
	   default.   Warnings controlled by the option	can be disabled	either
	   by	specifying   byte-size	 of   SIZE_MAX	 or   more    or    by
	   -Wno-alloc-size-larger-than.

       -Wno-alloc-size-larger-than
	   Disable   -Walloc-size-larger-than=	 warnings.    The   option  is
	   equivalent to -Walloc-size-larger-than=SIZE_MAX or larger.

       -Walloca
	   This	option warns on	all uses of "alloca" in	the source.

       -Walloca-larger-than=byte-size
	   This	option warns on	calls to "alloca"  with	 an  integer  argument
	   whose value is either zero, or that is not bounded by a controlling
	   predicate  that  limits  its	 value	to at most byte-size.  It also
	   warns for calls to "alloca"	where  the  bound  value  is  unknown.
	   Arguments  of  non-integer  types  are considered unbounded even if
	   they	appear to be constrained to the	expected range.

	   For example,	a bounded case of "alloca" could be:

		   void	func (size_t n)
		   {
		     void *p;
		     if	(n <= 1000)
		       p = alloca (n);
		     else
		       p = malloc (n);
		     f (p);
		   }

	   In the above	example, passing "-Walloca-larger-than=1000" would not
	   issue a warning because the call to "alloca"	is known to be at most
	   1000	bytes.	However, if  "-Walloca-larger-than=500"	 were  passed,
	   the compiler	would emit a warning.

	   Unbounded  uses,  on	 the  other hand, are uses of "alloca" with no
	   controlling	predicate  constraining	 its  integer  argument.   For
	   example:

		   void	func ()
		   {
		     void *p = alloca (n);
		     f (p);
		   }

	   If  "-Walloca-larger-than=500" were passed, the above would trigger
	   a warning, but this time because of the lack	of bounds checking.

	   Note, that even seemingly correct code  involving  signed  integers
	   could cause a warning:

		   void	func (signed int n)
		   {
		     if	(n < 500)
		       {
			 p = alloca (n);
			 f (p);
		       }
		   }

	   In  the  above  example, n could be negative, causing a larger than
	   expected argument to	be implicitly cast into	the "alloca" call.

	   This	option also warns when "alloca"	is used	in a loop.

	   -Walloca-larger-than=PTRDIFF_MAX  is	 enabled  by  default  but  is
	   usually  only effective  when -ftree-vrp is active (default for -O2
	   and above).

	   See also -Wvla-larger-than=byte-size.

       -Wno-alloca-larger-than
	   Disable -Walloca-larger-than= warnings.  The	option	is  equivalent
	   to -Walloca-larger-than=SIZE_MAX or larger.

       -Warith-conversion
	   Do  warn about implicit conversions from arithmetic operations even
	   when	conversion of the operands to  the  same  type	cannot	change
	   their   values.    This   affects   warnings	  from	 -Wconversion,
	   -Wfloat-conversion, and -Wsign-conversion.

		   void	f (char	c, int i)
		   {
		     c = c + i;	// warns with B<-Wconversion>
		     c = c + 1;	// only	warns with B<-Warith-conversion>
		   }

       -Warray-bounds
       -Warray-bounds=n
	   This	option is only active when -ftree-vrp is active	 (default  for
	   -O2 and above). It warns about subscripts to	arrays that are	always
	   out of bounds. This warning is enabled by -Wall.

	   -Warray-bounds=1
	       This  is	 the warning level of -Warray-bounds and is enabled by
	       -Wall; higher levels are	not, and must be explicitly requested.

	   -Warray-bounds=2
	       This warning level also warns about out of  bounds  access  for
	       arrays  at  the end of a	struct and for arrays accessed through
	       pointers. This warning level may	give a larger number of	 false
	       positives and is	deactivated by default.

       -Warray-parameter
       -Warray-parameter=n
	   Warn	about redeclarations of	functions involving arguments of array
	   or  pointer	types  of  inconsistent	kinds or forms,	and enable the
	   detection of	out-of-bounds accesses to such parameters by  warnings
	   such	as -Warray-bounds.

	   If  the  first  function  declaration uses the array	form the bound
	   specified in	the array is assumed  to  be  the  minimum  number  of
	   elements  expected  to be provided in calls to the function and the
	   maximum number of elements accessed	by  it.	  Failing  to  provide
	   arguments  of  sufficient  size  or accessing more than the maximum
	   number  of  elements	 may  be  diagnosed  by	  warnings   such   as
	   -Warray-bounds.   At	 level 1 the warning diagnoses inconsistencies
	   involving array parameters declared using the "T[static N]" form.

	   For example,	the warning triggers for the following	redeclarations
	   because  the	 first one allows an array of any size to be passed to
	   "f" while the second	one with the keyword "static"  specifies  that
	   the array argument must have	at least four elements.

		   void	f (int[static 4]);
		   void	f (int[]);	     //	warning	(inconsistent array form)

		   void	g (void)
		   {
		     int *p = (int *)malloc (4);
		     f (p);		     //	warning	(array too small)
		     ...
		   }

	   At  level  2	the warning also triggers for redeclarations involving
	   any other inconsistency in array or pointer argument	forms denoting
	   array  sizes.   Pointers  and  arrays  of  unspecified  bound   are
	   considered equivalent and do	not trigger a warning.

		   void	g (int*);
		   void	g (int[]);     // no warning
		   void	g (int[8]);    // warning (inconsistent	array bound)

	   -Warray-parameter=2	is  included  in  -Wall.   The -Wvla-parameter
	   option triggers  warnings  for  similar  inconsistencies  involving
	   Variable Length Array arguments.

       -Wattribute-alias=n
       -Wno-attribute-alias
	   Warn	 about	declarations  using the	"alias"	and similar attributes
	   whose target	is incompatible	with the type of the alias.

	   -Wattribute-alias=1
	       The default  warning  level  of	the  -Wattribute-alias	option
	       diagnoses  incompatibilities  between  the  type	 of  the alias
	       declaration and that of its target.  Such incompatibilities are
	       typically indicative of bugs.

	   -Wattribute-alias=2
	       At this level -Wattribute-alias also diagnoses cases where  the
	       attributes  of  the alias declaration are more restrictive than
	       the attributes applied to its  target.	These  mismatches  can
	       potentially  result  in	incorrect  code	 generation.  In other
	       cases they may be benign	and could be resolved simply by	adding
	       the missing attribute to	the target.  For comparison,  see  the
	       -Wmissing-attributes  option,  which  controls diagnostics when
	       the alias declaration is	 less  restrictive  than  the  target,
	       rather than more	restrictive.

	       Attributes   considered	include	 "alloc_align",	 "alloc_size",
	       "cold",	 "const",   "hot",   "leaf",   "malloc",    "nonnull",
	       "noreturn",    "nothrow",    "pure",   "returns_nonnull",   and
	       "returns_twice".

	   -Wattribute-alias is	equivalent to  -Wattribute-alias=1.   This  is
	   the	 default.    You   can	disable	 these	warnings  with	either
	   -Wno-attribute-alias	or -Wattribute-alias=0.

       -Wbool-compare
	   Warn	about  boolean	expression  compared  with  an	integer	 value
	   different   from   "true"/"false".	For  instance,	the  following
	   comparison is always	false:

		   int n = 5;
		   ...
		   if ((n > 1) == 2) { ... }

	   This	warning	is enabled by -Wall.

       -Wbool-operation
	   Warn	about suspicious operations on expressions of a	boolean	 type.
	   For instance, bitwise negation of a boolean is very likely a	bug in
	   the	program.  For C, this warning also warns about incrementing or
	   decrementing	 a  boolean,  which  rarely  makes  sense.   (In  C++,
	   decrementing	 a  boolean is always invalid.	Incrementing a boolean
	   is invalid in C++17,	and deprecated otherwise.)

	   This	warning	is enabled by -Wall.

       -Wduplicated-branches
	   Warn	when an	if-else	has identical branches.	 This warning  detects
	   cases like

		   if (p != NULL)
		     return 0;
		   else
		     return 0;

	   It  doesn't	warn when both branches	contain	just a null statement.
	   This	warning	also warn for conditional operators:

		     int i = x ? *p : *p;

       -Wduplicated-cond
	   Warn	about duplicated  conditions  in  an  if-else-if  chain.   For
	   instance, warn for the following code:

		   if (p->q != NULL) { ... }
		   else	if (p->q != NULL) { ...	}

       -Wframe-address
	   Warn	 when  the __builtin_frame_address or __builtin_return_address
	   is called with an argument greater than 0.  Such calls  may	return
	   indeterminate values	or crash the program.  The warning is included
	   in -Wall.

       -Wno-discarded-qualifiers (C and	Objective-C only)
	   Do  not  warn  if  type qualifiers on pointers are being discarded.
	   Typically, the compiler warns if  a	"const	char  *"  variable  is
	   passed  to a	function that takes a "char *" parameter.  This	option
	   can be used to suppress such	a warning.

       -Wno-discarded-array-qualifiers (C and Objective-C only)
	   Do not warn if type qualifiers on arrays which are pointer  targets
	   are being discarded.	 Typically, the	compiler warns if a "const int
	   (*)[]"  variable  is	 passed	to a function that takes a "int	(*)[]"
	   parameter.  This option can be used to suppress such	a warning.

       -Wno-incompatible-pointer-types (C and Objective-C only)
	   Do not warn when there is a conversion between pointers  that  have
	   incompatible	 types.	  This	warning	 is  for  cases	not covered by
	   -Wno-pointer-sign, which warns  for	pointer	 argument  passing  or
	   assignment with different signedness.

       -Wno-int-conversion (C and Objective-C only)
	   Do  not  warn  about	incompatible integer to	pointer	and pointer to
	   integer conversions.	 This warning is about	implicit  conversions;
	   for	explicit conversions the warnings -Wno-int-to-pointer-cast and
	   -Wno-pointer-to-int-cast may	be used.

       -Wzero-length-bounds
	   Warn	about accesses to elements of zero-length array	 members  that
	   might overlap other members of the same object.  Declaring interior
	   zero-length	arrays	is  discouraged	 because  accesses to them are
	   undefined.  See

	   For example,	the first two stores in	function "bad"	are  diagnosed
	   because  the	 array elements	overlap	the subsequent members "b" and
	   "c".	 The third store is diagnosed by -Warray-bounds	because	it  is
	   beyond the bounds of	the enclosing object.

		   struct X { int a[0];	int b, c; };
		   struct X x;

		   void	bad (void)
		   {
		     x.a[0] = 0;   // -Wzero-length-bounds
		     x.a[1] = 1;   // -Wzero-length-bounds
		     x.a[2] = 2;   // -Warray-bounds
		   }

	   Option -Wzero-length-bounds is enabled by -Warray-bounds.

       -Wno-div-by-zero
	   Do not warn about compile-time integer division by zero.  Floating-
	   point  division  by	zero  is  not  warned  about,  as  it can be a
	   legitimate way of obtaining infinities and NaNs.

       -Wsystem-headers
	   Print warning messages for constructs found in system header	files.
	   Warnings from  system  headers  are	normally  suppressed,  on  the
	   assumption  that  they  usually  do	not indicate real problems and
	   would only make the compiler	output harder  to  read.   Using  this
	   command-line	 option	tells GCC to emit warnings from	system headers
	   as if they occurred in user code.  However, note that  using	 -Wall
	   in conjunction with this option does	not warn about unknown pragmas
	   in system headers---for that, -Wunknown-pragmas must	also be	used.

       -Wtautological-compare
	   Warn	 if a self-comparison always evaluates to true or false.  This
	   warning detects various mistakes such as:

		   int i = 1;
		   ...
		   if (i > i) {	... }

	   This	warning	also  warns  about  bitwise  comparisons  that	always
	   evaluate to true or false, for instance:

		   if ((a & 16)	== 10) { ... }

	   will	always be false.

	   This	warning	is enabled by -Wall.

       -Wtrampolines
	   Warn	 about trampolines generated for pointers to nested functions.
	   A trampoline	is a small piece of data or code that  is  created  at
	   run	time  on  the  stack  when the address of a nested function is
	   taken, and is used to call the  nested  function  indirectly.   For
	   some	 targets,  it  is  made	 up  of	data only and thus requires no
	   special treatment.  But, for	most targets, it is made  up  of  code
	   and	thus requires the stack	to be made executable in order for the
	   program to work properly.

       -Wfloat-equal
	   Warn	if floating-point values are used in equality comparisons.

	   The idea behind this	is that	sometimes it is	 convenient  (for  the
	   programmer)	to consider floating-point values as approximations to
	   infinitely precise real numbers.  If	you are	doing this,  then  you
	   need	 to  compute (by analyzing the code, or	in some	other way) the
	   maximum or likely maximum error that	 the  computation  introduces,
	   and	allow  for  it when performing comparisons (and	when producing
	   output, but that's a	different problem).  In	particular, instead of
	   testing for equality, you should  check  to	see  whether  the  two
	   values  have	 ranges	 that  overlap;	 and  this  is	done  with the
	   relational  operators,  so  equality	  comparisons	are   probably
	   mistaken.

       -Wtraditional (C	and Objective-C	only)
	   Warn	  about	  certain   constructs	 that  behave  differently  in
	   traditional and ISO C.  Also	warn about ISO C constructs that  have
	   no  traditional  C  equivalent,  and/or problematic constructs that
	   should be avoided.

	   *   Macro parameters	that appear  within  string  literals  in  the
	       macro  body.   In  traditional  C macro replacement takes place
	       within string literals, but in ISO C it does not.

	   *   In traditional C, some preprocessor directives did  not	exist.
	       Traditional  preprocessors  only	 considered  a	line  to  be a
	       directive if the	# appeared in column 1 on the line.  Therefore
	       -Wtraditional  warns  about  directives	that   traditional   C
	       understands  but	 ignores  because the #	does not appear	as the
	       first character	on  the	 line.	 It  also  suggests  you  hide
	       directives  like	 "#pragma"  not	understood by traditional C by
	       indenting  them.	  Some	traditional  implementations  do   not
	       recognize   "#elif",   so  this	option	suggests  avoiding  it
	       altogether.

	   *   A function-like macro that appears without arguments.

	   *   The unary plus operator.

	   *   The U integer constant suffix, or the  F	 or  L	floating-point
	       constant	suffixes.  (Traditional	C does support the L suffix on
	       integer	constants.)   Note,  these  suffixes  appear in	macros
	       defined in the system headers of	most modern systems, e.g.  the
	       _MIN/_MAX  macros in "<limits.h>".  Use of these	macros in user
	       code might normally lead	to spurious  warnings,	however	 GCC's
	       integrated  preprocessor	has enough context to avoid warning in
	       these cases.

	   *   A function declared external in one block and then  used	 after
	       the end of the block.

	   *   A "switch" statement has	an operand of type "long".

	   *   A  non-"static"	function  declaration  follows a "static" one.
	       This construct is not accepted by some traditional C compilers.

	   *   The ISO type of an integer constant has a  different  width  or
	       signedness  from	 its  traditional  type.  This warning is only
	       issued if the base of the constant is ten.  I.e.	hexadecimal or
	       octal values, which typically represent bit patterns,  are  not
	       warned about.

	   *   Usage of	ISO string concatenation is detected.

	   *   Initialization of automatic aggregates.

	   *   Identifier  conflicts  with  labels.   Traditional  C  lacks  a
	       separate	namespace for labels.

	   *   Initialization of unions.  If  the  initializer	is  zero,  the
	       warning is omitted.  This is done under the assumption that the
	       zero  initializer  in  user  code  appears  conditioned on e.g.
	       "__STDC__" to avoid missing initializer warnings	and relies  on
	       default initialization to zero in the traditional C case.

	   *   Conversions  by	prototypes between fixed/floating-point	values
	       and vice	versa.	The absence of these prototypes	when compiling
	       with traditional	C causes serious problems.  This is  a	subset
	       of  the	possible  conversion  warnings;	 for  the full set use
	       -Wtraditional-conversion.

	   *   Use  of	ISO  C	style  function	 definitions.	This   warning
	       intentionally  is  not  issued  for  prototype  declarations or
	       variadic	functions because these	ISO C features appear in  your
	       code when using libiberty's traditional C compatibility macros,
	       "PARAMS"	 and  "VPARAMS".   This	 warning  is also bypassed for
	       nested  functions  because  that	 feature  is  already  a   GCC
	       extension and thus not relevant to traditional C	compatibility.

       -Wtraditional-conversion	(C and Objective-C only)
	   Warn	if a prototype causes a	type conversion	that is	different from
	   what	 would	happen	to  the	 same  argument	 in  the  absence of a
	   prototype.  This includes conversions of fixed  point  to  floating
	   and vice versa, and conversions changing the	width or signedness of
	   a  fixed-point  argument  except  when  the	same  as  the  default
	   promotion.

       -Wdeclaration-after-statement (C	and Objective-C	only)
	   Warn	when a declaration is found after  a  statement	 in  a	block.
	   This	 construct, known from C++, was	introduced with	ISO C99	and is
	   by default allowed in GCC.  It is not supported by ISO C90.

       -Wshadow
	   Warn	whenever a local variable or type declaration shadows  another
	   variable,  parameter,  type,	 class	member	(in  C++), or instance
	   variable (in	 Objective-C)  or  whenever  a	built-in  function  is
	   shadowed.  Note that	in C++,	the compiler warns if a	local variable
	   shadows   an	  explicit   typedef,	but   not   if	it  shadows  a
	   struct/class/enum.  If this warning is enabled,  it	includes  also
	   all	  instances    of    local   shadowing.	   This	  means	  that
	   -Wno-shadow=local and -Wno-shadow=compatible-local are ignored when
	   -Wshadow is used.  Same as -Wshadow=global.

       -Wno-shadow-ivar	(Objective-C only)
	   Do not warn whenever	a local	variable shadows an instance  variable
	   in an Objective-C method.

       -Wshadow=global
	   Warn	for any	shadowing.  Same as -Wshadow.

       -Wshadow=local
	   Warn	 when  a  local	 variable  shadows  another  local variable or
	   parameter.

       -Wshadow=compatible-local
	   Warn	when a	local  variable	 shadows  another  local  variable  or
	   parameter  whose  type  is  compatible  with	 that of the shadowing
	   variable.  In C++, type compatibility here means the	 type  of  the
	   shadowing  variable	can  be	 converted  to	that  of  the shadowed
	   variable.   The   creation	of   this   flag   (in	 addition   to
	   -Wshadow=local)  is	based  on  the idea that when a	local variable
	   shadows another  one	 of  incompatible  type,  it  is  most	likely
	   intentional,	not a bug or typo, as shown in the following example:

		   for (SomeIterator i = SomeObj.begin(); i != SomeObj.end(); ++i)
		   {
		     for (int i	= 0; i < N; ++i)
		     {
		       ...
		     }
		     ...
		   }

	   Since  the  two variable "i"	in the example above have incompatible
	   types, enabling only	 -Wshadow=compatible-local  does  not  emit  a
	   warning.   Because  their  types  are incompatible, if a programmer
	   accidentally	uses one in place  of  the  other,  type  checking  is
	   expected  to	 catch that and	emit an	error or warning.  Use of this
	   flag	instead	of -Wshadow=local can possibly reduce  the  number  of
	   warnings  triggered	by intentional shadowing.  Note	that this also
	   means that shadowing	"const char *i"	by "char *i" does not  emit  a
	   warning.

	   This	warning	is also	enabled	by -Wshadow=local.

       -Wlarger-than=byte-size
	   Warn	 whenever  an  object is defined whose size exceeds byte-size.
	   -Wlarger-than=PTRDIFF_MAX  is   enabled   by	  default.    Warnings
	   controlled by the option can	be disabled either by specifying byte-
	   size	of SIZE_MAX or more or by -Wno-larger-than.

	   Also	 warn  for  calls  to  bounded	functions  such	as "memchr" or
	   "strnlen" that specify a bound greater than	the  largest  possible
	   object,  which is PTRDIFF_MAX bytes by default.  These warnings can
	   only	be disabled by -Wno-larger-than.

       -Wno-larger-than
	   Disable -Wlarger-than=  warnings.   The  option  is	equivalent  to
	   -Wlarger-than=SIZE_MAX or larger.

       -Wframe-larger-than=byte-size
	   Warn	 if  the  size	of  a  function	 frame exceeds byte-size.  The
	   computation done to determine the stack frame size  is  approximate
	   and	not  conservative.   The  actual  requirements may be somewhat
	   greater than	byte-size even if  you	do  not	 get  a	 warning.   In
	   addition, any space allocated via "alloca", variable-length arrays,
	   or  related	constructs  is	not  included  by  the	compiler  when
	   determining	  whether    or	   not	  to	issue	 a    warning.
	   -Wframe-larger-than=PTRDIFF_MAX  is	enabled	 by default.  Warnings
	   controlled by the option can	be disabled either by specifying byte-
	   size	of SIZE_MAX or more or by -Wno-frame-larger-than.

       -Wno-frame-larger-than
	   Disable -Wframe-larger-than=	warnings.  The option is equivalent to
	   -Wframe-larger-than=SIZE_MAX	or larger.

       -Wno-free-nonheap-object
	   Warn	when attempting	to deallocate an object	that  was  either  not
	   allocated  on the heap, or by using a pointer that was not returned
	   from	a prior	call to	the corresponding  allocation  function.   For
	   example,  because  the  call	 to  "stpcpy" returns a	pointer	to the
	   terminating nul character and not to	the begginning of the  object,
	   the call to "free" below is diagnosed.

		   void	f (char	*p)
		   {
		     p = stpcpy	(p, "abc");
		     //	...
		     free (p);	 // warning
		   }

	   -Wfree-nonheap-object is enabled by default.

       -Wstack-usage=byte-size
	   Warn	 if the	stack usage of a function might	exceed byte-size.  The
	   computation done to determine the stack usage is conservative.  Any
	   space allocated via "alloca", variable-length  arrays,  or  related
	   constructs  is included by the compiler when	determining whether or
	   not to issue	a warning.

	   The message is in keeping with the output of	-fstack-usage.

	   *   If the stack usage is fully static but  exceeds	the  specified
	       amount, it's:

			 warning: stack	usage is 1120 bytes

	   *   If the stack usage is (partly) dynamic but bounded, it's:

			 warning: stack	usage might be 1648 bytes

	   *   If the stack usage is (partly) dynamic and not bounded, it's:

			 warning: stack	usage might be unbounded

	   -Wstack-usage=PTRDIFF_MAX   is   enabled   by   default.   Warnings
	   controlled by the option can	be disabled either by specifying byte-
	   size	of SIZE_MAX or more or by -Wno-stack-usage.

       -Wno-stack-usage
	   Disable -Wstack-usage=  warnings.   The  option  is	equivalent  to
	   -Wstack-usage=SIZE_MAX or larger.

       -Wunsafe-loop-optimizations
	   Warn	 if  the  loop cannot be optimized because the compiler	cannot
	   assume  anything  on	 the  bounds  of  the  loop   indices.	  With
	   -funsafe-loop-optimizations	 warn	if  the	 compiler  makes  such
	   assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
	   When	used in	combination with -Wformat and  -pedantic  without  GNU
	   extensions,	 this  option  disables	 the  warnings	about  non-ISO
	   "printf" / "scanf" format width specifiers "I32",  "I64",  and  "I"
	   used	on Windows targets, which depend on the	MS runtime.

       -Wpointer-arith
	   Warn	 about	anything that depends on the "size of" a function type
	   or of "void".   GNU	C  assigns  these  types  a  size  of  1,  for
	   convenience	in calculations	with "void *" pointers and pointers to
	   functions.  In C++, warn also when an arithmetic operation involves
	   "NULL".  This warning is also enabled by -Wpedantic.

       -Wno-pointer-compare
	   Do not warn	if  a  pointer	is  compared  with  a  zero  character
	   constant.   This  usually  means  that  the pointer was meant to be
	   dereferenced.  For example:

		   const char *p = foo ();
		   if (p == '\0')
		     return 42;

	   Note	that the code above is invalid in C++11.

	   This	warning	is enabled by default.

       -Wtsan
	   Warn	about unsupported features in ThreadSanitizer.

	   ThreadSanitizer does	not support "std::atomic_thread_fence" and can
	   report false	positives.

	   This	warning	is enabled by default.

       -Wtype-limits
	   Warn	if a comparison	is always true or  always  false  due  to  the
	   limited  range  of  the  data  type,	 but  do not warn for constant
	   expressions.	 For example, warn if an unsigned variable is compared
	   against zero	with "<" or ">=".  This	warning	 is  also  enabled  by
	   -Wextra.

       -Wabsolute-value	(C and Objective-C only)
	   Warn	 for  calls  to	 standard  functions that compute the absolute
	   value of an argument	when a more appropriate	standard  function  is
	   available.	For  example, calling "abs(3.14)" triggers the warning
	   because the appropriate function to call to	compute	 the  absolute
	   value  of  a	 double	 argument is "fabs".  The option also triggers
	   warnings when the argument in a call	to  such  a  function  has  an
	   unsigned  type.   This  warning  can	be suppressed with an explicit
	   type	cast and it is also enabled by -Wextra.

       -Wcomment
       -Wcomments
	   Warn	whenever a comment-start sequence /* appears in	a /*  comment,
	   or  whenever	 a  backslash-newline  appears	in a //	comment.  This
	   warning is enabled by -Wall.

       -Wtrigraphs
	   Warn	if any trigraphs are encountered that might change the meaning
	   of the program.  Trigraphs within comments are  not	warned	about,
	   except those	that would form	escaped	newlines.

	   This	 option	 is  implied  by  -Wall.   If -Wall is not given, this
	   option is still enabled  unless  trigraphs  are  enabled.   To  get
	   trigraph  conversion	 without  warnings,  but  get  the other -Wall
	   warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wundef
	   Warn	if an undefined	identifier is evaluated	in an "#if" directive.
	   Such	identifiers are	replaced with zero.

       -Wexpansion-to-defined
	   Warn	whenever defined is encountered	in the expansion  of  a	 macro
	   (including  the  case  where	 the  macro  is	 expanded  by  an  #if
	   directive).	Such usage is not  portable.   This  warning  is  also
	   enabled by -Wpedantic and -Wextra.

       -Wunused-macros
	   Warn	 about	macros	defined	 in  the main file that	are unused.  A
	   macro is used if it is expanded or tested for  existence  at	 least
	   once.   The	preprocessor also warns	if the macro has not been used
	   at the time it is redefined or undefined.

	   Built-in macros, macros defined on the  command  line,  and	macros
	   defined in include files are	not warned about.

	   Note:  If  a	 macro	is  actually  used,  but  only used in skipped
	   conditional blocks, then the	preprocessor reports it	as unused.  To
	   avoid the warning in	such a case, you might improve	the  scope  of
	   the	macro's	 definition  by, for example, moving it	into the first
	   skipped block.  Alternatively, you could provide a dummy  use  with
	   something like:

		   #if defined the_macro_causing_the_warning
		   #endif

       -Wno-endif-labels
	   Do  not  warn  whenever  an	"#else"	or an "#endif" are followed by
	   text.  This sometimes happens in older programs with	 code  of  the
	   form

		   #if FOO
		   ...
		   #else FOO
		   ...
		   #endif FOO

	   The	second and third "FOO" should be in comments.  This warning is
	   on by default.

       -Wbad-function-cast (C and Objective-C only)
	   Warn	when a function	call is	cast  to  a  non-matching  type.   For
	   example,  warn if a call to a function returning an integer type is
	   cast	to a pointer type.

       -Wc90-c99-compat	(C and Objective-C only)
	   Warn	about features not present in ISO C90, but present in ISO C99.
	   For instance, warn about use	of variable length arrays, "long long"
	   type, "bool"	type, compound literals, designated initializers,  and
	   so on.  This	option is independent of the standards mode.  Warnings
	   are disabled	in the expression that follows "__extension__".

       -Wc99-c11-compat	(C and Objective-C only)
	   Warn	about features not present in ISO C99, but present in ISO C11.
	   For	instance,  warn	 about use of anonymous	structures and unions,
	   "_Atomic" type qualifier, "_Thread_local" storage-class  specifier,
	   "_Alignas"  specifier,  "Alignof" operator, "_Generic" keyword, and
	   so on.  This	option is independent of the standards mode.  Warnings
	   are disabled	in the expression that follows "__extension__".

       -Wc11-c2x-compat	(C and Objective-C only)
	   Warn	about features not present in ISO C11, but present in ISO C2X.
	   For instance, warn about omitting the string	 in  "_Static_assert",
	   use	of  [[]]  syntax for attributes, use of	decimal	floating-point
	   types, and so on.  This option  is  independent  of	the  standards
	   mode.   Warnings  are  disabled  in	the  expression	 that  follows
	   "__extension__".

       -Wc++-compat (C and Objective-C only)
	   Warn	about ISO C constructs that are	outside	of the	common	subset
	   of  ISO  C  and  ISO	C++, e.g. request for implicit conversion from
	   "void *" to a pointer to non-"void" type.

       -Wc++11-compat (C++ and Objective-C++ only)
	   Warn	about C++ constructs whose meaning  differs  between  ISO  C++
	   1998	 and  ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are
	   keywords in ISO C++ 2011.  This warning turns on -Wnarrowing	and is
	   enabled by -Wall.

       -Wc++14-compat (C++ and Objective-C++ only)
	   Warn	about C++ constructs whose meaning  differs  between  ISO  C++
	   2011	and ISO	C++ 2014.  This	warning	is enabled by -Wall.

       -Wc++17-compat (C++ and Objective-C++ only)
	   Warn	 about	C++  constructs	 whose meaning differs between ISO C++
	   2014	and ISO	C++ 2017.  This	warning	is enabled by -Wall.

       -Wc++20-compat (C++ and Objective-C++ only)
	   Warn	about C++ constructs whose meaning  differs  between  ISO  C++
	   2017	and ISO	C++ 2020.  This	warning	is enabled by -Wall.

       -Wcast-qual
	   Warn	 whenever  a  pointer is cast so as to remove a	type qualifier
	   from	the target type.  For example, warn if a  "const  char	*"  is
	   cast	to an ordinary "char *".

	   Also	warn when making a cast	that introduces	a type qualifier in an
	   unsafe  way.	  For example, casting "char **" to "const char	**" is
	   unsafe, as in this example:

		     /*	p is char ** value.  */
		     const char	**q = (const char **) p;
		     /*	Assignment of readonly string to const char * is OK.  */
		     *q	= "string";
		     /*	Now char** pointer points to read-only memory.	*/
		     **p = 'b';

       -Wcast-align
	   Warn	whenever a pointer is cast such	that the required alignment of
	   the target is increased.  For example, warn if a "char *"  is  cast
	   to  an  "int	 *" on machines	where integers can only	be accessed at
	   two-	or four-byte boundaries.

       -Wcast-align=strict
	   Warn	whenever a pointer is cast such	that the required alignment of
	   the target is increased.  For example, warn if a "char *"  is  cast
	   to an "int *" regardless of the target machine.

       -Wcast-function-type
	   Warn	 when  a  function pointer is cast to an incompatible function
	   pointer.  In	a  cast	 involving  function  types  with  a  variable
	   argument list only the types	of initial arguments that are provided
	   are	considered.   Any  parameter of	pointer-type matches any other
	   pointer-type.   Any	benign	differences  in	 integral  types   are
	   ignored,  like  "int"  vs.  "long" on ILP32 targets.	 Likewise type
	   qualifiers are ignored.  The	function type  "void  (*)  (void)"  is
	   special  and	matches	everything, which can be used to suppress this
	   warning.  In	a cast involving pointer to member types this  warning
	   warns  whenever  the	 type  cast  is	changing the pointer to	member
	   type.  This warning is enabled by -Wextra.

       -Wwrite-strings
	   When	 compiling  C,	give  string   constants   the	 type	"const
	   char[length]" so that copying the address of	one into a non-"const"
	   "char  *" pointer produces a	warning.  These	warnings help you find
	   at compile time code	that can try to	write into a string  constant,
	   but	only  if  you  have  been  very	careful	about using "const" in
	   declarations	and prototypes.	 Otherwise, it	is  just  a  nuisance.
	   This	is why we did not make -Wall request these warnings.

	   When	 compiling  C++,  warn	about  the  deprecated conversion from
	   string literals to "char *".	 This warning is  enabled  by  default
	   for C++ programs.

       -Wclobbered
	   Warn	 for  variables	that might be changed by "longjmp" or "vfork".
	   This	warning	is also	enabled	by -Wextra.

       -Wconversion
	   Warn	for implicit conversions that may alter	a value. This includes
	   conversions between real and	integer, like "abs (x)"	 when  "x"  is
	   "double";  conversions  between signed and unsigned,	like "unsigned
	   ui =	-1"; and conversions to	smaller	types, like "sqrtf (M_PI)". Do
	   not warn for	 explicit  casts  like	"abs  ((int)  x)"  and	"ui  =
	   (unsigned)  -1",  or	 if the	value is not changed by	the conversion
	   like	in "abs	(2.0)".	 Warnings about	conversions between signed and
	   unsigned integers can be disabled by	using -Wno-sign-conversion.

	   For C++, also warn for  confusing  overload	resolution  for	 user-
	   defined   conversions;  and	conversions  that  never  use  a  type
	   conversion operator:	conversions to "void", the same	type,  a  base
	   class  or  a	 reference to them. Warnings about conversions between
	   signed and unsigned integers	are disabled by	default	in C++	unless
	   -Wsign-conversion is	explicitly enabled.

	   Warnings  about  conversion from arithmetic on a small type back to
	   that	type are only given with -Warith-conversion.

       -Wdangling-else
	   Warn	about constructions where there	may be confusion to which "if"
	   statement an	"else" branch belongs.	Here is	an example of  such  a
	   case:

		   {
		     if	(a)
		       if (b)
			 foo ();
		     else
		       bar ();
		   }

	   In  C/C++,  every  "else"  branch belongs to	the innermost possible
	   "if"	statement, which in this example is "if	(b)".  This  is	 often
	   not	what  the  programmer  expected,  as  illustrated in the above
	   example by indentation the programmer chose.	  When	there  is  the
	   potential  for  this	confusion, GCC issues a	warning	when this flag
	   is specified.  To eliminate the warning, add	explicit braces	around
	   the innermost "if" statement	so there is  no	 way  the  "else"  can
	   belong to the enclosing "if".  The resulting	code looks like	this:

		   {
		     if	(a)
		       {
			 if (b)
			   foo ();
			 else
			   bar ();
		       }
		   }

	   This	warning	is enabled by -Wparentheses.

       -Wdate-time
	   Warn	 when  macros  "__TIME__",  "__DATE__"	or "__TIMESTAMP__" are
	   encountered as they might prevent  bit-wise-identical  reproducible
	   compilations.

       -Wempty-body
	   Warn	 if  an	 empty	body  occurs  in an "if", "else" or "do	while"
	   statement.  This warning is also enabled by -Wextra.

       -Wno-endif-labels
	   Do not warn about stray tokens after	"#else"	and "#endif".

       -Wenum-compare
	   Warn	about a	comparison  between  values  of	 different  enumerated
	   types.    In	  C++	enumerated   type  mismatches  in  conditional
	   expressions are also	 diagnosed  and	 the  warning  is  enabled  by
	   default.  In	C this warning is enabled by -Wall.

       -Wenum-conversion
	   Warn	 when  a value of enumerated type is implicitly	converted to a
	   different enumerated	type.  This warning is enabled by  -Wextra  in
	   C.

       -Wjump-misses-init (C, Objective-C only)
	   Warn	 if  a	"goto" statement or a "switch" statement jumps forward
	   across the initialization of	a variable, or	jumps  backward	 to  a
	   label  after	 the  variable	has been initialized.  This only warns
	   about variables that	are initialized	when they are declared.	  This
	   warning  is	only supported for C and Objective-C; in C++ this sort
	   of branch is	an error in any	case.

	   -Wjump-misses-init is included in -Wc++-compat.  It can be disabled
	   with	the -Wno-jump-misses-init option.

       -Wsign-compare
	   Warn	when a comparison between signed  and  unsigned	 values	 could
	   produce  an	incorrect result when the signed value is converted to
	   unsigned.  In C++, this warning is also enabled by -Wall.  In C, it
	   is also enabled by -Wextra.

       -Wsign-conversion
	   Warn	for implicit conversions  that	may  change  the  sign	of  an
	   integer  value,  like  assigning  a signed integer expression to an
	   unsigned integer variable. An explicit cast silences	 the  warning.
	   In C, this option is	enabled	also by	-Wconversion.

       -Wfloat-conversion
	   Warn	 for  implicit conversions that	reduce the precision of	a real
	   value.  This	includes conversions from real to  integer,  and  from
	   higher  precision real to lower precision real values.  This	option
	   is also enabled by -Wconversion.

       -Wno-scalar-storage-order
	   Do not warn	on  suspicious	constructs  involving  reverse	scalar
	   storage order.

       -Wsizeof-array-div
	   Warn	 about divisions of two	sizeof operators when the first	one is
	   applied to an array and the divisor does not	equal the size of  the
	   array  element.  In such a case, the	computation will not yield the
	   number of elements in the array, which  is  likely  what  the  user
	   intended.  This warning warns e.g. about

		   int fn ()
		   {
		     int arr[10];
		     return sizeof (arr) / sizeof (short);
		   }

	   This	warning	is enabled by -Wall.

       -Wsizeof-pointer-div
	   Warn	for suspicious divisions of two	sizeof expressions that	divide
	   the	pointer	 size  by  the element size, which is the usual	way to
	   compute the array size but won't work out correctly with  pointers.
	   This	 warning  warns	e.g. about "sizeof (ptr) / sizeof (ptr[0])" if
	   "ptr" is not	an array, but a	pointer.  This warning is  enabled  by
	   -Wall.

       -Wsizeof-pointer-memaccess
	   Warn	 for suspicious	length parameters to certain string and	memory
	   built-in functions if the argument  uses  "sizeof".	 This  warning
	   triggers  for example for "memset (ptr, 0, sizeof (ptr));" if "ptr"
	   is not an array, but	a pointer, and suggests	 a  possible  fix,  or
	   about      "memcpy	   (&foo,      ptr,	 sizeof	    (&foo));".
	   -Wsizeof-pointer-memaccess also warns about calls to	bounded	string
	   copy	functions like "strncat" or  "strncpy"	that  specify  as  the
	   bound  a  "sizeof" expression of the	source array.  For example, in
	   the following function the call to "strncat"	specifies the size  of
	   the source string as	the bound.  That is almost certainly a mistake
	   and so the call is diagnosed.

		   void	make_file (const char *name)
		   {
		     char path[PATH_MAX];
		     strncpy (path, name, sizeof path -	1);
		     strncat (path, ".text", sizeof ".text");
		     ...
		   }

	   The -Wsizeof-pointer-memaccess option is enabled by -Wall.

       -Wno-sizeof-array-argument
	   Do  not  warn  when the "sizeof" operator is	applied	to a parameter
	   that	is declared as	an  array  in  a  function  definition.	  This
	   warning is enabled by default for C and C++ programs.

       -Wmemset-elt-size
	   Warn	for suspicious calls to	the "memset" built-in function,	if the
	   first  argument  references	an  array, and the third argument is a
	   number equal	to the number of elements, but not equal to  the  size
	   of the array	in memory.  This indicates that	the user has omitted a
	   multiplication  by  the  element  size.  This warning is enabled by
	   -Wall.

       -Wmemset-transposed-args
	   Warn	for suspicious calls to	the "memset" built-in  function	 where
	   the	second	argument  is  not zero and the third argument is zero.
	   For example,	the call "memset (buf, sizeof buf,  0)"	 is  diagnosed
	   because  "memset  (buf,  0,	sizeof	buf)"  was meant instead.  The
	   diagnostic is only emitted if the third argument is a literal zero.
	   Otherwise, if it is an expression that is folded to zero, or	a cast
	   of zero to some type, it is far less	likely that the	arguments have
	   been	mistakenly transposed and no warning is	emitted.  This warning
	   is enabled by -Wall.

       -Waddress
	   Warn	about suspicious uses of memory	addresses. These include using
	   the address of a function in	 a  conditional	 expression,  such  as
	   "void  func(void);  if  (func)", and	comparisons against the	memory
	   address of a	string literal,	such as	"if (x == "abc")".  Such  uses
	   typically  indicate	a  programmer error: the address of a function
	   always evaluates to true, so	their use  in  a  conditional  usually
	   indicate  that  the programmer forgot the parentheses in a function
	   call; and comparisons against string	literals result	in unspecified
	   behavior and	are not	portable in C, so they usually	indicate  that
	   the	programmer  intended to	use "strcmp".  This warning is enabled
	   by -Wall.

       -Wno-address-of-packed-member
	   Do not warn when the	address	of packed member of struct or union is
	   taken, which	usually	results	in an unaligned	pointer	 value.	  This
	   is enabled by default.

       -Wlogical-op
	   Warn	 about	suspicious  uses  of logical operators in expressions.
	   This	includes using logical operators in contexts where a  bit-wise
	   operator is likely to be expected.  Also warns when the operands of
	   a logical operator are the same:

		   extern int a;
		   if (a < 0 &&	a < 0) { ... }

       -Wlogical-not-parentheses
	   Warn	 about	logical	 not  used  on the left	hand side operand of a
	   comparison.	This option does not warn  if  the  right  operand  is
	   considered  to  be  a boolean expression.  Its purpose is to	detect
	   suspicious code like	the following:

		   int a;
		   ...
		   if (!a > 1) { ... }

	   It is possible to suppress the warning by  wrapping	the  LHS  into
	   parentheses:

		   if ((!a) > 1) { ... }

	   This	warning	is enabled by -Wall.

       -Waggregate-return
	   Warn	 if any	functions that return structures or unions are defined
	   or called.  (In languages where you can return an array, this  also
	   elicits a warning.)

       -Wno-aggressive-loop-optimizations
	   Warn	 if  in	a loop with constant number of iterations the compiler
	   detects undefined behavior in some statement	during one or more  of
	   the iterations.

       -Wno-attributes
	   Do  not  warn  if  an  unexpected  "__attribute__" is used, such as
	   unrecognized	attributes, function attributes	applied	to  variables,
	   etc.	  This	does  not  stop	 errors	for incorrect use of supported
	   attributes.

       -Wno-builtin-declaration-mismatch
	   Warn	if a  built-in	function  is  declared	with  an  incompatible
	   signature  or  as  a	 non-function,	or  when  a  built-in function
	   declared with a type	that does not include a	 prototype  is	called
	   with	 arguments whose promoted types	do not match those expected by
	   the function.  When -Wextra is specified, also warn when a built-in
	   function that takes arguments is declared without a prototype.  The
	   -Wbuiltin-declaration-mismatch warning is enabled by	 default.   To
	   avoid  the  warning	include	 the  appropriate  header to bring the
	   prototypes of built-in functions into scope.

	   For example,	the call to "memset" below is diagnosed	by the warning
	   because the function	expects	 a  value  of  type  "size_t"  as  its
	   argument   but  the	type  of  32  is  "int".   With	 -Wextra,  the
	   declaration of the function is diagnosed as well.

		   extern void*	memset ();
		   void	f (void	*d)
		   {
		     memset (d,	'\0', 32);
		   }

       -Wno-builtin-macro-redefined
	   Do not  warn	 if  certain  built-in	macros	are  redefined.	  This
	   suppresses	 warnings   for	  redefinition	 of   "__TIMESTAMP__",
	   "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
	   Warn	if a function is declared or defined  without  specifying  the
	   argument  types.   (An  old-style  function definition is permitted
	   without a warning if	preceded by a declaration that	specifies  the
	   argument types.)

       -Wold-style-declaration (C and Objective-C only)
	   Warn	 for  obsolescent  usages,  according  to the C	Standard, in a
	   declaration.	For example, warn  if  storage-class  specifiers  like
	   "static"  are  not the first	things in a declaration.  This warning
	   is also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
	   Warn	if an old-style	function definition is	used.	A  warning  is
	   given even if there is a previous prototype.	 A definition using ()
	   is  not  considered an old-style definition in C2X mode, because it
	   is equivalent to (void) in that case, but  is  considered  an  old-
	   style definition for	older standards.

       -Wmissing-parameter-type	(C and Objective-C only)
	   A  function	parameter  is  declared	 without  a  type specifier in
	   K&R-style functions:

		   void	foo(bar) { }

	   This	warning	is also	enabled	by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
	   Warn	if a global function is	defined	without	a  previous  prototype
	   declaration.	  This warning is issued even if the definition	itself
	   provides a prototype.  Use this option to detect  global  functions
	   that	do not have a matching prototype declaration in	a header file.
	   This	 option	is not valid for C++ because all function declarations
	   provide prototypes  and  a  non-matching  declaration  declares  an
	   overload  rather  than  conflict  with an earlier declaration.  Use
	   -Wmissing-declarations to detect missing declarations in C++.

       -Wmissing-declarations
	   Warn	 if  a	global	function  is  defined	without	  a   previous
	   declaration.	  Do  so  even	if  the	 definition  itself provides a
	   prototype.  Use this	option to detect global	functions that are not
	   declared in header  files.	In  C,	no  warnings  are  issued  for
	   functions	with	previous   non-prototype   declarations;   use
	   -Wmissing-prototypes	to detect  missing  prototypes.	  In  C++,  no
	   warnings   are   issued  for	 function  templates,  or  for	inline
	   functions, or for functions in anonymous namespaces.

       -Wmissing-field-initializers
	   Warn	if a structure's initializer has  some	fields	missing.   For
	   example, the	following code causes such a warning, because "x.h" is
	   implicitly zero:

		   struct s { int f, g,	h; };
		   struct s x =	{ 3, 4 };

	   This	 option	 does  not  warn about designated initializers,	so the
	   following modification does not trigger a warning:

		   struct s { int f, g,	h; };
		   struct s x =	{ .f = 3, .g = 4 };

	   In C	this option does not warn about	the universal zero initializer
	   { 0 }:

		   struct s { int f, g,	h; };
		   struct s x =	{ 0 };

	   Likewise, in	C++ this option	does not warn  about  the  empty  {  }
	   initializer,	for example:

		   struct s { int f, g,	h; };
		   s x = { };

	   This	warning	is included in -Wextra.	 To get	other -Wextra warnings
	   without this	one, use -Wextra -Wno-missing-field-initializers.

       -Wno-multichar
	   Do not warn if a multicharacter constant ('FOOF') is	used.  Usually
	   they	  indicate   a	 typo	in  the	 user's	 code,	as  they  have
	   implementation-defined values, and should not be used  in  portable
	   code.

       -Wnormalized=[none|id|nfc|nfkc]
	   In  ISO  C  and  ISO	C++, two identifiers are different if they are
	   different  sequences	 of  characters.   However,   sometimes	  when
	   characters  outside the basic ASCII character set are used, you can
	   have	two different character	sequences  that	 look  the  same.   To
	   avoid confusion, the	ISO 10646 standard sets	out some normalization
	   rules  which	 when  applied ensure that two sequences that look the
	   same	are turned into	the same sequence.  GCC	can warn  you  if  you
	   are	using  identifiers  that have not been normalized; this	option
	   controls that warning.

	   There are four levels of warning supported by GCC.  The default  is
	   -Wnormalized=nfc,  which  warns about any identifier	that is	not in
	   the ISO 10646 "C" normalized	form, NFC.   NFC  is  the  recommended
	   form	for most uses.	It is equivalent to -Wnormalized.

	   Unfortunately,  there are some characters allowed in	identifiers by
	   ISO C and ISO C++ that, when	turned into NFC, are  not  allowed  in
	   identifiers.	  That	is,  there's  no  way  to use these symbols in
	   portable ISO	C or  C++  and	have  all  your	 identifiers  in  NFC.
	   -Wnormalized=id suppresses the warning for these characters.	 It is
	   hoped  that	future versions	of the standards involved will correct
	   this, which is why this option is not the default.

	   You can switch the  warning	off  for  all  characters  by  writing
	   -Wnormalized=none  or  -Wno-normalized.  You	should only do this if
	   you are using some other normalization scheme (like	"D"),  because
	   otherwise  you can easily create bugs that are literally impossible
	   to see.

	   Some	characters in  ISO  10646  have	 distinct  meanings  but  look
	   identical  in  some fonts or	display	methodologies, especially once
	   formatting has been applied.	 For instance  "\u207F",  "SUPERSCRIPT
	   LATIN  SMALL	 LETTER	 N", displays just like	a regular "n" that has
	   been	 placed	 in  a	superscript.   ISO  10646  defines  the	  NFKC
	   normalization  scheme  to convert all these into a standard form as
	   well, and GCC warns if  your	 code  is  not	in  NFKC  if  you  use
	   -Wnormalized=nfkc.	This  warning  is  comparable to warning about
	   every identifier that contains the letter O	because	 it  might  be
	   confused  with  the	digit 0, and so	is not the default, but	may be
	   useful as a local coding convention if the programming  environment
	   cannot be fixed to display these characters distinctly.

       -Wno-attribute-warning
	   Do  not  warn  about	 usage	of  functions  declared	with "warning"
	   attribute.	  By	default,    this    warning    is     enabled.
	   -Wno-attribute-warning  can	be  used  to  disable  the  warning or
	   -Wno-error=attribute-warning	can be used to disable the error  when
	   compiled with -Werror flag.

       -Wno-deprecated
	   Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
	   Do not warn about uses of functions,	variables, and types marked as
	   deprecated by using the "deprecated"	attribute.

       -Wno-overflow
	   Do not warn about compile-time overflow in constant expressions.

       -Wno-odr
	   Warn	  about	  One  Definition  Rule	 violations  during  link-time
	   optimization.  Enabled by default.

       -Wopenmp-simd
	   Warn	if  the	 vectorizer  cost  model  overrides  the  OpenMP  simd
	   directive  set by user.  The	-fsimd-cost-model=unlimited option can
	   be used to relax the	cost model.

       -Woverride-init (C and Objective-C only)
	   Warn	if an initialized field	without	 side  effects	is  overridden
	   when	using designated initializers.

	   This	warning	is included in -Wextra.	 To get	other -Wextra warnings
	   without this	one, use -Wextra -Wno-override-init.

       -Wno-override-init-side-effects (C and Objective-C only)
	   Do not warn if an initialized field with side effects is overridden
	   when	 using	designated  initializers.   This warning is enabled by
	   default.

       -Wpacked
	   Warn	if a structure is given	the packed attribute, but  the	packed
	   attribute  has  no  effect  on the layout or	size of	the structure.
	   Such	 structures  may  be  mis-aligned  for	little	benefit.   For
	   instance,  in  this	code,  the  variable  "f.x" in "struct bar" is
	   misaligned even though "struct bar" does not	itself have the	packed
	   attribute:

		   struct foo {
		     int x;
		     char a, b,	c, d;
		   } __attribute__((packed));
		   struct bar {
		     char z;
		     struct foo	f;
		   };

       -Wnopacked-bitfield-compat
	   The 4.1, 4.2	and 4.3	series of GCC ignore the "packed" attribute on
	   bit-fields of type "char".  This was	 fixed	in  GCC	 4.4  but  the
	   change  can	lead  to  differences  in  the	structure layout.  GCC
	   informs you when the	offset of such a field has changed in GCC 4.4.
	   For example there is	no longer a 4-bit padding  between  field  "a"
	   and "b" in this structure:

		   struct foo
		   {
		     char a:4;
		     char b:8;
		   } __attribute__ ((packed));

	   This	     warning	  is	  enabled     by     default.	   Use
	   -Wno-packed-bitfield-compat to disable this warning.

       -Wpacked-not-aligned (C,	C++, Objective-C and Objective-C++ only)
	   Warn	if a structure field with explicitly specified alignment in  a
	   packed  struct or union is misaligned.  For example,	a warning will
	   be issued on	"struct	S", like, "warning: alignment 1	of 'struct  S'
	   is less than	8", in this code:

		   struct __attribute__	((aligned (8)))	S8 { char a[8];	};
		   struct __attribute__	((packed)) S {
		     struct S8 s8;
		   };

	   This	warning	is enabled by -Wall.

       -Wpadded
	   Warn	 if  padding  is  included  in a structure, either to align an
	   element  of	the  structure	or  to	align  the  whole   structure.
	   Sometimes  when this	happens	it is possible to rearrange the	fields
	   of the structure to reduce the padding and so  make	the  structure
	   smaller.

       -Wredundant-decls
	   Warn	if anything is declared	more than once in the same scope, even
	   in cases where multiple declaration is valid	and changes nothing.

       -Wrestrict
	   Warn	 when an object	referenced by a	"restrict"-qualified parameter
	   (or,	in C++,	a  "__restrict"-qualified  parameter)  is  aliased  by
	   another argument, or	when copies between such objects overlap.  For
	   example,  the  call	to  the	 "strcpy"  function  below attempts to
	   truncate the	string by replacing its	initial	 characters  with  the
	   last	 four.	 However,  because the call writes the terminating NUL
	   into	"a[4]",	the copies overlap and the call	is diagnosed.

		   void	foo (void)
		   {
		     char a[] =	"abcd1234";
		     strcpy (a,	a + 4);
		     ...
		   }

	   The -Wrestrict option detects some instances	of simple overlap even
	   without optimization	but works  best	 at  -O2  and  above.	It  is
	   included in -Wall.

       -Wnested-externs	(C and Objective-C only)
	   Warn	if an "extern" declaration is encountered within a function.

       -Winline
	   Warn	 if  a	function that is declared as inline cannot be inlined.
	   Even	with this option, the compiler does not	warn about failures to
	   inline functions declared in	system headers.

	   The compiler	uses a variety of heuristics to	determine  whether  or
	   not	to  inline  a  function.  For example, the compiler takes into
	   account the size of the function being inlined and  the  amount  of
	   inlining  that  has	already	 been  done  in	 the current function.
	   Therefore, seemingly	insignificant changes in  the  source  program
	   can cause the warnings produced by -Winline to appear or disappear.

       -Wint-in-bool-context
	   Warn	 for suspicious	use of integer values where boolean values are
	   expected, such as conditional expressions  (?:)  using  non-boolean
	   integer  constants  in boolean context, like	"if (a <= b ? 2	: 3)".
	   Or left shifting of signed integers in boolean context,  like  "for
	   (a  = 0; 1 << a; a++);".  Likewise for all kinds of multiplications
	   regardless of the data type.	 This warning is enabled by -Wall.

       -Wno-int-to-pointer-cast
	   Suppress warnings from casts	to pointer type	of  an	integer	 of  a
	   different  size.  In	C++, casting to	a pointer type of smaller size
	   is an error.	Wint-to-pointer-cast is	enabled	by default.

       -Wno-pointer-to-int-cast	(C and Objective-C only)
	   Suppress warnings from casts	from a pointer to an integer type of a
	   different size.

       -Winvalid-pch
	   Warn	if a precompiled header	is found in the	search path but	cannot
	   be used.

       -Wlong-long
	   Warn	if "long long" type  is	 used.	 This  is  enabled  by	either
	   -Wpedantic or -Wtraditional in ISO C90 and C++98 modes.  To inhibit
	   the warning messages, use -Wno-long-long.

       -Wvariadic-macros
	   Warn	 if  variadic  macros  are used	in ISO C90 mode, or if the GNU
	   alternate syntax is used in ISO  C99	 mode.	 This  is  enabled  by
	   either   -Wpedantic	or  -Wtraditional.   To	 inhibit  the  warning
	   messages, use -Wno-variadic-macros.

       -Wno-varargs
	   Do not warn upon questionable usage of the macros  used  to	handle
	   variable  arguments like "va_start".	 These warnings	are enabled by
	   default.

       -Wvector-operation-performance
	   Warn	if vector operation is not implemented via  SIMD  capabilities
	   of  the  architecture.   Mainly  useful for the performance tuning.
	   Vector operation can	be implemented "piecewise", which  means  that
	   the	scalar	operation  is  performed  on every vector element; "in
	   parallel", which means that the  vector  operation  is  implemented
	   using  scalars  of  wider  type, which normally is more performance
	   efficient; and "as a	single scalar",	which means that  vector  fits
	   into	a scalar type.

       -Wvla
	   Warn	 if  a	variable-length	 array	is used	in the code.  -Wno-vla
	   prevents the	-Wpedantic warning of the variable-length array.

       -Wvla-larger-than=byte-size
	   If this option is used, the	compiler  warns	 for  declarations  of
	   variable-length  arrays  whose size is either unbounded, or bounded
	   by an argument that allows  the  array  size	 to  exceed  byte-size
	   bytes.   This  is  similar  to  how	-Walloca-larger-than=byte-size
	   works, but with variable-length arrays.

	   Note	that GCC may optimize small variable-length arrays of a	 known
	   value  into plain arrays, so	this warning may not get triggered for
	   such	arrays.

	   -Wvla-larger-than=PTRDIFF_MAX  is  enabled  by   default   but   is
	   typically only effective when -ftree-vrp is active (default for -O2
	   and above).

	   See also -Walloca-larger-than=byte-size.

       -Wno-vla-larger-than
	   Disable  -Wvla-larger-than=	warnings.  The option is equivalent to
	   -Wvla-larger-than=SIZE_MAX or larger.

       -Wvla-parameter
	   Warn	about  redeclarations  of  functions  involving	 arguments  of
	   Variable  Length  Array  types  of inconsistent kinds or forms, and
	   enable the detection	of out-of-bounds accesses to  such  parameters
	   by warnings such as -Warray-bounds.

	   If  the  first  function  declaration  uses	the VLA	form the bound
	   specified in	the array is assumed  to  be  the  minimum  number  of
	   elements  expected  to be provided in calls to the function and the
	   maximum number of elements accessed	by  it.	  Failing  to  provide
	   arguments  of  sufficient  size  or accessing more than the maximum
	   number of elements may be diagnosed.

	   For example,	the warning triggers for the following	redeclarations
	   because  the	 first one allows an array of any size to be passed to
	   "f" while the second	one specifies that  the	 array	argument  must
	   have	 at  least  "n"	 elements.   In	addition, calling "f" with the
	   assotiated VLA bound	parameter in excess of the  actual  VLA	 bound
	   triggers a warning as well.

		   void	f (int n, int[n]);
		   void	f (int,	int[]);	    // warning:	argument 2 previously declared as a VLA

		   void	g (int n)
		   {
		       if (n > 4)
			 return;
		       int a[n];
		       f (sizeof a, a);	    // warning:	access to a by f may be	out of bounds
		     ...
		   }

	   -Wvla-parameter is included in -Wall.  The -Warray-parameter	option
	   triggers  warnings  for  similar  problems involving	ordinary array
	   arguments.

       -Wvolatile-register-var
	   Warn	if a register variable is  declared  volatile.	 The  volatile
	   modifier  does  not	inhibit	 all  optimizations that may eliminate
	   reads and/or	writes to register variables.  This warning is enabled
	   by -Wall.

       -Wdisabled-optimization
	   Warn	if a requested optimization pass is  disabled.	 This  warning
	   does	 not generally indicate	that there is anything wrong with your
	   code; it merely indicates  that  GCC's  optimizers  are  unable  to
	   handle  the code effectively.  Often, the problem is	that your code
	   is too big or too complex; GCC refuses to  optimize	programs  when
	   the	optimization  itself  is  likely to take inordinate amounts of
	   time.

       -Wpointer-sign (C and Objective-C only)
	   Warn	for pointer argument  passing  or  assignment  with  different
	   signedness.	 This  option is only supported	for C and Objective-C.
	   It is implied by -Wall and by -Wpedantic,  which  can  be  disabled
	   with	-Wno-pointer-sign.

       -Wstack-protector
	   This	 option	 is  only active when -fstack-protector	is active.  It
	   warns  about	 functions  that  are  not  protected  against	 stack
	   smashing.

       -Woverlength-strings
	   Warn	 about	string	constants  that	 are  longer than the "minimum
	   maximum" length specified in	 the  C	 standard.   Modern  compilers
	   generally  allow  string  constants	that  are much longer than the
	   standard's minimum limit, but very portable programs	 should	 avoid
	   using longer	strings.

	   The limit applies after string constant concatenation, and does not
	   count  the  trailing	NUL.  In C90, the limit	was 509	characters; in
	   C99,	it was raised to 4095.	C++98 does  not	 specify  a  normative
	   minimum maximum, so we do not diagnose overlength strings in	C++.

	   This	 option	 is  implied  by  -Wpedantic, and can be disabled with
	   -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
	   Issue a warning for any floating constant  that  does  not  have  a
	   suffix.   When  used	 together with -Wsystem-headers	it warns about
	   such	constants in system header files.  This	 can  be  useful  when
	   preparing  code to use with the "FLOAT_CONST_DECIMAL64" pragma from
	   the decimal floating-point extension	to C99.

       -Wno-lto-type-mismatch
	   During  the	link-time  optimization,  do  not  warn	  about	  type
	   mismatches in global	declarations from different compilation	units.
	   Requires -flto to be	enabled.  Enabled by default.

       -Wno-designated-init (C and Objective-C only)
	   Suppress   warnings	when  a	 positional  initializer  is  used  to
	   initialize  a   structure   that   has   been   marked   with   the
	   "designated_init" attribute.

   Options That	Control	Static Analysis
       -fanalyzer
	   This	 option	enables	an static analysis of program flow which looks
	   for "interesting"  interprocedural  paths  through  the  code,  and
	   issues warnings for problems	found on them.

	   This	analysis is much more expensive	than other GCC warnings.

	   Enabling this option	effectively enables the	following warnings:

	   -Wanalyzer-double-fclose			-Wanalyzer-double-free
	   -Wanalyzer-exposure-through-output-file	  -Wanalyzer-file-leak
	   -Wanalyzer-free-of-non-heap			-Wanalyzer-malloc-leak
	   -Wanalyzer-mismatching-deallocation
	   -Wanalyzer-possible-null-argument
	   -Wanalyzer-possible-null-dereference	      -Wanalyzer-null-argument
	   -Wanalyzer-null-dereference	       -Wanalyzer-shift-count-negative
	   -Wanalyzer-shift-count-overflow	-Wanalyzer-stale-setjmp-buffer
	   -Wanalyzer-tainted-array-index
	   -Wanalyzer-unsafe-call-within-signal-handler
	   -Wanalyzer-use-after-free
	   -Wanalyzer-use-of-pointer-in-stale-stack-frame
	   -Wanalyzer-write-to-const -Wanalyzer-write-to-string-literal

	   This	 option	 is only available if GCC was configured with analyzer
	   support enabled.

       -Wanalyzer-too-complex
	   If -fanalyzer is enabled, the analyzer uses various	heuristics  to
	   attempt  to	explore	the control flow and data flow in the program,
	   but these can be defeated by	sufficiently complicated code.

	   By default,	the  analysis  silently	 stops	if  the	 code  is  too
	   complicated	for  the  analyzer  to fully explore and it reaches an
	   internal limit.  The	-Wanalyzer-too-complex option  warns  if  this
	   occurs.

       -Wno-analyzer-double-fclose
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-double-fclose to disable it.

	   This	diagnostic warns for paths through the code in which  a	 "FILE
	   *" can have "fclose"	called on it more than once.

       -Wno-analyzer-double-free
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-double-free to	disable	it.

	   This	diagnostic warns for paths through the code in which a pointer
	   can have a deallocator called on it more than once, either  "free",
	   or a	deallocator referenced by attribute "malloc".

       -Wno-analyzer-exposure-through-output-file
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-exposure-through-output-file to disable it.

	   This	diagnostic warns  for  paths  through  the  code  in  which  a
	   security-sensitive  value  is  written  to  an output file (such as
	   writing a password to a log file).

       -Wno-analyzer-file-leak
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-file-leak to disable it.

	   This	 diagnostic  warns  for	 paths	through	 the  code  in which a
	   "<stdio.h>" "FILE *"	stream object is leaked.

       -Wno-analyzer-free-of-non-heap
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-free-of-non-heap to disable it.

	   This	diagnostic warns for paths through the code in which "free" is
	   called  on  a  non-heap  pointer  (e.g.  an	on-stack  buffer, or a
	   global).

       -Wno-analyzer-malloc-leak
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-malloc-leak to	disable	it.

	   This	diagnostic warns for paths through the code in which a pointer
	   allocated  via  an  allocator  is  leaked:  either  "malloc",  or a
	   function marked with	attribute "malloc".

       -Wno-analyzer-mismatching-deallocation
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-mismatching-deallocation to disable it.

	   This	diagnostic warns for paths through the code in which the wrong
	   deallocation	 function is called on a pointer value,	based on which
	   function was	used to	allocate the pointer  value.   The  diagnostic
	   will	 warn  about  mismatches  between  "free", scalar "delete" and
	   vector "delete[]", and those	marked as allocator/deallocator	 pairs
	   using attribute "malloc".

       -Wno-analyzer-possible-null-argument
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-possible-null-argument	to disable it.

	   This	diagnostic warns  for  paths  through  the  code  in  which  a
	   possibly-NULL  value	 is  passed to a function argument marked with
	   "__attribute__((nonnull))" as requiring a non-NULL value.

       -Wno-analyzer-possible-null-dereference
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-possible-null-dereference to disable it.

	   This	 diagnostic  warns  for	 paths	through	 the  code  in which a
	   possibly-NULL value is dereferenced.

       -Wno-analyzer-null-argument
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-null-argument to disable it.

	   This	 diagnostic  warns for paths through the code in which a value
	   known to be NULL is passed  to  a  function	argument  marked  with
	   "__attribute__((nonnull))" as requiring a non-NULL value.

       -Wno-analyzer-null-dereference
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-null-dereference to disable it.

	   This	diagnostic warns for paths through the code in which  a	 value
	   known to be NULL is dereferenced.

       -Wno-analyzer-shift-count-negative
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-shift-count-negative to disable it.

	   This	diagnostic warns for paths through the code in which  a	 shift
	   is  attempted  with	a  negative  count.   It  is  analogous	to the
	   -Wshift-count-negative diagnostic implemented in  the  C/C++	 front
	   ends,  but is implemented based on analyzing	interprocedural	paths,
	   rather than merely parsing the syntax tree.	However, the  analyzer
	   does	not prioritize detection of such paths,	so false negatives are
	   more	likely relative	to other warnings.

       -Wno-analyzer-shift-count-overflow
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-shift-count-overflow to disable it.

	   This	diagnostic warns for paths through the code in which  a	 shift
	   is attempted	with a count greater than or equal to the precision of
	   the	operand's type.	 It is analogous to the	-Wshift-count-overflow
	   diagnostic implemented in the C/C++ front ends, but is  implemented
	   based  on  analyzing	 interprocedural  paths,  rather  than	merely
	   parsing the syntax tree.  However, the analyzer does	not prioritize
	   detection of	 such  paths,  so  false  negatives  are  more	likely
	   relative to other warnings.

       -Wno-analyzer-stale-setjmp-buffer
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-stale-setjmp-buffer to	disable	it.

	   This	diagnostic warns for paths through the code in which "longjmp"
	   is called to	rewind to a "jmp_buf" relating to a "setjmp" call in a
	   function that has returned.

	   When	"setjmp" is called on a	"jmp_buf" to record a rewind location,
	   it records the stack	frame.	The stack frame	becomes	 invalid  when
	   the	function  containing the "setjmp" call returns.	 Attempting to
	   rewind to it	via "longjmp" would reference a	stack  frame  that  no
	   longer exists, and likely lead to a crash (or worse).

       -Wno-analyzer-tainted-array-index
	   This	 warning requires both -fanalyzer and -fanalyzer-checker=taint
	   to enable it; use -Wno-analyzer-tainted-array-index to disable it.

	   This	diagnostic warns for paths through the code in which  a	 value
	   that	 could	be under an attacker's control is used as the index of
	   an array access without being sanitized.

       -Wno-analyzer-unsafe-call-within-signal-handler
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-unsafe-call-within-signal-handler to disable it.

	   This	 diagnostic  warns  for	 paths	through	 the  code  in which a
	   function known to be	async-signal-unsafe  (such  as	"fprintf")  is
	   called from a signal	handler.

       -Wno-analyzer-use-after-free
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-use-after-free	to disable it.

	   This	diagnostic warns for paths through the code in which a pointer
	   is used after a deallocator is called on it:	either	"free",	 or  a
	   deallocator referenced by attribute "malloc".

       -Wno-analyzer-use-of-pointer-in-stale-stack-frame
	   This	  warning   requires   -fanalyzer,   which   enables  it;  use
	   -Wno-analyzer-use-of-pointer-in-stale-stack-frame to	disable	it.

	   This	diagnostic warns for paths through the code in which a pointer
	   is dereferenced that	points to a variable in	a stale	stack frame.

       -Wno-analyzer-write-to-const
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-write-to-const	to disable it.

	   This	 diagnostic  warns  for	 paths	through	 the code in which the
	   analyzer detects an attempt to write	through	a pointer to a "const"
	   object.  However, the analyzer does	not  prioritize	 detection  of
	   such	 paths,	 so  false negatives are more likely relative to other
	   warnings.

       -Wno-analyzer-write-to-string-literal
	   This	 warning  requires   -fanalyzer,   which   enables   it;   use
	   -Wno-analyzer-write-to-string-literal to disable it.

	   This	 diagnostic  warns  for	 paths	through	 the code in which the
	   analyzer detects an attempt to write	through	a pointer to a	string
	   literal.   However,	the  analyzer does not prioritize detection of
	   such	paths, so false	negatives are more likely  relative  to	 other
	   warnings.

       Pertinent  parameters  for  controlling	the  exploration  are: --param
       analyzer-bb-explosion-factor=value,			       --param
       analyzer-max-enodes-per-program-point=value,		       --param
       analyzer-max-recursion-depth=value,	       and	       --param
       analyzer-min-snodes-for-call-summary=value.

       The following options control the analyzer.

       -fanalyzer-call-summaries
	   Simplify  interprocedural  analysis	by  computing  the  effect  of
	   certain calls, rather than exploring	all paths through the function
	   from	callsite to each possible return.

	   If enabled, call summaries are only used for	 functions  with  more
	   than	 one  call site, and that are sufficiently complicated (as per
	   --param analyzer-min-snodes-for-call-summary=value).

       -fanalyzer-checker=name
	   Restrict the	analyzer to run	just the named checker,	and enable it.

	   Some	checkers are disabled by default (even with -fanalyzer),  such
	   as	    the	      "taint"	    checker	  that	    implements
	   -Wanalyzer-tainted-array-index, and	this  option  is  required  to
	   enable them.

       -fno-analyzer-feasibility
	   This	option is intended for analyzer	developers.

	   By  default	the analyzer verifies that there is a feasible control
	   flow	path for each diagnostic it emits: that	 the  conditions  that
	   hold	are not	mutually exclusive.  Diagnostics for which no feasible
	   path	 can  be found are rejected.  This filtering can be suppressed
	   with	-fno-analyzer-feasibility, for debugging issues	in this	code.

       -fanalyzer-fine-grained
	   This	option is intended for analyzer	developers.

	   Internally the analyzer builds an "exploded	graph"	that  combines
	   control flow	graphs with data flow information.

	   By  default,	an edge	in this	graph can contain the effects of a run
	   of	multiple   statements	within	 a    basic    block.	  With
	   -fanalyzer-fine-grained, each statement gets	its own	edge.

       -fanalyzer-show-duplicate-count
	   This	 option	 is  intended  for  analyzer  developers:  if multiple
	   diagnostics have been detected as being duplicates of  each	other,
	   it  emits  a	 note  when  reporting the best	diagnostic, giving the
	   number of  additional  diagnostics  that  were  suppressed  by  the
	   deduplication logic.

       -fno-analyzer-state-merge
	   This	option is intended for analyzer	developers.

	   By  default	the  analyzer attempts to simplify analysis by merging
	   sufficiently	similar	states at each program point as	it builds  its
	   "exploded  graph".  With -fno-analyzer-state-merge this merging can
	   be suppressed, for debugging	state-handling issues.

       -fno-analyzer-state-purge
	   This	option is intended for analyzer	developers.

	   By default the analyzer attempts to simplify	 analysis  by  purging
	   aspects  of	state  at  a program point that	appear to no longer be
	   relevant e.g. the values of locals that aren't  accessed  later  in
	   the function	and which aren't relevant to leak analysis.

	   With	  -fno-analyzer-state-purge  this  purging  of	state  can  be
	   suppressed, for debugging state-handling issues.

       -fanalyzer-transitivity
	   This	 option	 enables  transitivity	of  constraints	  within   the
	   analyzer.

       -fanalyzer-verbose-edges
	   This	 option	 is intended for analyzer developers.  It enables more
	   verbose, lower-level	detail in the  descriptions  of	 control  flow
	   within diagnostic paths.

       -fanalyzer-verbose-state-changes
	   This	 option	 is intended for analyzer developers.  It enables more
	   verbose, lower-level	detail in the descriptions of events  relating
	   to state machines within diagnostic paths.

       -fanalyzer-verbosity=level
	   This	 option	controls the complexity	of the control flow paths that
	   are emitted for analyzer diagnostics.

	   The level can be one	of:

	   0   At this level,  interprocedural	call  and  return  events  are
	       displayed,  along  with	the most pertinent state-change	events
	       relating	to a diagnostic.  For  example,	 for  a	 double-"free"
	       diagnostic, both	calls to "free"	will be	shown.

	   1   As  per	the previous level, but	also show events for the entry
	       to each function.

	   2   As per the previous level, but also  show  events  relating  to
	       control flow that are significant to triggering the issue (e.g.
	       "true path taken" at a conditional).

	       This level is the default.

	   3   As  per	the  previous level, but show all control flow events,
	       not just	significant ones.

	   4   This level is intended for analyzer developers; it adds various
	       other events intended for debugging the analyzer.

       -fdump-analyzer
	   Dump	 internal  details  about  what	 the  analyzer	is  doing   to
	   file.analyzer.txt.	   This	    option     is     overridden    by
	   -fdump-analyzer-stderr.

       -fdump-analyzer-stderr
	   Dump	internal details about what the	analyzer is doing  to  stderr.
	   This	option overrides -fdump-analyzer.

       -fdump-analyzer-callgraph
	   Dump	 a  representation of the call graph suitable for viewing with
	   GraphViz to file.callgraph.dot.

       -fdump-analyzer-exploded-graph
	   Dump	a representation of the	"exploded graph" suitable for  viewing
	   with	 GraphViz  to  file.eg.dot.   Nodes  are  color-coded based on
	   state-machine states	to emphasize state changes.

       -fdump-analyzer-exploded-nodes
	   Emit	diagnostics showing where nodes	in the "exploded graph"	are in
	   relation to the program source.

       -fdump-analyzer-exploded-nodes-2
	   Dump	 a  textual  representation  of	 the   "exploded   graph"   to
	   file.eg.txt.

       -fdump-analyzer-exploded-nodes-3
	   Dump	 a  textual representation of the "exploded graph" to one dump
	   file	per node, to file.eg-id.txt.  This is typically	a large	number
	   of dump files.

       -fdump-analyzer-feasibility
	   Dump	internal details about	the  analyzer's	 search	 for  feasible
	   paths.  The details are written in a	form suitable for viewing with
	   GraphViz to filenames of the	form file.*.fg.dot and file.*.tg.dot.

       -fdump-analyzer-json
	   Dump	 a  compressed	JSON  representation  of analyzer internals to
	   file.analyzer.json.gz.  The precise format is subject to change.

       -fdump-analyzer-state-purge
	   As per -fdump-analyzer-supergraph, dump  a  representation  of  the
	   "supergraph"	 suitable  for viewing with GraphViz, but annotate the
	   graph with information on what state	will be	purged at  each	 node.
	   The graph is	written	to file.state-purge.dot.

       -fdump-analyzer-supergraph
	   Dump	 representations of the	"supergraph" suitable for viewing with
	   GraphViz  to	 file.supergraph.dot  and  to  file.supergraph-eg.dot.
	   These  show	all  of	 the  control flow graphs in the program, with
	   interprocedural edges for  calls  and  returns.   The  second  dump
	   contains  annotations  showing  nodes  in  the "exploded graph" and
	   diagnostics associated with them.

   Options for Debugging Your Program
       To tell GCC to emit extra information for use by	a debugger, in	almost
       all cases you need only to add -g to your other options.

       GCC  allows  you	 to  use -g with -O.  The shortcuts taken by optimized
       code may	occasionally be	surprising: some variables  you	 declared  may
       not  exist  at  all; flow of control may	briefly	move where you did not
       expect it; some statements may not be  executed	because	 they  compute
       constant	 results  or their values are already at hand; some statements
       may execute in different	places because they have  been	moved  out  of
       loops.	Nevertheless  it  is possible to debug optimized output.  This
       makes it	reasonable to use the optimizer	for programs that  might  have
       bugs.

       If you are not using some other optimization option, consider using -Og
       with  -g.   With	no -O option at	all, some compiler passes that collect
       information useful for debugging	do not run at all,  so	that  -Og  may
       result in a better debugging experience.

       -g  Produce  debugging  information  in	the  operating system's	native
	   format (stabs, COFF,	XCOFF, or DWARF).   GDB	 can  work  with  this
	   debugging information.

	   On  most  systems  that  use	 stabs format, -g enables use of extra
	   debugging information that only GDB can use;	this extra information
	   makes debugging  work  better  in  GDB  but	probably  makes	 other
	   debuggers  crash  or	 refuse	 to  read the program.	If you want to
	   control for certain whether to generate the extra information,  use
	   -gstabs+, -gstabs, -gxcoff+,	-gxcoff, or -gvms (see below).

       -ggdb
	   Produce  debugging  information  for	use by GDB.  This means	to use
	   the most expressive format available	(DWARF,	stabs, or  the	native
	   format if neither of	those are supported), including	GDB extensions
	   if at all possible.

       -gdwarf
       -gdwarf-version
	   Produce   debugging	 information  in  DWARF	 format	 (if  that  is
	   supported).	The value of version may be either 2, 3, 4 or  5;  the
	   default  version  for  most	targets	 is  5	(with the exception of
	   VxWorks, TPF	and Darwin/Mac OS X, which default to version  2,  and
	   AIX,	which defaults to version 4).

	   Note	 that  with DWARF Version 2, some ports	require	and always use
	   some	non-conflicting	DWARF 3	extensions in the unwind tables.

	   Version 4 may require GDB 7.0  and  -fvar-tracking-assignments  for
	   maximum benefit. Version 5 requires GDB 8.0 or higher.

	   GCC	no  longer  supports  DWARF  Version 1,	which is substantially
	   different than Version 2 and	later.	For historical	reasons,  some
	   other  DWARF-related	 options such as -fno-dwarf2-cfi-asm) retain a
	   reference to	DWARF Version 2	in  their  names,  but	apply  to  all
	   currently-supported versions	of DWARF.

       -gstabs
	   Produce   debugging	 information  in  stabs	 format	 (if  that  is
	   supported), without GDB extensions.	This is	the format used	by DBX
	   on most BSD systems.	 On MIPS, Alpha	and System V Release 4 systems
	   this	option produces	stabs debugging	output that is not  understood
	   by DBX.  On System V	Release	4 systems this option requires the GNU
	   assembler.

       -gstabs+
	   Produce   debugging	 information  in  stabs	 format	 (if  that  is
	   supported),	using  GNU  extensions	understood  only  by  the  GNU
	   debugger  (GDB).   The  use	of  these extensions is	likely to make
	   other debuggers crash or refuse to read the program.

       -gxcoff
	   Produce  debugging  information  in	XCOFF  format  (if   that   is
	   supported).	 This  is  the	format used by the DBX debugger	on IBM
	   RS/6000 systems.

       -gxcoff+
	   Produce  debugging  information  in	XCOFF  format  (if   that   is
	   supported),	using  GNU  extensions	understood  only  by  the  GNU
	   debugger (GDB).  The	use of these  extensions  is  likely  to  make
	   other  debuggers crash or refuse to read the	program, and may cause
	   assemblers other than the GNU  assembler  (GAS)  to	fail  with  an
	   error.

       -gvms
	   Produce debugging information in Alpha/VMS debug format (if that is
	   supported).	This is	the format used	by DEBUG on Alpha/VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gxcofflevel
       -gvmslevel
	   Request  debugging  information  and	 also use level	to specify how
	   much	information.  The default level	is 2.

	   Level 0 produces no debug information at all.   Thus,  -g0  negates
	   -g.

	   Level  1 produces minimal information, enough for making backtraces
	   in parts of the  program  that  you	don't  plan  to	 debug.	  This
	   includes descriptions of functions and external variables, and line
	   number tables, but no information about local variables.

	   Level   3  includes	extra  information,  such  as  all  the	 macro
	   definitions present in the program.	Some debuggers	support	 macro
	   expansion when you use -g3.

	   If  you use multiple	-g options, with or without level numbers, the
	   last	such option is the one that is effective.

	   -gdwarf does	not  accept  a	concatenated  debug  level,  to	 avoid
	   confusion  with  -gdwarf-level.   Instead use an additional -glevel
	   option to change the	debug level for	DWARF.

       -fno-eliminate-unused-debug-symbols
	   By default, no debug	information is produced	for symbols  that  are
	   not	actually  used.	 Use this option if you	want debug information
	   for all symbols.

       -femit-class-debug-always
	   Instead of emitting debugging information for a C++ class  in  only
	   one object file, emit it in all object files	using the class.  This
	   option should be used only with debuggers that are unable to	handle
	   the	way  GCC  normally  emits  debugging  information  for classes
	   because  using  this	 option	 increases  the	 size	of   debugging
	   information by as much as a factor of two.

       -fno-merge-debug-strings
	   Direct  the	linker	to not merge together strings in the debugging
	   information that are	identical in different object files.   Merging
	   is  not  supported by all assemblers	or linkers.  Merging decreases
	   the size of the debug information in	the output file	at the cost of
	   increasing link processing time.  Merging is	enabled	by default.

       -fdebug-prefix-map=old=new
	   When	compiling files	residing in directory  old,  record  debugging
	   information	describing  them  as if	the files resided in directory
	   new instead.	 This can be used to replace a build-time path with an
	   install-time	path in	the debug info.	 It can	also be	used to	change
	   an absolute path to a relative path by using	. for new.   This  can
	   give	 more reproducible builds, which are location independent, but
	   may require an extra	command	to tell	GDB where to find  the	source
	   files. See also -ffile-prefix-map.

       -fvar-tracking
	   Run variable	tracking pass.	It computes where variables are	stored
	   at  each  position  in  code.  Better debugging information is then
	   generated  (if  the	debugging  information	format	supports  this
	   information).

	   It is enabled by default when compiling with	optimization (-Os, -O,
	   -O2,	 ...),	debugging  information	(-g) and the debug info	format
	   supports it.

       -fvar-tracking-assignments
	   Annotate assignments	to user	variables early	in the compilation and
	   attempt to carry the	annotations over  throughout  the  compilation
	   all	the way	to the end, in an attempt to improve debug information
	   while optimizing.  Use of -gdwarf-4 is recommended along with it.

	   It can be enabled even if var-tracking is disabled, in  which  case
	   annotations	are  created and maintained, but discarded at the end.
	   By default, this flag  is  enabled  together	 with  -fvar-tracking,
	   except when selective scheduling is enabled.

       -gsplit-dwarf
	   If  DWARF  debugging	 information  is  enabled,  separate  as  much
	   debugging information as possible into a separate output file  with
	   the	extension  .dwo.  This option allows the build system to avoid
	   linking files with debug information.  To be	 useful,  this	option
	   requires a debugger capable of reading .dwo files.

       -gdwarf32
       -gdwarf64
	   If  DWARF  debugging	 information is	enabled, the -gdwarf32 selects
	   the 32-bit DWARF format and the -gdwarf64 selects the 64-bit	 DWARF
	   format.   The  default  is  target  specific, on most targets it is
	   -gdwarf32 though.  The 32-bit DWARF format is  smaller,  but	 can't
	   support  more  than	2GiB  of debug information in any of the DWARF
	   debug information sections.	The 64-bit DWARF format	allows	larger
	   debug  information and might	not be well supported by all consumers
	   yet.

       -gdescribe-dies
	   Add description attributes to some DWARF DIEs  that	have  no  name
	   attribute,  such  as	 artificial variables, external	references and
	   call	site parameter DIEs.

       -gpubnames
	   Generate DWARF ".debug_pubnames" and	".debug_pubtypes" sections.

       -ggnu-pubnames
	   Generate ".debug_pubnames"  and  ".debug_pubtypes"  sections	 in  a
	   format  suitable  for  conversion into a GDB	index.	This option is
	   only	useful with a linker that can produce GDB index	version	7.

       -fdebug-types-section
	   When	using DWARF Version 4 or higher, type DIEs  can	 be  put  into
	   their own ".debug_types" section instead of making them part	of the
	   ".debug_info"  section.   It	 is  more  efficient  to put them in a
	   separate  comdat  section  since  the  linker   can	 then	remove
	   duplicates.	 But  not  all	DWARF consumers	support	".debug_types"
	   sections yet	and on some  objects  ".debug_types"  produces	larger
	   instead of smaller debugging	information.

       -grecord-gcc-switches
       -gno-record-gcc-switches
	   This	 switch	 causes	 the  command-line  options used to invoke the
	   compiler that may affect code generation  to	 be  appended  to  the
	   DW_AT_producer  attribute  in  DWARF	 debugging  information.   The
	   options are concatenated with  spaces  separating  them  from  each
	   other  and  from  the  compiler version.  It	is enabled by default.
	   See also -frecord-gcc-switches for another way of storing  compiler
	   options into	the object file.

       -gstrict-dwarf
	   Disallow  using  extensions	of  later  DWARF standard version than
	   selected  with  -gdwarf-version.   On  most	targets	  using	  non-
	   conflicting	DWARF  extensions  from	 later	standard  versions  is
	   allowed.

       -gno-strict-dwarf
	   Allow  using	 extensions  of	 later	DWARF  standard	 version  than
	   selected with -gdwarf-version.

       -gas-loc-support
	   Inform  the compiler	that the assembler supports ".loc" directives.
	   It may then use them	for the	assembler  to  generate	 DWARF2+  line
	   number tables.

	   This	 is  generally	desirable,  because  assembler-generated line-
	   number tables are a lot more	compact	than those  the	 compiler  can
	   generate itself.

	   This	 option	 will be enabled by default if,	at GCC configure time,
	   the assembler was found to support such directives.

       -gno-as-loc-support
	   Force GCC to	generate DWARF2+ line  number  tables  internally,  if
	   DWARF2+ line	number tables are to be	generated.

       -gas-locview-support
	   Inform  the	compiler that the assembler supports "view" assignment
	   and reset assertion checking	in ".loc" directives.

	   This	option will be enabled by default if, at GCC  configure	 time,
	   the assembler was found to support them.

       -gno-as-locview-support
	   Force    GCC	   to	 assign	   view	   numbers    internally,   if
	   -gvariable-location-views are explicitly requested.

       -gcolumn-info
       -gno-column-info
	   Emit	location column	information into DWARF debugging  information,
	   rather than just file and line.  This option	is enabled by default.

       -gstatement-frontiers
       -gno-statement-frontiers
	   This	  option   causes  GCC	to  create  markers  in	 the  internal
	   representation at the beginning of statements,  and	to  keep  them
	   roughly  in	place  throughout compilation, using them to guide the
	   output of "is_stmt" markers in the  line  number  table.   This  is
	   enabled  by default when compiling with optimization	(-Os, -O, -O2,
	   ...), and outputting	DWARF 2	debug information at the normal	level.

       -gvariable-location-views
       -gvariable-location-views=incompat5
       -gno-variable-location-views
	   Augment variable  location  lists  with  progressive	 view  numbers
	   implied from	the line number	table.	This enables debug information
	   consumers  to  inspect state	at certain points of the program, even
	   if  no  instructions	 associated  with  the	corresponding	source
	   locations  are  present  at	that  point.   If  the assembler lacks
	   support for view numbers in line number tables, this	will cause the
	   compiler to emit the	line number table, which generally makes  them
	   somewhat  less  compact.   The  augmented  line  number  tables and
	   location lists  are	fully  backward-compatible,  so	 they  can  be
	   consumed by debug information consumers that	are not	aware of these
	   augmentations, but they won't derive	any benefit from them either.

	   This	  is   enabled	by  default  when  outputting  DWARF  2	 debug
	   information at the normal level, as	long  as  there	 is  assembler
	   support,  -fvar-tracking-assignments	 is enabled and	-gstrict-dwarf
	   is not.  When assembler support is not available, this may still be
	   enabled, but	it will	force  GCC  to	output	internal  line	number
	   tables, and if -ginternal-reset-location-views is not enabled, that
	   will	most certainly lead to silently	mismatching location views.

	   There  is  a	 proposed  representation for view numbers that	is not
	   backward compatible with the	location  list	format	introduced  in
	   DWARF       5,	that	   can	     be	     enabled	  with
	   -gvariable-location-views=incompat5.	 This option may be removed in
	   the future, is only provided	as a reference implementation  of  the
	   proposed  representation.   Debug  information  consumers  are  not
	   expected to	support	 this  extended	 format,  and  they  would  be
	   rendered unable to decode location lists using it.

       -ginternal-reset-location-views
       -gno-internal-reset-location-views
	   Attempt  to	determine  location  views  that  can  be omitted from
	   location view lists.	 This  requires	 the  compiler	to  have  very
	   accurate insn length	estimates, which isn't always the case,	and it
	   may	cause incorrect	view lists to be generated silently when using
	   an assembler	that does not support location view  lists.   The  GNU
	   assembler  will  flag  any  such error as a "view number mismatch".
	   This	is only	enabled	on ports that  define  a  reliable  estimation
	   function.

       -ginline-points
       -gno-inline-points
	   Generate   extended	 debug	 information  for  inlined  functions.
	   Location view  tracking  markers  are  inserted  at	inlined	 entry
	   points, so that address and view numbers can	be computed and	output
	   in  debug  information.   This  can	be  enabled  independently  of
	   location views, in which case the view numbers won't	be output, but
	   it can only be enabled along	with statement frontiers,  and	it  is
	   only	enabled	by default if location views are enabled.

       -gz[=type]
	   Produce  compressed	debug  sections	 in  DWARF  format, if that is
	   supported.  If type is not given, the default type depends  on  the
	   capabilities	 of the	assembler and linker used.  type may be	one of
	   none	(don't compress	debug sections), zlib (use zlib	compression in
	   ELF gABI format), or	zlib-gnu (use zlib compression in  traditional
	   GNU	format).   If  the  linker  doesn't support writing compressed
	   debug  sections,  the  option  is  rejected.	  Otherwise,  if   the
	   assembler  does  not	 support  them,	 -gz  is silently ignored when
	   producing object files.

       -femit-struct-debug-baseonly
	   Emit	debug information for struct-like types	 only  when  the  base
	   name	 of  the compilation source file matches the base name of file
	   in which the	struct is defined.

	   This	 option	 substantially	 reduces   the	 size	of   debugging
	   information,	 but at	significant potential loss in type information
	   to  the  debugger.	See  -femit-struct-debug-reduced  for  a  less
	   aggressive	option.	  See  -femit-struct-debug-detailed  for  more
	   detailed control.

	   This	option works only with DWARF debug output.

       -femit-struct-debug-reduced
	   Emit	debug information for struct-like types	 only  when  the  base
	   name	 of  the compilation source file matches the base name of file
	   in which the	type is	defined, unless	the struct is  a  template  or
	   defined in a	system header.

	   This	  option   significantly   reduces   the   size	 of  debugging
	   information,	with some potential loss in type  information  to  the
	   debugger.   See  -femit-struct-debug-baseonly for a more aggressive
	   option.   See  -femit-struct-debug-detailed	 for   more   detailed
	   control.

	   This	option works only with DWARF debug output.

       -femit-struct-debug-detailed[=spec-list]
	   Specify  the	 struct-like  types  for  which	the compiler generates
	   debug information.  The intent is to	reduce duplicate struct	 debug
	   information between different object	files within the same program.

	   This	 option	 is  a detailed	version	of -femit-struct-debug-reduced
	   and -femit-struct-debug-baseonly, which serves for most needs.

	   A		   specification		has		   the
	   syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

	   The	optional  first	 word limits the specification to structs that
	   are used directly (dir:) or used indirectly (ind:).	A struct  type
	   is  used  directly  when  it	 is  the  type	of a variable, member.
	   Indirect uses arise through pointers	to structs.  That is, when use
	   of an incomplete struct is valid, the use is	indirect.  An  example
	   is struct one direct; struct	two * indirect;.

	   The	optional  second  word	limits	the  specification to ordinary
	   structs (ord:) or generic structs (gen:).  Generic  structs	are  a
	   bit	complicated  to	 explain.   For	 C++,  these  are non-explicit
	   specializations of template classes,	or non-template	classes	within
	   the	above.	 Other	programming  languages	have   generics,   but
	   -femit-struct-debug-detailed	does not yet implement them.

	   The	third  word  specifies	the source files for those structs for
	   which the compiler should emit debug	information.  The values  none
	   and	any  have  the	normal meaning.	 The value base	means that the
	   base	of name	of the file in which the type declaration appears must
	   match the base of the  name	of  the	 main  compilation  file.   In
	   practice,  this  means that when compiling foo.c, debug information
	   is generated	for types declared in that file	 and  foo.h,  but  not
	   other  header  files.   The	value sys means	those types satisfying
	   base	or declared in system or compiler headers.

	   You may need	to experiment to determine the best settings for  your
	   application.

	   The default is -femit-struct-debug-detailed=all.

	   This	option works only with DWARF debug output.

       -fno-dwarf2-cfi-asm
	   Emit	 DWARF	unwind	info as	compiler generated ".eh_frame" section
	   instead of using GAS	".cfi_*" directives.

       -fno-eliminate-unused-debug-types
	   Normally, when producing DWARF output, GCC avoids  producing	 debug
	   symbol  output  for	types that are nowhere used in the source file
	   being compiled.  Sometimes it is useful to have GCC emit  debugging
	   information	 for   all  types  declared  in	 a  compilation	 unit,
	   regardless of whether  or  not  they	 are  actually	used  in  that
	   compilation unit, for example if, in	the debugger, you want to cast
	   a value to a	type that is not actually used in your program (but is
	   declared).	More  often,  however,	this  results in a significant
	   amount of wasted space.

   Options That	Control	Optimization
       These options control various sorts of optimizations.

       Without any optimization	option,	the compiler's goal is to  reduce  the
       cost of compilation and to make debugging produce the expected results.
       Statements  are	independent: if	you stop the program with a breakpoint
       between statements, you can then	assign a new value to any variable  or
       change  the  program counter to any other statement in the function and
       get exactly the results you expect from the source code.

       Turning on optimization flags makes the compiler	attempt	to improve the
       performance and/or code size at the expense  of	compilation  time  and
       possibly	the ability to debug the program.

       The compiler performs optimization based	on the knowledge it has	of the
       program.	 Compiling multiple files at once to a single output file mode
       allows  the  compiler  to  use information gained from all of the files
       when compiling each of them.

       Not  all	 optimizations	are  controlled	 directly  by  a  flag.	  Only
       optimizations that have a flag are listed in this section.

       Most  optimizations are completely disabled at -O0 or if	an -O level is
       not set on the command line, even if individual optimization flags  are
       specified.  Similarly, -Og suppresses many optimization passes.

       Depending  on  the  target  and	how  GCC  was  configured,  a slightly
       different set of	optimizations may be enabled at	 each  -O  level  than
       those  listed  here.   You  can invoke GCC with -Q --help=optimizers to
       find out	the exact set of optimizations that are	enabled	at each	level.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time,	and  a
	   lot more memory for a large function.

	   With	-O, the	compiler tries to reduce code size and execution time,
	   without  performing	any  optimizations  that  take a great deal of
	   compilation time.

	   -O turns on the following optimization flags:

	   -fauto-inc-dec    -fbranch-count-reg	   -fcombine-stack-adjustments
	   -fcompare-elim -fcprop-registers -fdce -fdefer-pop -fdelayed-branch
	   -fdse	 -fforward-propagate	    -fguess-branch-probability
	   -fif-conversion   -fif-conversion2	-finline-functions-called-once
	   -fipa-modref	   -fipa-profile    -fipa-pure-const   -fipa-reference
	   -fipa-reference-addressable			     -fmerge-constants
	   -fmove-loop-invariants     -fomit-frame-pointer    -freorder-blocks
	   -fshrink-wrap       -fshrink-wrap-separate	    -fsplit-wide-types
	   -fssa-backprop  -fssa-phiopt	 -ftree-bit-ccp	 -ftree-ccp  -ftree-ch
	   -ftree-coalesce-vars		 -ftree-copy-prop	    -ftree-dce
	   -ftree-dominator-opts    -ftree-dse	  -ftree-forwprop   -ftree-fre
	   -ftree-phiprop -ftree-pta -ftree-scev-cprop -ftree-sink -ftree-slsr
	   -ftree-sra -ftree-ter -funit-at-a-time

       -O2 Optimize  even   more.    GCC   performs   nearly   all   supported
	   optimizations  that	do  not	 involve  a  space-speed tradeoff.  As
	   compared to -O, this	option increases both compilation time and the
	   performance of the generated	code.

	   -O2 turns on	all optimization flags specified by -O.	 It also turns
	   on the following optimization flags:

	   -falign-functions   -falign-jumps   -falign-labels	 -falign-loops
	   -fcaller-saves  -fcode-hoisting  -fcrossjumping  -fcse-follow-jumps
	   -fcse-skip-blocks	-fdelete-null-pointer-checks	-fdevirtualize
	   -fdevirtualize-speculatively		     -fexpensive-optimizations
	   -ffinite-loops     -fgcse	  -fgcse-lm	-fhoist-adjacent-loads
	   -finline-functions	-finline-small-functions   -findirect-inlining
	   -fipa-bit-cp	 -fipa-cp  -fipa-icf  -fipa-ra	 -fipa-sra   -fipa-vrp
	   -fisolate-erroneous-paths-dereference		   -flra-remat
	   -foptimize-sibling-calls    -foptimize-strlen    -fpartial-inlining
	   -fpeephole2				-freorder-blocks-algorithm=stc
	   -freorder-blocks-and-partition		   -freorder-functions
	   -frerun-cse-after-loop      -fschedule-insns	     -fschedule-insns2
	   -fsched-interblock  -fsched-spec -fstore-merging  -fstrict-aliasing
	   -fthread-jumps	   -ftree-builtin-call-dce	    -ftree-pre
	   -ftree-switch-conversion  -ftree-tail-merge -ftree-vrp

	   Please note the warning under -fgcse	about invoking -O2 on programs
	   that	use computed gotos.

       -O3 Optimize yet	more.  -O3 turns on all	optimizations specified	by -O2
	   and also turns on the following optimization	flags:

	   -fgcse-after-reload	      -fipa-cp-clone	    -floop-interchange
	   -floop-unroll-and-jam      -fpeel-loops	-fpredictive-commoning
	   -fsplit-loops	-fsplit-paths	      -ftree-loop-distribution
	   -ftree-loop-vectorize    -ftree-partial-pre	  -ftree-slp-vectorize
	   -funswitch-loops    -fvect-cost-model     -fvect-cost-model=dynamic
	   -fversion-loops-for-strides

       -O0 Reduce  compilation	time  and  make	debugging produce the expected
	   results.  This is the default.

       -Os Optimize for	size.  -Os enables all -O2 optimizations except	 those
	   that	often increase code size:

	   -falign-functions	-falign-jumps	-falign-labels	 -falign-loops
	   -fprefetch-loop-arrays  -freorder-blocks-algorithm=stc

	   It also enables -finline-functions, causes the compiler to tune for
	   code	 size  rather  than  execution	speed,	and  performs  further
	   optimizations designed to reduce code size.

       -Ofast
	   Disregard  strict  standards	 compliance.   -Ofast  enables all -O3
	   optimizations.  It also enables optimizations that  are  not	 valid
	   for	all  standard-compliant	 programs.   It	 turns on -ffast-math,
	   -fallow-store-data-races and	the  Fortran-specific  -fstack-arrays,
	   unless -fmax-stack-var-size is specified, and -fno-protect-parens.

       -Og Optimize  debugging	experience.   -Og  should  be the optimization
	   level of choice for the standard edit-compile-debug cycle, offering
	   a  reasonable  level	 of  optimization   while   maintaining	  fast
	   compilation and a good debugging experience.	 It is a better	choice
	   than	-O0 for	producing debuggable code because some compiler	passes
	   that	collect	debug information are disabled at -O0.

	   Like	 -O0,  -Og completely disables a number	of optimization	passes
	   so  that  individual	 options  controlling  them  have  no  effect.
	   Otherwise  -Og  enables all -O1 optimization	flags except for those
	   that	may interfere with debugging:

	   -fbranch-count-reg	 -fdelayed-branch    -fdse     -fif-conversion
	   -fif-conversion2			-finline-functions-called-once
	   -fmove-loop-invariants   -fssa-phiopt  -ftree-bit-ccp    -ftree-dse
	   -ftree-pta  -ftree-sra

       If you use multiple -O options, with or without level numbers, the last
       such option is the one that is effective.

       Options	of  the	 form  -fflag specify machine-independent flags.  Most
       flags have both positive	and negative forms; the	negative form of -ffoo
       is -fno-foo.  In	the table below, only one of the forms is listed---the
       one you typically use.  You can figure out the  other  form  by	either
       removing	no- or adding it.

       The  following options control specific optimizations.  They are	either
       activated by -O options or are related to ones that are.	 You  can  use
       the   following	 flags	 in  the  rare	cases  when  "fine-tuning"  of
       optimizations to	be performed is	desired.

       -fno-defer-pop
	   For machines	that must pop arguments	after a	function call,	always
	   pop	the arguments as soon as each function returns.	 At levels -O1
	   and higher, -fdefer-pop is the default; this	allows the compiler to
	   let arguments accumulate on the stack for  several  function	 calls
	   and pop them	all at once.

       -fforward-propagate
	   Perform  a  forward	propagation  pass  on  RTL.  The pass tries to
	   combine  two	 instructions  and  checks  if	the  result   can   be
	   simplified.	 If loop unrolling is active, two passes are performed
	   and the second is scheduled after loop unrolling.

	   This	option is enabled by default at	optimization levels  -O,  -O2,
	   -O3,	-Os.

       -ffp-contract=style
	   -ffp-contract=off  disables	floating-point expression contraction.
	   -ffp-contract=fast enables  floating-point  expression  contraction
	   such	 as forming of fused multiply-add operations if	the target has
	   native support for them.  -ffp-contract=on  enables	floating-point
	   expression  contraction  if allowed by the language standard.  This
	   is	currently   not	  implemented	 and	treated	   equal    to
	   -ffp-contract=off.

	   The default is -ffp-contract=fast.

       -fomit-frame-pointer
	   Omit	 the  frame  pointer  in  functions that don't need one.  This
	   avoids the instructions to save,  set  up  and  restore  the	 frame
	   pointer; on many targets it also makes an extra register available.

	   On  some  targets  this  flag  has  no  effect because the standard
	   calling sequence always uses	a  frame  pointer,  so	it  cannot  be
	   omitted.

	   Note	 that  -fno-omit-frame-pointer	doesn't	 guarantee  the	 frame
	   pointer is used in all functions.  Several targets always omit  the
	   frame pointer in leaf functions.

	   Enabled by default at -O and	higher.

       -foptimize-sibling-calls
	   Optimize sibling and	tail recursive calls.

	   Enabled at levels -O2, -O3, -Os.

       -foptimize-strlen
	   Optimize  various  standard	C  string  functions  (e.g.  "strlen",
	   "strchr" or "strcpy") and their "_FORTIFY_SOURCE" counterparts into
	   faster alternatives.

	   Enabled at levels -O2, -O3.

       -fno-inline
	   Do not expand any functions inline apart from those marked with the
	   "always_inline"  attribute.	 This  is   the	  default   when   not
	   optimizing.

	   Single functions can	be exempted from inlining by marking them with
	   the "noinline" attribute.

       -finline-small-functions
	   Integrate  functions	 into their callers when their body is smaller
	   than	expected function call code (so	overall	size of	 program  gets
	   smaller).   The  compiler heuristically decides which functions are
	   simple enough to be worth integrating in this way.	This  inlining
	   applies to all functions, even those	not declared inline.

	   Enabled at levels -O2, -O3, -Os.

       -findirect-inlining
	   Inline  also	 indirect  calls  that	are  discovered	to be known at
	   compile time	thanks to previous  inlining.	This  option  has  any
	   effect   only   when	  inlining   itself   is   turned  on  by  the
	   -finline-functions or -finline-small-functions options.

	   Enabled at levels -O2, -O3, -Os.

       -finline-functions
	   Consider all	functions for inlining,	even if	they are not  declared
	   inline.   The  compiler  heuristically  decides which functions are
	   worth integrating in	this way.

	   If all calls	to a given function are	integrated, and	 the  function
	   is  declared	 "static", then	the function is	normally not output as
	   assembler code in its own right.

	   Enabled at levels -O2, -O3, -Os.  Also enabled by -fprofile-use and
	   -fauto-profile.

       -finline-functions-called-once
	   Consider all	"static" functions called once for inlining into their
	   caller even if they are not marked "inline".	 If a call to a	 given
	   function  is	 integrated,  then  the	 function  is  not  output  as
	   assembler code in its own right.

	   Enabled at levels -O1, -O2, -O3 and -Os, but	not -Og.

       -fearly-inlining
	   Inline functions marked by "always_inline" and functions whose body
	   seems smaller than the function call	overhead  early	 before	 doing
	   -fprofile-generate  instrumentation	and real inlining pass.	 Doing
	   so makes  profiling	significantly  cheaper	and  usually  inlining
	   faster on programs having large chains of nested wrapper functions.

	   Enabled by default.

       -fipa-sra
	   Perform  interprocedural  scalar replacement	of aggregates, removal
	   of unused  parameters  and  replacement  of	parameters  passed  by
	   reference by	parameters passed by value.

	   Enabled at levels -O2, -O3 and -Os.

       -finline-limit=n
	   By  default,	 GCC limits the	size of	functions that can be inlined.
	   This	flag allows coarse control of this limit.  n is	 the  size  of
	   functions that can be inlined in number of pseudo instructions.

	   Inlining  is	 actually  controlled by a number of parameters, which
	   may be specified individually by  using  --param  name=value.   The
	   -finline-limit=n option sets	some of	these parameters as follows:

	   max-inline-insns-single
	       is set to n/2.

	   max-inline-insns-auto
	       is set to n/2.

	   See	 below	for  a	documentation  of  the	individual  parameters
	   controlling inlining	and for	the defaults of	these parameters.

	   Note: there may be no  value	 to  -finline-limit  that  results  in
	   default behavior.

	   Note: pseudo	instruction represents,	in this	particular context, an
	   abstract  measurement  of  function's  size.	  In  no  way  does it
	   represent a count of	assembly instructions and as  such  its	 exact
	   meaning might change	from one release to an another.

       -fno-keep-inline-dllexport
	   This	 is  a	more  fine-grained version of -fkeep-inline-functions,
	   which applies  only	to  functions  that  are  declared  using  the
	   "dllexport" attribute or declspec.

       -fkeep-inline-functions
	   In  C,  emit	"static" functions that	are declared "inline" into the
	   object file,	even if	the function has been inlined into all of  its
	   callers.   This  switch does	not affect functions using the "extern
	   inline" extension in	GNU C90.  In C++,  emit	 any  and  all	inline
	   functions into the object file.

       -fkeep-static-functions
	   Emit	 "static" functions into the object file, even if the function
	   is never used.

       -fkeep-static-consts
	   Emit	variables declared  "static  const"  when  optimization	 isn't
	   turned on, even if the variables aren't referenced.

	   GCC	enables	 this  option  by  default.   If you want to force the
	   compiler to check  if  a  variable  is  referenced,	regardless  of
	   whether    or    not	  optimization	 is   turned   on,   use   the
	   -fno-keep-static-consts option.

       -fmerge-constants
	   Attempt  to	merge  identical  constants  (string   constants   and
	   floating-point constants) across compilation	units.

	   This	 option	 is  the  default  for	optimized  compilation	if the
	   assembler and  linker  support  it.	 Use  -fno-merge-constants  to
	   inhibit this	behavior.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
	   Attempt to merge identical constants	and identical variables.

	   This	   option   implies   -fmerge-constants.    In	 addition   to
	   -fmerge-constants this considers  e.g.  even	 constant  initialized
	   arrays or initialized constant variables with integral or floating-
	   point  types.   Languages  like  C  or  C++	require	each variable,
	   including multiple instances	of  the	 same  variable	 in  recursive
	   calls,  to have distinct locations, so using	this option results in
	   non-conforming behavior.

       -fmodulo-sched
	   Perform  swing  modulo  scheduling  immediately  before  the	 first
	   scheduling  pass.   This pass looks at innermost loops and reorders
	   their instructions by overlapping different iterations.

       -fmodulo-sched-allow-regmoves
	   Perform more	aggressive SMS-based modulo scheduling	with  register
	   moves allowed.  By setting this flag	certain	anti-dependences edges
	   are	deleted,  which	 triggers the generation of reg-moves based on
	   the life-range  analysis.   This  option  is	 effective  only  with
	   -fmodulo-sched enabled.

       -fno-branch-count-reg
	   Disable  the	 optimization pass that	scans for opportunities	to use
	   "decrement and branch" instructions on a count register instead  of
	   instruction sequences that decrement	a register, compare it against
	   zero,  and  then branch based upon the result.  This	option is only
	   meaningful on architectures that support such  instructions,	 which
	   include   x86,   PowerPC,   IA-64   and   S/390.    Note  that  the
	   -fno-branch-count-reg  option  doesn't  remove  the	decrement  and
	   branch   instructions   from	  the	generated  instruction	stream
	   introduced by other optimization passes.

	   The default is -fbranch-count-reg at	-O1  and  higher,  except  for
	   -Og.

       -fno-function-cse
	   Do  not  put	function addresses in registers; make each instruction
	   that	calls a	 constant  function  contain  the  function's  address
	   explicitly.

	   This	 option	results	in less	efficient code,	but some strange hacks
	   that	 alter	the  assembler	output	may   be   confused   by   the
	   optimizations performed when	this option is not used.

	   The default is -ffunction-cse

       -fno-zero-initialized-in-bss
	   If the target supports a BSS	section, GCC by	default	puts variables
	   that	 are initialized to zero into BSS.  This can save space	in the
	   resulting code.

	   This	 option	 turns	off  this  behavior  because   some   programs
	   explicitly  rely  on	variables going	to the data section---e.g., so
	   that	the resulting  executable  can	find  the  beginning  of  that
	   section and/or make assumptions based on that.

	   The default is -fzero-initialized-in-bss.

       -fthread-jumps
	   Perform  optimizations  that	 check	to see if a jump branches to a
	   location where another comparison subsumed by the first  is	found.
	   If  so, the first branch is redirected to either the	destination of
	   the second branch or	a point	immediately following it, depending on
	   whether the condition is known to be	true or	false.

	   Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
	   When	using a	type that occupies multiple registers, such  as	 "long
	   long"  on  a	 32-bit	system,	split the registers apart and allocate
	   them	independently.	This normally generates	better code for	 those
	   types, but may make debugging more difficult.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fsplit-wide-types-early
	   Fully  split	 wide  types early, instead of very late.  This	option
	   has no effect unless	-fsplit-wide-types is turned on.

	   This	is the default on some targets.

       -fcse-follow-jumps
	   In  common  subexpression  elimination  (CSE),  scan	 through  jump
	   instructions	 when  the  target  of	the jump is not	reached	by any
	   other path.	For example, when CSE  encounters  an  "if"  statement
	   with	 an  "else"  clause,  CSE  follows the jump when the condition
	   tested is false.

	   Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
	   This	is similar to -fcse-follow-jumps, but  causes  CSE  to	follow
	   jumps  that	conditionally skip over	blocks.	 When CSE encounters a
	   simple "if" statement with no else clause, -fcse-skip-blocks	causes
	   CSE to follow the jump around the body of the "if".

	   Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
	   Re-run common subexpression elimination  after  loop	 optimizations
	   are performed.

	   Enabled at levels -O2, -O3, -Os.

       -fgcse
	   Perform  a global common subexpression elimination pass.  This pass
	   also	performs global	constant and copy propagation.

	   Note:  When	compiling  a  program  using  computed	gotos,	a  GCC
	   extension,  you  may	get better run-time performance	if you disable
	   the	global	common	subexpression  elimination  pass   by	adding
	   -fno-gcse to	the command line.

	   Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
	   When	 -fgcse-lm is enabled, global common subexpression elimination
	   attempts to	move  loads  that  are	only  killed  by  stores  into
	   themselves.	This allows a loop containing a	load/store sequence to
	   be  changed to a load outside the loop, and a copy/store within the
	   loop.

	   Enabled by default when -fgcse is enabled.

       -fgcse-sm
	   When	-fgcse-sm is enabled, a	store motion pass is run after	global
	   common  subexpression  elimination.	 This  pass  attempts  to move
	   stores out of loops.	 When  used  in	 conjunction  with  -fgcse-lm,
	   loops  containing  a	 load/store  sequence can be changed to	a load
	   before the loop and a store after the loop.

	   Not enabled at any optimization level.

       -fgcse-las
	   When	 -fgcse-las  is	 enabled,  the	global	common	 subexpression
	   elimination	pass eliminates	redundant loads	that come after	stores
	   to the same memory location (both partial and full redundancies).

	   Not enabled at any optimization level.

       -fgcse-after-reload
	   When	-fgcse-after-reload is enabled,	a redundant  load  elimination
	   pass	 is  performed	after  reload.	The purpose of this pass is to
	   clean up redundant spilling.

	   Enabled by -fprofile-use and	-fauto-profile.

       -faggressive-loop-optimizations
	   This	option tells the loop optimizer	to use language	constraints to
	   derive bounds for the number	of iterations of a loop.  This assumes
	   that	loop code does not invoke undefined behavior  by  for  example
	   causing  signed  integer  overflows or out-of-bound array accesses.
	   The bounds for the number of	iterations of a	loop are used to guide
	   loop	unrolling and peeling and loop exit test optimizations.	  This
	   option is enabled by	default.

       -funconstrained-commons
	   This	 option	 tells	the compiler that variables declared in	common
	   blocks (e.g.	Fortran) may later be overridden with longer  trailing
	   arrays.  This prevents certain optimizations	that depend on knowing
	   the array bounds.

       -fcrossjumping
	   Perform cross-jumping transformation.  This transformation  unifies
	   equivalent code and saves code size.	 The resulting code may	or may
	   not perform better than without cross-jumping.

	   Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
	   Combine increments or decrements of addresses with memory accesses.
	   This	 pass  is  always  skipped  on	architectures that do not have
	   instructions	to support this.  Enabled by default at	-O and	higher
	   on architectures that support this.

       -fdce
	   Perform  dead code elimination (DCE)	on RTL.	 Enabled by default at
	   -O and higher.

       -fdse
	   Perform dead	store elimination (DSE)	on RTL.	 Enabled by default at
	   -O and higher.

       -fif-conversion
	   Attempt   to	  transform   conditional   jumps   into   branch-less
	   equivalents.	 This includes use of conditional moves, min, max, set
	   flags  and  abs  instructions,  and	some tricks doable by standard
	   arithmetics.	 The use of conditional	execution on chips where it is
	   available is	controlled by -fif-conversion2.

	   Enabled at levels -O, -O2, -O3, -Os,	but not	with -Og.

       -fif-conversion2
	   Use	conditional   execution	  (where   available)	to   transform
	   conditional jumps into branch-less equivalents.

	   Enabled at levels -O, -O2, -O3, -Os,	but not	with -Og.

       -fdeclone-ctor-dtor
	   The	C++  ABI  requires  multiple entry points for constructors and
	   destructors:	one for	a base subobject, one for a  complete  object,
	   and	one  for  a  virtual  destructor  that	calls  operator	delete
	   afterwards.	For a hierarchy	 with  virtual	bases,	the  base  and
	   complete  variants  are  clones,  which  means  two	copies	of the
	   function.  With this	option,	the base  and  complete	 variants  are
	   changed to be thunks	that call a common implementation.

	   Enabled by -Os.

       -fdelete-null-pointer-checks
	   Assume  that	 programs cannot safely	dereference null pointers, and
	   that	no code	or data	element	resides	at address zero.  This	option
	   enables  simple  constant folding optimizations at all optimization
	   levels.  In addition, other optimization passes  in	GCC  use  this
	   flag	 to  control  global  dataflow analyses	that eliminate useless
	   checks for null pointers; these assume  that	 a  memory  access  to
	   address  zero  always  results  in  a trap, so that if a pointer is
	   checked after it has	already	been dereferenced, it cannot be	null.

	   Note	however	that in	some environments this assumption is not true.
	   Use -fno-delete-null-pointer-checks to  disable  this  optimization
	   for programs	that depend on that behavior.

	   This	option is enabled by default on	most targets.  On Nios II ELF,
	   it  defaults	 to  off.   On	AVR,  CR16, and	MSP430,	this option is
	   completely disabled.

	   Passes that use the dataflow	information are	enabled	 independently
	   at different	optimization levels.

       -fdevirtualize
	   Attempt  to	convert	 calls	to  virtual functions to direct	calls.
	   This	is done	both within a procedure	and interprocedurally as  part
	   of  indirect	 inlining  (-findirect-inlining)  and  interprocedural
	   constant propagation	(-fipa-cp).  Enabled at	levels -O2, -O3, -Os.

       -fdevirtualize-speculatively
	   Attempt to convert calls to virtual functions to speculative	direct
	   calls.  Based on  the  analysis  of	the  type  inheritance	graph,
	   determine for a given call the set of likely	targets. If the	set is
	   small,  preferably  of  size	 1, change the call into a conditional
	   deciding between direct and indirect	calls.	The speculative	 calls
	   enable  more	 optimizations,	 such  as  inlining.   When  they seem
	   useless after further optimization, they are	 converted  back  into
	   original form.

       -fdevirtualize-at-ltrans
	   Stream  extra  information  needed  for aggressive devirtualization
	   when	running	the link-time optimizer	in local transformation	 mode.
	   This	  option   enables  more  devirtualization  but	 significantly
	   increases the size of streamed data.	For this reason	it is disabled
	   by default.

       -fexpensive-optimizations
	   Perform  a  number  of  minor  optimizations	 that  are  relatively
	   expensive.

	   Enabled at levels -O2, -O3, -Os.

       -free
	   Attempt  to	remove	redundant  extension  instructions.   This  is
	   especially helpful for the x86-64  architecture,  which  implicitly
	   zero-extends	 in  64-bit  registers	after  writing	to their lower
	   32-bit half.

	   Enabled for Alpha, AArch64 and x86 at levels	-O2, -O3, -Os.

       -fno-lifetime-dse
	   In C++ the value of an object is only affected  by  changes	within
	   its	lifetime:  when	 the  constructor  begins,  the	 object	has an
	   indeterminate value,	and any	changes	during	the  lifetime  of  the
	   object  are dead when the object is destroyed.  Normally dead store
	   elimination will take advantage of this; if your code relies	on the
	   value of the	object storage persisting beyond the lifetime  of  the
	   object,  you	 can  use  this	flag to	disable	this optimization.  To
	   preserve stores before the constructor starts  (e.g.	 because  your
	   operator  new clears	the object storage) but	still treat the	object
	   as dead after the destructor, you can  use  -flifetime-dse=1.   The
	   default  behavior can be explicitly selected	with -flifetime-dse=2.
	   -flifetime-dse=0 is equivalent to -fno-lifetime-dse.

       -flive-range-shrinkage
	   Attempt to decrease register	pressure through register  live	 range
	   shrinkage.	This  is  helpful  for	fast  processors with small or
	   moderate size register sets.

       -fira-algorithm=algorithm
	   Use the specified coloring algorithm	for  the  integrated  register
	   allocator.  The algorithm argument can be priority, which specifies
	   Chow's  priority  coloring,	or  CB,	which specifies	Chaitin-Briggs
	   coloring.  Chaitin-Briggs  coloring	is  not	 implemented  for  all
	   architectures,  but for those targets that do support it, it	is the
	   default because it generates	better code.

       -fira-region=region
	   Use specified regions for the integrated register  allocator.   The
	   region argument should be one of the	following:

	   all Use  all	 loops	as register allocation regions.	 This can give
	       the best	results	for machines with  a  small  and/or  irregular
	       register	set.

	   mixed
	       Use  all	loops except for loops with small register pressure as
	       the regions.  This value	usually	gives the best results in most
	       cases and for most architectures, and  is  enabled  by  default
	       when compiling with optimization	for speed (-O, -O2, ...).

	   one Use  all	 functions as a	single region.	This typically results
	       in the smallest code size, and is enabled by default for	-Os or
	       -O0.

       -fira-hoist-pressure
	   Use IRA to evaluate register	pressure in the	code hoisting pass for
	   decisions to	hoist expressions.  This  option  usually  results  in
	   smaller code, but it	can slow the compiler down.

	   This	option is enabled at level -Os for all targets.

       -fira-loop-pressure
	   Use	IRA  to	 evaluate  register pressure in	loops for decisions to
	   move	loop invariants.  This option usually results in generation of
	   faster and smaller code on machines with large register  files  (>=
	   32 registers), but it can slow the compiler down.

	   This	option is enabled at level -O3 for some	targets.

       -fno-ira-share-save-slots
	   Disable  sharing  of	 stack	slots  used  for saving	call-used hard
	   registers living  through  a	 call.	 Each  hard  register  gets  a
	   separate  stack  slot,  and	as  a result function stack frames are
	   larger.

       -fno-ira-share-spill-slots
	   Disable sharing of  stack  slots  allocated	for  pseudo-registers.
	   Each	 pseudo-register  that	does  not  get	a hard register	gets a
	   separate stack slot,	and as a  result  function  stack  frames  are
	   larger.

       -flra-remat
	   Enable  CFG-sensitive rematerialization in LRA.  Instead of loading
	   values of spilled pseudos, LRA tries	to rematerialize (recalculate)
	   values if it	is profitable.

	   Enabled at levels -O2, -O3, -Os.

       -fdelayed-branch
	   If  supported  for  the  target   machine,	attempt	  to   reorder
	   instructions	 to  exploit instruction slots available after delayed
	   branch instructions.

	   Enabled at levels -O, -O2, -O3, -Os,	but not	at -Og.

       -fschedule-insns
	   If  supported  for  the  target   machine,	attempt	  to   reorder
	   instructions	 to  eliminate	execution  stalls due to required data
	   being unavailable.  This helps machines  that  have	slow  floating
	   point or memory load	instructions by	allowing other instructions to
	   be	issued	 until	the  result  of	 the  load  or	floating-point
	   instruction is required.

	   Enabled at levels -O2, -O3.

       -fschedule-insns2
	   Similar to -fschedule-insns,	but requests  an  additional  pass  of
	   instruction	scheduling  after  register  allocation	has been done.
	   This	is especially useful  on  machines  with  a  relatively	 small
	   number  of  registers  and where memory load	instructions take more
	   than	one cycle.

	   Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
	   Disable  instruction	 scheduling  across  basic  blocks,  which  is
	   normally  enabled  when scheduling before register allocation, i.e.
	   with	-fschedule-insns or at -O2 or higher.

       -fno-sched-spec
	   Disable speculative	motion	of  non-load  instructions,  which  is
	   normally  enabled  when scheduling before register allocation, i.e.
	   with	-fschedule-insns or at -O2 or higher.

       -fsched-pressure
	   Enable register pressure sensitive insn scheduling before  register
	   allocation.	 This only makes sense when scheduling before register
	   allocation is enabled, i.e. with  -fschedule-insns  or  at  -O2  or
	   higher.   Usage  of	this option can	improve	the generated code and
	   decrease its	size by	preventing register  pressure  increase	 above
	   the	number	of  available  hard registers and subsequent spills in
	   register allocation.

       -fsched-spec-load
	   Allow speculative motion of	some  load  instructions.   This  only
	   makes  sense	 when scheduling before	register allocation, i.e. with
	   -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
	   Allow speculative motion of	more  load  instructions.   This  only
	   makes  sense	 when scheduling before	register allocation, i.e. with
	   -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
	   Define how many insns (if any) can be moved	prematurely  from  the
	   queue  of  stalled  insns  into  the	 ready	list during the	second
	   scheduling pass.  -fno-sched-stalled-insns means that no insns  are
	   moved  prematurely, -fsched-stalled-insns=0 means there is no limit
	   on	how   many   queued   insns   can   be	 moved	  prematurely.
	   -fsched-stalled-insns    without   a	  value	  is   equivalent   to
	   -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
	   Define how many insn	groups (cycles)	are examined for a  dependency
	   on  a  stalled  insn	that is	a candidate for	premature removal from
	   the queue of	stalled	insns.	This has an  effect  only  during  the
	   second  scheduling pass, and	only if	-fsched-stalled-insns is used.
	   -fno-sched-stalled-insns-dep	       is	 equivalent	    to
	   -fsched-stalled-insns-dep=0.	  -fsched-stalled-insns-dep  without a
	   value is equivalent to -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
	   When	 scheduling  after   register	allocation,   use   superblock
	   scheduling.	 This  allows  motion  across  basic block boundaries,
	   resulting in	faster schedules.  This	option is experimental,	as not
	   all machine descriptions used by GCC	model the CPU  closely	enough
	   to avoid unreliable results from the	algorithm.

	   This	 only  makes  sense when scheduling after register allocation,
	   i.e.	with -fschedule-insns2 or at -O2 or higher.

       -fsched-group-heuristic
	   Enable the group heuristic in the scheduler.	 This heuristic	favors
	   the instruction that	belongs	to a schedule group.  This is  enabled
	   by  default	when scheduling	is enabled, i.e. with -fschedule-insns
	   or -fschedule-insns2	or at -O2 or higher.

       -fsched-critical-path-heuristic
	   Enable  the	critical-path  heuristic  in  the   scheduler.	  This
	   heuristic  favors  instructions  on	the  critical  path.   This is
	   enabled  by	default	 when  scheduling  is	enabled,   i.e.	  with
	   -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-spec-insn-heuristic
	   Enable  the	speculative  instruction  heuristic  in	the scheduler.
	   This	 heuristic  favors  speculative	 instructions	with   greater
	   dependency weakness.	 This is enabled by default when scheduling is
	   enabled, i.e.  with -fschedule-insns	or -fschedule-insns2 or	at -O2
	   or higher.

       -fsched-rank-heuristic
	   Enable  the rank heuristic in the scheduler.	 This heuristic	favors
	   the instruction belonging to	a basic	block  with  greater  size  or
	   frequency.	This is	enabled	by default when	scheduling is enabled,
	   i.e.	 with -fschedule-insns	or  -fschedule-insns2  or  at  -O2  or
	   higher.

       -fsched-last-insn-heuristic
	   Enable  the	last-instruction  heuristic  in	 the  scheduler.  This
	   heuristic favors the	instruction that is less dependent on the last
	   instruction scheduled.  This	is enabled by default when  scheduling
	   is  enabled,	 i.e. with -fschedule-insns or -fschedule-insns2 or at
	   -O2 or higher.

       -fsched-dep-count-heuristic
	   Enable  the	dependent-count	 heuristic  in	the  scheduler.	  This
	   heuristic   favors  the  instruction	 that  has  more  instructions
	   depending on	it.  This is enabled by	 default  when	scheduling  is
	   enabled, i.e.  with -fschedule-insns	or -fschedule-insns2 or	at -O2
	   or higher.

       -freschedule-modulo-scheduled-loops
	   Modulo scheduling is	performed before traditional scheduling.  If a
	   loop	 is  modulo  scheduled,	later scheduling passes	may change its
	   schedule.  Use this option to control that behavior.

       -fselective-scheduling
	   Schedule  instructions  using   selective   scheduling   algorithm.
	   Selective scheduling	runs instead of	the first scheduler pass.

       -fselective-scheduling2
	   Schedule   instructions   using   selective	scheduling  algorithm.
	   Selective scheduling	runs instead of	the second scheduler pass.

       -fsel-sched-pipelining
	   Enable software pipelining  of  innermost  loops  during  selective
	   scheduling.	  This	 option	  has	no   effect   unless   one  of
	   -fselective-scheduling or -fselective-scheduling2 is	turned on.

       -fsel-sched-pipelining-outer-loops
	   When	pipelining loops during	selective  scheduling,	also  pipeline
	   outer    loops.     This    option	 has	no    effect	unless
	   -fsel-sched-pipelining is turned on.

       -fsemantic-interposition
	   Some	object formats,	like ELF, allow	interposing of symbols by  the
	   dynamic linker.  This means that for	symbols	exported from the DSO,
	   the	compiler  cannot perform interprocedural propagation, inlining
	   and other  optimizations  in	 anticipation  that  the  function  or
	   variable  in	question may change. While this	feature	is useful, for
	   example, to rewrite memory  allocation  functions  by  a  debugging
	   implementation, it is expensive in the terms	of code	quality.  With
	   -fno-semantic-interposition	  the	compiler   assumes   that   if
	   interposition happens for functions the overwriting	function  will
	   have	precisely the same semantics (and side effects).  Similarly if
	   interposition   happens  for	 variables,  the  constructor  of  the
	   variable will be the	same. The flag has  no	effect	for  functions
	   explicitly	declared   inline  (where  it  is  never  allowed  for
	   interposition to  change  semantics)	 and  for  symbols  explicitly
	   declared weak.

       -fshrink-wrap
	   Emit	function prologues only	before parts of	the function that need
	   it,	rather	than at	the top	of the function.  This flag is enabled
	   by default at -O and	higher.

       -fshrink-wrap-separate
	   Shrink-wrap separate	parts of the prologue and epilogue separately,
	   so that those parts are only	executed when needed.  This option  is
	   on  by  default,  but  has  no  effect unless -fshrink-wrap is also
	   turned on and the target supports this.

       -fcaller-saves
	   Enable allocation of	values to  registers  that  are	 clobbered  by
	   function  calls, by emitting	extra instructions to save and restore
	   the registers around	such calls.  Such allocation is	done only when
	   it seems to result in better	code.

	   This	option is always  enabled  by  default	on  certain  machines,
	   usually  those  which  have	no  call-preserved  registers  to  use
	   instead.

	   Enabled at levels -O2, -O3, -Os.

       -fcombine-stack-adjustments
	   Tracks  stack  adjustments  (pushes	and  pops)  and	 stack	memory
	   references and then tries to	find ways to combine them.

	   Enabled by default at -O1 and higher.

       -fipa-ra
	   Use caller save registers for allocation if those registers are not
	   used	 by  any called	function.  In that case	it is not necessary to
	   save	and restore them around	 calls.	  This	is  only  possible  if
	   called  functions  are  part	 of  same  compilation unit as current
	   function and	they are compiled before it.

	   Enabled at levels -O2, -O3, -Os, however the	option is disabled  if
	   generated  code  will be instrumented for profiling (-p, or -pg) or
	   if callee's register	usage cannot be	known exactly (this happens on
	   targets that	do not expose prologues	and epilogues in RTL).

       -fconserve-stack
	   Attempt to minimize stack usage.  The compiler attempts to use less
	   stack space,	even if	that makes the program	slower.	  This	option
	   implies  setting  the  large-stack-frame  parameter	to 100 and the
	   large-stack-frame-growth parameter to 400.

       -ftree-reassoc
	   Perform reassociation on trees.  This flag is enabled by default at
	   -O and higher.

       -fcode-hoisting
	   Perform code	hoisting.  Code	hoisting tries to move the  evaluation
	   of  expressions executed on all paths to the	function exit as early
	   as  possible.   This	 is  especially	 useful	  as   a   code	  size
	   optimization, but it	often helps for	code speed as well.  This flag
	   is enabled by default at -O2	and higher.

       -ftree-pre
	   Perform  partial  redundancy	elimination (PRE) on trees.  This flag
	   is enabled by default at -O2	and -O3.

       -ftree-partial-pre
	   Make	partial	redundancy elimination (PRE)  more  aggressive.	  This
	   flag	is enabled by default at -O3.

       -ftree-forwprop
	   Perform  forward  propagation  on  trees.   This flag is enabled by
	   default at -O and higher.

       -ftree-fre
	   Perform full	redundancy elimination (FRE) on	trees.	The difference
	   between FRE and PRE is that FRE only	considers expressions that are
	   computed on all paths leading to the	redundant  computation.	  This
	   analysis  is	faster than PRE, though	it exposes fewer redundancies.
	   This	flag is	enabled	by default at -O and higher.

       -ftree-phiprop
	   Perform hoisting of loads from conditional pointers on trees.  This
	   pass	is enabled by default at -O and	higher.

       -fhoist-adjacent-loads
	   Speculatively hoist loads from both branches	of an if-then-else  if
	   the loads are from adjacent locations in the	same structure and the
	   target  architecture	has a conditional move instruction.  This flag
	   is enabled by default at -O2	and higher.

       -ftree-copy-prop
	   Perform  copy  propagation  on   trees.    This   pass   eliminates
	   unnecessary copy operations.	 This flag is enabled by default at -O
	   and higher.

       -fipa-pure-const
	   Discover  which functions are pure or constant.  Enabled by default
	   at -O and higher.

       -fipa-reference
	   Discover which static variables do not escape the compilation unit.
	   Enabled by default at -O and	higher.

       -fipa-reference-addressable
	   Discover   read-only,   write-only	and   non-addressable	static
	   variables.  Enabled by default at -O	and higher.

       -fipa-stack-alignment
	   Reduce  stack  alignment  on	 call  sites  if possible.  Enabled by
	   default.

       -fipa-pta
	   Perform  interprocedural  pointer  analysis	 and   interprocedural
	   modification	  and  reference  analysis.   This  option  can	 cause
	   excessive memory and	compile-time usage on large compilation	units.
	   It is not enabled by	default	at any optimization level.

       -fipa-profile
	   Perform interprocedural profile propagation.	 The functions	called
	   only	 from  cold  functions	are  marked  as	 cold.	Also functions
	   executed once (such as "cold", "noreturn", static  constructors  or
	   destructors)	 are identified. Cold functions	and loop less parts of
	   functions executed once are then optimized for  size.   Enabled  by
	   default at -O and higher.

       -fipa-modref
	   Perform   interprocedural   mod/ref	analysis.   This  optimization
	   analyzes the	side effects of	functions (memory locations  that  are
	   modified  or	referenced) and	enables	better optimization across the
	   function call boundary.  This flag is enabled by default at -O  and
	   higher.

       -fipa-cp
	   Perform  interprocedural  constant  propagation.  This optimization
	   analyzes the	program	to determine when values passed	 to  functions
	   are	constants  and	then optimizes accordingly.  This optimization
	   can substantially  increase	performance  if	 the  application  has
	   constants  passed to	functions.  This flag is enabled by default at
	   -O2,	-Os  and  -O3.	 It  is	 also  enabled	by  -fprofile-use  and
	   -fauto-profile.

       -fipa-cp-clone
	   Perform   function	cloning	  to   make  interprocedural  constant
	   propagation	stronger.   When  enabled,  interprocedural   constant
	   propagation	performs  function  cloning  when  externally  visible
	   function can	be  called  with  constant  arguments.	 Because  this
	   optimization	 can  create  multiple	copies	of  functions,	it may
	   significantly     increase	  code	   size	     (see      --param
	   ipa-cp-unit-growth=value).  This flag is enabled by default at -O3.
	   It is also enabled by -fprofile-use and -fauto-profile.

       -fipa-bit-cp
	   When	enabled, perform interprocedural bitwise constant propagation.
	   This	 flag  is  enabled  by default at -O2 and by -fprofile-use and
	   -fauto-profile.  It requires	that -fipa-cp is enabled.

       -fipa-vrp
	   When	enabled, perform interprocedural propagation of	value  ranges.
	   This	 flag  is enabled by default at	-O2. It	requires that -fipa-cp
	   is enabled.

       -fipa-icf
	   Perform  Identical  Code  Folding  for  functions   and   read-only
	   variables.	The  optimization  reduces  code  size and may disturb
	   unwind stacks by replacing a	function  by  equivalent  one  with  a
	   different  name. The	optimization works more	effectively with link-
	   time	optimization enabled.

	   Although  the  behavior  is	similar	 to  the  Gold	Linker's   ICF
	   optimization,  GCC  ICF  works  on  different  levels  and thus the
	   optimizations are not same -	there are equivalences that are	 found
	   only	by GCC and equivalences	found only by Gold.

	   This	flag is	enabled	by default at -O2 and -Os.

       -flive-patching=level
	   Control  GCC's  optimizations  to produce output suitable for live-
	   patching.

	   If  the  compiler's	optimization  uses  a	function's   body   or
	   information	extracted  from	 its  body  to optimize/change another
	   function, the latter	is called an impacted function of the  former.
	   If  a function is patched, its impacted functions should be patched
	   too.

	   The	impacted  functions   are   determined	 by   the   compiler's
	   interprocedural  optimizations.   For example, a caller is impacted
	   when	inlining a function into its caller, cloning  a	 function  and
	   changing  its  caller  to  call  this  new  clone,  or extracting a
	   function's pureness/constness information to	optimize its direct or
	   indirect callers, etc.

	   Usually, the	more IPA optimizations enabled,	the larger the	number
	   of  impacted	 functions for each function.  In order	to control the
	   number of impacted functions	and more easily	compute	 the  list  of
	   impacted  function,	IPA  optimizations can be partially enabled at
	   two different levels.

	   The level argument should be	one of the following:

	   inline-clone
	       Only enable inlining and	cloning	optimizations, which  includes
	       inlining,   cloning,   interprocedural  scalar  replacement  of
	       aggregates and partial inlining.	 As a result, when patching  a
	       function, all its callers and its clones' callers are impacted,
	       therefore need to be patched as well.

	       -flive-patching=inline-clone	disables     the     following
	       optimization flags: -fwhole-program  -fipa-pta  -fipa-reference
	       -fipa-ra	 -fipa-icf   -fipa-icf-functions   -fipa-icf-variables
	       -fipa-bit-cp		-fipa-vrp	      -fipa-pure-const
	       -fipa-reference-addressable -fipa-stack-alignment -fipa-modref

	   inline-only-static
	       Only enable inlining of static functions.  As  a	 result,  when
	       patching	a static function, all its callers are impacted	and so
	       need to be patched as well.

	       In  addition to all the flags that -flive-patching=inline-clone
	       disables,   -flive-patching=inline-only-static	disables   the
	       following   additional	optimization   flags:	-fipa-cp-clone
	       -fipa-sra  -fpartial-inlining  -fipa-cp

	   When	-flive-patching	is specified without any  value,  the  default
	   value is inline-clone.

	   This	flag is	disabled by default.

	   Note	  that	 -flive-patching   is  not  supported  with  link-time
	   optimization	(-flto).

       -fisolate-erroneous-paths-dereference
	   Detect paths	that trigger erroneous or undefined  behavior  due  to
	   dereferencing  a  null  pointer.  Isolate those paths from the main
	   control flow	and turn the statement	with  erroneous	 or  undefined
	   behavior  into  a trap.  This flag is enabled by default at -O2 and
	   higher  and	depends	 on  -fdelete-null-pointer-checks  also	 being
	   enabled.

       -fisolate-erroneous-paths-attribute
	   Detect  paths that trigger erroneous	or undefined behavior due to a
	   null	value being used in a way forbidden by a "returns_nonnull"  or
	   "nonnull"  attribute.   Isolate  those  paths from the main control
	   flow	and turn the statement with erroneous  or  undefined  behavior
	   into	 a trap.  This is not currently	enabled, but may be enabled by
	   -O2 in the future.

       -ftree-sink
	   Perform forward store motion	on trees.  This	 flag  is  enabled  by
	   default at -O and higher.

       -ftree-bit-ccp
	   Perform  sparse  conditional	 bit constant propagation on trees and
	   propagate pointer alignment information.  This pass	only  operates
	   on  local  scalar  variables	 and  is enabled by default at -O1 and
	   higher, except for -Og.  It requires	that -ftree-ccp	is enabled.

       -ftree-ccp
	   Perform sparse conditional constant	propagation  (CCP)  on	trees.
	   This	pass only operates on local scalar variables and is enabled by
	   default at -O and higher.

       -fssa-backprop
	   Propagate information about uses of a value up the definition chain
	   in  order  to  simplify  the	 definitions.	For example, this pass
	   strips sign operations if the sign of a value never	matters.   The
	   flag	is enabled by default at -O and	higher.

       -fssa-phiopt
	   Perform  pattern  matching on SSA PHI nodes to optimize conditional
	   code.  This pass is enabled by default at -O1  and  higher,	except
	   for -Og.

       -ftree-switch-conversion
	   Perform  conversion	of  simple  initializations  in	 a  switch  to
	   initializations from	a scalar  array.   This	 flag  is  enabled  by
	   default at -O2 and higher.

       -ftree-tail-merge
	   Look	 for identical code sequences.	When found, replace one	with a
	   jump	to the other.  This optimization is known as tail  merging  or
	   cross  jumping.  This flag is enabled by default at -O2 and higher.
	   The compilation time	in this	pass can be  limited  using  max-tail-
	   merge-comparisons	 parameter    and    max-tail-merge-iterations
	   parameter.

       -ftree-dce
	   Perform dead	code elimination (DCE) on trees.  This flag is enabled
	   by default at -O and	higher.

       -ftree-builtin-call-dce
	   Perform conditional dead code elimination (DCE) for calls to	built-
	   in functions	that may set "errno" but are otherwise	free  of  side
	   effects.   This flag	is enabled by default at -O2 and higher	if -Os
	   is not also specified.

       -ffinite-loops
	   Assume that a loop with an exit will	eventually take	the  exit  and
	   not	loop  indefinitely.   This allows the compiler to remove loops
	   that	otherwise  have	 no  side-effects,  not	 considering  eventual
	   endless looping as such.

	   This	option is enabled by default at	-O2 for	C++ with -std=c++11 or
	   higher.

       -ftree-dominator-opts
	   Perform   a	 variety  of  simple  scalar  cleanups	(constant/copy
	   propagation,	 redundancy   elimination,   range   propagation   and
	   expression  simplification)	based  on  a dominator tree traversal.
	   This	also performs jump threading (to reduce	jumps to jumps).  This
	   flag	is enabled by default at -O and	higher.

       -ftree-dse
	   Perform  dead  store	elimination (DSE) on trees.  A dead store is a
	   store into a	memory location	that is	later overwritten  by  another
	   store  without  any	intervening  loads.   In this case the earlier
	   store can be	deleted.  This flag is enabled by default  at  -O  and
	   higher.

       -ftree-ch
	   Perform  loop header	copying	on trees.  This	is beneficial since it
	   increases effectiveness of  code  motion  optimizations.   It  also
	   saves  one jump.  This flag is enabled by default at	-O and higher.
	   It is not enabled for -Os, since it usually increases code size.

       -ftree-loop-optimize
	   Perform loop	optimizations on  trees.   This	 flag  is  enabled  by
	   default at -O and higher.

       -ftree-loop-linear
       -floop-strip-mine
       -floop-block
	   Perform loop	nest optimizations.  Same as -floop-nest-optimize.  To
	   use	this  code  transformation,  GCC  has  to  be  configured with
	   --with-isl	to   enable   the   Graphite	loop	transformation
	   infrastructure.

       -fgraphite-identity
	   Enable the identity transformation for graphite.  For every SCoP we
	   generate  the  polyhedral  representation  and transform it back to
	   gimple.  Using  -fgraphite-identity	we  can	 check	the  costs  or
	   benefits  of	the GIMPLE -> GRAPHITE -> GIMPLE transformation.  Some
	   minimal optimizations are also performed by the code	generator isl,
	   like	index splitting	and dead code elimination in loops.

       -floop-nest-optimize
	   Enable the isl based	loop nest optimizer.  This is a	 generic  loop
	   nest	 optimizer  based  on  the  Pluto optimization algorithms.  It
	   calculates  a  loop	structure  optimized  for  data-locality   and
	   parallelism.	 This option is	experimental.

       -floop-parallelize-all
	   Use	the  Graphite  data dependence analysis	to identify loops that
	   can be  parallelized.   Parallelize	all  the  loops	 that  can  be
	   analyzed  to	 not contain loop carried dependences without checking
	   that	it is profitable to parallelize	the loops.

       -ftree-coalesce-vars
	   While transforming the  program  out	 of  the  SSA  representation,
	   attempt to reduce copying by	coalescing versions of different user-
	   defined  variables, instead of just compiler	temporaries.  This may
	   severely limit the ability to debug an optimized  program  compiled
	   with	-fno-var-tracking-assignments.	In the negated form, this flag
	   prevents  SSA coalescing of user variables.	This option is enabled
	   by default if optimization is enabled,  and	it  does  very	little
	   otherwise.

       -ftree-loop-if-convert
	   Attempt  to	transform  conditional jumps in	the innermost loops to
	   branch-less equivalents.  The intent	is to remove control-flow from
	   the innermost  loops	 in  order  to	improve	 the  ability  of  the
	   vectorization  pass	to  handle  these  loops.   This is enabled by
	   default if vectorization is enabled.

       -ftree-loop-distribution
	   Perform loop	distribution.  This flag can improve cache performance
	   on big loop bodies  and  allow  further  loop  optimizations,  like
	   parallelization  or vectorization, to take place.  For example, the
	   loop

		   DO I	= 1, N
		     A(I) = B(I) + C
		     D(I) = E(I) * F
		   ENDDO

	   is transformed to

		   DO I	= 1, N
		      A(I) = B(I) + C
		   ENDDO
		   DO I	= 1, N
		      D(I) = E(I) * F
		   ENDDO

	   This	flag is	enabled	by default at -O3.   It	 is  also  enabled  by
	   -fprofile-use and -fauto-profile.

       -ftree-loop-distribute-patterns
	   Perform  loop  distribution	of patterns that can be	code generated
	   with	calls to a library.  This flag is enabled by  default  at  -O2
	   and higher, and by -fprofile-use and	-fauto-profile.

	   This	pass distributes the initialization loops and generates	a call
	   to memset zero.  For	example, the loop

		   DO I	= 1, N
		     A(I) = 0
		     B(I) = A(I) + I
		   ENDDO

	   is transformed to

		   DO I	= 1, N
		      A(I) = 0
		   ENDDO
		   DO I	= 1, N
		      B(I) = A(I) + I
		   ENDDO

	   and	the  initialization  loop is transformed into a	call to	memset
	   zero.  This flag is enabled by default at -O3.  It is also  enabled
	   by -fprofile-use and	-fauto-profile.

       -floop-interchange
	   Perform  loop  interchange  outside	of  graphite.	This  flag can
	   improve cache performance on	 loop  nest  and  allow	 further  loop
	   optimizations, like vectorization, to take place.  For example, the
	   loop

		   for (int i =	0; i < N; i++)
		     for (int j	= 0; j < N; j++)
		       for (int	k = 0; k < N; k++)
			 c[i][j] = c[i][j] + a[i][k]*b[k][j];

	   is transformed to

		   for (int i =	0; i < N; i++)
		     for (int k	= 0; k < N; k++)
		       for (int	j = 0; j < N; j++)
			 c[i][j] = c[i][j] + a[i][k]*b[k][j];

	   This	 flag  is  enabled  by	default	at -O3.	 It is also enabled by
	   -fprofile-use and -fauto-profile.

       -floop-unroll-and-jam
	   Apply unroll	and jam	transformations	on feasible loops.  In a  loop
	   nest	 this  unrolls	the  outer  loop  by some factor and fuses the
	   resulting multiple inner loops.  This flag is enabled by default at
	   -O3.	 It is also enabled by -fprofile-use and -fauto-profile.

       -ftree-loop-im
	   Perform loop	invariant motion  on  trees.   This  pass  moves  only
	   invariants  that  are  hard to handle at RTL	level (function	calls,
	   operations that expand to nontrivial	 sequences  of	insns).	  With
	   -funswitch-loops  it	 also  moves  operands	of conditions that are
	   invariant out of  the  loop,	 so  that  we  can  use	 just  trivial
	   invariantness analysis in loop unswitching.	The pass also includes
	   store motion.

       -ftree-loop-ivcanon
	   Create  a  canonical	 counter for number of iterations in loops for
	   which  determining  number  of  iterations	requires   complicated
	   analysis.   Later  optimizations  then  may	determine  the	number
	   easily.  Useful especially in connection with unrolling.

       -ftree-scev-cprop
	   Perform final value replacement.  If	a variable is  modified	 in  a
	   loop	 in  such  a  way  that	its value when exiting the loop	can be
	   determined using only its initial value  and	 the  number  of  loop
	   iterations,	replace	uses of	the final value	by such	a computation,
	   provided it is sufficiently cheap.  This reduces data  dependencies
	   and	may  allow  further simplifications.  Enabled by default at -O
	   and higher.

       -fivopts
	   Perform  induction  variable	 optimizations	(strength   reduction,
	   induction  variable	merging	and induction variable elimination) on
	   trees.

       -ftree-parallelize-loops=n
	   Parallelize loops, i.e., split their	iteration space	to  run	 in  n
	   threads.   This  is	only  possible	for loops whose	iterations are
	   independent and can be arbitrarily reordered.  The optimization  is
	   only	profitable on multiprocessor machines, for loops that are CPU-
	   intensive,  rather than constrained e.g. by memory bandwidth.  This
	   option implies -pthread, and	thus is	only supported on targets that
	   have	support	for -pthread.

       -ftree-pta
	   Perform function-local points-to analysis on	trees.	This  flag  is
	   enabled by default at -O1 and higher, except	for -Og.

       -ftree-sra
	   Perform  scalar  replacement	 of  aggregates.   This	 pass replaces
	   structure references	with scalars to	prevent	committing  structures
	   to  memory  too  early.  This flag is enabled by default at -O1 and
	   higher, except for -Og.

       -fstore-merging
	   Perform merging of narrow stores to consecutive  memory  addresses.
	   This	 pass  merges  contiguous  stores of immediate values narrower
	   than	a word into  fewer  wider  stores  to  reduce  the  number  of
	   instructions.  This is enabled by default at	-O2 and	higher as well
	   as -Os.

       -ftree-ter
	   Perform  temporary  expression  replacement	during the SSA->normal
	   phase.  Single use/single def temporaries are replaced at their use
	   location with their defining	 expression.   This  results  in  non-
	   GIMPLE  code,  but  gives  the expanders much more complex trees to
	   work	on resulting in	better RTL generation.	 This  is  enabled  by
	   default at -O and higher.

       -ftree-slsr
	   Perform straight-line strength reduction on trees.  This recognizes
	   related  expressions	involving multiplications and replaces them by
	   less	expensive calculations when  possible.	 This  is  enabled  by
	   default at -O and higher.

       -ftree-vectorize
	   Perform    vectorization    on    trees.    This    flag    enables
	   -ftree-loop-vectorize and -ftree-slp-vectorize  if  not  explicitly
	   specified.

       -ftree-loop-vectorize
	   Perform  loop  vectorization	 on  trees.  This  flag	 is enabled by
	   default  at	-O3  and  by  -ftree-vectorize,	  -fprofile-use,   and
	   -fauto-profile.

       -ftree-slp-vectorize
	   Perform basic block vectorization on	trees. This flag is enabled by
	   default   at	  -O3  and  by	-ftree-vectorize,  -fprofile-use,  and
	   -fauto-profile.

       -fvect-cost-model=model
	   Alter the cost model	used for vectorization.	  The  model  argument
	   should be one of unlimited, dynamic,	cheap or very-cheap.  With the
	   unlimited   model   the  vectorized	code-path  is  assumed	to  be
	   profitable while with the dynamic model a runtime check guards  the
	   vectorized  code-path  to  enable it	only for iteration counts that
	   will	likely execute faster than when	executing the original	scalar
	   loop.   The cheap model disables vectorization of loops where doing
	   so would be cost prohibitive	for example due	 to  required  runtime
	   checks  for	data dependence	or alignment but otherwise is equal to
	   the dynamic model.  The very-cheap model only allows	 vectorization
	   if  the  vector code	would entirely replace the scalar code that is
	   being vectorized.  For example, if each iteration of	 a  vectorized
	   loop	 would	only  be able to handle	exactly	four iterations	of the
	   scalar loop,	the very-cheap model would only	allow vectorization if
	   the scalar iteration	count is known to be a multiple	of four.

	   The default cost model depends on other optimization	flags  and  is
	   either dynamic or cheap.

       -fsimd-cost-model=model
	   Alter  the  cost  model used	for vectorization of loops marked with
	   the OpenMP simd directive.  The model argument  should  be  one  of
	   unlimited,  dynamic,	 cheap.	  All  values  of  model have the same
	   meaning as described	in -fvect-cost-model and  by  default  a  cost
	   model defined with -fvect-cost-model	is used.

       -ftree-vrp
	   Perform  Value  Range Propagation on	trees.	This is	similar	to the
	   constant propagation	pass, but instead of values, ranges of	values
	   are	propagated.   This allows the optimizers to remove unnecessary
	   range checks	like array bound checks	and null pointer checks.  This
	   is enabled by default  at  -O2  and	higher.	  Null	pointer	 check
	   elimination	 is   only  done  if  -fdelete-null-pointer-checks  is
	   enabled.

       -fsplit-paths
	   Split paths leading to loop backedges.  This	can improve dead  code
	   elimination	and common subexpression elimination.  This is enabled
	   by default at -O3 and above.

       -fsplit-ivs-in-unroller
	   Enables expression  of  values  of  induction  variables  in	 later
	   iterations  of  the	unrolled  loop	using  the  value in the first
	   iteration.  This breaks  long  dependency  chains,  thus  improving
	   efficiency of the scheduling	passes.

	   A  combination  of  -fweb and CSE is	often sufficient to obtain the
	   same	effect.	 However, that is not reliable in cases	where the loop
	   body	is more	complicated than a single basic	block.	It  also  does
	   not	work  at  all on some architectures due	to restrictions	in the
	   CSE pass.

	   This	optimization is	enabled	by default.

       -fvariable-expansion-in-unroller
	   With	this option, the compiler  creates  multiple  copies  of  some
	   local variables when	unrolling a loop, which	can result in superior
	   code.

	   This	 optimization  is  enabled by default for PowerPC targets, but
	   disabled by default otherwise.

       -fpartial-inlining
	   Inline parts	of functions.  This option has any  effect  only  when
	   inlining   itself   is  turned  on  by  the	-finline-functions  or
	   -finline-small-functions options.

	   Enabled at levels -O2, -O3, -Os.

       -fpredictive-commoning
	   Perform   predictive	  commoning   optimization,   i.e.,    reusing
	   computations	 (especially  memory  loads  and  stores) performed in
	   previous iterations of loops.

	   This	option is enabled  at  level  -O3.   It	 is  also  enabled  by
	   -fprofile-use and -fauto-profile.

       -fprefetch-loop-arrays
	   If  supported  by  the  target  machine,  generate  instructions to
	   prefetch memory to improve the performance  of  loops  that	access
	   large arrays.

	   This	 option	 may generate better or	worse code; results are	highly
	   dependent on	the structure of loops within the source code.

	   Disabled at level -Os.

       -fno-printf-return-value
	   Do not substitute constants for known  return  value	 of  formatted
	   output  functions  such  as	"sprintf", "snprintf", "vsprintf", and
	   "vsnprintf" (but not	"printf" of "fprintf").	  This	transformation
	   allows  GCC	to  optimize  or  even eliminate branches based	on the
	   known return	value of these functions called	 with  arguments  that
	   are	either	constant,  or  whose values are	known to be in a range
	   that	makes  determining  the	 exact	return	value  possible.   For
	   example,  when  -fprintf-return-value is in effect, both the	branch
	   and the body	of the "if" statement (but not the call	to  "snprint")
	   can	be  optimized  away  when  "i"	is a 32-bit or smaller integer
	   because the return value is guaranteed to be	at most	8.

		   char	buf[9];
		   if (snprintf	(buf, "%08x", i) >= sizeof buf)
		     ...

	   The -fprintf-return-value option relies on other optimizations  and
	   yields  best	 results  with -O2 and above.  It works	in tandem with
	   the	-Wformat-overflow  and	 -Wformat-truncation   options.	   The
	   -fprintf-return-value option	is enabled by default.

       -fno-peephole
       -fno-peephole2
	   Disable   any   machine-specific   peephole	 optimizations.	   The
	   difference between -fno-peephole and	-fno-peephole2 is in how  they
	   are implemented in the compiler; some targets use one, some use the
	   other, a few	use both.

	   -fpeephole  is  enabled  by default.	 -fpeephole2 enabled at	levels
	   -O2,	-O3, -Os.

       -fno-guess-branch-probability
	   Do not guess	branch probabilities using heuristics.

	   GCC uses heuristics to guess	branch probabilities if	they  are  not
	   provided  by	profiling feedback (-fprofile-arcs).  These heuristics
	   are based on	the control flow graph.	 If some branch	 probabilities
	   are	specified  by "__builtin_expect", then the heuristics are used
	   to guess branch probabilities for the  rest	of  the	 control  flow
	   graph,  taking  the	"__builtin_expect"  info  into	account.   The
	   interactions	between	the heuristics and "__builtin_expect"  can  be
	   complex,  and  in  some  cases,  it	may  be	 useful	to disable the
	   heuristics so that the effects of "__builtin_expect"	are easier  to
	   understand.

	   It  is  also	 possible  to  specify	expected  probability  of  the
	   expression	with   "__builtin_expect_with_probability"    built-in
	   function.

	   The	default	 is -fguess-branch-probability at levels -O, -O2, -O3,
	   -Os.

       -freorder-blocks
	   Reorder basic blocks	in the compiled	function in  order  to	reduce
	   number of taken branches and	improve	code locality.

	   Enabled at levels -O, -O2, -O3, -Os.

       -freorder-blocks-algorithm=algorithm
	   Use	the  specified	algorithm  for	basic  block  reordering.  The
	   algorithm argument can be simple, which does	not increase code size
	   (except sometimes due to secondary effects like alignment), or stc,
	   the "software trace cache" algorithm, which tries to	put all	 often
	   executed  code together, minimizing the number of branches executed
	   by making extra copies of code.

	   The default is simple at levels -O, -Os, and	 stc  at  levels  -O2,
	   -O3.

       -freorder-blocks-and-partition
	   In addition to reordering basic blocks in the compiled function, in
	   order  to  reduce number of taken branches, partitions hot and cold
	   basic blocks	into separate sections of the assembly and  .o	files,
	   to improve paging and cache locality	performance.

	   This	 optimization  is  automatically turned	off in the presence of
	   exception   handling	  or   unwind	tables	 (on   targets	 using
	   setjump/longjump or target specific scheme),	for linkonce sections,
	   for	functions  with	 a  user-defined  section attribute and	on any
	   architecture	 that  does  not   support   named   sections.	  When
	   -fsplit-stack  is  used  this  option is not	enabled	by default (to
	   avoid linker	errors), but may be enabled  explicitly	 (if  using  a
	   working linker).

	   Enabled for x86 at levels -O2, -O3, -Os.

       -freorder-functions
	   Reorder  functions  in  the	object	file  in order to improve code
	   locality.   This  is	 implemented  by  using	 special   subsections
	   ".text.hot"	  for	most   frequently   executed   functions   and
	   ".text.unlikely" for	unlikely executed  functions.	Reordering  is
	   done	 by  the  linker  so  object  file  format  must support named
	   sections and	linker must place them in a reasonable way.

	   This	option isn't  effective	 unless	 you  either  provide  profile
	   feedback  (see  -fprofile-arcs  for	details)  or manually annotate
	   functions with "hot"	or "cold" attributes.

	   Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
	   Allow  the  compiler	 to  assume  the  strictest   aliasing	 rules
	   applicable  to  the language	being compiled.	 For C (and C++), this
	   activates optimizations based  on  the  type	 of  expressions.   In
	   particular, an object of one	type is	assumed	never to reside	at the
	   same	address	as an object of	a different type, unless the types are
	   almost  the	same.	For  example,  an  "unsigned int" can alias an
	   "int", but not a "void*" or a "double".  A character	type may alias
	   any other type.

	   Pay special attention to code like this:

		   union a_union {
		     int i;
		     double d;
		   };

		   int f() {
		     union a_union t;
		     t.d = 3.0;
		     return t.i;
		   }

	   The practice	of reading from	a different union member than the  one
	   most	 recently  written to (called "type-punning") is common.  Even
	   with	 -fstrict-aliasing,  type-punning  is  allowed,	 provided  the
	   memory  is  accessed	 through  the  union type.  So,	the code above
	   works as expected.	 However, this code might not:

		   int f() {
		     union a_union t;
		     int* ip;
		     t.d = 3.0;
		     ip	= &t.i;
		     return *ip;
		   }

	   Similarly, access by	taking	the  address,  casting	the  resulting
	   pointer  and	 dereferencing the result has undefined	behavior, even
	   if the cast uses a union type, e.g.:

		   int f() {
		     double d =	3.0;
		     return ((union a_union *) &d)->i;
		   }

	   The -fstrict-aliasing option	is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
       -falign-functions=n:m
       -falign-functions=n:m:n2
       -falign-functions=n:m:n2:m2
	   Align the start of functions	to the next power-of-two greater  than
	   or  equal  to  n,  skipping	up to m-1 bytes.  This ensures that at
	   least the first m bytes of the function can be fetched by  the  CPU
	   without crossing an n-byte alignment	boundary.

	   If m	is not specified, it defaults to n.

	   Examples: -falign-functions=32 aligns functions to the next 32-byte
	   boundary,  -falign-functions=24 aligns to the next 32-byte boundary
	   only	 if  this  can	be  done  by  skipping	23  bytes   or	 less,
	   -falign-functions=32:7  aligns to the next 32-byte boundary only if
	   this	can be done by skipping	6 bytes	or less.

	   The second pair of n2:m2 values allows you to specify  a  secondary
	   alignment:  -falign-functions=64:7:32:3  aligns to the next 64-byte
	   boundary if this can	be done	by skipping 6 bytes or less, otherwise
	   aligns to the next 32-byte boundary if this can be done by skipping
	   2 bytes or less.  If	m2 is not specified, it	defaults to n2.

	   Some	assemblers only	support	this flag when n is a power of two; in
	   that	case, it is rounded up.

	   -fno-align-functions	and  -falign-functions=1  are  equivalent  and
	   mean	that functions are not aligned.

	   If  n is not	specified or is	zero, use a machine-dependent default.
	   The maximum allowed n option	value is 65536.

	   Enabled at levels -O2, -O3.

       -flimit-function-alignment
	   If  this  option  is	 enabled,  the	 compiler   tries   to	 avoid
	   unnecessarily  overaligning	functions. It attempts to instruct the
	   assembler to	align by the amount  specified	by  -falign-functions,
	   but not to skip more	bytes than the size of the function.

       -falign-labels
       -falign-labels=n
       -falign-labels=n:m
       -falign-labels=n:m:n2
       -falign-labels=n:m:n2:m2
	   Align all branch targets to a power-of-two boundary.

	   Parameters  of  this	 option	are analogous to the -falign-functions
	   option.  -fno-align-labels and -falign-labels=1 are equivalent  and
	   mean	that labels are	not aligned.

	   If  -falign-loops  or  -falign-jumps	are applicable and are greater
	   than	this value, then their values are used instead.

	   If n	is not specified or is zero, use a  machine-dependent  default
	   which  is  very  likely to be 1, meaning no alignment.  The maximum
	   allowed n option value is 65536.

	   Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
       -falign-loops=n:m
       -falign-loops=n:m:n2
       -falign-loops=n:m:n2:m2
	   Align loops to a power-of-two boundary.  If the loops are  executed
	   many	 times,	 this  makes up	for any	execution of the dummy padding
	   instructions.

	   If -falign-labels is	greater	than this value,  then	its  value  is
	   used	instead.

	   Parameters  of  this	 option	are analogous to the -falign-functions
	   option.  -fno-align-loops and -falign-loops=1  are  equivalent  and
	   mean	 that  loops  are  not	aligned.  The maximum allowed n	option
	   value is 65536.

	   If n	is not specified or is zero, use a machine-dependent default.

	   Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
       -falign-jumps=n:m
       -falign-jumps=n:m:n2
       -falign-jumps=n:m:n2:m2
	   Align branch	targets	to a power-of-two boundary, for	branch targets
	   where the targets can only be reached by jumping.  In this case, no
	   dummy operations need be executed.

	   If -falign-labels is	greater	than this value,  then	its  value  is
	   used	instead.

	   Parameters  of  this	 option	are analogous to the -falign-functions
	   option.  -fno-align-jumps and -falign-jumps=1  are  equivalent  and
	   mean	that loops are not aligned.

	   If  n is not	specified or is	zero, use a machine-dependent default.
	   The maximum allowed n option	value is 65536.

	   Enabled at levels -O2, -O3.

       -fno-allocation-dce
	   Do not remove unused	C++ allocations	in dead	code elimination.

       -fallow-store-data-races
	   Allow the compiler to perform optimizations that may	introduce  new
	   data	 races	on stores, without proving that	the variable cannot be
	   concurrently	 accessed  by  other   threads.	   Does	  not	affect
	   optimization	of local data.	It is safe to use this option if it is
	   known that global data will not be accessed by multiple threads.

	   Examples   of  optimizations	 enabled  by  -fallow-store-data-races
	   include hoisting or if-conversions that may cause a value that  was
	   already  in memory to be re-written with that same value.  Such re-
	   writing is safe in a	single threaded	context	but may	be unsafe in a
	   multi-threaded  context.   Note  that  on  some   processors,   if-
	   conversions may be required in order	to enable vectorization.

	   Enabled at level -Ofast.

       -funit-at-a-time
	   This	option is left for compatibility reasons. -funit-at-a-time has
	   no  effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
	   and -fno-section-anchors.

	   Enabled by default.

       -fno-toplevel-reorder
	   Do  not  reorder  top-level	 functions,   variables,   and	 "asm"
	   statements.	 Output	them in	the same order that they appear	in the
	   input  file.	  When	this  option  is  used,	 unreferenced	static
	   variables  are  not	removed.   This	 option	is intended to support
	   existing code that relies on	a particular ordering.	For new	 code,
	   it is better	to use attributes when possible.

	   -ftoplevel-reorder  is  the	default	at -O1 and higher, and also at
	   -O0 if -fsection-anchors  is	 explicitly  requested.	  Additionally
	   -fno-toplevel-reorder implies -fno-section-anchors.

       -fweb
	   Constructs  webs  as	commonly used for register allocation purposes
	   and assign each web individual pseudo register.   This  allows  the
	   register  allocation	 pass to operate on pseudos directly, but also
	   strengthens several other optimization passes, such	as  CSE,  loop
	   optimizer  and  trivial  dead  code remover.	 It can, however, make
	   debugging impossible, since variables no longer  stay  in  a	 "home
	   register".

	   Enabled by default with -funroll-loops.

       -fwhole-program
	   Assume  that	 the  current  compilation  unit  represents the whole
	   program being compiled.  All	public functions  and  variables  with
	   the	 exception   of	  "main"   and	 those	 merged	 by  attribute
	   "externally_visible"	become static  functions  and  in  effect  are
	   optimized more aggressively by interprocedural optimizers.

	   This	 option	should not be used in combination with -flto.  Instead
	   relying on a	linker plugin should provide safer  and	 more  precise
	   information.

       -flto[=n]
	   This	 option	 runs  the standard link-time optimizer.  When invoked
	   with	source code,  it  generates  GIMPLE  (one  of  GCC's  internal
	   representations)  and  writes  it  to  special  ELF sections	in the
	   object file.	 When the object files are linked  together,  all  the
	   function  bodies  are read from these ELF sections and instantiated
	   as if they had been part of the same	translation unit.

	   To use the link-time	 optimizer,  -flto  and	 optimization  options
	   should  be specified	at compile time	and during the final link.  It
	   is recommended that you compile all the files participating in  the
	   same	 link  with the	same options and also specify those options at
	   link	time.  For example:

		   gcc -c -O2 -flto foo.c
		   gcc -c -O2 -flto bar.c
		   gcc -o myprog -flto -O2 foo.o bar.o

	   The first two invocations to	GCC save a bytecode representation  of
	   GIMPLE into special ELF sections inside foo.o and bar.o.  The final
	   invocation  reads  the GIMPLE bytecode from foo.o and bar.o,	merges
	   the two files into a	single internal	image, and compiles the	result
	   as usual.  Since both foo.o and bar.o  are  merged  into  a	single
	   image,   this   causes   all	  the	interprocedural	 analyses  and
	   optimizations in GCC	to work	across the two files as	if they	were a
	   single one.	This means, for	example, that the inliner is  able  to
	   inline functions in bar.o into functions in foo.o and vice-versa.

	   Another (simpler) way to enable link-time optimization is:

		   gcc -o myprog -flto -O2 foo.c bar.c

	   The	above  generates  bytecode  for	 foo.c	and bar.c, merges them
	   together into a single GIMPLE representation	and optimizes them  as
	   usual to produce myprog.

	   The	important  thing  to  keep in mind is that to enable link-time
	   optimizations you need to use the GCC driver	to  perform  the  link
	   step.   GCC automatically performs link-time	optimization if	any of
	   the objects involved	were  compiled	with  the  -flto  command-line
	   option.  You	can always override the	automatic decision to do link-
	   time	optimization by	passing	-fno-lto to the	link command.

	   To  make  whole  program optimization effective, it is necessary to
	   make	certain	whole program assumptions.  The	compiler needs to know
	   what	functions and variables	 can  be  accessed  by	libraries  and
	   runtime outside of the link-time optimized unit.  When supported by
	   the	linker,	 the  linker  plugin  (see -fuse-linker-plugin)	passes
	   information to the  compiler	 about	used  and  externally  visible
	   symbols.   When the linker plugin is	not available, -fwhole-program
	   should be used to allow the compiler	 to  make  these  assumptions,
	   which leads to more aggressive optimization decisions.

	   When	a file is compiled with	-flto without -fuse-linker-plugin, the
	   generated  object file is larger than a regular object file because
	   it  contains	 GIMPLE	 bytecodes  and	 the  usual  final  code  (see
	   -ffat-lto-objects).	  This	 means	that  object  files  with  LTO
	   information can be linked as	normal object files;  if  -fno-lto  is
	   passed to the linker, no interprocedural optimizations are applied.
	   Note	that when -fno-fat-lto-objects is enabled the compile stage is
	   faster but you cannot perform a regular, non-LTO link on them.

	   When	 producing  the	 final	binary,	 GCC  only  applies  link-time
	   optimizations to those files	that contain bytecode.	Therefore, you
	   can mix and match object files and libraries	with GIMPLE  bytecodes
	   and	final  object  code.  GCC automatically	selects	which files to
	   optimize in LTO mode	 and  which  files  to	link  without  further
	   processing.

	   Generally,  options specified at link time override those specified
	   at compile time, although in	some cases GCC attempts	to infer link-
	   time	options	from the settings used to compile the input files.

	   If you do not specify an optimization level option -O at link time,
	   then	GCC uses the highest optimization level	 used  when  compiling
	   the object files.  Note that	it is generally	ineffective to specify
	   an  optimization  level option only at link time and	not at compile
	   time, for  two  reasons.   First,  compiling	 without  optimization
	   suppresses  compiler	 passes	 that  gather  information  needed for
	   effective  optimization  at	link   time.	Second,	  some	 early
	   optimization	 passes	 can be	performed only at compile time and not
	   at link time.

	   There  are  some  code  generation  flags  preserved	 by  GCC  when
	   generating  bytecodes,  as  they  need  to be used during the final
	   link.  Currently, the following  options  and  their	 settings  are
	   taken  from	the  first object file that explicitly specifies them:
	   -fcommon, -fexceptions, -fnon-call-exceptions, -fgnu-tm and all the
	   -m target flags.

	   The following options -fPIC,	-fpic, -fpie and  -fPIE	 are  combined
	   based on the	following scheme:

		   B<-fPIC> + B<-fpic> = B<-fpic>
		   B<-fPIC> + B<-fno-pic> = B<-fno-pic>
		   B<-fpic/-fPIC> + (no	option)	= (no option)
		   B<-fPIC> + B<-fPIE> = B<-fPIE>
		   B<-fpic> + B<-fPIE> = B<-fpie>
		   B<-fPIC/-fpic> + B<-fpie> = B<-fpie>

	   Certain ABI-changing	flags are required to match in all compilation
	   units,  and trying to override this at link time with a conflicting
	   value   is	ignored.     This    includes	 options    such    as
	   -freg-struct-return and -fpcc-struct-return.

	   Other options such as -ffp-contract,	-fno-strict-overflow, -fwrapv,
	   -fno-trapv  or  -fno-strict-aliasing	are passed through to the link
	   stage and merged conservatively for conflicting translation	units.
	   Specifically	 -fno-strict-overflow,	-fwrapv	 and  -fno-trapv  take
	   precedence; and for example -ffp-contract=off takes precedence over
	   -ffp-contract=fast.	You can	override them at link time.

	   Diagnostic options such as -Wstringop-overflow are  passed  through
	   to  the  link  stage	and their setting matches that of the compile-
	   step	at function granularity.  Note	that  this  matters  only  for
	   diagnostics emitted during optimization.  Note that code transforms
	   such	as inlining can	lead to	warnings being enabled or disabled for
	   regions if code not consistent with the setting at compile time.

	   When	 you  need  to	pass  options  to  the	assembler  via	-Wa or
	   -Xassembler make sure to either compile such	translation units with
	   -fno-lto or consistently use	the  same  assembler  options  on  all
	   translation	units.	 You  can alternatively	also specify assembler
	   options at LTO link time.

	   To enable debug info	generation you need to supply  -g  at  compile
	   time.  If any of the	input files at link time were built with debug
	   info	 generation enabled the	link will enable debug info generation
	   as well.  Any elaborate debug info settings like  the  dwarf	 level
	   -gdwarf-5 need to be	explicitly repeated at the linker command line
	   and	mixing	different  settings  in	different translation units is
	   discouraged.

	   If LTO encounters objects with C linkage declared with incompatible
	   types  in  separate	translation  units  to	be   linked   together
	   (undefined  behavior	 according  to	ISO  C99  6.2.7),  a non-fatal
	   diagnostic may be issued.  The behavior is still undefined  at  run
	   time.  Similar diagnostics may be raised for	other languages.

	   Another   feature   of   LTO	 is  that  it  is  possible  to	 apply
	   interprocedural  optimizations  on  files  written	in   different
	   languages:

		   gcc -c -flto	foo.c
		   g++ -c -flto	bar.cc
		   gfortran -c -flto baz.f90
		   g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

	   Notice  that	the final link is done with g++	to get the C++ runtime
	   libraries and -lgfortran  is	 added	to  get	 the  Fortran  runtime
	   libraries.	In  general,  when  mixing  languages in LTO mode, you
	   should use the same link command options as when  mixing  languages
	   in a	regular	(non-LTO) compilation.

	   If  object files containing GIMPLE bytecode are stored in a library
	   archive, say	libfoo.a, it is	possible to extract and	use them in an
	   LTO link if you are using a linker with plugin support.  To	create
	   static  libraries  suitable	for  LTO,  use	gcc-ar	and gcc-ranlib
	   instead of ar and ranlib; to	show the symbols of object files  with
	   GIMPLE  bytecode,  use  gcc-nm.   Those  commands  require that ar,
	   ranlib and nm have been compiled  with  plugin  support.   At  link
	   time,  use  the flag	-fuse-linker-plugin to ensure that the library
	   participates	in the LTO optimization	process:

		   gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

	   With	the linker plugin enabled,  the	 linker	 extracts  the	needed
	   GIMPLE files	from libfoo.a and passes them on to the	running	GCC to
	   make	them part of the aggregated GIMPLE image to be optimized.

	   If  you  are	 not  using a linker with plugin support and/or	do not
	   enable the linker plugin, then  the	objects	 inside	 libfoo.a  are
	   extracted  and  linked as usual, but	they do	not participate	in the
	   LTO optimization process.   In  order  to  make  a  static  library
	   suitable  for  both LTO optimization	and usual linkage, compile its
	   object files	with -flto -ffat-lto-objects.

	   Link-time optimizations do not require the presence	of  the	 whole
	   program to operate.	If the program does not	require	any symbols to
	   be exported,	it is possible to combine -flto	and -fwhole-program to
	   allow   the	interprocedural	 optimizers  to	 use  more  aggressive
	   assumptions which may lead to improved optimization	opportunities.
	   Use	of  -fwhole-program is not needed when linker plugin is	active
	   (see	-fuse-linker-plugin).

	   The current implementation of LTO  makes  no	 attempt  to  generate
	   bytecode  that  is  portable	between	different types	of hosts.  The
	   bytecode files are versioned	and there is a strict  version	check,
	   so  bytecode	files generated	in one version of GCC do not work with
	   an older or newer version of	GCC.

	   Link-time optimization  does	 not  work  well  with	generation  of
	   debugging   information   on	 systems  other	 than  those  using  a
	   combination of ELF and DWARF.

	   If you specify the optional n, the optimization and code generation
	   done	at link	time is	executed in parallel using n parallel jobs  by
	   utilizing an	installed make program.	 The environment variable MAKE
	   may be used to override the program used.

	   You	can  also specify -flto=jobserver to use GNU make's job	server
	   mode	to determine the number	of parallel jobs. This is useful  when
	   the	Makefile  calling  GCC	is already executing in	parallel.  You
	   must	prepend	a + to the command recipe in the parent	 Makefile  for
	   this	 to  work.  This option	likely only works if MAKE is GNU make.
	   Even	without	the option value, GCC tries to automatically detect  a
	   running GNU make's job server.

	   Use	-flto=auto  to	use  GNU  make's  job server, if available, or
	   otherwise fall back to autodetection	of the number of  CPU  threads
	   present in your system.

       -flto-partition=alg
	   Specify the partitioning algorithm used by the link-time optimizer.
	   The	value  is  either 1to1 to specify a partitioning mirroring the
	   original source files or  balanced  to  specify  partitioning  into
	   equally  sized  chunks  (whenever  possible)	 or  max to create new
	   partition for every symbol where possible.  Specifying none	as  an
	   algorithm  disables	partitioning  and  streaming  completely.  The
	   default value is balanced. While 1to1 can be	used as	an  workaround
	   for	various	code ordering issues, the max partitioning is intended
	   for internal	testing	only.  The value one  specifies	 that  exactly
	   one	partition  should  be  used  while  the	 value	none  bypasses
	   partitioning	and executes the link-time optimization	step  directly
	   from	the WPA	phase.

       -flto-compression-level=n
	   This	  option   specifies   the   level  of	compression  used  for
	   intermediate	language written to LTO	 object	 files,	 and  is  only
	   meaningful  in  conjunction	with  LTO mode (-flto).	 GCC currently
	   supports two	LTO compression	algorithms. For	zstd, valid values are
	   0 (no compression) to 19 (maximum compression), while zlib supports
	   values from 0 to 9.	Values	outside	 this  range  are  clamped  to
	   either  minimum  or maximum of the supported	values.	 If the	option
	   is not given, a default balanced compression	setting	is used.

       -fuse-linker-plugin
	   Enables the use of a	linker plugin during  link-time	 optimization.
	   This	 option	 relies	 on  plugin  support  in  the linker, which is
	   available in	gold or	in GNU ld 2.21 or newer.

	   This	option enables the extraction  of  object  files  with	GIMPLE
	   bytecode  out  of  library  archives.  This improves	the quality of
	   optimization	by exposing more  code	to  the	 link-time  optimizer.
	   This	 information specifies what symbols can	be accessed externally
	   (by non-LTO object or  during  dynamic  linking).   Resulting  code
	   quality  improvements  on  binaries	(and shared libraries that use
	   hidden visibility) are similar to -fwhole-program.  See -flto for a
	   description of the effect of	this flag and how to use it.

	   This	option is enabled by  default  when  LTO  support  in  GCC  is
	   enabled  and	 GCC  was  configured for use with a linker supporting
	   plugins (GNU	ld 2.21	or newer or gold).

       -ffat-lto-objects
	   Fat LTO objects are object files that contain both the intermediate
	   language and	the object code. This makes them usable	for  both  LTO
	   linking  and	 normal	 linking.  This	 option	is effective only when
	   compiling with -flto	and is ignored at link time.

	   -fno-fat-lto-objects	improves compilation time over plain LTO,  but
	   requires  the  complete toolchain to	be aware of LTO. It requires a
	   linker  with	 linker	 plugin	 support  for	basic	functionality.
	   Additionally,  nm,  ar and ranlib need to support linker plugins to
	   allow a full-featured build environment (capable of building	static
	   libraries  etc).   GCC  provides  the  gcc-ar,  gcc-nm,  gcc-ranlib
	   wrappers to pass the	right options to these tools. With non fat LTO
	   makefiles need to be	modified to use	them.

	   Note	 that  modern  binutils	 provide  plugin  auto-load mechanism.
	   Installing the linker plugin	into $libdir/bfd-plugins has the  same
	   effect  as  usage  of the command wrappers (gcc-ar, gcc-nm and gcc-
	   ranlib).

	   The default is -fno-fat-lto-objects on targets with	linker	plugin
	   support.

       -fcompare-elim
	   After  register allocation and post-register	allocation instruction
	   splitting, identify arithmetic instructions that compute  processor
	   flags  similar  to a	comparison operation based on that arithmetic.
	   If possible,	eliminate the explicit comparison operation.

	   This	pass only applies to certain targets  that  cannot  explicitly
	   represent  the  comparison  operation before	register allocation is
	   complete.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fcprop-registers
	   After register allocation and post-register allocation  instruction
	   splitting,  perform	a  copy-propagation  pass  to  try  to	reduce
	   scheduling dependencies and occasionally eliminate the copy.

	   Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
	   Profiles collected using an instrumented binary for	multi-threaded
	   programs  may  be  inconsistent due to missed counter updates. When
	   this	option is specified, GCC uses heuristics to correct or	smooth
	   out	such  inconsistencies.	By default, GCC	emits an error message
	   when	an inconsistent	profile	is detected.

	   This	option is enabled by -fauto-profile.

       -fprofile-partial-training
	   With	"-fprofile-use"	all portions of	programs not  executed	during
	   train run are optimized agressively for size	rather than speed.  In
	   some	 cases	it is not practical to train all possible hot paths in
	   the program.	(For example, program may contain  functions  specific
	   for	a  given  hardware  and	 trianing  may	not cover all hardware
	   configurations      program	    is	    run	      on.)	  With
	   "-fprofile-partial-training"	 profile  feedback will	be ignored for
	   all functions not executed during the train run leading them	to  be
	   optimized  as  if they were compiled	without	profile	feedback. This
	   leads to better performance when train run  is  not	representative
	   but also leads to significantly bigger code.

       -fprofile-use
       -fprofile-use=path
	   Enable  profile  feedback-directed optimizations, and the following
	   optimizations, many of which	are  generally	profitable  only  with
	   profile feedback available:

	   -fbranch-probabilities	 -fprofile-values	-funroll-loops
	   -fpeel-loops	   -ftracer    -fvpt   -finline-functions     -fipa-cp
	   -fipa-cp-clone   -fipa-bit-cp -fpredictive-commoning	 -fsplit-loops
	   -funswitch-loops	-fgcse-after-reload	 -ftree-loop-vectorize
	   -ftree-slp-vectorize			     -fvect-cost-model=dynamic
	   -ftree-loop-distribute-patterns -fprofile-reorder-functions

	   Before you can use this option, you must first  generate  profiling
	   information.

	   By  default,	GCC emits an error message if the feedback profiles do
	   not match the source	code.  This error can be turned	into a warning
	   by using -Wno-error=coverage-mismatch.  Note	 this  may  result  in
	   poorly  optimized code.  Additionally, by default, GCC also emits a
	   warning  message  if	 the  feedback	profiles  do  not  exist  (see
	   -Wmissing-profile).

	   If  path  is	 specified,  GCC looks at the path to find the profile
	   feedback data files.	See -fprofile-dir.

       -fauto-profile
       -fauto-profile=path
	   Enable  sampling-based  feedback-directed  optimizations,  and  the
	   following  optimizations,  many  of	which are generally profitable
	   only	with profile feedback available:

	   -fbranch-probabilities	 -fprofile-values	-funroll-loops
	   -fpeel-loops	    -ftracer	-fvpt	-finline-functions    -fipa-cp
	   -fipa-cp-clone  -fipa-bit-cp	-fpredictive-commoning	 -fsplit-loops
	   -funswitch-loops	-fgcse-after-reload	 -ftree-loop-vectorize
	   -ftree-slp-vectorize			     -fvect-cost-model=dynamic
	   -ftree-loop-distribute-patterns -fprofile-correction

	   path	 is the	name of	a file containing AutoFDO profile information.
	   If omitted, it defaults to fbdata.afdo in the current directory.

	   Producing an	 AutoFDO  profile  data	 file  requires	 running  your
	   program  with  the  perf  utility  on  a supported GNU/Linux	target
	   system.  For	more information, see <https://perf.wiki.kernel.org/>.

	   E.g.

		   perf	record -e br_inst_retired:near_taken -b	-o perf.data \
		       -- your_program

	   Then	use the	create_gcov tool to convert the	raw profile data to  a
	   format  that	 can  be  used	by  GCC.   You	must  also  supply the
	   unstripped  binary  for   your   program   to   this	  tool.	   See
	   <https://github.com/google/autofdo>.

	   E.g.

		   create_gcov --binary=your_program.unstripped	--profile=perf.data \
		       --gcov=profile.afdo

       The  following  options	control	 compiler behavior regarding floating-
       point  arithmetic.   These  options  trade  off	 between   speed   and
       correctness.  All must be specifically enabled.

       -ffloat-store
	   Do  not  store  floating-point  variables in	registers, and inhibit
	   other options that might change whether a floating-point  value  is
	   taken from a	register or memory.

	   This	 option	prevents undesirable excess precision on machines such
	   as the 68000	where the floating registers (of the 68881) keep  more
	   precision  than  a "double" is supposed to have.  Similarly for the
	   x86 architecture.  For most programs,  the  excess  precision  does
	   only	 good,	but  a	few programs rely on the precise definition of
	   IEEE	floating point.	 Use -ffloat-store for	such  programs,	 after
	   modifying  them  to	store  all pertinent intermediate computations
	   into	variables.

       -fexcess-precision=style
	   This	 option	 allows	 further  control  over	 excess	 precision  on
	   machines  where  floating-point  operations	occur in a format with
	   more	precision or range than	 the  IEEE  standard  and  interchange
	   floating-point  types.   By	default, -fexcess-precision=fast is in
	   effect; this	means that operations may be carried out  in  a	 wider
	   precision  than  the	 types	specified  in the source if that would
	   result in faster code, and it is unpredictable when rounding	to the
	   types specified in the source code takes place.  When compiling  C,
	   if  -fexcess-precision=standard  is specified then excess precision
	   follows the rules specified in ISO C99; in particular,  both	 casts
	   and	assignments cause values to be rounded to their	semantic types
	   (whereas -ffloat-store only affects assignments).  This  option  is
	   enabled  by	default	 for  C	if a strict conformance	option such as
	   -std=c99 is used.  -ffast-math enables  -fexcess-precision=fast  by
	   default regardless of whether a strict conformance option is	used.

	   -fexcess-precision=standard	is not implemented for languages other
	   than	 C.   On  the  x86,  it	 has  no  effect  if  -mfpmath=sse  or
	   -mfpmath=sse+387  is	 specified; in the former case,	IEEE semantics
	   apply without excess	precision, and	in  the	 latter,  rounding  is
	   unpredictable.

       -ffast-math
	   Sets	  the  options	-fno-math-errno,  -funsafe-math-optimizations,
	   -ffinite-math-only,	  -fno-rounding-math,	  -fno-signaling-nans,
	   -fcx-limited-range and -fexcess-precision=fast.

	   This	 option	 causes	 the  preprocessor macro "__FAST_MATH__" to be
	   defined.

	   This	option is not turned on	by any -O option besides -Ofast	 since
	   it  can  result  in incorrect output	for programs that depend on an
	   exact implementation	of IEEE	or ISO rules/specifications  for  math
	   functions.  It may, however,	yield faster code for programs that do
	   not require the guarantees of these specifications.

       -fno-math-errno
	   Do not set "errno" after calling math functions that	 are  executed
	   with	 a single instruction, e.g., "sqrt".  A	program	that relies on
	   IEEE	exceptions for math error handling may want to use  this  flag
	   for speed while maintaining IEEE arithmetic compatibility.

	   This	 option	 is not	turned on by any -O option since it can	result
	   in  incorrect  output  for  programs	 that  depend  on   an	 exact
	   implementation   of	IEEE  or  ISO  rules/specifications  for  math
	   functions. It may, however, yield faster code for programs that  do
	   not require the guarantees of these specifications.

	   The default is -fmath-errno.

	   On  Darwin  systems,	the math library never sets "errno".  There is
	   therefore no	reason for the compiler	to  consider  the  possibility
	   that	it might, and -fno-math-errno is the default.

       -funsafe-math-optimizations
	   Allow  optimizations	 for floating-point arithmetic that (a)	assume
	   that	arguments and results are valid	and (b)	may  violate  IEEE  or
	   ANSI	 standards.   When used	at link	time, it may include libraries
	   or startup files that change	the default FPU	control	word or	 other
	   similar optimizations.

	   This	 option	 is not	turned on by any -O option since it can	result
	   in  incorrect  output  for  programs	 that  depend  on   an	 exact
	   implementation   of	IEEE  or  ISO  rules/specifications  for  math
	   functions. It may, however, yield faster code for programs that  do
	   not	require	 the  guarantees  of  these  specifications.   Enables
	   -fno-signed-zeros,	-fno-trapping-math,   -fassociative-math   and
	   -freciprocal-math.

	   The default is -fno-unsafe-math-optimizations.

       -fassociative-math
	   Allow  re-association  of  operands	in  series  of	floating-point
	   operations.	This violates the ISO C	and C++	language  standard  by
	   possibly changing computation result.  NOTE:	re-ordering may	change
	   the	sign  of  zero	as  well  as ignore NaNs and inhibit or	create
	   underflow or	overflow (and thus cannot be used on code that	relies
	   on  rounding	behavior like "(x + 2**52) - 2**52".  May also reorder
	   floating-point comparisons and thus may not be  used	 when  ordered
	   comparisons	 are   required.    This  option  requires  that  both
	   -fno-signed-zeros and -fno-trapping-math be in  effect.   Moreover,
	   it  doesn't	make  much sense with -frounding-math. For Fortran the
	   option is automatically enabled  when  both	-fno-signed-zeros  and
	   -fno-trapping-math are in effect.

	   The default is -fno-associative-math.

       -freciprocal-math
	   Allow  the  reciprocal of a value to	be used	instead	of dividing by
	   the value if	this enables optimizations.  For example "x /  y"  can
	   be replaced with "x * (1/y)", which is useful if "(1/y)" is subject
	   to	common	 subexpression	elimination.   Note  that  this	 loses
	   precision and increases the number of flops operating on the	value.

	   The default is -fno-reciprocal-math.

       -ffinite-math-only
	   Allow optimizations for floating-point arithmetic that assume  that
	   arguments and results are not NaNs or +-Infs.

	   This	 option	 is not	turned on by any -O option since it can	result
	   in  incorrect  output  for  programs	 that  depend  on   an	 exact
	   implementation   of	IEEE  or  ISO  rules/specifications  for  math
	   functions. It may, however, yield faster code for programs that  do
	   not require the guarantees of these specifications.

	   The default is -fno-finite-math-only.

       -fno-signed-zeros
	   Allow  optimizations	 for floating-point arithmetic that ignore the
	   signedness of zero.	IEEE  arithmetic  specifies  the  behavior  of
	   distinct  +0.0 and -0.0 values, which then prohibits	simplification
	   of	expressions   such   as	  x+0.0	  or	0.0*x	 (even	  with
	   -ffinite-math-only).	  This	option implies that the	sign of	a zero
	   result isn't	significant.

	   The default is -fsigned-zeros.

       -fno-trapping-math
	   Compile  code  assuming  that  floating-point   operations	cannot
	   generate user-visible traps.	 These traps include division by zero,
	   overflow,  underflow,  inexact  result and invalid operation.  This
	   option requires that	-fno-signaling-nans  be	 in  effect.   Setting
	   this	 option	may allow faster code if one relies on "non-stop" IEEE
	   arithmetic, for example.

	   This	option should never be turned on by any	-O option since	it can
	   result in incorrect output for programs that	 depend	 on  an	 exact
	   implementation   of	IEEE  or  ISO  rules/specifications  for  math
	   functions.

	   The default is -ftrapping-math.

       -frounding-math
	   Disable  transformations  and  optimizations	 that  assume  default
	   floating-point  rounding  behavior.	 This is round-to-zero for all
	   floating point to integer conversions, and round-to-nearest for all
	   other arithmetic truncations.  This option should be	specified  for
	   programs  that change the FP	rounding mode dynamically, or that may
	   be executed with a non-default rounding mode.  This option disables
	   constant folding of	floating-point	expressions  at	 compile  time
	   (which   may	  be   affected	  by  rounding	mode)  and  arithmetic
	   transformations that	are unsafe in the presence  of	sign-dependent
	   rounding modes.

	   The default is -fno-rounding-math.

	   This	 option	 is  experimental  and does not	currently guarantee to
	   disable all GCC optimizations that are affected by  rounding	 mode.
	   Future  versions  of	 GCC may provide finer control of this setting
	   using C99's "FENV_ACCESS" pragma.  This command-line	option will be
	   used	to specify the default state for "FENV_ACCESS".

       -fsignaling-nans
	   Compile code	assuming that IEEE signaling NaNs may  generate	 user-
	   visible  traps  during  floating-point  operations.	 Setting  this
	   option  disables  optimizations  that  may  change  the  number  of
	   exceptions  visible	with  signaling	 NaNs.	 This  option  implies
	   -ftrapping-math.

	   This	option causes the preprocessor macro "__SUPPORT_SNAN__"	to  be
	   defined.

	   The default is -fno-signaling-nans.

	   This	 option	 is  experimental  and does not	currently guarantee to
	   disable all GCC optimizations that affect signaling NaN behavior.

       -fno-fp-int-builtin-inexact
	   Do not allow	the built-in functions "ceil",	"floor",  "round"  and
	   "trunc",  and their "float" and "long double" variants, to generate
	   code	 that  raises  the  "inexact"  floating-point  exception   for
	   noninteger  arguments.   ISO	 C99  and C11 allow these functions to
	   raise the "inexact" exception, but ISO/IEC TS 18661-1:2014,	the  C
	   bindings  to	 IEEE  754-2008,  as integrated	into ISO C2X, does not
	   allow these functions to do so.

	   The default is -ffp-int-builtin-inexact, allowing the exception  to
	   be  raised,	unless	C2X  or	 a later C standard is selected.  This
	   option does nothing unless -ftrapping-math is in effect.

	   Even	if  -fno-fp-int-builtin-inexact	 is  used,  if	the  functions
	   generate  a call to a library function then the "inexact" exception
	   may be raised if the	library	 implementation	 does  not  follow  TS
	   18661.

       -fsingle-precision-constant
	   Treat  floating-point  constants  as	 single	 precision  instead of
	   implicitly converting them to double-precision constants.

       -fcx-limited-range
	   When	enabled, this option states that a range reduction step	is not
	   needed  when	 performing  complex  division.	  Also,	 there	is  no
	   checking whether the	result of a complex multiplication or division
	   is  "NaN  + I*NaN", with an attempt to rescue the situation in that
	   case.  The default is  -fno-cx-limited-range,  but  is  enabled  by
	   -ffast-math.

	   This	  option   controls   the  default  setting  of	 the  ISO  C99
	   "CX_LIMITED_RANGE" pragma.  Nevertheless, the option	applies	to all
	   languages.

       -fcx-fortran-rules
	   Complex multiplication and division follow  Fortran	rules.	 Range
	   reduction  is  done	as  part  of complex division, but there is no
	   checking whether the	result of a complex multiplication or division
	   is "NaN + I*NaN", with an attempt to	rescue the situation  in  that
	   case.

	   The default is -fno-cx-fortran-rules.

       The   following	 options   control   optimizations  that  may  improve
       performance, but	are not	enabled	 by  any  -O  options.	 This  section
       includes	experimental options that may produce broken code.

       -fbranch-probabilities
	   After  running  a  program  compiled	 with  -fprofile-arcs, you can
	   compile it a	second time using -fbranch-probabilities,  to  improve
	   optimizations  based	 on the	number of times	each branch was	taken.
	   When	a program compiled with	-fprofile-arcs	exits,	it  saves  arc
	   execution  counts  to a file	called sourcename.gcda for each	source
	   file.  The information in this data file is very dependent  on  the
	   structure  of  the  generated code, so you must use the same	source
	   code	and the	same optimization options for both compilations.

	   With	-fbranch-probabilities,	GCC puts a REG_BR_PROB	note  on  each
	   JUMP_INSN   and   CALL_INSN.	   These   can	 be  used  to  improve
	   optimization.  Currently, they are  only  used  in  one  place:  in
	   reorg.c,  instead of	guessing which path a branch is	most likely to
	   take, the REG_BR_PROB values	are used to  exactly  determine	 which
	   path	is taken more often.

	   Enabled by -fprofile-use and	-fauto-profile.

       -fprofile-values
	   If  combined	 with  -fprofile-arcs,	it adds	code so	that some data
	   about values	of expressions in the program is gathered.

	   With	-fbranch-probabilities,	it reads back the data	gathered  from
	   profiling values of expressions for usage in	optimizations.

	   Enabled by -fprofile-generate, -fprofile-use, and -fauto-profile.

       -fprofile-reorder-functions
	   Function reordering based on	profile	instrumentation	collects first
	   time	 of  execution	of  a  function	 and orders these functions in
	   ascending order.

	   Enabled with	-fprofile-use.

       -fvpt
	   If combined with -fprofile-arcs, this option	instructs the compiler
	   to add code to gather information about values of expressions.

	   With	-fbranch-probabilities,	it reads back the  data	 gathered  and
	   actually  performs  the optimizations based on them.	 Currently the
	   optimizations include specialization	of division  operations	 using
	   the knowledge about the value of the	denominator.

	   Enabled with	-fprofile-use and -fauto-profile.

       -frename-registers
	   Attempt to avoid false dependencies in scheduled code by making use
	   of	registers   left   over	  after	  register  allocation.	  This
	   optimization	most  benefits	processors  with  lots	of  registers.
	   Depending  on  the  debug information format	adopted	by the target,
	   however, it can  make  debugging  impossible,  since	 variables  no
	   longer stay in a "home register".

	   Enabled by default with -funroll-loops.

       -fschedule-fusion
	   Performs  a	target	dependent  pass	over the instruction stream to
	   schedule instructions of same type together because target  machine
	   can	execute	 them  more  efficiently  if they are adjacent to each
	   other in the	instruction flow.

	   Enabled at levels -O2, -O3, -Os.

       -ftracer
	   Perform  tail  duplication  to  enlarge  superblock	 size.	  This
	   transformation simplifies the control flow of the function allowing
	   other optimizations to do a better job.

	   Enabled by -fprofile-use and	-fauto-profile.

       -funroll-loops
	   Unroll  loops  whose	 number	 of  iterations	 can  be determined at
	   compile time	or upon	entry to  the  loop.   -funroll-loops  implies
	   -frerun-cse-after-loop,  -fweb  and	-frename-registers.   It  also
	   turns on complete loop peeling (i.e.	complete removal of loops with
	   a small constant number of iterations).   This  option  makes  code
	   larger, and may or may not make it run faster.

	   Enabled by -fprofile-use and	-fauto-profile.

       -funroll-all-loops
	   Unroll  all	loops, even if their number of iterations is uncertain
	   when	the loop is entered.  This usually  makes  programs  run  more
	   slowly.    -funroll-all-loops   implies   the   same	  options   as
	   -funroll-loops.

       -fpeel-loops
	   Peels loops for which there is enough information that they do  not
	   roll	 much  (from  profile  feedback	 or static analysis).  It also
	   turns on complete loop peeling (i.e.	complete removal of loops with
	   small constant number of iterations).

	   Enabled by -O3, -fprofile-use, and -fauto-profile.

       -fmove-loop-invariants
	   Enables the loop invariant motion pass in the RTL  loop  optimizer.
	   Enabled at level -O1	and higher, except for -Og.

       -fsplit-loops
	   Split a loop	into two if it contains	a condition that's always true
	   for one side	of the iteration space and false for the other.

	   Enabled by -fprofile-use and	-fauto-profile.

       -funswitch-loops
	   Move	 branches with loop invariant conditions out of	the loop, with
	   duplicates of the loop on  both  branches  (modified	 according  to
	   result of the condition).

	   Enabled by -fprofile-use and	-fauto-profile.

       -fversion-loops-for-strides
	   If  a  loop	iterates  over an array	with a variable	stride,	create
	   another version of the loop that assumes the	stride is always  one.
	   For example:

		   for (int i =	0; i < n; ++i)
		     x[i * stride] = ...;

	   becomes:

		   if (stride == 1)
		     for (int i	= 0; i < n; ++i)
		       x[i] = ...;
		   else
		     for (int i	= 0; i < n; ++i)
		       x[i * stride] = ...;

	   This	 is  particularly  useful  for assumed-shape arrays in Fortran
	   where  (for	example)  it  allows  better  vectorization   assuming
	   contiguous  accesses.   This	flag is	enabled	by default at -O3.  It
	   is also enabled by -fprofile-use and	-fauto-profile.

       -ffunction-sections
       -fdata-sections
	   Place each function or data item into its own section in the	output
	   file	if the target supports arbitrary sections.  The	 name  of  the
	   function or the name	of the data item determines the	section's name
	   in the output file.

	   Use	 these	options	 on  systems  where  the  linker  can  perform
	   optimizations to improve locality of	reference in  the  instruction
	   space.   Most systems using the ELF object format have linkers with
	   such	 optimizations.	  On  AIX,  the	 linker	 rearranges   sections
	   (CSECTs) based on the call graph.  The performance impact varies.

	   Together  with  a  linker  garbage collection (linker --gc-sections
	   option)  these  options  may	 lead  to  smaller   statically-linked
	   executables (after stripping).

	   On ELF/DWARF	systems	these options do not degenerate	the quality of
	   the	debug  information.   There  could be issues with other	object
	   files/debug info formats.

	   Only	use these options when there  are  significant	benefits  from
	   doing so.  When you specify these options, the assembler and	linker
	   create  larger  object  and	executable  files and are also slower.
	   These options affect	code generation.  They	prevent	 optimizations
	   by  the  compiler  and  assembler using relative locations inside a
	   translation unit since the locations	are unknown until  link	 time.
	   An  example of such an optimization is relaxing calls to short call
	   instructions.

       -fstdarg-opt
	   Optimize the	prologue of variadic argument functions	 with  respect
	   to usage of those arguments.

       -fsection-anchors
	   Try	to reduce the number of	symbolic address calculations by using
	   shared  "anchor"  symbols  to   address   nearby   objects.	  This
	   transformation can help to reduce the number	of GOT entries and GOT
	   accesses on some targets.

	   For example,	the implementation of the following function "foo":

		   static int a, b, c;
		   int foo (void) { return a + b + c; }

	   usually calculates the addresses of all three variables, but	if you
	   compile it with -fsection-anchors, it accesses the variables	from a
	   common  anchor  point  instead.   The  effect  is  similar  to  the
	   following pseudocode	(which isn't valid C):

		   int foo (void)
		   {
		     register int *xr =	&x;
		     return xr[&a - &x]	+ xr[&b	- &x] +	xr[&c -	&x];
		   }

	   Not all targets support this	option.

       -fzero-call-used-regs=choice
	   Zero	call-used registers at function	 return	 to  increase  program
	   security  by	 either	 mitigating  Return-Oriented Programming (ROP)
	   attacks or preventing information leakage through registers.

	   The	possible  values  of  choice  are  the	 same	as   for   the
	   "zero_call_used_regs" attribute.  The default is skip.

	   You	can control this behavior for a	specific function by using the
	   function attribute "zero_call_used_regs".

       --param name=value
	   In some places, GCC uses various constants to control the amount of
	   optimization	that is	 done.	 For  example,	GCC  does  not	inline
	   functions  that contain more	than a certain number of instructions.
	   You can control some	of these constants on the command  line	 using
	   the --param option.

	   The	names  of  specific parameters,	and the	meaning	of the values,
	   are tied to the internals of	 the  compiler,	 and  are  subject  to
	   change without notice in future releases.

	   In  order to	get minimal, maximal and default value of a parameter,
	   one can use --help=param -Q options.

	   In each case, the value is an integer.  The	following  choices  of
	   name	are recognized for all targets:

	   predictable-branch-outcome
	       When  branch  is	 predicted  to be taken	with probability lower
	       than this threshold (in percent), then it  is  considered  well
	       predictable.

	   max-rtl-if-conversion-insns
	       RTL if-conversion tries to remove conditional branches around a
	       block	and   replace	them   with   conditionally   executed
	       instructions.  This  parameter  gives  the  maximum  number  of
	       instructions  in	 a  block  which  should be considered for if-
	       conversion.  The	compiler will also  use	 other	heuristics  to
	       decide whether if-conversion is likely to be profitable.

	   max-rtl-if-conversion-predictable-cost
	       RTL  if-conversion  will	 try  to  remove  conditional branches
	       around a	block and replace  them	 with  conditionally  executed
	       instructions.   These  parameters  give the maximum permissible
	       cost for	the sequence that would	be generated by	 if-conversion
	       depending  on whether the branch	is statically determined to be
	       predictable or not.  The	units for this parameter are the  same
	       as  those  for  the GCC internal	seq_cost metric.  The compiler
	       will try	to provide a reasonable	 default  for  this  parameter
	       using the BRANCH_COST target macro.

	   max-crossjump-edges
	       The  maximum  number  of	 incoming edges	to consider for	cross-
	       jumping.	 The algorithm used by -fcrossjumping is O(N^2)	in the
	       number of edges incoming	to each	block.	Increasing values mean
	       more  aggressive	 optimization,	making	the  compilation  time
	       increase	with probably small improvement	in executable size.

	   min-crossjump-insns
	       The  minimum number of instructions that	must be	matched	at the
	       end of two blocks before	cross-jumping is  performed  on	 them.
	       This value is ignored in	the case where all instructions	in the
	       block being cross-jumped	from are matched.

	   max-grow-copy-bb-insns
	       The  maximum  code  size	 expansion  factor  when copying basic
	       blocks instead of jumping.  The expansion is relative to	a jump
	       instruction.

	   max-goto-duplication-insns
	       The maximum number of instructions to duplicate to a block that
	       jumps to	a computed goto.  To avoid O(N^2) behavior in a	number
	       of passes, GCC factors computed gotos early in the  compilation
	       process,	and unfactors them as late as possible.	 Only computed
	       jumps  at the end of a basic blocks with	no more	than max-goto-
	       duplication-insns are unfactored.

	   max-delay-slot-insn-search
	       The maximum number of instructions to consider when looking for
	       an instruction to  fill	a  delay  slot.	  If  more  than  this
	       arbitrary number	of instructions	are searched, the time savings
	       from  filling  the  delay  slot are minimal, so stop searching.
	       Increasing values mean more aggressive optimization, making the
	       compilation time	increase with probably	small  improvement  in
	       execution time.

	   max-delay-slot-live-search
	       When  trying  to	 fill  delay  slots,  the  maximum  number  of
	       instructions to consider	when searching for a block with	 valid
	       live  register information.  Increasing this arbitrarily	chosen
	       value  means  more  aggressive  optimization,  increasing   the
	       compilation  time.   This  parameter should be removed when the
	       delay slot code	is  rewritten  to  maintain  the  control-flow
	       graph.

	   max-gcse-memory
	       The  approximate	 maximum  amount of memory in "kB" that	can be
	       allocated in order to perform the global	 common	 subexpression
	       elimination  optimization.   If	more  memory than specified is
	       required, the optimization is not done.

	   max-gcse-insertion-ratio
	       If the ratio of expression insertions to	 deletions  is	larger
	       than  this  value  for  any expression, then RTL	PRE inserts or
	       removes the expression  and  thus  leaves  partially  redundant
	       computations in the instruction stream.

	   max-pending-list-length
	       The  maximum  number  of	pending	dependencies scheduling	allows
	       before flushing the current state  and  starting	 over.	 Large
	       functions  with	few  branches  or calls	can create excessively
	       large lists which needlessly consume memory and resources.

	   max-modulo-backtrack-attempts
	       The maximum number of backtrack attempts	the  scheduler	should
	       make   when  modulo  scheduling	a  loop.   Larger  values  can
	       exponentially increase compilation time.

	   max-inline-insns-single
	       Several parameters control the tree inliner used	in GCC.	  This
	       number  sets  the  maximum  number  of instructions (counted in
	       GCC's internal representation) in a single  function  that  the
	       tree   inliner  considers  for  inlining.   This	 only  affects
	       functions declared inline and methods implemented  in  a	 class
	       declaration (C++).

	   max-inline-insns-auto
	       When  you  use  -finline-functions  (included in	-O3), a	lot of
	       functions that would otherwise not be considered	 for  inlining
	       by  the	compiler  are  investigated.   To  those  functions, a
	       different  (more	 restrictive)  limit  compared	to   functions
	       declared	inline can be applied (--param max-inline-insns-auto).

	   max-inline-insns-small
	       This  is	 bound	applied	to calls which are considered relevant
	       with -finline-small-functions.

	   max-inline-insns-size
	       This is bound applied to	calls which are	 optimized  for	 size.
	       Small  growth  may  be  desirable  to  anticipate  optimization
	       oppurtunities exposed by	inlining.

	   uninlined-function-insns
	       Number  of  instructions	 accounted  by	inliner	 for  function
	       overhead	such as	function prologue and epilogue.

	   uninlined-function-time
	       Extra  time  accounted by inliner for function overhead such as
	       time needed to execute function prologue	and epilogue

	   inline-heuristics-hint-percent
	       The  scale  (in	percents)  applied   to	  inline-insns-single,
	       inline-insns-single-O2,	   inline-insns-auto	when	inline
	       heuristics hints	that inlining is very profitable (will	enable
	       later optimizations).

	   uninlined-thunk-insns
	   uninlined-thunk-time
	       Same as --param uninlined-function-insns	and --param uninlined-
	       function-time but applied to function thunks

	   inline-min-speedup
	       When  estimated	performance  improvement  of  caller  +	callee
	       runtime exceeds this threshold (in percent), the	 function  can
	       be inlined regardless of	the limit on --param max-inline-insns-
	       single and --param max-inline-insns-auto.

	   large-function-insns
	       The  limit  specifying  really  large functions.	 For functions
	       larger than this	limit after inlining, inlining is  constrained
	       by  --param  large-function-growth.   This  parameter is	useful
	       primarily to avoid extreme  compilation	time  caused  by  non-
	       linear algorithms used by the back end.

	   large-function-growth
	       Specifies  maximal  growth of large function caused by inlining
	       in percents.  For example, parameter  value  100	 limits	 large
	       function	growth to 2.0 times the	original size.

	   large-unit-insns
	       The  limit specifying large translation unit.  Growth caused by
	       inlining	of units larger	than this limit	is limited by  --param
	       inline-unit-growth.   For  small	units this might be too	tight.
	       For example, consider a unit consisting of function A  that  is
	       inline  and  B  that  just  calls A three times.	 If B is small
	       relative	to A, the  growth  of  unit  is	 300\%	and  yet  such
	       inlining	 is  very  sane.   For	very large units consisting of
	       small inlineable	functions, however, the	 overall  unit	growth
	       limit  is  needed  to avoid exponential explosion of code size.
	       Thus for	smaller	units, the size	is increased to	--param	large-
	       unit-insns before applying --param inline-unit-growth.

	   lazy-modules
	       Maximum number of concurrently open C++ module files when  lazy
	       loading.

	   inline-unit-growth
	       Specifies maximal overall growth	of the compilation unit	caused
	       by  inlining.   For  example,  parameter	 value	20 limits unit
	       growth to 1.2 times the original	size. Cold  functions  (either
	       marked  cold  via  an attribute or by profile feedback) are not
	       accounted into the unit size.

	   ipa-cp-unit-growth
	       Specifies maximal overall growth	of the compilation unit	caused
	       by  interprocedural   constant	propagation.	For   example,
	       parameter value 10 limits unit growth to	1.1 times the original
	       size.

	   ipa-cp-large-unit-insns
	       The size	of translation unit that IPA-CP	pass considers large.

	   large-stack-frame
	       The  limit  specifying  large stack frames.  While inlining the
	       algorithm is trying to not grow past this limit too much.

	   large-stack-frame-growth
	       Specifies maximal  growth  of  large  stack  frames  caused  by
	       inlining	in percents.  For example, parameter value 1000	limits
	       large stack frame growth	to 11 times the	original size.

	   max-inline-insns-recursive
	   max-inline-insns-recursive-auto
	       Specifies  the  maximum	number	of instructions	an out-of-line
	       copy of a self-recursive	 inline	 function  can	grow  into  by
	       performing recursive inlining.

	       --param	 max-inline-insns-recursive   applies	to   functions
	       declared	inline.	 For functions not declared inline,  recursive
	       inlining	happens	only when -finline-functions (included in -O3)
	       is  enabled;  --param  max-inline-insns-recursive-auto  applies
	       instead.

	   max-inline-recursive-depth
	   max-inline-recursive-depth-auto
	       Specifies  the  maximum	recursion  depth  used	for  recursive
	       inlining.

	       --param	 max-inline-recursive-depth   applies	to   functions
	       declared	inline.	 For functions not declared inline,  recursive
	       inlining	happens	only when -finline-functions (included in -O3)
	       is  enabled;  --param  max-inline-recursive-depth-auto  applies
	       instead.

	   min-inline-recursive-probability
	       Recursive inlining is profitable	only for function having  deep
	       recursion  in  average  and can hurt for	function having	little
	       recursion depth by increasing the prologue size	or  complexity
	       of function body	to other optimizers.

	       When profile feedback is	available (see -fprofile-generate) the
	       actual recursion	depth can be guessed from the probability that
	       function	 recurses via a	given call expression.	This parameter
	       limits inlining only  to	 call  expressions  whose  probability
	       exceeds the given threshold (in percents).

	   early-inlining-insns
	       Specify	growth	that the early inliner can make.  In effect it
	       increases the amount  of	 inlining  for	code  having  a	 large
	       abstraction penalty.

	   max-early-inliner-iterations
	       Limit  of  iterations  of  the  early  inliner.	This basically
	       bounds the number of nested indirect calls  the	early  inliner
	       can resolve.  Deeper chains are still handled by	late inlining.

	   comdat-sharing-probability
	       Probability  (in	 percent) that C++ inline function with	comdat
	       visibility are shared across multiple compilation units.

	   modref-max-bases
	   modref-max-refs
	   modref-max-accesses
	       Specifies the maximal number of base pointers,  references  and
	       accesses	stored for a single function by	mod/ref	analysis.

	   modref-max-tests
	       Specifies  the  maxmal number of	tests alias oracle can perform
	       to disambiguate memory locations	using the mod/ref information.
	       This parameter ought to be bigger than --param modref-max-bases
	       and --param modref-max-refs.

	   modref-max-depth
	       Specifies the maximum depth of DFS walk used by	modref	escape
	       analysis.  Setting to 0 disables	the analysis completely.

	   modref-max-escape-points
	       Specifies the maximum number of escape points tracked by	modref
	       per SSA-name.

	   profile-func-internal-id
	       A  parameter  to	control	whether	to use function	internal id in
	       profile database	lookup.	If the value is	0, the	compiler  uses
	       an  id  that  is	based on function assembler name and filename,
	       which makes old profile data more tolerant  to  source  changes
	       such as function	reordering etc.

	   min-vect-loop-bound
	       The  minimum  number  of	 iterations  under which loops are not
	       vectorized  when	 -ftree-vectorize  is  used.   The  number  of
	       iterations  after  vectorization	 needs	to be greater than the
	       value specified by this option to allow vectorization.

	   gcse-cost-distance-ratio
	       Scaling factor in calculation of	maximum	distance an expression
	       can  be	moved  by  GCSE	 optimizations.	  This	is   currently
	       supported  only	in  the	 code  hoisting	 pass.	The bigger the
	       ratio,  the  more  aggressive  code  hoisting  is  with	simple
	       expressions,  i.e.,  the	 expressions  that have	cost less than
	       gcse-unrestricted-cost.	 Specifying  0	disables  hoisting  of
	       simple expressions.

	   gcse-unrestricted-cost
	       Cost,  roughly measured as the cost of a	single typical machine
	       instruction, at which GCSE optimizations	do not	constrain  the
	       distance	an expression can travel.  This	is currently supported
	       only  in	the code hoisting pass.	 The lesser the	cost, the more
	       aggressive  code	 hoisting  is.	 Specifying   0	  allows   all
	       expressions to travel unrestricted distances.

	   max-hoist-depth
	       The  depth  of  search in the dominator tree for	expressions to
	       hoist.  This is used to avoid quadratic	behavior  in  hoisting
	       algorithm.   The	 value	of 0 does not limit on the search, but
	       may slow	down compilation of huge functions.

	   max-tail-merge-comparisons
	       The maximum amount of similar bbs to compare a bb  with.	  This
	       is used to avoid	quadratic behavior in tree tail	merging.

	   max-tail-merge-iterations
	       The maximum amount of iterations	of the pass over the function.
	       This is used to limit compilation time in tree tail merging.

	   store-merging-allow-unaligned
	       Allow  the  store merging pass to introduce unaligned stores if
	       it is legal to do so.

	   max-stores-to-merge
	       The maximum number of stores to attempt	to  merge  into	 wider
	       stores in the store merging pass.

	   max-store-chains-to-track
	       The maximum number of store chains to track at the same time in
	       the  attempt  to	 merge	them  into  wider  stores in the store
	       merging pass.

	   max-stores-to-track
	       The maximum number of stores to track at	the same time  in  the
	       attemt  to to merge them	into wider stores in the store merging
	       pass.

	   max-unrolled-insns
	       The maximum number of instructions that a loop may have	to  be
	       unrolled.    If	 a  loop  is  unrolled,	 this  parameter  also
	       determines how many times the loop code is unrolled.

	   max-average-unrolled-insns
	       The maximum number of instructions biased by  probabilities  of
	       their execution that a loop may have to be unrolled.  If	a loop
	       is  unrolled, this parameter also determines how	many times the
	       loop code is unrolled.

	   max-unroll-times
	       The maximum number of unrollings	of a single loop.

	   max-peeled-insns
	       The maximum number of instructions that a loop may have	to  be
	       peeled.	 If  a	loop is	peeled,	this parameter also determines
	       how many	times the loop code is peeled.

	   max-peel-times
	       The maximum number of peelings of a single loop.

	   max-peel-branches
	       The maximum number of branches on  the  hot  path  through  the
	       peeled sequence.

	   max-completely-peeled-insns
	       The maximum number of insns of a	completely peeled loop.

	   max-completely-peel-times
	       The  maximum  number of iterations of a loop to be suitable for
	       complete	peeling.

	   max-completely-peel-loop-nest-depth
	       The maximum depth of a loop nest	suitable for complete peeling.

	   max-unswitch-insns
	       The maximum number of insns of an unswitched loop.

	   max-unswitch-level
	       The maximum number of branches unswitched in a single loop.

	   lim-expensive
	       The minimum  cost  of  an  expensive  expression	 in  the  loop
	       invariant motion.

	   min-loop-cond-split-prob
	       When FDO	profile	information is available, min-loop-cond-split-
	       prob  specifies	minimum	 threshold  for	 probability  of semi-
	       invariant condition statement to	trigger	loop split.

	   iv-consider-all-candidates-bound
	       Bound on	number of candidates for  induction  variables,	 below
	       which  all  candidates are considered for each use in induction
	       variable	optimizations.	If  there  are	more  candidates  than
	       this,  only  the	 most  relevant	 ones  are considered to avoid
	       quadratic time complexity.

	   iv-max-considered-uses
	       The induction variable optimizations  give  up  on  loops  that
	       contain more induction variable uses.

	   iv-always-prune-cand-set-bound
	       If  the	number	of  candidates in the set is smaller than this
	       value, always try to remove unnecessary ivs from	the  set  when
	       adding a	new one.

	   avg-loop-niter
	       Average number of iterations of a loop.

	   dse-max-object-size
	       Maximum	size  (in  bytes)  of objects tracked bytewise by dead
	       store  elimination.   Larger  values  may  result   in	larger
	       compilation times.

	   dse-max-alias-queries-per-store
	       Maximum	number	of  queries  into  the alias oracle per	store.
	       Larger values result in larger compilation times	and may	result
	       in more removed dead stores.

	   scev-max-expr-size
	       Bound on	size of	expressions  used  in  the  scalar  evolutions
	       analyzer.  Large	expressions slow the analyzer.

	   scev-max-expr-complexity
	       Bound  on  the  complexity  of  the  expressions	 in the	scalar
	       evolutions analyzer.  Complex expressions slow the analyzer.

	   max-tree-if-conversion-phi-args
	       Maximum number of arguments in  a  PHI  supported  by  TREE  if
	       conversion unless the loop is marked with simd pragma.

	   vect-max-version-for-alignment-checks
	       The  maximum  number  of	 run-time checks that can be performed
	       when doing loop versioning for alignment	in the vectorizer.

	   vect-max-version-for-alias-checks
	       The maximum number of run-time checks  that  can	 be  performed
	       when doing loop versioning for alias in the vectorizer.

	   vect-max-peeling-for-alignment
	       The  maximum  number  of	loop peels to enhance access alignment
	       for vectorizer. Value -1	means no limit.

	   max-iterations-to-track
	       The maximum number of iterations	 of  a	loop  the  brute-force
	       algorithm  for analysis of the number of	iterations of the loop
	       tries to	evaluate.

	   hot-bb-count-fraction
	       The denominator n of fraction  1/n  of  the  maximal  execution
	       count of	a basic	block in the entire program that a basic block
	       needs  to  at  least  have  in order to be considered hot.  The
	       default is 10000, which means that a basic block	is  considered
	       hot  if	its  execution	count  is  greater than	1/10000	of the
	       maximal execution count.	 0 means that it is  never  considered
	       hot.  Used in non-LTO mode.

	   hot-bb-count-ws-permille
	       The  number of most executed permilles, ranging from 0 to 1000,
	       of the profiled execution of the	entire program	to  which  the
	       execution count of a basic block	must be	part of	in order to be
	       considered  hot.	  The default is 990, which means that a basic
	       block is	considered hot if its execution	count  contributes  to
	       the upper 990 permilles,	or 99.0%, of the profiled execution of
	       the  entire  program.  0	means that it is never considered hot.
	       Used in LTO mode.

	   hot-bb-frequency-fraction
	       The denominator n of fraction 1/n of the	execution frequency of
	       the entry block of a  function  that  a	basic  block  of  this
	       function	 needs to at least have	in order to be considered hot.
	       The default  is	1000,  which  means  that  a  basic  block  is
	       considered  hot in a function if	it is executed more frequently
	       than 1/1000  of	the  frequency	of  the	 entry	block  of  the
	       function.  0 means that it is never considered hot.

	   unlikely-bb-count-fraction
	       The  denominator	 n  of	fraction 1/n of	the number of profiled
	       runs of the entire program below	which the execution count of a
	       basic block must	 be  in	 order	for  the  basic	 block	to  be
	       considered  unlikely  executed.	The default is 20, which means
	       that a basic block is considered	unlikely  executed  if	it  is
	       executed	in fewer than 1/20, or 5%, of the runs of the program.
	       0 means that it is always considered unlikely executed.

	   max-predicted-iterations
	       The  maximum  number  of	loop iterations	we predict statically.
	       This is useful in cases where a function	contains a single loop
	       with known bound	and another  loop  with	 unknown  bound.   The
	       known  number  of  iterations is	predicted correctly, while the
	       unknown number of iterations average to roughly 10.  This means
	       that the	loop without bounds appears artificially cold relative
	       to the other one.

	   builtin-expect-probability
	       Control the probability of the expression having	the  specified
	       value.  This  parameter	takes a	percentage (i.e. 0 ... 100) as
	       input.

	   builtin-string-cmp-inline-length
	       The maximum length of a constant	string for  a  builtin	string
	       cmp call	eligible for inlining.

	   align-threshold
	       Select  fraction	 of  the  maximal frequency of executions of a
	       basic block in a	function to align the basic block.

	   align-loop-iterations
	       A loop expected to iterate at  least  the  selected  number  of
	       iterations is aligned.

	   tracer-dynamic-coverage
	   tracer-dynamic-coverage-feedback
	       This value is used to limit superblock formation	once the given
	       percentage  of  executed	 instructions is covered.  This	limits
	       unnecessary code	size expansion.

	       The tracer-dynamic-coverage-feedback  parameter	is  used  only
	       when  profile  feedback	is  available.	 The real profiles (as
	       opposed to statically estimated ones) are  much	less  balanced
	       allowing	the threshold to be larger value.

	   tracer-max-code-growth
	       Stop  tail  duplication	once  code  growth  has	 reached given
	       percentage.  This is a rather artificial	limit, as most of  the
	       duplicates  are eliminated later	in cross jumping, so it	may be
	       set to much higher values than is the desired code growth.

	   tracer-min-branch-ratio
	       Stop reverse growth when	the reverse probability	of  best  edge
	       is less than this threshold (in percent).

	   tracer-min-branch-probability
	   tracer-min-branch-probability-feedback
	       Stop forward growth if the best edge has	probability lower than
	       this threshold.

	       Similarly   to	tracer-dynamic-coverage	  two  parameters  are
	       provided.  tracer-min-branch-probability-feedback is  used  for
	       compilation   with   profile  feedback  and  tracer-min-branch-
	       probability compilation without.	  The  value  for  compilation
	       with profile feedback needs to be more conservative (higher) in
	       order to	make tracer effective.

	   stack-clash-protection-guard-size
	       Specify	the  size of the operating system provided stack guard
	       as 2 raised to num bytes.  Higher values	may reduce the	number
	       of  explicit  probes,  but  a  value  larger than the operating
	       system provided guard will leave	code vulnerable	to stack clash
	       style attacks.

	   stack-clash-protection-probe-interval
	       Stack clash protection involves probing stack space  as	it  is
	       allocated.   This  param	 controls the maximum distance between
	       probes into the stack as	2 raised to num	bytes.	Higher	values
	       may  reduce  the	 number	of explicit probes, but	a value	larger
	       than the	 operating  system  provided  guard  will  leave  code
	       vulnerable to stack clash style attacks.

	   max-cse-path-length
	       The maximum number of basic blocks on path that CSE considers.

	   max-cse-insns
	       The   maximum  number  of  instructions	CSE  processes	before
	       flushing.

	   ggc-min-expand
	       GCC  uses  a  garbage  collector	 to  manage  its  own	memory
	       allocation.  This parameter specifies the minimum percentage by
	       which  the garbage collector's heap should be allowed to	expand
	       between	collections.   Tuning  this  may  improve  compilation
	       speed; it has no	effect on code generation.

	       The  default  is	 30%  +	70% * (RAM/1GB)	with an	upper bound of
	       100% when RAM >=	1GB.  If "getrlimit" is	available, the	notion
	       of  "RAM"  is  the  smallest of actual RAM and "RLIMIT_DATA" or
	       "RLIMIT_AS".  If	 GCC  is  not  able  to	 calculate  RAM	 on  a
	       particular  platform,  the lower	bound of 30% is	used.  Setting
	       this parameter and  ggc-min-heapsize  to	 zero  causes  a  full
	       collection  to  occur  at every opportunity.  This is extremely
	       slow, but can be	useful for debugging.

	   ggc-min-heapsize
	       Minimum size of the garbage collector's heap before  it	begins
	       bothering  to  collect  garbage.	  The  first collection	occurs
	       after the  heap	expands	 by  ggc-min-expand%  beyond  ggc-min-
	       heapsize.   Again,  tuning  this	may improve compilation	speed,
	       and has no effect on code generation.

	       The default is the smaller of RAM/8,  RLIMIT_RSS,  or  a	 limit
	       that  tries  to	ensure	that  RLIMIT_DATA or RLIMIT_AS are not
	       exceeded, but with a lower bound	of 4096	(four  megabytes)  and
	       an  upper  bound	of 131072 (128 megabytes).  If GCC is not able
	       to calculate RAM	on a particular	platform, the lower  bound  is
	       used.   Setting	this parameter very large effectively disables
	       garbage collection.  Setting this parameter and	ggc-min-expand
	       to zero causes a	full collection	to occur at every opportunity.

	   max-reload-search-insns
	       The  maximum  number of instruction reload should look backward
	       for  equivalent	register.    Increasing	  values   mean	  more
	       aggressive  optimization,  making the compilation time increase
	       with probably slightly better performance.

	   max-cselib-memory-locations
	       The maximum number of memory locations cselib should take  into
	       account.	  Increasing values mean more aggressive optimization,
	       making the compilation time  increase  with  probably  slightly
	       better performance.

	   max-sched-ready-insns
	       The  maximum  number  of	 instructions  ready  to be issued the
	       scheduler should	consider at any	given time  during  the	 first
	       scheduling   pass.    Increasing	  values  mean	more  thorough
	       searches, making	the compilation	time  increase	with  probably
	       little benefit.

	   max-sched-region-blocks
	       The  maximum  number of blocks in a region to be	considered for
	       interblock scheduling.

	   max-pipeline-region-blocks
	       The maximum number of blocks in a region	to be  considered  for
	       pipelining in the selective scheduler.

	   max-sched-region-insns
	       The  maximum  number  of	insns in a region to be	considered for
	       interblock scheduling.

	   max-pipeline-region-insns
	       The maximum number of insns in a	region to  be  considered  for
	       pipelining in the selective scheduler.

	   min-spec-prob
	       The  minimum  probability  (in  percents)  of reaching a	source
	       block for interblock speculative	scheduling.

	   max-sched-extend-regions-iters
	       The maximum number of iterations	through	CFG to extend regions.
	       A value of 0 disables region extensions.

	   max-sched-insn-conflict-delay
	       The maximum conflict delay for an insn  to  be  considered  for
	       speculative motion.

	   sched-spec-prob-cutoff
	       The  minimal  probability of speculation	success	(in percents),
	       so that speculative insns are scheduled.

	   sched-state-edge-prob-cutoff
	       The minimum probability an edge must have for the scheduler  to
	       save its	state across it.

	   sched-mem-true-dep-cost
	       Minimal	distance  (in  CPU  cycles)  between  store  and  load
	       targeting same memory locations.

	   selsched-max-lookahead
	       The  maximum  size  of  the  lookahead  window	of   selective
	       scheduling.    It   is	a   depth   of	search	for  available
	       instructions.

	   selsched-max-sched-times
	       The maximum number of times that	an  instruction	 is  scheduled
	       during  selective  scheduling.  This is the limit on the	number
	       of iterations through which the instruction may be pipelined.

	   selsched-insns-to-rename
	       The maximum number of best instructions in the ready list  that
	       are considered for renaming in the selective scheduler.

	   sms-min-sc
	       The  minimum  value  of stage count that	swing modulo scheduler
	       generates.

	   max-last-value-rtl
	       The maximum size	 measured  as  number  of  RTLs	 that  can  be
	       recorded	 in an expression in combiner for a pseudo register as
	       last known value	of that	register.

	   max-combine-insns
	       The maximum number of instructions the RTL  combiner  tries  to
	       combine.

	   integer-share-limit
	       Small  integer  constants  can  use  a  shared  data structure,
	       reducing	the compiler's memory usage and	increasing its	speed.
	       This sets the maximum value of a	shared integer constant.

	   ssp-buffer-size
	       The  minimum  size  of buffers (i.e. arrays) that receive stack
	       smashing	protection when	-fstack-protection is used.

	   min-size-for-stack-sharing
	       The minimum size	of variables taking part in stack slot sharing
	       when not	optimizing.

	   max-jump-thread-duplication-stmts
	       Maximum number of statements allowed in a block that  needs  to
	       be duplicated when threading jumps.

	   max-fields-for-field-sensitive
	       Maximum	number	of  fields  in	a structure treated in a field
	       sensitive manner	during pointer analysis.

	   prefetch-latency
	       Estimate	on average number of instructions  that	 are  executed
	       before  prefetch	 finishes.   The  distance prefetched ahead is
	       proportional to this constant.  Increasing this number may also
	       lead  to	 less  streams	being  prefetched  (see	 simultaneous-
	       prefetches).

	   simultaneous-prefetches
	       Maximum number of prefetches that can run at the	same time.

	   l1-cache-line-size
	       The size	of cache line in L1 data cache,	in bytes.

	   l1-cache-size
	       The size	of L1 data cache, in kilobytes.

	   l2-cache-size
	       The size	of L2 data cache, in kilobytes.

	   prefetch-dynamic-strides
	       Whether	the  loop  array  prefetch  pass should	issue software
	       prefetch	hints for strides  that	 are  non-constant.   In  some
	       cases  this  may	 be  beneficial, though	the fact the stride is
	       non-constant may	make it	hard to	predict	when  there  is	 clear
	       benefit to issuing these	hints.

	       Set  to	1  if  the  prefetch  hints  should be issued for non-
	       constant	strides.  Set to 0 if prefetch hints should be	issued
	       only  for  strides  that	 are  known  to	 be constant and below
	       prefetch-minimum-stride.

	   prefetch-minimum-stride
	       Minimum constant	stride,	in  bytes,  to	start  using  prefetch
	       hints for.  If the stride is less than this threshold, prefetch
	       hints will not be issued.

	       This  setting  is  useful  for  processors  that	 have hardware
	       prefetchers, in which case there	may be conflicts  between  the
	       hardware	 prefetchers  and  the	software  prefetchers.	If the
	       hardware	prefetchers have a maximum stride they can handle,  it
	       should be used here to improve the use of software prefetchers.

	       A  value	 of  -1	 means we don't	have a threshold and therefore
	       prefetch	hints can be issued for	any constant stride.

	       This setting is only useful for	strides	 that  are  known  and
	       constant.

	   loop-interchange-max-num-stmts
	       The maximum number of stmts in a	loop to	be interchanged.

	   loop-interchange-stride-ratio
	       The  minimum  ratio between stride of two loops for interchange
	       to be profitable.

	   min-insn-to-prefetch-ratio
	       The minimum ratio between the number of	instructions  and  the
	       number of prefetches to enable prefetching in a loop.

	   prefetch-min-insn-to-mem-ratio
	       The  minimum  ratio  between the	number of instructions and the
	       number of memory	references to enable prefetching in a loop.

	   use-canonical-types
	       Whether the compiler should use the  "canonical"	 type  system.
	       Should  always  be  1,  which  uses  a  more efficient internal
	       mechanism  for  comparing  types	 in  C++  and	Objective-C++.
	       However,	 if  bugs  in  the  canonical  type system are causing
	       compilation failures, set this value to 0 to disable  canonical
	       types.

	   switch-conversion-max-branch-ratio
	       Switch  initialization conversion refuses to create arrays that
	       are bigger than	switch-conversion-max-branch-ratio  times  the
	       number of branches in the switch.

	   max-partial-antic-length
	       Maximum	length	of  the	 partial antic set computed during the
	       tree partial redundancy elimination  optimization  (-ftree-pre)
	       when  optimizing	 at  -O3  and above.  For some sorts of	source
	       code the	enhanced partial redundancy  elimination  optimization
	       can run away, consuming all of the memory available on the host
	       machine.	 This parameter	sets a limit on	the length of the sets
	       that   are  computed,  which  prevents  the  runaway  behavior.
	       Setting a value of 0 for	this parameter allows an unlimited set
	       length.

	   rpo-vn-max-loop-depth
	       Maximum loop depth that is value-numbered optimistically.  When
	       the limit hits the innermost  rpo-vn-max-loop-depth  loops  and
	       the   outermost	loop  in  the  loop  nest  are	value-numbered
	       optimistically and the remaining	ones not.

	   sccvn-max-alias-queries-per-access
	       Maximum number of alias-oracle queries we perform when  looking
	       for  redundancies  for  loads and stores.  If this limit	is hit
	       the search is aborted and the load or store is  not  considered
	       redundant.  The number of queries is algorithmically limited to
	       the number of stores on all paths from the load to the function
	       entry.

	   ira-max-loops-num
	       IRA  uses  regional  register  allocation  by  default.	 If  a
	       function	contains more loops than  the  number  given  by  this
	       parameter,   only   at  most  the  given	 number	 of  the  most
	       frequently-executed loops form regions  for  regional  register
	       allocation.

	   ira-max-conflict-table-size
	       Although	 IRA  uses  a  sophisticated algorithm to compress the
	       conflict	table, the table can still require  excessive  amounts
	       of  memory  for	huge  functions.   If the conflict table for a
	       function	could be more than  the	 size  in  MB  given  by  this
	       parameter,  the	register  allocator  instead  uses  a  faster,
	       simpler,	and lower-quality  algorithm  that  does  not  require
	       building	a pseudo-register conflict table.

	   ira-loop-reserved-regs
	       IRA  can	be used	to evaluate more accurate register pressure in
	       loops for decisions to move loop	 invariants  (see  -O3).   The
	       number  of available registers reserved for some	other purposes
	       is given	by this	parameter.  Default of the  parameter  is  the
	       best found from numerous	experiments.

	   lra-inheritance-ebb-probability-cutoff
	       LRA  tries  to reuse values reloaded in registers in subsequent
	       insns.  This optimization is called inheritance.	 EBB  is  used
	       as  a  region to	do this	optimization.  The parameter defines a
	       minimal fall-through edge probability in	percentage used	to add
	       BB to inheritance EBB in	LRA.  The  default  value  was	chosen
	       from numerous runs of SPEC2000 on x86-64.

	   loop-invariant-max-bbs-in-loop
	       Loop   invariant	  motion   can	be  very  expensive,  both  in
	       compilation time	and in amount of needed	 compile-time  memory,
	       with  very large	loops.	Loops with more	basic blocks than this
	       parameter  won't	 have  loop  invariant	 motion	  optimization
	       performed on them.

	   loop-max-datarefs-for-datadeps
	       Building	 data  dependencies is expensive for very large	loops.
	       This parameter limits the number	of data	 references  in	 loops
	       that  are considered for	data dependence	analysis.  These large
	       loops are no handled  by	 the  optimizations  using  loop  data
	       dependencies.

	   max-vartrack-size
	       Sets  a	maximum	 number	 of  hash  table  slots	 to use	during
	       variable	tracking dataflow analysis of any function.   If  this
	       limit   is  exceeded  with  variable  tracking  at  assignments
	       enabled,	analysis for that  function  is	 retried  without  it,
	       after removing all debug	insns from the function.  If the limit
	       is  exceeded even without debug insns, var tracking analysis is
	       completely disabled for the function.  Setting the parameter to
	       zero makes it unlimited.

	   max-vartrack-expr-depth
	       Sets a maximum number of	recursion levels  when	attempting  to
	       map  variable  names or debug temporaries to value expressions.
	       This  trades  compilation  time	 for   more   complete	 debug
	       information.   If  this	is set too low,	value expressions that
	       are available and could be represented in debug information may
	       end up not being	used;  setting	this  higher  may  enable  the
	       compiler	 to  find  more	complex	debug expressions, but compile
	       time and	memory use may grow.

	   max-debug-marker-count
	       Sets a threshold	on the number of  debug	 markers  (e.g.	 begin
	       stmt  markers)  to  avoid  complexity  explosion	at inlining or
	       expanding to RTL.  If a function	has  more  such	 gimple	 stmts
	       than the	set limit, such	stmts will be dropped from the inlined
	       copy of a function, and from its	RTL expansion.

	   min-nondebug-insn-uid
	       Use  uids  starting  at this parameter for nondebug insns.  The
	       range below the parameter is  reserved  exclusively  for	 debug
	       insns  created  by  -fvar-tracking-assignments, but debug insns
	       may get (non-overlapping) uids above it if the  reserved	 range
	       is exhausted.

	   ipa-sra-ptr-growth-factor
	       IPA-SRA replaces	a pointer to an	aggregate with one or more new
	       parameters  only	when their cumulative size is less or equal to
	       ipa-sra-ptr-growth-factor  times	 the  size  of	the   original
	       pointer parameter.

	   ipa-sra-max-replacements
	       Maximum	pieces	of  an	aggregate  that	 IPA-SRA tracks.  As a
	       consequence, it is also the maximum number of replacements of a
	       formal parameter.

	   sra-max-scalarization-size-Ospeed
	   sra-max-scalarization-size-Osize
	       The two Scalar Reduction	of Aggregates passes (SRA and IPA-SRA)
	       aim  to	replace	 scalar	 parts	of  aggregates	with  uses  of
	       independent  scalar  variables.	 These	parameters control the
	       maximum	size,  in  storage  units,  of	aggregate   which   is
	       considered  for	replacement when compiling for speed (sra-max-
	       scalarization-size-Ospeed) or size (sra-max-scalarization-size-
	       Osize) respectively.

	   sra-max-propagations
	       The  maximum  number  of	 artificial   accesses	 that	Scalar
	       Replacement  of	Aggregates  (SRA)  will	 track,	 per one local
	       variable, in order to facilitate	copy propagation.

	   tm-max-aggregate-size
	       When making copies of thread-local variables in a  transaction,
	       this   parameter	 specifies  the	 size  in  bytes  after	 which
	       variables are saved with	the logging functions  as  opposed  to
	       save/restore  code  sequence  pairs.   This option only applies
	       when using -fgnu-tm.

	   graphite-max-nb-scop-params
	       To avoid	exponential effects in the Graphite  loop  transforms,
	       the  number  of	parameters  in a Static	Control	Part (SCoP) is
	       bounded.	 A value of zero can be	used to	 lift  the  bound.   A
	       variable	whose value is unknown at compilation time and defined
	       outside a SCoP is a parameter of	the SCoP.

	   loop-block-tile-size
	       Loop   blocking	 or  strip  mining  transforms,	 enabled  with
	       -floop-block or -floop-strip-mine, strip	mine each loop in  the
	       loop  nest  by  a given number of iterations.  The strip	length
	       can be changed using the	loop-block-tile-size parameter.

	   ipa-jump-function-lookups
	       Specifies number	of statements  visited	during	jump  function
	       offset discovery.

	   ipa-cp-value-list-size
	       IPA-CP  attempts	 to track all possible values and types	passed
	       to a function's	parameter  in  order  to  propagate  them  and
	       perform	 devirtualization.    ipa-cp-value-list-size   is  the
	       maximum number of values	and types it  stores  per  one	formal
	       parameter of a function.

	   ipa-cp-eval-threshold
	       IPA-CP  calculates  its	own  score  of	cloning	 profitability
	       heuristics and performs those cloning opportunities with	scores
	       that exceed ipa-cp-eval-threshold.

	   ipa-cp-max-recursive-depth
	       Maximum depth of	recursive cloning for self-recursive function.

	   ipa-cp-min-recursive-probability
	       Recursive cloning only  when  the  probability  of  call	 being
	       executed	exceeds	the parameter.

	   ipa-cp-recursion-penalty
	       Percentage  penalty  the	 recursive functions will receive when
	       they are	evaluated for cloning.

	   ipa-cp-single-call-penalty
	       Percentage  penalty  functions  containing  a  single  call  to
	       another	function  will	receive	 when  they  are evaluated for
	       cloning.

	   ipa-max-agg-items
	       IPA-CP is also capable to propagate a number of	scalar	values
	       passed  in an aggregate.	ipa-max-agg-items controls the maximum
	       number of such values per one parameter.

	   ipa-cp-loop-hint-bonus
	       When IPA-CP determines that a cloning candidate would make  the
	       number  of  iterations of a loop	known, it adds a bonus of ipa-
	       cp-loop-hint-bonus to the profitability score of	the candidate.

	   ipa-max-loop-predicates
	       The maximum number of different	predicates  IPA	 will  use  to
	       describe	when loops in a	function have known properties.

	   ipa-max-aa-steps
	       During  its  analysis  of function bodies, IPA-CP employs alias
	       analysis	in order  to  track  values  pointed  to  by  function
	       parameters.   In	 order	not spend too much time	analyzing huge
	       functions, it gives up and consider all memory clobbered	 after
	       examining ipa-max-aa-steps statements modifying memory.

	   ipa-max-switch-predicate-bounds
	       Maximal	number	of boundary endpoints of case ranges of	switch
	       statement.  For switch exceeding	this limit,  IPA-CP  will  not
	       construct  cloning  cost	 predicate,  which is used to estimate
	       cloning benefit,	for default case of the	switch statement.

	   ipa-max-param-expr-ops
	       IPA-CP will analyze conditional statement that references  some
	       function	parameter to estimate benefit for cloning upon certain
	       constant	 value.	  But  if  number of operations	in a parameter
	       expression exceeds ipa-max-param-expr-ops,  the	expression  is
	       treated as complicated one, and is not handled by IPA analysis.

	   lto-partitions
	       Specify	desired	 number	 of  partitions	 produced during WHOPR
	       compilation.  The number	of partitions should exceed the	number
	       of CPUs used for	compilation.

	   lto-min-partition
	       Size   of   minimal   partition	 for   WHOPR   (in   estimated
	       instructions).	This prevents expenses of splitting very small
	       programs	into too many partitions.

	   lto-max-partition
	       Size of max partition for WHOPR	(in  estimated	instructions).
	       to  provide  an	upper  bound for individual size of partition.
	       Meant to	be used	only with balanced partitioning.

	   lto-max-streaming-parallelism
	       Maximal number of parallel processes used for LTO streaming.

	   cxx-max-namespaces-for-diagnostic-help
	       The maximum number of namespaces	 to  consult  for  suggestions
	       when C++	name lookup fails for an identifier.

	   sink-frequency-threshold
	       The  maximum  relative execution	frequency (in percents)	of the
	       target block relative to	a statement's original block to	 allow
	       statement  sinking  of  a  statement.  Larger numbers result in
	       more aggressive statement sinking.  A small positive adjustment
	       is applied for statements with memory  operands	as  those  are
	       even more profitable so sink.

	   max-stores-to-sink
	       The maximum number of conditional store pairs that can be sunk.
	       Set  to	0  if  either  vectorization (-ftree-vectorize)	or if-
	       conversion (-ftree-loop-if-convert) is disabled.

	   case-values-threshold
	       The smallest number of different	values for which it is best to
	       use a jump-table	instead	of a tree of conditional branches.  If
	       the value is 0, use the default for the machine.

	   jump-table-max-growth-ratio-for-size
	       The maximum code	size growth ratio when expanding into  a  jump
	       table  (in percent).  The parameter is used when	optimizing for
	       size.

	   jump-table-max-growth-ratio-for-speed
	       The maximum code	size growth ratio when expanding into  a  jump
	       table  (in percent).  The parameter is used when	optimizing for
	       speed.

	   tree-reassoc-width
	       Set the maximum number of instructions executed in parallel  in
	       reassociated  tree.  This  parameter overrides target dependent
	       heuristics used by default if has non zero value.

	   sched-pressure-algorithm
	       Choose	between	  the	two   available	  implementations   of
	       -fsched-pressure.   Algorithm  1	is the original	implementation
	       and is the more	likely	to  prevent  instructions  from	 being
	       reordered.  Algorithm 2 was designed to be a compromise between
	       the  relatively	conservative approach taken by algorithm 1 and
	       the rather aggressive approach taken by the default  scheduler.
	       It  relies  more	 heavily on having a regular register file and
	       accurate	register pressure classes.  See	haifa-sched.c  in  the
	       GCC sources for more details.

	       The default choice depends on the target.

	   max-slsr-cand-scan
	       Set   the  maximum  number  of  existing	 candidates  that  are
	       considered  when	 seeking  a  basis  for	 a  new	 straight-line
	       strength	reduction candidate.

	   asan-globals
	       Enable buffer overflow detection	for global objects.  This kind
	       of   protection	 is  enabled  by  default  if  you  are	 using
	       -fsanitize=address   option.    To   disable   global   objects
	       protection use --param asan-globals=0.

	   asan-stack
	       Enable  buffer overflow detection for stack objects.  This kind
	       of   protection	 is   enabled	by    default	 when	 using
	       -fsanitize=address.   To	 disable  stack	protection use --param
	       asan-stack=0 option.

	   asan-instrument-reads
	       Enable buffer overflow detection	for memory reads.   This  kind
	       of    protection	   is	 enabled   by	default	  when	 using
	       -fsanitize=address.  To disable	memory	reads  protection  use
	       --param asan-instrument-reads=0.

	   asan-instrument-writes
	       Enable  buffer overflow detection for memory writes.  This kind
	       of   protection	 is   enabled	by    default	 when	 using
	       -fsanitize=address.   To	 disable  memory writes	protection use
	       --param asan-instrument-writes=0	option.

	   asan-memintrin
	       Enable  detection  for  built-in	 functions.   This   kind   of
	       protection is enabled by	default	when using -fsanitize=address.
	       To   disable   built-in	 functions   protection	  use  --param
	       asan-memintrin=0.

	   asan-use-after-return
	       Enable detection	of use-after-return.  This kind	of  protection
	       is enabled by default when using	the -fsanitize=address option.
	       To disable it use --param asan-use-after-return=0.

	       Note:  By default the check is disabled at run time.  To	enable
	       it, add "detect_stack_use_after_return=1"  to  the  environment
	       variable	ASAN_OPTIONS.

	   asan-instrumentation-with-call-threshold
	       If  number of memory accesses in	function being instrumented is
	       greater or equal	to  this  number,  use	callbacks  instead  of
	       inline  checks.	 E.g.  to  disable  inline  code  use  --param
	       asan-instrumentation-with-call-threshold=0.

	   hwasan-instrument-stack
	       Enable  hwasan  instrumentation	of  statically	sized	stack-
	       allocated  variables.   This kind of instrumentation is enabled
	       by default when	using  -fsanitize=hwaddress  and  disabled  by
	       default	when  using  -fsanitize=kernel-hwaddress.   To disable
	       stack instrumentation  use  --param  hwasan-instrument-stack=0,
	       and to enable it	use --param hwasan-instrument-stack=1.

	   hwasan-random-frame-tag
	       When   using  stack  instrumentation,  decide  tags  for	 stack
	       variables using a deterministic sequence	beginning at a	random
	       tag  for	each frame.  With this parameter unset tags are	chosen
	       using the same sequence but beginning from 1.  This is  enabled
	       by   default   for  -fsanitize=hwaddress	 and  unavailable  for
	       -fsanitize=kernel-hwaddress.   To  disable   it	 use   --param
	       hwasan-random-frame-tag=0.

	   hwasan-instrument-allocas
	       Enable  hwasan  instrumentation	of  dynamically	 sized	stack-
	       allocated variables.  This kind of instrumentation  is  enabled
	       by  default  when  using	 -fsanitize=hwaddress  and disabled by
	       default when  using  -fsanitize=kernel-hwaddress.   To  disable
	       instrumentation	   of	  such	   variables	use    --param
	       hwasan-instrument-allocas=0,  and  to  enable  it  use  --param
	       hwasan-instrument-allocas=1.

	   hwasan-instrument-reads
	       Enable hwasan checks on memory reads.  Instrumentation of reads
	       is   enabled  by	 default  for  both  -fsanitize=hwaddress  and
	       -fsanitize=kernel-hwaddress.  To	disable	checking memory	 reads
	       use --param hwasan-instrument-reads=0.

	   hwasan-instrument-writes
	       Enable  hwasan  checks  on  memory  writes.  Instrumentation of
	       writes is enabled by default for	both -fsanitize=hwaddress  and
	       -fsanitize=kernel-hwaddress.  To	disable	checking memory	writes
	       use --param hwasan-instrument-writes=0.

	   hwasan-instrument-mem-intrinsics
	       Enable	 hwasan	   instrumentation   of	  builtin   functions.
	       Instrumentation	of  these  builtin  functions  is  enabled  by
	       default	     for       both	 -fsanitize=hwaddress	   and
	       -fsanitize=kernel-hwaddress.   To  disable  instrumentation  of
	       builtin		   functions		use	       --param
	       hwasan-instrument-mem-intrinsics=0.

	   use-after-scope-direct-emission-threshold
	       If the size of a	local variable in bytes	is smaller or equal to
	       this  number,  directly	poison	(or  unpoison)	shadow	memory
	       instead of using	run-time callbacks.

	   tsan-distinguish-volatile
	       Emit special instrumentation for	accesses to volatiles.

	   tsan-instrument-func-entry-exit
	       Emit   instrumentation	calls	to   __tsan_func_entry()   and
	       __tsan_func_exit().

	   max-fsm-thread-path-insns
	       Maximum number of instructions to copy when duplicating	blocks
	       on a finite state automaton jump	thread path.

	   max-fsm-thread-length
	       Maximum number of basic blocks on a finite state	automaton jump
	       thread path.

	   max-fsm-thread-paths
	       Maximum	number of new jump thread paths	to create for a	finite
	       state automaton.

	   parloops-chunk-size
	       Chunk size of omp schedule for loops parallelized by parloops.

	   parloops-schedule
	       Schedule	 type  of  omp	schedule  for  loops  parallelized  by
	       parloops	(static, dynamic, guided, auto,	runtime).

	   parloops-min-per-thread
	       The  minimum  number  of	 iterations per	thread of an innermost
	       parallelized  loop  for	which  the  parallelized  variant   is
	       preferred  over	the  single  threaded  one.   Note  that for a
	       parallelized loop nest the minimum number of iterations of  the
	       outermost loop per thread is two.

	   max-ssa-name-query-depth
	       Maximum	depth  of  recursion  when  querying properties	of SSA
	       names in	things like fold routines.   One  level	 of  recursion
	       corresponds to following	a use-def chain.

	   max-speculative-devirt-maydefs
	       The  maximum  number  of	may-defs we analyze when looking for a
	       must-def	specifying the dynamic type of an object that  invokes
	       a virtual call we may be	able to	devirtualize speculatively.

	   max-vrp-switch-assertions
	       The  maximum number of assertions to add	along the default edge
	       of a switch statement during VRP.

	   evrp-mode
	       Specifies the mode Early	VRP should operate in.

	   unroll-jam-min-percent
	       The minimum  percentage	of  memory  references	that  must  be
	       optimized  away	for  the  unroll-and-jam  transformation to be
	       considered profitable.

	   unroll-jam-max-unroll
	       The maximum number of times the outer loop should  be  unrolled
	       by the unroll-and-jam transformation.

	   max-rtl-if-conversion-unpredictable-cost
	       Maximum	permissible  cost  for	the  sequence  that  would  be
	       generated by the	RTL if-conversion pass for a  branch  that  is
	       considered unpredictable.

	   max-variable-expansions-in-unroller
	       If -fvariable-expansion-in-unroller is used, the	maximum	number
	       of  times  that	an individual variable will be expanded	during
	       loop unrolling.

	   tracer-min-branch-probability-feedback
	       Stop forward growth if the probability of  best	edge  is  less
	       than this threshold (in percent). Used when profile feedback is
	       available.

	   partial-inlining-entry-probability
	       Maximum probability of the entry	BB of split region (in percent
	       relative	 to entry BB of	the function) to make partial inlining
	       happen.

	   max-tracked-strlens
	       Maximum number of strings for which  strlen  optimization  pass
	       will track string lengths.

	   gcse-after-reload-partial-fraction
	       The   threshold	 ratio	 for   performing  partial  redundancy
	       elimination after reload.

	   gcse-after-reload-critical-fraction
	       The threshold ratio of  critical	 edges	execution  count  that
	       permit performing redundancy elimination	after reload.

	   max-loop-header-insns
	       The  maximum  number  of	insns in loop header duplicated	by the
	       copy loop headers pass.

	   vect-epilogues-nomask
	       Enable loop epilogue vectorization using	smaller	vector size.

	   vect-partial-vector-usage
	       Controls	when  the  loop	 vectorizer  considers	using  partial
	       vector  loads  and  stores as an	alternative to falling back to
	       scalar code.  0 stops the vectorizer from  ever	using  partial
	       vector  loads  and  stores.   1 allows partial vector loads and
	       stores if vectorization	removes	 the  need  for	 the  code  to
	       iterate.	  2  allows  partial  vector  loads  and stores	in all
	       loops.  The parameter  only  has	 an  effect  on	 targets  that
	       support partial vector loads and	stores.

	   avoid-fma-max-bits
	       Maximum number of bits for which	we avoid creating FMAs.

	   sms-loop-average-count-threshold
	       A  threshold  on	the average loop count considered by the swing
	       modulo scheduler.

	   sms-dfa-history
	       The number of cycles the	swing modulo scheduler considers  when
	       checking	conflicts using	DFA.

	   max-inline-insns-recursive-auto
	       The maximum number of instructions non-inline function can grow
	       to via recursive	inlining.

	   graphite-allow-codegen-errors
	       Whether codegen errors should be	ICEs when -fchecking.

	   sms-max-ii-factor
	       A factor	for tuning the upper bound that	swing modulo scheduler
	       uses for	scheduling a loop.

	   lra-max-considered-reload-pseudos
	       The  max	 number	 of reload pseudos which are considered	during
	       spilling	a non-reload pseudo.

	   max-pow-sqrt-depth
	       Maximum	depth  of  sqrt	 chains	 to  use   when	  synthesizing
	       exponentiation by a real	constant.

	   max-dse-active-local-stores
	       Maximum	number	of  active  local  stores  in  RTL  dead store
	       elimination.

	   asan-instrument-allocas
	       Enable asan allocas/VLAs	protection.

	   max-iterations-computation-cost
	       Bound on	the cost of an expression to  compute  the  number  of
	       iterations.

	   max-isl-operations
	       Maximum number of isl operations, 0 means unlimited.

	   graphite-max-arrays-per-scop
	       Maximum number of arrays	per scop.

	   max-vartrack-reverse-op-size
	       Max. size of loc	list for which reverse ops should be added.

	   tracer-dynamic-coverage-feedback
	       The  percentage	of  function, weighted by execution frequency,
	       that must be covered by trace  formation.   Used	 when  profile
	       feedback	is available.

	   max-inline-recursive-depth-auto
	       The   maximum   depth  of  recursive  inlining  for  non-inline
	       functions.

	   fsm-scale-path-stmts
	       Scale factor  to	 apply	to  the	 number	 of  statements	 in  a
	       threading path when comparing to	the number of (scaled) blocks.

	   fsm-maximum-phi-arguments
	       Maximum	number	of  arguments  a  PHI  may have	before the FSM
	       threader	will not try to	thread through its block.

	   uninit-control-dep-attempts
	       Maximum	number	of  nested  calls  to	search	 for   control
	       dependencies during uninitialized variable analysis.

	   sra-max-scalarization-size-Osize
	       Maximum size, in	storage	units, of an aggregate which should be
	       considered for scalarization when compiling for size.

	   fsm-scale-path-blocks
	       Scale  factor  to  apply	to the number of blocks	in a threading
	       path when comparing to the number of (scaled) statements.

	   sched-autopref-queue-depth
	       Hardware	autoprefetcher scheduler model control	flag.	Number
	       of  lookahead  cycles  the model	looks into; at ' ' only	enable
	       instruction sorting heuristic.

	   loop-versioning-max-inner-insns
	       The maximum number of instructions that an inner	loop can  have
	       before the loop versioning pass considers it too	big to copy.

	   loop-versioning-max-outer-insns
	       The  maximum number of instructions that	an outer loop can have
	       before the loop versioning pass considers it too	big  to	 copy,
	       discounting  any	 instructions  in  inner  loops	 that directly
	       benefit from versioning.

	   ssa-name-def-chain-limit
	       The  maximum  number  of	 SSA_NAME  assignments	to  follow  in
	       determining  a  property	of a variable such as its value.  This
	       limits the number of iterations or recursive calls GCC performs
	       when optimizing certain statements or  when  determining	 their
	       validity	prior to issuing diagnostics.

	   store-merging-max-size
	       Maximum size of a single	store merging region in	bytes.

	   hash-table-verification-limit
	       The  number  of	elements  for which hash table verification is
	       done for	each searched element.

	   max-find-base-term-values
	       Maximum number of VALUEs	handled	during a single	find_base_term
	       call.

	   analyzer-max-enodes-per-program-point
	       The maximum number of exploded nodes per	program	 point	within
	       the analyzer, before terminating	analysis of that point.

	   analyzer-max-constraints
	       The maximum number of constraints per state.

	   analyzer-min-snodes-for-call-summary
	       The  minimum  number  of	 supernodes  within a function for the
	       analyzer	to consider summarizing	its effects at call sites.

	   analyzer-max-enodes-for-full-dump
	       The maximum depth of exploded nodes that	should appear in a dot
	       dump before switching to	a less verbose format.

	   analyzer-max-recursion-depth
	       The maximum number of times a callsite can  appear  in  a  call
	       stack  within  the  analyzer,  before terminating analysis of a
	       call that would recurse deeper.

	   analyzer-max-svalue-depth
	       The maximum depth of a symbolic value, before approximating the
	       value as	unknown.

	   analyzer-max-infeasible-edges
	       The  maximum  number  of	 infeasible  edges  to	reject	before
	       declaring a diagnostic as infeasible.

	   gimple-fe-computed-hot-bb-threshold
	       The  number  of executions of a basic block which is considered
	       hot.  The parameter is used only	in GIMPLE FE.

	   analyzer-bb-explosion-factor
	       The maximum number of 'after supernode' exploded	 nodes	within
	       the analyzer per	supernode, before terminating analysis.

	   ranger-logical-depth
	       Maximum depth of	logical	expression evaluation ranger will look
	       through when evaluating outgoing	edge ranges.

	   openacc-kernels
	       Specify	mode  of  OpenACC `kernels' constructs handling.  With
	       --param=openacc-kernels=decompose, OpenACC `kernels' constructs
	       are decomposed into parts, a sequence  of  compute  constructs,
	       each  then  handled  individually.   This  is work in progress.
	       With   --param=openacc-kernels=parloops,	  OpenACC    `kernels'
	       constructs  are handled by the parloops pass, en	bloc.  This is
	       the current default.

	   The following choices of name are available on AArch64 targets:

	   aarch64-sve-compare-costs
	       When vectorizing	for SVE, consider using	"unpacked" vectors for
	       smaller elements	and use	the cost model to  pick	 the  cheapest
	       approach.   Also	 use  the cost model to	choose between SVE and
	       Advanced	SIMD vectorization.

	       Using unpacked vectors includes	storing	 smaller  elements  in
	       larger  containers  and accessing elements with extending loads
	       and truncating stores.

	   aarch64-float-recp-precision
	       The number of Newton iterations for calculating the  reciprocal
	       for  float  type.  The precision	of division is proportional to
	       this param when division	approximation is enabled.  The default
	       value is	1.

	   aarch64-double-recp-precision
	       The number of Newton iterations for calculating the  reciprocal
	       for  double  type.  The precision of division is	propotional to
	       this param when division	approximation is enabled.  The default
	       value is	2.

	   aarch64-autovec-preference
	       Force  an  ISA  selection  strategy   for   auto-vectorization.
	       Accepts values from 0 to	4, inclusive.

	       0   Use the default heuristics.

	       1   Use only Advanced SIMD for auto-vectorization.

	       2   Use only SVE	for auto-vectorization.

	       3   Use	both Advanced SIMD and SVE.  Prefer Advanced SIMD when
		   the costs are deemed	equal.

	       4   Use both Advanced SIMD and SVE.  Prefer SVE when the	 costs
		   are deemed equal.

	       The default value is 0.

	   aarch64-loop-vect-issue-rate-niters
	       The  tuning  for	some AArch64 CPUs tries	to take	both latencies
	       and issue rates into  account  when  deciding  whether  a  loop
	       should be vectorized using SVE, vectorized using	Advanced SIMD,
	       or  not	vectorized at all.  If this parameter is set to	n, GCC
	       will not	use this heuristic for loops that are known to execute
	       in fewer	than n Advanced	SIMD iterations.

   Program Instrumentation Options
       GCC supports a number of	command-line options that control adding  run-
       time  instrumentation  to the code it normally generates.  For example,
       one purpose of instrumentation is collect profiling statistics for  use
       in finding program hot spots, code coverage analysis, or	profile-guided
       optimizations.  Another class of	program	instrumentation	is adding run-
       time  checking  to  detect  programming	errors	like  invalid  pointer
       dereferences or out-of-bounds array accesses, as	well  as  deliberately
       hostile	attacks	such as	stack smashing or C++ vtable hijacking.	 There
       is also a general hook which can	be used	to implement  other  forms  of
       tracing or function-level instrumentation for debug or program analysis
       purposes.

       -p
       -pg Generate  extra  code to write profile information suitable for the
	   analysis program prof (for -p) or gprof (for	-pg).	You  must  use
	   this	 option	 when  compiling the source files you want data	about,
	   and you must	also use it when linking.

	   You can use	the  function  attribute  "no_instrument_function"  to
	   suppress  profiling	of  individual	functions  when	compiling with
	   these options.

       -fprofile-arcs
	   Add code so	that  program  flow  arcs  are	instrumented.	During
	   execution  the  program records how many times each branch and call
	   is executed and how many times it is	taken or returns.  On  targets
	   that	support	constructors with priority support, profiling properly
	   handles   constructors,   destructors  and  C++  constructors  (and
	   destructors)	of classes which are  used  as	a  type	 of  a	global
	   variable.

	   When	the compiled program exits it saves this data to a file	called
	   auxname.gcda	 for  each  source  file.   The	 data  may be used for
	   profile-directed  optimizations  (-fbranch-probabilities),  or  for
	   test	 coverage  analysis  (-ftest-coverage).	  Each	object	file's
	   auxname  is	generated  from	 the  name  of	the  output  file,  if
	   explicitly  specified and it	is not the final executable, otherwise
	   it is the basename of the source file.  In both cases any suffix is
	   removed (e.g. foo.gcda for input file  dir/foo.c,  or  dir/foo.gcda
	   for output file specified as	-o dir/foo.o).

       --coverage
	   This	 option	 is  used  to  compile	and link code instrumented for
	   coverage analysis.  The option  is  a  synonym  for	-fprofile-arcs
	   -ftest-coverage  (when  compiling)  and -lgcov (when	linking).  See
	   the documentation for those options for more	details.

	   *   Compile the source files	with -fprofile-arcs plus  optimization
	       and  code  generation options.  For test	coverage analysis, use
	       the additional -ftest-coverage option.	You  do	 not  need  to
	       profile every source file in a program.

	   *   Compile	the  source files additionally with -fprofile-abs-path
	       to create absolute path names in	the .gcno files.  This	allows
	       gcov to find the	correct	sources	in projects where compilations
	       occur with different working directories.

	   *   Link  your  object  files  with	-lgcov	or -fprofile-arcs (the
	       latter implies the former).

	   *   Run the program on a representative workload  to	 generate  the
	       arc  profile  information.   This may be	repeated any number of
	       times.  You can run concurrent instances	of your	 program,  and
	       provided	 that the file system supports locking,	the data files
	       will be correctly updated.   Unless  a  strict  ISO  C  dialect
	       option  is  in  effect, "fork" calls are	detected and correctly
	       handled without double counting.

	   *   For profile-directed optimizations, compile  the	 source	 files
	       again  with  the	 same optimization and code generation options
	       plus -fbranch-probabilities.

	   *   For test	coverage analysis, use gcov to produce human  readable
	       information  from the .gcno and .gcda files.  Refer to the gcov
	       documentation for further information.

	   With	-fprofile-arcs,	for each function of your program GCC  creates
	   a  program  flow  graph,  then finds	a spanning tree	for the	graph.
	   Only	 arcs  that  are  not  on  the	spanning  tree	have   to   be
	   instrumented:  the  compiler	adds code to count the number of times
	   that	these arcs are executed.  When an arc is the only exit or only
	   entrance to a block,	the instrumentation code can be	added  to  the
	   block;  otherwise,  a  new  basic block must	be created to hold the
	   instrumentation code.

       -ftest-coverage
	   Produce a notes file	that the gcov code-coverage utility can	use to
	   show	program	coverage.  Each	source	file's	note  file  is	called
	   auxname.gcno.   Refer  to  the  -fprofile-arcs  option  above for a
	   description of auxname and instructions on  how  to	generate  test
	   coverage data.  Coverage data matches the source files more closely
	   if you do not optimize.

       -fprofile-abs-path
	   Automatically  convert  relative source file	names to absolute path
	   names in the	.gcno files.  This allows gcov	to  find  the  correct
	   sources in projects where compilations occur	with different working
	   directories.

       -fprofile-dir=path
	   Set	the directory to search	for the	profile	data files in to path.
	   This	 option	 affects  only	 the   profile	 data	generated   by
	   -fprofile-generate,	-ftest-coverage,  -fprofile-arcs  and  used by
	   -fprofile-use and -fbranch-probabilities and	its  related  options.
	   Both	absolute and relative paths can	be used.  By default, GCC uses
	   the	current	 directory as path, thus the profile data file appears
	   in the same directory as the	object file.  In order to prevent  the
	   file	 name  clashing,  if  the  object file name is not an absolute
	   path, we mangle the absolute	path of	the sourcename.gcda  file  and
	   use	it  as	the  file  name	 of  a .gcda file.  See	similar	option
	   -fprofile-note.

	   When	an executable is run in	a massive parallel environment,	it  is
	   recommended to save profile to different folders.  That can be done
	   with	variables in path that are exported during run-time:

	   %p  process ID.

	   %q{VAR}
	       value of	environment variable VAR

       -fprofile-generate
       -fprofile-generate=path
	   Enable  options  usually  used  for	instrumenting  application  to
	   produce  profile  useful  for  later	 recompilation	with   profile
	   feedback  based optimization.  You must use -fprofile-generate both
	   when	compiling and when linking your	program.

	   The	  following    options	  are	  enabled:     -fprofile-arcs,
	   -fprofile-values, -finline-functions, and -fipa-bit-cp.

	   If  path  is	 specified,  GCC looks at the path to find the profile
	   feedback data files.	See -fprofile-dir.

	   To optimize the program based on the	collected profile information,
	   use -fprofile-use.

       -fprofile-info-section
       -fprofile-info-section=name
	   Register the	profile	information in the specified  section  instead
	   of  using a constructor/destructor.	The section name is name if it
	   is specified, otherwise the section name defaults to	 ".gcov_info".
	   A pointer to	the profile information	generated by -fprofile-arcs or
	   -ftest-coverage  is	placed	in  the	 specified  section  for  each
	   translation unit.  This option  disables  the  profile  information
	   registration	 through  a  constructor  and  it disables the profile
	   information processing through a destructor.	 This  option  is  not
	   intended  to	 be used in hosted environments	such as	GNU/Linux.  It
	   targets  systems  with  limited  resources  which  do  not  support
	   constructors	 and  destructors.  The	linker could collect the input
	   sections in a continuous memory block  and  define  start  and  end
	   symbols.   The runtime support could	dump the profiling information
	   registered in this linker  set  during  program  termination	 to  a
	   serial line for example.  A GNU linker script example which defines
	   a linker output section follows:

		     .gcov_info	     :
		     {
		       PROVIDE (__gcov_info_start = .);
		       KEEP (*(.gcov_info))
		       PROVIDE (__gcov_info_end	= .);
		     }

       -fprofile-note=path
	   If  path is specified, GCC saves .gcno file into path location.  If
	   you combine the option with multiple	source files, the  .gcno  file
	   will	be overwritten.

       -fprofile-prefix-path=path
	   This	    option     can     be    used    in	   combination	  with
	   profile-generate=profile_dir	and profile-use=profile_dir to	inform
	   GCC	where  is the base directory of	built source tree.  By default
	   profile_dir will contain files with mangled absolute	paths  of  all
	   object  files  in  the  built  project.  This is not	desirable when
	   directory used to build the instrumented binary  differs  from  the
	   directory  used to build the	binary optimized with profile feedback
	   because the profile data will not be	 found	during	the  optimized
	   build.    In	  such	setups	-fprofile-prefix-path=path  with  path
	   pointing to the base	directory of the build can be  used  to	 strip
	   the irrelevant part of the path and keep all	file names relative to
	   the main build directory.

       -fprofile-update=method
	   Alter the update method for an application instrumented for profile
	   feedback  based optimization.  The method argument should be	one of
	   single, atomic or prefer-atomic.   The  first  one  is  useful  for
	   single-threaded applications, while the second one prevents profile
	   corruption by emitting thread-safe code.

	   Warning: When an application	does not properly join all threads (or
	   creates an detached thread),	a profile file can be still corrupted.

	   Using  prefer-atomic	 would	be  transformed	either to atomic, when
	   supported by	a target, or to	 single	 otherwise.   The  GCC	driver
	   automatically selects prefer-atomic when -pthread is	present	in the
	   command line.

       -fprofile-filter-files=regex
	   Instrument  only functions from files whose name matches any	of the
	   regular expressions (separated by semi-colons).

	   For	 example,   -fprofile-filter-files=main\.c;module.*\.c	  will
	   instrument only main.c and all C files starting with	'module'.

       -fprofile-exclude-files=regex
	   Instrument  only functions from files whose name does not match any
	   of the regular expressions (separated by semi-colons).

	   For	 example,   -fprofile-exclude-files=/usr/.*    will    prevent
	   instrumentation of all files	that are located in the	/usr/ folder.

       -fprofile-reproducible=[multithreaded|parallel-runs|serial]
	   Control   level   of	  reproducibility   of	 profile  gathered  by
	   "-fprofile-generate".  This makes it	possible  to  rebuild  program
	   with	 same  outcome	which is useful, for example, for distribution
	   packages.

	   With	 -fprofile-reproducible=serial	 the   profile	 gathered   by
	   -fprofile-generate  is  reproducible	 provided  the trained program
	   behaves the same at each invocation of the train  run,  it  is  not
	   multi-threaded  and	profile	 data  streaming is always done	in the
	   same	order.	Note that profile streaming  happens  at  the  end  of
	   program run but also	before "fork" function is invoked.

	   Note	 that it is quite common that execution	counts of some part of
	   programs depends, for example, on length of temporary file names or
	   memory space	randomization (that may	 affect	 hash-table  collision
	   rate).   Such non-reproducible part of programs may be annotated by
	   "no_instrument_function" function attribute.	gcov-dump with -l  can
	   be  used  to	 dump  gathered	 data  and verify that they are	indeed
	   reproducible.

	   With	-fprofile-reproducible=parallel-runs collected	profile	 stays
	   reproducible	 regardless  the  order	 of streaming of the data into
	   gcda	files.	 This  setting	makes  it  possible  to	 run  multiple
	   instances  of  instrumented program in parallel (such as with "make
	   -j"). This reduces quality  of  gathered  data,  in	particular  of
	   indirect call profiling.

       -fsanitize=address
	   Enable  AddressSanitizer,  a	 fast  memory  error detector.	Memory
	   access instructions are instrumented	to  detect  out-of-bounds  and
	   use-after-free	 bugs.	       The	  option       enables
	   -fsanitize-address-use-after-scope.				   See
	   <https://github.com/google/sanitizers/wiki/AddressSanitizer>	   for
	   more	details.  The run-time behavior	can be	influenced  using  the
	   ASAN_OPTIONS	 environment  variable.	  When	set  to	 "help=1", the
	   available options are shown at startup of the instrumented program.
	   See
	   <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags>
	   for a list of supported options.  The  option  cannot  be  combined
	   with	-fsanitize=thread or -fsanitize=hwaddress.  Note that the only
	   target -fsanitize=hwaddress is currently supported on is AArch64.

       -fsanitize=kernel-address
	   Enable      AddressSanitizer	    for	    Linux     kernel.	   See
	   <https://github.com/google/kasan> for more details.

       -fsanitize=hwaddress
	   Enable Hardware-assisted AddressSanitizer, which  uses  a  hardware
	   ability  to ignore the top byte of a	pointer	to allow the detection
	   of memory  errors  with  a  low  memory  overhead.	Memory	access
	   instructions	 are  instrumented  to	detect	out-of-bounds and use-
	   after-free	     bugs.	    The		option	       enables
	   -fsanitize-address-use-after-scope.				   See
	   <https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html>
	   for more details.  The run-time behavior can	 be  influenced	 using
	   the HWASAN_OPTIONS environment variable.  When set to "help=1", the
	   available options are shown at startup of the instrumented program.
	   The	 option	  cannot   be	combined   with	 -fsanitize=thread  or
	   -fsanitize=address, and is currently	only available on AArch64.

       -fsanitize=kernel-hwaddress
	   Enable Hardware-assisted AddressSanitizer for  compilation  of  the
	   Linux  kernel.   Similar  to	-fsanitize=kernel-address but using an
	   alternate	instrumentation	    method,	and	similar	    to
	   -fsanitize=hwaddress	but with instrumentation differences necessary
	   for	compiling  the	Linux  kernel.	These differences are to avoid
	   hwasan library initialization calls and to account  for  the	 stack
	   pointer having a different value in its top byte.

	   Note:    This    option    has    different	  defaults    to   the
	   -fsanitize=hwaddress.  Instrumenting	the stack and alloca calls are
	   not on by default but are still possible by specifying the command-
	   line	 options   --param   hwasan-instrument-stack=1	 and   --param
	   hwasan-instrument-allocas=1	respectively. Using a random frame tag
	   is not implemented for kernel instrumentation.

       -fsanitize=pointer-compare
	   Instrument  comparison  operation  (<,  <=,	>,  >=)	 with  pointer
	   operands.	 The	option	  must	 be   combined	 with	either
	   -fsanitize=kernel-address or	-fsanitize=address The	option	cannot
	   be  combined	with -fsanitize=thread.	 Note: By default the check is
	   disabled    at     run     time.	 To	enable	   it,	   add
	   "detect_invalid_pointer_pairs=2"   to   the	 environment  variable
	   ASAN_OPTIONS.   Using   "detect_invalid_pointer_pairs=1"    detects
	   invalid operation only when both pointers are non-null.

       -fsanitize=pointer-subtract
	   Instrument  subtraction  with pointer operands.  The	option must be
	   combined	with	 either	     -fsanitize=kernel-address	    or
	   -fsanitize=address	 The	option	 cannot	  be   combined	  with
	   -fsanitize=thread.  Note: By	default	the check is disabled  at  run
	   time.   To  enable  it, add "detect_invalid_pointer_pairs=2"	to the
	   environment		variable	  ASAN_OPTIONS.		 Using
	   "detect_invalid_pointer_pairs=1"  detects  invalid  operation  only
	   when	both pointers are non-null.

       -fsanitize=thread
	   Enable ThreadSanitizer, a fast data race detector.	Memory	access
	   instructions	 are  instrumented  to	detect	data  race  bugs.  See
	   <https://github.com/google/sanitizers/wiki#threadsanitizer>	   for
	   more	 details.  The	run-time  behavior can be influenced using the
	   TSAN_OPTIONS		 environment	       variable;	   see
	   <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags>
	   for	a  list	 of  supported options.	 The option cannot be combined
	   with	-fsanitize=address, -fsanitize=leak.

	   Note	that sanitized atomic builtins cannot  throw  exceptions  when
	   operating  on  invalid  memory  addresses  with non-call exceptions
	   (-fnon-call-exceptions).

       -fsanitize=leak
	   Enable LeakSanitizer, a memory leak	detector.   This  option  only
	   matters  for	 linking  of  executables and the executable is	linked
	   against a library  that  overrides  "malloc"	 and  other  allocator
	   functions.							   See
	   <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer>
	   for more details.  The run-time behavior can	 be  influenced	 using
	   the	LSAN_OPTIONS  environment  variable.   The  option  cannot  be
	   combined with -fsanitize=thread.

       -fsanitize=undefined
	   Enable  UndefinedBehaviorSanitizer,	a  fast	  undefined   behavior
	   detector.	Various	  computations	 are  instrumented  to	detect
	   undefined	     behavior	      at	 runtime.	   See
	   <https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html>   for
	   more	details.   The run-time	behavior can be	influenced  using  the
	   UBSAN_OPTIONS environment variable.	Current	suboptions are:

	   -fsanitize=shift
	       This  option  enables  checking	that  the  result  of  a shift
	       operation  is  not  undefined.	Note  that  what  exactly   is
	       considered  undefined  differs  slightly	 between C and C++, as
	       well as between ISO C90 and C99,	 etc.	This  option  has  two
	       suboptions,		-fsanitize=shift-base		   and
	       -fsanitize=shift-exponent.

	   -fsanitize=shift-exponent
	       This option enables checking that  the  second  argument	 of  a
	       shift  operation	 is  not  negative  and	 is  smaller  than the
	       precision of the	promoted first argument.

	   -fsanitize=shift-base
	       If the second argument of a shift operation  is	within	range,
	       check  that  the	 result	of a shift operation is	not undefined.
	       Note that what exactly is considered undefined differs slightly
	       between C and C++, as well as between ISO C90 and C99, etc.

	   -fsanitize=integer-divide-by-zero
	       Detect integer division by zero	as  well  as  "INT_MIN	/  -1"
	       division.

	   -fsanitize=unreachable
	       With	this	 option,     the     compiler	  turns	   the
	       "__builtin_unreachable" call into a  diagnostics	 message  call
	       instead.	  When	reaching the "__builtin_unreachable" call, the
	       behavior	is undefined.

	   -fsanitize=vla-bound
	       This option instructs the compiler to check that	the size of  a
	       variable	length array is	positive.

	   -fsanitize=null
	       This   option  enables  pointer	checking.   Particularly,  the
	       application built with this option  turned  on  will  issue  an
	       error  message  when it tries to	dereference a NULL pointer, or
	       if a reference (possibly	an rvalue reference)  is  bound	 to  a
	       NULL pointer, or	if a method is invoked on an object pointed by
	       a NULL pointer.

	   -fsanitize=return
	       This  option enables return statement checking.	Programs built
	       with this option	turned on will issue an	error message when the
	       end  of	a  non-void  function  is  reached  without   actually
	       returning a value.  This	option works in	C++ only.

	   -fsanitize=signed-integer-overflow
	       This option enables signed integer overflow checking.  We check
	       that the	result of "+", "*", and	both unary and binary "-" does
	       not   overflow	in  the	 signed	 arithmetics.	Note,  integer
	       promotion rules must be	taken  into  account.	That  is,  the
	       following is not	an overflow:

		       signed char a = SCHAR_MAX;
		       a++;

	   -fsanitize=bounds
	       This  option  enables instrumentation of	array bounds.  Various
	       out of bounds accesses are detected.  Flexible  array  members,
	       flexible	  array	  member-like	arrays,	 and  initializers  of
	       variables with static storage are not instrumented.

	   -fsanitize=bounds-strict
	       This option enables strict  instrumentation  of	array  bounds.
	       Most  out  of  bounds accesses are detected, including flexible
	       array  members	and   flexible	 array	 member-like   arrays.
	       Initializers   of   variables   with  static  storage  are  not
	       instrumented.

	   -fsanitize=alignment
	       This option enables checking of alignment of pointers when they
	       are  dereferenced,  or	when   a   reference   is   bound   to
	       insufficiently  aligned target, or when a method	or constructor
	       is invoked on insufficiently aligned object.

	   -fsanitize=object-size
	       This option enables instrumentation of memory references	 using
	       the  "__builtin_object_size"  function.	 Various out of	bounds
	       pointer accesses	are detected.

	   -fsanitize=float-divide-by-zero
	       Detect floating-point division by zero.	Unlike	other  similar
	       options,	 -fsanitize=float-divide-by-zero  is  not  enabled  by
	       -fsanitize=undefined, since floating-point division by zero can
	       be a legitimate way of obtaining	infinities and NaNs.

	   -fsanitize=float-cast-overflow
	       This option enables floating-point type to  integer  conversion
	       checking.   We check that the result of the conversion does not
	       overflow.       Unlike	    other	similar	      options,
	       -fsanitize=float-cast-overflow	  is	 not	 enabled    by
	       -fsanitize=undefined.  This option  does	 not  work  well  with
	       "FE_INVALID" exceptions enabled.

	   -fsanitize=nonnull-attribute
	       This  option enables instrumentation of calls, checking whether
	       null values are not passed to arguments marked as  requiring  a
	       non-null	value by the "nonnull" function	attribute.

	   -fsanitize=returns-nonnull-attribute
	       This  option  enables  instrumentation  of return statements in
	       functions marked	with "returns_nonnull" function	attribute,  to
	       detect returning	of null	values from such functions.

	   -fsanitize=bool
	       This  option  enables instrumentation of	loads from bool.  If a
	       value other than	0/1 is loaded, a run-time error	is issued.

	   -fsanitize=enum
	       This option enables instrumentation of loads from an enum type.
	       If a value outside the range of values for  the	enum  type  is
	       loaded, a run-time error	is issued.

	   -fsanitize=vptr
	       This  option  enables  instrumentation  of  C++ member function
	       calls, member accesses and some conversions between pointers to
	       base and	derived	classes, to verify the referenced  object  has
	       the correct dynamic type.

	   -fsanitize=pointer-overflow
	       This option enables instrumentation of pointer arithmetics.  If
	       the pointer arithmetics overflows, a run-time error is issued.

	   -fsanitize=builtin
	       This  option  enables  instrumentation of arguments to selected
	       builtin functions.  If an  invalid  value  is  passed  to  such
	       arguments,  a  run-time error is	issued.	 E.g. passing 0	as the
	       argument	 to   "__builtin_ctz"	or   "__builtin_clz"   invokes
	       undefined behavior and is diagnosed by this option.

	   While  -ftrapv  causes  traps  for  signed overflows	to be emitted,
	   -fsanitize=undefined	gives a	diagnostic  message.   This  currently
	   works only for the C	family of languages.

       -fno-sanitize=all
	   This	  option   disables   all   previously	 enabled   sanitizers.
	   -fsanitize=all is not allowed, as some sanitizers  cannot  be  used
	   together.

       -fasan-shadow-offset=number
	   This	  option   forces   GCC	  to   use  custom  shadow  offset  in
	   AddressSanitizer checks.   It  is  useful  for  experimenting  with
	   different shadow memory layouts in Kernel AddressSanitizer.

       -fsanitize-sections=s1,s2,...
	   Sanitize  global  variables	in selected user-defined sections.  si
	   may contain wildcards.

       -fsanitize-recover[=opts]
	   -fsanitize-recover= controls	error  recovery	 mode  for  sanitizers
	   mentioned  in  comma-separated  list	of opts.  Enabling this	option
	   for a sanitizer component causes it to attempt to continue  running
	   the	program	 as if no error	happened.  This	means multiple runtime
	   errors can be reported in a single program run, and the  exit  code
	   of  the  program  may  indicate  success even when errors have been
	   reported.  The -fno-sanitize-recover= option	can be used  to	 alter
	   this	 behavior:  only  the  first  detected	error  is reported and
	   program then	exits with a non-zero exit code.

	   Currently this feature only works for -fsanitize=undefined (and its
	   suboptions	  except      for      -fsanitize=unreachable	   and
	   -fsanitize=return),		       -fsanitize=float-cast-overflow,
	   -fsanitize=float-divide-by-zero,	     -fsanitize=bounds-strict,
	   -fsanitize=kernel-address   and   -fsanitize=address.    For	 these
	   sanitizers  error  recovery	is  turned  on	by   default,	except
	   -fsanitize=address,	 for   which  this  feature  is	 experimental.
	   -fsanitize-recover=all  and	 -fno-sanitize-recover=all   is	  also
	   accepted,  the  former  enables  recovery  for  all sanitizers that
	   support it, the latter disables recovery for	 all  sanitizers  that
	   support it.

	   Even	if a recovery mode is turned on	the compiler side, it needs to
	   be also enabled on the runtime library side,	otherwise the failures
	   are still fatal.  The runtime library defaults to "halt_on_error=0"
	   for	ThreadSanitizer	 and UndefinedBehaviorSanitizer, while default
	   value  for  AddressSanitizer	 is  "halt_on_error=1".	 This  can  be
	   overridden	through	  setting  the	"halt_on_error"	 flag  in  the
	   corresponding environment variable.

	   Syntax without an explicit opts parameter  is  deprecated.	It  is
	   equivalent to specifying an opts list of:

		   undefined,float-cast-overflow,float-divide-by-zero,bounds-strict

       -fsanitize-address-use-after-scope
	   Enable  sanitization	 of  local variables to	detect use-after-scope
	   bugs.  The option sets -fstack-reuse	to none.

       -fsanitize-undefined-trap-on-error
	   The	 -fsanitize-undefined-trap-on-error   option   instructs   the
	   compiler to report undefined	behavior using "__builtin_trap"	rather
	   than	 a  "libubsan" library routine.	 The advantage of this is that
	   the "libubsan" library is not needed	and is not linked in, so  this
	   is usable even in freestanding environments.

       -fsanitize-coverage=trace-pc
	   Enable  coverage-guided  fuzzing  code  instrumentation.  Inserts a
	   call	to "__sanitizer_cov_trace_pc" into every basic block.

       -fsanitize-coverage=trace-cmp
	   Enable dataflow guided fuzzing  code	 instrumentation.   Inserts  a
	   call	to "__sanitizer_cov_trace_cmp1", "__sanitizer_cov_trace_cmp2",
	   "__sanitizer_cov_trace_cmp4"	 or  "__sanitizer_cov_trace_cmp8"  for
	   integral   comparison    with    both    operands	variable    or
	   "__sanitizer_cov_trace_const_cmp1",
	   "__sanitizer_cov_trace_const_cmp2",
	   "__sanitizer_cov_trace_const_cmp4"				    or
	   "__sanitizer_cov_trace_const_cmp8" for integral comparison with one
	   operand	 constant,	 "__sanitizer_cov_trace_cmpf"	    or
	   "__sanitizer_cov_trace_cmpd"	 for  float  or	double comparisons and
	   "__sanitizer_cov_trace_switch" for switch statements.

       -fcf-protection=[full|branch|return|none|check]
	   Enable code instrumentation of control-flow transfers  to  increase
	   program  security by	checking that target addresses of control-flow
	   transfer instructions (such as  indirect  function  call,  function
	   return, indirect jump) are valid.  This prevents diverting the flow
	   of  control	to  an unexpected target.  This	is intended to protect
	   against such	threats	 as  Return-oriented  Programming  (ROP),  and
	   similarly call/jmp-oriented programming (COP/JOP).

	   The	value  "branch"	 tells	the  compiler to implement checking of
	   validity of control-flow transfer at	the point of  indirect	branch
	   instructions,  i.e.	call/jmp  instructions.	  The  value  "return"
	   implements checking of validity at the point	of  returning  from  a
	   function.   The  value  "full"  is  an  alias  for  specifying both
	   "branch" and	"return". The value "none" turns off instrumentation.

	   The value "check"  is  used	for  the  final	 link  with  link-time
	   optimization	 (LTO).	  An  error  is	issued if LTO object files are
	   compiled with different -fcf-protection values.  The	value  "check"
	   is ignored at the compile time.

	   The	macro  "__CET__" is defined when -fcf-protection is used.  The
	   first bit of	"__CET__" is set to 1 for the value "branch"  and  the
	   second bit of "__CET__" is set to 1 for the "return".

	   You	can  also  use	the  "nocf_check"  attribute to	identify which
	   functions and calls should be skipped from instrumentation.

	   Currently the x86 GNU/Linux target provides an implementation based
	   on Intel Control-flow Enforcement Technology	(CET) which works  for
	   i686	processor or newer.

       -fstack-protector
	   Emit	 extra	code  to  check	 for  buffer  overflows, such as stack
	   smashing attacks.  This is done  by	adding	a  guard  variable  to
	   functions  with  vulnerable	objects.  This includes	functions that
	   call	"alloca", and functions	with buffers larger than or equal to 8
	   bytes.  The guards are initialized when a function is  entered  and
	   then	 checked  when the function exits.  If a guard check fails, an
	   error message is printed and	the  program  exits.   Only  variables
	   that	 are actually allocated	on the stack are considered, optimized
	   away	variables or variables allocated in registers don't count.

       -fstack-protector-all
	   Like	-fstack-protector except that all functions are	protected.

       -fstack-protector-strong
	   Like	-fstack-protector but  includes	 additional  functions	to  be
	   protected  ---  those  that	have  local array definitions, or have
	   references to local	frame  addresses.   Only  variables  that  are
	   actually  allocated	on  the	 stack	are considered,	optimized away
	   variables or	variables allocated in registers don't count.

       -fstack-protector-explicit
	   Like	-fstack-protector but only protects those functions which have
	   the "stack_protect" attribute.

       -fstack-check
	   Generate code to verify that	you do not go beyond the  boundary  of
	   the	stack.	 You should specify this flag if you are running in an
	   environment with multiple threads, but  you	only  rarely  need  to
	   specify it in a single-threaded environment since stack overflow is
	   automatically  detected  on nearly all systems if there is only one
	   stack.

	   Note	that this switch does not actually cause checking to be	 done;
	   the	operating  system  or  the language runtime must do that.  The
	   switch causes generation of code to ensure that they	see the	 stack
	   being extended.

	   You	can  additionally  specify  a  string  parameter:  no means no
	   checking, generic  means  force  the	 use  of  old-style  checking,
	   specific  means  use	 the best checking method and is equivalent to
	   bare	-fstack-check.

	   Old-style checking is a generic mechanism that requires no specific
	   target support  in  the  compiler  but  comes  with	the  following
	   drawbacks:

	   1.  Modified	allocation strategy for	large objects: they are	always
	       allocated  dynamically if their size exceeds a fixed threshold.
	       Note this may change the	semantics of some code.

	   2.  Fixed limit on the size of the static frame of functions:  when
	       it  is  topped  by a particular function, stack checking	is not
	       reliable	and a warning is issued	by the compiler.

	   3.  Inefficiency: because of	both the modified allocation  strategy
	       and the generic implementation, code performance	is hampered.

	   Note	 that old-style	stack checking is also the fallback method for
	   specific if no target support has been added	in the compiler.

	   -fstack-check= is designed  for  Ada's  needs  to  detect  infinite
	   recursion  and  stack  overflows.   specific	is an excellent	choice
	   when	compiling Ada code.  It	is not generally sufficient to protect
	   against stack-clash attacks.	 To protect  against  those  you  want
	   -fstack-clash-protection.

       -fstack-clash-protection
	   Generate  code  to  prevent	stack  clash style attacks.  When this
	   option is enabled, the compiler will	 only  allocate	 one  page  of
	   stack  space	 at a time and each page is accessed immediately after
	   allocation.	Thus, it prevents allocations from  jumping  over  any
	   stack guard page provided by	the operating system.

	   Most	targets	do not fully support stack clash protection.  However,
	   on  those  targets  -fstack-clash-protection	 will  protect dynamic
	   stack  allocations.	 -fstack-clash-protection  may	also   provide
	   limited  protection	for  static  stack  allocations	 if the	target
	   supports -fstack-check=specific.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
	   Generate code to ensure that	the  stack  does  not  grow  beyond  a
	   certain  value,  either the value of	a register or the address of a
	   symbol.  If a larger	stack is required, a signal is raised  at  run
	   time.   For	most  targets,	the  signal is raised before the stack
	   overruns the	boundary, so  it  is  possible	to  catch  the	signal
	   without taking special precautions.

	   For	instance,  if  the stack starts	at absolute address 0x80000000
	   and	  grows	   downwards,	 you	 can	 use	 the	 flags
	   -fstack-limit-symbol=__stack_limit				   and
	   -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack  limit  of
	   128KB.  Note	that this may only work	with the GNU linker.

	   You	can  locally  override	stack  limit  checking	by  using  the
	   "no_stack_limit" function attribute.

       -fsplit-stack
	   Generate code to automatically split	the stack before it overflows.
	   The resulting program has a	discontiguous  stack  which  can  only
	   overflow  if	 the  program  is  unable to allocate any more memory.
	   This	is most	useful when running threaded programs,	as  it	is  no
	   longer  necessary  to  calculate  a good stack size to use for each
	   thread.  This is currently only implemented	for  the  x86  targets
	   running GNU/Linux.

	   When	 code  compiled	with -fsplit-stack calls code compiled without
	   -fsplit-stack, there	may not	be much	stack space available for  the
	   latter code to run.	If compiling all code, including library code,
	   with	 -fsplit-stack	is  not	 an option, then the linker can	fix up
	   these calls so that the code	compiled without -fsplit-stack	always
	   has	a  large  stack.   Support for this is implemented in the gold
	   linker in GNU binutils release 2.21 and later.

       -fvtable-verify=[std|preinit|none]
	   This	option is only available when compiling	C++ code.  It turns on
	   (or off, if using -fvtable-verify=none) the security	 feature  that
	   verifies  at	 run  time,  for  every	 virtual call, that the	vtable
	   pointer through which the call is made is valid for the type	of the
	   object, and has not been corrupted or overwritten.  If  an  invalid
	   vtable  pointer  is	detected at run	time, an error is reported and
	   execution of	the program is immediately halted.

	   This	option causes run-time data structures to be built at  program
	   startup,  which  are	 used  for verifying the vtable	pointers.  The
	   options std and preinit control  the	 timing	 of  when  these  data
	   structures  are built.  In both cases the data structures are built
	   before execution reaches "main".  Using -fvtable-verify=std	causes
	   the	data  structures  to be	built after shared libraries have been
	   loaded and initialized.  -fvtable-verify=preinit causes them	to  be
	   built before	shared libraries have been loaded and initialized.

	   If  this  option  appears  multiple	times in the command line with
	   different values specified, none takes highest priority  over  both
	   std and preinit; preinit takes priority over	std.

       -fvtv-debug
	   When	   used	   in	 conjunction   with   -fvtable-verify=std   or
	   -fvtable-verify=preinit,  causes  debug  versions  of  the  runtime
	   functions  for  the vtable verification feature to be called.  This
	   flag	also causes the	compiler to log	information about which	vtable
	   pointers it finds for each class.  This information is written to a
	   file	named vtv_set_ptr_data.log  in	the  directory	named  by  the
	   environment variable	VTV_LOGS_DIR if	that is	defined	or the current
	   working directory otherwise.

	   Note:   This	 feature  appends  data	to the log file. If you	want a
	   fresh log file, be sure to delete any existing one.

       -fvtv-counts
	   This	 is  a	debugging  flag.   When	 used  in   conjunction	  with
	   -fvtable-verify=std	or  -fvtable-verify=preinit,  this  causes the
	   compiler to keep track of the total	number	of  virtual  calls  it
	   encounters  and  the	 number	 of verifications it inserts.  It also
	   counts the number of	calls to certain  run-time  library  functions
	   that	 it  inserts  and  logs	 this information for each compilation
	   unit.  The  compiler	 writes	 this  information  to	a  file	 named
	   vtv_count_data.log  in  the	directory  named  by  the  environment
	   variable VTV_LOGS_DIR if that is defined  or	 the  current  working
	   directory otherwise.	 It also counts	the size of the	vtable pointer
	   sets	  for	each   class,	and   writes   this   information   to
	   vtv_class_set_sizes.log in the same directory.

	   Note:  This feature appends data to the log files.	To  get	 fresh
	   log files, be sure to delete	any existing ones.

       -finstrument-functions
	   Generate  instrumentation  calls  for  entry	and exit to functions.
	   Just	after function	entry  and  just  before  function  exit,  the
	   following  profiling	 functions  are	called with the	address	of the
	   current  function  and  its	call  site.    (On   some   platforms,
	   "__builtin_return_address"	does   not  work  beyond  the  current
	   function, so	the call site information may not be available to  the
	   profiling functions otherwise.)

		   void	__cyg_profile_func_enter (void *this_fn,
						  void *call_site);
		   void	__cyg_profile_func_exit	 (void *this_fn,
						  void *call_site);

	   The	first  argument	 is  the  address  of the start	of the current
	   function, which may be looked up exactly in the symbol table.

	   This	instrumentation	is also	done for functions expanded inline  in
	   other functions.  The profiling calls indicate where, conceptually,
	   the	inline	function  is  entered  and  exited.   This  means that
	   addressable versions	of such	functions must be available.   If  all
	   your	 uses  of  a  function	are  expanded inline, this may mean an
	   additional expansion	of code	size.  If you use "extern  inline"  in
	   your	 C  code,  an  addressable  version  of	such functions must be
	   provided.  (This is normally	the case anyway, but if	you get	 lucky
	   and	the  optimizer	always expands the functions inline, you might
	   have	gotten away without providing static copies.)

	   A function may be given the attribute "no_instrument_function",  in
	   which case this instrumentation is not done.	 This can be used, for
	   example,  for  the  profiling functions listed above, high-priority
	   interrupt routines, and any	functions  from	 which	the  profiling
	   functions  cannot safely be called (perhaps signal handlers,	if the
	   profiling routines generate output or allocate memory).

       -finstrument-functions-exclude-file-list=file,file,...
	   Set the list	of functions that are  excluded	 from  instrumentation
	   (see	 the description of -finstrument-functions).  If the file that
	   contains a function definition matches with one of file, then  that
	   function  is	not instrumented.  The match is	done on	substrings: if
	   the file  parameter	is  a  substring  of  the  file	 name,	it  is
	   considered to be a match.

	   For example:

		   -finstrument-functions-exclude-file-list=/bits/stl,include/sys

	   excludes  any  inline  function  defined  in	 files whose pathnames
	   contain /bits/stl or	include/sys.

	   If, for some	reason,	you want to include letter , in	 one  of  sym,
	   write		 ,.		   For		      example,
	   -finstrument-functions-exclude-file-list=',,tmp' (note  the	single
	   quote surrounding the option).

       -finstrument-functions-exclude-function-list=sym,sym,...
	   This	 is  similar  to -finstrument-functions-exclude-file-list, but
	   this	option sets the	list of	function names	to  be	excluded  from
	   instrumentation.   The  function  name  to  be matched is its user-
	   visible name, such as "vector<int> blah(const vector<int> &)",  not
	   the internal	mangled	name (e.g., "_Z4blahRSt6vectorIiSaIiEE").  The
	   match is done on substrings:	if the sym parameter is	a substring of
	   the function	name, it is considered to be a match.  For C99 and C++
	   extended identifiers, the function name must	be given in UTF-8, not
	   using universal character names.

       -fpatchable-function-entry=N[,M]
	   Generate  N	NOPs right at the beginning of each function, with the
	   function entry point	before the Mth	NOP.   If  M  is  omitted,  it
	   defaults  to	 0 so the function entry points	to the address just at
	   the first NOP.  The NOP instructions	reserve	extra space which  can
	   be  used  to	 patch	in  any	 desired  instrumentation at run time,
	   provided that the code segment is writable.	The amount of space is
	   controllable	indirectly via the number of NOPs; the NOP instruction
	   used	corresponds to the instruction emitted	by  the	 internal  GCC
	   back-end interface "gen_nop".  This behavior	is target-specific and
	   may	 also	depend	 on  the  architecture	variant	 and/or	 other
	   compilation options.

	   For run-time	identification,	the starting addresses of these	areas,
	   which correspond to their respective	function entries minus M,  are
	   additionally	  collected   in   the	"__patchable_function_entries"
	   section of the resulting binary.

	   Note	that the value	of  "__attribute__  ((patchable_function_entry
	   (N,M)))"	takes	  precedence	over	command-line	option
	   -fpatchable-function-entry=N,M.  This can be	used to	 increase  the
	   area	 size  or  to  remove  it completely on	a single function.  If
	   "N=0", no pad location is recorded.

	   The NOP instructions	are inserted at---and maybe before,  depending
	   on M---the function entry address, even before the prologue.

	   The maximum value of	N and M	is 65535.

   Options Controlling the Preprocessor
       These options control the C preprocessor, which is run on each C	source
       file before actual compilation.

       If  you	use the	-E option, nothing is done except preprocessing.  Some
       of these	options	make sense only	together with -E  because  they	 cause
       the preprocessor	output to be unsuitable	for actual compilation.

       In  addition  to	the options listed here, there are a number of options
       to control search paths	for  include  files  documented	 in  Directory
       Options.	  Options  to  control	preprocessor diagnostics are listed in
       Warning Options.

       -D name
	   Predefine name as a macro, with definition 1.

       -D name=definition
	   The contents	of definition are tokenized and	processed as  if  they
	   appeared during translation phase three in a	#define	directive.  In
	   particular,	 the  definition  is  truncated	 by  embedded  newline
	   characters.

	   If you are invoking the preprocessor	from  a	 shell	or  shell-like
	   program  you	 may need to use the shell's quoting syntax to protect
	   characters such as spaces that have a meaning in the	shell syntax.

	   If you wish to define a function-like macro on  the	command	 line,
	   write  its  argument	 list  with surrounding	parentheses before the
	   equals sign (if any).  Parentheses are meaningful to	 most  shells,
	   so	you   should   quote   the   option.	With   sh   and	  csh,
	   -D'name(args...)=definition'	works.

	   -D and -U options are processed in the order	they are given on  the
	   command  line.   All	 -imacros  file	 and -include file options are
	   processed after all -D and -U options.

       -U name
	   Cancel any previous definition of name, either built	in or provided
	   with	a -D option.

       -include	file
	   Process file	as if "#include	"file""	appeared as the	first line  of
	   the primary source file.  However, the first	directory searched for
	   file	 is  the  preprocessor's  working  directory  instead  of  the
	   directory containing	the main source	file.  If not found there,  it
	   is  searched	 for  in  the remainder	of the "#include "...""	search
	   chain as normal.

	   If multiple -include	options	are given, the files are  included  in
	   the order they appear on the	command	line.

       -imacros	file
	   Exactly  like -include, except that any output produced by scanning
	   file	is thrown away.	  Macros  it  defines  remain  defined.	  This
	   allows  you	to  acquire  all the macros from a header without also
	   processing its declarations.

	   All files specified by -imacros  are	 processed  before  all	 files
	   specified by	-include.

       -undef
	   Do  not  predefine any system-specific or GCC-specific macros.  The
	   standard predefined macros remain defined.

       -pthread
	   Define additional macros  required  for  using  the	POSIX  threads
	   library.    You  should  use	 this  option  consistently  for  both
	   compilation and linking.  This option  is  supported	 on  GNU/Linux
	   targets,  most  other  Unix derivatives, and	also on	x86 Cygwin and
	   MinGW targets.

       -M  Instead of outputting the result of preprocessing,  output  a  rule
	   suitable  for  make	describing the dependencies of the main	source
	   file.  The preprocessor outputs one make rule containing the	object
	   file	name for that source file, a colon, and	the names of  all  the
	   included  files,  including	those coming from -include or -imacros
	   command-line	options.

	   Unless specified explicitly (with -MT or -MQ), the object file name
	   consists of the name	of the source file with	 any  suffix  replaced
	   with	 object	 file  suffix  and  with  any  leading directory parts
	   removed.  If	there are many included	files then the rule  is	 split
	   into	several	lines using \-newline.	The rule has no	commands.

	   This	option does not	suppress the preprocessor's debug output, such
	   as  -dM.   To  avoid	 mixing	 such debug output with	the dependency
	   rules you should explicitly specify the dependency output file with
	   -MF,	or  use	 an  environment  variable  like  DEPENDENCIES_OUTPUT.
	   Debug output	is still sent to the regular output stream as normal.

	   Passing  -M	to the driver implies -E, and suppresses warnings with
	   an implicit -w.

       -MM Like	-M but do not mention header files that	are  found  in	system
	   header directories, nor header files	that are included, directly or
	   indirectly, from such a header.

	   This	 implies that the choice of angle brackets or double quotes in
	   an #include directive does not in  itself  determine	 whether  that
	   header appears in -MM dependency output.

       -MF file
	   When	  used	with  -M  or  -MM,  specifies  a  file	to  write  the
	   dependencies	to.  If	no -MF switch is given the preprocessor	 sends
	   the rules to	the same place it would	send preprocessed output.

	   When	 used  with  the driver	options	-MD or -MMD, -MF overrides the
	   default dependency output file.

	   If file is -, then the dependencies are written to stdout.

       -MG In conjunction with an option  such	as  -M	requesting  dependency
	   generation,	-MG  assumes  missing header files are generated files
	   and adds them to the	dependency list	without	raising	an error.  The
	   dependency filename is taken	directly from the "#include" directive
	   without prepending any  path.   -MG	also  suppresses  preprocessed
	   output, as a	missing	header file renders this useless.

	   This	feature	is used	in automatic updating of makefiles.

       -Mno-modules
	   Disable dependency generation for compiled module interfaces.

       -MP This	option instructs CPP to	add a phony target for each dependency
	   other than the main file, causing each to depend on nothing.	 These
	   dummy  rules	 work  around  errors  make gives if you remove	header
	   files without updating the Makefile to match.

	   This	is typical output:

		   test.o: test.c test.h

		   test.h:

       -MT target
	   Change the target of	the rule emitted by dependency generation.  By
	   default CPP takes the name of the  main  input  file,  deletes  any
	   directory  components  and  any file	suffix such as .c, and appends
	   the platform's usual	object suffix.	The result is the target.

	   An -MT option sets the target to be exactly the string you specify.
	   If you want multiple	targets, you can  specify  them	 as  a	single
	   argument to -MT, or use multiple -MT	options.

	   For example,	-MT '$(objpfx)foo.o' might give

		   $(objpfx)foo.o: foo.c

       -MQ target
	   Same	 as  -MT,  but	it  quotes any characters which	are special to
	   Make.  -MQ '$(objpfx)foo.o' gives

		   $$(objpfx)foo.o: foo.c

	   The default target is automatically quoted, as  if  it  were	 given
	   with	-MQ.

       -MD -MD	is  equivalent	to -M -MF file,	except that -E is not implied.
	   The driver determines file based on whether an -o option is	given.
	   If  it  is,	the  driver uses its argument but with a suffix	of .d,
	   otherwise it	 takes	the  name  of  the  input  file,  removes  any
	   directory components	and suffix, and	applies	a .d suffix.

	   If  -MD is used in conjunction with -E, any -o switch is understood
	   to specify the dependency output file, but if used without -E, each
	   -o is understood to specify a target	object file.

	   Since -E is not implied, -MD	can be used to generate	 a  dependency
	   output file as a side effect	of the compilation process.

       -MMD
	   Like	 -MD  except mention only user header files, not system	header
	   files.

       -fpreprocessed
	   Indicate to the preprocessor	that the input file has	 already  been
	   preprocessed.    This   suppresses  things  like  macro  expansion,
	   trigraph conversion,	escaped	newline	splicing,  and	processing  of
	   most	 directives.   The  preprocessor  still	recognizes and removes
	   comments, so	that you can pass a file preprocessed with -C  to  the
	   compiler   without	problems.    In	  this	 mode  the  integrated
	   preprocessor	is little more than a tokenizer	for the	front ends.

	   -fpreprocessed is implicit  if  the	input  file  has  one  of  the
	   extensions  .i, .ii or .mi.	These are the extensions that GCC uses
	   for preprocessed files created by -save-temps.

       -fdirectives-only
	   When	preprocessing, handle directives, but do not expand macros.

	   The option's	behavior depends on the	-E and -fpreprocessed options.

	   With	-E, preprocessing is limited to	 the  handling	of  directives
	   such	 as  "#define",	 "#ifdef",  and	 "#error".  Other preprocessor
	   operations, such as macro expansion and trigraph conversion are not
	   performed.  In addition, the	-dD option is implicitly enabled.

	   With	-fpreprocessed,	predefinition of command line and most builtin
	   macros  is  disabled.   Macros  such	 as  "__LINE__",   which   are
	   contextually	  dependent,   are  handled  normally.	 This  enables
	   compilation	 of   files   previously   preprocessed	   with	   "-E
	   -fdirectives-only".

	   With	 both -E and -fpreprocessed, the rules for -fpreprocessed take
	   precedence.	This enables full preprocessing	 of  files  previously
	   preprocessed	with "-E -fdirectives-only".

       -fdollars-in-identifiers
	   Accept $ in identifiers.

       -fextended-identifiers
	   Accept   universal  character  names	 and  extended	characters  in
	   identifiers.	 This option is	enabled	by default for C99 (and	 later
	   C standard versions)	and C++.

       -fno-canonical-system-headers
	   When	 preprocessing,	 do  not  shorten  system  header  paths  with
	   canonicalization.

       -fmax-include-depth=depth
	   Set the maximum depth of the	nested #include. The default is	200.

       -ftabstop=width
	   Set the distance between tab	stops.	This  helps  the  preprocessor
	   report  correct  column numbers in warnings or errors, even if tabs
	   appear on the line.	If the value is	less than 1  or	 greater  than
	   100,	the option is ignored.	The default is 8.

       -ftrack-macro-expansion[=level]
	   Track  locations of tokens across macro expansions. This allows the
	   compiler to emit diagnostic about the current macro expansion stack
	   when	a compilation error occurs in a	macro  expansion.  Using  this
	   option makes	the preprocessor and the compiler consume more memory.
	   The level parameter can be used to choose the level of precision of
	   token  location  tracking thus decreasing the memory	consumption if
	   necessary. Value 0 of  level	 de-activates  this  option.  Value  1
	   tracks  tokens locations in a degraded mode for the sake of minimal
	   memory overhead.  In	 this  mode  all  tokens  resulting  from  the
	   expansion  of  an  argument	of a function-like macro have the same
	   location. Value 2 tracks tokens locations completely. This value is
	   the most memory hungry.  When this option is	given no argument, the
	   default parameter value is 2.

	   Note	that "-ftrack-macro-expansion=2" is activated by default.

       -fmacro-prefix-map=old=new
	   When	preprocessing files residing  in  directory  old,  expand  the
	   "__FILE__"  and  "__BASE_FILE__"  macros as if the files resided in
	   directory new instead.  This	can be used to change an absolute path
	   to a	relative path by using . for new  which	 can  result  in  more
	   reproducible	 builds	 that  are  location independent.  This	option
	   also	 affects  "__builtin_FILE()"  during  compilation.   See  also
	   -ffile-prefix-map.

       -fexec-charset=charset
	   Set	the  execution	character  set,	 used for string and character
	   constants.  The default is UTF-8.   charset	can  be	 any  encoding
	   supported by	the system's "iconv" library routine.

       -fwide-exec-charset=charset
	   Set	the  wide  execution  character	 set, used for wide string and
	   character constants.	 The default is	 one  of  UTF-32BE,  UTF-32LE,
	   UTF-16BE,  or  UTF-16LE,  whichever	corresponds  to	 the  width of
	   "wchar_t" and the big-endian	or little-endian byte order being used
	   for code generation.	 As with -fexec-charset, charset  can  be  any
	   encoding   supported	 by  the  system's  "iconv"  library  routine;
	   however, you	will have problems with	 encodings  that  do  not  fit
	   exactly in "wchar_t".

       -finput-charset=charset
	   Set	the  input  character  set,  used  for	translation  from  the
	   character set of the	input file to the source character set used by
	   GCC.	 If the	locale does  not  specify,  or	GCC  cannot  get  this
	   information	from  the  locale,  the	default	is UTF-8.  This	can be
	   overridden by  either  the  locale  or  this	 command-line  option.
	   Currently  the  command-line	 option	 takes precedence if there's a
	   conflict.  charset can be any encoding supported  by	 the  system's
	   "iconv" library routine.

       -fpch-deps
	   When	 using	precompiled  headers, this flag	causes the dependency-
	   output flags	to also	list the files from the	 precompiled  header's
	   dependencies.   If  not  specified, only the	precompiled header are
	   listed and not the files that were used to create it, because those
	   files are not consulted when	a precompiled header is	used.

       -fpch-preprocess
	   This	option allows use of a precompiled header  together  with  -E.
	   It	inserts	 a  special  "#pragma",	 "#pragma  GCC	pch_preprocess
	   "filename"" in the output to	mark the place where  the  precompiled
	   header was found, and its filename.	When -fpreprocessed is in use,
	   GCC recognizes this "#pragma" and loads the PCH.

	   This	 option	 is off	by default, because the	resulting preprocessed
	   output is only really suitable as input to GCC.  It is switched  on
	   by -save-temps.

	   You	should	not  write  this "#pragma" in your own code, but it is
	   safe	to edit	the filename  if  the  PCH  file  is  available	 in  a
	   different  location.	  The  filename	 may  be absolute or it	may be
	   relative to GCC's current directory.

       -fworking-directory
	   Enable generation of	linemarkers in the  preprocessor  output  that
	   let	the compiler know the current working directory	at the time of
	   preprocessing.  When	 this  option  is  enabled,  the  preprocessor
	   emits,  after  the initial linemarker, a second linemarker with the
	   current working directory followed by two slashes.  GCC  uses  this
	   directory,  when  it's  present  in	the preprocessed input,	as the
	   directory  emitted  as  the	current	 working  directory  in	  some
	   debugging  information  formats.  This option is implicitly enabled
	   if debugging	information is enabled,	but this can be	inhibited with
	   the negated form -fno-working-directory.  If	the -P flag is present
	   in the command line,	this option has	no effect,  since  no  "#line"
	   directives are emitted whatsoever.

       -A predicate=answer
	   Make	 an  assertion with the	predicate predicate and	answer answer.
	   This	form is	preferred to  the  older  form	-A  predicate(answer),
	   which  is  still  supported,	 because it does not use shell special
	   characters.

       -A -predicate=answer
	   Cancel an assertion with the	predicate predicate and	answer answer.

       -C  Do not discard comments.  All comments are passed  through  to  the
	   output file,	except for comments in processed directives, which are
	   deleted along with the directive.

	   You	should	be  prepared for side effects when using -C; it	causes
	   the preprocessor to treat comments as tokens	in  their  own	right.
	   For	example,  comments  appearing  at the start of what would be a
	   directive line have	the  effect  of	 turning  that	line  into  an
	   ordinary  source  line,  since  the	first  token on	the line is no
	   longer a #.

       -CC Do not discard comments, including during macro expansion.  This is
	   like	-C, except that	comments  contained  within  macros  are  also
	   passed through to the output	file where the macro is	expanded.

	   In  addition	 to  the side effects of the -C	option,	the -CC	option
	   causes all C++-style	comments inside	a macro	 to  be	 converted  to
	   C-style  comments.  This is to prevent later	use of that macro from
	   inadvertently commenting out	the remainder of the source line.

	   The -CC option is generally used to support lint comments.

       -P  Inhibit  generation	of  linemarkers	 in  the   output   from   the
	   preprocessor.   This	 might be useful when running the preprocessor
	   on something	that is	not C code, and	will  be  sent	to  a  program
	   which might be confused by the linemarkers.

       -traditional
       -traditional-cpp
	   Try	to  imitate  the  behavior of pre-standard C preprocessors, as
	   opposed to ISO  C  preprocessors.   See  the	 GNU  CPP  manual  for
	   details.

	   Note	 that GCC does not otherwise attempt to	emulate	a pre-standard
	   C compiler, and these  options  are	only  supported	 with  the  -E
	   switch, or when invoking CPP	explicitly.

       -trigraphs
	   Support  ISO	C trigraphs.  These are	three-character	sequences, all
	   starting with ??, that are defined by ISO C	to  stand  for	single
	   characters.	 For  example,	??/  stands  for  \,  so  '??/n'  is a
	   character constant for a newline.

	   The nine trigraphs and their	replacements are

		   Trigraph:	   ??(	??)  ??<  ??>  ??=  ??/	 ??'  ??!  ??-
		   Replacement:	     [	  ]    {    }	 #    \	   ^	|    ~

	   By default, GCC ignores trigraphs, but in standard-conforming modes
	   it converts them.  See the -std and -ansi options.

       -remap
	   Enable special code to work around file systems which  only	permit
	   very	short file names, such as MS-DOS.

       -H  Print  the  name  of	 each  header  file used, in addition to other
	   normal activities.  Each name is indented to	show how deep  in  the
	   #include  stack  it is.  Precompiled	header files are also printed,
	   even	if they	are found to be	invalid; an invalid precompiled	header
	   file	is printed with	...x and a valid one with ...! .

       -dletters
	   Says	to make	debugging dumps	during	compilation  as	 specified  by
	   letters.   The  flags  documented  here  are	 those relevant	to the
	   preprocessor.   Other  letters  are	interpreted  by	 the  compiler
	   proper, or reserved for future versions of GCC, and so are silently
	   ignored.   If  you  specify	letters	 whose behavior	conflicts, the
	   result is undefined.

	   -dM Instead of the  normal  output,	generate  a  list  of  #define
	       directives  for	all the	macros defined during the execution of
	       the preprocessor, including predefined macros.  This gives  you
	       a  way of finding out what is predefined	in your	version	of the
	       preprocessor.  Assuming you have	no file	foo.h, the command

		       touch foo.h; cpp	-dM foo.h

	       shows all the predefined	macros.

	       If you use -dM without the -E option, -dM is interpreted	 as  a
	       synonym for -fdump-rtl-mach.

	   -dD Like  -dM  except  in  two  respects:  it  does not include the
	       predefined macros, and it outputs both the  #define  directives
	       and  the	 result	 of preprocessing.  Both kinds of output go to
	       the standard output file.

	   -dN Like -dD, but emit only the macro names,	not their expansions.

	   -dI Output  #include	 directives  in	 addition  to  the  result  of
	       preprocessing.

	   -dU Like  -dD  except  that only macros that	are expanded, or whose
	       definedness is tested in	preprocessor directives,  are  output;
	       the  output  is delayed until the use or	test of	the macro; and
	       #undef  directives  are	also  output  for  macros  tested  but
	       undefined at the	time.

       -fdebug-cpp
	   This	 option	 is only useful	for debugging GCC.  When used from CPP
	   or with -E, it dumps	debugging  information	about  location	 maps.
	   Every  token	 in  the output	is preceded by the dump	of the map its
	   location belongs to.

	   When	used from GCC without -E, this option has no effect.

       -Wp,option
	   You can use -Wp,option to  bypass  the  compiler  driver  and  pass
	   option  directly  through  to the preprocessor.  If option contains
	   commas, it is split into multiple options at	the commas.   However,
	   many	 options  are  modified,  translated  or  interpreted  by  the
	   compiler driver before being	passed to the  preprocessor,  and  -Wp
	   forcibly  bypasses this phase.  The preprocessor's direct interface
	   is undocumented and subject to change,  so  whenever	 possible  you
	   should  avoid  using	 -Wp  and  let	the  driver handle the options
	   instead.

       -Xpreprocessor option
	   Pass	option as an option to the preprocessor.  You can use this  to
	   supply  system-specific  preprocessor  options  that	 GCC  does not
	   recognize.

	   If you want to pass an option that takes an argument, you must  use
	   -Xpreprocessor  twice,  once	 for  the  option  and	once  for  the
	   argument.

       -no-integrated-cpp
	   Perform preprocessing as a separate pass  before  compilation.   By
	   default,  GCC performs preprocessing	as an integrated part of input
	   tokenization	 and  parsing.	 If  this  option  is  provided,   the
	   appropriate language	front end (cc1,	cc1plus, or cc1obj for C, C++,
	   and	Objective-C,  respectively) is instead invoked twice, once for
	   preprocessing  only	and  once  for	actual	compilation   of   the
	   preprocessed	 input.	 This option may be useful in conjunction with
	   the -B or -wrapper options to specify an alternate preprocessor  or
	   perform  additional processing of the program source	between	normal
	   preprocessing and compilation.

       -flarge-source-files
	   Adjust GCC to expect	large source files, at the expense  of	slower
	   compilation and higher memory usage.

	   Specifically,  GCC  normally	 tracks	 both  column numbers and line
	   numbers within source files and it normally prints  both  of	 these
	   numbers  in	diagnostics.  However, once it has processed a certain
	   number of source lines, it stops tracking column numbers  and  only
	   tracks  line	 numbers.  This	means that diagnostics for later lines
	   do not include column numbers.  It also  means  that	 options  like
	   -Wmisleading-indentation  cease to work at that point, although the
	   compiler   prints   a    note    if	  this	  happens.     Passing
	   -flarge-source-files	 significantly	increases the number of	source
	   lines that GCC can process before it	stops tracking columns.

   Passing Options to the Assembler
       You can pass options to the assembler.

       -Wa,option
	   Pass	option as an option to	the  assembler.	  If  option  contains
	   commas, it is split into multiple options at	the commas.

       -Xassembler option
	   Pass	 option	 as  an	 option	to the assembler.  You can use this to
	   supply  system-specific  assembler  options	that  GCC   does   not
	   recognize.

	   If  you want	to pass	an option that takes an	argument, you must use
	   -Xassembler twice, once for the option and once for the argument.

   Options for Linking
       These options come into play when the compiler links object files  into
       an executable output file.  They	are meaningless	if the compiler	is not
       doing a link step.

       object-file-name
	   A  file  name  that	does not end in	a special recognized suffix is
	   considered to name an object	file or	library.   (Object  files  are
	   distinguished  from	libraries  by the linker according to the file
	   contents.)  If linking is done, these  object  files	 are  used  as
	   input to the	linker.

       -c
       -S
       -E  If  any  of	these options is used, then the	linker is not run, and
	   object file names should not	be used	as arguments.

       -flinker-output=type
	   This	option controls	code generation	of  the	 link-time  optimizer.
	   By  default	the  linker  output is automatically determined	by the
	   linker plugin.  For	debugging  the	compiler  and  if  incremental
	   linking  with a non-LTO object file is desired, it may be useful to
	   control the type manually.

	   If type is exec, code generation produces a static binary. In  this
	   case	-fpic and -fpie	are both disabled.

	   If type is dyn, code	generation produces a shared library.  In this
	   case	 -fpic	or  -fPIC is preserved,	but not	enabled	automatically.
	   This	allows to build	shared libraries without  position-independent
	   code	on architectures where this is possible, i.e. on x86.

	   If  type is pie, code generation produces an	-fpie executable. This
	   results in similar optimizations as exec except that	-fpie  is  not
	   disabled if specified at compilation	time.

	   If  type  is	 rel, the compiler assumes that	incremental linking is
	   done.  The sections	containing  intermediate  code	for  link-time
	   optimization	are merged, pre-optimized, and output to the resulting
	   object file.	In addition, if	-ffat-lto-objects is specified,	binary
	   code	 is  produced  for  future  non-LTO  linking.  The object file
	   produced by incremental linking is smaller than  a  static  library
	   produced  from  the	same object files.  At link time the result of
	   incremental	linking	 also  loads  faster  than  a  static  library
	   assuming that the majority of objects in the	library	are used.

	   Finally  nolto-rel  configures the compiler for incremental linking
	   where code generation is forced, a final binary  is	produced,  and
	   the intermediate code for later link-time optimization is stripped.
	   When	 multiple  object files	are linked together the	resulting code
	   is better optimized than with link-time optimizations disabled (for
	   example, cross-module inlining happens), but	most  of  benefits  of
	   whole program optimizations are lost.

	   During  the	incremental link (by -r) the linker plugin defaults to
	   rel.	With current interfaces	to GNU	Binutils  it  is  however  not
	   possible to incrementally link LTO objects and non-LTO objects into
	   a  single mixed object file.	 If any	of object files	in incremental
	   link	cannot be used for link-time optimization, the	linker	plugin
	   issues  a  warning  and  uses  nolto-rel. To	maintain whole program
	   optimization, it is recommended to link such	 objects  into	static
	   library  instead.  Alternatively  it	 is  possible to use H.J. Lu's
	   binutils with support for mixed objects.

       -fuse-ld=bfd
	   Use the bfd linker instead of the default linker.

       -fuse-ld=gold
	   Use the gold	linker instead of the default linker.

       -fuse-ld=lld
	   Use the LLVM	lld linker instead of the default linker.

       -llibrary
       -l library
	   Search  the	library	 named	library	 when  linking.	  (The	second
	   alternative	with  the  library  as a separate argument is only for
	   POSIX compliance and	is not recommended.)

	   The -l option is passed directly to the linker by  GCC.   Refer  to
	   your	  linker   documentation   for	exact  details.	  The  general
	   description below applies to	the GNU	linker.

	   The linker searches a standard list of directories for the library.
	   The	directories   searched	 include   several   standard	system
	   directories plus any	that you specify with -L.

	   Static  libraries are archives of object files, and have file names
	   like	liblibrary.a.  Some targets  also  support  shared  libraries,
	   which  typically have names like liblibrary.so.  If both static and
	   shared libraries are	found, the linker gives	preference to  linking
	   with	the shared library unless the -static option is	used.

	   It  makes  a	difference where in the	command	you write this option;
	   the linker searches and processes libraries and object files	in the
	   order they are specified.  Thus, foo.o -lz bar.o searches library z
	   after file foo.o but	before bar.o.  If bar.o	refers to functions in
	   z, those functions may not be loaded.

       -lobjc
	   You need this special case of the -l	option in  order  to  link  an
	   Objective-C or Objective-C++	program.

       -nostartfiles
	   Do  not  use	 the  standard system startup files when linking.  The
	   standard system libraries  are  used	 normally,  unless  -nostdlib,
	   -nolibc, or -nodefaultlibs is used.

       -nodefaultlibs
	   Do  not  use	 the standard system libraries when linking.  Only the
	   libraries you  specify  are	passed	to  the	 linker,  and  options
	   specifying  linkage of the system libraries,	such as	-static-libgcc
	   or -shared-libgcc, are ignored.  The	 standard  startup  files  are
	   used	normally, unless -nostartfiles is used.

	   The compiler	may generate calls to "memcmp",	"memset", "memcpy" and
	   "memmove".	These entries are usually resolved by entries in libc.
	   These entry points should be	supplied through some other  mechanism
	   when	this option is specified.

       -nolibc
	   Do  not  use	the C library or system	libraries tightly coupled with
	   it when linking.  Still link	with  the  startup  files,  libgcc  or
	   toolchain  provided	language  support  libraries  such as libgnat,
	   libgfortran or libstdc++ unless options preventing their  inclusion
	   are used as well.  This typically removes -lc from the link command
	   line,  as  well  as	system	libraries that normally	go with	it and
	   become meaningless when absence of a	 C  library  is	 assumed,  for
	   example  -lpthread or -lm in	some configurations.  This is intended
	   for bare-board targets when there is	indeed no C library available.

       -nostdlib
	   Do not use the standard system  startup  files  or  libraries  when
	   linking.   No  startup files	and only the libraries you specify are
	   passed to the linker, and options specifying	linkage	of the	system
	   libraries, such as -static-libgcc or	-shared-libgcc,	are ignored.

	   The compiler	may generate calls to "memcmp",	"memset", "memcpy" and
	   "memmove".	These entries are usually resolved by entries in libc.
	   These entry points should be	supplied through some other  mechanism
	   when	this option is specified.

	   One	 of   the   standard   libraries  bypassed  by	-nostdlib  and
	   -nodefaultlibs is libgcc.a, a library of internal subroutines which
	   GCC uses  to	 overcome  shortcomings	 of  particular	 machines,  or
	   special needs for some languages.

	   In  most cases, you need libgcc.a even when you want	to avoid other
	   standard libraries.	In other words,	when you specify -nostdlib  or
	   -nodefaultlibs  you	should	usually	 specify  -lgcc	as well.  This
	   ensures that	you have no  unresolved	 references  to	 internal  GCC
	   library subroutines.	 (An example of	such an	internal subroutine is
	   "__main", used to ensure C++	constructors are called.)

       -e entry
       --entry=entry
	   Specify  that  the  program	entry point is entry.  The argument is
	   interpreted by the linker; the GNU linker accepts either  a	symbol
	   name	or an address.

       -pie
	   Produce  a  dynamically  linked  position independent executable on
	   targets that	support	it.  For predictable results,  you  must  also
	   specify the same set	of options used	for compilation	(-fpie,	-fPIE,
	   or model suboptions)	when you specify this linker option.

       -no-pie
	   Don't produce a dynamically linked position independent executable.

       -static-pie
	   Produce  a  static  position	independent executable on targets that
	   support it.	A static position independent executable is similar to
	   a static executable,	but can	be loaded at  any  address  without  a
	   dynamic linker.  For	predictable results, you must also specify the
	   same	 set  of  options used for compilation (-fpie, -fPIE, or model
	   suboptions) when you	specify	this linker option.

       -pthread
	   Link	with the POSIX threads library.	 This option is	 supported  on
	   GNU/Linux  targets,	most  other  Unix derivatives, and also	on x86
	   Cygwin and MinGW targets.  On some targets this  option  also  sets
	   flags  for  the preprocessor, so it should be used consistently for
	   both	compilation and	linking.

       -r  Produce a relocatable object	as output.   This  is  also  known  as
	   partial linking.

       -rdynamic
	   Pass	 the  flag  -export-dynamic to the ELF linker, on targets that
	   support it. This instructs the linker to add	all symbols, not  only
	   used	 ones,	to the dynamic symbol table. This option is needed for
	   some	uses of	"dlopen" or to allow obtaining backtraces from	within
	   a program.

       -s  Remove  all	symbol	table  and  relocation	information  from  the
	   executable.

       -static
	   On systems that support dynamic linking, this  overrides  -pie  and
	   prevents linking with the shared libraries.	On other systems, this
	   option has no effect.

       -shared
	   Produce a shared object which can then be linked with other objects
	   to  form  an	executable.  Not all systems support this option.  For
	   predictable results,	you must also specify the same set of  options
	   used	 for  compilation (-fpic, -fPIC, or model suboptions) when you
	   specify this	linker option.[1]

       -shared-libgcc
       -static-libgcc
	   On systems that provide libgcc as a shared library,	these  options
	   force the use of either the shared or static	version, respectively.
	   If  no  shared  version  of	libgcc was built when the compiler was
	   configured, these options have no effect.

	   There are several situations	in which an application	should use the
	   shared libgcc instead of the	static version.	 The  most  common  of
	   these  is when the application wishes to throw and catch exceptions
	   across different shared libraries.	In  that  case,	 each  of  the
	   libraries  as  well as the application itself should	use the	shared
	   libgcc.

	   Therefore,  the  G++	 driver	 automatically	 adds	-shared-libgcc
	   whenever  you  build	a shared library or a main executable, because
	   C++ programs	typically use exceptions, so this is the  right	 thing
	   to do.

	   If, instead,	you use	the GCC	driver to create shared	libraries, you
	   may	find  that  they are not always	linked with the	shared libgcc.
	   If GCC finds, at its	configuration time, that you  have  a  non-GNU
	   linker or a GNU linker that does not	support	option --eh-frame-hdr,
	   it  links  the  shared  version  of libgcc into shared libraries by
	   default.  Otherwise,	it takes advantage of the linker and optimizes
	   away	the linking with the shared version of	libgcc,	 linking  with
	   the static version of libgcc	by default.  This allows exceptions to
	   propagate   through	 such	shared	libraries,  without  incurring
	   relocation costs at library load time.

	   However, if a library or main executable is supposed	 to  throw  or
	   catch  exceptions,  you must	link it	using the G++ driver, or using
	   the option -shared-libgcc, such that	it is linked with  the	shared
	   libgcc.

       -static-libasan
	   When	 the  -fsanitize=address option	is used	to link	a program, the
	   GCC driver automatically links  against  libasan.   If  libasan  is
	   available  as a shared library, and the -static option is not used,
	   then	this  links  against  the  shared  version  of	libasan.   The
	   -static-libasan  option  directs  the  GCC  driver  to link libasan
	   statically, without necessarily linking other libraries statically.

       -static-libtsan
	   When	the -fsanitize=thread option is	used to	link  a	 program,  the
	   GCC	driver	automatically  links  against  libtsan.	 If libtsan is
	   available as	a shared library, and the -static option is not	 used,
	   then	 this  links  against  the  shared  version  of	 libtsan.  The
	   -static-libtsan option directs  the	GCC  driver  to	 link  libtsan
	   statically, without necessarily linking other libraries statically.

       -static-liblsan
	   When	 the -fsanitize=leak option is used to link a program, the GCC
	   driver  automatically  links	 against  liblsan.   If	  liblsan   is
	   available  as a shared library, and the -static option is not used,
	   then	this  links  against  the  shared  version  of	liblsan.   The
	   -static-liblsan  option  directs  the  GCC  driver  to link liblsan
	   statically, without necessarily linking other libraries statically.

       -static-libubsan
	   When	the -fsanitize=undefined option	is used	to link	a program, the
	   GCC driver automatically links against libubsan.   If  libubsan  is
	   available  as a shared library, and the -static option is not used,
	   then	this links  against  the  shared  version  of  libubsan.   The
	   -static-libubsan  option  directs  the  GCC driver to link libubsan
	   statically, without necessarily linking other libraries statically.

       -static-libstdc++
	   When	the g++	program	is used	to link	a  C++	program,  it  normally
	   automatically  links	 against libstdc++.  If	libstdc++ is available
	   as a	shared library,	and the	-static	option is not used, then  this
	   links  against  the	shared version of libstdc++.  That is normally
	   fine.  However, it is sometimes useful to  freeze  the  version  of
	   libstdc++  used by the program without going	all the	way to a fully
	   static link.	 The -static-libstdc++ option directs the  g++	driver
	   to  link  libstdc++	statically,  without necessarily linking other
	   libraries statically.

       -symbolic
	   Bind	references to global symbols when building  a  shared  object.
	   Warn	about any unresolved references	(unless	overridden by the link
	   editor  option  -Xlinker  -z	 -Xlinker  defs).   Only a few systems
	   support this	option.

       -T script
	   Use script as the linker script.  This option is supported by  most
	   systems  using the GNU linker.  On some targets, such as bare-board
	   targets without an operating	system,	the -T option may be  required
	   when	linking	to avoid references to undefined symbols.

       -Xlinker	option
	   Pass	option as an option to the linker.  You	can use	this to	supply
	   system-specific linker options that GCC does	not recognize.

	   If  you  want to pass an option that	takes a	separate argument, you
	   must	use -Xlinker twice, once for  the  option  and	once  for  the
	   argument.  For example, to pass -assert definitions,	you must write
	   -Xlinker  -assert  -Xlinker definitions.  It	does not work to write
	   -Xlinker "-assert definitions",  because  this  passes  the	entire
	   string as a single argument,	which is not what the linker expects.

	   When	 using	the  GNU linker, it is usually more convenient to pass
	   arguments to	linker options using the option=value syntax  than  as
	   separate   arguments.    For	 example,  you	can  specify  -Xlinker
	   -Map=output.map rather  than	 -Xlinker  -Map	 -Xlinker  output.map.
	   Other linkers may not support this syntax for command-line options.

       -Wl,option
	   Pass	option as an option to the linker.  If option contains commas,
	   it  is split	into multiple options at the commas.  You can use this
	   syntax  to  pass  an	 argument  to  the   option.	For   example,
	   -Wl,-Map,output.map	passes	-Map  output.map  to the linker.  When
	   using the GNU linker,  you  can  also  get  the  same  effect  with
	   -Wl,-Map=output.map.

       -u symbol
	   Pretend the symbol symbol is	undefined, to force linking of library
	   modules to define it.  You can use -u multiple times	with different
	   symbols to force loading of additional library modules.

       -z keyword
	   -z  is  passed  directly  on	 to  the linker	along with the keyword
	   keyword. See	the section in the documentation of  your  linker  for
	   permitted values and	their meanings.

   Options for Directory Search
       These  options  specify	directories  to	 search	 for header files, for
       libraries and for parts of the compiler:

       -I dir
       -iquote dir
       -isystem	dir
       -idirafter dir
	   Add the directory dir to the	list of	directories to be searched for
	   header files	 during	 preprocessing.	  If  dir  begins  with	 =  or
	   $SYSROOT, then the =	or $SYSROOT is replaced	by the sysroot prefix;
	   see --sysroot and -isysroot.

	   Directories	specified with -iquote apply only to the quote form of
	   the directive, "#include "file"".  Directories specified  with  -I,
	   -isystem,   or   -idirafter	 apply	 to   lookup   for   both  the
	   "#include "file"" and "#include <file>" directives.

	   You can specify any number or combination of	these options  on  the
	   command  line  to  search  for header files in several directories.
	   The lookup order is as follows:

	   1.  For the quote form of the include directive, the	 directory  of
	       the current file	is searched first.

	   2.  For  the	 quote	form of	the include directive, the directories
	       specified by -iquote  options  are  searched  in	 left-to-right
	       order, as they appear on	the command line.

	   3.  Directories  specified  with -I options are scanned in left-to-
	       right order.

	   4.  Directories specified with  -isystem  options  are  scanned  in
	       left-to-right order.

	   5.  Standard	system directories are scanned.

	   6.  Directories  specified  with  -idirafter	options	are scanned in
	       left-to-right order.

	   You can use -I to override a	system header file, substituting  your
	   own	version,  since	 these	directories  are  searched  before the
	   standard system header file directories.  However, you  should  not
	   use	this  option  to  add directories that contain vendor-supplied
	   system header files;	use -isystem for that.

	   The -isystem	and -idirafter options also mark the  directory	 as  a
	   system  directory,  so that it gets the same	special	treatment that
	   is applied to the standard system directories.

	   If a	standard system	include	directory, or  a  directory  specified
	   with	-isystem, is also specified with -I, the -I option is ignored.
	   The	directory  is  still searched but as a system directory	at its
	   normal position in the system include chain.	  This	is  to	ensure
	   that	 GCC's	procedure to fix buggy system headers and the ordering
	   for the "#include_next" directive are  not  inadvertently  changed.
	   If	you  really  need  to  change  the  search  order  for	system
	   directories,	use the	-nostdinc and/or -isystem options.

       -I- Split the include path.  This option	has been  deprecated.	Please
	   use	-iquote	 instead  for -I directories before the	-I- and	remove
	   the -I- option.

	   Any directories specified with -I options before -I-	 are  searched
	   only	 for  headers  requested  with "#include "file""; they are not
	   searched for	 "#include <file>".   If  additional  directories  are
	   specified  with  -I	options	 after	the -I-, those directories are
	   searched for	all #include directives.

	   In addition,	-I- inhibits the use of	the directory of  the  current
	   file	directory as the first search directory	for "#include "file"".
	   There is no way to override this effect of -I-.

       -iprefix	prefix
	   Specify  prefix  as the prefix for subsequent -iwithprefix options.
	   If the prefix represents a directory, you should include the	 final
	   /.

       -iwithprefix dir
       -iwithprefixbefore dir
	   Append  dir	to  the	prefix specified previously with -iprefix, and
	   add	the  resulting	directory  to	the   include	search	 path.
	   -iwithprefixbefore puts it in the same place	-I would; -iwithprefix
	   puts	it where -idirafter would.

       -isysroot dir
	   This	 option	 is  like  the	--sysroot  option, but applies only to
	   header files	(except	for Darwin targets, where it applies  to  both
	   header  files  and  libraries).   See the --sysroot option for more
	   information.

       -imultilib dir
	   Use dir as a	 subdirectory  of  the	directory  containing  target-
	   specific C++	headers.

       -nostdinc
	   Do  not  search  the	 standard system directories for header	files.
	   Only	 the  directories  explicitly  specified  with	-I,   -iquote,
	   -isystem,  and/or  -idirafter  options  (and	 the  directory	of the
	   current file, if appropriate) are searched.

       -nostdinc++
	   Do not  search  for	header	files  in  the	C++-specific  standard
	   directories,	 but  do  still	search the other standard directories.
	   (This option	is used	when building the C++ library.)

       -iplugindir=dir
	   Set the  directory  to  search  for	plugins	 that  are  passed  by
	   -fplugin=name instead of -fplugin=path/name.so.  This option	is not
	   meant to be used by the user, but only passed by the	driver.

       -Ldir
	   Add directory dir to	the list of directories	to be searched for -l.

       -Bprefix
	   This	 option	 specifies  where  to find the executables, libraries,
	   include files, and data files of the	compiler itself.

	   The compiler	driver program runs one	or  more  of  the  subprograms
	   cpp,	 cc1, as and ld.  It tries prefix as a prefix for each program
	   it tries to run, both with and  without  machine/version/  for  the
	   corresponding target	machine	and compiler version.

	   For	each subprogram	to be run, the compiler	driver first tries the
	   -B prefix, if any.  If that name is not found,  or  if  -B  is  not
	   specified,  the  driver  tries two standard prefixes, /usr/lib/gcc/
	   and /usr/local/lib/gcc/.  If	neither	of those  results  in  a  file
	   name	 that  is  found,  the unmodified program name is searched for
	   using the directories specified in your PATH	environment variable.

	   The compiler	checks to see if the path provided by -B refers	 to  a
	   directory, and if necessary it adds a directory separator character
	   at the end of the path.

	   -B  prefixes	that effectively specify directory names also apply to
	   libraries in	the linker,  because  the  compiler  translates	 these
	   options into	-L options for the linker.  They also apply to include
	   files  in  the  preprocessor, because the compiler translates these
	   options into	-isystem options for the preprocessor.	In this	 case,
	   the compiler	appends	include	to the prefix.

	   The	runtime	 support  file libgcc.a	can also be searched for using
	   the -B prefix, if needed.  If  it  is  not  found  there,  the  two
	   standard  prefixes  above  are tried, and that is all.  The file is
	   left	out of the link	if it is not found by those means.

	   Another way to specify a prefix much	like the -B prefix is  to  use
	   the environment variable GCC_EXEC_PREFIX.

	   As  a  special kludge, if the path provided by -B is	[dir/]stageN/,
	   where N is a	number in the range 0 to 9, then  it  is  replaced  by
	   [dir/]include.  This	is to help with	boot-strapping the compiler.

       -no-canonical-prefixes
	   Do  not  expand  any	 symbolic links, resolve references to /../ or
	   /./,	or make	the path absolute when generating a relative prefix.

       --sysroot=dir
	   Use dir as the logical root directory for  headers  and  libraries.
	   For	example,  if  the  compiler  normally  searches	for headers in
	   /usr/include	 and  libraries	 in  /usr/lib,	it  instead   searches
	   dir/usr/include and dir/usr/lib.

	   If  you  use	 both  this  option and	the -isysroot option, then the
	   --sysroot option applies to libraries,  but	the  -isysroot	option
	   applies to header files.

	   The	GNU  linker  (beginning	 with  version 2.16) has the necessary
	   support for this option.  If	your  linker  does  not	 support  this
	   option,  the	 header	 file aspect of	--sysroot still	works, but the
	   library aspect does not.

       --no-sysroot-suffix
	   For some targets, a suffix is added to the root directory specified
	   with	--sysroot, depending  on  the  other  options  used,  so  that
	   headers  may	for example be found in	dir/suffix/usr/include instead
	   of dir/usr/include.	This option disables the addition  of  such  a
	   suffix.

   Options for Code Generation Conventions
       These  machine-independent  options  control  the interface conventions
       used in code generation.

       Most of them have both positive and negative forms; the	negative  form
       of  -ffoo  is  -fno-foo.	  In the table below, only one of the forms is
       listed---the one	that is	not the	default.  You can figure out the other
       form by either removing no- or adding it.

       -fstack-reuse=reuse-level
	   This	option controls	stack space reuse for user declared local/auto
	   variables and compiler generated temporaries.  reuse_level  can  be
	   all,	 named_vars,  or  none.	 all enables stack reuse for all local
	   variables and temporaries, named_vars enables the  reuse  only  for
	   user	 defined  local	 variables with	names, and none	disables stack
	   reuse completely. The default value is all. The  option  is	needed
	   when	the program extends the	lifetime of a scoped local variable or
	   a  compiler generated temporary beyond the end point	defined	by the
	   language.  When a lifetime of a variable ends, and if the  variable
	   lives  in  memory, the optimizing compiler has the freedom to reuse
	   its stack space with	other temporaries or  scoped  local  variables
	   whose  live	range  does not	overlap	with it. Legacy	code extending
	   local  lifetime  is	likely	to  break   with   the	 stack	 reuse
	   optimization.

	   For example,

		      int *p;
		      {
			int local1;

			p = &local1;
			local1 = 10;
			....
		      }
		      {
			 int local2;
			 local2	= 20;
			 ...
		      }

		      if (*p ==	10)  //	out of scope use of local1
			{

			}

	   Another example:

		      struct A
		      {
			  A(int	k) : i(k), j(k)	{ }
			  int i;
			  int j;
		      };

		      A	*ap;

		      void foo(const A&	ar)
		      {
			 ap = &ar;
		      }

		      void bar()
		      {
			 foo(A(10)); //	temp object's lifetime ends when foo returns

			 {
			   A a(20);
			   ....
			 }
			 ap->i+= 10;  // ap references out of scope temp whose space
				      // is reused with	a. What	is the value of	ap->i?
		      }

	   The	lifetime  of a compiler	generated temporary is well defined by
	   the C++ standard. When a lifetime of	a temporary ends, and  if  the
	   temporary  lives in memory, the optimizing compiler has the freedom
	   to reuse its	stack space with other	temporaries  or	 scoped	 local
	   variables  whose  live range	does not overlap with it. However some
	   of the legacy code relies on	the behavior  of  older	 compilers  in
	   which  temporaries' stack space is not reused, the aggressive stack
	   reuse can lead to runtime errors. This option is  used  to  control
	   the temporary stack reuse optimization.

       -ftrapv
	   This	 option	 generates  traps  for	signed	overflow  on addition,
	   subtraction,	multiplication operations.  The	 options  -ftrapv  and
	   -fwrapv  override  each  other,  so	using  -ftrapv	-fwrapv	on the
	   command-line	results	in -fwrapv being effective.   Note  that  only
	   active options override, so using -ftrapv -fwrapv -fno-wrapv	on the
	   command-line	results	in -ftrapv being effective.

       -fwrapv
	   This	option instructs the compiler to assume	that signed arithmetic
	   overflow  of	 addition, subtraction and multiplication wraps	around
	   using  twos-complement  representation.   This  flag	 enables  some
	   optimizations and disables others.  The options -ftrapv and -fwrapv
	   override  each  other, so using -ftrapv -fwrapv on the command-line
	   results in -fwrapv being effective.	Note that only active  options
	   override,  so  using	-ftrapv	-fwrapv	-fno-wrapv on the command-line
	   results in -ftrapv being effective.

       -fwrapv-pointer
	   This	 option	 instructs  the	 compiler  to  assume	that   pointer
	   arithmetic  overflow	on addition and	subtraction wraps around using
	   twos-complement   representation.	This   flag   disables	  some
	   optimizations which assume pointer overflow is invalid.

       -fstrict-overflow
	   This	 option	implies	-fno-wrapv -fno-wrapv-pointer and when negated
	   implies -fwrapv -fwrapv-pointer.

       -fexceptions
	   Enable  exception  handling.	  Generates  extra  code   needed   to
	   propagate exceptions.  For some targets, this implies GCC generates
	   frame  unwind  information  for  all	 functions,  which can produce
	   significant	data  size  overhead,  although	 it  does  not	affect
	   execution.	If  you	 do not	specify	this option, GCC enables it by
	   default for languages like  C++  that  normally  require  exception
	   handling, and disables it for languages like	C that do not normally
	   require  it.	  However,  you	 may  need  to enable this option when
	   compiling C code that needs to interoperate properly	with exception
	   handlers written in C++.  You may also wish to disable this	option
	   if  you  are	 compiling older C++ programs that don't use exception
	   handling.

       -fnon-call-exceptions
	   Generate  code  that	 allows	  trapping   instructions   to	 throw
	   exceptions.	 Note  that  this  requires  platform-specific runtime
	   support that	does not exist everywhere.  Moreover, it  only	allows
	   trapping  instructions  to throw exceptions,	i.e. memory references
	   or floating-point instructions.  It does not	allow exceptions to be
	   thrown from arbitrary signal	handlers such as "SIGALRM".

       -fdelete-dead-exceptions
	   Consider that instructions that  may	 throw	exceptions  but	 don't
	   otherwise  contribute  to  the  execution  of  the  program	can be
	   optimized away.  This option	is enabled  by	default	 for  the  Ada
	   compiler,   as   permitted	by  the	 Ada  language	specification.
	   Optimization	passes that cause dead exceptions to  be  removed  are
	   enabled independently at different optimization levels.

       -funwind-tables
	   Similar  to	-fexceptions, except that it just generates any	needed
	   static data,	but does not affect the	generated code	in  any	 other
	   way.	  You  normally	 do not	need to	enable this option; instead, a
	   language processor that needs this  handling	 enables  it  on  your
	   behalf.

       -fasynchronous-unwind-tables
	   Generate  unwind  table  in	DWARF  format,	if supported by	target
	   machine.  The table is exact	at each	instruction  boundary,	so  it
	   can	be  used for stack unwinding from asynchronous events (such as
	   debugger or garbage collector).

       -fno-gnu-unique
	   On systems with  recent  GNU	 assembler  and	 C  library,  the  C++
	   compiler  uses  the	"STB_GNU_UNIQUE"  binding  to  make  sure that
	   definitions of  template  static  data  members  and	 static	 local
	   variables  in  inline  functions are	unique even in the presence of
	   "RTLD_LOCAL"; this is necessary to avoid problems  with  a  library
	   used	  by   two  different  "RTLD_LOCAL"  plugins  depending	 on  a
	   definition in one of	them and therefore disagreeing with the	 other
	   one	about the binding of the symbol.  But this causes "dlclose" to
	   be  ignored	for  affected  DSOs;  if  your	 program   relies   on
	   reinitialization  of	 a DSO via "dlclose" and "dlopen", you can use
	   -fno-gnu-unique.

       -fpcc-struct-return
	   Return "short" "struct" and "union" values in  memory  like	longer
	   ones, rather	than in	registers.  This convention is less efficient,
	   but	it has the advantage of	allowing intercallability between GCC-
	   compiled  files  and	  files	  compiled   with   other   compilers,
	   particularly	the Portable C Compiler	(pcc).

	   The	precise	 convention for	returning structures in	memory depends
	   on the target configuration macros.

	   Short structures and	unions are  those  whose  size	and  alignment
	   match that of some integer type.

	   Warning:  code  compiled with the -fpcc-struct-return switch	is not
	   binary compatible with code compiled	with  the  -freg-struct-return
	   switch.   Use  it  to  conform  to a	non-default application	binary
	   interface.

       -freg-struct-return
	   Return "struct" and "union"	values	in  registers  when  possible.
	   This	   is	 more	 efficient    for    small   structures	  than
	   -fpcc-struct-return.

	   If you specify neither -fpcc-struct-return nor -freg-struct-return,
	   GCC defaults	to whichever convention	is standard  for  the  target.
	   If	there	is   no	  standard   convention,   GCC	 defaults   to
	   -fpcc-struct-return,	except on targets where	GCC is	the  principal
	   compiler.  In those cases, we can choose the	standard, and we chose
	   the more efficient register return alternative.

	   Warning:  code  compiled with the -freg-struct-return switch	is not
	   binary compatible with code compiled	with  the  -fpcc-struct-return
	   switch.   Use  it  to  conform  to a	non-default application	binary
	   interface.

       -fshort-enums
	   Allocate to an "enum" type only as many bytes as it needs  for  the
	   declared  range  of possible	values.	 Specifically, the "enum" type
	   is equivalent to the	smallest integer type that has enough room.

	   Warning: the	-fshort-enums switch causes GCC	to generate code  that
	   is  not  binary compatible with code	generated without that switch.
	   Use it to conform to	a non-default application binary interface.

       -fshort-wchar
	   Override the	underlying type	for "wchar_t" to  be  "short  unsigned
	   int"	 instead of the	default	for the	target.	 This option is	useful
	   for building	programs to run	under WINE.

	   Warning: the	-fshort-wchar switch causes GCC	to generate code  that
	   is  not  binary compatible with code	generated without that switch.
	   Use it to conform to	a non-default application binary interface.

       -fcommon
	   In C	code, this option controls the placement of  global  variables
	   defined  without  an	initializer, known as tentative	definitions in
	   the	C  standard.   Tentative   definitions	 are   distinct	  from
	   declarations	 of a variable with the	"extern" keyword, which	do not
	   allocate storage.

	   The default is  -fno-common,	 which	specifies  that	 the  compiler
	   places  uninitialized  global  variables  in	the BSS	section	of the
	   object file.	 This inhibits the merging of tentative	definitions by
	   the linker so you get  a  multiple-definition  error	 if  the  same
	   variable is accidentally defined in more than one compilation unit.

	   The	-fcommon  places  uninitialized	 global	 variables in a	common
	   block.  This	allows the linker to resolve all tentative definitions
	   of the same variable	in different compilation  units	 to  the  same
	   object,  or	to  a  non-tentative  definition.   This  behavior  is
	   inconsistent	with C++, and on many targets implies a	speed and code
	   size	penalty	on global variable references.	It is mainly useful to
	   enable legacy code to link without errors.

       -fno-ident
	   Ignore the "#ident" directive.

       -finhibit-size-directive
	   Don't output	a ".size" assembler directive, or anything  else  that
	   would cause trouble if the function is split	in the middle, and the
	   two	halves	are  placed  at	 locations  far	apart in memory.  This
	   option is used when compiling crtstuff.c; you should	 not  need  to
	   use it for anything else.

       -fverbose-asm
	   Put	extra commentary information in	the generated assembly code to
	   make	it more	readable.  This	option is generally  only  of  use  to
	   those  who  actually	 need  to  read	 the  generated	 assembly code
	   (perhaps while debugging the	compiler itself).

	   -fno-verbose-asm, the default, causes the extra information	to  be
	   omitted and is useful when comparing	two assembler files.

	   The added comments include:

	   *   information on the compiler version and command-line options,

	   *   the   source   code   lines   associated	  with	 the  assembly
	       instructions, in	the form FILENAME:LINENUMBER:CONTENT OF	LINE,

	   *   hints on	which high-level expressions correspond	to the various
	       assembly	instruction operands.

	   For example,	given this C source file:

		   int test (int n)
		   {
		     int i;
		     int total = 0;

		     for (i = 0; i < n;	i++)
		       total +=	i * i;

		     return total;
		   }

	   compiling to	(x86_64) assembly  via	-S  and	 emitting  the	result
	   direct to stdout via	-o -

		   gcc -S test.c -fverbose-asm -Os -o -

	   gives output	similar	to this:

			   .file   "test.c"
		   # GNU C11 (GCC) version 7.0.0 20160809 (experimental) (x86_64-pc-linux-gnu)
		     [...snip...]
		   # options passed:
		     [...snip...]

			   .text
			   .globl  test
			   .type   test, @function
		   test:
		   .LFB0:
			   .cfi_startproc
		   # test.c:4:	 int total = 0;
			   xorl	   %eax, %eax	   # <retval>
		   # test.c:6:	 for (i	= 0; i < n; i++)
			   xorl	   %edx, %edx	   # i
		   .L2:
		   # test.c:6:	 for (i	= 0; i < n; i++)
			   cmpl	   %edi, %edx	   # n,	i
			   jge	   .L5	   #,
		   # test.c:7:	   total += i *	i;
			   movl	   %edx, %ecx	   # i,	tmp92
			   imull   %edx, %ecx	   # i,	tmp92
		   # test.c:6:	 for (i	= 0; i < n; i++)
			   incl	   %edx	   # i
		   # test.c:7:	   total += i *	i;
			   addl	   %ecx, %eax	   # tmp92, <retval>
			   jmp	   .L2	   #
		   .L5:
		   # test.c:10:	}
			   ret
			   .cfi_endproc
		   .LFE0:
			   .size   test, .-test
			   .ident  "GCC: (GNU) 7.0.0 20160809 (experimental)"
			   .section	   .note.GNU-stack,"",@progbits

	   The comments	are intended for humans	rather than machines and hence
	   the precise format of the comments is subject to change.

       -frecord-gcc-switches
	   This	 switch	causes the command line	used to	invoke the compiler to
	   be recorded into the	object	file  that  is	being  created.	  This
	   switch  is only implemented on some targets and the exact format of
	   the recording is target and binary file format  dependent,  but  it
	   usually  takes  the	form of	a section containing ASCII text.  This
	   switch is related to	the -fverbose-asm switch, but that switch only
	   records information in the assembler	output file as comments, so it
	   never reaches the object file.  See also -grecord-gcc-switches  for
	   another way of storing compiler options into	the object file.

       -fpic
	   Generate  position-independent  code	 (PIC)	suitable  for use in a
	   shared library, if supported	for the	 target	 machine.   Such  code
	   accesses  all  constant  addresses  through	a  global offset table
	   (GOT).  The dynamic	loader	resolves  the  GOT  entries  when  the
	   program  starts  (the dynamic loader	is not part of GCC; it is part
	   of  the  operating  system).	  If  the  GOT	size  for  the	linked
	   executable  exceeds	a  machine-specific  maximum  size, you	get an
	   error message from the linker indicating that -fpic does not	 work;
	   in that case, recompile with	-fPIC instead.	(These maximums	are 8k
	   on  the SPARC, 28k on AArch64 and 32k on the	m68k and RS/6000.  The
	   x86 has no such limit.)

	   Position-independent	code requires special support,	and  therefore
	   works  only on certain machines.  For the x86, GCC supports PIC for
	   System V but	not for	the Sun	386i.	Code  generated	 for  the  IBM
	   RS/6000 is always position-independent.

	   When	 this  flag  is	 set,  the  macros "__pic__" and "__PIC__" are
	   defined to 1.

       -fPIC
	   If supported	for  the  target  machine,  emit  position-independent
	   code,  suitable  for	 dynamic linking and avoiding any limit	on the
	   size	of the global offset table.  This option makes a difference on
	   AArch64, m68k, PowerPC and SPARC.

	   Position-independent	code requires special support,	and  therefore
	   works only on certain machines.

	   When	 this  flag  is	 set,  the  macros "__pic__" and "__PIC__" are
	   defined to 2.

       -fpie
       -fPIE
	   These options are similar to	-fpic and  -fPIC,  but	the  generated
	   position-independent	 code  can  be	only  linked into executables.
	   Usually these options are used to compile code that will be	linked
	   using the -pie GCC option.

	   -fpie  and  -fPIE  both  define the macros "__pie__"	and "__PIE__".
	   The macros have the value 1 for -fpie and 2 for -fPIE.

       -fno-plt
	   Do not use  the  PLT	 for  external	function  calls	 in  position-
	   independent	code.	Instead, load the callee address at call sites
	   from	the GOT	and branch to it.  This	leads to more  efficient  code
	   by  eliminating  PLT	stubs and exposing GOT loads to	optimizations.
	   On architectures such as 32-bit x86 where PLT stubs expect the  GOT
	   pointer in a	specific register, this	gives more register allocation
	   freedom  to	the  compiler.	 Lazy binding requires use of the PLT;
	   with	-fno-plt all external symbols are resolved at load time.

	   Alternatively, the function attribute "noplt" can be	used to	 avoid
	   calls through the PLT for specific external functions.

	   In  position-dependent  code,  a  few targets also convert calls to
	   functions that are marked to	 not  use  the	PLT  to	 use  the  GOT
	   instead.

       -fno-jump-tables
	   Do not use jump tables for switch statements	even where it would be
	   more	 efficient than	other code generation strategies.  This	option
	   is of use in	conjunction with -fpic or -fPIC	for building code that
	   forms part of a dynamic linker and cannot reference the address  of
	   a  jump  table.   On	some targets, jump tables do not require a GOT
	   and this option is not needed.

       -fno-bit-tests
	   Do not use bit tests	for switch statements even where it  would  be
	   more	efficient than other code generation strategies.

       -ffixed-reg
	   Treat  the  register	 named reg as a	fixed register;	generated code
	   should never	refer to it (except perhaps as a stack pointer,	 frame
	   pointer or in some other fixed role).

	   reg	must  be  the name of a	register.  The register	names accepted
	   are machine-specific	and are	defined	in the "REGISTER_NAMES"	 macro
	   in the machine description macro file.

	   This	 flag  does  not  have a negative form,	because	it specifies a
	   three-way choice.

       -fcall-used-reg
	   Treat the register named reg	 as  an	 allocable  register  that  is
	   clobbered  by  function calls.  It may be allocated for temporaries
	   or variables	that do	not live across	a  call.   Functions  compiled
	   this	way do not save	and restore the	register reg.

	   It  is  an  error  to use this flag with the	frame pointer or stack
	   pointer.  Use of this flag for  other  registers  that  have	 fixed
	   pervasive   roles   in   the	 machine's  execution  model  produces
	   disastrous results.

	   This	flag does not have a negative form,  because  it  specifies  a
	   three-way choice.

       -fcall-saved-reg
	   Treat  the  register	 named	reg  as	an allocable register saved by
	   functions.  It may be allocated even	for temporaries	 or  variables
	   that	 live  across  a  call.	  Functions compiled this way save and
	   restore the register	reg if they use	it.

	   It is an error to use this flag with	the  frame  pointer  or	 stack
	   pointer.   Use  of  this  flag  for other registers that have fixed
	   pervasive  roles  in	 the  machine's	  execution   model   produces
	   disastrous results.

	   A  different	sort of	disaster results from the use of this flag for
	   a register in which function	values may be returned.

	   This	flag does not have a negative form,  because  it  specifies  a
	   three-way choice.

       -fpack-struct[=n]
	   Without  a  value  specified,  pack	all structure members together
	   without holes.  When	a value	is specified (which must  be  a	 small
	   power  of  two),  pack  structure  members according	to this	value,
	   representing	the maximum alignment (that is,	objects	 with  default
	   alignment  requirements  larger  than  this	are output potentially
	   unaligned at	the next fitting location.

	   Warning: the	-fpack-struct switch causes GCC	to generate code  that
	   is  not  binary compatible with code	generated without that switch.
	   Additionally, it makes the code suboptimal.	Use it to conform to a
	   non-default application binary interface.

       -fleading-underscore
	   This	option and its counterpart, -fno-leading-underscore,  forcibly
	   change  the	way C symbols are represented in the object file.  One
	   use is to help link with legacy assembly code.

	   Warning: the	-fleading-underscore switch  causes  GCC  to  generate
	   code	that is	not binary compatible with code	generated without that
	   switch.   Use  it  to  conform  to a	non-default application	binary
	   interface.  Not all	targets	 provide  complete  support  for  this
	   switch.

       -ftls-model=model
	   Alter  the  thread-local  storage  model  to	 be  used.   The model
	   argument should be one of global-dynamic,  local-dynamic,  initial-
	   exec	  or   local-exec.    Note  that  the  choice  is  subject  to
	   optimization: the compiler may  use	a  more	 efficient  model  for
	   symbols not visible outside of the translation unit,	or if -fpic is
	   not given on	the command line.

	   The	default	 without -fpic is initial-exec;	with -fpic the default
	   is global-dynamic.

       -ftrampolines
	   For targets that normally need trampolines  for  nested  functions,
	   always  generate them instead of using descriptors.	Otherwise, for
	   targets that	do not need them, like for example HP-PA or IA-64,  do
	   nothing.

	   A  trampoline  is a small piece of code that	is created at run time
	   on the stack	when the address of a nested function is taken,	and is
	   used	 to  call  the	nested	function  indirectly.	Therefore,  it
	   requires  the  stack	to be made executable in order for the program
	   to work properly.

	   -fno-trampolines is enabled by default on a	language  by  language
	   basis  to  let  the	compiler avoid generating them,	if it computes
	   that	this is	safe, and replace them with descriptors.   Descriptors
	   are	made  up of data only, but the generated code must be prepared
	   to deal with	them.  As of this writing, -fno-trampolines is enabled
	   by default only for Ada.

	   Moreover, code compiled with	-ftrampolines and code	compiled  with
	   -fno-trampolines  are not binary compatible if nested functions are
	   present.  This option must therefore	 be  used  on  a  program-wide
	   basis and be	manipulated with extreme care.

       -fvisibility=[default|internal|hidden|protected]
	   Set	the  default  ELF  image  symbol  visibility  to the specified
	   option---all	symbols	are marked with	this unless overridden	within
	   the	code.	Using  this  feature  can  very	 substantially improve
	   linking and load times of shared  object  libraries,	 produce  more
	   optimized  code, provide near-perfect API export and	prevent	symbol
	   clashes.  It	is strongly recommended	 that  you  use	 this  in  any
	   shared objects you distribute.

	   Despite  the	 nomenclature,	default	 always	 means	public;	 i.e.,
	   available to	be linked against  from	 outside  the  shared  object.
	   protected  and  internal  are pretty	useless	in real-world usage so
	   the only other commonly used	option	is  hidden.   The  default  if
	   -fvisibility	 isn't	specified  is default, i.e., make every	symbol
	   public.

	   A good explanation of the benefits offered by ensuring ELF  symbols
	   have	 the  correct  visibility  is  given  by  "How To Write	Shared
	   Libraries"	by   Ulrich   Drepper	(which	 can   be   found   at
	   <https://www.akkadia.org/drepper/>)---however  a  superior solution
	   made	possible by this option	to  marking  things  hidden  when  the
	   default  is	public	is  to make the	default	hidden and mark	things
	   public.   This  is  the  norm  with	DLLs  on  Windows   and	  with
	   -fvisibility=hidden	and  "__attribute__ ((visibility("default")))"
	   instead  of	"__declspec(dllexport)"	 you  get   almost   identical
	   semantics  with  identical  syntax.	 This is a great boon to those
	   working with	cross-platform projects.

	   For those adding visibility support to existing code, you may  find
	   "#pragma  GCC  visibility" of use.  This works by you enclosing the
	   declarations	you wish to set	 visibility  for  with	(for  example)
	   "#pragma  GCC  visibility push(hidden)" and "#pragma	GCC visibility
	   pop".  Bear in mind that symbol visibility should be	viewed as part
	   of the API interface	contract and thus all new code	should	always
	   specify  visibility	when it	is not the default; i.e., declarations
	   only	 for  use  within  the	local  DSO  should  always  be	marked
	   explicitly	as   hidden   as   so	to   avoid   PLT   indirection
	   overheads---making this abundantly clear also aids readability  and
	   self-documentation	of  the	 code.	 Note  that  due  to  ISO  C++
	   specification requirements, "operator new"  and  "operator  delete"
	   must	always be of default visibility.

	   Be  aware  that  headers  from  outside your	project, in particular
	   system headers and headers from any other library you use, may  not
	   be expecting	to be compiled with visibility other than the default.
	   You	 may   need   to   explicitly	say  "#pragma  GCC  visibility
	   push(default)" before including any such headers.

	   "extern" declarations are not affected by -fvisibility, so a	lot of
	   code	 can  be   recompiled	with   -fvisibility=hidden   with   no
	   modifications.    However,	this  means  that  calls  to  "extern"
	   functions with no explicit visibility use the PLT, so  it  is  more
	   effective  to  use "__attribute ((visibility))" and/or "#pragma GCC
	   visibility" to tell the compiler which "extern" declarations	should
	   be treated as hidden.

	   Note	that -fvisibility does affect C++ vague	linkage	entities. This
	   means that, for instance, an	exception  class  that	is  be	thrown
	   between  DSOs  must be explicitly marked with default visibility so
	   that	the type_info nodes are	unified	between	the DSOs.

	   An overview of these	techniques, their benefits and how to use them
	   is at <http://gcc.gnu.org/wiki/Visibility>.

       -fstrict-volatile-bitfields
	   This	option should be used if accesses to volatile  bit-fields  (or
	   other  structure fields, although the compiler usually honors those
	   types anyway) should	use a  single  access  of  the	width  of  the
	   field's  type,  aligned  to	a  natural alignment if	possible.  For
	   example, targets  with  memory-mapped  peripheral  registers	 might
	   require  all	 such  accesses	to be 16 bits wide; with this flag you
	   can declare all peripheral bit-fields as "unsigned short" (assuming
	   short is 16 bits on these targets)  to  force  GCC  to  use	16-bit
	   accesses instead of,	perhaps, a more	efficient 32-bit access.

	   If  this  option  is	disabled, the compiler uses the	most efficient
	   instruction.	 In the	previous example, that might be	a 32-bit  load
	   instruction,	 even  though  that accesses bytes that	do not contain
	   any portion of the bit-field, or memory-mapped registers  unrelated
	   to the one being updated.

	   In  some cases, such	as when	the "packed" attribute is applied to a
	   structure field, it may not be possible to access the field with  a
	   single  read	 or  write  that  is  correctly	aligned	for the	target
	   machine.  In	this  case  GCC	 falls	back  to  generating  multiple
	   accesses rather than	code that will fault or	truncate the result at
	   run time.

	   Note:   Due	to  restrictions  of  the  C/C++11 memory model, write
	   accesses are	not allowed to touch non  bit-field  members.	It  is
	   therefore  recommended  to  define  all bits	of the field's type as
	   bit-field members.

	   The default value of	this option is determined by  the  application
	   binary interface for	the target processor.

       -fsync-libcalls
	   This	 option	 controls  whether  any	 out-of-line  instance	of the
	   "__sync" family of functions	may be used  to	 implement  the	 C++11
	   "__atomic" family of	functions.

	   The	default	 value of this option is enabled, thus the only	useful
	   form	of the option is -fno-sync-libcalls.  This option is  used  in
	   the implementation of the libatomic runtime library.

   GCC Developer Options
       This  section  describes	 command-line  options	that  are primarily of
       interest	to GCC	developers,  including	options	 to  support  compiler
       testing and investigation of compiler bugs and compile-time performance
       problems.   This	 includes  options that	produce	debug dumps at various
       points in the compilation; that print statistics	such as	memory use and
       execution time; and that	print information about	 GCC's	configuration,
       such as where it	searches for libraries.	 You should rarely need	to use
       any of these options for	ordinary compilation and linking tasks.

       Many  developer options that cause GCC to dump output to	a file take an
       optional	=filename suffix. You can specify  stdout  or  -  to  dump  to
       standard	output,	and stderr for standard	error.

       If  =filename  is  omitted,  a default dump file	name is	constructed by
       concatenating the base dump file	name, a	pass number, phase letter, and
       pass name.  The base dump file name is the name of output file produced
       by  the	compiler  if  explicitly  specified  and  not  an  executable;
       otherwise it is the source file name.  The pass number is determined by
       the order passes	are registered with the	compiler's pass	manager.  This
       is  generally the same as the order of execution, but passes registered
       by plugins,  target-specific  passes,  or  passes  that	are  otherwise
       registered  late	are numbered higher than the pass named	final, even if
       they are	executed earlier.  The	phase  letter  is  one	of  i  (inter-
       procedural analysis), l (language-specific), r (RTL), or	t (tree).  The
       files are created in the	directory of the output	file.

       -fcallgraph-info
       -fcallgraph-info=MARKERS
	   Makes the compiler output callgraph information for the program, on
	   a  per-object-file  basis.	The  information  is  generated	in the
	   common VCG format.  It can be decorated with	 additional,  per-node
	   and/or  per-edge  information, if a list of comma-separated markers
	   is additionally specified.  When the	"su" marker is specified,  the
	   callgraph   is  decorated  with  stack  usage  information;	it  is
	   equivalent to -fstack-usage.	 When the "da"	marker	is  specified,
	   the	callgraph  is  decorated  with	information  about dynamically
	   allocated objects.

	   When	compiling with -flto, no callgraph information is output along
	   with	the object file.   At  LTO  link  time,	 -fcallgraph-info  may
	   generate  multiple callgraph	information files next to intermediate
	   LTO output files.

       -dletters
       -fdump-rtl-pass
       -fdump-rtl-pass=filename
	   Says	to make	debugging dumps	during compilation at times  specified
	   by letters.	This is	used for debugging the RTL-based passes	of the
	   compiler.

	   Some	 -dletters switches have different meaning when	-E is used for
	   preprocessing.

	   Debug dumps can be enabled with a  -fdump-rtl  switch  or  some  -d
	   option  letters.  Here are the possible letters for use in pass and
	   letters, and	their meanings:

	   -fdump-rtl-alignments
	       Dump after branch alignments have been computed.

	   -fdump-rtl-asmcons
	       Dump after fixing rtl statements	that have  unsatisfied	in/out
	       constraints.

	   -fdump-rtl-auto_inc_dec
	       Dump  after  auto-inc-dec  discovery.  This pass	is only	run on
	       architectures that have auto inc	or auto	dec instructions.

	   -fdump-rtl-barriers
	       Dump after cleaning up the barrier instructions.

	   -fdump-rtl-bbpart
	       Dump after partitioning hot and cold basic blocks.

	   -fdump-rtl-bbro
	       Dump after block	reordering.

	   -fdump-rtl-btl1
	   -fdump-rtl-btl2
	       -fdump-rtl-btl1 and -fdump-rtl-btl2 enable  dumping  after  the
	       two branch target load optimization passes.

	   -fdump-rtl-bypass
	       Dump after jump bypassing and control flow optimizations.

	   -fdump-rtl-combine
	       Dump after the RTL instruction combination pass.

	   -fdump-rtl-compgotos
	       Dump after duplicating the computed gotos.

	   -fdump-rtl-ce1
	   -fdump-rtl-ce2
	   -fdump-rtl-ce3
	       -fdump-rtl-ce1,	 -fdump-rtl-ce2,   and	-fdump-rtl-ce3	enable
	       dumping after the three if conversion passes.

	   -fdump-rtl-cprop_hardreg
	       Dump after hard register	copy propagation.

	   -fdump-rtl-csa
	       Dump after combining stack adjustments.

	   -fdump-rtl-cse1
	   -fdump-rtl-cse2
	       -fdump-rtl-cse1 and -fdump-rtl-cse2 enable  dumping  after  the
	       two common subexpression	elimination passes.

	   -fdump-rtl-dce
	       Dump after the standalone dead code elimination passes.

	   -fdump-rtl-dbr
	       Dump after delayed branch scheduling.

	   -fdump-rtl-dce1
	   -fdump-rtl-dce2
	       -fdump-rtl-dce1	and  -fdump-rtl-dce2  enable dumping after the
	       two dead	store elimination passes.

	   -fdump-rtl-eh
	       Dump after finalization of EH handling code.

	   -fdump-rtl-eh_ranges
	       Dump after conversion of	EH handling range regions.

	   -fdump-rtl-expand
	       Dump after RTL generation.

	   -fdump-rtl-fwprop1
	   -fdump-rtl-fwprop2
	       -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable	dumping	 after
	       the two forward propagation passes.

	   -fdump-rtl-gcse1
	   -fdump-rtl-gcse2
	       -fdump-rtl-gcse1	 and  -fdump-rtl-gcse2	enable	dumping	 after
	       global common subexpression elimination.

	   -fdump-rtl-init-regs
	       Dump after the initialization of	the registers.

	   -fdump-rtl-initvals
	       Dump after the computation of the initial value sets.

	   -fdump-rtl-into_cfglayout
	       Dump after converting to	cfglayout mode.

	   -fdump-rtl-ira
	       Dump after iterated register allocation.

	   -fdump-rtl-jump
	       Dump after the second jump optimization.

	   -fdump-rtl-loop2
	       -fdump-rtl-loop2	  enables   dumping   after   the   rtl	  loop
	       optimization passes.

	   -fdump-rtl-mach
	       Dump  after  performing	the  machine  dependent	reorganization
	       pass, if	that pass exists.

	   -fdump-rtl-mode_sw
	       Dump after removing redundant mode switches.

	   -fdump-rtl-rnreg
	       Dump after register renumbering.

	   -fdump-rtl-outof_cfglayout
	       Dump after converting from cfglayout mode.

	   -fdump-rtl-peephole2
	       Dump after the peephole pass.

	   -fdump-rtl-postreload
	       Dump after post-reload optimizations.

	   -fdump-rtl-pro_and_epilogue
	       Dump after generating the function prologues and	epilogues.

	   -fdump-rtl-sched1
	   -fdump-rtl-sched2
	       -fdump-rtl-sched1 and -fdump-rtl-sched2	enable	dumping	 after
	       the basic block scheduling passes.

	   -fdump-rtl-ree
	       Dump after sign/zero extension elimination.

	   -fdump-rtl-seqabstr
	       Dump after common sequence discovery.

	   -fdump-rtl-shorten
	       Dump after shortening branches.

	   -fdump-rtl-sibling
	       Dump after sibling call optimizations.

	   -fdump-rtl-split1
	   -fdump-rtl-split2
	   -fdump-rtl-split3
	   -fdump-rtl-split4
	   -fdump-rtl-split5
	       These  options  enable dumping after five rounds	of instruction
	       splitting.

	   -fdump-rtl-sms
	       Dump after modulo scheduling.  This pass	is only	 run  on  some
	       architectures.

	   -fdump-rtl-stack
	       Dump after conversion from GCC's	"flat register file" registers
	       to  the	x87's  stack-like registers.  This pass	is only	run on
	       x86 variants.

	   -fdump-rtl-subreg1
	   -fdump-rtl-subreg2
	       -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable	dumping	 after
	       the two subreg expansion	passes.

	   -fdump-rtl-unshare
	       Dump after all rtl has been unshared.

	   -fdump-rtl-vartrack
	       Dump after variable tracking.

	   -fdump-rtl-vregs
	       Dump after converting virtual registers to hard registers.

	   -fdump-rtl-web
	       Dump after live range splitting.

	   -fdump-rtl-regclass
	   -fdump-rtl-subregs_of_mode_init
	   -fdump-rtl-subregs_of_mode_finish
	   -fdump-rtl-dfinit
	   -fdump-rtl-dfinish
	       These dumps are defined but always produce empty	files.

	   -da
	   -fdump-rtl-all
	       Produce all the dumps listed above.

	   -dA Annotate	 the  assembler	 output	 with  miscellaneous debugging
	       information.

	   -dD Dump all	macro definitions, at the  end	of  preprocessing,  in
	       addition	to normal output.

	   -dH Produce a core dump whenever an error occurs.

	   -dp Annotate	 the  assembler	output with a comment indicating which
	       pattern and alternative is used.	 The length and	cost  of  each
	       instruction are also printed.

	   -dP Dump  the  RTL in the assembler output as a comment before each
	       instruction.  Also turns	on -dp annotation.

	   -dx Just generate RTL for  a	 function  instead  of	compiling  it.
	       Usually used with -fdump-rtl-expand.

       -fdump-debug
	   Dump	 debugging  information	 generated during the debug generation
	   phase.

       -fdump-earlydebug
	   Dump	 debugging  information	 generated  during  the	 early	 debug
	   generation phase.

       -fdump-noaddr
	   When	doing debugging	dumps, suppress	address	output.	 This makes it
	   more	  feasible  to	use  diff  on  debugging  dumps	 for  compiler
	   invocations with different compiler binaries	and/or different  text
	   / bss / data	/ heap / stack / dso start locations.

       -freport-bug
	   Collect  and	 dump  debug  information  into	a temporary file if an
	   internal compiler error (ICE) occurs.

       -fdump-unnumbered
	   When	 doing	debugging  dumps,  suppress  instruction  numbers  and
	   address  output.   This  makes  it  more  feasible  to  use diff on
	   debugging dumps for compiler	invocations with different options, in
	   particular with and without -g.

       -fdump-unnumbered-links
	   When	 doing	debugging  dumps  (see	-d  option  above),   suppress
	   instruction	numbers	 for  the  links  to  the  previous  and  next
	   instructions	in a sequence.

       -fdump-ipa-switch
       -fdump-ipa-switch-options
	   Control the dumping at various stages of inter-procedural  analysis
	   language tree to a file.  The file name is generated	by appending a
	   switch  specific  suffix  to	 the source file name, and the file is
	   created in the same directory as the	output	file.	The  following
	   dumps are possible:

	   all Enables all inter-procedural analysis dumps.

	   cgraph
	       Dumps   information   about   call-graph	 optimization,	unused
	       function	removal, and inlining decisions.

	   inline
	       Dump after function inlining.

	   Additionally, the options -optimized, -missed, -note, and -all  can
	   be provided,	with the same meaning as for -fopt-info, defaulting to
	   -optimized.

	   For	  example,    -fdump-ipa-inline-optimized-missed   will	  emit
	   information on callsites that were inlined,	along  with  callsites
	   that	were not inlined.

	   By  default,	 the  dump  will  contain  messages  about  successful
	   optimizations (equivalent to	-optimized)  together  with  low-level
	   details about the analysis.

       -fdump-lang
	   Dump	 language-specific  information.   The	file  name  is made by
	   appending .lang to the source file name.

       -fdump-lang-all
       -fdump-lang-switch
       -fdump-lang-switch-options
       -fdump-lang-switch-options=filename
	   Control the dumping of language-specific information.  The  options
	   and	filename  portions  behave  as	described  in  the -fdump-tree
	   option.  The	following switch values	are accepted:

	   all Enable all language-specific dumps.

	   class
	       Dump class hierarchy information.  Virtual table	information is
	       emitted unless 'slim' is	specified.  This option	is  applicable
	       to C++ only.

	   module
	       Dump  module  information.   Options  lineno (locations), graph
	       (reachability), blocks (clusters), uid  (serialization),	 alias
	       (mergeable),  asmname (Elrond), eh (mapper) & vops (macros) may
	       provide additional information.	This option is	applicable  to
	       C++ only.

	   raw Dump  the raw internal tree data.  This option is applicable to
	       C++ only.

       -fdump-passes
	   Print on stderr the list of optimization passes that	are turned  on
	   and off by the current command-line options.

       -fdump-statistics-option
	   Enable  and	control	dumping	of pass	statistics in a	separate file.
	   The file  name  is  generated  by  appending	 a  suffix  ending  in
	   .statistics to the source file name,	and the	file is	created	in the
	   same	 directory  as	the output file.  If the -option form is used,
	   -stats causes counters to be	summed over the	whole compilation unit
	   while -details dumps	every event as the passes generate them.   The
	   default  with  no  option  is  to  sum  counters  for each function
	   compiled.

       -fdump-tree-all
       -fdump-tree-switch
       -fdump-tree-switch-options
       -fdump-tree-switch-options=filename
	   Control  the	 dumping  at  various	stages	 of   processing   the
	   intermediate	 language  tree	 to  a	file.  If the -options form is
	   used, options is a list of -	separated options  which  control  the
	   details  of the dump.  Not all options are applicable to all	dumps;
	   those that are not meaningful are ignored.  The  following  options
	   are available

	   address
	       Print the address of each node.	Usually	this is	not meaningful
	       as  it  changes	according  to the environment and source file.
	       Its primary use is for tying  up	 a  dump  file	with  a	 debug
	       environment.

	   asmname
	       If  "DECL_ASSEMBLER_NAME"  has  been  set for a given decl, use
	       that in the dump	instead	of "DECL_NAME".	 Its  primary  use  is
	       ease of use working backward from mangled names in the assembly
	       file.

	   slim
	       When  dumping  front-end	 intermediate representations, inhibit
	       dumping of members of a scope or	 body  of  a  function	merely
	       because that scope has been reached.  Only dump such items when
	       they are	directly reachable by some other path.

	       When dumping pretty-printed trees, this option inhibits dumping
	       the bodies of control structures.

	       When  dumping  RTL,  print  the	RTL  in	 slim (condensed) form
	       instead of the default LISP-like	representation.

	   raw Print a raw representation of the tree.	By default, trees  are
	       pretty-printed into a C-like representation.

	   details
	       Enable  more detailed dumps (not	honored	by every dump option).
	       Also include information	from the optimization passes.

	   stats
	       Enable dumping various statistics about the pass	 (not  honored
	       by every	dump option).

	   blocks
	       Enable showing basic block boundaries (disabled in raw dumps).

	   graph
	       For  each  of the other indicated dump files (-fdump-rtl-pass),
	       dump a representation of	the control flow  graph	 suitable  for
	       viewing	with  GraphViz to file.passid.pass.dot.	 Each function
	       in the file is pretty-printed as	a subgraph, so	that  GraphViz
	       can render them all in a	single plot.

	       This  option currently only works for RTL dumps,	and the	RTL is
	       always dumped in	slim form.

	   vops
	       Enable showing virtual operands for every statement.

	   lineno
	       Enable showing line numbers for statements.

	   uid Enable showing the unique ID ("DECL_UID") for each variable.

	   verbose
	       Enable showing the tree dump for	each statement.

	   eh  Enable showing the EH region number holding each	statement.

	   scev
	       Enable showing scalar evolution analysis	details.

	   optimized
	       Enable showing  optimization  information  (only	 available  in
	       certain passes).

	   missed
	       Enable  showing missed optimization information (only available
	       in certain passes).

	   note
	       Enable other detailed optimization information (only  available
	       in certain passes).

	   all Turn on all options, except raw,	slim, verbose and lineno.

	   optall
	       Turn  on	all optimization options, i.e.,	optimized, missed, and
	       note.

	   To determine	what tree dumps	are available or find the dump	for  a
	   pass	of interest follow the steps below.

	   1.  Invoke GCC with -fdump-passes and in the	stderr output look for
	       a code that corresponds to the pass you are interested in.  For
	       example,	 the  codes  "tree-evrp", "tree-vrp1", and "tree-vrp2"
	       correspond to the three Value Range  Propagation	 passes.   The
	       number  at  the	end  distinguishes distinct invocations	of the
	       same pass.

	   2.  To enable the creation of the dump file,	append the  pass  code
	       to  the	-fdump-	 option	 prefix	 and  invoke GCC with it.  For
	       example,	 to  enable  the  dump	from  the  Early  Value	 Range
	       Propagation  pass, invoke GCC with the -fdump-tree-evrp option.
	       Optionally, you may specify the name of the dump	file.  If  you
	       don't specify one, GCC creates as described below.

	   3.  Find  the  pass	dump in	a file whose name is composed of three
	       components separated by a period: the name of the  source  file
	       GCC  was	 invoked  to  compile, a numeric suffix	indicating the
	       pass number followed by the letter t for	tree passes  (and  the
	       letter  r  for  RTL  passes),  and  finally the pass code.  For
	       example,	the Early VRP pass dump	 might	be  in	a  file	 named
	       myfile.c.038t.evrp in the current working directory.  Note that
	       the  numeric  codes  are	 not  stable  and  may change from one
	       version of GCC to another.

       -fopt-info
       -fopt-info-options
       -fopt-info-options=filename
	   Controls optimization dumps from various  optimization  passes.  If
	   the	-options form is used, options is a list of - separated	option
	   keywords to select the dump details and optimizations.

	   The options can be divided into three groups:

	   1.  options describing what kinds of	messages should	be emitted,

	   2.  options describing the verbosity	of the dump, and

	   3.  options describing which	optimizations should be	included.

	   The options from each group can be freely mixed as  they  are  non-
	   overlapping.	 However,  in case of any conflicts, the later options
	   override the	earlier	options	on the command line.

	   The following options control which kinds  of  messages  should  be
	   emitted:

	   optimized
	       Print information when an optimization is successfully applied.
	       It is up	to a pass to decide which information is relevant. For
	       example,	 the  vectorizer  passes  print	the source location of
	       loops which are successfully vectorized.

	   missed
	       Print information about missed optimizations. Individual	passes
	       control which information to include in the output.

	   note
	       Print verbose information about optimizations, such as  certain
	       transformations,	more detailed messages about decisions etc.

	   all Print   detailed	  optimization	 information.	This  includes
	       optimized, missed, and note.

	   The following option	controls the dump verbosity:

	   internals
	       By default, only	"high-level" messages are emitted. This	option
	       enables additional, more	detailed, messages, which  are	likely
	       to only be of interest to GCC developers.

	   One	or  more  of  the  following  option  keywords	can be used to
	   describe a group of optimizations:

	   ipa Enable dumps from all interprocedural optimizations.

	   loop
	       Enable dumps from all loop optimizations.

	   inline
	       Enable dumps from all inlining optimizations.

	   omp Enable dumps from all OMP  (Offloading  and  Multi  Processing)
	       optimizations.

	   vec Enable dumps from all vectorization optimizations.

	   optall
	       Enable  dumps from all optimizations. This is a superset	of the
	       optimization groups listed above.

	   If options is omitted, it defaults to optimized-optall, which means
	   to dump  messages  about  successful	 optimizations	from  all  the
	   passes, omitting messages that are treated as "internals".

	   If the filename is provided,	then the dumps from all	the applicable
	   optimizations  are  concatenated  into the filename.	 Otherwise the
	   dump	is output onto stderr. Though multiple -fopt-info options  are
	   accepted,  only  one	 of  them  can	include	 a  filename. If other
	   filenames are provided then all  but	 the  first  such  option  are
	   ignored.

	   Note	 that  the  output filename is overwritten in case of multiple
	   translation units. If a combined output from	 multiple  translation
	   units is desired, stderr should be used instead.

	   In  the  following  example,	 the  optimization  info  is output to
	   stderr:

		   gcc -O3 -fopt-info

	   This	example:

		   gcc -O3 -fopt-info-missed=missed.all

	   outputs  missed  optimization  report  from	all  the  passes  into
	   missed.all, and this	one:

		   gcc -O2 -ftree-vectorize -fopt-info-vec-missed

	   prints  information	about  missed  optimization opportunities from
	   vectorization passes	on stderr.  Note that -fopt-info-vec-missed is
	   equivalent to -fopt-info-missed-vec.	 The order of the optimization
	   group names and message types  listed  after	 -fopt-info  does  not
	   matter.

	   As another example,

		   gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

	   outputs information about missed optimizations as well as optimized
	   locations from all the inlining passes into inline.txt.

	   Finally, consider:

		   gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

	   Here	the two	output filenames vec.miss and loop.opt are in conflict
	   since only one output file is allowed. In this case,	only the first
	   option  takes  effect  and the subsequent options are ignored. Thus
	   only	vec.miss is produced which contains dumps from the  vectorizer
	   about missed	opportunities.

       -fsave-optimization-record
	   Write    a	 SRCFILE.opt-record.json.gz    file   detailing	  what
	   optimizations were performed, for those optimizations that  support
	   -fopt-info.

	   This	 option	 is experimental and the format	of the data within the
	   compressed JSON file	is subject to change.

	   It  is  roughly  equivalent	to  a  machine-readable	  version   of
	   -fopt-info-all,  as a collection of messages	with source file, line
	   number and column number, with the following	 additional  data  for
	   each	message:

	   *   the  execution  count  of  the code being optimized, along with
	       metadata	about whether this was from actual  profile  data,  or
	       just  an	estimate, allowing consumers to	prioritize messages by
	       code hotness,

	   *   the  function  name  of	the  code   being   optimized,	 where
	       applicable,

	   *   the "inlining chain" for	the code being optimized, so that when
	       a  function  is	inlined	 into  several different places	(which
	       might  themselves  be  inlined),	 the  reader  can  distinguish
	       between the copies,

	   *   objects	identifying  those  parts of the message that refer to
	       expressions, statements or symbol-table nodes, which  of	 these
	       categories  they	 are,  and,  when available, their source code
	       location,

	   *   the GCC pass that emitted the message, and

	   *   the location in GCC's own  code	from  which  the  message  was
	       emitted

	   Additionally,  some	messages  are  logically  nested  within other
	   messages, reflecting	implementation	details	 of  the  optimization
	   passes.

       -fsched-verbose=n
	   On  targets	that  use instruction scheduling, this option controls
	   the amount of debugging output the scheduler	 prints	 to  the  dump
	   files.

	   For	 n   greater  than  zero,  -fsched-verbose  outputs  the  same
	   information as  -fdump-rtl-sched1  and  -fdump-rtl-sched2.	For  n
	   greater  than  one,	it  also  output  basic	 block	probabilities,
	   detailed ready list information and unit/insn info.	For n  greater
	   than	 two, it includes RTL at abort point, control-flow and regions
	   info.   And	for  n	over  four,  -fsched-verbose   also   includes
	   dependence info.

       -fenable-kind-pass
       -fdisable-kind-pass=range-list
	   This	is a set of options that are used to explicitly	disable/enable
	   optimization	 passes.   These  options  are	intended  for  use for
	   debugging GCC.  Compiler  users  should  use	 regular  options  for
	   enabling/disabling passes instead.

	   -fdisable-ipa-pass
	       Disable IPA pass	pass. pass is the pass name.  If the same pass
	       is  statically invoked in the compiler multiple times, the pass
	       name should be appended with a sequential number	starting  from
	       1.

	   -fdisable-rtl-pass
	   -fdisable-rtl-pass=range-list
	       Disable	RTL  pass  pass.   pass	is the pass name.  If the same
	       pass is statically invoked in the compiler multiple times,  the
	       pass  name should be appended with a sequential number starting
	       from 1.	range-list  is	a  comma-separated  list  of  function
	       ranges  or  assembler  names.   Each  range  is	a  number pair
	       separated by a colon.  The range	is inclusive in	both ends.  If
	       the range is trivial, the number	pair can be  simplified	 as  a
	       single  number.	 If the	function's call	graph node's uid falls
	       within one of the specified ranges, the pass  is	 disabled  for
	       that  function.	 The  uid is shown in the function header of a
	       dump file, and the pass names can be  dumped  by	 using	option
	       -fdump-passes.

	   -fdisable-tree-pass
	   -fdisable-tree-pass=range-list
	       Disable	tree pass pass.	 See -fdisable-rtl for the description
	       of option arguments.

	   -fenable-ipa-pass
	       Enable IPA pass pass.  pass is the pass name.  If the same pass
	       is statically invoked in	the compiler multiple times, the  pass
	       name  should be appended	with a sequential number starting from
	       1.

	   -fenable-rtl-pass
	   -fenable-rtl-pass=range-list
	       Enable RTL pass pass.  See -fdisable-rtl	 for  option  argument
	       description and examples.

	   -fenable-tree-pass
	   -fenable-tree-pass=range-list
	       Enable  tree  pass pass.	 See -fdisable-rtl for the description
	       of option arguments.

	   Here	are some examples showing uses of these	options.

		   # disable ccp1 for all functions
		      -fdisable-tree-ccp1
		   # disable complete unroll for function whose	cgraph node uid	is 1
		      -fenable-tree-cunroll=1
		   # disable gcse2 for functions at the	following ranges [1,1],
		   # [300,400],	and [400,1000]
		   # disable gcse2 for functions foo and foo2
		      -fdisable-rtl-gcse2=foo,foo2
		   # disable early inlining
		      -fdisable-tree-einline
		   # disable ipa inlining
		      -fdisable-ipa-inline
		   # enable tree full unroll
		      -fenable-tree-unroll

       -fchecking
       -fchecking=n
	   Enable internal consistency checking.  The default depends  on  the
	   compiler  configuration.   -fchecking=2  enables  further  internal
	   consistency checking	that might affect code generation.

       -frandom-seed=string
	   This	option provides	a seed	that  GCC  uses	 in  place  of	random
	   numbers  in	generating  certain  symbol  names  that  have	to  be
	   different in	every compiled file.  It is also used to place	unique
	   stamps  in  coverage	 data  files and the object files that produce
	   them.  You can use the -frandom-seed	option to produce reproducibly
	   identical object files.

	   The string can either be a number (decimal, octal  or  hex)	or  an
	   arbitrary  string  (in  which  case	it's  converted	to a number by
	   computing CRC32).

	   The string should be	different for every file you compile.

       -save-temps
	   Store the usual "temporary" intermediate  files  permanently;  name
	   them	 as  auxiliary	output	files,	as  specified  described under
	   -dumpbase and -dumpdir.

	   When	 used  in  combination	with  the  -x	command-line   option,
	   -save-temps is sensible enough to avoid overwriting an input	source
	   file	 with  the  same  extension  as	 an  intermediate  file.   The
	   corresponding intermediate file may be  obtained  by	 renaming  the
	   source file before using -save-temps.

       -save-temps=cwd
	   Equivalent to -save-temps -dumpdir ./.

       -save-temps=obj
	   Equivalent  to  -save-temps	-dumpdir outdir/, where	outdir/	is the
	   directory of	 the  output  file  specified  after  the  -o  option,
	   including  any directory separators.	 If the	-o option is not used,
	   the -save-temps=obj switch behaves like -save-temps=cwd.

       -time[=file]
	   Report the CPU time taken by	each  subprocess  in  the  compilation
	   sequence.   For  C  source  files,  this is the compiler proper and
	   assembler (plus the linker if linking is done).

	   Without the specification of	an output file,	the output looks  like
	   this:

		   # cc1 0.12 0.01
		   # as	0.00 0.01

	   The	first  number  on  each	 line is the "user time", that is time
	   spent executing the program itself.	The second number  is  "system
	   time",  time	spent executing	operating system routines on behalf of
	   the program.	 Both numbers are in seconds.

	   With	the specification of an	output file, the output	is appended to
	   the named file, and it looks	like this:

		   0.12	0.01 cc1 <options>
		   0.00	0.01 as	<options>

	   The "user time" and the "system time" are moved before the  program
	   name,  and the options passed to the	program	are displayed, so that
	   one can later tell what file	was being  compiled,  and  with	 which
	   options.

       -fdump-final-insns[=file]
	   Dump	 the  final  internal  representation  (RTL)  to file.	If the
	   optional argument is	omitted	(or if file is "."), the name  of  the
	   dump	 file is determined by appending ".gkd"	to the dump base name,
	   see -dumpbase.

       -fcompare-debug[=opts]
	   If no error occurs during compilation, run the  compiler  a	second
	   time,  adding  opts	and  -fcompare-debug-second  to	 the arguments
	   passed  to  the  second  compilation.   Dump	 the  final   internal
	   representation  in  both  compilations,  and	print an error if they
	   differ.

	   If the equal	sign is	omitted, the default -gtoggle is used.

	   The environment variable GCC_COMPARE_DEBUG, if  defined,  non-empty
	   and	  nonzero,    implicitly    enables    -fcompare-debug.	    If
	   GCC_COMPARE_DEBUG is	defined	to a string starting with a dash, then
	   it is used for opts,	otherwise the default -gtoggle is used.

	   -fcompare-debug=,  with  the	 equal	sign  but  without  opts,   is
	   equivalent to -fno-compare-debug, which disables the	dumping	of the
	   final  representation  and  the second compilation, preventing even
	   GCC_COMPARE_DEBUG from taking effect.

	   To  verify  full  coverage  during  -fcompare-debug	testing,   set
	   GCC_COMPARE_DEBUG  to say -fcompare-debug-not-overridden, which GCC
	   rejects as an invalid option	in any actual compilation (rather than
	   preprocessing, assembly  or	linking).   To	get  just  a  warning,
	   setting  GCC_COMPARE_DEBUG  to  -w%n-fcompare-debug	not overridden
	   will	do.

       -fcompare-debug-second
	   This	option is implicitly passed to the  compiler  for  the	second
	   compilation	requested  by  -fcompare-debug,	 along with options to
	   silence warnings, and omitting other	options	that would  cause  the
	   compiler to produce output to files or to standard output as	a side
	   effect.  Dump files and preserved temporary files are renamed so as
	   to  contain	the  ".gk"  additional	extension  during  the	second
	   compilation,	to avoid overwriting those generated by	the first.

	   When	this option is passed to the compiler driver,  it  causes  the
	   first  compilation  to be skipped, which makes it useful for	little
	   other than debugging	the compiler proper.

       -gtoggle
	   Turn	off generation of debug	 info,	if  leaving  out  this	option
	   generates  it, or turn it on	at level 2 otherwise.  The position of
	   this	argument in the	command	line does not matter; it takes	effect
	   after all other options are processed, and it does so only once, no
	   matter  how	many times it is given.	 This is mainly	intended to be
	   used	with -fcompare-debug.

       -fvar-tracking-assignments-toggle
	   Toggle -fvar-tracking-assignments, in the same  way	that  -gtoggle
	   toggles -g.

       -Q  Makes  the compiler print out each function name as it is compiled,
	   and print some statistics about each	pass when it finishes.

       -ftime-report
	   Makes the compiler print some statistics about the time consumed by
	   each	pass when it finishes.

       -ftime-report-details
	   Record the time consumed by	infrastructure	parts  separately  for
	   each	pass.

       -fira-verbose=n
	   Control  the	verbosity of the dump file for the integrated register
	   allocator.  The default value is 5.	If the value n is  greater  or
	   equal  to  10,  the	dump  output  is sent to stderr	using the same
	   format as n minus 10.

       -flto-report
	   Prints a report with	internal details on the	workings of the	 link-
	   time	 optimizer.   The contents of this report vary from version to
	   version.   It  is  meant  to	 be  useful  to	 GCC  developers  when
	   processing object files in LTO mode (via -flto).

	   Disabled by default.

       -flto-report-wpa
	   Like	 -flto-report,	but  only print	for the	WPA phase of link-time
	   optimization.

       -fmem-report
	   Makes the compiler print some  statistics  about  permanent	memory
	   allocation when it finishes.

       -fmem-report-wpa
	   Makes  the  compiler	 print	some statistics	about permanent	memory
	   allocation for the WPA phase	only.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
	   Makes the compiler print some  statistics  about  permanent	memory
	   allocation before or	after interprocedural optimization.

       -fprofile-report
	   Makes  the  compiler	print some statistics about consistency	of the
	   (estimated) profile and effect of individual	passes.

       -fstack-usage
	   Makes the compiler output stack usage information for the  program,
	   on  a  per-function	basis.	 The  filename for the dump is made by
	   appending .su to the	auxname.  auxname is generated from  the  name
	   of  the  output  file,  if  explicitly  specified  and it is	not an
	   executable, otherwise it is the basename of the  source  file.   An
	   entry is made up of three fields:

	   *   The name	of the function.

	   *   A number	of bytes.

	   *   One or more qualifiers: "static", "dynamic", "bounded".

	   The	qualifier  "static"  means  that  the function manipulates the
	   stack statically: a fixed number of bytes  are  allocated  for  the
	   frame  on  function	entry  and released on function	exit; no stack
	   adjustments are otherwise made in the function.  The	 second	 field
	   is this fixed number	of bytes.

	   The	qualifier  "dynamic"  means  that the function manipulates the
	   stack dynamically: in addition to the static	 allocation  described
	   above,  stack adjustments are made in the body of the function, for
	   example to  push/pop	 arguments  around  function  calls.   If  the
	   qualifier   "bounded"   is	also  present,	the  amount  of	 these
	   adjustments is bounded at compile time and the second field	is  an
	   upper  bound	of the total amount of stack used by the function.  If
	   it is not present, the amount of these adjustments is  not  bounded
	   at  compile	time  and the second field only	represents the bounded
	   part.

       -fstats
	   Emit	statistics about  front-end  processing	 at  the  end  of  the
	   compilation.	  This	option is supported only by the	C++ front end,
	   and the information is generally only useful	to the G++ development
	   team.

       -fdbg-cnt-list
	   Print the name and the counter upper	bound for all debug counters.

       -fdbg-cnt=counter-value-list
	   Set the internal debug counter lower	 and  upper  bound.   counter-
	   value-list	    is	     a	     comma-separated	  list	    of
	   name:lower_bound1-upper_bound1      [:lower_bound2-upper_bound2...]
	   tuples  which  sets	the  name  of  the  counter and	list of	closed
	   intervals.  The lower_bound is optional and is zero initialized  if
	   not	set.   For example, with -fdbg-cnt=dce:2-4:10-11,tail_call:10,
	   "dbg_cnt(dce)" returns true only for	second,	third,	fourth,	 tenth
	   and eleventh	invocation.  For "dbg_cnt(tail_call)" true is returned
	   for first 10	invocations.

       -print-file-name=library
	   Print the full absolute name	of the library file library that would
	   be  used  when  linking---and  don't	 do  anything else.  With this
	   option, GCC does not	compile	or link	anything; it just  prints  the
	   file	name.

       -print-multi-directory
	   Print  the directory	name corresponding to the multilib selected by
	   any other switches present in the command line.  This directory  is
	   supposed to exist in	GCC_EXEC_PREFIX.

       -print-multi-lib
	   Print  the  mapping	from  multilib	directory  names  to  compiler
	   switches that enable	them.  The directory name  is  separated  from
	   the	switches by ;, and each	switch starts with an @	instead	of the
	   -, without spaces between multiple switches.	 This is  supposed  to
	   ease	shell processing.

       -print-multi-os-directory
	   Print  the path to OS libraries for the selected multilib, relative
	   to some lib subdirectory.  If OS libraries are present in  the  lib
	   subdirectory	 and no	multilibs are used, this is usually just ., if
	   OS libraries	are present  in	 libsuffix  sibling  directories  this
	   prints  e.g.	 ../lib64,  ../lib or ../lib32,	or if OS libraries are
	   present in lib/subdir subdirectories	it prints e.g. amd64,  sparcv9
	   or ev6.

       -print-multiarch
	   Print the path to OS	libraries for the selected multiarch, relative
	   to some lib subdirectory.

       -print-prog-name=program
	   Like	-print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
	   Same	as -print-file-name=libgcc.a.

	   This	 is useful when	you use	-nostdlib or -nodefaultlibs but	you do
	   want	to link	with libgcc.a.	You can	do:

		   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
	   Print the name of the configured installation directory and a  list
	   of  program	and  library  directories  gcc searches---and don't do
	   anything else.

	   This	is useful when	gcc  prints  the  error	 message  installation
	   problem,  cannot  exec cpp0:	No such	file or	directory.  To resolve
	   this	you either need	to put cpp0 and	the other compiler  components
	   where  gcc  expects	to  find  them,	or you can set the environment
	   variable GCC_EXEC_PREFIX to the directory where you installed them.
	   Don't forget	the trailing /.

       -print-sysroot
	   Print the target sysroot directory that is used during compilation.
	   This	is the target sysroot specified	either at  configure  time  or
	   using  the  --sysroot  option,  possibly  with an extra suffix that
	   depends on compilation options.  If no target sysroot is specified,
	   the option prints nothing.

       -print-sysroot-headers-suffix
	   Print the suffix added to the target	 sysroot  when	searching  for
	   headers,  or	 give  an error	if the compiler	is not configured with
	   such	a suffix---and don't do	anything else.

       -dumpmachine
	   Print    the	   compiler's	 target	   machine    (for    example,
	   i686-pc-linux-gnu)---and don't do anything else.

       -dumpversion
	   Print  the  compiler	 version  (for example,	3.0, 6.3.0 or 7)---and
	   don't do anything else.  This  is  the  compiler  version  used  in
	   filesystem  paths and specs.	Depending on how the compiler has been
	   configured it can be	just a	single	number	(major	version),  two
	   numbers  separated  by  a  dot  (major  and minor version) or three
	   numbers separated by	dots (major, minor and patchlevel version).

       -dumpfullversion
	   Print the full compiler version---and don't do anything  else.  The
	   output  is always three numbers separated by	dots, major, minor and
	   patchlevel version.

       -dumpspecs
	   Print the compiler's	built-in specs---and don't do  anything	 else.
	   (This is used when GCC itself is being built.)

   Machine-Dependent Options
       Each  target  machine  supported	 by GCC	can have its own options---for
       example,	to allow you to	compile	for a particular processor variant  or
       ABI,  or	 to  control  optimizations  specific  to  that	 machine.   By
       convention, the names of	machine-specific options start with -m.

       Some configurations of the compiler  also  support  additional  target-
       specific	options, usually for compatibility with	other compilers	on the
       same platform.

       AArch64 Options

       These options are defined for AArch64 implementations:

       -mabi=name
	   Generate code for the specified data	model.	Permissible values are
	   ilp32 for SysV-like data model where	int, long int and pointers are
	   32  bits,  and  lp64	for SysV-like data model where int is 32 bits,
	   but long int	and pointers are 64 bits.

	   The default depends on the  specific	 target	 configuration.	  Note
	   that	 the  LP64  and	 ILP32	ABIs are not link-compatible; you must
	   compile your	entire program with the	same  ABI,  and	 link  with  a
	   compatible set of libraries.

       -mbig-endian
	   Generate  big-endian	 code.	 This  is  the	default	 when  GCC  is
	   configured for an aarch64_be-*-* target.

       -mgeneral-regs-only
	   Generate code which uses only the general-purpose registers.	  This
	   will	 prevent  the  compiler	from using floating-point and Advanced
	   SIMD	 registers  but	 will  not  impose  any	 restrictions  on  the
	   assembler.

       -mlittle-endian
	   Generate  little-endian  code.   This  is  the  default when	GCC is
	   configured for an aarch64-*-* but not an aarch64_be-*-* target.

       -mcmodel=tiny
	   Generate code for  the  tiny	 code  model.	The  program  and  its
	   statically  defined	symbols	 must  be  within  1MB	of each	other.
	   Programs can	be statically or dynamically linked.

       -mcmodel=small
	   Generate code for the  small	 code  model.	The  program  and  its
	   statically  defined	symbols	 must  be  within  4GB	of each	other.
	   Programs can	be statically or  dynamically  linked.	 This  is  the
	   default code	model.

       -mcmodel=large
	   Generate  code for the large	code model.  This makes	no assumptions
	   about addresses and sizes of	sections.  Programs can	be  statically
	   linked  only.   The	-mcmodel=large	option	is  incompatible  with
	   -mabi=ilp32,	-fpic and -fPIC.

       -mstrict-align
       -mno-strict-align
	   Avoid or allow generating memory accesses that may not  be  aligned
	   on  a  natural  object  boundary  as	 described in the architecture
	   specification.

       -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer
	   Omit	or keep	the frame  pointer  in	leaf  functions.   The	former
	   behavior is the default.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
	   Generate  stack  protection	code using canary at guard.  Supported
	   locations are global	for a global canary or sysreg for a canary  in
	   an appropriate system register.

	   With	 the latter choice the options -mstack-protector-guard-reg=reg
	   and -mstack-protector-guard-offset=offset furthermore specify which
	   system register to use as base register for reading the canary, and
	   from	what offset from that  base  register.	There  is  no  default
	   register  or	 offset	 as  this is entirely for use within the Linux
	   kernel.

       -mtls-dialect=desc
	   Use TLS descriptors	as  the	 thread-local  storage	mechanism  for
	   dynamic accesses of TLS variables.  This is the default.

       -mtls-dialect=traditional
	   Use	traditional  TLS  as  the  thread-local	 storage mechanism for
	   dynamic accesses of TLS variables.

       -mtls-size=size
	   Specify bit size of immediate TLS offsets.  Valid  values  are  12,
	   24, 32, 48.	This option requires binutils 2.26 or newer.

       -mfix-cortex-a53-835769
       -mno-fix-cortex-a53-835769
	   Enable  or  disable	the  workaround	for the	ARM Cortex-A53 erratum
	   number 835769.  This	involves inserting a NOP  instruction  between
	   memory   instructions   and	 64-bit	  integer  multiply-accumulate
	   instructions.

       -mfix-cortex-a53-843419
       -mno-fix-cortex-a53-843419
	   Enable or disable the workaround for	 the  ARM  Cortex-A53  erratum
	   number  843419.   This  erratum workaround is made at link time and
	   this	will only pass the corresponding flag to the linker.

       -mlow-precision-recip-sqrt
       -mno-low-precision-recip-sqrt
	   Enable or disable the reciprocal square root	 approximation.	  This
	   option     only     has     an    effect    if    -ffast-math    or
	   -funsafe-math-optimizations is used as well.	 Enabling this reduces
	   precision of	reciprocal square root results to about	 16  bits  for
	   single precision and	to 32 bits for double precision.

       -mlow-precision-sqrt
       -mno-low-precision-sqrt
	   Enable  or disable the square root approximation.  This option only
	   has an effect if -ffast-math	or -funsafe-math-optimizations is used
	   as well.  Enabling this reduces precision of	square root results to
	   about 16 bits for single  precision	and  to	 32  bits  for	double
	   precision.  If enabled, it implies -mlow-precision-recip-sqrt.

       -mlow-precision-div
       -mno-low-precision-div
	   Enable or disable the division approximation.  This option only has
	   an  effect if -ffast-math or	-funsafe-math-optimizations is used as
	   well.  Enabling this	reduces	precision of division results to about
	   16 bits for single precision	and to 32 bits for double precision.

       -mtrack-speculation
       -mno-track-speculation
	   Enable  or  disable	generation  of	additional   code   to	 track
	   speculative	execution  through conditional branches.  The tracking
	   state can then be used by the  compiler  when  expanding  calls  to
	   "__builtin_speculation_safe_copy"  to  permit a more	efficient code
	   sequence to be generated.

       -moutline-atomics
       -mno-outline-atomics
	   Enable or disable calls to out-of-line helpers to implement	atomic
	   operations.	 These	helpers	will, at runtime, determine if the LSE
	   instructions	from ARMv8.1-A can be used; if not, they will use  the
	   load/store-exclusive	 instructions  that  are  present  in the base
	   ARMv8.0 ISA.

	   This	option is only applicable when compiling for the base  ARMv8.0
	   instruction	set.  If using a later revision, e.g. -march=armv8.1-a
	   or -march=armv8-a+lse, the  ARMv8.1-Atomics	instructions  will  be
	   used	 directly.   The  same	applies	 when  using  -mcpu=  when the
	   selected cpu	supports the  lse  feature.   This  option  is	on  by
	   default.

       -march=name
	   Specify the name of the target architecture and, optionally,	one or
	   more	   feature    modifiers.     This    option   has   the	  form
	   -march=arch{+[no]feature}*.

	   The table below summarizes the permissible values for arch and  the
	   features that they enable by	default:

	   arch	value :	Architecture : Includes	by default
	   armv8-a : Armv8-A : +fp, +simd
	   armv8.1-a : Armv8.1-A : armv8-a, +crc, +lse,	+rdma
	   armv8.2-a : Armv8.2-A : armv8.1-a
	   armv8.3-a : Armv8.3-A : armv8.2-a, +pauth
	   armv8.4-a : Armv8.4-A : armv8.3-a, +flagm, +fp16fml,	+dotprod
	   armv8.5-a : Armv8.5-A : armv8.4-a, +sb, +ssbs, +predres
	   armv8.6-a : Armv8.6-A : armv8.5-a, +bf16, +i8mm
	   armv8-r : Armv8-R : armv8-r

	   The	value  native  is  available  on  native AArch64 GNU/Linux and
	   causes the compiler to pick the architecture	of  the	 host  system.
	   This	 option	 has  no effect	if the compiler	is unable to recognize
	   the architecture of the host	system,

	   The permissible values for feature are listed in the	sub-section on
	   aarch64-feature-modifiers,,-march  and  -mcpu  Feature   Modifiers.
	   Where  conflicting  feature modifiers are specified,	the right-most
	   feature is used.

	   GCC uses name to determine what kind	of instructions	 it  can  emit
	   when	 generating  assembly  code.   If  -march is specified without
	   either of -mtune or -mcpu also being	specified, the code  is	 tuned
	   to  perform	well  across a range of	target processors implementing
	   the target architecture.

       -mtune=name
	   Specify the name of the target processor for	which GCC should  tune
	   the	performance  of	 the code.  Permissible	values for this	option
	   are:	 generic,  cortex-a35,	cortex-a53,  cortex-a55,   cortex-a57,
	   cortex-a72,	 cortex-a73,   cortex-a75,  cortex-a76,	 cortex-a76ae,
	   cortex-a77,	cortex-a65,  cortex-a65ae,   cortex-a34,   cortex-a78,
	   cortex-a78ae,   cortex-a78c,	  ares,	  exynos-m1,   emag,   falkor,
	   neoverse-512tvb,	neoverse-e1,	 neoverse-n1,	  neoverse-n2,
	   neoverse-v1,neoverse-v2,  grace,  qdf24xx, saphira, phecda, xgene1,
	   vulcan, octeontx, octeontx81,  octeontx83, octeontx2, octeontx2t98,
	   octeontx2t96	    octeontx2t93,     octeontx2f95,	octeontx2f95n,
	   octeontx2f95mm,   a64fx,   thunderx,	  thunderxt88,	thunderxt88p1,
	   thunderxt81,	 tsv110,  thunderxt83,	thunderx2t99,	thunderx3t110,
	   zeus,	 cortex-a57.cortex-a53,		cortex-a72.cortex-a53,
	   cortex-a73.cortex-a35,			cortex-a73.cortex-a53,
	   cortex-a75.cortex-a55,      cortex-a76.cortex-a55,	   cortex-r82,
	   cortex-x1, ampere1, ampere1a, cobalt-100 and	native.

	   The	  values     cortex-a57.cortex-a53,	cortex-a72.cortex-a53,
	   cortex-a73.cortex-a35,			cortex-a73.cortex-a53,
	   cortex-a75.cortex-a55,  cortex-a76.cortex-a55  specify   that   GCC
	   should tune for a big.LITTLE	system.

	   The	value  neoverse-512tvb	specifies  that	 GCC  should  tune for
	   Neoverse cores that (a) implement SVE and (b) have a	 total	vector
	   bandwidth  of 512 bits per cycle.  In other words, the option tells
	   GCC to tune for Neoverse cores that can execute 4 128-bit  Advanced
	   SIMD	 arithmetic  instructions  a  cycle  and  that	can execute an
	   equivalent number of	SVE arithmetic instructions per	cycle  (2  for
	   256-bit  SVE, 4 for 128-bit SVE).  This is more general than	tuning
	   for a specific core like Neoverse V1	but is more specific than  the
	   default tuning described below.

	   Additionally	 on  native AArch64 GNU/Linux systems the value	native
	   tunes performance to	the host system.  This option has no effect if
	   the compiler	is unable to  recognize	 the  processor	 of  the  host
	   system.

	   Where none of -mtune=, -mcpu= or -march= are	specified, the code is
	   tuned to perform well across	a range	of target processors.

	   This	option cannot be suffixed by feature modifiers.

       -mcpu=name
	   Specify  the	 name  of the target processor,	optionally suffixed by
	   one	or  more  feature  modifiers.	This  option  has   the	  form
	   -mcpu=cpu{+[no]feature}*,  where the	permissible values for cpu are
	   the same as those available for -mtune.  The	permissible values for
	   feature    are     documented     in	    the	    sub-section	    on
	   aarch64-feature-modifiers,,-march   and  -mcpu  Feature  Modifiers.
	   Where conflicting feature modifiers are specified,  the  right-most
	   feature is used.

	   GCC	uses  name  to determine what kind of instructions it can emit
	   when	generating assembly code (as if	by -march)  and	 to  determine
	   the	target	processor  for which to	tune for performance (as if by
	   -mtune).  Where this	option is used in conjunction with  -march  or
	   -mtune,  those options take precedence over the appropriate part of
	   this	option.

	   -mcpu=neoverse-512tvb is special in that it does  not  refer	 to  a
	   specific  core,  but	 instead refers	to all Neoverse	cores that (a)
	   implement SVE and (b) have a	total vector bandwidth of 512  bits  a
	   cycle.    Unless   overridden   by	-march,	 -mcpu=neoverse-512tvb
	   generates code that can run on a Neoverse V1	core,  since  Neoverse
	   V1  is  the	first  Neoverse	 core  with  these properties.	Unless
	   overridden by -mtune, -mcpu=neoverse-512tvb tunes code in the  same
	   way as for -mtune=neoverse-512tvb.

       -moverride=string
	   Override  tuning  decisions	made  by the back-end in response to a
	   -mtune= switch.  The	syntax,	semantics,  and	 accepted  values  for
	   string  in  this  option are	not guaranteed to be consistent	across
	   releases.

	   This	option is only intended	to be useful when developing GCC.

       -mverbose-cost-dump
	   Enable verbose cost model dumping in	the debug  dump	 files.	  This
	   option is provided for use in debugging the compiler.

       -mpc-relative-literal-loads
       -mno-pc-relative-literal-loads
	   Enable  or  disable	PC-relative  literal  loads.  With this	option
	   literal pools are accessed using a single instruction  and  emitted
	   after  each function.  This limits the maximum size of functions to
	   1MB.	 This is enabled by default for	-mcmodel=tiny.

       -msign-return-address=scope
	   Select the function scope on	which return address signing  will  be
	   applied.   Permissible  values  are	none,  which  disables	return
	   address  signing,  non-leaf,	 which	enables	 pointer  signing  for
	   functions  which  are  not  leaf  functions,	and all, which enables
	   pointer signing for all functions.  The default value is none. This
	   option has been deprecated by -mbranch-protection.

       -mbranch-protection=none|standard|pac-ret[+leaf+b-key]|bti
	   Select the branch protection	features to use.  none is the  default
	   and	turns  off  all	types of branch	protection.  standard turns on
	   all	types  of  branch  protection  features.   If  a  feature  has
	   additional  tuning  options,	 then standard sets it to its standard
	   level.  pac-ret[+leaf] turns	 on  return  address  signing  to  its
	   standard  level:  signing functions that save the return address to
	   memory (non-leaf functions will practically always do  this)	 using
	   the	a-key.	 The  optional argument	leaf can be used to extend the
	   signing to include leaf functions.  The optional argument b-key can
	   be used to sign the functions with the B-key	instead	of the	A-key.
	   bti turns on	branch target identification mechanism.

       -mharden-sls=opts
	   Enable  compiler hardening against straight line speculation	(SLS).
	   opts	is a comma-separated list of the following options:

	   retbr
	   blr

	   In addition,	 -mharden-sls=all  enables  all	 SLS  hardening	 while
	   -mharden-sls=none disables all SLS hardening.

       -msve-vector-bits=bits
	   Specify  the	number of bits in an SVE vector	register.  This	option
	   only	has an effect when SVE is enabled.

	   GCC supports	two  forms  of	SVE  code  generation:	"vector-length
	   agnostic"  output  that  works with any size	of vector register and
	   "vector-length specific" output that	allows GCC to make assumptions
	   about the vector length when	it is useful for optimization reasons.
	   The possible	values of bits are: scalable, 128, 256,	512, 1024  and
	   2048.   Specifying  scalable	selects	vector-length agnostic output.
	   At  present	-msve-vector-bits=128  also  generates	 vector-length
	   agnostic  output for	big-endian targets.  All other values generate
	   vector-length specific code.	 The  behavior	of  these  values  may
	   change  in  future  releases	and no value except scalable should be
	   relied on for producing code	 that  is  portable  across  different
	   hardware SVE	vector lengths.

	   The	default	 is -msve-vector-bits=scalable,	which produces vector-
	   length agnostic code.

       -march and -mcpu	Feature	Modifiers

       Feature modifiers used  with  -march  and  -mcpu	 can  be  any  of  the
       following and their inverses nofeature:

       crc Enable CRC extension.  This is on by	default	for -march=armv8.1-a.

       crypto
	   Enable  Crypto  extension.	This  also  enables  Advanced SIMD and
	   floating-point instructions.

       fp  Enable floating-point instructions.	This is	on by default for  all
	   possible values for options -march and -mcpu.

       simd
	   Enable  Advanced  SIMD  instructions.   This	also enables floating-
	   point instructions.	This is	on by default for all possible	values
	   for options -march and -mcpu.

       sve Enable  Scalable  Vector Extension instructions.  This also enables
	   Advanced SIMD and floating-point instructions.

       lse Enable Large	System Extension instructions.	This is	on by  default
	   for -march=armv8.1-a.

       rdma
	   Enable  Round  Double Multiply Accumulate instructions.  This is on
	   by default for -march=armv8.1-a.

       fp16
	   Enable  FP16	  extension.	This   also   enables	floating-point
	   instructions.

       fp16fml
	   Enable  FP16	fmla extension.	 This also enables FP16	extensions and
	   floating-point instructions.	This option is enabled by default  for
	   -march=armv8.4-a.  Use  of  this option with	architectures prior to
	   Armv8.2-A is	not supported.

       rcpc
	   Enable the RcPc extension.  This does not  change  code  generation
	   from	 GCC,  but  is passed on to the	assembler, enabling inline asm
	   statements to use instructions from the RcPc	extension.

       dotprod
	   Enable the Dot Product extension.  This also	enables	Advanced  SIMD
	   instructions.

       aes Enable  the	Armv8-a	 aes  and  pmull  crypto extension.  This also
	   enables Advanced SIMD instructions.

       sha2
	   Enable the  Armv8-a	sha2  crypto  extension.   This	 also  enables
	   Advanced SIMD instructions.

       sha3
	   Enable  the	sha512	and  sha3 crypto extension.  This also enables
	   Advanced SIMD instructions. Use of this option  with	 architectures
	   prior to Armv8.2-A is not supported.

       sm4 Enable  the	sm3  and  sm4  crypto  extension.   This  also enables
	   Advanced SIMD instructions.	Use of this option with	 architectures
	   prior to Armv8.2-A is not supported.

       profile
	   Enable the Statistical Profiling extension.	This option is only to
	   enable  the	extension  at  the assembler level and does not	affect
	   code	generation.

       rng Enable the Armv8.5-a	Random Number instructions.   This  option  is
	   only	 to  enable  the extension at the assembler level and does not
	   affect code generation.

       memtag
	   Enable the Armv8.5-a	Memory Tagging Extensions.  Use	of this	option
	   with	architectures prior to Armv8.5-A is not	supported.

       sb  Enable the Armv8-a Speculation Barrier instruction.	This option is
	   only	to enable the extension	at the assembler level	and  does  not
	   affect  code	 generation.   This  option  is	enabled	by default for
	   -march=armv8.5-a.

       ssbs
	   Enable the Armv8-a Speculative Store	Bypass Safe instruction.  This
	   option is only to enable the	extension at the assembler  level  and
	   does	not affect code	generation.  This option is enabled by default
	   for -march=armv8.5-a.

       predres
	   Enable  the	Armv8-a	 Execution  and	 Data  Prediction  Restriction
	   instructions.  This option is only to enable	the extension  at  the
	   assembler  level  and does not affect code generation.  This	option
	   is enabled by default for -march=armv8.5-a.

       sve2
	   Enable the Armv8-a Scalable Vector Extension	2.  This also  enables
	   SVE instructions.

       sve2-bitperm
	   Enable   SVE2   bitperm   instructions.   This  also	 enables  SVE2
	   instructions.

       sve2-sm4
	   Enable SVE2 sm4 instructions.  This also enables SVE2 instructions.

       sve2-aes
	   Enable SVE2 aes instructions.  This also enables SVE2 instructions.

       sve2-sha3
	   Enable  SVE2	  sha3	 instructions.	  This	 also	enables	  SVE2
	   instructions.

       tme Enable the Transactional Memory Extension.

       i8mm
	   Enable  8-bit  Integer  Matrix  Multiply  instructions.   This also
	   enables Advanced SIMD and floating-point instructions.  This	option
	   is enabled by default for -march=armv8.6-a.	 Use  of  this	option
	   with	architectures prior to Armv8.2-A is not	supported.

       f32mm
	   Enable  32-bit  Floating  point Matrix Multiply instructions.  This
	   also	 enables  SVE  instructions.   Use   of	  this	 option	  with
	   architectures prior to Armv8.2-A is not supported.

       f64mm
	   Enable  64-bit  Floating  point Matrix Multiply instructions.  This
	   also	 enables  SVE  instructions.   Use   of	  this	 option	  with
	   architectures prior to Armv8.2-A is not supported.

       bf16
	   Enable brain	half-precision floating-point instructions.  This also
	   enables Advanced SIMD and floating-point instructions.  This	option
	   is  enabled	by  default  for -march=armv8.6-a.  Use	of this	option
	   with	architectures prior to Armv8.2-A is not	supported.

       flagm
	   Enable the Flag Manipulation	instructions Extension.

       pauth
	   Enable the Pointer Authentication Extension.

       Feature	crypto	implies	 aes,  sha2,  and  simd,  which	 implies   fp.
       Conversely,  nofp  implies  nosimd,  which  implies nocrypto, noaes and
       nosha2.

       Adapteva	Epiphany Options

       These -m	options	are defined for	Adapteva Epiphany:

       -mhalf-reg-file
	   Don't allocate any  register	 in  the  range	 "r32"..."r63".	  That
	   allows code to run on hardware variants that	lack these registers.

       -mprefer-short-insn-regs
	   Preferentially  allocate  registers	that  allow  short instruction
	   generation.	This can result	in  increased  instruction  count,  so
	   this	may either reduce or increase overall code size.

       -mbranch-cost=num
	   Set	the  cost  of  branches	 to roughly num	"simple" instructions.
	   This	cost is	only a heuristic and  is  not  guaranteed  to  produce
	   consistent results across releases.

       -mcmove
	   Enable the generation of conditional	moves.

       -mnops=num
	   Emit	num NOPs before	every other generated instruction.

       -mno-soft-cmpsf
	   For	single-precision  floating-point  comparisons,	emit an	"fsub"
	   instruction and test	the flags.  This is  faster  than  a  software
	   comparison,	but can	get incorrect results in the presence of NaNs,
	   or when two different small numbers are compared  such  that	 their
	   difference  is  calculated  as  zero.  The default is -msoft-cmpsf,
	   which uses slower, but IEEE-compliant, software comparisons.

       -mstack-offset=num
	   Set the offset between the top of the stack and the stack  pointer.
	   E.g.,  a  value  of	8  means  that	the  eight  bytes in the range
	   "sp+0...sp+7"  can  be  used	 by  leaf  functions   without	 stack
	   allocation.	Values other than 8 or 16 are untested and unlikely to
	   work.   Note	 also  that  this  option changes the ABI; compiling a
	   program with	a different stack offset than the libraries have  been
	   compiled  with  generally does not work.  This option can be	useful
	   if you want to evaluate if a	different stack	offset would give  you
	   better  code, but to	actually use a different stack offset to build
	   working programs, it	is recommended to configure the	toolchain with
	   the appropriate --with-stack-offset=num option.

       -mno-round-nearest
	   Make	the scheduler assume that the rounding mode has	 been  set  to
	   truncating.	The default is -mround-nearest.

       -mlong-calls
	   If  not otherwise specified by an attribute,	assume all calls might
	   be beyond the offset	range of the  "b"  /  "bl"  instructions,  and
	   therefore   load  the  function  address  into  a  register	before
	   performing a	(otherwise direct) call.  This is the default.

       -mshort-calls
	   If not otherwise specified by an attribute, assume all direct calls
	   are in the range of the "b"	/  "bl"	 instructions,	so  use	 these
	   instructions	for direct calls.  The default is -mlong-calls.

       -msmall16
	   Assume  addresses  can  be  loaded as 16-bit	unsigned values.  This
	   does	 not  apply  to	 function  addresses  for  which  -mlong-calls
	   semantics are in effect.

       -mfp-mode=mode
	   Set	 the   prevailing  mode	 of  the  floating-point  unit.	  This
	   determines the floating-point mode that is provided and expected at
	   function call and return time.  Making this mode match the mode you
	   predominantly need at function start	can make your programs smaller
	   and faster by avoiding unnecessary mode switches.

	   mode	can be set to one the following	values:

	   caller
	       Any mode	at function entry is valid, and	retained  or  restored
	       when  the  function returns, and	when it	calls other functions.
	       This  mode  is  useful  for  compiling	libraries   or	 other
	       compilation  units you might want to incorporate	into different
	       programs	 with  different  prevailing  FPU   modes,   and   the
	       convenience of being able to use	a single object	file outweighs
	       the  size  and speed overhead for any extra mode	switching that
	       might be	needed,	compared with what would be needed with	a more
	       specific	choice of prevailing FPU mode.

	   truncate
	       This is the mode	 used  for  floating-point  calculations  with
	       truncating  (i.e.  round	 towards  zero)	 rounding  mode.  That
	       includes	conversion from	floating point to integer.

	   round-nearest
	       This is the mode	 used  for  floating-point  calculations  with
	       round-to-nearest-or-even	rounding mode.

	   int This  is	 the  mode used	to perform integer calculations	in the
	       FPU,  e.g.   integer   multiply,	  or   integer	 multiply-and-
	       accumulate.

	   The default is -mfp-mode=caller

       -mno-split-lohi
       -mno-postinc
       -mno-postmodify
	   Code	 generation  tweaks  that  disable, respectively, splitting of
	   32-bit  loads,  generation	of   post-increment   addresses,   and
	   generation of post-modify addresses.	 The defaults are msplit-lohi,
	   -mpost-inc, and -mpost-modify.

       -mnovect-double
	   Change   the	 preferred  SIMD  mode	to  SImode.   The  default  is
	   -mvect-double, which	uses DImode as preferred SIMD mode.

       -max-vect-align=num
	   The maximum alignment for SIMD vector mode types.  num may be 4  or
	   8.  The default is 8.  Note that this is an ABI change, even	though
	   many	 library  function interfaces are unaffected if	they don't use
	   SIMD	vector modes in	places that affect size	 and/or	 alignment  of
	   relevant types.

       -msplit-vecmove-early
	   Split vector	moves into single word moves before reload.  In	theory
	   this	 can  give  better register allocation,	but so far the reverse
	   seems to be generally the case.

       -m1reg-reg
	   Specify a register to hold the constant  -1,	 which	makes  loading
	   small  negative  constants  and certain bitmasks faster.  Allowable
	   values for reg are r43 and r63, which specify use of	that  register
	   as a	fixed register,	and none, which	means that no register is used
	   for this purpose.  The default is -m1reg-none.

       AMD GCN Options

       These options are defined specifically for the AMD GCN port.

       -march=gpu
       -mtune=gpu
	   Set	architecture  type or tuning for gpu. Supported	values for gpu
	   are

	   fiji
	       Compile for GCN3	Fiji devices (gfx803).

	   gfx900
	       Compile for GCN5	Vega 10	devices	(gfx900).

	   gfx906
	       Compile for GCN5	Vega 20	devices	(gfx906).

       -msram-ecc=on
       -msram-ecc=off
       -msram-ecc=any
	   Compile binaries suitable for devices  with	the  SRAM-ECC  feature
	   enabled,  disabled,	or  either  mode.  This	feature	can be enabled
	   per-process on some devices.	 The  compiled	code  must  match  the
	   device mode.	The default is any, for	devices	that support it.

       -mstack-size=bytes
	   Specify  how	 many  bytes of	stack space will be requested for each
	   GPU thread (wave-front).  Beware that there may be many threads and
	   limited memory available.  The size of  the	stack  allocation  may
	   also	 have  an impact on run-time performance.  The default is 32KB
	   when	using OpenACC or OpenMP, and 1MB otherwise.

       -mxnack
	   Compile binaries  suitable  for  devices  with  the	XNACK  feature
	   enabled.  Some devices always require XNACK and some	allow the user
	   to  configure XNACK.	 The compiled code must	match the device mode.
	   The default is -mno-xnack.  At present this option is a placeholder
	   for support that is not yet implemented.

       ARC Options

       The following options control the architecture variant for  which  code
       is being	compiled:

       -mbarrel-shifter
	   Generate  instructions  supported  by  barrel shifter.  This	is the
	   default unless -mcpu=ARC601 or -mcpu=ARCEM is in effect.

       -mjli-always
	   Force to call a function using jli_s	instruction.  This  option  is
	   valid only for ARCv2	architecture.

       -mcpu=cpu
	   Set	architecture  type, register usage, and	instruction scheduling
	   parameters  for  cpu.   There  are  also  shortcut  alias   options
	   available  for  backward  compatibility and convenience.  Supported
	   values for cpu are

	   arc600
	       Compile for ARC600.  Aliases: -mA6, -mARC600.

	   arc601
	       Compile for ARC601.  Alias: -mARC601.

	   arc700
	       Compile for ARC700.  Aliases:  -mA7,  -mARC700.	 This  is  the
	       default when configured with --with-cpu=arc700.

	   arcem
	       Compile for ARC EM.

	   archs
	       Compile for ARC HS.

	   em  Compile for ARC EM CPU with no hardware extensions.

	   em4 Compile for ARC EM4 CPU.

	   em4_dmips
	       Compile for ARC EM4 DMIPS CPU.

	   em4_fpus
	       Compile	for  ARC  EM4  DMIPS  CPU  with	 the  single-precision
	       floating-point extension.

	   em4_fpuda
	       Compile for ARC EM4 DMIPS CPU with  single-precision  floating-
	       point and double	assist instructions.

	   hs  Compile	for  ARC HS CPU	with no	hardware extensions except the
	       atomic instructions.

	   hs34
	       Compile for ARC HS34 CPU.

	   hs38
	       Compile for ARC HS38 CPU.

	   hs38_linux
	       Compile for ARC HS38 CPU	with all hardware extensions on.

	   arc600_norm
	       Compile for ARC 600 CPU with "norm" instructions	enabled.

	   arc600_mul32x16
	       Compile for ARC 600 CPU	with  "norm"  and  32x16-bit  multiply
	       instructions enabled.

	   arc600_mul64
	       Compile	 for  ARC  600	CPU  with  "norm"  and	"mul64"-family
	       instructions enabled.

	   arc601_norm
	       Compile for ARC 601 CPU with "norm" instructions	enabled.

	   arc601_mul32x16
	       Compile for ARC 601 CPU	with  "norm"  and  32x16-bit  multiply
	       instructions enabled.

	   arc601_mul64
	       Compile	 for  ARC  601	CPU  with  "norm"  and	"mul64"-family
	       instructions enabled.

	   nps400
	       Compile for ARC 700 on NPS400 chip.

	   em_mini
	       Compile for ARC EM minimalist configuration  featuring  reduced
	       register	set.

       -mdpfp
       -mdpfp-compact
	   Generate  double-precision  FPX instructions, tuned for the compact
	   implementation.

       -mdpfp-fast
	   Generate double-precision FPX  instructions,	 tuned	for  the  fast
	   implementation.

       -mno-dpfp-lrsr
	   Disable  "lr"  and  "sr"  instructions from using FPX extension aux
	   registers.

       -mea
	   Generate extended arithmetic	instructions.  Currently only "divaw",
	   "adds",  "subs",  and  "sat16"  are	supported.   Only  valid   for
	   -mcpu=ARC700.

       -mno-mpy
	   Do  not generate "mpy"-family instructions for ARC700.  This	option
	   is deprecated.

       -mmul32x16
	   Generate 32x16-bit multiply and multiply-accumulate instructions.

       -mmul64
	   Generate  "mul64"  and  "mulu64"  instructions.   Only  valid   for
	   -mcpu=ARC600.

       -mnorm
	   Generate  "norm" instructions.  This	is the default if -mcpu=ARC700
	   is in effect.

       -mspfp
       -mspfp-compact
	   Generate single-precision FPX instructions, tuned for  the  compact
	   implementation.

       -mspfp-fast
	   Generate  single-precision  FPX  instructions,  tuned  for the fast
	   implementation.

       -msimd
	   Enable generation of	 ARC  SIMD  instructions  via  target-specific
	   builtins.  Only valid for -mcpu=ARC700.

       -msoft-float
	   This	 option	 ignored;  it  is  provided for	compatibility purposes
	   only.  Software floating-point code is emitted by default, and this
	   default can overridden by FPX options; -mspfp,  -mspfp-compact,  or
	   -mspfp-fast	for  single  precision,	and -mdpfp, -mdpfp-compact, or
	   -mdpfp-fast for double precision.

       -mswap
	   Generate "swap" instructions.

       -matomic
	   This	enables	use of the locked load/store conditional extension  to
	   implement  atomic memory built-in functions.	 Not available for ARC
	   6xx or ARC EM cores.

       -mdiv-rem
	   Enable "div"	and "rem" instructions for ARCv2 cores.

       -mcode-density
	   Enable code density instructions for	ARC EM.	 This option is	on  by
	   default for ARC HS.

       -mll64
	   Enable double load/store operations for ARC HS cores.

       -mtp-regno=regno
	   Specify thread pointer register number.

       -mmpy-option=multo
	   Compile  ARCv2  code	 with  a  multiplier  design  option.  You can
	   specify the option using either  a  string  or  numeric  value  for
	   multo.  wlh1	is the default value.  The recognized values are:

	   0
	   none
	       No multiplier available.

	   1
	   w   16x16  multiplier, fully	pipelined.  The	following instructions
	       are enabled: "mpyw" and "mpyuw".

	   2
	   wlh1
	       32x32 multiplier, fully pipelined  (1  stage).	The  following
	       instructions  are  additionally enabled:	"mpy", "mpyu", "mpym",
	       "mpymu",	and "mpy_s".

	   3
	   wlh2
	       32x32 multiplier, fully pipelined (2  stages).	The  following
	       instructions  are  additionally enabled:	"mpy", "mpyu", "mpym",
	       "mpymu",	and "mpy_s".

	   4
	   wlh3
	       Two 16x16 multipliers,  blocking,  sequential.	The  following
	       instructions  are  additionally enabled:	"mpy", "mpyu", "mpym",
	       "mpymu",	and "mpy_s".

	   5
	   wlh4
	       One 16x16  multiplier,  blocking,  sequential.	The  following
	       instructions  are  additionally enabled:	"mpy", "mpyu", "mpym",
	       "mpymu",	and "mpy_s".

	   6
	   wlh5
	       One  32x4  multiplier,  blocking,  sequential.	The  following
	       instructions  are  additionally enabled:	"mpy", "mpyu", "mpym",
	       "mpymu",	and "mpy_s".

	   7
	   plus_dmpy
	       ARC HS SIMD support.

	   8
	   plus_macd
	       ARC HS SIMD support.

	   9
	   plus_qmacw
	       ARC HS SIMD support.

	   This	option is only available for ARCv2 cores.

       -mfpu=fpu
	   Enables support for specific	floating-point hardware	extensions for
	   ARCv2 cores.	 Supported values for fpu are:

	   fpus
	       Enables support for  single-precision  floating-point  hardware
	       extensions.

	   fpud
	       Enables	support	 for  double-precision floating-point hardware
	       extensions.  The	single-precision floating-point	 extension  is
	       also enabled.  Not available for	ARC EM.

	   fpuda
	       Enables	support	 for  double-precision floating-point hardware
	       extensions using	 double-precision  assist  instructions.   The
	       single-precision	 floating-point	 extension  is	also  enabled.
	       This option is only available for ARC EM.

	   fpuda_div
	       Enables support for  double-precision  floating-point  hardware
	       extensions  using  double-precision  assist  instructions.  The
	       single-precision	 floating-point,   square-root,	  and	divide
	       extensions are also enabled.  This option is only available for
	       ARC EM.

	   fpuda_fma
	       Enables	support	 for  double-precision floating-point hardware
	       extensions using	 double-precision  assist  instructions.   The
	       single-precision	 floating-point	 and  fused  multiply  and add
	       hardware	extensions are also  enabled.	This  option  is  only
	       available for ARC EM.

	   fpuda_all
	       Enables	support	 for  double-precision floating-point hardware
	       extensions using	 double-precision  assist  instructions.   All
	       single-precision	 floating-point	 hardware  extensions are also
	       enabled.	 This option is	only available for ARC EM.

	   fpus_div
	       Enables support for  single-precision  floating-point,  square-
	       root and	divide hardware	extensions.

	   fpud_div
	       Enables	support	 for  double-precision floating-point, square-
	       root and	divide	hardware  extensions.	This  option  includes
	       option fpus_div.	Not available for ARC EM.

	   fpus_fma
	       Enables	support	 for single-precision floating-point and fused
	       multiply	and add	hardware extensions.

	   fpud_fma
	       Enables support for double-precision floating-point  and	 fused
	       multiply	 and  add  hardware  extensions.  This option includes
	       option fpus_fma.	 Not available for ARC EM.

	   fpus_all
	       Enables	support	 for   all   single-precision	floating-point
	       hardware	extensions.

	   fpud_all
	       Enables	support	for all	single-	and double-precision floating-
	       point hardware extensions.  Not available for ARC EM.

       -mirq-ctrl-saved=register-range,	blink, lp_count
	   Specifies   general-purposes	  registers   that    the    processor
	   automatically   saves/restores   on	 interrupt   entry  and	 exit.
	   register-range is specified as two registers	separated by  a	 dash.
	   The register	range always starts with "r0", the upper limit is "fp"
	   register.   blink  and  lp_count are	optional.  This	option is only
	   valid for ARC EM and	ARC HS cores.

       -mrgf-banked-regs=number
	   Specifies the number	of registers  replicated  in  second  register
	   bank	 on  entry  to fast interrupt.	Fast interrupts	are interrupts
	   with	the highest priority level P0.	These interrupts save only  PC
	   and	 STATUS32   registers  to  avoid  memory  transactions	during
	   interrupt entry and exit sequences.	Use this option	when  you  are
	   using  fast	interrupts  in	an ARC V2 family processor.  Permitted
	   values are 4, 8, 16,	and 32.

       -mlpc-width=width
	   Specify the width of	the "lp_count"	register.   Valid  values  for
	   width  are  8,  16,	20,  24, 28 and	32 bits.  The default width is
	   fixed to 32 bits.  If the width is less than	32, the	compiler  does
	   not	attempt	 to  transform	loops in your program to use the zero-
	   delay loop  mechanism  unless  it  is  known	 that  the  "lp_count"
	   register  can  hold	the required loop-counter value.  Depending on
	   the width  specified,  the  compiler	 and  run-time	library	 might
	   continue  to	use the	loop mechanism for various needs.  This	option
	   defines macro "__ARC_LPC_WIDTH__" with the value of width.

       -mrf16
	   This	option instructs the compiler to generate code for a  16-entry
	   register file.  This	option defines the "__ARC_RF16__" preprocessor
	   macro.

       -mbranch-index
	   Enable use of "bi" or "bih" instructions to implement jump tables.

       The  following  options	are  passed through to the assembler, and also
       define preprocessor macro symbols.

       -mdsp-packa
	   Passed down to the assembler	to enable the DSP Pack	A  extensions.
	   Also	 sets  the preprocessor	symbol "__Xdsp_packa".	This option is
	   deprecated.

       -mdvbf
	   Passed down to the assembler	to enable the dual  Viterbi  butterfly
	   extension.	Also  sets  the	 preprocessor  symbol "__Xdvbf".  This
	   option is deprecated.

       -mlock
	   Passed down to  the	assembler  to  enable  the  locked  load/store
	   conditional	 extension.    Also   sets   the  preprocessor	symbol
	   "__Xlock".

       -mmac-d16
	   Passed down to the assembler.  Also sets  the  preprocessor	symbol
	   "__Xxmac_d16".  This	option is deprecated.

       -mmac-24
	   Passed  down	 to  the assembler.  Also sets the preprocessor	symbol
	   "__Xxmac_24".  This option is deprecated.

       -mrtsc
	   Passed down to  the	assembler  to  enable  the  64-bit  time-stamp
	   counter  extension  instruction.  Also sets the preprocessor	symbol
	   "__Xrtsc".  This option is deprecated.

       -mswape
	   Passed down to the assembler	 to  enable  the  swap	byte  ordering
	   extension   instruction.    Also   sets   the  preprocessor	symbol
	   "__Xswape".

       -mtelephony
	   Passed down to the assembler	to  enable  dual-  and	single-operand
	   instructions	 for  telephony.   Also	 sets  the preprocessor	symbol
	   "__Xtelephony".  This option	is deprecated.

       -mxy
	   Passed down to the assembler	to enable  the	XY  memory  extension.
	   Also	sets the preprocessor symbol "__Xxy".

       The following options control how the assembly code is annotated:

       -misize
	   Annotate assembler instructions with	estimated addresses.

       -mannotate-align
	   Explain  what alignment considerations lead to the decision to make
	   an instruction short	or long.

       The following options are passed	through	to the linker:

       -marclinux
	   Passed through to the linker, to  specify  use  of  the  "arclinux"
	   emulation.	This option is enabled by default in tool chains built
	   for	"arc-linux-uclibc"  and	 "arceb-linux-uclibc"	targets	  when
	   profiling is	not requested.

       -marclinux_prof
	   Passed through to the linker, to specify use	of the "arclinux_prof"
	   emulation.	This option is enabled by default in tool chains built
	   for	"arc-linux-uclibc"  and	 "arceb-linux-uclibc"	targets	  when
	   profiling is	requested.

       The following options control the semantics of generated	code:

       -mlong-calls
	   Generate calls as register indirect calls, thus providing access to
	   the full 32-bit address range.

       -mmedium-calls
	   Don't use less than 25-bit addressing range for calls, which	is the
	   offset  available for an unconditional branch-and-link instruction.
	   Conditional execution of function calls is suppressed, to allow use
	   of the 25-bit range,	rather than the	21-bit range with  conditional
	   branch-and-link.   This  is	the  default for tool chains built for
	   "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -G num
	   Put definitions of externally-visible data in a small data  section
	   if that data	is no bigger than num bytes.  The default value	of num
	   is 4	for any	ARC configuration, or 8	when we	have double load/store
	   operations.

       -mno-sdata
	   Do  not  generate  sdata  references.  This is the default for tool
	   chains  built  for  "arc-linux-uclibc"   and	  "arceb-linux-uclibc"
	   targets.

       -mvolatile-cache
	   Use	ordinarily  cached  memory  accesses  for volatile references.
	   This	is the default.

       -mno-volatile-cache
	   Enable cache	bypass for volatile references.

       The following options fine tune code generation:

       -malign-call
	   Do alignment	optimizations for call instructions.

       -mauto-modify-reg
	   Enable the use of pre/post modify with register displacement.

       -mbbit-peephole
	   Enable bbit peephole2.

       -mno-brcc
	   This	 option	 disables  a  target-specific  pass  in	 arc_reorg  to
	   generate  compare-and-branch	 ("brcc")  instructions.   It  has  no
	   effect on generation	of these instructions driven by	 the  combiner
	   pass.

       -mcase-vector-pcrel
	   Use PC-relative switch case tables to enable	case table shortening.
	   This	is the default for -Os.

       -mcompact-casesi
	   Enable  compact "casesi" pattern.  This is the default for -Os, and
	   only	available for ARCv1 cores.  This option	is deprecated.

       -mno-cond-exec
	   Disable  the	 ARCompact-specific  pass  to	generate   conditional
	   execution instructions.

	   Due	to  delay  slot	 scheduling  and  interactions between operand
	   numbers, literal sizes, instruction lengths,	and  the  support  for
	   conditional	execution,  the	 target-independent  pass  to generate
	   conditional execution is often lacking, so the ARC port has kept  a
	   special  pass  around that tries to find more conditional execution
	   generation  opportunities   after   register	  allocation,	branch
	   shortening,	and  delay  slot scheduling have been done.  This pass
	   generally, but not always, improves performance and code  size,  at
	   the cost of extra compilation time, which is	why there is an	option
	   to  switch  it  off.	  If you have a	problem	with call instructions
	   exceeding  their  allowable	 offset	  range	  because   they   are
	   conditionalized, you	should consider	using -mmedium-calls instead.

       -mearly-cbranchsi
	   Enable pre-reload use of the	"cbranchsi" pattern.

       -mexpand-adddi
	   Expand  "adddi3"  and "subdi3" at RTL generation time into "add.f",
	   "adc" etc.  This option is deprecated.

       -mindexed-loads
	   Enable the use of indexed loads.  This can be  problematic  because
	   some	optimizers then	assume that indexed stores exist, which	is not
	   the case.

       -mlra
	   Enable  Local  Register Allocation.	This is	still experimental for
	   ARC,	 so  by	 default  the  compiler	 uses  standard	 reload	 (i.e.
	   -mno-lra).

       -mlra-priority-none
	   Don't indicate any priority for target registers.

       -mlra-priority-compact
	   Indicate target register priority for r0..r3	/ r12..r15.

       -mlra-priority-noncompact
	   Reduce target register priority for r0..r3 /	r12..r15.

       -mmillicode
	   When	 optimizing for	size (using -Os), prologues and	epilogues that
	   have	to save	or restore a  large  number  of	 registers  are	 often
	   shortened  by  using	 call to a special function in libgcc; this is
	   referred  to	 as  a	millicode  call.   As  these  calls  can  pose
	   performance	issues,	 and/or	cause linking issues when linking in a
	   nonstandard way,  this  option  is  provided	 to  turn  on  or  off
	   millicode call generation.

       -mcode-density-frame
	   This	 option	 enable	 the  compiler	to  emit  "enter"  and "leave"
	   instructions.  These	instructions are  only	valid  for  CPUs  with
	   code-density	feature.

       -mmixed-code
	   Tweak  register  allocation	to help	16-bit instruction generation.
	   This	generally has the effect of decreasing the average instruction
	   size	while increasing the instruction count.

       -mq-class
	   Ths option is deprecated.  Enable q instruction alternatives.  This
	   is the default for -Os.

       -mRcq
	   Enable Rcq constraint handling.  Most short code generation depends
	   on this.  This is the default.

       -mRcw
	   Enable Rcw constraint handling.  Most ccfsm condexec	mostly depends
	   on this.  This is the default.

       -msize-level=level
	   Fine-tune size optimization with regards to instruction lengths and
	   alignment.  The recognized values for level are:

	   0   No size optimization.  This level  is  deprecated  and  treated
	       like 1.

	   1   Short instructions are used opportunistically.

	   2   In  addition, alignment of loops	and of code after barriers are
	       dropped.

	   3   In addition, optional data alignment is dropped,	and the	option
	       Os is enabled.

	   This	defaults to 3 when -Os is in effect.  Otherwise, the  behavior
	   when	this is	not set	is equivalent to level 1.

       -mtune=cpu
	   Set	instruction  scheduling	 parameters  for  cpu,	overriding any
	   implied by -mcpu=.

	   Supported values for	cpu are

	   ARC600
	       Tune for	ARC600 CPU.

	   ARC601
	       Tune for	ARC601 CPU.

	   ARC700
	       Tune for	ARC700 CPU with	standard multiplier block.

	   ARC700-xmac
	       Tune for	ARC700 CPU with	XMAC block.

	   ARC725D
	       Tune for	ARC725D	CPU.

	   ARC750D
	       Tune for	ARC750D	CPU.

       -mmultcost=num
	   Cost	to assume for a	multiply instruction, with 4 being equal to  a
	   normal instruction.

       -munalign-prob-threshold=probability
	   Set probability threshold for unaligning branches.  When tuning for
	   ARC700 and optimizing for speed, branches without filled delay slot
	   are	 preferably  emitted  unaligned	 and  long,  unless  profiling
	   indicates that the probability for the branch to be taken is	 below
	   probability.	 The default is	(REG_BR_PROB_BASE/2), i.e. 5000.

       The  following  options	are maintained for backward compatibility, but
       are now deprecated and will be removed in a future release:

       -margonaut
	   Obsolete FPX.

       -mbig-endian
       -EB Compile code	for big-endian targets.	 Use of	these options  is  now
	   deprecated.	 Big-endian  code  is  supported by configuring	GCC to
	   build "arceb-elf32" and "arceb-linux-uclibc"	targets, for which big
	   endian is the default.

       -mlittle-endian
       -EL Compile code	for little-endian targets.  Use	of  these  options  is
	   now deprecated.  Little-endian code is supported by configuring GCC
	   to  build  "arc-elf32"  and	"arc-linux-uclibc"  targets, for which
	   little endian is the	default.

       -mbarrel_shifter
	   Replaced by -mbarrel-shifter.

       -mdpfp_compact
	   Replaced by -mdpfp-compact.

       -mdpfp_fast
	   Replaced by -mdpfp-fast.

       -mdsp_packa
	   Replaced by -mdsp-packa.

       -mEA
	   Replaced by -mea.

       -mmac_24
	   Replaced by -mmac-24.

       -mmac_d16
	   Replaced by -mmac-d16.

       -mspfp_compact
	   Replaced by -mspfp-compact.

       -mspfp_fast
	   Replaced by -mspfp-fast.

       -mtune=cpu
	   Values arc600, arc601, arc700 and arc700-xmac for cpu are  replaced
	   by ARC600, ARC601, ARC700 and ARC700-xmac respectively.

       -multcost=num
	   Replaced by -mmultcost.

       ARM Options

       These -m	options	are defined for	the ARM	port:

       -mabi=name
	   Generate code for the specified ABI.	 Permissible values are: apcs-
	   gnu,	atpcs, aapcs, aapcs-linux and iwmmxt.

       -mapcs-frame
	   Generate  a	stack  frame  that is compliant	with the ARM Procedure
	   Call	Standard for all functions,  even  if  this  is	 not  strictly
	   necessary   for   correct   execution   of  the  code.   Specifying
	   -fomit-frame-pointer	with this option causes	the stack  frames  not
	   to	be   generated	 for   leaf   functions.    The	  default   is
	   -mno-apcs-frame.  This option is deprecated.

       -mapcs
	   This	is a synonym for -mapcs-frame and is deprecated.

       -mthumb-interwork
	   Generate code that supports	calling	 between  the  ARM  and	 Thumb
	   instruction	sets.	Without	 this option, on pre-v5	architectures,
	   the two  instruction	 sets  cannot  be  reliably  used  inside  one
	   program.   The  default  is	-mno-thumb-interwork,  since  slightly
	   larger code is generated when -mthumb-interwork is  specified.   In
	   AAPCS configurations	this option is meaningless.

       -mno-sched-prolog
	   Prevent the reordering of instructions in the function prologue, or
	   the	merging	 of  those  instruction	 with  the instructions	in the
	   function's body.  This  means  that	all  functions	start  with  a
	   recognizable	set of instructions (or	in fact	one of a choice	from a
	   small  set  of  different function prologues), and this information
	   can be used to locate the start of functions	inside	an  executable
	   piece of code.  The default is -msched-prolog.

       -mfloat-abi=name
	   Specifies which floating-point ABI to use.  Permissible values are:
	   soft, softfp	and hard.

	   Specifying  soft  causes  GCC to generate output containing library
	   calls for floating-point operations.	 softfp	allows the  generation
	   of  code using hardware floating-point instructions,	but still uses
	   the soft-float calling  conventions.	  hard	allows	generation  of
	   floating-point   instructions   and	 uses	FPU-specific   calling
	   conventions.

	   The default depends on the  specific	 target	 configuration.	  Note
	   that	 the  hard-float  and soft-float ABIs are not link-compatible;
	   you must compile your entire	program	with the same  ABI,  and  link
	   with	a compatible set of libraries.

       -mgeneral-regs-only
	   Generate  code which	uses only the general-purpose registers.  This
	   will	prevent	the compiler from using	 floating-point	 and  Advanced
	   SIMD	 registers  but	 will  not  impose  any	 restrictions  on  the
	   assembler.

       -mlittle-endian
	   Generate code for a processor running in little-endian mode.	  This
	   is the default for all standard configurations.

       -mbig-endian
	   Generate  code  for	a  processor  running  in big-endian mode; the
	   default is to compile code for a little-endian processor.

       -mbe8
       -mbe32
	   When	linking	 a  big-endian	image  select  between	BE8  and  BE32
	   formats.   The option has no	effect for little-endian images	and is
	   ignored.   The  default  is	dependent  on  the   selected	target
	   architecture.   For	ARMv6  and  later architectures	the default is
	   BE8,	for older architectures	the default is BE32.  BE32 format  has
	   been	deprecated by ARM.

       -march=name[+extension...]
	   This	 specifies  the	name of	the target ARM architecture.  GCC uses
	   this	name to	determine what kind of instructions it can  emit  when
	   generating  assembly	 code.	This option can	be used	in conjunction
	   with	or instead of the -mcpu= option.

	   Permissible names are:  armv4t,  armv5t,  armv5te,  armv6,  armv6j,
	   armv6k, armv6kz, armv6t2, armv6z, armv6zk, armv7, armv7-a, armv7ve,
	   armv8-a,  armv8.1-a,	 armv8.2-a,  armv8.3-a,	 armv8.4-a, armv8.5-a,
	   armv8.6-a, armv7-r, armv8-r,	armv6-m, armv6s-m, armv7-m,  armv7e-m,
	   armv8-m.base, armv8-m.main, armv8.1-m.main, iwmmxt and iwmmxt2.

	   Additionally,  the  following architectures,	which lack support for
	   the	Thumb  execution  state,  are  recognized   but	  support   is
	   deprecated: armv4.

	   Many	 of  the architectures support extensions.  These can be added
	   by  appending  +extension  to  the  architecture  name.   Extension
	   options  are	 processed  in	order and capabilities accumulate.  An
	   extension will also enable any necessary base extensions upon which
	   it depends.	For example, the +crypto extension will	always	enable
	   the +simd extension.	 The exception to the additive construction is
	   for	extensions  that  are  prefixed	 with +no...: these extensions
	   disable the specified option	and  any  other	 extensions  that  may
	   depend on the presence of that extension.

	   For	 example,   -march=armv7-a+simd+nofp+vfpv4  is	equivalent  to
	   writing -march=armv7-a+vfpv4	since the  +simd  option  is  entirely
	   disabled by the +nofp option	that follows it.

	   Most	extension names	are generically	named, but have	an effect that
	   is  dependent  upon	the  architecture to which it is applied.  For
	   example, the	+simd option  can  be  applied	to  both  armv7-a  and
	   armv8-a   architectures,  but  will	enable	the  original  ARMv7-A
	   Advanced SIMD (Neon)	extensions for armv7-a and the ARMv8-A variant
	   for armv8-a.

	   The	table  below  lists  the   supported   extensions   for	  each
	   architecture.   Architectures  not  mentioned  do  not  support any
	   extensions.

	   armv5te
	   armv6
	   armv6j
	   armv6k
	   armv6kz
	   armv6t2
	   armv6z
	   armv6zk
	       +fp The	VFPv2  floating-point  instructions.   The   extension
		   +vfpv2 can be used as an alias for this extension.

	       +nofp
		   Disable the floating-point instructions.

	   armv7
	       The   common   subset  of  the  ARMv7-A,	 ARMv7-R  and  ARMv7-M
	       architectures.

	       +fp The VFPv3  floating-point  instructions,  with  16  double-
		   precision  registers.  The extension	+vfpv3-d16 can be used
		   as an alias for this	extension.  Note  that	floating-point
		   is  not  supported by the base ARMv7-M architecture,	but is
		   compatible with both	the ARMv7-A and	ARMv7-R	architectures.

	       +nofp
		   Disable the floating-point instructions.

	   armv7-a
	       +mp The multiprocessing extension.

	       +sec
		   The security	extension.

	       +fp The VFPv3  floating-point  instructions,  with  16  double-
		   precision  registers.  The extension	+vfpv3-d16 can be used
		   as an alias for this	extension.

	       +simd
		   The Advanced	SIMD (Neon) v1 and  the	 VFPv3	floating-point
		   instructions.   The extensions +neon	and +neon-vfpv3	can be
		   used	as aliases for this extension.

	       +vfpv3
		   The VFPv3  floating-point  instructions,  with  32  double-
		   precision registers.

	       +vfpv3-d16-fp16
		   The	VFPv3  floating-point  instructions,  with  16 double-
		   precision registers and the	half-precision	floating-point
		   conversion operations.

	       +vfpv3-fp16
		   The	VFPv3  floating-point  instructions,  with  32 double-
		   precision registers and the	half-precision	floating-point
		   conversion operations.

	       +vfpv4-d16
		   The	VFPv4  floating-point  instructions,  with  16 double-
		   precision registers.

	       +vfpv4
		   The VFPv4  floating-point  instructions,  with  32  double-
		   precision registers.

	       +neon-fp16
		   The	Advanced  SIMD	(Neon) v1 and the VFPv3	floating-point
		   instructions,  with	 the   half-precision	floating-point
		   conversion operations.

	       +neon-vfpv4
		   The	Advanced  SIMD	(Neon) v2 and the VFPv4	floating-point
		   instructions.

	       +nosimd
		   Disable the Advanced	SIMD instructions  (does  not  disable
		   floating point).

	       +nofp
		   Disable the floating-point and Advanced SIMD	instructions.

	   armv7ve
	       The  extended  version of the ARMv7-A architecture with support
	       for virtualization.

	       +fp The VFPv4  floating-point  instructions,  with  16  double-
		   precision  registers.  The extension	+vfpv4-d16 can be used
		   as an alias for this	extension.

	       +simd
		   The Advanced	SIMD (Neon) v2 and  the	 VFPv4	floating-point
		   instructions.   The extension +neon-vfpv4 can be used as an
		   alias for this extension.

	       +vfpv3-d16
		   The VFPv3  floating-point  instructions,  with  16  double-
		   precision registers.

	       +vfpv3
		   The	VFPv3  floating-point  instructions,  with  32 double-
		   precision registers.

	       +vfpv3-d16-fp16
		   The VFPv3  floating-point  instructions,  with  16  double-
		   precision  registers	 and the half-precision	floating-point
		   conversion operations.

	       +vfpv3-fp16
		   The VFPv3  floating-point  instructions,  with  32  double-
		   precision  registers	 and the half-precision	floating-point
		   conversion operations.

	       +vfpv4-d16
		   The VFPv4  floating-point  instructions,  with  16  double-
		   precision registers.

	       +vfpv4
		   The	VFPv4  floating-point  instructions,  with  32 double-
		   precision registers.

	       +neon
		   The Advanced	SIMD (Neon) v1 and  the	 VFPv3	floating-point
		   instructions.   The extension +neon-vfpv3 can be used as an
		   alias for this extension.

	       +neon-fp16
		   The Advanced	SIMD (Neon) v1 and  the	 VFPv3	floating-point
		   instructions,   with	  the	half-precision	floating-point
		   conversion operations.

	       +nosimd
		   Disable the Advanced	SIMD instructions  (does  not  disable
		   floating point).

	       +nofp
		   Disable the floating-point and Advanced SIMD	instructions.

	   armv8-a
	       +crc
		   The Cyclic Redundancy Check (CRC) instructions.

	       +simd
		   The ARMv8-A Advanced	SIMD and floating-point	instructions.

	       +crypto
		   The cryptographic instructions.

	       +nocrypto
		   Disable the cryptographic instructions.

	       +nofp
		   Disable the floating-point, Advanced	SIMD and cryptographic
		   instructions.

	       +sb Speculation Barrier Instruction.

	       +predres
		   Execution and Data Prediction Restriction Instructions.

	   armv8.1-a
	       +simd
		   The	  ARMv8.1-A    Advanced	   SIMD	  and	floating-point
		   instructions.

	       +crypto
		   The cryptographic  instructions.   This  also  enables  the
		   Advanced SIMD and floating-point instructions.

	       +nocrypto
		   Disable the cryptographic instructions.

	       +nofp
		   Disable the floating-point, Advanced	SIMD and cryptographic
		   instructions.

	       +sb Speculation Barrier Instruction.

	       +predres
		   Execution and Data Prediction Restriction Instructions.

	   armv8.2-a
	   armv8.3-a
	       +fp16
		   The	  half-precision    floating-point   data   processing
		   instructions.  This also  enables  the  Advanced  SIMD  and
		   floating-point instructions.

	       +fp16fml
		   The	half-precision	floating-point	fmla  extension.  This
		   also	enables	the  half-precision  floating-point  extension
		   and Advanced	SIMD and floating-point	instructions.

	       +simd
		   The	  ARMv8.1-A    Advanced	   SIMD	  and	floating-point
		   instructions.

	       +crypto
		   The cryptographic  instructions.   This  also  enables  the
		   Advanced SIMD and floating-point instructions.

	       +dotprod
		   Enable  the	Dot  Product  extension.   This	 also  enables
		   Advanced SIMD instructions.

	       +nocrypto
		   Disable the cryptographic extension.

	       +nofp
		   Disable the floating-point, Advanced	SIMD and cryptographic
		   instructions.

	       +sb Speculation Barrier Instruction.

	       +predres
		   Execution and Data Prediction Restriction Instructions.

	       +i8mm
		   8-bit Integer  Matrix  Multiply  instructions.   This  also
		   enables Advanced SIMD and floating-point instructions.

	       +bf16
		   Brain  half-precision  floating-point  instructions.	  This
		   also	enables	Advanced SIMD and floating-point instructions.

	   armv8.4-a
	       +fp16
		   The	 half-precision	  floating-point    data    processing
		   instructions.   This	 also  enables	the  Advanced SIMD and
		   floating-point instructions as  well	 as  the  Dot  Product
		   extension   and   the  half-precision  floating-point  fmla
		   extension.

	       +simd
		   The ARMv8.3-A Advanced SIMD and floating-point instructions
		   as well as the Dot Product extension.

	       +crypto
		   The cryptographic  instructions.   This  also  enables  the
		   Advanced  SIMD  and	floating-point instructions as well as
		   the Dot Product extension.

	       +nocrypto
		   Disable the cryptographic extension.

	       +nofp
		   Disable the floating-point, Advanced	SIMD and cryptographic
		   instructions.

	       +sb Speculation Barrier Instruction.

	       +predres
		   Execution and Data Prediction Restriction Instructions.

	       +i8mm
		   8-bit Integer  Matrix  Multiply  instructions.   This  also
		   enables Advanced SIMD and floating-point instructions.

	       +bf16
		   Brain  half-precision  floating-point  instructions.	  This
		   also	enables	Advanced SIMD and floating-point instructions.

	   armv8.5-a
	       +fp16
		   The	 half-precision	  floating-point    data    processing
		   instructions.   This	 also  enables	the  Advanced SIMD and
		   floating-point instructions as  well	 as  the  Dot  Product
		   extension   and   the  half-precision  floating-point  fmla
		   extension.

	       +simd
		   The ARMv8.3-A Advanced SIMD and floating-point instructions
		   as well as the Dot Product extension.

	       +crypto
		   The cryptographic  instructions.   This  also  enables  the
		   Advanced  SIMD  and	floating-point instructions as well as
		   the Dot Product extension.

	       +nocrypto
		   Disable the cryptographic extension.

	       +nofp
		   Disable the floating-point, Advanced	SIMD and cryptographic
		   instructions.

	       +i8mm
		   8-bit Integer  Matrix  Multiply  instructions.   This  also
		   enables Advanced SIMD and floating-point instructions.

	       +bf16
		   Brain  half-precision  floating-point  instructions.	  This
		   also	enables	Advanced SIMD and floating-point instructions.

	   armv8.6-a
	       +fp16
		   The	 half-precision	  floating-point    data    processing
		   instructions.   This	 also  enables	the  Advanced SIMD and
		   floating-point instructions as  well	 as  the  Dot  Product
		   extension   and   the  half-precision  floating-point  fmla
		   extension.

	       +simd
		   The ARMv8.3-A Advanced SIMD and floating-point instructions
		   as well as the Dot Product extension.

	       +crypto
		   The cryptographic  instructions.   This  also  enables  the
		   Advanced  SIMD  and	floating-point instructions as well as
		   the Dot Product extension.

	       +nocrypto
		   Disable the cryptographic extension.

	       +nofp
		   Disable the floating-point, Advanced	SIMD and cryptographic
		   instructions.

	       +i8mm
		   8-bit Integer  Matrix  Multiply  instructions.   This  also
		   enables Advanced SIMD and floating-point instructions.

	       +bf16
		   Brain  half-precision  floating-point  instructions.	  This
		   also	enables	Advanced SIMD and floating-point instructions.

	   armv7-r
	       +fp.sp
		   The	single-precision  VFPv3	 floating-point	 instructions.
		   The	extension  +vfpv3xd  can  be used as an	alias for this
		   extension.

	       +fp The	VFPv3  floating-point  instructions  with  16  double-
		   precision  registers.  The extension	+vfpv3-d16 can be used
		   as an alias for this	extension.

	       +vfpv3xd-d16-fp16
		   The single-precision	VFPv3 floating-point instructions with
		   16  double-precision	 registers  and	  the	half-precision
		   floating-point conversion operations.

	       +vfpv3-d16-fp16
		   The	VFPv3  floating-point  instructions  with  16  double-
		   precision registers and the	half-precision	floating-point
		   conversion operations.

	       +nofp
		   Disable the floating-point extension.

	       +idiv
		   The ARM-state integer division instructions.

	       +noidiv
		   Disable the ARM-state integer division extension.

	   armv7e-m
	       +fp The single-precision	VFPv4 floating-point instructions.

	       +fpv5
		   The single-precision	FPv5 floating-point instructions.

	       +fp.dp
		   The	 single-   and	double-precision  FPv5	floating-point
		   instructions.

	       +nofp
		   Disable the floating-point extensions.

	   armv8.1-m.main
	       +dsp
		   The DSP instructions.

	       +mve
		   The M-Profile Vector	Extension (MVE)	integer	instructions.

	       +mve.fp
		   The M-Profile Vector	Extension  (MVE)  integer  and	single
		   precision floating-point instructions.

	       +fp The single-precision	floating-point instructions.

	       +fp.dp
		   The	  single-    and    double-precision	floating-point
		   instructions.

	       +nofp
		   Disable the floating-point extension.

	       +cdecp0,	+cdecp1, ... , +cdecp7
		   Enable the Custom  Datapath	Extension  (CDE)  on  selected
		   coprocessors	 according to the numbers given	in the options
		   in the range	0 to 7.

	   armv8-m.main
	       +dsp
		   The DSP instructions.

	       +nodsp
		   Disable the DSP extension.

	       +fp The single-precision	floating-point instructions.

	       +fp.dp
		   The	  single-    and    double-precision	floating-point
		   instructions.

	       +nofp
		   Disable the floating-point extension.

	       +cdecp0,	+cdecp1, ... , +cdecp7
		   Enable  the	Custom	Datapath  Extension  (CDE) on selected
		   coprocessors	according to the numbers given in the  options
		   in the range	0 to 7.

	   armv8-r
	       +crc
		   The Cyclic Redundancy Check (CRC) instructions.

	       +fp.sp
		   The single-precision	FPv5 floating-point instructions.

	       +simd
		   The ARMv8-A Advanced	SIMD and floating-point	instructions.

	       +crypto
		   The cryptographic instructions.

	       +nocrypto
		   Disable the cryptographic instructions.

	       +nofp
		   Disable the floating-point, Advanced	SIMD and cryptographic
		   instructions.

	   -march=native  causes  the compiler to auto-detect the architecture
	   of the build	computer.  At present, this feature is only  supported
	   on  GNU/Linux,  and	not  all architectures are recognized.	If the
	   auto-detect is unsuccessful the option has no effect.

       -mtune=name
	   This	option specifies the name of  the  target  ARM	processor  for
	   which  GCC  should  tune the	performance of the code.  For some ARM
	   implementations better performance can be obtained  by  using  this
	   option.   Permissible  names	 are:  arm7tdmi,  arm7tdmi-s, arm710t,
	   arm720t,   arm740t,	 strongarm,    strongarm110,	strongarm1100,
	   0strongarm1110,   arm8,   arm810,  arm9,  arm9e,  arm920,  arm920t,
	   arm922t,  arm946e-s,	 arm966e-s,  arm968e-s,	 arm926ej-s,  arm940t,
	   arm9tdmi,   arm10tdmi,  arm1020t,  arm1026ej-s,  arm10e,  arm1020e,
	   arm1022e,	arm1136j-s,    arm1136jf-s,    mpcore,	  mpcorenovfp,
	   arm1156t2-s,	     arm1156t2f-s,	arm1176jz-s,	 arm1176jzf-s,
	   generic-armv7-a,  cortex-a5,	  cortex-a7,   cortex-a8,   cortex-a9,
	   cortex-a12,	 cortex-a15,   cortex-a17,   cortex-a32,   cortex-a35,
	   cortex-a53,	 cortex-a55,   cortex-a57,   cortex-a72,   cortex-a73,
	   cortex-a75,	 cortex-a76,   cortex-a76ae,  cortex-a77,  cortex-a78,
	   cortex-a78ae, cortex-a78c, ares, cortex-r4, cortex-r4f,  cortex-r5,
	   cortex-r7,	cortex-r8,   cortex-r52,   cortex-m0,	cortex-m0plus,
	   cortex-m1, cortex-m3, cortex-m4, cortex-m7, cortex-m23, cortex-m33,
	   cortex-m35p,	  cortex-m55,	cortex-x1,   cortex-m1.small-multiply,
	   cortex-m0.small-multiply,  cortex-m0plus.small-multiply, exynos-m1,
	   marvell-pj4,	neoverse-n1, neoverse-n2, neoverse-v1, xscale, iwmmxt,
	   iwmmxt2, ep9312, fa526, fa626, fa606te, fa626te,  fmp626,  fa726te,
	   xgene1.

	   Additionally,  this	option	can  specify  that GCC should tune the
	   performance of the code for a big.LITTLE system.  Permissible names
	   are:		 cortex-a15.cortex-a7,		 cortex-a17.cortex-a7,
	   cortex-a57.cortex-a53,			cortex-a72.cortex-a53,
	   cortex-a72.cortex-a35,			cortex-a73.cortex-a53,
	   cortex-a75.cortex-a55, cortex-a76.cortex-a55.

	   -mtune=generic-arch	specifies that GCC should tune the performance
	   for a blend of processors within architecture arch.	The aim	is  to
	   generate code that run well on the current most popular processors,
	   balancing  between  optimizations  that  benefit  some  CPUs	in the
	   range, and  avoiding	 performance  pitfalls	of  other  CPUs.   The
	   effects  of	this  option  may change in future GCC versions	as CPU
	   models come and go.

	   -mtune permits  the	same  extension	 options  as  -mcpu,  but  the
	   extension options do	not affect the tuning of the generated code.

	   -mtune=native  causes  the  compiler	 to auto-detect	the CPU	of the
	   build computer.  At present,	this  feature  is  only	 supported  on
	   GNU/Linux,  and not all architectures are recognized.  If the auto-
	   detect is unsuccessful the option has no effect.

       -mcpu=name[+extension...]
	   This	specifies the name of the target ARM processor.	 GCC uses this
	   name	to derive the name of  the  target  ARM	 architecture  (as  if
	   specified  by  -march) and the ARM processor	type for which to tune
	   for performance (as if specified by -mtune).	 Where this option  is
	   used	 in  conjunction  with	-march	or  -mtune, those options take
	   precedence over the appropriate part	of this	option.

	   Many	 of  the  supported  CPUs  implement  optional	 architectural
	   extensions.	 Where	this  is  so  the architectural	extensions are
	   normally enabled by default.	  If  implementations  that  lack  the
	   extension  exist,  then the extension syntax	can be used to disable
	   those extensions that have been omitted.   For  floating-point  and
	   Advanced  SIMD  (Neon)  instructions,  the  settings	of the options
	   -mfloat-abi and -mfpu must also be considered:  floating-point  and
	   Advanced  SIMD instructions will only be used if -mfloat-abi	is not
	   set to soft;	and any	setting	of -mfpu other than auto will override
	   the available floating-point	and SIMD extension instructions.

	   For example,	cortex-a9 can be found in three	major  configurations:
	   integer  only,  with	 just  a floating-point	unit or	with floating-
	   point and  Advanced	SIMD.	The  default  is  to  enable  all  the
	   instructions,  but  the extensions +nosimd and +nofp	can be used to
	   disable  just  the  SIMD  or	 both  the  SIMD  and	floating-point
	   instructions	respectively.

	   Permissible names for this option are the same as those for -mtune.

	   The following extension options are common to the listed CPUs:

	   +nodsp
	       Disable the DSP instructions on cortex-m33, cortex-m35p.

	   +nofp
	       Disables	 the  floating-point instructions on arm9e, arm946e-s,
	       arm966e-s, arm968e-s, arm10e, arm1020e,	arm1022e,  arm926ej-s,
	       arm1026ej-s,   cortex-r5,   cortex-r7,	cortex-r8,  cortex-m4,
	       cortex-m7, cortex-m33 and cortex-m35p.  Disables	the  floating-
	       point  and  SIMD	 instructions  on  generic-armv7-a, cortex-a5,
	       cortex-a7,  cortex-a8,	cortex-a9,   cortex-a12,   cortex-a15,
	       cortex-a17,     cortex-a15.cortex-a7,	 cortex-a17.cortex-a7,
	       cortex-a32, cortex-a35, cortex-a53 and cortex-a55.

	   +nofp.dp
	       Disables	the double-precision component of  the	floating-point
	       instructions on cortex-r5, cortex-r7, cortex-r8,	cortex-r52 and
	       cortex-m7.

	   +nosimd
	       Disables	 the  SIMD  (but  not  floating-point) instructions on
	       generic-armv7-a,	cortex-a5, cortex-a7 and cortex-a9.

	   +crypto
	       Enables	 the   cryptographic   instructions   on   cortex-a32,
	       cortex-a35,  cortex-a53,	 cortex-a55,  cortex-a57,  cortex-a72,
	       cortex-a73,	  cortex-a75,	     exynos-m1,	       xgene1,
	       cortex-a57.cortex-a53,			cortex-a72.cortex-a53,
	       cortex-a73.cortex-a35,	     cortex-a73.cortex-a53	   and
	       cortex-a75.cortex-a55.

	   Additionally	 the  generic-armv7-a  pseudo target defaults to VFPv3
	   with	16 double-precision  registers.	  It  supports	the  following
	   extension  options:	mp,  sec,  vfpv3-d16,  vfpv3,  vfpv3-d16-fp16,
	   vfpv3-fp16,	vfpv4-d16,   vfpv4,   neon,   neon-vfpv3,   neon-fp16,
	   neon-vfpv4.	 The  meanings	are  the same as for the extensions to
	   -march=armv7-a.

	   -mcpu=generic-arch  is  also	 permissible,  and  is	equivalent  to
	   -march=arch -mtune=generic-arch.  See -mtune	for more information.

	   -mcpu=native	 causes	 the  compiler	to  auto-detect	the CPU	of the
	   build computer.  At present,	this  feature  is  only	 supported  on
	   GNU/Linux,  and not all architectures are recognized.  If the auto-
	   detect is unsuccessful the option has no effect.

       -mfpu=name
	   This	specifies what floating-point hardware (or hardware emulation)
	   is available	on the target.	Permissible names  are:	 auto,	vfpv2,
	   vfpv3,     vfpv3-fp16,    vfpv3-d16,	   vfpv3-d16-fp16,    vfpv3xd,
	   vfpv3xd-fp16, neon-vfpv3, neon-fp16,	vfpv4, vfpv4-d16, fpv4-sp-d16,
	   neon-vfpv4,	fpv5-d16,  fpv5-sp-d16,	 fp-armv8,  neon-fp-armv8  and
	   crypto-neon-fp-armv8.   Note	 that  neon is an alias	for neon-vfpv3
	   and vfp is an alias for vfpv2.

	   The setting auto is the default and	is  special.   It  causes  the
	   compiler   to   select   the	  floating-point   and	Advanced  SIMD
	   instructions	based on the settings of -mcpu and -march.

	   If the selected floating-point hardware includes the	NEON extension
	   (e.g. -mfpu=neon), note  that  floating-point  operations  are  not
	   generated	 by	GCC's	  auto-vectorization	pass	unless
	   -funsafe-math-optimizations is also	specified.   This  is  because
	   NEON	 hardware  does	 not fully implement the IEEE 754 standard for
	   floating-point  arithmetic  (in  particular	denormal  values   are
	   treated  as	zero),	so  the	use of NEON instructions may lead to a
	   loss	of precision.

	   You can also	set the	fpu  name  at  function	 level	by  using  the
	   "target("fpu=")" function attributes	or pragmas.

       -mfp16-format=name
	   Specify  the	 format	 of the	"__fp16" half-precision	floating-point
	   type.  Permissible names  are  none,	 ieee,	and  alternative;  the
	   default is none, in which case the "__fp16" type is not defined.

       -mstructure-size-boundary=n
	   The sizes of	all structures and unions are rounded up to a multiple
	   of  the  number of bits set by this option.	Permissible values are
	   8, 32 and 64.  The default value varies for	different  toolchains.
	   For the COFF	targeted toolchain the default value is	8.  A value of
	   64 is only allowed if the underlying	ABI supports it.

	   Specifying a	larger number can produce faster, more efficient code,
	   but	can  also  increase the	size of	the program.  Different	values
	   are potentially incompatible.  Code compiled	with one value	cannot
	   necessarily	expect	to  work  with code or libraries compiled with
	   another value, if they exchange  information	 using	structures  or
	   unions.

	   This	option is deprecated.

       -mabort-on-noreturn
	   Generate  a call to the function "abort" at the end of a "noreturn"
	   function.  It is executed if	the function tries to return.

       -mlong-calls
       -mno-long-calls
	   Tells the compiler to perform function calls	by first  loading  the
	   address  of	the  function  into  a	register and then performing a
	   subroutine call on this register.  This switch  is  needed  if  the
	   target function lies	outside	of the 64-megabyte addressing range of
	   the offset-based version of subroutine call instruction.

	   Even	 if  this switch is enabled, not all function calls are	turned
	   into	long calls.  The heuristic is that static functions, functions
	   that	have the "short_call" attribute, functions that	are inside the
	   scope of a "#pragma no_long_calls" directive, and  functions	 whose
	   definitions	 have	already	  been	compiled  within  the  current
	   compilation unit are	not turned into	long calls.  The exceptions to
	   this	rule are that weak function definitions,  functions  with  the
	   "long_call"	attribute  or  the  "section" attribute, and functions
	   that	are within the scope of	a "#pragma long_calls"	directive  are
	   always turned into long calls.

	   This	feature	is not enabled by default.  Specifying -mno-long-calls
	   restores  the  default behavior, as does placing the	function calls
	   within the scope of a  "#pragma  long_calls_off"  directive.	  Note
	   these switches have no effect on how	the compiler generates code to
	   handle function calls via function pointers.

       -msingle-pic-base
	   Treat  the  register	 used  for PIC addressing as read-only,	rather
	   than	loading	it in the prologue for	each  function.	  The  runtime
	   system  is  responsible  for	 initializing  this  register  with an
	   appropriate value before execution begins.

       -mpic-register=reg
	   Specify the register	to be used for PIC addressing.	 For  standard
	   PIC	base  case, the	default	is any suitable	register determined by
	   compiler.  For single PIC base case,	the default is R9 if target is
	   EABI	based or stack-checking	is enabled, otherwise the  default  is
	   R10.

       -mpic-data-is-text-relative
	   Assume  that	the displacement between the text and data segments is
	   fixed  at  static  link  time.   This  permits  using   PC-relative
	   addressing  operations  to  access  data  known  to	be in the data
	   segment.  For non-VxWorks RTP targets, this option  is  enabled  by
	   default.    When   disabled	 on   such  targets,  it  will	enable
	   -msingle-pic-base by	default.

       -mpoke-function-name
	   Write the name of each function into	 the  text  section,  directly
	   preceding  the function prologue.  The generated code is similar to
	   this:

			t0
			    .ascii "arm_poke_function_name", 0
			    .align
			t1
			    .word 0xff000000 + (t1 - t0)
			arm_poke_function_name
			    mov	    ip,	sp
			    stmfd   sp!, {fp, ip, lr, pc}
			    sub	    fp,	ip, #4

	   When	performing a stack backtrace, code can inspect	the  value  of
	   "pc"	 stored	 at  "fp  +  0".   If the trace	function then looks at
	   location "pc	- 12" and the top 8 bits are set, then	we  know  that
	   there  is  a	 function  name	 embedded  immediately	preceding this
	   location and	has length "((pc[-3]) &	0xff000000)".

       -mthumb
       -marm
	   Select between generating code  that	 executes  in  ARM  and	 Thumb
	   states.   The  default  for most configurations is to generate code
	   that	executes in ARM	state, but  the	 default  can  be  changed  by
	   configuring GCC with	the --with-mode=state configure	option.

	   You	can  also override the ARM and Thumb mode for each function by
	   using the "target("thumb")" and "target("arm")" function attributes
	   or pragmas.

       -mflip-thumb
	   Switch ARM/Thumb modes on alternating functions.   This  option  is
	   provided for	regression testing of mixed Thumb/ARM code generation,
	   and is not intended for ordinary use	in compiling code.

       -mtpcs-frame
	   Generate  a	stack frame that is compliant with the Thumb Procedure
	   Call	Standard for all non-leaf functions.  (A leaf function is  one
	   that	  does	 not  call  any	 other	functions.)   The  default  is
	   -mno-tpcs-frame.

       -mtpcs-leaf-frame
	   Generate a stack frame that is compliant with the  Thumb  Procedure
	   Call	Standard for all leaf functions.  (A leaf function is one that
	   does	  not	call   any   other   functions.)    The	  default   is
	   -mno-apcs-leaf-frame.

       -mcallee-super-interworking
	   Gives all externally	visible	functions in the file  being  compiled
	   an  ARM  instruction	set header which switches to Thumb mode	before
	   executing the rest of the function.	This allows these functions to
	   be called from non-interworking code.  This option is not valid  in
	   AAPCS configurations	because	interworking is	enabled	by default.

       -mcaller-super-interworking
	   Allows calls	via function pointers (including virtual functions) to
	   execute  correctly  regardless  of whether the target code has been
	   compiled for	interworking or	not.  There is a small overhead	in the
	   cost	of executing a function	pointer	if  this  option  is  enabled.
	   This	  option   is	not  valid  in	AAPCS  configurations  because
	   interworking	is enabled by default.

       -mtp=name
	   Specify the access model for	the thread local storage pointer.  The
	   valid models	are soft, which	generates calls	to  "__aeabi_read_tp",
	   cp15,  which	 fetches  the  thread  pointer	from  "cp15"  directly
	   (supported in the arm6k architecture), and  auto,  which  uses  the
	   best	 available  method  for	 the  selected processor.  The default
	   setting is auto.

       -mtls-dialect=dialect
	   Specify the dialect to use for accessing thread local storage.  Two
	   dialects are	supported---gnu	and gnu2.  The gnu dialect selects the
	   original GNU	scheme for supporting local  and  global  dynamic  TLS
	   models.   The gnu2 dialect selects the GNU descriptor scheme, which
	   provides  better  performance  for  shared  libraries.    The   GNU
	   descriptor  scheme is compatible with the original scheme, but does
	   require new assembler, linker and  library  support.	  Initial  and
	   local  exec TLS models are unaffected by this option	and always use
	   the original	scheme.

       -mword-relocations
	   Only	generate  absolute  relocations	 on  word-sized	 values	 (i.e.
	   R_ARM_ABS32).   This	 is  enabled  by  default on targets (uClinux,
	   SymbianOS) where the	runtime	loader imposes this  restriction,  and
	   when	 -fpic	or  -fPIC  is  specified.  This	 option	conflicts with
	   -mslow-flash-data.

       -mfix-cortex-m3-ldrd
	   Some	 Cortex-M3  cores  can	cause  data  corruption	 when	"ldrd"
	   instructions	 with  overlapping  destination	and base registers are
	   used.  This option  avoids  generating  these  instructions.	  This
	   option is enabled by	default	when -mcpu=cortex-m3 is	specified.

       -munaligned-access
       -mno-unaligned-access
	   Enables (or disables) reading and writing of	16- and	32- bit	values
	   from	 addresses  that  are  not 16- or 32- bit aligned.  By default
	   unaligned access is disabled	for all	pre-ARMv6, all ARMv6-M and for
	   ARMv8-M  Baseline  architectures,  and  enabled   for   all	 other
	   architectures.   If	unaligned  access is not enabled then words in
	   packed data structures are accessed a byte at a time.

	   The	ARM  attribute	"Tag_CPU_unaligned_access"  is	set   in   the
	   generated  object  file to either true or false, depending upon the
	   setting of this option.  If unaligned access	is  enabled  then  the
	   preprocessor	symbol "__ARM_FEATURE_UNALIGNED" is also defined.

       -mneon-for-64bits
	   This	option is deprecated and has no	effect.

       -mslow-flash-data
	   Assume loading data from flash is slower than fetching instruction.
	   Therefore  literal  load is minimized for better performance.  This
	   option is only supported when compiling for ARMv7 M-profile and off
	   by default. It conflicts with -mword-relocations.

       -masm-syntax-unified
	   Assume inline assembler is using unified asm	syntax.	  The  default
	   is  currently off which implies divided syntax.  This option	has no
	   impact on Thumb2. However, this may change in  future  releases  of
	   GCC.	 Divided syntax	should be considered deprecated.

       -mrestrict-it
	   Restricts  generation  of  IT  blocks  to  conform  to the rules of
	   ARMv8-A.  IT	blocks can only	contain	a  single  16-bit  instruction
	   from	a select set of	instructions. This option is on	by default for
	   ARMv8-A Thumb mode.

       -mprint-tune-info
	   Print CPU tuning information	as comment in assembler	file.  This is
	   an  option used only	for regression testing of the compiler and not
	   intended for	ordinary  use  in  compiling  code.   This  option  is
	   disabled by default.

       -mverbose-cost-dump
	   Enable  verbose  cost  model	dumping	in the debug dump files.  This
	   option is provided for use in debugging the compiler.

       -mpure-code
	   Do  not  allow  constant  data  to  be  placed  in  code  sections.
	   Additionally,  when	compiling  for ELF object format give all text
	   sections   the    ELF    processor-specific	  section    attribute
	   "SHF_ARM_PURECODE".	 This option is	only available when generating
	   non-pic code	for M-profile targets.

       -mcmse
	   Generate secure code	 as  per  the  "ARMv8-M	 Security  Extensions:
	   Requirements	on Development Tools Engineering Specification", which
	   can			 be		     found		    on
	   <https://developer.arm.com/documentation/ecm0359818/latest/>.

       -mfix-cmse-cve-2021-35465
	   Mitigate against  a	potential  security  issue  with  the  "VLLDM"
	   instruction	 in   some   M-profile	 devices   when	  using	  CMSE
	   (CVE-2021-365465).  This option is  enabled	by  default  when  the
	   option   -mcpu=   is	  used	with  "cortex-m33",  "cortex-m35p"  or
	   "cortex-m55".  The option -mno-fix-cmse-cve-2021-35465 can be  used
	   to disable the mitigation.

       -mfdpic
       -mno-fdpic
	   Select  the	FDPIC  ABI,  which uses	64-bit function	descriptors to
	   represent pointers to functions.  When the compiler	is  configured
	   for	"arm-*-uclinuxfdpiceabi" targets, this option is on by default
	   and implies	-fPIE  if  none	 of  the  PIC/PIE-related  options  is
	   provided.   On  other  targets,  it only enables the	FDPIC-specific
	   code	generation features, and the user  should  explicitly  provide
	   the PIC/PIE-related options as needed.

	   Note	 that  static  linking is not supported	because	it would still
	   involve the dynamic linker when  the	 program  self-relocates.   If
	   such	 behavior  is  acceptable, use -static and -Wl,-dynamic-linker
	   options.

	   The opposite	-mno-fdpic option is useful (and  required)  to	 build
	   the	 Linux	 kernel	  using	 the  same  ("arm-*-uclinuxfdpiceabi")
	   toolchain as	the one	used to	build the userland programs.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
	   Specify Atmel AVR instruction set architectures (ISA) or MCU	type.

	   The default for this	option is avr2.

	   GCC supports	the following AVR devices and ISAs:

	   "avr2"
	       "Classic" devices with up to 8 KiB of program  memory.	mcu  =
	       "attiny22",  "attiny26",	"at90s2313", "at90s2323", "at90s2333",
	       "at90s2343",	"at90s4414",	 "at90s4433",	  "at90s4434",
	       "at90c8534", "at90s8515", "at90s8535".

	   "avr25"
	       "Classic"  devices  with	up to 8	KiB of program memory and with
	       the  "MOVW"  instruction.   mcu	=   "attiny13",	  "attiny13a",
	       "attiny24", "attiny24a",	"attiny25", "attiny261", "attiny261a",
	       "attiny2313",	 "attiny2313a",	   "attiny43u",	   "attiny44",
	       "attiny44a", "attiny45",	"attiny48", "attiny441",  "attiny461",
	       "attiny461a",	 "attiny4313",	   "attiny84",	  "attiny84a",
	       "attiny85", "attiny87", "attiny88",  "attiny828",  "attiny841",
	       "attiny861", "attiny861a", "ata5272", "ata6616c", "at86rf401".

	   "avr3"
	       "Classic"  devices  with	16 KiB up to 64	KiB of program memory.
	       mcu = "at76c711", "at43usb355".

	   "avr31"
	       "Classic" devices with  128  KiB	 of  program  memory.	mcu  =
	       "atmega103", "at43usb320".

	   "avr35"
	       "Classic"  devices  with	 16 KiB	up to 64 KiB of	program	memory
	       and  with  the  "MOVW"	instruction.	mcu   =	  "attiny167",
	       "attiny1634",	"atmega8u2",	"atmega16u2",	 "atmega32u2",
	       "ata5505", "ata6617c", "ata664251", "at90usb82",	"at90usb162".

	   "avr4"
	       "Enhanced" devices with up to 8 KiB of program memory.	mcu  =
	       "atmega48",     "atmega48a",	"atmega48p",	 "atmega48pa",
	       "atmega48pb", "atmega8",	"atmega8a", "atmega8hva",  "atmega88",
	       "atmega88a",	"atmega88p",	"atmega88pa",	 "atmega88pb",
	       "atmega8515", "atmega8535",  "ata6285",	"ata6286",  "ata6289",
	       "ata6612c",  "at90pwm1",	 "at90pwm2",  "at90pwm2b", "at90pwm3",
	       "at90pwm3b", "at90pwm81".

	   "avr5"
	       "Enhanced" devices with 16 KiB up to 64 KiB of program  memory.
	       mcu  =  "atmega16", "atmega16a",	"atmega16hva", "atmega16hva2",
	       "atmega16hvb", "atmega16hvbrevb",  "atmega16m1",	 "atmega16u4",
	       "atmega161",	"atmega162",	 "atmega163",	 "atmega164a",
	       "atmega164p",   "atmega164pa",	 "atmega165",	 "atmega165a",
	       "atmega165p",	"atmega165pa",	  "atmega168",	 "atmega168a",
	       "atmega168p",   "atmega168pa",	"atmega168pb",	  "atmega169",
	       "atmega169a",	"atmega169p",	 "atmega169pa",	   "atmega32",
	       "atmega32a",  "atmega32c1",  "atmega32hvb",  "atmega32hvbrevb",
	       "atmega32m1",	"atmega32u4",	 "atmega32u6",	  "atmega323",
	       "atmega324a",   "atmega324p",	"atmega324pa",	  "atmega325",
	       "atmega325a",	"atmega325p",	 "atmega325pa",	  "atmega328",
	       "atmega328p",   "atmega328pb",	 "atmega329",	 "atmega329a",
	       "atmega329p",   "atmega329pa",	"atmega3250",	"atmega3250a",
	       "atmega3250p",  "atmega3250pa",	"atmega3290",	"atmega3290a",
	       "atmega3290p",	 "atmega3290pa",    "atmega406",   "atmega64",
	       "atmega64a",   "atmega64c1",   "atmega64hve",   "atmega64hve2",
	       "atmega64m1",	"atmega64rfr2",	   "atmega640",	  "atmega644",
	       "atmega644a",  "atmega644p",  "atmega644pa",   "atmega644rfr2",
	       "atmega645",	"atmega645a",	 "atmega645p",	  "atmega649",
	       "atmega649a",   "atmega649p",   "atmega6450",	"atmega6450a",
	       "atmega6450p",	"atmega6490",	"atmega6490a",	"atmega6490p",
	       "ata5795",  "ata5790",	"ata5790n",   "ata5791",   "ata6613c",
	       "ata6614q",   "ata5782",	  "ata5831",   "ata8210",   "ata8510",
	       "ata5702m322",	"at90pwm161",	"at90pwm216",	 "at90pwm316",
	       "at90can32",	"at90can64",	"at90scr100",	 "at90usb646",
	       "at90usb647", "at94k", "m3000".

	   "avr51"
	       "Enhanced" devices with 128  KiB	 of  program  memory.	mcu  =
	       "atmega128",  "atmega128a",  "atmega128rfa1",  "atmega128rfr2",
	       "atmega1280",   "atmega1281",   "atmega1284",	"atmega1284p",
	       "atmega1284rfr2", "at90can128", "at90usb1286", "at90usb1287".

	   "avr6"
	       "Enhanced"  devices with	3-byte PC, i.e.	with more than 128 KiB
	       of  program  memory.   mcu  =  "atmega256rfr2",	 "atmega2560",
	       "atmega2561", "atmega2564rfr2".

	   "avrxmega2"
	       "XMEGA"	devices	 with  more  than  8  KiB  and up to 64	KiB of
	       program	 memory.    mcu	  =    "atxmega8e5",	"atxmega16a4",
	       "atxmega16a4u",	"atxmega16c4",	"atxmega16d4",	"atxmega16e5",
	       "atxmega32a4",  "atxmega32a4u",	"atxmega32c3",	"atxmega32c4",
	       "atxmega32d3", "atxmega32d4", "atxmega32e5".

	   "avrxmega3"
	       "XMEGA"	devices	 with  up to 64	KiB of combined	program	memory
	       and RAM,	and with program memory	visible	 in  the  RAM  address
	       space.	  mcu	=   "attiny202",   "attiny204",	  "attiny212",
	       "attiny214",	"attiny402",	 "attiny404",	  "attiny406",
	       "attiny412",	"attiny414",	 "attiny416",	  "attiny417",
	       "attiny804",	"attiny806",	 "attiny807",	  "attiny814",
	       "attiny816",	"attiny817",	"attiny1604",	 "attiny1606",
	       "attiny1607",   "attiny1614",	"attiny1616",	 "attiny1617",
	       "attiny3214",	"attiny3216",	 "attiny3217",	  "atmega808",
	       "atmega809",    "atmega1608",	"atmega1609",	 "atmega3208",
	       "atmega3209", "atmega4808", "atmega4809".

	   "avrxmega4"
	       "XMEGA"	devices	 with  more  than  64 KiB and up to 128	KiB of
	       program	 memory.    mcu	  =   "atxmega64a3",   "atxmega64a3u",
	       "atxmega64a4u",	"atxmega64b1",	"atxmega64b3",	"atxmega64c3",
	       "atxmega64d3", "atxmega64d4".

	   "avrxmega5"
	       "XMEGA" devices with more than 64 KiB and  up  to  128  KiB  of
	       program	 memory	  and	more  than  64	KiB  of	 RAM.	mcu  =
	       "atxmega64a1", "atxmega64a1u".

	   "avrxmega6"
	       "XMEGA" devices with more than 128 KiB of program memory.   mcu
	       =      "atxmega128a3",	  "atxmega128a3u",     "atxmega128b1",
	       "atxmega128b3", "atxmega128c3", "atxmega128d3", "atxmega128d4",
	       "atxmega192a3",	      "atxmega192a3u",	       "atxmega192c3",
	       "atxmega192d3",	       "atxmega256a3",	      "atxmega256a3b",
	       "atxmega256a3bu",       "atxmega256a3u",	       "atxmega256c3",
	       "atxmega256d3", "atxmega384c3", "atxmega384d3".

	   "avrxmega7"
	       "XMEGA"	devices	 with  more than 128 KiB of program memory and
	       more   than   64	  KiB	of   RAM.    mcu   =   "atxmega128a1",
	       "atxmega128a1u",	"atxmega128a4u".

	   "avrtiny"
	       "TINY"  Tiny  core  devices  with  512 B	up to 4	KiB of program
	       memory.	mcu =  "attiny4",  "attiny5",  "attiny9",  "attiny10",
	       "attiny20", "attiny40".

	   "avr1"
	       This  ISA  is implemented by the	minimal	AVR core and supported
	       for assembler only.  mcu	= "attiny11", "attiny12",  "attiny15",
	       "attiny28", "at90s1200".

       -mabsdata
	   Assume that all data	in static storage can be accessed by LDS / STS
	   instructions.   This	 option	 has  only  an	effect on reduced Tiny
	   devices  like  ATtiny40.   See  also	 the  "absdata"	 AVR  Variable
	   Attributes,variable attribute.

       -maccumulate-args
	   Accumulate  outgoing	 function  arguments  and  acquire/release the
	   needed stack	space for outgoing function arguments once in function
	   prologue/epilogue.  Without this  option,  outgoing	arguments  are
	   pushed before calling a function and	popped afterwards.

	   Popping  the	 arguments after the function call can be expensive on
	   AVR so that accumulating the	stack  space  might  lead  to  smaller
	   executables	because	 arguments  need not be	removed	from the stack
	   after such a	function call.

	   This	option can lead	 to  reduced  code  size  for  functions  that
	   perform  several calls to functions that get	their arguments	on the
	   stack like calls to printf-like functions.

       -mbranch-cost=cost
	   Set the branch costs	for conditional	branch instructions  to	 cost.
	   Reasonable  values  for  cost are small, non-negative integers. The
	   default branch cost is 0.

       -mcall-prologues
	   Functions prologues/epilogues are expanded as calls to  appropriate
	   subroutines.	 Code size is smaller.

       -mdouble=bits
       -mlong-double=bits
	   Set	the  size  (in	bits)  of  the "double"	or "long double" type,
	   respectively.  Possible values for bits are 32 and 64.  Whether  or
	   not	 a   specific  value  for  bits	 is  allowed  depends  on  the
	   "--with-double="   and   "--with-long-double="    configure options
	   ("https://gcc.gnu.org/install/configure.html#avr"),	and  the  same
	   applies for the default values of the options.

       -mgas-isr-prologues
	   Interrupt service routines (ISRs) may use  the  "__gcc_isr"	pseudo
	   instruction	supported  by GNU Binutils.  If	this option is on, the
	   feature can still be	disabled for individual	ISRs by	means  of  the
	   AVR	Function  Attributes,,"no_gccisr"  function  attribute.	  This
	   feature is activated	per default if optimization  is	 on  (but  not
	   with	 -Og,  @pxref{Optimize	Options}), and if GNU Binutils support
	   PR21683 ("https://sourceware.org/PR21683").

       -mint8
	   Assume "int"	to be 8-bit integer.  This affects the	sizes  of  all
	   types: a "char" is 1	byte, an "int" is 1 byte, a "long" is 2	bytes,
	   and	"long long" is 4 bytes.	 Please	note that this option does not
	   conform to the C standards, but it results in smaller code size.

       -mmain-is-OS_task
	   Do not save registers in "main".   The  effect  is  the  same  like
	   attaching  attribute	 AVR Function Attributes,,"OS_task" to "main".
	   It is activated per default if optimization is on.

       -mn-flash=num
	   Assume that the flash memory	has a size of num times	64 KiB.

       -mno-interrupts
	   Generated code is not compatible with  hardware  interrupts.	  Code
	   size	is smaller.

       -mrelax
	   Try	to  replace  "CALL"  resp.  "JMP"  instruction	by the shorter
	   "RCALL" resp. "RJMP"	instruction if	applicable.   Setting  -mrelax
	   just	 adds the --mlink-relax	option to the assembler's command line
	   and the --relax option to the linker's command line.

	   Jump	relaxing is performed by the linker because jump  offsets  are
	   not	known  before  code  is	located. Therefore, the	assembler code
	   generated by	the compiler is	the same, but the instructions in  the
	   executable may differ from instructions in the assembler code.

	   Relaxing  must  be  turned  on  if linker stubs are needed, see the
	   section on "EIND" and linker	stubs below.

       -mrmw
	   Assume that the device supports the Read-Modify-Write  instructions
	   "XCH", "LAC", "LAS" and "LAT".

       -mshort-calls
	   Assume that "RJMP" and "RCALL" can target the whole program memory.

	   This	 option	 is used internally for	multilib selection.  It	is not
	   an optimization option, and you don't need to set it	by hand.

       -msp8
	   Treat the stack pointer register as an 8-bit	register, i.e.	assume
	   the	high byte of the stack pointer is zero.	 In general, you don't
	   need	to set this option by hand.

	   This	option is used internally by the compiler to select and	 build
	   multilibs	for   architectures   "avr2"   and   "avr25".	 These
	   architectures mix devices with and without "SPH".  For any  setting
	   other  than	-mmcu=avr2  or -mmcu=avr25 the compiler	driver adds or
	   removes this	 option	 from  the  compiler  proper's	command	 line,
	   because  the	 compiler then knows if	the device or architecture has
	   an 8-bit stack pointer and thus no "SPH" register or	not.

       -mstrict-X
	   Use address register	"X" in a way proposed by the  hardware.	  This
	   means  that	"X"  is	 only used in indirect,	post-increment or pre-
	   decrement addressing.

	   Without this	option,	the "X"	register may be	used in	the  same  way
	   as  "Y"  or	"Z" which then is emulated by additional instructions.
	   For example,	loading	a value	with "X+const" addressing with a small
	   non-negative	"const < 64" to	a register Rn is performed as

		   adiw	r26, const   ; X += const
		   ld	<Rn>, X	       ; <Rn> =	*X
		   sbiw	r26, const   ; X -= const

       -mtiny-stack
	   Only	change the lower 8 bits	of the stack pointer.

       -mfract-convert-truncate
	   Allow to use	 truncation  instead  of  rounding  towards  zero  for
	   fractional fixed-point types.

       -nodevicelib
	   Don't link against AVR-LibC's device	specific library "lib<mcu>.a".

       -nodevicespecs
	   Don't  add  -specs=device-specs/specs-mcu  to the compiler driver's
	   command line.  The user takes responsibility	for supplying the sub-
	   processes  like  compiler  proper,  assembler   and	 linker	  with
	   appropriate	command	line options.  This means that the user	has to
	   supply her private device specs file	by  means  of  -specs=path-to-
	   specs-file.	There is no more need for option -mmcu=mcu.

	   This	 option	 can  also serve as a replacement for the older	way of
	   specifying custom device-specs files	that needed  -B	 some-path  to
	   point  to  a	directory which	contains a folder named	"device-specs"
	   which contains a  specs  file  named	 "specs-mcu",  where  mcu  was
	   specified by	-mmcu=mcu.

       -Waddr-space-convert
	   Warn	about conversions between address spaces in the	case where the
	   resulting  address  space  is not contained in the incoming address
	   space.

       -Wmisspelled-isr
	   Warn	if the	ISR  is	 misspelled,  i.e.  without  __vector  prefix.
	   Enabled by default.

       "EIND" and Devices with More Than 128 Ki	Bytes of Flash

       Pointers	 in  the  implementation  are  16 bits wide.  The address of a
       function	or label is represented	as word	address	so that	indirect jumps
       and calls can target any	code address in	the range of 64	Ki words.

       In order	to facilitate indirect jump on devices with more than  128  Ki
       bytes  of  program  memory  space, there	is a special function register
       called "EIND" that serves  as  most  significant	 part  of  the	target
       address when "EICALL" or	"EIJMP"	instructions are used.

       Indirect	jumps and calls	on these devices are handled as	follows	by the
       compiler	and are	subject	to some	limitations:

       *   The compiler	never sets "EIND".

       *   The	 compiler   uses   "EIND"   implicitly	 in   "EICALL"/"EIJMP"
	   instructions	or might read "EIND" directly in order to  emulate  an
	   indirect call/jump by means of a "RET" instruction.

       *   The	compiler  assumes that "EIND" never changes during the startup
	   code	or during  the	application.  In  particular,  "EIND"  is  not
	   saved/restored   in	 function   or	 interrupt   service   routine
	   prologue/epilogue.

       *   For indirect	calls to  functions  and  computed  goto,  the	linker
	   generates   stubs.  Stubs  are  jump	 pads  sometimes  also	called
	   trampolines.	Thus, the indirect call/jump jumps  to	such  a	 stub.
	   The stub contains a direct jump to the desired address.

       *   Linker  relaxation  must  be	turned on so that the linker generates
	   the stubs correctly in all  situations.  See	 the  compiler	option
	   -mrelax  and	 the  linker  option  --relax.	There are corner cases
	   where the linker is supposed	to generate stubs but  aborts  without
	   relaxation and without a helpful error message.

       *   The default linker script is	arranged for code with "EIND = 0".  If
	   code	 is  supposed  to  work	for a setup with "EIND != 0", a	custom
	   linker script has to	be used	in order to place the  sections	 whose
	   name	start with ".trampolines" into the segment where "EIND"	points
	   to.

       *   The	startup	 code  from  libgcc  never  sets  "EIND".  Notice that
	   startup code	is a blend of code from	libgcc and AVR-LibC.  For  the
	   impact   of	 AVR-LibC  on  "EIND",	see  the  AVR-LibC user	manual
	   ("http://nongnu.org/avr-libc/user-manual/").

       *   It is legitimate for	user-specific startup code to  set  up	"EIND"
	   early,  for	example	 by  means  of	initialization code located in
	   section ".init3". Such code runs prior to general startup code that
	   initializes RAM and	calls  constructors,  but  after  the  bit  of
	   startup  code  from	AVR-LibC that sets "EIND" to the segment where
	   the vector table is located.

		   #include <avr/io.h>

		   static void
		   __attribute__((section(".init3"),naked,used,no_instrument_function))
		   init3_set_eind (void)
		   {
		     __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
				     "out %i0,r24" :: "n" (&EIND) : "r24","memory");
		   }

	   The "__trampolines_start" symbol is defined in the linker script.

       *   Stubs are generated automatically by	the linker  if	the  following
	   two conditions are met:

	   -<The address of a label is taken by	means of the "gs" modifier>
	       (short for generate stubs) like so:

		       LDI r24,	lo8(gs(<func>))
		       LDI r25,	hi8(gs(<func>))

	   -<The final location	of that	label is in a code segment>
	       outside the segment where the stubs are located.

       *   The	compiler  emits	 such  "gs"  modifiers	for code labels	in the
	   following situations:

	   -<Taking address of a function or code label.>
	   -<Computed goto.>
	   -<If	prologue-save function is used,	see -mcall-prologues>
	       command-line option.

	   -<Switch/case dispatch tables. If you do not	want such dispatch>
	       tables  you  can	 specify  the  -fno-jump-tables	  command-line
	       option.

	   -<C and C++ constructors/destructors	called during
	   startup/shutdown.>
	   -<If	the tools hit a	"gs()" modifier	explained above.>
       *   Jumping to non-symbolic addresses like so is	not supported:

		   int main (void)
		   {
		       /* Call function	at word	address	0x2 */
		       return ((int(*)(void)) 0x2)();
		   }

	   Instead,  a	stub  has  to  be  set up, i.e.	the function has to be
	   called through a symbol ("func_4" in	the example):

		   int main (void)
		   {
		       extern int func_4 (void);

		       /* Call function	at byte	address	0x4 */
		       return func_4();
		   }

	   and	the  application  be  linked   with   -Wl,--defsym,func_4=0x4.
	   Alternatively, "func_4" can be defined in the linker	script.

       Handling	 of the	"RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function
       Registers

       Some AVR	devices	support	memories larger	than the 64 KiB	range that can
       be accessed with	16-bit pointers.  To access memory  locations  outside
       this  64	 KiB  range,  the content of a "RAMP" register is used as high
       part of the address: The	"X", "Y", "Z" address register is concatenated
       with  the  "RAMPX",  "RAMPY",  "RAMPZ"	special	  function   register,
       respectively,  to  get  a  wide	address.  Similarly,  "RAMPD"  is used
       together	with direct addressing.

       *   The startup code initializes	the "RAMP" special function  registers
	   with	zero.

       *   If  a  AVR  Named  Address  Spaces,named  address  space other than
	   generic or "__flash"	is used, then "RAMPZ" is set as	needed	before
	   the operation.

       *   If  the  device  supports  RAM  larger than 64 KiB and the compiler
	   needs to change "RAMPZ" to  accomplish  an  operation,  "RAMPZ"  is
	   reset to zero after the operation.

       *   If  the  device  comes  with	 a  specific  "RAMP" register, the ISR
	   prologue/epilogue saves/restores that SFR and initializes  it  with
	   zero	in case	the ISR	code might (implicitly)	use it.

       *   RAM larger than 64 KiB is not supported by GCC for AVR targets.  If
	   you	use inline assembler to	read from locations outside the	16-bit
	   address range and change one	of  the	 "RAMP"	 registers,  you  must
	   reset it to zero after the access.

       AVR Built-in Macros

       GCC  defines several built-in macros so that the	user code can test for
       the presence or absence of  features.   Almost  any  of	the  following
       built-in	macros are deduced from	device capabilities and	thus triggered
       by the -mmcu= command-line option.

       For even	more AVR-specific built-in macros see AVR Named	Address	Spaces
       and AVR Built-in	Functions.

       "__AVR_ARCH__"
	   Build-in  macro  that  resolves to a	decimal	number that identifies
	   the architecture and	depends	on  the	 -mmcu=mcu  option.   Possible
	   values are:

	   2, 25, 3, 31, 35, 4,	5, 51, 6

	   for	mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5",
	   "avr51", "avr6",

	   respectively	and

	   100,	102, 103, 104, 105, 106, 107

	   for	 mcu="avrtiny",	  "avrxmega2",	  "avrxmega3",	  "avrxmega4",
	   "avrxmega5",	  "avrxmega6",	 "avrxmega7",  respectively.   If  mcu
	   specifies a device, this built-in macro  is	set  accordingly.  For
	   example, with -mmcu=atmega8 the macro is defined to 4.

       "__AVR_Device__"
	   Setting -mmcu=device	defines	this built-in macro which reflects the
	   device's  name.  For	 example,  -mmcu=atmega8  defines the built-in
	   macro       "__AVR_ATmega8__",	-mmcu=attiny261a       defines
	   "__AVR_ATtiny261A__", etc.

	   The built-in	macros'	names follow the scheme	"__AVR_Device__" where
	   Device  is  the  device  name  as  from  the	 AVR  user manual. The
	   difference between Device in	 the  built-in	macro  and  device  in
	   -mmcu=device	is that	the latter is always lowercase.

	   If  device is not a device but only a core architecture like	avr51,
	   this	macro is not defined.

       "__AVR_DEVICE_NAME__"
	   Setting -mmcu=device	defines	this built-in macro  to	 the  device's
	   name.  For  example,	 with  -mmcu=atmega8  the  macro is defined to
	   "atmega8".

	   If device is	not a device but only a	core architecture like	avr51,
	   this	macro is not defined.

       "__AVR_XMEGA__"
	   The device /	architecture belongs to	the XMEGA family of devices.

       "__AVR_HAVE_ELPM__"
	   The device has the "ELPM" instruction.

       "__AVR_HAVE_ELPMX__"
	   The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

       "__AVR_HAVE_MOVW__"
	   The	device	has the	"MOVW" instruction to perform 16-bit register-
	   register moves.

       "__AVR_HAVE_LPMX__"
	   The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

       "__AVR_HAVE_MUL__"
	   The device has a hardware multiplier.

       "__AVR_HAVE_JMP_CALL__"
	   The device has the "JMP" and	"CALL" instructions.  This is the case
	   for devices with more than 8	KiB of program memory.

       "__AVR_HAVE_EIJMP_EICALL__"
       "__AVR_3_BYTE_PC__"
	   The device has the "EIJMP" and "EICALL" instructions.  This is  the
	   case	 for  devices  with more than 128 KiB of program memory.  This
	   also	means that the program counter (PC) is 3 bytes wide.

       "__AVR_2_BYTE_PC__"
	   The program counter (PC) is 2 bytes wide.  This  is	the  case  for
	   devices with	up to 128 KiB of program memory.

       "__AVR_HAVE_8BIT_SP__"
       "__AVR_HAVE_16BIT_SP__"
	   The	stack  pointer	(SP) register is treated as 8-bit respectively
	   16-bit register by the compiler.  The definition of these macros is
	   affected by -mtiny-stack.

       "__AVR_HAVE_SPH__"
       "__AVR_SP8__"
	   The device has  the	SPH  (high  part  of  stack  pointer)  special
	   function register or	has an 8-bit stack pointer, respectively.  The
	   definition  of  these macros	is affected by -mmcu= and in the cases
	   of -mmcu=avr2 and -mmcu=avr25 also by -msp8.

       "__AVR_HAVE_RAMPD__"
       "__AVR_HAVE_RAMPX__"
       "__AVR_HAVE_RAMPY__"
       "__AVR_HAVE_RAMPZ__"
	   The device has  the	"RAMPD",  "RAMPX",  "RAMPY",  "RAMPZ"  special
	   function register, respectively.

       "__NO_INTERRUPTS__"
	   This	macro reflects the -mno-interrupts command-line	option.

       "__AVR_ERRATA_SKIP__"
       "__AVR_ERRATA_SKIP_JMP_CALL__"
	   Some	 AVR  devices  (AT90S8515,  ATmega103)	must  not  skip	32-bit
	   instructions	because	of a hardware erratum.	Skip instructions  are
	   "SBRS",  "SBRC",  "SBIS",  "SBIC"  and "CPSE".  The second macro is
	   only	defined	if "__AVR_HAVE_JMP_CALL__" is also set.

       "__AVR_ISA_RMW__"
	   The device has Read-Modify-Write instructions (XCH,	LAC,  LAS  and
	   LAT).

       "__AVR_SFR_OFFSET__=offset"
	   Instructions	 that  can  address  I/O  special  function  registers
	   directly like "IN", "OUT", "SBI", etc. may use a different  address
	   as if addressed by an instruction to	access RAM like	"LD" or	"STS".
	   This	 offset	 depends  on  the  device  architecture	 and has to be
	   subtracted from the RAM address in order to get the respective  I/O
	   address.

       "__AVR_SHORT_CALLS__"
	   The -mshort-calls command line option is set.

       "__AVR_PM_BASE_ADDRESS__=addr"
	   Some	 devices  support  reading from	flash memory by	means of "LD*"
	   instructions.  The flash memory is seen in the data	address	 space
	   at  an  offset  of "__AVR_PM_BASE_ADDRESS__".  If this macro	is not
	   defined, this feature is not	available.  If	defined,  the  address
	   space  is  linear  and  there is no need to put ".rodata" into RAM.
	   This	is handled by the default  linker  description	file,  and  is
	   currently  available	 for  "avrtiny"	 and  "avrxmega3".   Even more
	   convenient, there is	no need	to use address spaces  like  "__flash"
	   or features like attribute "progmem"	and "pgm_read_*".

       "__WITH_AVRLIBC__"
	   The	compiler is configured to be used together with	AVR-Libc.  See
	   the --with-avrlibc configure	option.

       "__HAVE_DOUBLE_MULTILIB__"
	   Defined if -mdouble=	acts as	a multilib option.

       "__HAVE_DOUBLE32__"
       "__HAVE_DOUBLE64__"
	   Defined if the compiler supports 32-bit double resp.	64-bit double.
	   The actual layout is	specified by option -mdouble=.

       "__DEFAULT_DOUBLE__"
	   The size in bits of "double"	if -mdouble= is	not set.  To test  the
	   layout   of	 "double"   in	a  program,  use  the  built-in	 macro
	   "__SIZEOF_DOUBLE__".

       "__HAVE_LONG_DOUBLE32__"
       "__HAVE_LONG_DOUBLE64__"
       "__HAVE_LONG_DOUBLE_MULTILIB__"
       "__DEFAULT_LONG_DOUBLE__"
	   Same	as above, but for "long	double"	instead	of "double".

       "__WITH_DOUBLE_COMPARISON__"
	   Reflects    the    "--with-double-comparison={tristate|bool|libf7}"
	   configure option ("https://gcc.gnu.org/install/configure.html#avr")
	   and is defined to 2 or 3.

       "__WITH_LIBF7_LIBGCC__"
       "__WITH_LIBF7_MATH__"
       "__WITH_LIBF7_MATH_SYMBOLS__"
	   Reflects	   the	     "--with-libf7={libgcc|math|math-symbols}"
	   configure option
	   ("https://gcc.gnu.org/install/configure.html#avr").

       Blackfin	Options

       -mcpu=cpu[-sirevision]
	   Specifies the name of the target  Blackfin  processor.   Currently,
	   cpu	can be one of bf512, bf514, bf516, bf518, bf522, bf523,	bf524,
	   bf525, bf526, bf527,	bf531,	bf532,	bf533,	bf534,	bf536,	bf537,
	   bf538,  bf539,  bf542,  bf544, bf547, bf548,	bf549, bf542m, bf544m,
	   bf547m, bf548m, bf549m, bf561, bf592.

	   The optional	sirevision  specifies  the  silicon  revision  of  the
	   target  Blackfin  processor.	  Any  workarounds  available  for the
	   targeted silicon revision are enabled.  If sirevision is  none,  no
	   workarounds are enabled.  If	sirevision is any, all workarounds for
	   the	targeted  processor  are  enabled.  The	"__SILICON_REVISION__"
	   macro is defined to two hexadecimal digits representing  the	 major
	   and	minor numbers in the silicon revision.	If sirevision is none,
	   the "__SILICON_REVISION__" is not defined.  If sirevision  is  any,
	   the	"__SILICON_REVISION__"	is  defined  to	 be  0xffff.   If this
	   optional sirevision is not  used,  GCC  assumes  the	 latest	 known
	   silicon revision of the targeted Blackfin processor.

	   GCC	defines	 a  preprocessor macro for the specified cpu.  For the
	   bfin-elf toolchain, this option causes the hardware BSP provided by
	   libgloss to be linked in if -msim is	not given.

	   Without this	option,	bf532 is used as the processor by default.

	   Note	that support for bf561 is incomplete.	For  bf561,  only  the
	   preprocessor	macro is defined.

       -msim
	   Specifies  that  the	 program  will	be run on the simulator.  This
	   causes the simulator	BSP provided by	 libgloss  to  be  linked  in.
	   This	 option	has effect only	for bfin-elf toolchain.	 Certain other
	   options, such as -mid-shared-library	and -mfdpic, imply -msim.

       -momit-leaf-frame-pointer
	   Don't keep the frame	pointer	in  a  register	 for  leaf  functions.
	   This	 avoids	 the  instructions  to	save, set up and restore frame
	   pointers and	makes an extra register	available in leaf functions.

       -mspecld-anomaly
	   When	enabled, the compiler ensures that the generated code does not
	   contain speculative loads after jump	instructions. If  this	option
	   is used, "__WORKAROUND_SPECULATIVE_LOADS" is	defined.

       -mno-specld-anomaly
	   Don't  generate  extra  code	 to  prevent  speculative  loads  from
	   occurring.

       -mcsync-anomaly
	   When	enabled, the compiler ensures that the generated code does not
	   contain CSYNC or SSYNC  instructions	 too  soon  after  conditional
	   branches.  If this option is	used, "__WORKAROUND_SPECULATIVE_SYNCS"
	   is defined.

       -mno-csync-anomaly
	   Don't  generate  extra  code	to prevent CSYNC or SSYNC instructions
	   from	occurring too soon after a conditional branch.

       -mlow64k
	   When	enabled, the  compiler	is  free  to  take  advantage  of  the
	   knowledge that the entire program fits into the low 64k of memory.

       -mno-low64k
	   Assume that the program is arbitrarily large.  This is the default.

       -mstack-check-l1
	   Do  stack  checking	using  information  placed  into L1 scratchpad
	   memory by the uClinux kernel.

       -mid-shared-library
	   Generate code that supports shared libraries	 via  the  library  ID
	   method.   This  allows for execute in place and shared libraries in
	   an environment without  virtual  memory  management.	  This	option
	   implies -fPIC.  With	a bfin-elf target, this	option implies -msim.

       -mno-id-shared-library
	   Generate  code  that	 doesn't  assume ID-based shared libraries are
	   being used.	This is	the default.

       -mleaf-id-shared-library
	   Generate code that supports shared libraries	 via  the  library  ID
	   method,  but	 assumes  that	this  library or executable won't link
	   against any other ID	shared libraries.  That	allows the compiler to
	   use faster code for jumps and calls.

       -mno-leaf-id-shared-library
	   Do not assume that the code being compiled won't link  against  any
	   ID  shared  libraries.   Slower code	is generated for jump and call
	   insns.

       -mshared-library-id=n
	   Specifies the identification	number of the ID-based shared  library
	   being  compiled.   Specifying  a  value of 0	generates more compact
	   code; specifying other values forces	the allocation of that	number
	   to the current library but is no more space-	or time-efficient than
	   omitting this option.

       -msep-data
	   Generate  code  that	 allows	 the  data  segment to be located in a
	   different area of memory from the text segment.   This  allows  for
	   execute   in	  place	 in  an	 environment  without  virtual	memory
	   management by eliminating relocations against the text section.

       -mno-sep-data
	   Generate code that assumes that the data segment follows  the  text
	   segment.  This is the default.

       -mlong-calls
       -mno-long-calls
	   Tells  the  compiler	to perform function calls by first loading the
	   address of the function into	 a  register  and  then	 performing  a
	   subroutine  call  on	 this  register.  This switch is needed	if the
	   target function lies	outside	of the 24-bit addressing range of  the
	   offset-based	version	of subroutine call instruction.

	   This	feature	is not enabled by default.  Specifying -mno-long-calls
	   restores  the default behavior.  Note these switches	have no	effect
	   on how the compiler generates code to  handle  function  calls  via
	   function pointers.

       -mfast-fp
	   Link	 with  the  fast  floating-point library. This library relaxes
	   some	of the	IEEE  floating-point  standard's  rules	 for  checking
	   inputs against Not-a-Number (NAN), in the interest of performance.

       -minline-plt
	   Enable  inlining of PLT entries in function calls to	functions that
	   are not known to bind locally.  It has no effect without -mfdpic.

       -mmulticore
	   Build a standalone application for multicore	 Blackfin  processors.
	   This	 option	 causes	proper start files and link scripts supporting
	   multicore to	be used, and defines the macro "__BFIN_MULTICORE".  It
	   can only be used with -mcpu=bf561[-sirevision].

	   This	option can be used with	-mcorea	or -mcoreb, which selects  the
	   one-application-per-core  programming  model.   Without  -mcorea or
	   -mcoreb,  the  single-application/dual-core	programming  model  is
	   used. In this model,	the main function of Core B should be named as
	   "coreb_main".

	   If this option is not used, the single-core application programming
	   model is used.

       -mcorea
	   Build  a  standalone	application for	Core A of BF561	when using the
	   one-application-per-core programming	model. Proper start files  and
	   link	  scripts   are	  used	to  support  Core  A,  and  the	 macro
	   "__BFIN_COREA" is  defined.	 This  option  can  only  be  used  in
	   conjunction with -mmulticore.

       -mcoreb
	   Build  a  standalone	application for	Core B of BF561	when using the
	   one-application-per-core programming	model. Proper start files  and
	   link	  scripts   are	  used	to  support  Core  B,  and  the	 macro
	   "__BFIN_COREB" is defined. When this	option is  used,  "coreb_main"
	   should  be used instead of "main".  This option can only be used in
	   conjunction with -mmulticore.

       -msdram
	   Build a standalone application for SDRAM. Proper  start  files  and
	   link	 scripts  are  used to put the application into	SDRAM, and the
	   macro "__BFIN_SDRAM"	is  defined.   The  loader  should  initialize
	   SDRAM before	loading	the application.

       -micplb
	   Assume  that	ICPLBs are enabled at run time.	 This has an effect on
	   certain anomaly workarounds.	 For Linux targets, the	default	is  to
	   assume  ICPLBs are enabled; for standalone applications the default
	   is off.

       C6X Options

       -march=name
	   This	specifies the name of the target architecture.	GCC uses  this
	   name	 to  determine	what  kind  of	instructions  it can emit when
	   generating assembly	code.	Permissible  names  are:  c62x,	 c64x,
	   c64x+, c67x,	c67x+, c674x.

       -mbig-endian
	   Generate code for a big-endian target.

       -mlittle-endian
	   Generate code for a little-endian target.  This is the default.

       -msim
	   Choose startup files	and linker script suitable for the simulator.

       -msdata=default
	   Put	small global and static	data in	the ".neardata"	section, which
	   is pointed to by register "B14".  Put  small	 uninitialized	global
	   and	static	data  in  the ".bss" section, which is adjacent	to the
	   ".neardata" section.	 Put small read-only data into	the  ".rodata"
	   section.   The corresponding	sections used for large	pieces of data
	   are ".fardata", ".far" and ".const".

       -msdata=all
	   Put all data, not just small	objects, into  the  sections  reserved
	   for	small  data, and use addressing	relative to the	"B14" register
	   to access them.

       -msdata=none
	   Make	no use of the  sections	 reserved  for	small  data,  and  use
	   absolute  addresses to access all data.  Put	all initialized	global
	   and static data in the ".fardata" section,  and  all	 uninitialized
	   data	 in  the  ".far"  section.   Put  all  constant	 data into the
	   ".const" section.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
	   Generate code for the  specified  architecture.   The  choices  for
	   architecture-type  are  v3,	v8  and	 v10 for respectively ETRAX 4,
	   ETRAX 100, and ETRAX	100 LX.	 Default is v0.

       -mtune=architecture-type
	   Tune	to architecture-type everything	applicable about the generated
	   code, except	for the	ABI and	the  set  of  available	 instructions.
	   The	 choices   for	 architecture-type   are   the	 same  as  for
	   -march=architecture-type.

       -mmax-stack-frame=n
	   Warn	when the stack frame of	a function exceeds n bytes.

       -metrax4
       -metrax100
	   The options -metrax4	and -metrax100 are synonyms for	-march=v3  and
	   -march=v8 respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
	   Work	 around	 a  bug	 in the	"muls" and "mulu" instructions for CPU
	   models where	it applies.  This option is active by default.

       -mpdebug
	   Enable  CRIS-specific  verbose  debug-related  information  in  the
	   assembly  code.  This option	also has the effect of turning off the
	   #NO_APP formatted-code indicator to the assembler at	the  beginning
	   of the assembly file.

       -mcc-init
	   Do not use condition-code results from previous instruction;	always
	   emit	compare	and test instructions before use of condition codes.

       -mno-side-effects
	   Do  not  emit  instructions	with  side effects in addressing modes
	   other than post-increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
	   These options (no- options) arrange	(eliminate  arrangements)  for
	   the	stack  frame,  individual data and constants to	be aligned for
	   the maximum single data access size for the chosen CPU model.   The
	   default  is	to  arrange for	32-bit alignment.  ABI details such as
	   structure layout are	not affected by	these options.

       -m32-bit
       -m16-bit
       -m8-bit
	   Similar to the stack- data- and const-align	options	 above,	 these
	   options arrange for stack frame, writable data and constants	to all
	   be  32-bit,	16-bit	or  8-bit  aligned.   The  default  is	32-bit
	   alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
	   With	 -mno-prologue-epilogue,  the  normal  function	 prologue  and
	   epilogue  which  set	 up  the stack frame are omitted and no	return
	   instructions	or return sequences are	generated in  the  code.   Use
	   this	 option	 only  together	with visual inspection of the compiled
	   code: no warnings or	errors are generated when call-saved registers
	   must	 be  saved,  or	 storage  for  local  variables	 needs	to  be
	   allocated.

       -melf
	   Legacy no-op	option.

       -sim
	   This	 option	 arranges  to  link with input-output functions	from a
	   simulator library.  Code,  initialized  data	 and  zero-initialized
	   data	are allocated consecutively.

       -sim2
	   Like	 -sim,	but  pass linker options to locate initialized data at
	   0x40000000 and zero-initialized data	at 0x80000000.

       CR16 Options

       These options are defined specifically for the CR16 ports.

       -mmac
	   Enable the use of  multiply-accumulate  instructions.  Disabled  by
	   default.

       -mcr16cplus
       -mcr16c
	   Generate code for CR16C or CR16C+ architecture. CR16C+ architecture
	   is default.

       -msim
	   Links  the  library libsim.a	which is in compatible with simulator.
	   Applicable to ELF compiler only.

       -mint32
	   Choose integer type as 32-bit wide.

       -mbit-ops
	   Generates "sbit"/"cbit" instructions	for bit	manipulations.

       -mdata-model=model
	   Choose a data model.	The choices for	model are near,	far or medium.
	   medium is default.  However,	far is not valid with -mcr16c, as  the
	   CR16C architecture does not support the far data model.

       C-SKY Options

       GCC supports these options when compiling for C-SKY V2 processors.

       -march=arch
	   Specify  the	C-SKY target architecture.  Valid values for arch are:
	   ck801, ck802, ck803,	ck807, and ck810.  The default is ck810.

       -mcpu=cpu
	   Specify the C-SKY target processor.	 Valid	values	for  cpu  are:
	   ck801,  ck801t,  ck802,  ck802t,  ck802j,  ck803,  ck803h,  ck803t,
	   ck803ht,  ck803f,  ck803fh,	ck803e,	 ck803eh,  ck803et,  ck803eht,
	   ck803ef, ck803efh, ck803ft, ck803eft, ck803efht, ck803r1, ck803hr1,
	   ck803tr1,  ck803htr1,  ck803fr1,  ck803fhr1,	 ck803er1,  ck803ehr1,
	   ck803etr1,	ck803ehtr1,    ck803efr1,    ck803efhr1,    ck803ftr1,
	   ck803eftr1,	 ck803efhtr1,	ck803s,	  ck803st,  ck803se,  ck803sf,
	   ck803sef,  ck803seft,  ck807e,  ck807ef,  ck807,  ck807f,   ck810e,
	   ck810et, ck810ef, ck810eft, ck810, ck810v, ck810f, ck810t, ck810fv,
	   ck810tv, ck810ft, and ck810ftv.

       -mbig-endian
       -EB
       -mlittle-endian
       -EL Select big- or little-endian	code.  The default is little-endian.

       -mfloat-abi=name
	   Specifies which floating-point ABI to use.  Permissible values are:
	   soft, softfp	and hard.

	   Specifying  soft  causes  GCC to generate output containing library
	   calls for floating-point operations.	 softfp	allows the  generation
	   of  code using hardware floating-point instructions,	but still uses
	   the soft-float calling  conventions.	  hard	allows	generation  of
	   floating-point   instructions   and	 uses	FPU-specific   calling
	   conventions.

	   The default depends on the  specific	 target	 configuration.	  Note
	   that	 the  hard-float  and soft-float ABIs are not link-compatible;
	   you must compile your entire	program	with the same  ABI,  and  link
	   with	a compatible set of libraries.

       -mhard-float
       -msoft-float
	   Select  hardware  or	 software floating-point implementations.  The
	   default is soft float.

       -mdouble-float
       -mno-double-float
	   When	-mhard-float  is  in  effect,  enable  generation  of  double-
	   precision  float  instructions.   This  is  the default except when
	   compiling for CK803.

       -mfdivdu
       -mno-fdivdu
	   When	-mhard-float is	in effect,  enable  generation	of  "frecipd",
	   "fsqrtd",  and  "fdivd"  instructions.   This is the	default	except
	   when	compiling for CK803.

       -mfpu=fpu
	   Select the floating-point processor.	 This option can only be  used
	   with	 -mhard-float.	 Values	 for  fpu  are	fpv2_sf	(equivalent to
	   -mno-double-float -mno-fdivdu), fpv2	 (-mdouble-float  -mno-divdu),
	   and fpv2_divd (-mdouble-float -mdivdu).

       -melrw
       -mno-elrw
	   Enable  the extended	"lrw" instruction.  This option	defaults to on
	   for CK801 and off otherwise.

       -mistack
       -mno-istack
	   Enable interrupt stack instructions;	the default is off.

	   The -mistack	option is required to handle the "interrupt" and "isr"
	   function attributes.

       -mmp
	   Enable multiprocessor instructions; the default is off.

       -mcp
	   Enable coprocessor instructions; the	default	is off.

       -mcache
	   Enable coprocessor instructions; the	default	is off.

       -msecurity
	   Enable C-SKY	security instructions; the default is off.

       -mtrust
	   Enable C-SKY	trust instructions; the	default	is off.

       -mdsp
       -medsp
       -mvdsp
	   Enable  C-SKY  DSP,	Enhanced  DSP,	or  Vector  DSP	 instructions,
	   respectively.  All of these options default to off.

       -mdiv
       -mno-div
	   Generate divide instructions.  Default is off.

       -msmart
       -mno-smart
	   Generate  code for Smart Mode, using	only registers numbered	0-7 to
	   allow use of	16-bit instructions.  This option is ignored for CK801
	   where this is the required behavior,	and  it	 defaults  to  on  for
	   CK802.  For other targets, the default is off.

       -mhigh-registers
       -mno-high-registers
	   Generate code using the high	registers numbered 16-31.  This	option
	   is  not  supported  on  CK801,  CK802,  or CK803, and is enabled by
	   default for other processors.

       -manchor
       -mno-anchor
	   Generate code using global anchor symbol addresses.

       -mpushpop
       -mno-pushpop
	   Generate code using "push" and  "pop"  instructions.	  This	option
	   defaults to on.

       -mmultiple-stld
       -mstm
       -mno-multiple-stld
       -mno-stm
	   Generate  code  using  "stm"	 and  "ldm" instructions.  This	option
	   isn't supported on  CK801  but  is  enabled	by  default  on	 other
	   processors.

       -mconstpool
       -mno-constpool
	   Create  constant  pools  in the compiler instead of deferring it to
	   the assembler.  This	option is the default and required for correct
	   code	generation on CK801  and  CK802,  and  is  optional  on	 other
	   processors.

       -mstack-size
       -mno-stack-size
	   Emit	 ".stack_size"	directives  for	 each function in the assembly
	   output.  This option	defaults to off.

       -mccrt
       -mno-ccrt
	   Generate code for the C-SKY compiler	 runtime  instead  of  libgcc.
	   This	option defaults	to off.

       -mbranch-cost=n
	   Set	the  branch costs to roughly "n" instructions.	The default is
	   1.

       -msched-prolog
       -mno-sched-prolog
	   Permit scheduling of	 function  prologue  and  epilogue  sequences.
	   Using this option can result	in code	that is	not compliant with the
	   C-SKY  V2  ABI prologue requirements	and that cannot	be debugged or
	   backtraced.	It is disabled by default.

       -msim
	   Links the library libsemi.a which is	in compatible with  simulator.
	   Applicable to ELF compiler only.

       Darwin Options

       These  options  are  defined  for  all architectures running the	Darwin
       operating system.

       FSF GCC on Darwin does not create "fat" object  files;  it  creates  an
       object  file  for the single architecture that GCC was built to target.
       Apple's GCC on Darwin does create "fat" files if	multiple -arch options
       are used; it does so by running the compiler or linker  multiple	 times
       and joining the results together	with lipo.

       The  subtype  of	 the  file created (like ppc7400 or ppc970 or i686) is
       determined by the flags that specify the	ISA  that  GCC	is  targeting,
       like  -mcpu or -march.  The -force_cpusubtype_ALL option	can be used to
       override	this.

       The Darwin tools	vary in	their behavior	when  presented	 with  an  ISA
       mismatch.  The assembler, as, only permits instructions to be used that
       are  valid  for the subtype of the file it is generating, so you	cannot
       put 64-bit instructions in a ppc750 object file.	 The linker for	shared
       libraries, /usr/bin/libtool, fails and prints  an  error	 if  asked  to
       create  a shared	library	with a less restrictive	subtype	than its input
       files (for instance, trying to put a ppc970 object file	in  a  ppc7400
       library).  The linker for executables, ld, quietly gives	the executable
       the most	restrictive subtype of any of its input	files.

       -Fdir
	   Add	the  framework	directory  dir	to  the	 head  of  the list of
	   directories to be searched for header files.	 These directories are
	   interleaved with those specified by -I options and are scanned in a
	   left-to-right order.

	   A framework directory is a directory	 with  frameworks  in  it.   A
	   framework  is  a  directory	with  a	 Headers and/or	PrivateHeaders
	   directory contained directly	in it that ends	 in  .framework.   The
	   name	 of  a	framework  is the name of this directory excluding the
	   .framework.	Headers	associated with	the framework are found	in one
	   of those two	directories, with Headers  being  searched  first.   A
	   subframework	 is  a	framework  directory  that is in a framework's
	   Frameworks directory.  Includes of subframework  headers  can  only
	   appear  in  a header	of a framework that contains the subframework,
	   or  in  a  sibling  subframework  header.   Two  subframeworks  are
	   siblings  if	 they  occur  in  the  same framework.	A subframework
	   should not have the same name as a framework; a warning  is	issued
	   if	this  is  violated.   Currently	 a  subframework  cannot  have
	   subframeworks; in the future, the  mechanism	 may  be  extended  to
	   support   this.    The   standard   frameworks   can	 be  found  in
	   /System/Library/Frameworks  and  /Library/Frameworks.   An  example
	   include looks like "#include	<Framework/header.h>", where Framework
	   denotes  the	 name  of  the	framework and header.h is found	in the
	   PrivateHeaders or Headers directory.

       -iframeworkdir
	   Like	-F except the directory	is a treated as	 a  system  directory.
	   The	main  difference  between this -iframework and -F is that with
	   -iframework the compiler does not warn about	 constructs  contained
	   within  header  files found via dir.	 This option is	valid only for
	   the C family	of languages.

       -gused
	   Emit	debugging information for symbols that are  used.   For	 stabs
	   debugging  format,  this  enables -feliminate-unused-debug-symbols.
	   This	is by default ON.

       -gfull
	   Emit	debugging information for all symbols and types.

       -fconstant-cfstrings
	   The -fconstant-cfstrings is an alias	for -mconstant-cfstrings.

       -mconstant-cfstrings
	   When	the NeXT runtime is being used (the default on these systems),
	   override any	-fconstant-string-class	 setting  and  cause  "@"...""
	   literals to be laid out as constant CoreFoundation strings.

       -mmacosx-version-min=version
	   The earliest	version	of MacOS X that	this executable	will run on is
	   version.   Typical  values supported	for version include 12,	10.12,
	   and 10.5.8.

	   If the compiler was built to	use the	system's headers  by  default,
	   then	the default for	this option is the system version on which the
	   compiler  is	running, otherwise the default is to make choices that
	   are compatible with as many systems and code	bases as possible.

       -mkernel
	   Enable kernel development mode.  The	-mkernel option	sets  -static,
	   -fno-common,		 -fno-use-cxa-atexit,	      -fno-exceptions,
	   -fno-non-call-exceptions,  -fapple-kext,  -fno-weak	and  -fno-rtti
	   where  applicable.  This mode also sets -mno-altivec, -msoft-float,
	   -fno-builtin	and -mlong-branch for PowerPC targets.

       -mone-byte-bool
	   Override the	defaults for "bool"  so	 that  "sizeof(bool)==1".   By
	   default "sizeof(bool)" is 4 when compiling for Darwin/PowerPC and 1
	   when	compiling for Darwin/x86, so this option has no	effect on x86.

	   Warning:  The  -mone-byte-bool  switch  causes GCC to generate code
	   that	is not binary compatible  with	code  generated	 without  that
	   switch.   Using  this  switch  may  require	recompiling  all other
	   modules in a	program, including system libraries.  Use this	switch
	   to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
	   Generate  code suitable for fast turnaround development, such as to
	   allow  GDB  to  dynamically	load  .o  files	 into  already-running
	   programs.   -findirect-data and -ffix-and-continue are provided for
	   backwards compatibility.

       -all_load
	   Loads all members of	static archive libraries.  See man  ld(1)  for
	   more	information.

       -arch_errors_fatal
	   Cause  the  errors  having  to  do  with  files that	have the wrong
	   architecture	to be fatal.

       -bind_at_load
	   Causes the output file to be	marked such that  the  dynamic	linker
	   will	 bind  all  undefined  references  when	 the file is loaded or
	   launched.

       -bundle
	   Produce a Mach-o bundle  format  file.   See	 man  ld(1)  for  more
	   information.

       -bundle_loader executable
	   This	 option	 specifies  the	 executable  that  will	load the build
	   output file being linked.  See man ld(1) for	more information.

       -dynamiclib
	   When	passed this option, GCC	produces a dynamic library instead  of
	   an executable when linking, using the Darwin	libtool	command.

       -force_cpusubtype_ALL
	   This	 causes	 GCC's output file to have the ALL subtype, instead of
	   one controlled by the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
	   These options are passed to the Darwin linker.  The	Darwin	linker
	   man page describes them in detail.

       DEC Alpha Options

       These -m	options	are defined for	the DEC	Alpha implementations:

       -mno-soft-float
       -msoft-float
	   Use	(do  not  use)	the  hardware  floating-point instructions for
	   floating-point  operations.	 When	-msoft-float   is   specified,
	   functions   in   libgcc.a   are   used  to  perform	floating-point
	   operations.	Unless they are	replaced by routines that emulate  the
	   floating-point  operations,	or  compiled  in such a	way as to call
	   such	 emulations  routines,	these  routines	 issue	floating-point
	   operations.	  If  you are compiling	for an Alpha without floating-
	   point operations, you must ensure that the library is built	so  as
	   not to call them.

	   Note	 that  Alpha implementations without floating-point operations
	   are required	to have	floating-point registers.

       -mfp-reg
       -mno-fp-regs
	   Generate code that uses (does not use) the floating-point  register
	   set.	  -mno-fp-regs	implies	 -msoft-float.	 If the	floating-point
	   register set	is not used, floating-point  operands  are  passed  in
	   integer  registers  as  if  they  were  integers and	floating-point
	   results are passed in $0 instead of $f0.  This  is  a  non-standard
	   calling sequence, so	any function with a floating-point argument or
	   return value	called by code compiled	with -mno-fp-regs must also be
	   compiled with that option.

	   A  typical  use  of	this option is building	a kernel that does not
	   use,	and hence  need	 not  save  and	 restore,  any	floating-point
	   registers.

       -mieee
	   The Alpha architecture implements floating-point hardware optimized
	   for	maximum	 performance.	It  is	mostly compliant with the IEEE
	   floating-point standard.  However, for  full	 compliance,  software
	   assistance  is  required.   This  option generates code fully IEEE-
	   compliant code except that the inexact-flag is not maintained  (see
	   below).   If	 this  option  is  turned  on,	the preprocessor macro
	   "_IEEE_FP" is defined during	compilation.  The  resulting  code  is
	   less	 efficient  but	 is  able  to  correctly  support denormalized
	   numbers and	exceptional  IEEE  values  such	 as  not-a-number  and
	   plus/minus  infinity.   Other  Alpha	 compilers  call  this	option
	   -ieee_with_no_inexact.

       -mieee-with-inexact
	   This	is like	-mieee except the generated code  also	maintains  the
	   IEEE	 inexact-flag.	 Turning  on  this option causes the generated
	   code	to  implement  fully-compliant	IEEE  math.   In  addition  to
	   "_IEEE_FP",	"_IEEE_FP_EXACT"  is  defined as a preprocessor	macro.
	   On some  Alpha  implementations  the	 resulting  code  may  execute
	   significantly  slower  than	the  code generated by default.	 Since
	   there is very little	code that depends  on  the  inexact-flag,  you
	   should  normally  not  specify  this	option.	 Other Alpha compilers
	   call	this option -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
	   This	option controls	what floating-point related traps are enabled.
	   Other Alpha compilers call this option -fptm	trap-mode.   The  trap
	   mode	can be set to one of four values:

	   n   This  is	the default (normal) setting.  The only	traps that are
	       enabled are the ones that cannot	be disabled in software	(e.g.,
	       division	by zero	trap).

	   u   In addition to the traps	enabled	 by  n,	 underflow  traps  are
	       enabled as well.

	   su  Like u, but the instructions are	marked to be safe for software
	       completion (see Alpha architecture manual for details).

	   sui Like su,	but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
	   Selects  the	 IEEE  rounding	mode.  Other Alpha compilers call this
	   option -fprm	rounding-mode.	The rounding-mode can be one of:

	   n   Normal IEEE rounding mode.  Floating-point numbers are  rounded
	       towards	the nearest machine number or towards the even machine
	       number in case of a tie.

	   m   Round towards minus infinity.

	   c   Chopped rounding	 mode.	 Floating-point	 numbers  are  rounded
	       towards zero.

	   d   Dynamic	rounding  mode.	 A field in the	floating-point control
	       register	 (fpcr,	 see  Alpha  architecture  reference   manual)
	       controls	  the	rounding   mode	 in  effect.   The  C  library
	       initializes this	register for rounding towards  plus  infinity.
	       Thus,  unless  your program modifies the	fpcr, d	corresponds to
	       round towards plus infinity.

       -mtrap-precision=trap-precision
	   In the Alpha	 architecture,	floating-point	traps  are  imprecise.
	   This	 means without software	assistance it is impossible to recover
	   from	a floating trap	and program execution  normally	 needs	to  be
	   terminated.	GCC can	generate code that can assist operating	system
	   trap	 handlers  in  determining  the	 exact	location that caused a
	   floating-point  trap.   Depending  on  the	requirements   of   an
	   application,	different levels of precisions can be selected:

	   p   Program precision.  This	option is the default and means	a trap
	       handler can only	identify which program caused a	floating-point
	       exception.

	   f   Function	  precision.   The  trap  handler  can	determine  the
	       function	that caused a floating-point exception.

	   i   Instruction precision.  The  trap  handler  can	determine  the
	       exact instruction that caused a floating-point exception.

	   Other   Alpha  compilers  provide  the  equivalent  options	called
	   -scope_safe and -resumption_safe.

       -mieee-conformant
	   This	option marks the generated code	as IEEE	conformant.  You  must
	   not	use this option	unless you also	specify	-mtrap-precision=i and
	   either -mfp-trap-mode=su or -mfp-trap-mode=sui.  Its	only effect is
	   to emit the	line  .eflag  48  in  the  function  prologue  of  the
	   generated assembly file.

       -mbuild-constants
	   Normally GCC	examines a 32- or 64-bit integer constant to see if it
	   can	 construct   it	  from	smaller	 constants  in	two  or	 three
	   instructions.  If it	cannot,	it outputs the constant	as  a  literal
	   and generates code to load it from the data segment at run time.

	   Use	this  option to	require	GCC to construct all integer constants
	   using code, even if it takes	 more  instructions  (the  maximum  is
	   six).

	   You	typically  use	this  option to	build a	shared library dynamic
	   loader.  Itself a shared library, it	must relocate itself in	memory
	   before it can find the variables and	 constants  in	its  own  data
	   segment.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
	   Indicate  whether GCC should	generate code to use the optional BWX,
	   CIX,	FIX and	MAX instruction	sets.	The  default  is  to  use  the
	   instruction	sets  supported	 by  the CPU type specified via	-mcpu=
	   option or that of the CPU  on  which	 GCC  was  built  if  none  is
	   specified.

       -mfloat-vax
       -mfloat-ieee
	   Generate  code  that	uses (does not use) VAX	F and G	floating-point
	   arithmetic instead of IEEE single and double	precision.

       -mexplicit-relocs
       -mno-explicit-relocs
	   Older  Alpha	 assemblers  provided  no  way	to   generate	symbol
	   relocations	except via assembler macros.  Use of these macros does
	   not allow optimal  instruction  scheduling.	 GNU  binutils	as  of
	   version  2.12  supports  a  new  syntax that	allows the compiler to
	   explicitly  mark  which   relocations   should   apply   to	 which
	   instructions.   This	 option	is mostly useful for debugging,	as GCC
	   detects the capabilities of the assembler when it is	built and sets
	   the default accordingly.

       -msmall-data
       -mlarge-data
	   When	-mexplicit-relocs is in	effect,	static data  is	 accessed  via
	   gp-relative	relocations.   When  -msmall-data  is  used, objects 8
	   bytes long or smaller are placed in a small data area (the ".sdata"
	   and ".sbss" sections) and are accessed via 16-bit  relocations  off
	   of  the  $gp	register.  This	limits the size	of the small data area
	   to 64KB, but	allows the variables to	be  directly  accessed	via  a
	   single instruction.

	   The	default	 is  -mlarge-data.   With this option the data area is
	   limited to just below 2GB.  Programs	that require more than 2GB  of
	   data	 must  use "malloc" or "mmap" to allocate the data in the heap
	   instead of in the program's data segment.

	   When	 generating  code  for	 shared	  libraries,   -fpic   implies
	   -msmall-data	and -fPIC implies -mlarge-data.

       -msmall-text
       -mlarge-text
	   When	 -msmall-text  is  used, the compiler assumes that the code of
	   the entire program (or shared library) fits in  4MB,	 and  is  thus
	   reachable  with  a  branch instruction.  When -msmall-data is used,
	   the compiler	can assume that	all local symbols share	the  same  $gp
	   value,  and	thus  reduce the number	of instructions	required for a
	   function call from 4	to 1.

	   The default is -mlarge-text.

       -mcpu=cpu_type
	   Set the instruction set and instruction scheduling  parameters  for
	   machine type	cpu_type.  You can specify either the EV style name or
	   the	corresponding chip number.  GCC	supports scheduling parameters
	   for the EV4,	EV5 and	EV6  family  of	 processors  and  chooses  the
	   default  values  for	 the  instruction  set	from the processor you
	   specify.  If	you do not specify a processor type, GCC  defaults  to
	   the processor on which the compiler was built.

	   Supported values for	cpu_type are

	   ev4
	   ev45
	   21064
	       Schedules as an EV4 and has no instruction set extensions.

	   ev5
	   21164
	       Schedules as an EV5 and has no instruction set extensions.

	   ev56
	   21164a
	       Schedules as an EV5 and supports	the BWX	extension.

	   pca56
	   21164pc
	   21164PC
	       Schedules as an EV5 and supports	the BWX	and MAX	extensions.

	   ev6
	   21264
	       Schedules  as  an  EV6  and  supports  the  BWX,	 FIX,  and MAX
	       extensions.

	   ev67
	   21264a
	       Schedules as an EV6 and supports	the BWX,  CIX,	FIX,  and  MAX
	       extensions.

	   Native  toolchains also support the value native, which selects the
	   best	architecture option for	the host processor.  -mcpu=native  has
	   no effect if	GCC does not recognize the processor.

       -mtune=cpu_type
	   Set	only  the  instruction	scheduling parameters for machine type
	   cpu_type.  The instruction set is not changed.

	   Native toolchains also support the value native, which selects  the
	   best	architecture option for	the host processor.  -mtune=native has
	   no effect if	GCC does not recognize the processor.

       -mmemory-latency=time
	   Sets	 the  latency  the  scheduler should assume for	typical	memory
	   references as seen by  the  application.   This  number  is	highly
	   dependent on	the memory access patterns used	by the application and
	   the size of the external cache on the machine.

	   Valid options for time are

	   number
	       A decimal number	representing clock cycles.

	   L1
	   L2
	   L3
	   main
	       The  compiler  contains estimates of the	number of clock	cycles
	       for "typical" EV4 & EV5 hardware	for the	Level 1, 2 & 3	caches
	       (also  called  Dcache,  Scache, and Bcache), as well as to main
	       memory.	Note that L3 is	only valid for EV5.

       eBPF Options

       -mframe-limit=bytes
	   This	 specifies  the	 hard  limit  for  frame  sizes,   in	bytes.
	   Currently,  the  value that can be specified	should be less than or
	   equal to 32767.  Defaults to	 whatever  limit  is  imposed  by  the
	   version of the Linux	kernel targeted.

       -mkernel=version
	   This	 specifies the minimum version of the kernel that will run the
	   compiled  program.	GCC  uses  this	 version  to  determine	 which
	   instructions	to use,	what kernel helpers to allow, etc.  Currently,
	   version  can	be one of 4.0, 4.1, 4.2, 4.3, 4.4, 4.5,	4.6, 4.7, 4.8,
	   4.9,	4.10, 4.11, 4.12, 4.13,	4.14, 4.15, 4.16,  4.17,  4.18,	 4.19,
	   4.20, 5.0, 5.1, 5.2,	latest and native.

       -mbig-endian
	   Generate code for a big-endian target.

       -mlittle-endian
	   Generate code for a little-endian target.  This is the default.

       -mxbpf
	   Generate code for an	expanded version of BPF, which relaxes some of
	   the restrictions imposed by the BPF architecture:

	   -<Save and restore callee-saved registers at	function entry and>
	       exit, respectively.

       FR30 Options

       These options are defined specifically for the FR30 port.

       -msmall-model
	   Use	the small address space	model.	This can produce smaller code,
	   but it does assume that all symbolic	values and addresses fit  into
	   a 20-bit range.

       -mno-lsim
	   Assume  that	 runtime  support has been provided and	so there is no
	   need	to include the simulator  library  (libsim.a)  on  the	linker
	   command line.

       FT32 Options

       These options are defined specifically for the FT32 port.

       -msim
	   Specifies  that  the	 program  will	be run on the simulator.  This
	   causes an alternate runtime startup and library to be linked.   You
	   must	 not use this option when generating programs that will	run on
	   real	hardware; you  must  provide  your  own	 runtime  library  for
	   whatever I/O	functions are needed.

       -mlra
	   Enable  Local  Register Allocation.	This is	still experimental for
	   FT32, so by default the compiler uses standard reload.

       -mnodiv
	   Do not use div and mod instructions.

       -mft32b
	   Enable use of the extended instructions of the FT32B	processor.

       -mcompress
	   Compress all	code using the Ft32B code compression scheme.

       -mnopm
	   Do not generate code	that reads program memory.

       FRV Options

       -mgpr-32
	   Only	use the	first 32 general-purpose registers.

       -mgpr-64
	   Use all 64 general-purpose registers.

       -mfpr-32
	   Use only the	first 32 floating-point	registers.

       -mfpr-64
	   Use all 64 floating-point registers.

       -mhard-float
	   Use hardware	instructions for floating-point	operations.

       -msoft-float
	   Use library routines	for floating-point operations.

       -malloc-cc
	   Dynamically allocate	condition code registers.

       -mfixed-cc
	   Do not try to dynamically allocate condition	code  registers,  only
	   use "icc0" and "fcc0".

       -mdword
	   Change ABI to use double word insns.

       -mno-dword
	   Do not use double word instructions.

       -mdouble
	   Use floating-point double instructions.

       -mno-double
	   Do not use floating-point double instructions.

       -mmedia
	   Use media instructions.

       -mno-media
	   Do not use media instructions.

       -mmuladd
	   Use multiply	and add/subtract instructions.

       -mno-muladd
	   Do not use multiply and add/subtract	instructions.

       -mfdpic
	   Select  the FDPIC ABI, which	uses function descriptors to represent
	   pointers to functions.  Without  any	 PIC/PIE-related  options,  it
	   implies  -fPIE.   With  -fpic  or -fpie, it assumes GOT entries and
	   small data are within a 12-bit range	from  the  GOT	base  address;
	   with	-fPIC or -fPIE,	GOT offsets are	computed with 32 bits.	With a
	   bfin-elf target, this option	implies	-msim.

       -minline-plt
	   Enable  inlining of PLT entries in function calls to	functions that
	   are not known to bind locally.  It has no effect  without  -mfdpic.
	   It's	 enabled  by default if	optimizing for speed and compiling for
	   shared libraries (i.e., -fPIC or -fpic), or	when  an  optimization
	   option such as -O3 or above is present in the command line.

       -mTLS
	   Assume a large TLS segment when generating thread-local code.

       -mtls
	   Do  not  assume  a  large  TLS segment when generating thread-local
	   code.

       -mgprel-ro
	   Enable the use of "GPREL" relocations in the	 FDPIC	ABI  for  data
	   that	 is  known  to	be  in	read-only  sections.   It's enabled by
	   default, except for -fpic or	-fpie: even though it  may  help  make
	   the	global	offset	table  smaller,	it trades 1 instruction	for 4.
	   With	-fPIC or -fPIE,	it trades 3 instructions for 4,	one  of	 which
	   may be shared by multiple symbols, and it avoids the	need for a GOT
	   entry  for  the referenced symbol, so it's more likely to be	a win.
	   If it is not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
	   Link	with the (library, not FD) pic	libraries.   It's  implied  by
	   -mlibrary-pic,  as well as by -fPIC and -fpic without -mfdpic.  You
	   should never	have to	use it explicitly.

       -mlinked-fp
	   Follow the EABI requirement of  always  creating  a	frame  pointer
	   whenever  a	stack  frame  is allocated.  This option is enabled by
	   default and can be disabled with -mno-linked-fp.

       -mlong-calls
	   Use indirect	addressing  to	call  functions	 outside  the  current
	   compilation	unit.  This allows the functions to be placed anywhere
	   within the 32-bit address space.

       -malign-labels
	   Try to align	labels to an 8-byte boundary by	 inserting  NOPs  into
	   the	previous  packet.   This  option  only has an effect when VLIW
	   packing is enabled.	It doesn't create new packets; it merely  adds
	   NOPs	to existing ones.

       -mlibrary-pic
	   Generate position-independent EABI code.

       -macc-4
	   Use only the	first four media accumulator registers.

       -macc-8
	   Use all eight media accumulator registers.

       -mpack
	   Pack	VLIW instructions.

       -mno-pack
	   Do not pack VLIW instructions.

       -mno-eflags
	   Do not mark ABI switches in e_flags.

       -mcond-move
	   Enable the use of conditional-move instructions (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-cond-move
	   Disable the use of conditional-move instructions.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mscc
	   Enable the use of conditional set instructions (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-scc
	   Disable the use of conditional set instructions.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mcond-exec
	   Enable the use of conditional execution (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-cond-exec
	   Disable the use of conditional execution.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mvliw-branch
	   Run a pass to pack branches into VLIW instructions (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-vliw-branch
	   Do not run a	pass to	pack branches into VLIW	instructions.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mmulti-cond-exec
	   Enable  optimization	 of  "&&"  and	"||"  in conditional execution
	   (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-multi-cond-exec
	   Disable optimization	of "&&"	and "||" in conditional	execution.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mnested-cond-exec
	   Enable nested conditional execution optimizations (default).

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -mno-nested-cond-exec
	   Disable nested conditional execution	optimizations.

	   This	switch is mainly for debugging the compiler and	will likely be
	   removed in a	future version.

       -moptimize-membar
	   This	 switch	 removes  redundant  "membar"  instructions  from  the
	   compiler-generated code.  It	is enabled by default.

       -mno-optimize-membar
	   This	 switch	 disables  the automatic removal of redundant "membar"
	   instructions	from the generated code.

       -mtomcat-stats
	   Cause gas to	print out tomcat statistics.

       -mcpu=cpu
	   Select the processor	type for which	to  generate  code.   Possible
	   values  are	frv,  fr550, tomcat, fr500, fr450, fr405, fr400, fr300
	   and simple.

       GNU/Linux Options

       These -m	options	are defined for	GNU/Linux targets:

       -mglibc
	   Use	the  GNU  C  library.	This  is   the	 default   except   on
	   *-*-linux-*uclibc*,	  *-*-linux-*musl*   and   *-*-linux-*android*
	   targets.

       -muclibc
	   Use uClibc C	library.  This is the  default	on  *-*-linux-*uclibc*
	   targets.

       -mmusl
	   Use	the  musl  C library.  This is the default on *-*-linux-*musl*
	   targets.

       -mbionic
	   Use Bionic C	library.  This is the default  on  *-*-linux-*android*
	   targets.

       -mandroid
	   Compile code	compatible with	Android	platform.  This	is the default
	   on *-*-linux-*android* targets.

	   When	   compiling,	 this	 option	  enables   -mbionic,	-fPIC,
	   -fno-exceptions and	-fno-rtti  by  default.	  When	linking,  this
	   option  makes  the  GCC driver pass Android-specific	options	to the
	   linker.   Finally,  this  option  causes  the  preprocessor	 macro
	   "__ANDROID__" to be defined.

       -tno-android-cc
	   Disable  compilation	 effects  of  -mandroid,  i.e.,	 do not	enable
	   -mbionic, -fPIC, -fno-exceptions and	-fno-rtti by default.

       -tno-android-ld
	   Disable linking effects of -mandroid,  i.e.,	 pass  standard	 Linux
	   linking options to the linker.

       H8/300 Options

       These -m	options	are defined for	the H8/300 implementations:

       -mrelax
	   Shorten  some  address references at	link time, when	possible; uses
	   the linker option -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in  the  normal  mode.	  This
	   switch must be used either with -mh or -ms.

       -ms2600
	   Generate code for the H8S/2600.  This switch	must be	used with -ms.

       -mexr
	   Extended registers are stored on stack before execution of function
	   with	 monitor  attribute.  Default option is	-mexr.	This option is
	   valid only for H8S targets.

       -mno-exr
	   Extended registers are not stored  on  stack	 before	 execution  of
	   function  with monitor attribute. Default option is -mno-exr.  This
	   option is valid only	for H8S	targets.

       -mint32
	   Make	"int" data 32 bits by default.

       -malign-300
	   On the H8/300H and H8S, use the same	alignment  rules  as  for  the
	   H8/300.   The default for the H8/300H and H8S is to align longs and
	   floats on 4-byte boundaries.	 -malign-300 causes them to be aligned
	   on 2-byte boundaries.  This option has no effect on the H8/300.

       HPPA Options

       These -m	options	are defined for	the HPPA family	of computers:

       -march=architecture-type
	   Generate code for the  specified  architecture.   The  choices  for
	   architecture-type  are  1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for
	   PA 2.0 processors.  Refer  to  /usr/lib/sched.models	 on  an	 HP-UX
	   system  to  determine  the  proper  architecture  option  for  your
	   machine.  Code compiled for lower numbered  architectures  runs  on
	   higher numbered architectures, but not the other way	around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
	   Synonyms for	-march=1.0, -march=1.1,	and -march=2.0 respectively.

       -mcaller-copies
	   The	caller	copies	function arguments passed by hidden reference.
	   This	option should be used with care	as it is not  compatible  with
	   the	default	 32-bit	runtime.  However, only	aggregates larger than
	   eight bytes are passed by hidden reference and the option  provides
	   better compatibility	with OpenMP.

       -mjump-in-delay
	   This	 option	 is  ignored  and  provided for	compatibility purposes
	   only.

       -mdisable-fpregs
	   Prevent floating-point registers from being	used  in  any  manner.
	   This	 is  necessary for compiling kernels that perform lazy context
	   switching of	floating-point registers.  If you use this option  and
	   attempt to perform floating-point operations, the compiler aborts.

       -mdisable-indexing
	   Prevent  the	 compiler  from	 using	indexing  address modes.  This
	   avoids some rather obscure problems when  compiling	MIG  generated
	   code	under MACH.

       -mno-space-regs
	   Generate code that assumes the target has no	space registers.  This
	   allows GCC to generate faster indirect calls	and use	unscaled index
	   address modes.

	   Such	code is	suitable for level 0 PA	systems	and kernels.

       -mfast-indirect-calls
	   Generate  code  that	 assumes  calls	 never cross space boundaries.
	   This	allows GCC to emit code	that performs faster indirect calls.

	   This	option does not	work in	the presence of	 shared	 libraries  or
	   nested functions.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A  fixed  register  is  one that the	register allocator cannot use.
	   This	is useful when compiling kernel	code.	A  register  range  is
	   specified  as two registers separated by a dash.  Multiple register
	   ranges can be specified separated by	a comma.

       -mlong-load-store
	   Generate  3-instruction  load  and  store  sequences	 as  sometimes
	   required  by	 the  HP-UX  10	 linker.  This is equivalent to	the +k
	   option to the HP compilers.

       -mportable-runtime
	   Use the  portable  calling  conventions  proposed  by  HP  for  ELF
	   systems.

       -mgas
	   Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
	   Schedule  code  according  to  the constraints for the machine type
	   cpu-type.  The choices for cpu-type are  700	 7100,	7100LC,	 7200,
	   7300	 and  8000.  Refer to /usr/lib/sched.models on an HP-UX	system
	   to determine	the proper scheduling option for  your	machine.   The
	   default scheduling is 8000.

       -mlinker-opt
	   Enable  the optimization pass in the	HP-UX linker.  Note this makes
	   symbolic debugging impossible.  It also triggers a bug in the HP-UX
	   8 and HP-UX 9 linkers in which they give bogus error	messages  when
	   linking some	programs.

       -msoft-float
	   Generate  output  containing	 library  calls	 for  floating	point.
	   Warning: the	requisite libraries are	not  available	for  all  HPPA
	   targets.  Normally the facilities of	the machine's usual C compiler
	   are	used,  but  this cannot	be done	directly in cross-compilation.
	   You must make your own arrangements	to  provide  suitable  library
	   functions for cross-compilation.

	   -msoft-float	 changes  the  calling	convention in the output file;
	   therefore, it is only useful	if you compile all of a	 program  with
	   this	 option.   In  particular,  you	 need to compile libgcc.a, the
	   library that	comes with GCC,	with -msoft-float in order for this to
	   work.

       -msio
	   Generate the	predefine, "_SIO", for	server	IO.   The  default  is
	   -mwsio.     This    generates   the	 predefines,   "__hp9000s700",
	   "__hp9000s700__" and	"_WSIO", for workstation  IO.	These  options
	   are available under HP-UX and HI-UX.

       -mgnu-ld
	   Use	options	 specific  to  GNU ld.	This passes -shared to ld when
	   building  a	shared	library.   It  is  the	default	 when  GCC  is
	   configured,	explicitly  or	implicitly, with the GNU linker.  This
	   option does not affect which	ld is called;  it  only	 changes  what
	   parameters  are  passed  to	that  ld.   The	 ld  that is called is
	   determined by the --with-ld configure option, GCC's program	search
	   path,  and  finally by the user's PATH.  The	linker used by GCC can
	   be printed using which `gcc -print-prog-name=ld`.  This  option  is
	   only	 available  on	the  64-bit  HP-UX  GCC,  i.e. configured with
	   hppa*64*-*-hpux*.

       -mhp-ld
	   Use options specific	to HP ld.  This	passes -b to ld	when  building
	   a  shared  library  and  passes  +Accept  TypeMismatch to ld	on all
	   links.  It is the default when GCC  is  configured,	explicitly  or
	   implicitly,	with the HP linker.  This option does not affect which
	   ld is called; it only changes what parameters are  passed  to  that
	   ld.	The ld that is called is determined by the --with-ld configure
	   option,  GCC's program search path, and finally by the user's PATH.
	   The	linker	used  by  GCC  can  be	printed	  using	  which	  `gcc
	   -print-prog-name=ld`.   This	option is only available on the	64-bit
	   HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

       -mlong-calls
	   Generate code that uses long	call sequences.	 This ensures  that  a
	   call	 is  always able to reach linker generated stubs.  The default
	   is to generate long calls only when the distance from the call site
	   to the beginning of the function or translation unit, as  the  case
	   may	be,  exceeds  a	 predefined limit set by the branch type being
	   used.  The limits for normal	calls are 7,600,000 and	240,000	bytes,
	   respectively	for the	PA 2.0 and PA 1.X architectures.  Sibcalls are
	   always limited at 240,000 bytes.

	   Distances are measured from the beginning of	functions  when	 using
	   the	-ffunction-sections  option,  or  when	using  the  -mgas  and
	   -mno-portable-runtime options together under	 HP-UX	with  the  SOM
	   linker.

	   It  is  normally  not  desirable  to	use this option	as it degrades
	   performance.	 However, it may  be  useful  in  large	 applications,
	   particularly	when partial linking is	used to	build the application.

	   The	types  of  long	 calls used depends on the capabilities	of the
	   assembler and linker, and the type of code  being  generated.   The
	   impact  on  systems	that support long absolute calls, and long pic
	   symbol-difference or	pc-relative calls should be relatively	small.
	   However, an indirect	call is	used on	32-bit ELF systems in pic code
	   and it is quite long.

       -munix=unix-std
	   Generate  compiler  predefines  and	select	a  startfile  for  the
	   specified UNIX standard.  The choices for unix-std are 93,  95  and
	   98.	93 is supported	on all HP-UX versions.	95 is available	on HP-
	   UX 10.10 and	later.	98 is available	on HP-UX 11.11 and later.  The
	   default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to
	   11.00, and 98 for HP-UX 11.11 and later.

	   -munix=93  provides	the  same  predefines  as  GCC	3.3  and  3.4.
	   -munix=95  provides	additional  predefines	for  "XOPEN_UNIX"  and
	   "_XOPEN_SOURCE_EXTENDED",  and  the	startfile unix95.o.  -munix=98
	   provides	additional     predefines      for	"_XOPEN_UNIX",
	   "_XOPEN_SOURCE_EXTENDED",	   "_INCLUDE__STDC_A1_SOURCE"	   and
	   "_INCLUDE_XOPEN_SOURCE_500",	and the	startfile unix98.o.

	   It is important to note that	this option changes the	interfaces for
	   various library routines.  It also affects the operational behavior
	   of the C library.  Thus, extreme  care  is  needed  in  using  this
	   option.

	   Library  code  that	is intended to operate with more than one UNIX
	   standard   must   test,    set    and    restore    the    variable
	   "__xpg4_extended_mask"  as  appropriate.  Most GNU software doesn't
	   provide this	capability.

       -nolibdld
	   Suppress the	generation of link options to  search  libdld.sl  when
	   the -static option is specified on HP-UX 10 and later.

       -static
	   The	HP-UX  implementation of setlocale in libc has a dependency on
	   libdld.sl.  There isn't an archive  version	of  libdld.sl.	 Thus,
	   when	 the  -static  option  is  specified, special link options are
	   needed to resolve this dependency.

	   On HP-UX 10 and later, the GCC driver adds the necessary options to
	   link	with libdld.sl when the	-static	 option	 is  specified.	  This
	   causes the resulting	binary to be dynamic.  On the 64-bit port, the
	   linkers  generate  dynamic  binaries	 by  default in	any case.  The
	   -nolibdld option can	be used	to prevent the GCC driver from	adding
	   these link options.

       -threads
	   Add	support	 for  multithreading with the dce thread library under
	   HP-UX.  This	option	sets  flags  for  both	the  preprocessor  and
	   linker.

       IA-64 Options

       These are the -m	options	defined	for the	Intel IA-64 architecture.

       -mbig-endian
	   Generate code for a big-endian target.  This	is the default for HP-
	   UX.

       -mlittle-endian
	   Generate  code for a	little-endian target.  This is the default for
	   AIX5	and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
	   Generate (or	don't) code  for  the  GNU  assembler.	 This  is  the
	   default.

       -mgnu-ld
       -mno-gnu-ld
	   Generate (or	don't) code for	the GNU	linker.	 This is the default.

       -mno-pic
	   Generate  code  that	 does  not use a global	pointer	register.  The
	   result is not position independent code,  and  violates  the	 IA-64
	   ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
	   Generate  (or  don't)  a  stop  bit	immediately  before  and after
	   volatile asm	statements.

       -mregister-names
       -mno-register-names
	   Generate (or	don't) in, loc,	and out	register names for the stacked
	   registers.  This may	make assembler output more readable.

       -mno-sdata
       -msdata
	   Disable (or enable) optimizations that use the small	data  section.
	   This	may be useful for working around optimizer bugs.

       -mconstant-gp
	   Generate  code  that	 uses  a single	constant global	pointer	value.
	   This	is useful when compiling kernel	code.

       -mauto-pic
	   Generate   code   that   is	 self-relocatable.     This    implies
	   -mconstant-gp.  This	is useful when compiling firmware code.

       -minline-float-divide-min-latency
	   Generate code for inline divides of floating-point values using the
	   minimum latency algorithm.

       -minline-float-divide-max-throughput
	   Generate code for inline divides of floating-point values using the
	   maximum throughput algorithm.

       -mno-inline-float-divide
	   Do not generate inline code for divides of floating-point values.

       -minline-int-divide-min-latency
	   Generate  code  for	inline	divides	 of  integer  values using the
	   minimum latency algorithm.

       -minline-int-divide-max-throughput
	   Generate code for  inline  divides  of  integer  values  using  the
	   maximum throughput algorithm.

       -mno-inline-int-divide
	   Do not generate inline code for divides of integer values.

       -minline-sqrt-min-latency
	   Generate  code  for	inline	square roots using the minimum latency
	   algorithm.

       -minline-sqrt-max-throughput
	   Generate code for inline square roots using the maximum  throughput
	   algorithm.

       -mno-inline-sqrt
	   Do not generate inline code for "sqrt".

       -mfused-madd
       -mno-fused-madd
	   Do  (don't)	generate  code	that  uses  the	 fused multiply/add or
	   multiply/subtract  instructions.   The  default  is	to  use	 these
	   instructions.

       -mno-dwarf2-asm
       -mdwarf2-asm
	   Don't  (or  do)  generate  assembler	code for the DWARF line	number
	   debugging info.   This  may	be  useful  when  not  using  the  GNU
	   assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
	   Allow stop bits to be placed	earlier	than immediately preceding the
	   instruction	 that  triggered  the  stop  bit.   This  can  improve
	   instruction scheduling, but does not	always do so.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A fixed register is one that	the  register  allocator  cannot  use.
	   This	 is  useful  when  compiling kernel code.  A register range is
	   specified as	two registers separated	by a dash.  Multiple  register
	   ranges can be specified separated by	a comma.

       -mtls-size=tls-size
	   Specify  bit	 size  of immediate TLS	offsets.  Valid	values are 14,
	   22, and 64.

       -mtune=cpu-type
	   Tune	the instruction	scheduling for a particular CPU, Valid	values
	   are itanium,	itanium1, merced, itanium2, and	mckinley.

       -milp32
       -mlp64
	   Generate  code  for	a  32-bit  or  64-bit environment.  The	32-bit
	   environment sets int, long and pointer  to  32  bits.   The	64-bit
	   environment	sets  int  to 32 bits and long and pointer to 64 bits.
	   These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
	   (Dis/En)able	 data  speculative  scheduling	before	reload.	  This
	   results  in generation of "ld.a" instructions and the corresponding
	   check instructions ("ld.c" /	 "chk.a").   The  default  setting  is
	   disabled.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
	   (En/Dis)able	  data	speculative  scheduling	 after	reload.	  This
	   results in generation of "ld.a" instructions	and the	 corresponding
	   check  instructions	("ld.c"	 /  "chk.a").	The default setting is
	   enabled.

       -mno-sched-control-spec
       -msched-control-spec
	   (Dis/En)able	 control  speculative  scheduling.   This  feature  is
	   available only during region	scheduling (i.e. before	reload).  This
	   results   in	  generation   of  the	"ld.s"	instructions  and  the
	   corresponding check instructions "chk.s".  The default  setting  is
	   disabled.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
	   (En/Dis)able	 speculative  scheduling  of the instructions that are
	   dependent on	the data speculative loads  before  reload.   This  is
	   effective  only  with  -msched-br-data-spec	enabled.   The default
	   setting is enabled.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
	   (En/Dis)able	speculative scheduling of the  instructions  that  are
	   dependent  on  the  data  speculative  loads	after reload.  This is
	   effective only  with	 -msched-ar-data-spec  enabled.	  The  default
	   setting is enabled.

       -msched-in-control-spec
       -mno-sched-in-control-spec
	   (En/Dis)able	 speculative  scheduling  of the instructions that are
	   dependent on	the control speculative	loads.	This is	effective only
	   with	-msched-control-spec enabled.  The default setting is enabled.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
	   If enabled, data-speculative	instructions are chosen	 for  schedule
	   only	 if  there are no other	choices	at the moment.	This makes the
	   use of the data speculation much more  conservative.	  The  default
	   setting is disabled.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
	   If	enabled,   control-speculative	instructions  are  chosen  for
	   schedule only if there are no other choices at  the	moment.	  This
	   makes  the  use  of the control speculation much more conservative.
	   The default setting is disabled.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
	   If  enabled,	 speculative  dependencies   are   considered	during
	   computation	of the instructions priorities.	 This makes the	use of
	   the speculation a bit more conservative.  The  default  setting  is
	   disabled.

       -msched-spec-ldc
	   Use a simple	data speculation check.	 This option is	on by default.

       -msched-control-spec-ldc
	   Use	a  simple check	for control speculation.  This option is on by
	   default.

       -msched-stop-bits-after-every-cycle
	   Place a stop	bit after every	cycle when scheduling.	This option is
	   on by default.

       -msched-fp-mem-deps-zero-cost
	   Assume that floating-point stores and loads are not likely to cause
	   a conflict when placed  into	 the  same  instruction	 group.	  This
	   option is disabled by default.

       -msel-sched-dont-check-control-spec
	   Generate  checks  for  control speculation in selective scheduling.
	   This	flag is	disabled by default.

       -msched-max-memory-insns=max-insns
	   Limit on the	number of memory insns per instruction	group,	giving
	   lower priority to subsequent	memory insns attempting	to schedule in
	   the same instruction	group. Frequently useful to prevent cache bank
	   conflicts.  The default value is 1.

       -msched-max-memory-insns-hard-limit
	   Makes  the limit specified by msched-max-memory-insns a hard	limit,
	   disallowing	more  than  that  number  in  an  instruction	group.
	   Otherwise,  the limit is "soft", meaning that non-memory operations
	   are preferred when the limit	is reached, but	memory operations  may
	   still be scheduled.

       LM32 Options

       These -m	options	are defined for	the LatticeMico32 architecture:

       -mbarrel-shift-enabled
	   Enable barrel-shift instructions.

       -mdivide-enabled
	   Enable divide and modulus instructions.

       -mmultiply-enabled
	   Enable multiply instructions.

       -msign-extend-enabled
	   Enable sign extend instructions.

       -muser-enabled
	   Enable user-defined instructions.

       M32C Options

       -mcpu=name
	   Select the CPU for which code is generated.	name may be one	of r8c
	   for	the  R8C/Tiny  series,	m16c  for the M16C (up to /60) series,
	   m32cm for the M16C/80 series, or m32c for the M32C/80 series.

       -msim
	   Specifies that the program will be  run  on	the  simulator.	  This
	   causes an alternate runtime library to be linked in which supports,
	   for	example,  file	I/O.   You  must  not  use  this  option  when
	   generating programs that  will  run	on  real  hardware;  you  must
	   provide  your  own  runtime	library	for whatever I/O functions are
	   needed.

       -memregs=number
	   Specifies the number	 of  memory-based  pseudo-registers  GCC  uses
	   during  code	generation.  These pseudo-registers are	used like real
	   registers, so there is a tradeoff between GCC's ability to fit  the
	   code	into available registers, and the performance penalty of using
	   memory  instead  of	registers.  Note that all modules in a program
	   must	be compiled with the same value	for this option.   Because  of
	   that,  you  must  not  use  this  option with GCC's default runtime
	   libraries.

       M32R/D Options

       These -m	options	are defined for	Renesas	M32R/D architectures:

       -m32r2
	   Generate code for the M32R/2.

       -m32rx
	   Generate code for the M32R/X.

       -m32r
	   Generate code for the M32R.	This is	the default.

       -mmodel=small
	   Assume all objects live in the lower	16MB of	memory (so that	 their
	   addresses  can  be  loaded with the "ld24" instruction), and	assume
	   all subroutines are reachable with the "bl" instruction.   This  is
	   the default.

	   The	addressability	of  a  particular  object  can be set with the
	   "model" attribute.

       -mmodel=medium
	   Assume objects may be anywhere in the  32-bit  address  space  (the
	   compiler   generates	  "seth/add3"	instructions   to  load	 their
	   addresses), and assume all subroutines are reachable	with the  "bl"
	   instruction.

       -mmodel=large
	   Assume  objects  may	 be  anywhere in the 32-bit address space (the
	   compiler  generates	"seth/add3"   instructions   to	  load	 their
	   addresses),	and  assume  subroutines may not be reachable with the
	   "bl"	 instruction  (the  compiler   generates   the	 much	slower
	   "seth/add3/jl" instruction sequence).

       -msdata=none
	   Disable  use	of the small data area.	 Variables are put into	one of
	   ".data", ".bss", or ".rodata" (unless the "section"	attribute  has
	   been	specified).  This is the default.

	   The	small  data  area  consists  of	sections ".sdata" and ".sbss".
	   Objects may be explicitly put in  the  small	 data  area  with  the
	   "section" attribute using one of these sections.

       -msdata=sdata
	   Put small global and	static data in the small data area, but	do not
	   generate special code to reference them.

       -msdata=use
	   Put	small  global  and  static  data  in  the small	data area, and
	   generate special instructions to reference them.

       -G num
	   Put global and static objects less than or equal to num bytes  into
	   the	small  data  or	BSS sections instead of	the normal data	or BSS
	   sections.  The default value	of num is 8.  The -msdata option  must
	   be set to one of sdata or use for this option to have any effect.

	   All	modules	 should	 be  compiled  with  the  same	-G  num	value.
	   Compiling with different values of num may or may not work;	if  it
	   doesn't  the	 linker	gives an error message---incorrect code	is not
	   generated.

       -mdebug
	   Makes  the  M32R-specific  code  in	the  compiler	display	  some
	   statistics that might help in debugging programs.

       -malign-loops
	   Align all loops to a	32-byte	boundary.

       -mno-align-loops
	   Do not enforce a 32-byte alignment for loops.  This is the default.

       -missue-rate=number
	   Issue number	instructions per cycle.	 number	can only be 1 or 2.

       -mbranch-cost=number
	   number  can only be 1 or 2.	If it is 1 then	branches are preferred
	   over	conditional code, if it	is 2, then the opposite	applies.

       -mflush-trap=number
	   Specifies the trap number to	use to flush the cache.	  The  default
	   is 12.  Valid numbers are between 0 and 15 inclusive.

       -mno-flush-trap
	   Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
	   Specifies  the  name	 of  the  operating system function to call to
	   flush the cache.  The default is _flush_cache, but a	function  call
	   is only used	if a trap is not available.

       -mno-flush-func
	   Indicates that there	is no OS function for flushing the cache.

       M680x0 Options

       These  are  the	-m options defined for M680x0 and ColdFire processors.
       The default settings depend on which architecture was selected when the
       compiler	was configured;	the defaults for the most common  choices  are
       given below.

       -march=arch
	   Generate  code  for	a  specific M680x0 or ColdFire instruction set
	   architecture.  Permissible values of	arch for M680x0	 architectures
	   are:	 68000,	68010, 68020, 68030, 68040, 68060 and cpu32.  ColdFire
	   architectures   are	 selected   according	to   Freescale's   ISA
	   classification and the permissible values are: isaa,	isaaplus, isab
	   and isac.

	   GCC	defines	 a  macro "__mcfarch__"	whenever it is generating code
	   for a ColdFire target.  The arch in this macro is one of the	-march
	   arguments given above.

	   When	used together, -march and -mtune select	code that  runs	 on  a
	   family of similar processors	but that is optimized for a particular
	   microarchitecture.

       -mcpu=cpu
	   Generate  code  for	a  specific M680x0 or ColdFire processor.  The
	   M680x0 cpus are: 68000, 68010, 68020, 68030,	68040,	68060,	68302,
	   68332  and  cpu32.  The ColdFire cpus are given by the table	below,
	   which also classifies the CPUs into families:

	   Family : -mcpu arguments
	   51 :	51 51ac	51ag 51cn 51em 51je 51jf 51jg 51jm 51mm	51qe 51qm
	   5206	: 5202 5204 5206
	   5206e : 5206e
	   5208	: 5207 5208
	   5211a : 5210a 5211a
	   5213	: 5211 5212 5213
	   5216	: 5214 5216
	   52235 : 52230 52231 52232 52233 52234 52235
	   5225	: 5224 5225
	   52259 : 52252 52254 52255 52256 52258 52259
	   5235	: 5232 5233 5234 5235 523x
	   5249	: 5249
	   5250	: 5250
	   5271	: 5270 5271
	   5272	: 5272
	   5275	: 5274 5275
	   5282	: 5280 5281 5282 528x
	   53017 : 53011 53012 53013 53014 53015 53016 53017
	   5307	: 5307
	   5329	: 5327 5328 5329 532x
	   5373	: 5372 5373 537x
	   5407	: 5407
	   5475	: 5470 5471 5472 5473 5474 5475	547x 5480 5481 5482 5483 5484
	   5485

	   -mcpu=cpu overrides -march=arch if arch  is	compatible  with  cpu.
	   Other combinations of -mcpu and -march are rejected.

	   GCC	defines	 the macro "__mcf_cpu_cpu" when	ColdFire target	cpu is
	   selected.  It also defines "__mcf_family_family", where  the	 value
	   of family is	given by the table above.

       -mtune=tune
	   Tune	 the  code  for	 a  particular	microarchitecture  within  the
	   constraints set by -march and -mcpu.	 The M680x0 microarchitectures
	   are:	68000, 68010, 68020,  68030,  68040,  68060  and  cpu32.   The
	   ColdFire microarchitectures are: cfv1, cfv2,	cfv3, cfv4 and cfv4e.

	   You	can  also  use	-mtune=68020-40	 for  code  that  needs	to run
	   relatively well on 68020, 68030 and 68040 targets.  -mtune=68020-60
	   is similar but includes 68060 targets as well.  These  two  options
	   select  the	same  tuning  decisions	 as  -m68020-40	and -m68020-60
	   respectively.

	   GCC defines the macros "__mcarch" and "__mcarch__" when tuning  for
	   680x0  architecture	arch.	It also	defines	"mcarch" unless	either
	   -ansi or a non-GNU -std option is used.  If GCC  is	tuning	for  a
	   range   of	architectures,	 as  selected  by  -mtune=68020-40  or
	   -mtune=68020-60, it defines the macros for  every  architecture  in
	   the range.

	   GCC	also  defines  the macro "__muarch__" when tuning for ColdFire
	   microarchitecture uarch, where uarch	is one of the arguments	 given
	   above.

       -m68000
       -mc68000
	   Generate output for a 68000.	 This is the default when the compiler
	   is  configured  for	68000-based  systems.	It  is	equivalent  to
	   -march=68000.

	   Use this option for microcontrollers	with a 68000  or  EC000	 core,
	   including the 68008,	68302, 68306, 68307, 68322, 68328 and 68356.

       -m68010
	   Generate output for a 68010.	 This is the default when the compiler
	   is  configured  for	68010-based  systems.	It  is	equivalent  to
	   -march=68010.

       -m68020
       -mc68020
	   Generate output for a 68020.	 This is the default when the compiler
	   is  configured  for	68020-based  systems.	It  is	equivalent  to
	   -march=68020.

       -m68030
	   Generate output for a 68030.	 This is the default when the compiler
	   is  configured  for	68030-based  systems.	It  is	equivalent  to
	   -march=68030.

       -m68040
	   Generate output for a 68040.	 This is the default when the compiler
	   is  configured  for	68040-based  systems.	It  is	equivalent  to
	   -march=68040.

	   This	 option	inhibits the use of 68881/68882	instructions that have
	   to be emulated by software on the 68040.  Use this option  if  your
	   68040 does not have code to emulate those instructions.

       -m68060
	   Generate output for a 68060.	 This is the default when the compiler
	   is  configured  for	68060-based  systems.	It  is	equivalent  to
	   -march=68060.

	   This	option inhibits	the use	of 68020 and 68881/68882  instructions
	   that	have to	be emulated by software	on the 68060.  Use this	option
	   if your 68060 does not have code to emulate those instructions.

       -mcpu32
	   Generate output for a CPU32.	 This is the default when the compiler
	   is  configured  for	CPU32-based  systems.	It  is	equivalent  to
	   -march=cpu32.

	   Use this option for microcontrollers	with a CPU32 or	 CPU32+	 core,
	   including  the  68330,  68331,  68332,  68333, 68334, 68336,	68340,
	   68341, 68349	and 68360.

       -m5200
	   Generate output for a 520X ColdFire CPU.  This is the default  when
	   the	 compiler   is	configured  for	 520X-based  systems.	It  is
	   equivalent to -mcpu=5206, and is now	deprecated in  favor  of  that
	   option.

	   Use this option for microcontroller with a 5200 core, including the
	   MCF5202, MCF5203, MCF5204 and MCF5206.

       -m5206e
	   Generate  output  for  a  5206e  ColdFire  CPU.   The option	is now
	   deprecated in favor of the equivalent -mcpu=5206e.

       -m528x
	   Generate output for a member	of  the	 ColdFire  528X	 family.   The
	   option is now deprecated in favor of	the equivalent -mcpu=528x.

       -m5307
	   Generate  output  for  a  ColdFire  5307  CPU.   The	 option	is now
	   deprecated in favor of the equivalent -mcpu=5307.

       -m5407
	   Generate output for	a  ColdFire  5407  CPU.	  The  option  is  now
	   deprecated in favor of the equivalent -mcpu=5407.

       -mcfv4e
	   Generate  output  for  a  ColdFire V4e family CPU (e.g. 547x/548x).
	   This	includes use of	 hardware  floating-point  instructions.   The
	   option  is equivalent to -mcpu=547x,	and is now deprecated in favor
	   of that option.

       -m68020-40
	   Generate  output  for  a  68040,  without  using  any  of  the  new
	   instructions.   This	 results  in  code  that  can  run  relatively
	   efficiently on either a 68020/68881 or a 68030  or  a  68040.   The
	   generated code does use the 68881 instructions that are emulated on
	   the 68040.

	   The option is equivalent to -march=68020 -mtune=68020-40.

       -m68020-60
	   Generate  output  for  a  68060,  without  using  any  of  the  new
	   instructions.   This	 results  in  code  that  can  run  relatively
	   efficiently	on  either  a  68020/68881 or a	68030 or a 68040.  The
	   generated code does use the 68881 instructions that are emulated on
	   the 68060.

	   The option is equivalent to -march=68020 -mtune=68020-60.

       -mhard-float
       -m68881
	   Generate floating-point instructions.   This	 is  the  default  for
	   68020  and  above,  and  for	ColdFire devices that have an FPU.  It
	   defines  the	 macro	"__HAVE_68881__"   on	M680x0	 targets   and
	   "__mcffpu__"	on ColdFire targets.

       -msoft-float
	   Do  not  generate  floating-point  instructions;  use library calls
	   instead.  This is the default for 68000, 68010, and 68832  targets.
	   It is also the default for ColdFire devices that have no FPU.

       -mdiv
       -mno-div
	   Generate  (do  not generate)	ColdFire hardware divide and remainder
	   instructions.  If -march is used without -mcpu, the default is "on"
	   for ColdFire	architectures  and  "off"  for	M680x0	architectures.
	   Otherwise,  the  default  is	 taken from the	target CPU (either the
	   default CPU,	or the one specified  by  -mcpu).   For	 example,  the
	   default is "off" for	-mcpu=5206 and "on" for	-mcpu=5206e.

	   GCC defines the macro "__mcfhwdiv__"	when this option is enabled.

       -mshort
	   Consider  type  "int"  to  be  16  bits  wide,  like	 "short	 int".
	   Additionally, parameters passed on the stack	are also aligned to  a
	   16-bit  boundary  even  on  targets whose API mandates promotion to
	   32-bit.

       -mno-short
	   Do not consider type	"int"  to  be  16  bits	 wide.	 This  is  the
	   default.

       -mnobitfield
       -mno-bitfield
	   Do  not  use	 the bit-field instructions.  The -m68000, -mcpu32 and
	   -m5200 options imply	-mnobitfield.

       -mbitfield
	   Do use the bit-field	 instructions.	 The  -m68020  option  implies
	   -mbitfield.	 This  is  the	default	 if  you  use  a configuration
	   designed for	a 68020.

       -mrtd
	   Use a different function-calling  convention,  in  which  functions
	   that	 take  a  fixed	 number	 of  arguments	return	with the "rtd"
	   instruction,	which pops  their  arguments  while  returning.	  This
	   saves  one  instruction in the caller since there is	no need	to pop
	   the arguments there.

	   This	calling	convention is incompatible with	the one	normally  used
	   on  Unix,  so  you  cannot  use  it	if  you	need to	call libraries
	   compiled with the Unix compiler.

	   Also, you must provide function prototypes for all  functions  that
	   take	 variable numbers of arguments (including "printf"); otherwise
	   incorrect code is generated for calls to those functions.

	   In addition,	 seriously  incorrect  code  results  if  you  call  a
	   function  with  too many arguments.	(Normally, extra arguments are
	   harmlessly ignored.)

	   The "rtd" instruction is supported  by  the	68010,	68020,	68030,
	   68040, 68060	and CPU32 processors, but not by the 68000 or 5200.

	   The default is -mno-rtd.

       -malign-int
       -mno-align-int
	   Control  whether  GCC  aligns  "int", "long", "long long", "float",
	   "double",  and  "long  double"  variables  on  a  32-bit   boundary
	   (-malign-int)  or  a	 16-bit	 boundary  (-mno-align-int).  Aligning
	   variables on	32-bit boundaries produces  code  that	runs  somewhat
	   faster  on  processors  with	 32-bit	 busses	at the expense of more
	   memory.

	   Warning: if you use the -malign-int switch, GCC  aligns  structures
	   containing	the   above  types  differently	 than  most  published
	   application binary interface	specifications for the m68k.

	   Use the pc-relative addressing mode of the 68000 directly,  instead
	   of  using  a	 global	offset table.  At present, this	option implies
	   -fpic, allowing at most a 16-bit offset for pc-relative addressing.
	   -fPIC is not	presently supported with -mpcrel, though this could be
	   supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
	   Do not (do) assume that unaligned memory references are handled  by
	   the system.

       -msep-data
	   Generate  code  that	 allows	 the  data  segment to be located in a
	   different area of memory from the text segment.   This  allows  for
	   execute-in-place   in   an	environment   without  virtual	memory
	   management.	This option implies -fPIC.

       -mno-sep-data
	   Generate code that assumes that the data segment follows  the  text
	   segment.  This is the default.

       -mid-shared-library
	   Generate  code  that	 supports  shared libraries via	the library ID
	   method.  This allows	for execute-in-place and shared	 libraries  in
	   an  environment  without  virtual  memory  management.  This	option
	   implies -fPIC.

       -mno-id-shared-library
	   Generate code that doesn't assume  ID-based	shared	libraries  are
	   being used.	This is	the default.

       -mshared-library-id=n
	   Specifies  the identification number	of the ID-based	shared library
	   being compiled.  Specifying a value of  0  generates	 more  compact
	   code;  specifying other values forces the allocation	of that	number
	   to the current library, but is no  more  space-  or	time-efficient
	   than	omitting this option.

       -mxgot
       -mno-xgot
	   When	 generating  position-independent  code	for ColdFire, generate
	   code	that works if the GOT has more than 8192 entries.   This  code
	   is  larger  and slower than code generated without this option.  On
	   M680x0 processors, this option is not needed; -fPIC suffices.

	   GCC normally	uses a single instruction to load values from the GOT.
	   While this is relatively efficient, it only works  if  the  GOT  is
	   smaller  than  about	 64k.	Anything  larger  causes the linker to
	   report an error such	as:

		   relocation truncated	to fit:	R_68K_GOT16O foobar

	   If this happens, you	should recompile your code  with  -mxgot.   It
	   should  then	 work  with  very large	GOTs.  However,	code generated
	   with	-mxgot is less efficient, since	it  takes  4  instructions  to
	   fetch the value of a	global symbol.

	   Note	that some linkers, including newer versions of the GNU linker,
	   can	create multiple	GOTs and sort GOT entries.  If you have	such a
	   linker, you should only need	to use -mxgot when compiling a	single
	   object file that accesses more than 8192 GOT	entries.  Very few do.

	   These  options  have	 no  effect unless GCC is generating position-
	   independent code.

       -mlong-jump-table-offsets
	   Use 32-bit offsets in "switch"  tables.   The  default  is  to  use
	   16-bit offsets.

       MCore Options

       These are the -m	options	defined	for the	Motorola M*Core	processors.

       -mhardlit
       -mno-hardlit
	   Inline  constants  into  the	 code  stream if it can	be done	in two
	   instructions	or less.

       -mdiv
       -mno-div
	   Use the divide instruction.	(Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
	   Allow arbitrary-sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
	   Always treat	bit-fields as "int"-sized.

       -m4byte-functions
       -mno-4byte-functions
	   Force all functions to be aligned to	a 4-byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
	   Emit	callgraph information.

       -mslow-bytes
       -mno-slow-bytes
	   Prefer word access when reading byte	quantities.

       -mlittle-endian
       -mbig-endian
	   Generate code for a little-endian target.

       -m210
       -m340
	   Generate code for the 210 processor.

       -mno-lsim
	   Assume that runtime support has  been  provided  and	 so  omit  the
	   simulator library (libsim.a)	from the linker	command	line.

       -mstack-increment=size
	   Set	the  maximum  amount  for  a single stack increment operation.
	   Large values	can  increase  the  speed  of  programs	 that  contain
	   functions  that  need  a  large amount of stack space, but they can
	   also	trigger	a segmentation fault if	 the  stack  is	 extended  too
	   much.  The default value is 0x1000.

       MeP Options

       -mabsdiff
	   Enables  the	 "abs"	instruction,  which is the absolute difference
	   between two registers.

       -mall-opts
	   Enables all the optional instructions---average, multiply,  divide,
	   bit	operations,  leading zero, absolute difference,	min/max, clip,
	   and saturation.

       -maverage
	   Enables the "ave" instruction, which	computes the  average  of  two
	   registers.

       -mbased=n
	   Variables  of  size	n  bytes or smaller are	placed in the ".based"
	   section by default.	Based variables	use the	$tp register as	a base
	   register, and there is a 128-byte limit to the ".based" section.

       -mbitops
	   Enables the bit operation instructions---bit	 test  ("btstm"),  set
	   ("bsetm"),  clear  ("bclrm"),  invert  ("bnotm"),  and test-and-set
	   ("tas").

       -mc=name
	   Selects which section constant data is  placed  in.	 name  may  be
	   tiny, near, or far.

       -mclip
	   Enables  the	 "clip"	 instruction.	Note that -mclip is not	useful
	   unless you also provide -mminmax.

       -mconfig=name
	   Selects one of the built-in core configurations.  Each MeP chip has
	   one or more modules in it; each module has a	core CPU and a variety
	   of  coprocessors,  optional	instructions,  and  peripherals.   The
	   "MeP-Integrator"   tool,   not   part   of	GCC,   provides	 these
	   configurations through this option; using this option is  the  same
	   as  using  all the corresponding command-line options.  The default
	   configuration is default.

       -mcop
	   Enables the coprocessor instructions.  By default, this is a	32-bit
	   coprocessor.	 Note that the coprocessor is normally enabled via the
	   -mconfig= option.

       -mcop32
	   Enables the 32-bit coprocessor's instructions.

       -mcop64
	   Enables the 64-bit coprocessor's instructions.

       -mivc2
	   Enables IVC2	scheduling.  IVC2 is a 64-bit VLIW coprocessor.

       -mdc
	   Causes constant variables to	be placed in the ".near" section.

       -mdiv
	   Enables the "div" and "divu"	instructions.

       -meb
	   Generate big-endian code.

       -mel
	   Generate little-endian code.

       -mio-volatile
	   Tells the compiler that any variable	marked with the	"io" attribute
	   is to be considered volatile.

       -ml Causes variables to be assigned to the ".far" section by default.

       -mleadz
	   Enables the "leadz" (leading	zero) instruction.

       -mm Causes variables to be assigned to the ".near" section by default.

       -mminmax
	   Enables the "min" and "max" instructions.

       -mmult
	   Enables the multiplication and multiply-accumulate instructions.

       -mno-opts
	   Disables all	the optional instructions enabled by -mall-opts.

       -mrepeat
	   Enables the "repeat"	and  "erepeat"	instructions,  used  for  low-
	   overhead looping.

       -ms Causes  all variables to default to the ".tiny" section.  Note that
	   there is a 65536-byte limit to this	section.   Accesses  to	 these
	   variables use the %gp base register.

       -msatur
	   Enables  the	 saturation instructions.  Note	that the compiler does
	   not currently generate these	itself,	but this  option  is  included
	   for compatibility with other	tools, like "as".

       -msdram
	   Link	 the  SDRAM-based  runtime  instead  of	 the default ROM-based
	   runtime.

       -msim
	   Link	the simulator run-time libraries.

       -msimnovec
	   Link	the simulator runtime libraries,  excluding  built-in  support
	   for reset and exception vectors and tables.

       -mtf
	   Causes  all	functions  to  default to the ".far" section.  Without
	   this	option,	functions default to the ".near" section.

       -mtiny=n
	   Variables that are n	bytes or smaller are allocated to the  ".tiny"
	   section.   These  variables use the $gp base	register.  The default
	   for this option is 4, but note that there's a 65536-byte  limit  to
	   the ".tiny" section.

       MicroBlaze Options

       -msoft-float
	   Use software	emulation for floating point (default).

       -mhard-float
	   Use hardware	floating-point instructions.

       -mmemcpy
	   Do not optimize block moves,	use "memcpy".

       -mno-clearbss
	   This	  option   is  deprecated.   Use  -fno-zero-initialized-in-bss
	   instead.

       -mcpu=cpu-type
	   Use features	of, and	schedule code for, the given  CPU.   Supported
	   values are in the format vX.YY.Z, where X is	a major	version, YY is
	   the minor version, and Z is compatibility code.  Example values are
	   v3.00.a, v4.00.b, v5.00.a, v5.00.b, v6.00.a.

       -mxl-soft-mul
	   Use software	multiply emulation (default).

       -mxl-soft-div
	   Use software	emulation for divides (default).

       -mxl-barrel-shift
	   Use the hardware barrel shifter.

       -mxl-pattern-compare
	   Use pattern compare instructions.

       -msmall-divides
	   Use table lookup optimization for small signed integer divisions.

       -mxl-stack-check
	   This	option is deprecated.  Use -fstack-check instead.

       -mxl-gp-opt
	   Use GP-relative ".sdata"/".sbss" sections.

       -mxl-multiply-high
	   Use multiply	high instructions for high part	of 32x32 multiply.

       -mxl-float-convert
	   Use hardware	floating-point conversion instructions.

       -mxl-float-sqrt
	   Use hardware	floating-point square root instruction.

       -mbig-endian
	   Generate code for a big-endian target.

       -mlittle-endian
	   Generate code for a little-endian target.

       -mxl-reorder
	   Use reorder instructions (swap and byte reversed load/store).

       -mxl-mode-app-model
	   Select application model app-model.	Valid models are

	   executable
	       normal executable (default), uses startup code crt0.o.

	   -mpic-data-is-text-relative
	       Assume that the displacement between the	text and data segments
	       is  fixed  at  static  link  time.   This  allows  data	to  be
	       referenced by offset from start of text address instead of  GOT
	       since PC-relative addressing is not supported.

	   xmdstub
	       for   use  with	Xilinx	Microprocessor	Debugger  (XMD)	 based
	       software	 intrusive  debug  agent  called  xmdstub.  This  uses
	       startup	file  crt1.o and sets the start	address	of the program
	       to 0x800.

	   bootstrap
	       for applications	that are  loaded  using	 a  bootloader.	  This
	       model  uses  startup  file  crt2.o  which  does	not  contain a
	       processor  reset	 vector	 handler.   This   is	suitable   for
	       transferring  control  on  a  processor reset to	the bootloader
	       rather than the application.

	   novectors
	       for applications	that do	not  require  any  of  the  MicroBlaze
	       vectors.	 This  option  may  be useful for applications running
	       within a	monitoring application.	This model uses	 crt3.o	 as  a
	       startup file.

	   Option  -xl-mode-app-model is a deprecated alias for	-mxl-mode-app-
	   model.

       MIPS Options

       -EB Generate big-endian code.

       -EL Generate little-endian code.	 This is the default  for  mips*el-*-*
	   configurations.

       -march=arch
	   Generate code that runs on arch, which can be the name of a generic
	   MIPS	 ISA,  or  the	name of	a particular processor.	 The ISA names
	   are:	 mips1,	 mips2,	 mips3,	 mips4,	 mips32,  mips32r2,  mips32r3,
	   mips32r5,   mips32r6,  mips64,  mips64r2,  mips64r3,	 mips64r5  and
	   mips64r6.  The processor names are:	4kc,  4km,  4kp,  4ksc,	 4kec,
	   4kem,  4kep,	 4ksd,	5kc, 5kf, 20kc,	24kc, 24kf2_1, 24kf1_1,	24kec,
	   24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1,	34kn,  74kc,  74kf2_1,
	   74kf1_1,  74kf3_2,  1004kc,	1004kf2_1,  1004kf1_1,	i6400,	i6500,
	   interaptiv,	loongson2e,  loongson2f,  loongson3a,  gs464,  gs464e,
	   gs264e,  m4k,  m14k,	 m14kc,	 m14ke,	 m14kec, m5100,	m5101, octeon,
	   octeon+, octeon2,  octeon3,	orion,	p5600,	p6600,	r2000,	r3000,
	   r3900,  r4000,  r4400,  r4600,  r4650,  r4700, r5900, r6000,	r8000,
	   rm7000, rm9000,  r10000,  r12000,  r14000,  r16000,	sb1,  sr71000,
	   vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400, vr5500, xlr
	   and	xlp.   The  special value from-abi selects the most compatible
	   architecture	for the	selected ABI (that is, mips1 for  32-bit  ABIs
	   and mips3 for 64-bit	ABIs).

	   The	native	Linux/GNU  toolchain  also  supports the value native,
	   which selects the best architecture option for the host  processor.
	   -march=native   has	no  effect  if	GCC  does  not	recognize  the
	   processor.

	   In processor	names, a final	000  can  be  abbreviated  as  k  (for
	   example, -march=r2k).  Prefixes are optional, and vr	may be written
	   r.

	   Names  of  the  form	nf2_1 refer to processors with FPUs clocked at
	   half	the rate of the	 core,	names  of  the	form  nf1_1  refer  to
	   processors  with  FPUs  clocked  at	the same rate as the core, and
	   names of the	form nf3_2 refer to processors	with  FPUs  clocked  a
	   ratio  of 3:2 with respect to the core.  For	compatibility reasons,
	   nf is accepted as a synonym for nf2_1 while nx and bfx are accepted
	   as synonyms for nf1_1.

	   GCC defines two macros based	on the	value  of  this	 option.   The
	   first is "_MIPS_ARCH", which	gives the name of target architecture,
	   as  a  string.  The second has the form "_MIPS_ARCH_foo", where foo
	   is  the  capitalized	  value	  of   "_MIPS_ARCH".	For   example,
	   -march=r2000	 sets  "_MIPS_ARCH"  to	 "r2000" and defines the macro
	   "_MIPS_ARCH_R2000".

	   Note	that the "_MIPS_ARCH" macro uses  the  processor  names	 given
	   above.   In	other  words,  it  has	the  full  prefix and does not
	   abbreviate 000 as k.	 In the	case of	from-abi, the macro names  the
	   resolved  architecture  (either  "mips1" or "mips3").  It names the
	   default architecture	when no	-march option is given.

       -mtune=arch
	   Optimize for	arch.  Among other things, this	 option	 controls  the
	   way	 instructions	are  scheduled,	 and  the  perceived  cost  of
	   arithmetic operations.  The list of arch values is the same as  for
	   -march.

	   When	 this  option  is  not	used,  GCC optimizes for the processor
	   specified by	-march.	 By using -march and -mtune  together,	it  is
	   possible  to	generate code that runs	on a family of processors, but
	   optimize the	code for one particular	member of that family.

	   -mtune defines the macros "_MIPS_TUNE" and "_MIPS_TUNE_foo",	 which
	   work	in the same way	as the -march ones described above.

       -mips1
	   Equivalent to -march=mips1.

       -mips2
	   Equivalent to -march=mips2.

       -mips3
	   Equivalent to -march=mips3.

       -mips4
	   Equivalent to -march=mips4.

       -mips32
	   Equivalent to -march=mips32.

       -mips32r3
	   Equivalent to -march=mips32r3.

       -mips32r5
	   Equivalent to -march=mips32r5.

       -mips32r6
	   Equivalent to -march=mips32r6.

       -mips64
	   Equivalent to -march=mips64.

       -mips64r2
	   Equivalent to -march=mips64r2.

       -mips64r3
	   Equivalent to -march=mips64r3.

       -mips64r5
	   Equivalent to -march=mips64r5.

       -mips64r6
	   Equivalent to -march=mips64r6.

       -mips16
       -mno-mips16
	   Generate  (do  not  generate)  MIPS16  code.	 If GCC	is targeting a
	   MIPS32 or MIPS64 architecture, it makes use of the MIPS16e ASE.

	   MIPS16 code generation can also be  controlled  on  a  per-function
	   basis by means of "mips16" and "nomips16" attributes.

       -mflip-mips16
	   Generate  MIPS16  code  on  alternating  functions.	This option is
	   provided for	regression testing  of	mixed  MIPS16/non-MIPS16  code
	   generation,	and is not intended for	ordinary use in	compiling user
	   code.

       -minterlink-compressed
       -mno-interlink-compressed
	   Require  (do	 not   require)	  that	 code	using	the   standard
	   (uncompressed)   MIPS   ISA	be  link-compatible  with  MIPS16  and
	   microMIPS code, and vice versa.

	   For example,	code using  the	 standard  ISA	encoding  cannot  jump
	   directly  to	MIPS16 or microMIPS code; it must either use a call or
	   an indirect jump.  -minterlink-compressed therefore disables	direct
	   jumps unless	 GCC  knows  that  the	target	of  the	 jump  is  not
	   compressed.

       -minterlink-mips16
       -mno-interlink-mips16
	   Aliases  of	-minterlink-compressed	and -mno-interlink-compressed.
	   These options predate  the  microMIPS  ASE  and  are	 retained  for
	   backwards compatibility.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
	   Generate code for the given ABI.

	   Note	that the EABI has a 32-bit and a 64-bit	variant.  GCC normally
	   generates  64-bit  code  when you select a 64-bit architecture, but
	   you can use -mgp32 to get 32-bit code instead.

	   For	   information	    about      the	O64	 ABI,	   see
	   <http://gcc.gnu.org/projects/mipso64-abi.html>.

	   GCC	supports  a  variant  of  the  o32 ABI in which	floating-point
	   registers are 64 rather than	32 bits	wide.	You  can  select  this
	   combination	with  -mabi=32 -mfp64.	This ABI relies	on the "mthc1"
	   and "mfhc1"	instructions  and  is  therefore  only	supported  for
	   MIPS32R2, MIPS32R3 and MIPS32R5 processors.

	   The register	assignments for	arguments and return values remain the
	   same,  but  each scalar value is passed in a	single 64-bit register
	   rather than a  pair	of  32-bit  registers.	 For  example,	scalar
	   floating-point values are returned in $f0 only, not a $f0/$f1 pair.
	   The	set  of	call-saved registers also remains the same in that the
	   even-numbered double-precision registers are	saved.

	   Two additional variants of the o32 ABI are supported	 to  enable  a
	   transition  from  32-bit  to	 64-bit	 registers.   These  are  FPXX
	   (-mfpxx) and	FP64A (-mfp64  -mno-odd-spreg).	  The  FPXX  extension
	   mandates that all code must execute correctly when run using	32-bit
	   or  64-bit registers.  The code can be interlinked with either FP32
	   or FP64, but	not both.  The FP64A extension is similar to the  FP64
	   extension  but  forbids  the	 use  of odd-numbered single-precision
	   registers.  This can	be used	in conjunction with the	"FRE" mode  of
	   FPUs	 in MIPS32R5 processors	and allows both	FP32 and FP64A code to
	   interlink and run in	the same process without changing FPU modes.

       -mabicalls
       -mno-abicalls
	   Generate (do	not generate) code that	 is  suitable  for  SVR4-style
	   dynamic objects.  -mabicalls	is the default for SVR4-based systems.

       -mshared
       -mno-shared
	   Generate (do	not generate) code that	is fully position-independent,
	   and	that  can  therefore  be  linked  into shared libraries.  This
	   option only affects -mabicalls.

	   All -mabicalls code has  traditionally  been	 position-independent,
	   regardless  of  options  like  -fPIC	 and  -fpic.   However,	 as an
	   extension, the GNU toolchain	allows	executables  to	 use  absolute
	   accesses  for  locally-binding symbols.  It can also	use shorter GP
	   initialization sequences and	 generate  direct  calls  to  locally-
	   defined functions.  This mode is selected by	-mno-shared.

	   -mno-shared	depends	 on  binutils  2.16  or	 higher	 and generates
	   objects that	can only be linked by the GNU  linker.	 However,  the
	   option  does	 not  affect  the ABI of the final executable; it only
	   affects  the	 ABI  of  relocatable  objects.	   Using   -mno-shared
	   generally makes executables both smaller and	quicker.

	   -mshared is the default.

       -mplt
       -mno-plt
	   Assume  (do not assume) that	the static and dynamic linkers support
	   PLTs	and copy relocations.  This option  only  affects  -mno-shared
	   -mabicalls.	 For  the  n64	ABI, this option has no	effect without
	   -msym32.

	   You	can  make  -mplt  the  default	 by   configuring   GCC	  with
	   --with-mips-plt.  The default is -mno-plt otherwise.

       -mxgot
       -mno-xgot
	   Lift	(do not	lift) the usual	restrictions on	the size of the	global
	   offset table.

	   GCC normally	uses a single instruction to load values from the GOT.
	   While  this	is  relatively	efficient, it only works if the	GOT is
	   smaller than	about 64k.   Anything  larger  causes  the  linker  to
	   report an error such	as:

		   relocation truncated	to fit:	R_MIPS_GOT16 foobar

	   If  this happens, you should	recompile your code with -mxgot.  This
	   works with  very  large  GOTs,  although  the  code	is  also  less
	   efficient,  since it	takes three instructions to fetch the value of
	   a global symbol.

	   Note	that some linkers can create multiple GOTs.  If	you have  such
	   a  linker,  you should only need to use -mxgot when a single	object
	   file	accesses more than 64k's worth of GOT entries.	Very few do.

	   These options have no effect	 unless	 GCC  is  generating  position
	   independent code.

       -mgp32
	   Assume that general-purpose registers are 32	bits wide.

       -mgp64
	   Assume that general-purpose registers are 64	bits wide.

       -mfp32
	   Assume that floating-point registers	are 32 bits wide.

       -mfp64
	   Assume that floating-point registers	are 64 bits wide.

       -mfpxx
	   Do not assume the width of floating-point registers.

       -mhard-float
	   Use floating-point coprocessor instructions.

       -msoft-float
	   Do  not  use	 floating-point	 coprocessor  instructions.  Implement
	   floating-point calculations using library calls instead.

       -mno-float
	   Equivalent to  -msoft-float,	 but  additionally  asserts  that  the
	   program   being   compiled  does  not  perform  any	floating-point
	   operations.	This option is presently supported only	by some	 bare-
	   metal  MIPS	configurations,	 where	it may select a	special	set of
	   libraries that lack	all  floating-point  support  (including,  for
	   example,  the  floating-point  "printf" formats).  If code compiled
	   with	-mno-float accidentally	contains floating-point	operations, it
	   is likely to	suffer a link-time or run-time failure.

       -msingle-float
	   Assume that the floating-point coprocessor  only  supports  single-
	   precision operations.

       -mdouble-float
	   Assume   that   the	floating-point	coprocessor  supports  double-
	   precision operations.  This is the default.

       -modd-spreg
       -mno-odd-spreg
	   Enable the  use  of	odd-numbered  single-precision	floating-point
	   registers for the o32 ABI.  This is the default for processors that
	   are known to	support	these registers.  When using the o32 FPXX ABI,
	   -mno-odd-spreg is set by default.

       -mabs=2008
       -mabs=legacy
	   These  options  control  the	 treatment of the special not-a-number
	   (NaN) IEEE 754 floating-point data with the "abs.fmt" and "neg.fmt"
	   machine instructions.

	   By default or when -mabs=legacy is used  the	 legacy	 treatment  is
	   selected.	In   this   case  these	 instructions  are  considered
	   arithmetic and avoided where	correct	operation is required and  the
	   input  operand  might  be a NaN.  A longer sequence of instructions
	   that	manipulate the sign bit	of floating-point  datum  manually  is
	   used	 instead  unless  the  -ffinite-math-only option has also been
	   specified.

	   The -mabs=2008 option selects the IEEE 754-2008 treatment.  In this
	   case	these instructions are considered non-arithmetic and therefore
	   operating correctly in all cases, including in particular where the
	   input operand is a NaN.  These instructions	are  therefore	always
	   used	for the	respective operations.

       -mnan=2008
       -mnan=legacy
	   These  options  control  the	 encoding  of the special not-a-number
	   (NaN) IEEE 754 floating-point data.

	   The -mnan=legacy option selects the legacy encoding.	 In this  case
	   quiet  NaNs	(qNaNs)	are denoted by the first bit of	their trailing
	   significand field being  0,	whereas	 signaling  NaNs  (sNaNs)  are
	   denoted  by the first bit of	their trailing significand field being
	   1.

	   The -mnan=2008 option selects the IEEE 754-2008 encoding.  In  this
	   case	 qNaNs	are  denoted  by  the  first  bit  of  their  trailing
	   significand field being 1, whereas sNaNs are	denoted	by  the	 first
	   bit of their	trailing significand field being 0.

	   The	default	 is  -mnan=legacy  unless GCC has been configured with
	   --with-nan=2008.

       -mllsc
       -mno-llsc
	   Use (do not use) ll,	sc, and	sync instructions to implement	atomic
	   memory  built-in  functions.	 When neither option is	specified, GCC
	   uses	the instructions if the	target architecture supports them.

	   -mllsc is  useful  if  the  runtime	environment  can  emulate  the
	   instructions	 and  -mno-llsc	 can  be  useful  when	compiling  for
	   nonstandard ISAs.  You  can	make  either  option  the  default  by
	   configuring	GCC  with --with-llsc and --without-llsc respectively.
	   --with-llsc	is  the	 default  for  some  configurations;  see  the
	   installation	documentation for details.

       -mdsp
       -mno-dsp
	   Use (do not use) revision 1 of the MIPS DSP ASE.
	     This option defines the preprocessor macro	"__mips_dsp".  It also
	   defines "__mips_dsp_rev" to 1.

       -mdspr2
       -mno-dspr2
	   Use (do not use) revision 2 of the MIPS DSP ASE.
	     This  option  defines  the	 preprocessor  macros "__mips_dsp" and
	   "__mips_dspr2".  It also defines "__mips_dsp_rev" to	2.

       -msmartmips
       -mno-smartmips
	   Use (do not use) the	MIPS SmartMIPS ASE.

       -mpaired-single
       -mno-paired-single
	   Use (do not use) paired-single floating-point instructions.
	     This  option  requires  hardware  floating-point  support	to  be
	   enabled.

       -mdmx
       -mno-mdmx
	   Use	(do  not use) MIPS Digital Media Extension instructions.  This
	   option can only be used when	generating 64-bit  code	 and  requires
	   hardware floating-point support to be enabled.

       -mips3d
       -mno-mips3d
	   Use	(do  not  use)	the  MIPS-3D  ASE.  The	option -mips3d implies
	   -mpaired-single.

       -mmicromips
       -mno-micromips
	   Generate (do	not generate) microMIPS	code.

	   MicroMIPS code generation can also be controlled on a  per-function
	   basis by means of "micromips" and "nomicromips" attributes.

       -mmt
       -mno-mt
	   Use (do not use) MT Multithreading instructions.

       -mmcu
       -mno-mcu
	   Use (do not use) the	MIPS MCU ASE instructions.

       -meva
       -mno-eva
	   Use (do not use) the	MIPS Enhanced Virtual Addressing instructions.

       -mvirt
       -mno-virt
	   Use (do not use) the	MIPS Virtualization (VZ) instructions.

       -mxpa
       -mno-xpa
	   Use	 (do  not  use)	 the  MIPS  eXtended  Physical	Address	 (XPA)
	   instructions.

       -mcrc
       -mno-crc
	   Use	(do  not  use)	the  MIPS  Cyclic   Redundancy	 Check	 (CRC)
	   instructions.

       -mginv
       -mno-ginv
	   Use (do not use) the	MIPS Global INValidate (GINV) instructions.

       -mloongson-mmi
       -mno-loongson-mmi
	   Use	 (do   not   use)  the	MIPS  Loongson	MultiMedia  extensions
	   Instructions	(MMI).

       -mloongson-ext
       -mno-loongson-ext
	   Use (do not use) the	MIPS Loongson EXTensions (EXT) instructions.

       -mloongson-ext2
       -mno-loongson-ext2
	   Use	(do  not  use)	the  MIPS  Loongson   EXTensions   r2	(EXT2)
	   instructions.

       -mlong64
	   Force  "long"  types	 to  be	 64  bits  wide.   See -mlong32	for an
	   explanation of the default and the way that	the  pointer  size  is
	   determined.

       -mlong32
	   Force "long", "int",	and pointer types to be	32 bits	wide.

	   The	default	 size  of  "int"s, "long"s and pointers	depends	on the
	   ABI.	 All the supported ABIs	use 32-bit "int"s.  The	n64  ABI  uses
	   64-bit  "long"s,  as	 does  the  64-bit EABI; the others use	32-bit
	   "long"s.  Pointers are the same size	as "long"s, or the  same  size
	   as integer registers, whichever is smaller.

       -msym32
       -mno-sym32
	   Assume  (do	not  assume)  that  all	 symbols  have	32-bit values,
	   regardless  of  the	selected  ABI.	 This  option  is  useful   in
	   combination	with  -mabi=64 and -mno-abicalls because it allows GCC
	   to generate shorter and faster references to	symbolic addresses.

       -G num
	   Put definitions of externally-visible data in a small data  section
	   if  that  data  is no bigger	than num bytes.	 GCC can then generate
	   more	efficient accesses to the data;	see -mgpopt for	details.

	   The default -G option depends on the	configuration.

       -mlocal-sdata
       -mno-local-sdata
	   Extend (do not extend) the -G behavior to local data	too,  such  as
	   to  static  variables  in  C.  -mlocal-sdata	is the default for all
	   configurations.

	   If the linker complains that	an application is using	too much small
	   data, you might  want  to  try  rebuilding  the  less  performance-
	   critical parts with -mno-local-sdata.  You might also want to build
	   large  libraries with -mno-local-sdata, so that the libraries leave
	   more	room for the main program.

       -mextern-sdata
       -mno-extern-sdata
	   Assume (do not assume) that externally-defined data is in  a	 small
	   data	 section  if  the  size	 of  that data is within the -G	limit.
	   -mextern-sdata is the default for all configurations.

	   If you compile a module Mod with -mextern-sdata -G num -mgpopt, and
	   Mod references a variable Var that is no bigger than	num bytes, you
	   must	make sure that Var is placed in	a small	data section.  If  Var
	   is  defined	by another module, you must either compile that	module
	   with	a high-enough -G setting or attach a  "section"	 attribute  to
	   Var's  definition.  If Var is common, you must link the application
	   with	a high-enough -G setting.

	   The easiest way of satisfying these restrictions is to compile  and
	   link	 every	module with the	same -G	option.	 However, you may wish
	   to build a library  that  supports  several	different  small  data
	   limits.   You can do	this by	compiling the library with the highest
	   supported -G	setting	and additionally  using	 -mno-extern-sdata  to
	   stop	 the  library from making assumptions about externally-defined
	   data.

       -mgpopt
       -mno-gpopt
	   Use (do not use) GP-relative	accesses for symbols that are known to
	   be  in  a  small  data   section;   see   -G,   -mlocal-sdata   and
	   -mextern-sdata.  -mgpopt is the default for all configurations.

	   -mno-gpopt  is  useful  for	cases where the	$gp register might not
	   hold	the value of "_gp".  For example, if the code  is  part	 of  a
	   library  that  might	 be used in a boot monitor, programs that call
	   boot	monitor	routines pass an  unknown  value  in  $gp.   (In  such
	   situations, the boot	monitor	itself is usually compiled with	-G0.)

	   -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

       -membedded-data
       -mno-embedded-data
	   Allocate variables to the read-only data section first if possible,
	   then	next in	the small data section if possible, otherwise in data.
	   This	 gives	slightly slower	code than the default, but reduces the
	   amount of RAM required when executing, and thus  may	 be  preferred
	   for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
	   Put	uninitialized "const" variables	in the read-only data section.
	   This	option is only meaningful in conjunction with -membedded-data.

       -mcode-readable=setting
	   Specify whether GCC may generate code that  reads  from  executable
	   sections.  There are	three possible settings:

	   -mcode-readable=yes
	       Instructions  may  freely  access executable sections.  This is
	       the default setting.

	   -mcode-readable=pcrel
	       MIPS16 PC-relative  load	 instructions  can  access  executable
	       sections,  but  other instructions must not do so.  This	option
	       is useful on 4KSc and 4KSd processors when the code  TLBs  have
	       the Read	Inhibit	bit set.  It is	also useful on processors that
	       can   be	 configured  to	 have  a  dual	instruction/data  SRAM
	       interface and that, like	the M4K,  automatically	 redirect  PC-
	       relative	loads to the instruction RAM.

	   -mcode-readable=no
	       Instructions  must not access executable	sections.  This	option
	       can be useful on	targets	that are configured  to	 have  a  dual
	       instruction/data	 SRAM  interface  but that (unlike the M4K) do
	       not automatically redirect PC-relative loads to the instruction
	       RAM.

       -msplit-addresses
       -mno-split-addresses
	   Enable  (disable)  use  of  the  "%hi()"  and   "%lo()"   assembler
	   relocation	operators.    This   option  has  been	superseded  by
	   -mexplicit-relocs but is retained for backwards compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
	   Use (do not use) assembler relocation operators when	 dealing  with
	   symbolic	addresses.	The	alternative,	selected    by
	   -mno-explicit-relocs, is to use assembler macros instead.

	   -mexplicit-relocs is	the default if GCC was configured  to  use  an
	   assembler that supports relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
	   Trap	(do not	trap) on integer division by zero.

	   The default is -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
	   MIPS	 systems  check	 for  division	by zero	by generating either a
	   conditional trap or a break instruction.  Using  traps  results  in
	   smaller  code,  but	is only	supported on MIPS II and later.	 Also,
	   some	versions of the	Linux kernel have a  bug  that	prevents  trap
	   from	 generating  the proper	signal ("SIGFPE").  Use	-mdivide-traps
	   to allow conditional	traps on architectures that support  them  and
	   -mdivide-breaks to force the	use of breaks.

	   The	default	 is usually -mdivide-traps, but	this can be overridden
	   at  configure  time	using  --with-divide=breaks.	Divide-by-zero
	   checks can be completely disabled using -mno-check-zero-division.

       -mload-store-pairs
       -mno-load-store-pairs
	   Enable  (disable)  an  optimization	that pairs consecutive load or
	   store instructions to enable	load/store bonding.   This  option  is
	   enabled  by	default	 but  only  takes  effect  when	 the  selected
	   architecture	is known to support bonding.

       -mmemcpy
       -mno-memcpy
	   Force (do not force)	the use	 of  "memcpy"  for  non-trivial	 block
	   moves.  The default is -mno-memcpy, which allows GCC	to inline most
	   constant-sized copies.

       -mlong-calls
       -mno-long-calls
	   Disable  (do	 not  disable)	use of the "jal" instruction.  Calling
	   functions using "jal" is more efficient but requires	the caller and
	   callee to be	in the same 256	megabyte segment.

	   This	option has  no	effect	on  abicalls  code.   The  default  is
	   -mno-long-calls.

       -mmad
       -mno-mad
	   Enable  (disable)  use of the "mad",	"madu" and "mul" instructions,
	   as provided by the R4650 ISA.

       -mimadd
       -mno-imadd
	   Enable (disable) use	of the "madd" and "msub" integer instructions.
	   The default is -mimadd on architectures  that  support  "madd"  and
	   "msub"  except  for	the  74k  architecture	where  it was found to
	   generate slower code.

       -mfused-madd
       -mno-fused-madd
	   Enable (disable)  use  of  the  floating-point  multiply-accumulate
	   instructions,   when	  they	 are   available.    The   default  is
	   -mfused-madd.

	   On the R8000	CPU when multiply-accumulate  instructions  are	 used,
	   the intermediate product is calculated to infinite precision	and is
	   not subject to the FCSR Flush to Zero bit.  This may	be undesirable
	   in	some   circumstances.	On  other  processors  the  result  is
	   numerically identical to the	equivalent computation using  separate
	   multiply, add, subtract and negate instructions.

       -nocpp
	   Tell	 the  MIPS  assembler  to  not	run its	preprocessor over user
	   assembler files (with a .s suffix) when assembling them.

       -mfix-24k
       -mno-fix-24k
	   Work	around the 24K E48 (lost data on stores	during refill) errata.
	   The workarounds are implemented by the  assembler  rather  than  by
	   GCC.

       -mfix-r4000
       -mno-fix-r4000
	   Work	around certain R4000 CPU errata:

	   -   A  double-word or a variable shift may give an incorrect	result
	       if executed immediately after starting an integer division.

	   -   A double-word or	a variable shift may give an incorrect	result
	       if executed while an integer multiplication is in progress.

	   -   An  integer division may	give an	incorrect result if started in
	       a delay slot of a taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
	   Work	around certain R4400 CPU errata:

	   -   A double-word or	a variable shift may give an incorrect	result
	       if executed immediately after starting an integer division.

       -mfix-r10000
       -mno-fix-r10000
	   Work	around certain R10000 errata:

	   -   "ll"/"sc"  sequences  may  not  behave  atomically on revisions
	       prior to	3.0.  They may deadlock	on revisions 2.6 and earlier.

	   This	option can only	be used	if the	target	architecture  supports
	   branch-likely  instructions.	  -mfix-r10000	is  the	 default  when
	   -march=r10000 is used; -mno-fix-r10000 is the default otherwise.

       -mfix-r5900
       -mno-fix-r5900
	   Do not attempt to schedule the preceding instruction	into the delay
	   slot	of a branch instruction	placed at the end of a short  loop  of
	   six	instructions  or fewer and always schedule a "nop" instruction
	   there instead.  The short loop bug under certain conditions	causes
	   loops  to  execute only once	or twice, due to a hardware bug	in the
	   R5900 chip.	The workaround is implemented by the assembler	rather
	   than	by GCC.

       -mfix-rm7000
       -mno-fix-rm7000
	   Work	 around	 the  RM7000 "dmult"/"dmultu" errata.  The workarounds
	   are implemented by the assembler rather than	by GCC.

       -mfix-vr4120
       -mno-fix-vr4120
	   Work	around certain VR4120 errata:

	   -   "dmultu"	does not always	produce	the correct result.

	   -   "div" and "ddiv"	do not always produce the  correct  result  if
	       one of the operands is negative.

	   The	workarounds  for the division errata rely on special functions
	   in libgcc.a.	 At present, these functions are only provided by  the
	   "mips64vr*-elf" configurations.

	   Other  VR4120  errata  require a NOP	to be inserted between certain
	   pairs of instructions.  These errata	are handled by the  assembler,
	   not by GCC itself.

       -mfix-vr4130
	   Work	 around	 the VR4130 "mflo"/"mfhi" errata.  The workarounds are
	   implemented by the assembler	 rather	 than  by  GCC,	 although  GCC
	   avoids  using  "mflo"  and  "mfhi"  if the VR4130 "macc", "macchi",
	   "dmacc" and "dmacchi" instructions are available instead.

       -mfix-sb1
       -mno-fix-sb1
	   Work	around certain SB-1 CPU	core  errata.	(This  flag  currently
	   works  around  the  SB-1  revision  2  "F1" and "F2"	floating-point
	   errata.)

       -mr10k-cache-barrier=setting
	   Specify whether GCC should insert cache barriers to avoid the  side
	   effects of speculation on R10K processors.

	   In  common  with  many  processors,	the  R10K tries	to predict the
	   outcome  of	a  conditional	branch	and   speculatively   executes
	   instructions	 from  the  "taken"  branch.   It  later  aborts these
	   instructions	if the predicted outcome is wrong.   However,  on  the
	   R10K, even aborted instructions can have side effects.

	   This	 problem  only	affects	 kernel	 stores	 and, depending	on the
	   system, kernel loads.   As  an  example,  a	speculatively-executed
	   store may load the target memory into cache and mark	the cache line
	   as  dirty,  even  if	 the  store itself is later aborted.  If a DMA
	   operation writes to the same	area of	memory before the "dirty" line
	   is flushed, the cached data overwrites the DMA-ed  data.   See  the
	   R10K	 processor  manual  for	 a  full  description, including other
	   potential problems.

	   One workaround is to	insert cache barrier instructions before every
	   memory access that might be speculatively executed and  that	 might
	   have	 side  effects	even if	aborted.  -mr10k-cache-barrier=setting
	   controls GCC's implementation of this workaround.  It assumes  that
	   aborted accesses to any byte	in the following regions does not have
	   side	effects:

	   1.  the memory occupied by the current function's stack frame;

	   2.  the memory occupied by an incoming stack	argument;

	   3.  the  memory  occupied  by  an  object with a link-time-constant
	       address.

	   It is  the  kernel's	 responsibility	 to  ensure  that  speculative
	   accesses to these regions are indeed	safe.

	   If the input	program	contains a function declaration	such as:

		   void	foo (void);

	   then	 the  implementation of	"foo" must allow "j foo" and "jal foo"
	   to be executed speculatively.   GCC	honors	this  restriction  for
	   functions  it  compiles itself.  It expects non-GCC functions (such
	   as hand-written assembly code) to do	the same.

	   The option has three	forms:

	   -mr10k-cache-barrier=load-store
	       Insert a	cache barrier before a load or	store  that  might  be
	       speculatively executed and that might have side effects even if
	       aborted.

	   -mr10k-cache-barrier=store
	       Insert	a   cache   barrier  before  a	store  that  might  be
	       speculatively executed and that might have side effects even if
	       aborted.

	   -mr10k-cache-barrier=none
	       Disable the insertion of	cache barriers.	 This is  the  default
	       setting.

       -mflush-func=func
       -mno-flush-func
	   Specifies  the  function to call to flush the I and D caches, or to
	   not call any	such function.	If called, the function	must take  the
	   same	arguments as the common	"_flush_func", that is,	the address of
	   the	memory range for which the cache is being flushed, the size of
	   the memory range, and the number 3 (to  flush  both	caches).   The
	   default  depends on the target GCC was configured for, but commonly
	   is either "_flush_func" or "__cpu_flush".

       mbranch-cost=num
	   Set the cost	of branches  to	 roughly  num  "simple"	 instructions.
	   This	 cost  is  only	 a  heuristic and is not guaranteed to produce
	   consistent  results	across	releases.   A  zero  cost  redundantly
	   selects the default,	which is based on the -mtune setting.

       -mbranch-likely
       -mno-branch-likely
	   Enable  or disable use of Branch Likely instructions, regardless of
	   the default for the	selected  architecture.	  By  default,	Branch
	   Likely  instructions	 may be	generated if they are supported	by the
	   selected architecture.  An exception	is for the MIPS32  and	MIPS64
	   architectures  and  processors  that	implement those	architectures;
	   for those, Branch Likely  instructions  are	not  be	 generated  by
	   default  because  the  MIPS32 and MIPS64 architectures specifically
	   deprecate their use.

       -mcompact-branches=never
       -mcompact-branches=optimal
       -mcompact-branches=always
	   These options control which form of	branches  will	be  generated.
	   The default is -mcompact-branches=optimal.

	   The	-mcompact-branches=never  option  ensures  that	compact	branch
	   instructions	will never be generated.

	   The -mcompact-branches=always option	ensures	that a compact	branch
	   instruction	will  be  generated if available.  If a	compact	branch
	   instruction is not available, a delay slot form of the branch  will
	   be used instead.

	   This	option is supported from MIPS Release 6	onwards.

	   The	-mcompact-branches=optimal  option  will  cause	 a  delay slot
	   branch to be	used if	one is available in the	current	 ISA  and  the
	   delay  slot	is  successfully  filled.   If	the  delay slot	is not
	   filled, a compact branch will be chosen if one is available.

       -mfp-exceptions
       -mno-fp-exceptions
	   Specifies whether FP	exceptions are enabled.	 This affects  how  FP
	   instructions	 are  scheduled	 for  some processors.	The default is
	   that	FP exceptions are enabled.

	   For instance, on the	SB-1, if FP exceptions are  disabled,  and  we
	   are	 emitting  64-bit  code,  then	we  can	 use  both  FP	pipes.
	   Otherwise, we can only use one FP pipe.

       -mvr4130-align
       -mno-vr4130-align
	   The VR4130 pipeline is two-way superscalar, but can only issue  two
	   instructions	 together  if  the  first one is 8-byte	aligned.  When
	   this	option is enabled, GCC aligns pairs of	instructions  that  it
	   thinks should execute in parallel.

	   This	 option	only has an effect when	optimizing for the VR4130.  It
	   normally makes code faster, but at the expense of making it bigger.
	   It is enabled by default at optimization level -O3.

       -msynci
       -mno-synci
	   Enable   (disable)	generation   of	  "synci"   instructions    on
	   architectures  that	support	 it.   The  "synci"  instructions  (if
	   enabled) are	generated when "__builtin___clear_cache" is compiled.

	   This	 option	 defaults  to  -mno-synci,  but	 the  default  can  be
	   overridden by configuring GCC with --with-synci.

	   When	 compiling  code for single processor systems, it is generally
	   safe	to use "synci".	 However, on many multi-core (SMP) systems, it
	   does	not invalidate the instruction caches on  all  cores  and  may
	   lead	to undefined behavior.

       -mrelax-pic-calls
       -mno-relax-pic-calls
	   Try to turn PIC calls that are normally dispatched via register $25
	   into	direct calls.  This is only possible if	the linker can resolve
	   the destination at link time	and if the destination is within range
	   for a direct	call.

	   -mrelax-pic-calls  is  the  default if GCC was configured to	use an
	   assembler and a linker that support the ".reloc" assembly directive
	   and -mexplicit-relocs is  in	 effect.   With	 -mno-explicit-relocs,
	   this	 optimization can be performed by the assembler	and the	linker
	   alone without help from the compiler.

       -mmcount-ra-address
       -mno-mcount-ra-address
	   Emit	(do not	emit) code that	allows "_mcount" to modify the calling
	   function's return address.  When enabled, this option  extends  the
	   usual  "_mcount"  interface	with a new ra-address parameter, which
	   has type "intptr_t *" and is	passed in register $12.	 "_mcount" can
	   then	modify the return address by doing both	of the following:

	   *   Returning the new address in register $31.

	   *   Storing the new address	in  "*ra-address",  if	ra-address  is
	       nonnull.

	   The default is -mno-mcount-ra-address.

       -mframe-header-opt
       -mno-frame-header-opt
	   Enable  (disable)  frame  header optimization in the	o32 ABI.  When
	   using the o32 ABI, calling functions	will allocate 16 bytes on  the
	   stack  for  the  called  function  to write out register arguments.
	   When	enabled, this optimization will	suppress the allocation	of the
	   frame header	if it can be determined	that it	is unused.

	   This	optimization is	off by default at all optimization levels.

       -mlxc1-sxc1
       -mno-lxc1-sxc1
	   When	 applicable,  enable  (disable)	 the  generation  of  "lwxc1",
	   "swxc1", "ldxc1", "sdxc1" instructions.  Enabled by default.

       -mmadd4
       -mno-madd4
	   When	 applicable,  enable  (disable)	 the  generation  of 4-operand
	   "madd.s", "madd.d" and related instructions.	 Enabled by default.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
	   Specify  that  intrinsic  library  functions	 are  being  compiled,
	   passing all values in registers, no matter the size.

       -mepsilon
       -mno-epsilon
	   Generate  floating-point  comparison	instructions that compare with
	   respect to the "rE" epsilon register.

       -mabi=mmixware
       -mabi=gnu
	   Generate code that passes function  parameters  and	return	values
	   that	 (in  the called function) are seen as registers $0 and	up, as
	   opposed to the GNU ABI which	uses global registers $231 and up.

       -mzero-extend
       -mno-zero-extend
	   When	reading	data from memory in sizes shorter than	64  bits,  use
	   (do	not  use)  zero-extending load instructions by default,	rather
	   than	sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
	   Make	the result of a	division yielding a remainder  have  the  same
	   sign	 as the	divisor.  With the default, -mno-knuthdiv, the sign of
	   the remainder follows the sign of the dividend.  Both  methods  are
	   arithmetically valid, the latter being almost exclusively used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
	   Prepend (do not prepend) a :	to all global symbols, so the assembly
	   code	can be used with the "PREFIX" assembly directive.

       -melf
	   Generate  an	 executable in the ELF format, rather than the default
	   mmo format used by the mmix simulator.

       -mbranch-predict
       -mno-branch-predict
	   Use (do not use)  the  probable-branch  instructions,  when	static
	   branch prediction indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
	   Generate  (do not generate) code that uses base addresses.  Using a
	   base	address	automatically generates	 a  request  (handled  by  the
	   assembler  and  the linker) for a constant to be set	up in a	global
	   register.  The register is  used  for  one  or  more	 base  address
	   requests  within  the  range	 0  to	255 from the value held	in the
	   register.  The generally leads to short  and	 fast  code,  but  the
	   number  of  different  data items that can be addressed is limited.
	   This	means that a program that uses lots of static data may require
	   -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
	   Force (do not force)	generated code to have a single	exit point  in
	   each	function.

       MN10300 Options

       These -m	options	are defined for	Matsushita MN10300 architectures:

       -mmult-bug
	   Generate  code  to  avoid bugs in the multiply instructions for the
	   MN10300 processors.	This is	the default.

       -mno-mult-bug
	   Do not generate code	to avoid bugs in the multiply instructions for
	   the MN10300 processors.

       -mam33
	   Generate code using features	specific to the	AM33 processor.

       -mno-am33
	   Do not generate code	using features specific	to the AM33 processor.
	   This	is the default.

       -mam33-2
	   Generate code using features	specific to the	AM33/2.0 processor.

       -mam34
	   Generate code using features	specific to the	AM34 processor.

       -mtune=cpu-type
	   Use the timing characteristics  of  the  indicated  CPU  type  when
	   scheduling	instructions.	This  does  not	 change	 the  targeted
	   processor type.  The	CPU type must be one of	mn10300, am33,	am33-2
	   or am34.

       -mreturn-pointer-on-d0
	   When	 generating  a	function  that	returns	 a pointer, return the
	   pointer in both "a0"	and "d0".  Otherwise, the pointer is  returned
	   only	 in  "a0",  and	 attempts  to  call  such  functions without a
	   prototype result in	errors.	  Note	that  this  option  is	on  by
	   default; use	-mno-return-pointer-on-d0 to disable it.

       -mno-crt0
	   Do not link in the C	run-time initialization	object file.

       -mrelax
	   Indicate  to	 the  linker  that  it	should	perform	 a  relaxation
	   optimization	pass to	shorten	branches, calls	 and  absolute	memory
	   addresses.  This option only	has an effect when used	on the command
	   line	for the	final link step.

	   This	option makes symbolic debugging	impossible.

       -mliw
	   Allow  the  compiler	to generate Long Instruction Word instructions
	   if the target is the	AM33 or	later.	This  is  the  default.	  This
	   option defines the preprocessor macro "__LIW__".

       -mno-liw
	   Do  not  allow  the	compiler  to  generate	Long  Instruction Word
	   instructions.   This	 option	  defines   the	  preprocessor	 macro
	   "__NO_LIW__".

       -msetlb
	   Allow  the  compiler	 to generate the SETLB and Lcc instructions if
	   the target is the AM33 or later.  This is the default.  This	option
	   defines the preprocessor macro "__SETLB__".

       -mno-setlb
	   Do not allow	the compiler to	generate SETLB	or  Lcc	 instructions.
	   This	option defines the preprocessor	macro "__NO_SETLB__".

       Moxie Options

       -meb
	   Generate  big-endian	 code.	 This  is  the	default	 for moxie-*-*
	   configurations.

       -mel
	   Generate little-endian code.

       -mmul.x
	   Generate mul.x and umul.x instructions.  This is  the  default  for
	   moxiebox-*-*	configurations.

       -mno-crt0
	   Do not link in the C	run-time initialization	object file.

       MSP430 Options

       These options are defined for the MSP430:

       -masm-hex
	   Force  assembly  output to always use hex constants.	 Normally such
	   constants are signed	decimals, but this  option  is	available  for
	   testsuite and/or aesthetic purposes.

       -mmcu=
	   Select  the MCU to target.  This is used to create a	C preprocessor
	   symbol based	upon the MCU name, converted to	upper  case  and  pre-
	   and	post-fixed  with  __.	This  in  turn is used by the msp430.h
	   header file to select an MCU-specific supplementary header file.

	   The option also sets	the ISA	to use.	 If the	MCU name is  one  that
	   is  known  to  only	support	 the  430  ISA	then that is selected,
	   otherwise the 430X ISA is selected.	A generic MCU name  of	msp430
	   can	also  be  used	to  select the 430 ISA.	 Similarly the generic
	   msp430x MCU name selects the	430X ISA.

	   In addition an MCU-specific linker script is	added  to  the	linker
	   command  line.   The	 script's name is the name of the MCU with .ld
	   appended.  Thus  specifying	-mmcu=xxx  on  the  gcc	 command  line
	   defines the C preprocessor symbol "__XXX__" and cause the linker to
	   search for a	script called xxx.ld.

	   The	ISA  and hardware multiply supported for the different MCUs is
	   hard-coded into GCC.	 However, an external devices.csv file can  be
	   used	 to  extend  device  support beyond those that have been hard-
	   coded.

	   GCC searches	for the	devices.csv file using the  following  methods
	   in  the  given  precedence  order,  where  the  first  method takes
	   precendence over the	second which takes precedence over the third.

	   Include path	specified with "-I" and	"-L"
	       devices.csv will	be searched for	in  each  of  the  directories
	       specified by include paths and linker library search paths.

	   Path	specified by the environment variable MSP430_GCC_INCLUDE_DIR
	       Define	the   value   of   the	 global	 environment  variable
	       MSP430_GCC_INCLUDE_DIR  to  the	full  path  to	the  directory
	       containing  devices.csv,	and GCC	will search this directory for
	       devices.csv.  If	devices.csv is found, this directory will also
	       be registered as	an include  path,  and	linker	library	 path.
	       Header files and	linker scripts in this directory can therefore
	       be  used	 without  manually  specifying	"-I"  and  "-L"	on the
	       command line.

	   The msp430-elf{,bare}/include/devices directory
	       Finally,	 GCC  will  examine  msp430-elf{,bare}/include/devices
	       from  the  toolchain  root  directory.  This directory does not
	       exist in	a default installation,	but if the user	has created it
	       and copied devices.csv there, then the MCU data will  be	 read.
	       As  above, this directory will also be registered as an include
	       path, and linker	library	path.

	   If none of the above	search	methods	 find  devices.csv,  then  the
	   hard-coded MCU data is used.

       -mwarn-mcu
       -mno-warn-mcu
	   This	 option	 enables  or disables warnings about conflicts between
	   the MCU name	specified by the -mmcu option and the ISA set  by  the
	   -mcpu  option  and/or  the  hardware	 multiply  support  set	by the
	   -mhwmult option.  It	also toggles warnings about  unrecognized  MCU
	   names.  This	option is on by	default.

       -mcpu=
	   Specifies  the ISA to use.  Accepted	values are msp430, msp430x and
	   msp430xv2.  This option is deprecated.  The -mmcu= option should be
	   used	to select the ISA.

       -msim
	   Link	 to  the  simulator  runtime  libraries	 and  linker   script.
	   Overrides any scripts that would be selected	by the -mmcu= option.

       -mlarge
	   Use large-model addressing (20-bit pointers,	20-bit "size_t").

       -msmall
	   Use small-model addressing (16-bit pointers,	16-bit "size_t").

       -mrelax
	   This	 option	 is passed to the assembler and	linker,	and allows the
	   linker to perform certain optimizations that	cannot be  done	 until
	   the final link.

       mhwmult=
	   Describes  the  type	 of hardware multiply supported	by the target.
	   Accepted values are none for	no hardware multiply,  16bit  for  the
	   original  16-bit-only  multiply supported by	early MCUs.  32bit for
	   the 16/32-bit multiply supported by later MCUs and f5series for the
	   16/32-bit multiply supported	by F5-series MCUs.  A  value  of  auto
	   can	also be	given.	This tells GCC to deduce the hardware multiply
	   support based upon the MCU name provided by the -mmcu  option.   If
	   no  -mmcu  option is	specified or if	the MCU	name is	not recognized
	   then	no hardware  multiply  support	is  assumed.   "auto"  is  the
	   default setting.

	   Hardware  multiplies	 are  normally	performed by calling a library
	   routine.  This saves	space in the generated code.   When  compiling
	   at -O3 or higher however the	hardware multiplier is invoked inline.
	   This	makes for bigger, but faster code.

	   The	hardware  multiply  routines disable interrupts	whilst running
	   and restore the previous interrupt state when  they	finish.	  This
	   makes  them	safe  to  use  inside interrupt	handlers as well as in
	   normal code.

       -minrt
	   Enable the use  of  a  minimum  runtime  environment	 -  no	static
	   initializers	  or  constructors.   This  is	intended  for  memory-
	   constrained devices.	 The compiler includes special symbols in some
	   objects that	tell the linker	and runtime which code	fragments  are
	   required.

       -mtiny-printf
	   Enable  reduced  code  size	"printf" and "puts" library functions.
	   The tiny implementations of these functions are not	reentrant,  so
	   must	be used	with caution in	multi-threaded applications.

	   Support  for	 streams has been removed and the string to be printed
	   will	always be sent to stdout via the "write" syscall.  The	string
	   is not buffered before it is	sent to	write.

	   This	option requires	Newlib Nano IO,	so GCC must be configured with
	   --enable-newlib-nano-formatted-io.

       -mmax-inline-shift=
	   This	 option	 takes an integer between 0 and	64 inclusive, and sets
	   the maximum number of inline	shift  instructions  which  should  be
	   emitted  to	perform	 a shift operation by a	constant amount.  When
	   this	value needs to be exceeded, an mspabi helper function is  used
	   instead.  The default value is 4.

	   This	 only affects cases where a shift by multiple positions	cannot
	   be completed	with a single instruction (e.g.	all shifts >1  on  the
	   430 ISA).

	   Shifts of a 32-bit value are	at least twice as costly, so the value
	   passed for this option is divided by	2 and the resulting value used
	   instead.

       -mcode-region=
       -mdata-region=
	   These  options  tell	the compiler where to place functions and data
	   that	do not have one	of the "lower",	"upper", "either" or "section"
	   attributes.	Possible values	 are  "lower",	"upper",  "either"  or
	   "any".   The	 first	three behave like the corresponding attribute.
	   The fourth possible value - "any" -	is  the	 default.   It	leaves
	   placement  entirely	up to the linker script	and how	it assigns the
	   standard sections (".text", ".data",	etc) to	the memory regions.

       -msilicon-errata=
	   This	option passes on a request to assembler	to  enable  the	 fixes
	   for the named silicon errata.

       -msilicon-errata-warn=
	   This	 option	passes on a request to the assembler to	enable warning
	   messages when a silicon errata might	need to	be applied.

       -mwarn-devices-csv
       -mno-warn-devices-csv
	   Warn	if devices.csv is not found or there are  problem  parsing  it
	   (default: on).

       NDS32 Options

       These options are defined for NDS32 implementations:

       -mbig-endian
	   Generate code in big-endian mode.

       -mlittle-endian
	   Generate code in little-endian mode.

       -mreduced-regs
	   Use reduced-set registers for register allocation.

       -mfull-regs
	   Use full-set	registers for register allocation.

       -mcmov
	   Generate conditional	move instructions.

       -mno-cmov
	   Do not generate conditional move instructions.

       -mext-perf
	   Generate performance	extension instructions.

       -mno-ext-perf
	   Do not generate performance extension instructions.

       -mext-perf2
	   Generate performance	extension 2 instructions.

       -mno-ext-perf2
	   Do not generate performance extension 2 instructions.

       -mext-string
	   Generate string extension instructions.

       -mno-ext-string
	   Do not generate string extension instructions.

       -mv3push
	   Generate v3 push25/pop25 instructions.

       -mno-v3push
	   Do not generate v3 push25/pop25 instructions.

       -m16-bit
	   Generate 16-bit instructions.

       -mno-16-bit
	   Do not generate 16-bit instructions.

       -misr-vector-size=num
	   Specify the size of each interrupt vector, which must be 4 or 16.

       -mcache-block-size=num
	   Specify  the	 size  of each cache block, which must be a power of 2
	   between 4 and 512.

       -march=arch
	   Specify the name of the target architecture.

       -mcmodel=code-model
	   Set the code	model to one of

	   small
	       All the data and	read-only data segments	must be	 within	 512KB
	       addressing  space.   The	 text  segment	must  be  within  16MB
	       addressing space.

	   medium
	       The data	segment	must be	within 512KB while the read-only  data
	       segment	can  be	within 4GB addressing space.  The text segment
	       should be still within 16MB addressing space.

	   large
	       All the text and	data segments can  be  within  4GB  addressing
	       space.

       -mctor-dtor
	   Enable constructor/destructor feature.

       -mrelax
	   Guide linker	to relax instructions.

       Nios II Options

       These are the options defined for the Altera Nios II processor.

       -G num
	   Put	global and static objects less than or equal to	num bytes into
	   the small data or BSS sections instead of the normal	 data  or  BSS
	   sections.  The default value	of num is 8.

       -mgpopt=option
       -mgpopt
       -mno-gpopt
	   Generate  (do  not  generate)  GP-relative accesses.	 The following
	   option names	are recognized:

	   none
	       Do not generate GP-relative accesses.

	   local
	       Generate	GP-relative accesses for small data objects  that  are
	       not  external, weak, or uninitialized common symbols.  Also use
	       GP-relative addressing for objects that	have  been  explicitly
	       placed in a small data section via a "section" attribute.

	   global
	       As  for local, but also generate	GP-relative accesses for small
	       data objects that are external, weak, or	common.	  If  you  use
	       this  option,  you  must	 ensure	that all parts of your program
	       (including libraries) are compiled with the same	-G setting.

	   data
	       Generate	GP-relative accesses  for  all	data  objects  in  the
	       program.	  If  you  use	this  option,  the entire data and BSS
	       segments	of your	program	must fit in 64K	of memory and you must
	       use an appropriate linker script	to allocate  them  within  the
	       addressable range of the	global pointer.

	   all Generate	GP-relative addresses for function pointers as well as
	       data  pointers.	If you use this	option,	the entire text, data,
	       and BSS segments	of your	program	must fit in 64K	of memory  and
	       you  must  use  an  appropriate	linker script to allocate them
	       within the addressable range of the global pointer.

	   -mgpopt  is	equivalent  to	-mgpopt=local,	 and   -mno-gpopt   is
	   equivalent to -mgpopt=none.

	   The	default	 is -mgpopt except when	-fpic or -fPIC is specified to
	   generate position-independent code.	Note that the Nios II ABI does
	   not permit GP-relative accesses from	shared libraries.

	   You	may  need  to  specify	-mno-gpopt  explicitly	when  building
	   programs  that include large	amounts	of small data, including large
	   GOT data sections.  In this case, the 16-bit	offset for GP-relative
	   addressing may not be large enough to allow access  to  the	entire
	   small data section.

       -mgprel-sec=regexp
	   This	option specifies additional section names that can be accessed
	   via	GP-relative addressing.	 It is most useful in conjunction with
	   "section" attributes	on variable declarations and a	custom	linker
	   script.  The	regexp is a POSIX Extended Regular Expression.

	   This	 option	does not affect	the behavior of	the -G option, and the
	   specified sections are in addition to  the  standard	 ".sdata"  and
	   ".sbss" small-data sections that are	recognized by -mgpopt.

       -mr0rel-sec=regexp
	   This	 option	specifies names	of sections that can be	accessed via a
	   16-bit offset from "r0"; that is, in	the low	32K or high 32K	of the
	   32-bit address space.   It  is  most	 useful	 in  conjunction  with
	   "section"  attributes  on variable declarations and a custom	linker
	   script.  The	regexp is a POSIX Extended Regular Expression.

	   In contrast to the use of GP-relative addressing  for  small	 data,
	   zero-based  addressing  is never generated by default and there are
	   no conventional section names used in standard linker  scripts  for
	   sections in the low or high areas of	memory.

       -mel
       -meb
	   Generate little-endian (default) or big-endian (experimental) code,
	   respectively.

       -march=arch
	   This	 specifies  the	 name of the target Nios II architecture.  GCC
	   uses	this name to determine what kind of instructions it  can  emit
	   when	generating assembly code.  Permissible names are: r1, r2.

	   The	preprocessor  macro "__nios2_arch__" is	available to programs,
	   with	value 1	or 2, indicating the targeted ISA level.

       -mbypass-cache
       -mno-bypass-cache
	   Force all load and store instructions to  always  bypass  cache  by
	   using  I/O  variants	 of  the  instructions.	 The default is	not to
	   bypass the cache.

       -mno-cache-volatile
       -mcache-volatile
	   Volatile memory access bypass the cache using the I/O  variants  of
	   the	load  and store	instructions. The default is not to bypass the
	   cache.

       -mno-fast-sw-div
       -mfast-sw-div
	   Do not use table-based fast divide for small	numbers.  The  default
	   is to use the fast divide at	-O3 and	above.

       -mno-hw-mul
       -mhw-mul
       -mno-hw-mulx
       -mhw-mulx
       -mno-hw-div
       -mhw-div
	   Enable  or  disable	emitting  "mul",  "mulx"  and  "div" family of
	   instructions	by the compiler. The default is	to emit	"mul" and  not
	   emit	"div" and "mulx".

       -mbmx
       -mno-bmx
       -mcdx
       -mno-cdx
	   Enable  or  disable generation of Nios II R2	BMX (bit manipulation)
	   and CDX (code density) instructions.	 Enabling  these  instructions
	   also	 requires  -march=r2.	Since  these instructions are optional
	   extensions to the R2	architecture, the default is not to emit them.

       -mcustom-insn=N
       -mno-custom-insn
	   Each	-mcustom-insn=N	option enables use  of	a  custom  instruction
	   with	 encoding N when generating code that uses insn.  For example,
	   -mcustom-fadds=253 generates	custom	instruction  253  for  single-
	   precision  floating-point  add  operations  instead	of the default
	   behavior of using a library call.

	   The following values	of insn	are supported.	 Except	 as  otherwise
	   noted,  floating-point  operations  are  expected to	be implemented
	   with	normal IEEE 754	semantics and correspond  directly  to	the  C
	   operators or	the equivalent GCC built-in functions.

	   Single-precision floating point:

	   fadds, fsubs, fdivs,	fmuls
	       Binary arithmetic operations.

	   fnegs
	       Unary negation.

	   fabss
	       Unary absolute value.

	   fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts,	fcmpnes
	       Comparison operations.

	   fmins, fmaxs
	       Floating-point  minimum	and  maximum.	These instructions are
	       only generated if -ffinite-math-only is specified.

	   fsqrts
	       Unary square root operation.

	   fcoss, fsins, ftans,	fatans,	fexps, flogs
	       Floating-point trigonometric and	exponential functions.	 These
	       instructions  are only generated	if -funsafe-math-optimizations
	       is also specified.

	   Double-precision floating point:

	   faddd, fsubd, fdivd,	fmuld
	       Binary arithmetic operations.

	   fnegd
	       Unary negation.

	   fabsd
	       Unary absolute value.

	   fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd,	fcmpned
	       Comparison operations.

	   fmind, fmaxd
	       Double-precision	minimum	and maximum.  These  instructions  are
	       only generated if -ffinite-math-only is specified.

	   fsqrtd
	       Unary square root operation.

	   fcosd, fsind, ftand,	fatand,	fexpd, flogd
	       Double-precision	  trigonometric	  and  exponential  functions.
	       These	 instructions	  are	   only	     generated	    if
	       -funsafe-math-optimizations is also specified.

	   Conversions:

	   fextsd
	       Conversion from single precision	to double precision.

	   ftruncds
	       Conversion from double precision	to single precision.

	   fixsi, fixsu, fixdi,	fixdu
	       Conversion  from	 floating  point to signed or unsigned integer
	       types, with truncation towards zero.

	   round
	       Conversion  from	 single-precision  floating  point  to	signed
	       integer,	 rounding  to  the  nearest integer and	ties away from
	       zero.  This corresponds	to  the	 "__builtin_lroundf"  function
	       when -fno-math-errno is used.

	   floatis, floatus, floatid, floatud
	       Conversion  from	 signed	or unsigned integer types to floating-
	       point types.

	   In  addition,  all  of  the	following  transfer  instructions  for
	   internal  registers	X  and	Y  must	 be provided to	use any	of the
	   double-precision floating-point instructions.  Custom  instructions
	   taking  two	double-precision  source  operands  expect  the	 first
	   operand in the 64-bit register  X.	The  other  operand  (or  only
	   operand  of	a  unary  operation) is	given to the custom arithmetic
	   instruction with the	least significant half in source register src1
	   and the most	significant half in src2.  A custom  instruction  that
	   returns  a  double-precision	result returns the most	significant 32
	   bits	in the destination register  and  the  other  half  in	32-bit
	   register   Y.   GCC	automatically  generates  the  necessary  code
	   sequences to	write register X and/or	read register Y	 when  double-
	   precision floating-point instructions are used.

	   fwrx
	       Write  src1  into the least significant half of X and src2 into
	       the most	significant half of X.

	   fwry
	       Write src1 into Y.

	   frdxhi, frdxlo
	       Read the	most or	least (respectively) significant half of X and
	       store it	in dest.

	   frdy
	       Read the	value of Y and store it	into dest.

	   Note	that you can gain more local control over generation  of  Nios
	   II  custom  instructions by using the "target("custom-insn=N")" and
	   "target("no-custom-insn")" function attributes or pragmas.

       -mcustom-fpu-cfg=name
	   This	option enables a predefined, named set of  custom  instruction
	   encodings (see -mcustom-insn	above).	 Currently, the	following sets
	   are defined:

	   -mcustom-fpu-cfg=60-1    is	 equivalent   to:   -mcustom-fmuls=252
	   -mcustom-fadds=253 -mcustom-fsubs=254 -fsingle-precision-constant

	   -mcustom-fpu-cfg=60-2   is	equivalent   to:    -mcustom-fmuls=252
	   -mcustom-fadds=253	    -mcustom-fsubs=254	    -mcustom-fdivs=255
	   -fsingle-precision-constant

	   -mcustom-fpu-cfg=72-3  is   equivalent   to:	  -mcustom-floatus=243
	   -mcustom-fixsi=244	  -mcustom-floatis=245	  -mcustom-fcmpgts=246
	   -mcustom-fcmples=249	  -mcustom-fcmpeqs=250	  -mcustom-fcmpnes=251
	   -mcustom-fmuls=252	    -mcustom-fadds=253	    -mcustom-fsubs=254
	   -mcustom-fdivs=255 -fsingle-precision-constant

	   -mcustom-fpu-cfg=fph2   is	equivalent   to:    -mcustom-fabss=224
	   -mcustom-fnegs=225	  -mcustom-fcmpnes=226	  -mcustom-fcmpeqs=227
	   -mcustom-fcmpges=228	  -mcustom-fcmpgts=229	  -mcustom-fcmples=230
	   -mcustom-fcmplts=231	     -mcustom-fmaxs=232	    -mcustom-fmins=233
	   -mcustom-round=248	  -mcustom-fixsi=249	  -mcustom-floatis=250
	   -mcustom-fsqrts=251	    -mcustom-fmuls=252	    -mcustom-fadds=253
	   -mcustom-fsubs=254 -mcustom-fdivs=255

	   Custom instruction assignments given	by  individual	-mcustom-insn=
	   options  override  those  given by -mcustom-fpu-cfg=, regardless of
	   the order of	the options on the command line.

	   Note	that you can gain more local control over selection of	a  FPU
	   configuration by using the "target("custom-fpu-cfg=name")" function
	   attribute or	pragma.

	   The	name  fph2  is	an  abbreviation  for  Nios  II	Floating Point
	   Hardware 2 Component.  Please note  that  the  custom  instructions
	   enabled  by	-mcustom-fmins=233  and	 -mcustom-fmaxs=234  are  only
	   generated  if  -ffinite-math-only   is   specified.	  The	custom
	   instruction	enabled	 by  -mcustom-round=248	 is  only generated if
	   -fno-math-errno  is	specified.    In   contrast   to   the	 other
	   configurations, -fsingle-precision-constant is not set.

       These  additional  -m  options are available for	the Altera Nios	II ELF
       (bare-metal) target:

       -mhal
	   Link	with HAL BSP.  This suppresses linking with the	GCC-provided C
	   runtime startup and termination code,  and  is  typically  used  in
	   conjunction	with  -msys-crt0=  to  specify	the  location  of  the
	   alternate startup code provided by the HAL BSP.

       -msmallc
	   Link	with a limited version of the C	library, -lsmallc, rather than
	   Newlib.

       -msys-crt0=startfile
	   startfile is	the file name of the  startfile	 (crt0)	 to  use  when
	   linking.  This option is only useful	in conjunction with -mhal.

       -msys-lib=systemlib
	   systemlib  is  the  library	name of	the library that provides low-
	   level system	calls required by  the	C  library,  e.g.  "read"  and
	   "write".   This  option  is	typically  used	to link	with a library
	   provided by a HAL BSP.

       Nvidia PTX Options

       These options are defined for Nvidia PTX:

       -m64
	   Ignored, but	preserved for backward compatibility.  Only 64-bit ABI
	   is supported.

       -misa=ISA-string
	   Generate code for given the specified PTX ISA  (e.g.	 sm_35).   ISA
	   strings  must  be  lower-case.  Valid ISA strings include sm_30 and
	   sm_35.  The default ISA is sm_35.

       -mmainkernel
	   Link	in code	for a __main kernel.  This is for stand-alone  instead
	   of offloading execution.

       -moptimize
	   Apply  partitioned  execution  optimizations.   This	is the default
	   when	any level of optimization is selected.

       -msoft-stack
	   Generate code that does not use ".local" memory directly for	 stack
	   storage.   Instead,	 a   per-warp	stack  pointer	is  maintained
	   explicitly. This enables  variable-length  stack  allocation	 (with
	   variable-length arrays or "alloca"),	and when global	memory is used
	   for	underlying  storage,  makes  it	 possible  to access automatic
	   variables from other	threads, or  with  atomic  instructions.  This
	   code	 generation  variant  is  used	for OpenMP offloading, but the
	   option is exposed on	 its  own  for	the  purpose  of  testing  the
	   compiler; to	generate code suitable for linking into	programs using
	   OpenMP offloading, use option -mgomp.

       -muniform-simt
	   Switch  to  code  generation	 variant  that	allows	to execute all
	   threads in each warp,  while	 maintaining  memory  state  and  side
	   effects  as	if  only one thread in each warp was active outside of
	   OpenMP SIMD regions.	 All atomic operations and  calls  to  runtime
	   (malloc,  free,  vprintf)  are  conditionally executed (iff current
	   lane	index equals the master	lane index), and  the  register	 being
	   assigned  is	copied via a shuffle instruction from the master lane.
	   Outside of SIMD regions lane	0 is the master; inside,  each	thread
	   sees	itself as the master.  Shared memory array "int	__nvptx_uni[]"
	   stores  all-zeros  or  all-ones  bitmasks for each warp, indicating
	   current mode	(0 outside of SIMD regions).  Each thread can bitwise-
	   and the bitmask at position "tid.y"	with  current  lane  index  to
	   compute the master lane index.

       -mgomp
	   Generate  code  for	use in OpenMP offloading: enables -msoft-stack
	   and -muniform-simt  options,	 and  selects  corresponding  multilib
	   variant.

       OpenRISC	Options

       These options are defined for OpenRISC:

       -mboard=name
	   Configure  a	 board	specific  runtime.  This will be passed	to the
	   linker for newlib board library linking.  The default is "or1ksim".

       -mnewlib
	   This	option is ignored; it  is  for	compatibility  purposes	 only.
	   This	 used  to  select linker and preprocessor options for use with
	   newlib.

       -msoft-div
       -mhard-div
	   Select   software   or   hardware   divide	("l.div",    "l.divu")
	   instructions.  This default is hardware divide.

       -msoft-mul
       -mhard-mul
	   Select   software   or   hardware   multiply	  ("l.mul",  "l.muli")
	   instructions.  This default is hardware multiply.

       -msoft-float
       -mhard-float
	   Select software or hardware for  floating  point  operations.   The
	   default is software.

       -mdouble-float
	   When	 -mhard-float  is  selected,  enables  generation  of  double-
	   precision floating point instructions.  By default  functions  from
	   libgcc   are	  used	to  perform  double-precision  floating	 point
	   operations.

       -munordered-float
	   When	-mhard-float is	 selected,  enables  generation	 of  unordered
	   floating  point compare and set flag	("lf.sfun*") instructions.  By
	   default  functions  from  libgcc  are  used	to  perform  unordered
	   floating point compare and set flag operations.

       -mcmov
	   Enable  generation of conditional move ("l.cmov") instructions.  By
	   default the equivalent will be generated using set and branch.

       -mror
	   Enable generation  of  rotate  right	 ("l.ror")  instructions.   By
	   default  functions  from  libgcc  are  used to perform rotate right
	   operations.

       -mrori
	   Enable  generation  of  rotate  right  with	immediate   ("l.rori")
	   instructions.  By default functions from libgcc are used to perform
	   rotate right	with immediate operations.

       -msext
	   Enable  generation  of  sign	extension ("l.ext*") instructions.  By
	   default memory loads	are used to perform sign extension.

       -msfimm
	   Enable generation of	compare	and set	flag with immediate ("l.sf*i")
	   instructions.  By default extra instructions	will be	 generated  to
	   store the immediate to a register first.

       -mshftimm
	   Enable  generation  of  shift  with	immediate ("l.srai", "l.srli",
	   "l.slli") instructions.  By	default	 extra	instructions  will  be
	   generated to	store the immediate to a register first.

       PDP-11 Options

       These options are defined for the PDP-11:

       -mfpu
	   Use	hardware  FPP  floating	 point.	  This	is  the	default.  (FIS
	   floating point on the PDP-11/40 is not supported.)  Implies -m45.

       -msoft-float
	   Do not use hardware floating	point.

       -mac0
	   Return  floating-point  results  in	ac0  (fr0  in  Unix  assembler
	   syntax).

       -mno-ac0
	   Return floating-point results in memory.  This is the default.

       -m40
	   Generate code for a PDP-11/40.  Implies -msoft-float	-mno-split.

       -m45
	   Generate code for a PDP-11/45.  This	is the default.

       -m10
	   Generate code for a PDP-11/10.  Implies -msoft-float	-mno-split.

       -mint16
       -mno-int32
	   Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
	   Use 32-bit "int".

       -msplit
	   Target has split instruction	and data space.	 Implies -m45.

       -munix-asm
	   Use Unix assembler syntax.

       -mdec-asm
	   Use DEC assembler syntax.

       -mgnu-asm
	   Use GNU assembler syntax.  This is the default.

       -mlra
	   Use	the  new LRA register allocator.  By default, the old "reload"
	   allocator is	used.

       picoChip	Options

       These -m	options	are defined for	picoChip implementations:

       -mae=ae_type
	   Set the instruction set, register set, and  instruction  scheduling
	   parameters  for  array  element type	ae_type.  Supported values for
	   ae_type are ANY, MUL, and MAC.

	   -mae=ANY selects a completely generic AE type.  Code	generated with
	   this	option runs on any of the other	AE types.  The code is not  as
	   efficient  as  it  would be if compiled for a specific AE type, and
	   some	types of operation (e.g., multiplication) do not work properly
	   on all types	of AE.

	   -mae=MUL selects a MUL AE type.  This is the	most  useful  AE  type
	   for compiled	code, and is the default.

	   -mae=MAC  selects  a	 DSP-style  MAC	 AE.   Code compiled with this
	   option  may	suffer	from   poor   performance   of	 byte	(char)
	   manipulation,  since	 the  DSP AE does not provide hardware support
	   for byte load/stores.

       -msymbol-as-address
	   Enable the compiler to directly use a symbol	name as	an address  in
	   a load/store	instruction, without first loading it into a register.
	   Typically,  the use of this option generates	larger programs, which
	   run faster than when	the option isn't used.	However,  the  results
	   vary	 from  program	to  program,  so  it is	left as	a user option,
	   rather than being permanently enabled.

       -mno-inefficient-warnings
	   Disables warnings about the generation of inefficient code.	 These
	   warnings  can  be  generated, for example, when compiling code that
	   performs byte-level memory operations on the	MAC AE type.  The  MAC
	   AE has no hardware support for byte-level memory operations,	so all
	   byte	  load/stores	must   be  synthesized	from  word  load/store
	   operations.	This is	inefficient and	 a  warning  is	 generated  to
	   indicate that you should rewrite the	code to	avoid byte operations,
	   or  to  target  an AE type that has the necessary hardware support.
	   This	option disables	these warnings.

       PowerPC Options

       These are listed	under

       PRU Options

       These command-line options are defined for PRU target:

       -minrt
	   Link	with a minimum runtime environment, with no support for	static
	   initializers	and constructors.  Using this option can significantly
	   reduce the size of the final	ELF binary.  Beware that the  compiler
	   could   still   generate   code   with   static   initializers  and
	   constructors.  It is	up to the programmer to	ensure that the	source
	   program will	not use	those features.

       -mmcu=mcu
	   Specify the PRU MCU variant to use.	Check  Newlib  for  the	 exact
	   list	of supported MCUs.

       -mno-relax
	   Make	 GCC  pass  the	 --no-relax  command-line option to the	linker
	   instead of the --relax option.

       -mloop
	   Allow (or do	not allow) GCC to use the LOOP instruction.

       -mabi=variant
	   Specify the ABI variant to output code for.	-mabi=ti  selects  the
	   unmodified  TI ABI while -mabi=gnu selects a	GNU variant that copes
	   more	 naturally  with  certain  GCC	assumptions.   These  are  the
	   differences:

	   Function Pointer Size
	       TI  ABI	specifies  that	 function  (code) pointers are 16-bit,
	       whereas GNU supports only 32-bit	data and code pointers.

	   Optional Return Value Pointer
	       Function	return values larger than 64 bits are passed by	 using
	       a  hidden  pointer  as  the first argument of the function.  TI
	       ABI, though, mandates that the pointer can be NULL in case  the
	       caller  is not using the	returned value.	 GNU always passes and
	       expects a valid return value pointer.

	   The current -mabi=ti	implementation simply raises a	compile	 error
	   when	  any  of  the	above  code  constructs	 is  detected.	 As  a
	   consequence the standard C  library	cannot	be  built  and	it  is
	   omitted when	linking	with -mabi=ti.

	   Relaxation is a GNU feature and for safety reasons is disabled when
	   using  -mabi=ti.   The  TI  toolchain does not emit relocations for
	   QBBx	instructions, so  the  GNU  linker  cannot  adjust  them  when
	   shortening adjacent LDI32 pseudo instructions.

       RISC-V Options

       These command-line options are defined for RISC-V targets:

       -mbranch-cost=n
	   Set the cost	of branches to roughly n instructions.

       -mplt
       -mno-plt
	   When	 generating  PIC  code,	 do  or	 don't	allow the use of PLTs.
	   Ignored for non-PIC.	 The default is	-mplt.

       -mabi=ABI-string
	   Specify integer and floating-point calling convention.   ABI-string
	   contains  two  parts:  the  size of integer types and the registers
	   used	 for  floating-point  types.	For   example	-march=rv64ifd
	   -mabi=lp64d	means  that  long  and pointers	are 64-bit (implicitly
	   defining int	to be 32-bit), and that	floating-point values up to 64
	   bits	 wide  are  passed  in	F  registers.	Contrast   this	  with
	   -march=rv64ifd  -mabi=lp64f,	 which	still  allows  the compiler to
	   generate code that uses the F and  D	 extensions  but  only	allows
	   floating-point values up to 32 bits long to be passed in registers;
	   or  -march=rv64ifd -mabi=lp64, in which no floating-point arguments
	   will	be passed in registers.

	   The default for this	argument is system dependent, users who	want a
	   specific calling convention should  specify	one  explicitly.   The
	   valid  calling conventions are: ilp32, ilp32f, ilp32d, lp64,	lp64f,
	   and lp64d.  Some calling conventions	are impossible to implement on
	   some	ISAs:  for  example,  -march=rv32if  -mabi=ilp32d  is  invalid
	   because  the	 ABI  requires 64-bit values be	passed in F registers,
	   but F registers are only 32 bits wide.  There is  also  the	ilp32e
	   ABI that can	only be	used with the rv32e architecture.  This	ABI is
	   not well specified at present, and is subject to change.

       -mfdiv
       -mno-fdiv
	   Do  or  don't  use  hardware	 floating-point	divide and square root
	   instructions.  This requires	the F or D  extensions	for  floating-
	   point  registers.   The  default  is	 to  use them if the specified
	   architecture	has these instructions.

       -mdiv
       -mno-div
	   Do or don't use hardware instructions for integer  division.	  This
	   requires  the  M  extension.	  The  default	is  to use them	if the
	   specified architecture has these instructions.

       -march=ISA-string
	   Generate code for given RISC-V ISA (e.g. rv64im).  ISA strings must
	   be lower-case.  Examples include rv64i, rv32g, rv32e, and rv32imaf.

	   When	-march=	is not specified, use the setting from -mcpu.

	   If both -march and -mcpu= are not specified,	the default  for  this
	   argument   is   system   dependent,	 users	who  want  a  specific
	   architecture	extensions should specify one explicitly.

       -mcpu=processor-string
	   Use	architecture  of  and  optimize	 the  output  for  the	 given
	   processor,  specified  by  particular CPU name.  Permissible	values
	   for	this   option	are:   sifive-e20,   sifive-e21,   sifive-e24,
	   sifive-e31,	 sifive-e34,   sifive-e76,   sifive-s21,   sifive-s51,
	   sifive-s54, sifive-s76, sifive-u54, and sifive-u74.

       -mtune=processor-string
	   Optimize  the  output  for  the  given  processor,	specified   by
	   microarchitecture  or  particular CPU name.	Permissible values for
	   this	 option	  are:	 rocket,   sifive-3-series,   sifive-5-series,
	   sifive-7-series, size, and all valid	options	for -mcpu=.

	   When	 -mtune=  is  not  specified,  use the setting from -mcpu, the
	   default is rocket if	both are not specified.

	   The size choice is not intended for use by end-users.  This is used
	   when	-Os is specified.  It  overrides  the  instruction  cost  info
	   provided by -mtune=,	but does not override the pipeline info.  This
	   helps reduce	code size while	still giving good performance.

       -mpreferred-stack-boundary=num
	   Attempt  to	keep  the  stack boundary aligned to a 2 raised	to num
	   byte	boundary.  If -mpreferred-stack-boundary is not	specified, the
	   default is 4	(16 bytes or 128-bits).

	   Warning: If you use this switch, then you must  build  all  modules
	   with	 the  same  value, including any libraries.  This includes the
	   system libraries and	startup	modules.

       -msmall-data-limit=n
	   Put global and static data smaller than  n  bytes  into  a  special
	   section (on some targets).

       -msave-restore
       -mno-save-restore
	   Do  or don't	use smaller but	slower prologue	and epilogue code that
	   uses	library	function calls.	 The default is	 to  use  fast	inline
	   prologues and epilogues.

       -mshorten-memrefs
       -mno-shorten-memrefs
	   Do  or  do  not  attempt  to	make more use of compressed load/store
	   instructions	by replacing a load/store of 'base  register  +	 large
	   offset' with	a new load/store of 'new base +	small offset'.	If the
	   new	base  gets  stored  in	a  compressed  register,  then the new
	   load/store can be compressed.   Currently  targets  32-bit  integer
	   load/stores only.

       -mstrict-align
       -mno-strict-align
	   Do  not  or	do generate unaligned memory accesses.	The default is
	   set depending on  whether  the  processor  we  are  optimizing  for
	   supports fast unaligned access or not.

       -mcmodel=medlow
	   Generate  code  for	the medium-low code model. The program and its
	   statically defined symbols must lie within a	single 2  GiB  address
	   range  and  must  lie between absolute addresses -2 GiB and +2 GiB.
	   Programs can	be statically  or  dynamically	linked.	 This  is  the
	   default code	model.

       -mcmodel=medany
	   Generate  code  for	the medium-any code model. The program and its
	   statically defined symbols must be within any single	2 GiB  address
	   range. Programs can be statically or	dynamically linked.

       -mexplicit-relocs
       -mno-exlicit-relocs
	   Use	or do not use assembler	relocation operators when dealing with
	   symbolic addresses.	The alternative	is  to	use  assembler	macros
	   instead, which may limit optimization.

       -mrelax
       -mno-relax
	   Take	 advantage  of	linker	relaxations  to	 reduce	 the number of
	   instructions	required to materialize	symbol addresses. The  default
	   is to take advantage	of linker relaxations.

       -memit-attribute
       -mno-emit-attribute
	   Emit	 (do  not  emit)  RISC-V attribute to record extra information
	   into	ELF objects.  This feature requires at least binutils 2.32.

       -malign-data=type
	   Control how GCC aligns variables and	constants of array, structure,
	   or union types.  Supported values for type are xlen	which  uses  x
	   register  width  as	the  alignment	value,	and natural which uses
	   natural alignment.  xlen is the default.

       -mbig-endian
	   Generate  big-endian	 code.	 This  is  the	default	 when  GCC  is
	   configured for a riscv64be-*-* or riscv32be-*-* target.

       -mlittle-endian
	   Generate  little-endian  code.   This  is  the  default when	GCC is
	   configured for a riscv64-*-*	or riscv32-*-* but not a riscv64be-*-*
	   or riscv32be-*-* target.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
	   Generate stack protection code using	canary	at  guard.   Supported
	   locations  are  global  for	a  global canary or tls	for per-thread
	   canary in the TLS block.

	   With	the latter choice the options  -mstack-protector-guard-reg=reg
	   and -mstack-protector-guard-offset=offset furthermore specify which
	   register  to	 use as	base register for reading the canary, and from
	   what	offset from that base register.	There is no  default  register
	   or offset as	this is	entirely for use within	the Linux kernel.

       RL78 Options

       -msim
	   Links  in additional	target libraries to support operation within a
	   simulator.

       -mmul=none
       -mmul=g10
       -mmul=g13
       -mmul=g14
       -mmul=rl78
	   Specifies the type of hardware multiplication and division  support
	   to  be  used.  The simplest is "none", which	uses software for both
	   multiplication and division.	 This is the default.  The "g13" value
	   is  for  the	 hardware  multiply/divide  peripheral	found  on  the
	   RL78/G13 (S2	core) targets.	The "g14" value	selects	the use	of the
	   multiplication  and division	instructions supported by the RL78/G14
	   (S3 core) parts.  The value "rl78" is an alias for  "g14"  and  the
	   value "mg10"	is an alias for	"none".

	   In  addition	 a  C  preprocessor  macro  is defined,	based upon the
	   setting of this option.  Possible values are:  "__RL78_MUL_NONE__",
	   "__RL78_MUL_G13__" or "__RL78_MUL_G14__".

       -mcpu=g10
       -mcpu=g13
       -mcpu=g14
       -mcpu=rl78
	   Specifies  the  RL78	 core to target.  The default is the G14 core,
	   also	known as an S3 core or just RL78.  The G13 or S2 core does not
	   have	multiply or divide instructions, instead it  uses  a  hardware
	   peripheral  for these operations.  The G10 or S1 core does not have
	   register banks, so it uses a	different calling convention.

	   If this option is set it also selects the type of hardware multiply
	   support to use, unless this is overridden by	an explicit -mmul=none
	   option on the command line.	Thus specifying	-mcpu=g13 enables  the
	   use	 of  the  G13  hardware	 multiply  peripheral  and  specifying
	   -mcpu=g10 disables the use of hardware multiplications altogether.

	   Note, although the RL78/G14 core is the default target,  specifying
	   -mcpu=g14  or  -mcpu=rl78  on  the  command	line  does  change the
	   behavior of the  toolchain  since  it  also	enables	 G14  hardware
	   multiply  support.	If  these  options  are	 not  specified	on the
	   command line	then software multiplication  routines	will  be  used
	   even	 though	the code targets the RL78 core.	 This is for backwards
	   compatibility with older toolchains which  did  not	have  hardware
	   multiply and	divide support.

	   In  addition	 a  C  preprocessor  macro  is defined,	based upon the
	   setting of  this  option.   Possible	 values	 are:  "__RL78_G10__",
	   "__RL78_G13__" or "__RL78_G14__".

       -mg10
       -mg13
       -mg14
       -mrl78
	   These  are  aliases	for the	corresponding -mcpu= option.  They are
	   provided for	backwards compatibility.

       -mallregs
	   Allow the compiler to use  all  of  the  available  registers.   By
	   default  registers  "r24..r31"  are	reserved  for use in interrupt
	   handlers.  With this	option enabled these registers can be used  in
	   ordinary functions as well.

       -m64bit-doubles
       -m32bit-doubles
	   Make	the "double" data type be 64 bits (-m64bit-doubles) or 32 bits
	   (-m32bit-doubles) in	size.  The default is -m32bit-doubles.

       -msave-mduc-in-interrupts
       -mno-save-mduc-in-interrupts
	   Specifies that interrupt handler functions should preserve the MDUC
	   registers.	This  is  only	necessary if normal code might use the
	   MDUC	registers, for example because it performs multiplication  and
	   division  operations.   The default is to ignore the	MDUC registers
	   as this makes the interrupt handlers	 faster.   The	target	option
	   -mg13  needs	 to be passed for this to work as this feature is only
	   available on	the G13	target (S2 core).   The	 MDUC  registers  will
	   only	be saved if the	interrupt handler performs a multiplication or
	   division operation or it calls another function.

       IBM RS/6000 and PowerPC Options

       These -m	options	are defined for	the IBM	RS/6000	and PowerPC:

       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mpopcntd
       -mno-popcntd
       -mfprnd
       -mno-fprnd
       -mcmpb
       -mno-cmpb
       -mhard-dfp
       -mno-hard-dfp
	   You	use  these options to specify which instructions are available
	   on the processor you	are using.  The	default	value of these options
	   is determined when configuring GCC.	Specifying the	-mcpu=cpu_type
	   overrides the specification of these	options.  We recommend you use
	   the -mcpu=cpu_type option rather than the options listed above.

	   Specifying  -mpowerpc-gpopt	allows GCC to use the optional PowerPC
	   architecture	instructions in	the General Purpose  group,  including
	   floating-point square root.	Specifying -mpowerpc-gfxopt allows GCC
	   to  use  the	 optional  PowerPC  architecture  instructions	in the
	   Graphics group, including floating-point select.

	   The -mmfcrf option allows GCC to generate the move  from  condition
	   register  field instruction implemented on the POWER4 processor and
	   other processors that support the PowerPC V2.01 architecture.   The
	   -mpopcntb  option  allows  GCC to generate the popcount and double-
	   precision FP	reciprocal estimate  instruction  implemented  on  the
	   POWER5  processor  and  other  processors  that support the PowerPC
	   V2.02 architecture.	The -mpopcntd option allows  GCC  to  generate
	   the	popcount  instruction  implemented on the POWER7 processor and
	   other processors that support the PowerPC V2.06 architecture.   The
	   -mfprnd  option  allows  GCC	 to  generate  the FP round to integer
	   instructions	 implemented  on  the  POWER5+	processor  and	 other
	   processors that support the PowerPC V2.03 architecture.  The	-mcmpb
	   option  allows  GCC	to  generate  the  compare  bytes  instruction
	   implemented on the  POWER6  processor  and  other  processors  that
	   support  the	 PowerPC  V2.05	 architecture.	 The -mhard-dfp	option
	   allows GCC to  generate  the	 decimal  floating-point  instructions
	   implemented on some POWER processors.

	   The -mpowerpc64 option allows GCC to	generate the additional	64-bit
	   instructions	 that are found	in the full PowerPC64 architecture and
	   to treat GPRs as 64-bit, doubleword quantities.   GCC  defaults  to
	   -mno-powerpc64.

       -mcpu=cpu_type
	   Set	architecture  type, register usage, and	instruction scheduling
	   parameters  for  machine  type  cpu_type.   Supported  values   for
	   cpu_type  are  401,	403,  405, 405fp, 440, 440fp, 464, 464fp, 476,
	   476fp, 505, 601, 602, 603, 603e, 604, 604e, 620,  630,  740,	 7400,
	   7450,  750,	801,  821,  823,  860,	970, 8540, a2, e300c2, e300c3,
	   e500mc, e500mc64, e5500, e6500, ec603e, G3, G4, G5, titan,  power3,
	   power4,  power5,  power5+, power6, power6x, power7, power8, power9,
	   power10, powerpc, powerpc64,	powerpc64le, rs64, and native.

	   -mcpu=powerpc, -mcpu=powerpc64, and -mcpu=powerpc64le specify  pure
	   32-bit  PowerPC  (either  endian),  64-bit  big  endian PowerPC and
	   64-bit little endian	PowerPC	architecture machine  types,  with  an
	   appropriate,	  generic   processor  model  assumed  for  scheduling
	   purposes.

	   Specifying native as	cpu type detects and selects the  architecture
	   option  that	 corresponds  to  the  host  processor	of  the	system
	   performing the compilation.	-mcpu=native has no effect if GCC does
	   not recognize the processor.

	   The other options specify a	specific  processor.   Code  generated
	   under those options runs best on that processor, and	may not	run at
	   all on others.

	   The	-mcpu  options	automatically  enable or disable the following
	   options:

	   -maltivec  -mfprnd	-mhard-float   -mmfcrf	 -mmultiple  -mpopcntb
	   -mpopcntd   -mpowerpc64  -mpowerpc-gpopt   -mpowerpc-gfxopt -mmulhw
	   -mdlmzb    -mmfpgpr	  -mvsx	  -mcrypto    -mhtm    -mpower8-fusion
	   -mpower8-vector   -mquad-memory   -mquad-memory-atomic   -mfloat128
	   -mfloat128-hardware -mprefixed -mpcrel -mmma	-mrop-protect

	   The particular options set for any particular  CPU  varies  between
	   compiler  versions,	depending  on  what  setting  seems to produce
	   optimal code	for that  CPU;	it  doesn't  necessarily  reflect  the
	   actual  hardware's  capabilities.  If you wish to set an individual
	   option to a particular value, you may specify it  after  the	 -mcpu
	   option, like	-mcpu=970 -mno-altivec.

	   On  AIX,  the  -maltivec and	-mpowerpc64 options are	not enabled or
	   disabled by the -mcpu option	at present because AIX does  not  have
	   full	 support  for  these options.  You may still enable or disable
	   them	individually if	you're sure it'll work in your environment.

       -mtune=cpu_type
	   Set	the  instruction  scheduling  parameters  for	machine	  type
	   cpu_type,  but  do not set the architecture type or register	usage,
	   as -mcpu=cpu_type does.  The	same values for	cpu_type are used  for
	   -mtune  as  for  -mcpu.   If	both are specified, the	code generated
	   uses	 the  architecture  and	 registers  set	 by  -mcpu,  but   the
	   scheduling parameters set by	-mtune.

       -mcmodel=small
	   Generate  PowerPC64 code for	the small model: The TOC is limited to
	   64k.

       -mcmodel=medium
	   Generate PowerPC64 code for the medium model:  The  TOC  and	 other
	   static  data	 may  be  up  to  a  total of 4G in size.  This	is the
	   default for 64-bit Linux.

       -mcmodel=large
	   Generate PowerPC64 code for the large model:	The TOC	may be	up  to
	   4G  in  size.   Other  data	and code is only limited by the	64-bit
	   address space.

       -maltivec
       -mno-altivec
	   Generate code that uses (does not use)  AltiVec  instructions,  and
	   also	 enable	 the  use of built-in functions	that allow more	direct
	   access to the AltiVec instruction set.  You may also	 need  to  set
	   -mabi=altivec   to	adjust	 the  current  ABI  with  AltiVec  ABI
	   enhancements.

	   When	-maltivec is used, the element order  for  AltiVec  intrinsics
	   such	 as  "vec_splat",  "vec_extract", and "vec_insert" match array
	   element order corresponding to the endianness of the	target.	  That
	   is,	element	 zero  identifies  the	leftmost  element  in a	vector
	   register when targeting a big-endian	platform, and  identifies  the
	   rightmost  element  in  a  vector register when targeting a little-
	   endian platform.

       -mvrsave
       -mno-vrsave
	   Generate VRSAVE instructions	when generating	AltiVec	code.

       -msecure-plt
	   Generate code that allows ld	and ld.so  to  build  executables  and
	   shared  libraries  with  non-executable ".plt" and ".got" sections.
	   This	is a PowerPC 32-bit SYSV ABI option.

       -mbss-plt
	   Generate code that uses a BSS ".plt"	section	that ld.so  fills  in,
	   and	requires ".plt"	and ".got" sections that are both writable and
	   executable.	This is	a PowerPC 32-bit SYSV ABI option.

       -misel
       -mno-isel
	   This	 switch	 enables  or   disables	  the	generation   of	  ISEL
	   instructions.

       -mvsx
       -mno-vsx
	   Generate   code  that  uses	(does  not  use)  vector/scalar	 (VSX)
	   instructions, and also enable the use of  built-in  functions  that
	   allow more direct access to the VSX instruction set.

       -mcrypto
       -mno-crypto
	   Enable  the	use  (disable)	of  the	 built-in functions that allow
	   direct access to the	cryptographic instructions that	were added  in
	   version 2.07	of the PowerPC ISA.

       -mhtm
       -mno-htm
	   Enable  (disable)  the  use	of  the	 built-in functions that allow
	   direct  access  to  the   Hardware	Transactional	Memory	 (HTM)
	   instructions	that were added	in version 2.07	of the PowerPC ISA.

       -mpower8-fusion
       -mno-power8-fusion
	   Generate  code  that	keeps (does not	keeps) some integer operations
	   adjacent so that the	instructions can be fused together  on	power8
	   and later processors.

       -mpower8-vector
       -mno-power8-vector
	   Generate  code  that	 uses  (does  not  use)	 the vector and	scalar
	   instructions	that were added	in version 2.07	of  the	 PowerPC  ISA.
	   Also	 enable	 the  use of built-in functions	that allow more	direct
	   access to the vector	instructions.

       -mquad-memory
       -mno-quad-memory
	   Generate code that uses (does not use)  the	non-atomic  quad  word
	   memory  instructions.   The	-mquad-memory  option  requires	use of
	   64-bit mode.

       -mquad-memory-atomic
       -mno-quad-memory-atomic
	   Generate code that uses (does not use) the atomic quad word	memory
	   instructions.   The	-mquad-memory-atomic  option  requires	use of
	   64-bit mode.

       -mfloat128
       -mno-float128
	   Enable/disable the __float128 keyword  for  IEEE  128-bit  floating
	   point  and  use either software emulation for IEEE 128-bit floating
	   point or hardware instructions.

	   The VSX instruction set (-mvsx) must	be enabled  to	use  the  IEEE
	   128-bit floating point support.  The	IEEE 128-bit floating point is
	   only	supported on Linux.

	   The	default	 for  -mfloat128  is  enabled on PowerPC Linux systems
	   using the VSX instruction set, and disabled on other	systems.

	   If  you  use	 the  ISA  3.0	instruction  set  (-mpower9-vector  or
	   -mcpu=power9)  on  a	64-bit system, the IEEE	128-bit	floating point
	   support will	also enable the	generation of  ISA  3.0	 IEEE  128-bit
	   floating  point  instructions.  Otherwise, if you do	not specify to
	   generate ISA	3.0 instructions or you	are  targeting	a  32-bit  big
	   endian  system,  IEEE  128-bit  floating  point  will  be done with
	   software emulation.

       -mfloat128-hardware
       -mno-float128-hardware
	   Enable/disable using	ISA 3.0	hardware instructions to  support  the
	   __float128 data type.

	   The	default	 for  -mfloat128-hardware  is enabled on PowerPC Linux
	   systems using the ISA 3.0 instruction set, and  disabled  on	 other
	   systems.

       -m32
       -m64
	   Generate  code for 32-bit or	64-bit environments of Darwin and SVR4
	   targets (including GNU/Linux).  The 32-bit  environment  sets  int,
	   long	 and  pointer  to  32 bits and generates code that runs	on any
	   PowerPC variant.  The 64-bit	environment sets int to	 32  bits  and
	   long	 and  pointer to 64 bits, and generates	code for PowerPC64, as
	   for -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
	   Modify generation of	the TOC	(Table Of Contents), which is  created
	   for	every  executable  file.  The -mfull-toc option	is selected by
	   default.  In	that case, GCC allocates at least one  TOC  entry  for
	   each	 unique	non-automatic variable reference in your program.  GCC
	   also	places floating-point constants	in  the	 TOC.	However,  only
	   16,384 entries are available	in the TOC.

	   If  you  receive  a	linker	error  message	that  saying  you have
	   overflowed the available TOC	space, you can reduce  the  amount  of
	   TOC space used with the -mno-fp-in-toc and -mno-sum-in-toc options.
	   -mno-fp-in-toc  prevents  GCC from putting floating-point constants
	   in the TOC and -mno-sum-in-toc  forces  GCC	to  generate  code  to
	   calculate  the sum of an address and	a constant at run time instead
	   of putting that sum into the	TOC.  You may specify one or  both  of
	   these options.  Each	causes GCC to produce very slightly slower and
	   larger code at the expense of conserving TOC	space.

	   If you still	run out	of space in the	TOC even when you specify both
	   of  these  options,	specify	 -mminimal-toc	instead.   This	option
	   causes GCC to make only one TOC entry for  every  file.   When  you
	   specify  this  option,  GCC produces	code that is slower and	larger
	   but which uses extremely little TOC space.  You  may	 wish  to  use
	   this	 option	 only  on  files that contain less frequently-executed
	   code.

       -maix64
       -maix32
	   Enable 64-bit AIX ABI  and  calling	convention:  64-bit  pointers,
	   64-bit  "long" type,	and the	infrastructure needed to support them.
	   Specifying -maix64 implies -mpowerpc64, while -maix32 disables  the
	   64-bit ABI and implies -mno-powerpc64.  GCC defaults	to -maix32.

       -mxl-compat
       -mno-xl-compat
	   Produce  code  that	conforms  more	closely	 to  IBM  XL  compiler
	   semantics  when  using  AIX-compatible  ABI.	  Pass	floating-point
	   arguments  to  prototyped  functions	 beyond	the register save area
	   (RSA) on the	stack in addition to argument  FPRs.   Do  not	assume
	   that	 most  significant  double  in	128-bit	 long  double value is
	   properly rounded when comparing values and  converting  to  double.
	   Use XL symbol names for long	double support routines.

	   The	 AIX   calling	convention  was	 extended  but	not  initially
	   documented to handle	an obscure K&R C case of  calling  a  function
	   that	 takes	the address of its arguments with fewer	arguments than
	   declared.  IBM XL compilers access floating-point arguments that do
	   not fit in the RSA from the stack when  a  subroutine  is  compiled
	   without   optimization.    Because  always  storing	floating-point
	   arguments on	the stack  is  inefficient  and	 rarely	 needed,  this
	   option is not enabled by default and	only is	necessary when calling
	   subroutines compiled	by IBM XL compilers without optimization.

       -mpe
	   Support   IBM  RS/6000  SP  Parallel	 Environment  (PE).   Link  an
	   application written to use message  passing	with  special  startup
	   code	 to  enable  the  application to run.  The system must have PE
	   installed in	the  standard  location	 (/usr/lpp/ppe.poe/),  or  the
	   specs  file	must  be overridden with the -specs= option to specify
	   the appropriate directory location.	The Parallel Environment  does
	   not support threads,	so the -mpe option and the -pthread option are
	   incompatible.

       -malign-natural
       -malign-power
	   On  AIX,  32-bit  Darwin,  and 64-bit PowerPC GNU/Linux, the	option
	   -malign-natural  overrides  the  ABI-defined	 alignment  of	larger
	   types,  such	as floating-point doubles, on their natural size-based
	   boundary.  The option -malign-power instructs  GCC  to  follow  the
	   ABI-specified  alignment  rules.   GCC  defaults  to	 the  standard
	   alignment defined in	the ABI.

	   On  64-bit  Darwin,	natural	 alignment   is	  the	default,   and
	   -malign-power is not	supported.

       -msoft-float
       -mhard-float
	   Generate  code that does not	use (uses) the floating-point register
	   set.	 Software floating-point emulation is provided if you use  the
	   -msoft-float	option,	and pass the option to GCC when	linking.

       -mmultiple
       -mno-multiple
	   Generate  code  that	 uses  (does  not  use)	the load multiple word
	   instructions	and  the  store	 multiple  word	 instructions.	 These
	   instructions	 are  generated	 by  default on	POWER systems, and not
	   generated on	PowerPC	systems.  Do not  use  -mmultiple  on  little-
	   endian  PowerPC  systems, since those instructions do not work when
	   the processor is in little-endian mode.  The	exceptions are	PPC740
	   and PPC750 which permit these instructions in little-endian mode.

       -mupdate
       -mno-update
	   Generate   code  that  uses	(does  not  use)  the  load  or	 store
	   instructions	that update the	base register to the  address  of  the
	   calculated  memory  location.   These instructions are generated by
	   default.  If	you use	-mno-update, there is a	small  window  between
	   the	time  that the stack pointer is	updated	and the	address	of the
	   previous frame is stored, which means code  that  walks  the	 stack
	   frame across	interrupts or signals may get corrupted	data.

       -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses
	   Generate  code  that	 tries to avoid	(not avoid) the	use of indexed
	   load	 or  store  instructions.  These  instructions	can  incur   a
	   performance	penalty	 on  Power6  processors	in certain situations,
	   such	as when	 stepping  through  large  arrays  that	 cross	a  16M
	   boundary.   This option is enabled by default when targeting	Power6
	   and disabled	otherwise.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating-point  multiply
	   and	accumulate  instructions.  These instructions are generated by
	   default if hardware floating	point is used.	The  machine-dependent
	   -mfused-madd	 option	 is  now  mapped  to  the  machine-independent
	   -ffp-contract=fast  option,	and  -mno-fused-madd  is   mapped   to
	   -ffp-contract=off.

       -mmulhw
       -mno-mulhw
	   Generate  code  that	uses (does not use) the	half-word multiply and
	   multiply-accumulate instructions on the IBM 405, 440, 464  and  476
	   processors.	 These	instructions  are  generated  by  default when
	   targeting those processors.

       -mdlmzb
       -mno-dlmzb
	   Generate code that uses (does  not  use)  the  string-search	 dlmzb
	   instruction	on  the	 IBM  405,  440, 464 and 476 processors.  This
	   instruction	is  generated  by   default   when   targeting	 those
	   processors.

       -mno-bit-align
       -mbit-align
	   On  System  V.4  and	 embedded  PowerPC  systems  do	not (do) force
	   structures and unions that contain bit-fields to be aligned to  the
	   base	type of	the bit-field.

	   For	example,  by  default  a  structure  containing	 nothing but 8
	   "unsigned" bit-fields of length 1 is	aligned	to a  4-byte  boundary
	   and	has a size of 4	bytes.	By using -mno-bit-align, the structure
	   is aligned to a 1-byte boundary and is 1 byte in size.

       -mno-strict-align
       -mstrict-align
	   On System V.4 and embedded PowerPC systems do not (do) assume  that
	   unaligned memory references are handled by the system.

       -mrelocatable
       -mno-relocatable
	   Generate  code  that	allows (does not allow)	a static executable to
	   be relocated	to a different address at run time.  A simple embedded
	   PowerPC system  loader  should  relocate  the  entire  contents  of
	   ".got2"  and	 4-byte	 locations  listed  in the ".fixup" section, a
	   table of 32-bit addresses generated by this option.	 For  this  to
	   work,   all	 objects   linked   together  must  be	compiled  with
	   -mrelocatable or -mrelocatable-lib.	-mrelocatable code aligns  the
	   stack to an 8-byte boundary.

       -mrelocatable-lib
       -mno-relocatable-lib
	   Like	 -mrelocatable,	-mrelocatable-lib generates a ".fixup" section
	   to allow static executables	to  be	relocated  at  run  time,  but
	   -mrelocatable-lib  does  not	 use  the  smaller  stack alignment of
	   -mrelocatable.  Objects  compiled  with  -mrelocatable-lib  may  be
	   linked   with   objects   compiled  with  any  combination  of  the
	   -mrelocatable options.

       -mno-toc
       -mtoc
	   On System V.4 and embedded PowerPC systems do not (do) assume  that
	   register  2	contains  a  pointer  to a global area pointing	to the
	   addresses used in the program.

       -mlittle
       -mlittle-endian
	   On System V.4 and embedded PowerPC systems  compile	code  for  the
	   processor in	little-endian mode.  The -mlittle-endian option	is the
	   same	as -mlittle.

       -mbig
       -mbig-endian
	   On  System  V.4  and	 embedded PowerPC systems compile code for the
	   processor in	big-endian mode.  The -mbig-endian option is the  same
	   as -mbig.

       -mdynamic-no-pic
	   On  Darwin  and  Mac	 OS  X systems,	compile	code so	that it	is not
	   relocatable,	but that its external references are relocatable.  The
	   resulting  code  is	suitable  for  applications,  but  not	shared
	   libraries.

       -msingle-pic-base
	   Treat  the  register	 used  for PIC addressing as read-only,	rather
	   than	loading	it in the prologue for	each  function.	  The  runtime
	   system  is  responsible  for	 initializing  this  register  with an
	   appropriate value before execution begins.

       -mprioritize-restricted-insns=priority
	   This	option controls	the priority that is assigned to dispatch-slot
	   restricted instructions during the  second  scheduling  pass.   The
	   argument priority takes the value 0,	1, or 2	to assign no, highest,
	   or	second-highest	 (respectively)	  priority   to	 dispatch-slot
	   restricted instructions.

       -msched-costly-dep=dependence_type
	   This	option controls	which dependences are considered costly	by the
	   target during instruction scheduling.  The argument dependence_type
	   takes one of	the following values:

	   no  No dependence is	costly.

	   all All dependences are costly.

	   true_store_to_load
	       A true dependence from store to load is costly.

	   store_to_load
	       Any dependence from store to load is costly.

	   number
	       Any dependence for which	the latency is greater than  or	 equal
	       to number is costly.

       -minsert-sched-nops=scheme
	   This	 option	controls which NOP insertion scheme is used during the
	   second scheduling pass.  The	 argument  scheme  takes  one  of  the
	   following values:

	   no  Don't insert NOPs.

	   pad Pad  with  NOPs any dispatch group that has vacant issue	slots,
	       according to the	scheduler's grouping.

	   regroup_exact
	       Insert NOPs to  force  costly  dependent	 insns	into  separate
	       groups.	Insert exactly as many NOPs as needed to force an insn
	       to a new	group, according to the	estimated processor grouping.

	   number
	       Insert  NOPs  to	 force	costly	dependent  insns into separate
	       groups.	Insert number NOPs to force an insn to a new group.

       -mcall-sysv
	   On System V.4 and  embedded	PowerPC	 systems  compile  code	 using
	   calling  conventions	 that  adhere  to  the March 1995 draft	of the
	   System  V   Application   Binary   Interface,   PowerPC   processor
	   supplement.	 This  is  the default unless you configured GCC using
	   powerpc-*-eabiaix.

       -mcall-sysv-eabi
       -mcall-eabi
	   Specify both	-mcall-sysv and	-meabi options.

       -mcall-sysv-noeabi
	   Specify both	-mcall-sysv and	-mno-eabi options.

       -mcall-aixdesc
	   On System V.4 and embedded PowerPC systems compile code for the AIX
	   operating system.

       -mcall-linux
	   On System V.4 and embedded PowerPC systems  compile	code  for  the
	   Linux-based GNU system.

       -mcall-freebsd
	   On  System  V.4  and	 embedded PowerPC systems compile code for the
	   FreeBSD operating system.

       -mcall-netbsd
	   On System V.4 and embedded PowerPC systems  compile	code  for  the
	   NetBSD operating system.

       -mcall-openbsd
	   On  System  V.4  and	 embedded PowerPC systems compile code for the
	   OpenBSD operating system.

       -mtraceback=traceback_type
	   Select the type of traceback	table. Valid values for	traceback_type
	   are full, part, and no.

       -maix-struct-return
	   Return all structures in memory (as specified by the	AIX ABI).

       -msvr4-struct-return
	   Return structures smaller than 8 bytes in registers	(as  specified
	   by the SVR4 ABI).

       -mabi=abi-type
	   Extend  the current ABI with	a particular extension,	or remove such
	   extension.  Valid values are: altivec,  no-altivec,	ibmlongdouble,
	   ieeelongdouble, elfv1, elfv2, and for AIX: vec-extabi, vec-default.

       -mabi=ibmlongdouble
	   Change  the	current	ABI to use IBM extended-precision long double.
	   This	is not likely to work if your system defaults  to  using  IEEE
	   extended-precision long double.  If you change the long double type
	   from	 IEEE  extended-precision,  the	 compiler will issue a warning
	   unless you use the -Wno-psabi option.   Requires  -mlong-double-128
	   to be enabled.

       -mabi=ieeelongdouble
	   Change  the current ABI to use IEEE extended-precision long double.
	   This	is not likely to work if your system  defaults	to  using  IBM
	   extended-precision long double.  If you change the long double type
	   from	 IBM  extended-precision,  the	compiler  will issue a warning
	   unless you use the -Wno-psabi option.   Requires  -mlong-double-128
	   to be enabled.

       -mabi=elfv1
	   Change  the	current	ABI to use the ELFv1 ABI.  This	is the default
	   ABI for big-endian PowerPC 64-bit Linux.   Overriding  the  default
	   ABI	requires  special  system  support  and	 is  likely to fail in
	   spectacular ways.

       -mabi=elfv2
	   Change the current ABI to use the ELFv2 ABI.	 This is  the  default
	   ABI for little-endian PowerPC 64-bit	Linux.	Overriding the default
	   ABI	requires  special  system  support  and	 is  likely to fail in
	   spectacular ways.

       -mgnu-attribute
       -mno-gnu-attribute
	   Emit	.gnu_attribute assembly	directives to set tag/value pairs in a
	   .gnu.attributes section that	specify	 ABI  variations  in  function
	   parameters or return	values.

       -mprototype
       -mno-prototype
	   On System V.4 and embedded PowerPC systems assume that all calls to
	   variable  argument  functions  are properly prototyped.  Otherwise,
	   the compiler	must insert an instruction before every	non-prototyped
	   call	to set or clear	bit 6 of the condition code register ("CR") to
	   indicate whether floating-point values are passed in	the  floating-
	   point  registers  in	 case  the  function takes variable arguments.
	   With	 -mprototype,  only  calls  to	prototyped  variable  argument
	   functions set or clear the bit.

       -msim
	   On  embedded	 PowerPC  systems,  assume  that the startup module is
	   called sim-crt0.o and that the standard C  libraries	 are  libsim.a
	   and	 libc.a.    This   is	the   default	for  powerpc-*-eabisim
	   configurations.

       -mmvme
	   On embedded PowerPC systems,	assume	that  the  startup  module  is
	   called  crt0.o  and	the  standard  C  libraries  are libmvme.a and
	   libc.a.

       -mads
	   On embedded PowerPC systems,	assume	that  the  startup  module  is
	   called crt0.o and the standard C libraries are libads.a and libc.a.

       -myellowknife
	   On  embedded	 PowerPC  systems,  assume  that the startup module is
	   called crt0.o and the standard C libraries are libyk.a and libc.a.

       -mvxworks
	   On System V.4 and embedded PowerPC systems, specify	that  you  are
	   compiling for a VxWorks system.

       -memb
	   On embedded PowerPC systems,	set the	"PPC_EMB" bit in the ELF flags
	   header to indicate that eabi	extended relocations are used.

       -meabi
       -mno-eabi
	   On  System  V.4  and	embedded PowerPC systems do (do	not) adhere to
	   the Embedded	Applications Binary Interface (EABI), which is	a  set
	   of  modifications  to  the  System  V.4  specifications.  Selecting
	   -meabi means	that the stack is aligned to  an  8-byte  boundary,  a
	   function  "__eabi"  is  called  from	 "main"	 to  set  up  the EABI
	   environment,	and the	-msdata	option can use both "r2" and "r13"  to
	   point  to two separate small	data areas.  Selecting -mno-eabi means
	   that	 the  stack  is	 aligned  to  a	 16-byte  boundary,  no	  EABI
	   initialization  function  is	 called	 from  "main", and the -msdata
	   option only uses "r13" to point to a	single small data  area.   The
	   -meabi  option  is on by default if you configured GCC using	one of
	   the powerpc*-*-eabi*	options.

       -msdata=eabi
	   On System V.4 and embedded PowerPC systems, put  small  initialized
	   "const"  global  and	static data in the ".sdata2" section, which is
	   pointed to by register "r2".	  Put  small  initialized  non-"const"
	   global and static data in the ".sdata" section, which is pointed to
	   by  register	"r13".	Put small uninitialized	global and static data
	   in the ".sbss" section, which is adjacent to	the ".sdata"  section.
	   The	-msdata=eabi  option  is  incompatible	with the -mrelocatable
	   option.  The	-msdata=eabi option also sets the -memb	option.

       -msdata=sysv
	   On System V.4 and embedded PowerPC systems, put  small  global  and
	   static  data	 in  the  ".sdata"  section,  which  is	 pointed to by
	   register "r13".  Put	small uninitialized global and static data  in
	   the	".sbss"	 section,  which  is adjacent to the ".sdata" section.
	   The -msdata=sysv option  is	incompatible  with  the	 -mrelocatable
	   option.

       -msdata=default
       -msdata
	   On  System  V.4  and	 embedded  PowerPC systems, if -meabi is used,
	   compile code	the same as -msdata=eabi, otherwise compile  code  the
	   same	as -msdata=sysv.

       -msdata=data
	   On  System  V.4 and embedded	PowerPC	systems, put small global data
	   in the ".sdata" section.  Put small uninitialized  global  data  in
	   the	".sbss"	 section.   Do not use register	"r13" to address small
	   data	however.  This is the default behavior	unless	other  -msdata
	   options are used.

       -msdata=none
       -mno-sdata
	   On  embedded	PowerPC	systems, put all initialized global and	static
	   data	in the ".data" section,	and  all  uninitialized	 data  in  the
	   ".bss" section.

       -mreadonly-in-sdata
	   Put read-only objects in the	".sdata" section as well.  This	is the
	   default.

       -mblock-move-inline-limit=num
	   Inline  all	block  moves  (such  as	calls to "memcpy" or structure
	   copies) less	than or	equal to num bytes.  The minimum value for num
	   is 32 bytes on 32-bit targets and 64	bytes on 64-bit	targets.   The
	   default value is target-specific.

       -mblock-compare-inline-limit=num
	   Generate  non-looping  inline  code for all block compares (such as
	   calls to "memcmp" or	structure compares) less than or equal to  num
	   bytes.  If  num  is	0, all inline expansion	(non-loop and loop) of
	   block compare is disabled. The default value	is target-specific.

       -mblock-compare-inline-loop-limit=num
	   Generate an inline expansion	using loop code	for all	block compares
	   that	are less than or equal to num  bytes,  but  greater  than  the
	   limit  for  non-loop	 inline	 block compare expansion. If the block
	   length is not constant, at most num bytes will be  compared	before
	   "memcmp"  is	 called	 to  compare  the  remainder of	the block. The
	   default value is target-specific.

       -mstring-compare-inline-limit=num
	   Compare at  most  num  string  bytes	 with  inline  code.   If  the
	   difference  or  end of string is not	found at the end of the	inline
	   compare a call to "strcmp" or "strncmp" will	take care of the  rest
	   of the comparison. The default is 64	bytes.

       -G num
	   On  embedded	PowerPC	systems, put global and	static items less than
	   or equal to num bytes into the small	data or	BSS  sections  instead
	   of  the  normal data	or BSS section.	 By default, num is 8.	The -G
	   num switch is also passed to	the linker.   All  modules  should  be
	   compiled with the same -G num value.

       -mregnames
       -mno-regnames
	   On  System  V.4  and	 embedded  PowerPC  systems  do	 (do not) emit
	   register names in  the  assembly  language  output  using  symbolic
	   forms.

       -mlongcall
       -mno-longcall
	   By  default assume that all calls are far away so that a longer and
	   more	expensive calling sequence is required.	 This is required  for
	   calls farther than 32 megabytes (33,554,432 bytes) from the current
	   location.  A	short call is generated	if the compiler	knows the call
	   cannot  be  that  far  away.	 This setting can be overridden	by the
	   "shortcall" function	attribute, or by "#pragma longcall(0)".

	   Some	linkers	 are  capable  of  detecting  out-of-range  calls  and
	   generating  glue code on the	fly.  On these systems,	long calls are
	   unnecessary and generate slower code.  As of	this writing, the  AIX
	   linker  can	do  this, as can the GNU linker	for PowerPC/64.	 It is
	   planned to add this feature to the GNU linker  for  32-bit  PowerPC
	   systems as well.

	   On  PowerPC64  ELFv2	 and  32-bit  PowerPC  systems	with newer GNU
	   linkers, GCC	can generate long  calls  using	 an  inline  PLT  call
	   sequence  (see  -mpltseq).	PowerPC	 with  -mbss-plt and PowerPC64
	   ELFv1 (big-endian) do not support inline PLT	calls.

	   On Darwin/PPC systems, "#pragma longcall" generates	"jbsr  callee,
	   L42",  plus	a branch island	(glue code).  The two target addresses
	   represent the callee	and the	branch island.	The Darwin/PPC	linker
	   prefers  the	 first	address	and generates a	"bl callee" if the PPC
	   "bl"	instruction reaches the	callee directly; otherwise, the	linker
	   generates "bl L42" to call the branch island.  The branch island is
	   appended to the body	of the calling function; it computes the  full
	   32-bit address of the callee	and jumps to it.

	   On  Mach-O  (Darwin)	systems, this option directs the compiler emit
	   to the glue for every direct	call, and the  Darwin  linker  decides
	   whether to use or discard it.

	   In  the future, GCC may ignore all longcall specifications when the
	   linker is known to generate glue.

       -mpltseq
       -mno-pltseq
	   Implement (do not implement)	 -fno-plt  and	long  calls  using  an
	   inline  PLT call sequence that supports lazy	linking	and long calls
	   to functions	in dlopen'd shared libraries.  Inline  PLT  calls  are
	   only	 supported  on PowerPC64 ELFv2 and 32-bit PowerPC systems with
	   newer GNU linkers, and are enabled by default  if  the  support  is
	   detected  when configuring GCC, and,	in the case of 32-bit PowerPC,
	   if GCC is configured	with --enable-secureplt.   -mpltseq  code  and
	   -mbss-plt  32-bit  PowerPC  relocatable  objects  may not be	linked
	   together.

       -mtls-markers
       -mno-tls-markers
	   Mark	(do not	mark) calls  to	 "__tls_get_addr"  with	 a  relocation
	   specifying the function argument.  The relocation allows the	linker
	   to	reliably   associate   function	  call	 with  argument	 setup
	   instructions	for TLS	optimization, which  in	 turn  allows  GCC  to
	   better schedule the sequence.

       -mrecip
       -mno-recip
	   This	 option	 enables use of	the reciprocal estimate	and reciprocal
	   square root estimate	instructions  with  additional	Newton-Raphson
	   steps  to  increase	precision  instead of doing a divide or	square
	   root	and divide for floating-point arguments.  You should  use  the
	   -ffast-math	  option    when    using   -mrecip   (or   at	 least
	   -funsafe-math-optimizations,	-ffinite-math-only,  -freciprocal-math
	   and	-fno-trapping-math).   Note  that  while the throughput	of the
	   sequence is generally  higher  than	the  throughput	 of  the  non-
	   reciprocal  instruction,  the  precision  of	 the  sequence	can be
	   decreased  by  up  to  2  ulp  (i.e.	 the  inverse  of  1.0	equals
	   0.99999994) for reciprocal square roots.

       -mrecip=opt
	   This	 option	controls which reciprocal estimate instructions	may be
	   used.  opt is a comma-separated  list  of  options,	which  may  be
	   preceded by a "!" to	invert the option:

	   all Enable all estimate instructions.

	   default
	       Enable the default instructions,	equivalent to -mrecip.

	   none
	       Disable all estimate instructions, equivalent to	-mno-recip.

	   div Enable  the  reciprocal	approximation  instructions  for  both
	       single and double precision.

	   divf
	       Enable	the    single-precision	   reciprocal	 approximation
	       instructions.

	   divd
	       Enable	 the	double-precision    reciprocal	 approximation
	       instructions.

	   rsqrt
	       Enable the reciprocal square  root  approximation  instructions
	       for both	single and double precision.

	   rsqrtf
	       Enable	 the	single-precision    reciprocal	 square	  root
	       approximation instructions.

	   rsqrtd
	       Enable	the   double-precision	  reciprocal	square	  root
	       approximation instructions.

	   So,	for example, -mrecip=all,!rsqrtd enables all of	the reciprocal
	   estimate instructions, except for the "FRSQRTE", "XSRSQRTEDP",  and
	   "XVRSQRTEDP"	  instructions	 which	 handle	 the  double-precision
	   reciprocal square root calculations.

       -mrecip-precision
       -mno-recip-precision
	   Assume (do not assume) that the  reciprocal	estimate  instructions
	   provide  higher-precision estimates than is mandated	by the PowerPC
	   ABI.	  Selecting   -mcpu=power6,   -mcpu=power7   or	  -mcpu=power8
	   automatically   selects  -mrecip-precision.	 The  double-precision
	   square root estimate	instructions are not generated by  default  on
	   low-precision  machines, since they do not provide an estimate that
	   converges after three steps.

       -mveclibabi=type
	   Specifies the ABI type to use for vectorizing intrinsics  using  an
	   external  library.	The  only  type	 supported at present is mass,
	   which specifies to use IBM's	 Mathematical  Acceleration  Subsystem
	   (MASS)   libraries	for   vectorizing  intrinsics  using  external
	   libraries.	GCC  currently	emits  calls  to  "acosd2",  "acosf4",
	   "acoshd2",  "acoshf4",  "asind2",  "asinf4",	 "asinhd2", "asinhf4",
	   "atan2d2", "atan2f4",  "atand2",  "atanf4",	"atanhd2",  "atanhf4",
	   "cbrtd2", "cbrtf4", "cosd2",	"cosf4", "coshd2", "coshf4", "erfcd2",
	   "erfcf4",  "erfd2",	"erff4", "exp2d2", "exp2f4", "expd2", "expf4",
	   "expm1d2", "expm1f4", "hypotd2", "hypotf4", "lgammad2", "lgammaf4",
	   "log10d2", "log10f4",  "log1pd2",  "log1pf4",  "log2d2",  "log2f4",
	   "logd2",  "logf4",  "powd2",	 "powf4",  "sind2", "sinf4", "sinhd2",
	   "sinhf4",  "sqrtd2",	 "sqrtf4",  "tand2",  "tanf4",	"tanhd2",  and
	   "tanhf4"  when  generating  code for	power7.	 Both -ftree-vectorize
	   and -funsafe-math-optimizations must	also  be  enabled.   The  MASS
	   libraries must be specified at link time.

       -mfriz
       -mno-friz
	   Generate   (do  not	generate)  the	"friz"	instruction  when  the
	   -funsafe-math-optimizations option is used to optimize rounding  of
	   floating-point values to 64-bit integer and back to floating	point.
	   The	"friz"	instruction  does  not	return	the  same value	if the
	   floating-point number is too	large to fit in	an integer.

       -mpointers-to-nested-functions
       -mno-pointers-to-nested-functions
	   Generate (do	not  generate)	code  to  load	up  the	 static	 chain
	   register  ("r11")  when calling through a pointer on	AIX and	64-bit
	   Linux  systems  where  a  function  pointer	points	to  a	3-word
	   descriptor  giving  the function address, TOC value to be loaded in
	   register "r2", and static chain value  to  be  loaded  in  register
	   "r11".   The	 -mpointers-to-nested-functions	is on by default.  You
	   cannot call through pointers	to nested  functions  or  pointers  to
	   functions  compiled in other	languages that use the static chain if
	   you use -mno-pointers-to-nested-functions.

       -msave-toc-indirect
       -mno-save-toc-indirect
	   Generate (do	not generate) code  to	save  the  TOC	value  in  the
	   reserved  stack  location  in the function prologue if the function
	   calls through a pointer on AIX and 64-bit Linux  systems.   If  the
	   TOC value is	not saved in the prologue, it is saved just before the
	   call	through	the pointer.  The -mno-save-toc-indirect option	is the
	   default.

       -mcompat-align-parm
       -mno-compat-align-parm
	   Generate (do	not generate) code to pass structure parameters	with a
	   maximum alignment of	64 bits, for compatibility with	older versions
	   of GCC.

	   Older  versions of GCC (prior to 4.9.0) incorrectly did not align a
	   structure parameter on  a  128-bit  boundary	 when  that  structure
	   contained  a	member requiring 128-bit alignment.  This is corrected
	   in more recent versions  of	GCC.   This  option  may  be  used  to
	   generate code that is compatible with functions compiled with older
	   versions of GCC.

	   The -mno-compat-align-parm option is	the default.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
       -mstack-protector-guard-symbol=symbol
	   Generate  stack  protection	code using canary at guard.  Supported
	   locations are global	for global canary or tls for per-thread	canary
	   in the TLS block (the default with GNU libc version 2.4 or later).

	   With	the latter choice the options  -mstack-protector-guard-reg=reg
	   and -mstack-protector-guard-offset=offset furthermore specify which
	   register  to	 use as	base register for reading the canary, and from
	   what	offset from that base register.	The default for	 those	is  as
	   specified	       in	   the		relevant	  ABI.
	   -mstack-protector-guard-symbol=symbol overrides the offset  with  a
	   symbol reference to a canary	in the TLS block.

       -mpcrel
       -mno-pcrel
	   Generate  (do  not  generate)  pc-relative addressing.  The -mpcrel
	   option requires that	the medium code	 model	(-mcmodel=medium)  and
	   prefixed addressing (-mprefixed) options are	enabled.

       -mprefixed
       -mno-prefixed
	   Generate (do	not generate) addressing modes using prefixed load and
	   store instructions.	The -mprefixed option requires that the	option
	   -mcpu=power10 (or later) is enabled.

       -mmma
       -mno-mma
	   Generate  (do  not generate)	the MMA	instructions.  The -mma	option
	   requires that the option -mcpu=power10 (or later) is	enabled.

       -mrop-protect
       -mno-rop-protect
	   Generate (do	not generate) ROP  protection  instructions  when  the
	   target processor supports them.  Currently this option disables the
	   shrink-wrap optimization (-fshrink-wrap).

       -mprivileged
       -mno-privileged
	   Generate (do	not generate) code that	will run in privileged state.

       -mblock-ops-unaligned-vsx
       -mno-block-ops-unaligned-vsx
	   Generate  (do  not  generate)  unaligned  vsx  loads	and stores for
	   inline expansion of "memcpy"	and "memmove".

       RX Options

       These command-line options are defined for RX targets:

       -m64bit-doubles
       -m32bit-doubles
	   Make	the "double" data type be 64 bits (-m64bit-doubles) or 32 bits
	   (-m32bit-doubles) in	size.  The default is  -m32bit-doubles.	  Note
	   RX  floating-point  hardware	 only works on 32-bit values, which is
	   why the default is -m32bit-doubles.

       -fpu
       -nofpu
	   Enables (-fpu) or disables (-nofpu) the use	of  RX	floating-point
	   hardware.  The default is enabled for the RX600 series and disabled
	   for the RX200 series.

	   Floating-point instructions are only	generated for 32-bit floating-
	   point  values, however, so the FPU hardware is not used for doubles
	   if the -m64bit-doubles option is used.

	   Note	If the -fpu option is enabled then -funsafe-math-optimizations
	   is  also  enabled  automatically.   This  is	 because  the  RX  FPU
	   instructions	are themselves unsafe.

       -mcpu=name
	   Selects  the	 type of RX CPU	to be targeted.	 Currently three types
	   are supported, the generic RX600 and	RX200 series hardware and  the
	   specific RX610 CPU.	The default is RX600.

	   The	only difference	between	RX600 and RX610	is that	the RX610 does
	   not support the "MVTIPL" instruction.

	   The RX200 series does not have a hardware floating-point  unit  and
	   so -nofpu is	enabled	by default when	this type is selected.

       -mbig-endian-data
       -mlittle-endian-data
	   Store data (but not code) in	the big-endian format.	The default is
	   -mlittle-endian-data,  i.e.	to  store  data	 in  the little-endian
	   format.

       -msmall-data-limit=N
	   Specifies the maximum size in bytes of global and static  variables
	   which can be	placed into the	small data area.  Using	the small data
	   area	 can  lead to smaller and faster code, but the size of area is
	   limited and it is up	to the programmer to ensure that the area does
	   not overflow.  Also when the	small data area	is  used  one  of  the
	   RX's	registers (usually "r13") is reserved for use pointing to this
	   area,  so  it is no longer available	for use	by the compiler.  This
	   could result	in slower and/or larger	code if	variables  are	pushed
	   onto	the stack instead of being held	in this	register.

	   Note,  common  variables (variables that have not been initialized)
	   and constants are not placed	into the small data area as  they  are
	   assigned to other sections in the output executable.

	   The default value is	zero, which disables this feature.  Note, this
	   feature  is	not enabled by default with higher optimization	levels
	   (-O2	 etc)  because	of  the	 potentially  detrimental  effects  of
	   reserving a register.  It is	up to the programmer to	experiment and
	   discover  whether this feature is of	benefit	to their program.  See
	   the description of the -mpid	option for a description  of  how  the
	   actual register to hold the small data area pointer is chosen.

       -msim
       -mno-sim
	   Use	the  simulator	runtime.   The	default	is to use the libgloss
	   board-specific runtime.

       -mas100-syntax
       -mno-as100-syntax
	   When	generating assembler output use	a syntax  that	is  compatible
	   with	Renesas's AS100	assembler.  This syntax	can also be handled by
	   the	GAS  assembler,	 but  it  has  some  restrictions so it	is not
	   generated by	default.

       -mmax-constant-size=N
	   Specifies the maximum size, in bytes, of a  constant	 that  can  be
	   used	  as  an  operand  in  a  RX  instruction.   Although  the  RX
	   instruction set does	allow constants	of up to 4 bytes in length  to
	   be  used  in	 instructions,	a  longer  value  equates  to a	longer
	   instruction.	 Thus in some circumstances it can  be	beneficial  to
	   restrict  the  size	of  constants  that  are used in instructions.
	   Constants that are too big are instead placed into a	constant  pool
	   and referenced via register indirection.

	   The	value N	can be between 0 and 4.	 A value of 0 (the default) or
	   4 means that	constants of any size are allowed.

       -mrelax
	   Enable linker relaxation.  Linker relaxation	is a  process  whereby
	   the	linker	attempts  to  reduce  the size of a program by finding
	   shorter versions of various instructions.  Disabled by default.

       -mint-register=N
	   Specify the number of  registers  to	 reserve  for  fast  interrupt
	   handler functions.  The value N can be between 0 and	4.  A value of
	   1  means  that  register "r13" is reserved for the exclusive	use of
	   fast	interrupt handlers.  A value of	2 reserves "r13" and "r12".  A
	   value of 3 reserves "r13", "r12"  and  "r11",  and  a  value	 of  4
	   reserves  "r13" through "r10".  A value of 0, the default, does not
	   reserve any registers.

       -msave-acc-in-interrupts
	   Specifies that interrupt  handler  functions	 should	 preserve  the
	   accumulator	register.  This	is only	necessary if normal code might
	   use the accumulator	register,  for	example	 because  it  performs
	   64-bit  multiplications.   The default is to	ignore the accumulator
	   as this makes the interrupt handlers	faster.

       -mpid
       -mno-pid
	   Enables the generation of position independent data.	 When  enabled
	   any	access	to  constant  data  is	done via an offset from	a base
	   address held	in a register.	This allows the	location  of  constant
	   data	 to be determined at run time without requiring	the executable
	   to be relocated, which is a benefit to embedded  applications  with
	   tight  memory  constraints.	 Data  that  can  be  modified	is not
	   affected by this option.

	   Note, using this feature reserves a register,  usually  "r13",  for
	   the	constant  data base address.  This can result in slower	and/or
	   larger code,	especially in complicated functions.

	   The actual register chosen to hold the constant data	 base  address
	   depends    upon   whether   the   -msmall-data-limit	  and/or   the
	   -mint-register command-line options	are  enabled.	Starting  with
	   register  "r13"  and	 proceeding downwards, registers are allocated
	   first to satisfy the	requirements of	-mint-register,	then -mpid and
	   finally -msmall-data-limit.	Thus it	is possible for	the small data
	   area	register to be "r8" if both  -mint-register=4  and  -mpid  are
	   specified on	the command line.

	   By  default	this  feature  is  not	enabled.   The	default	can be
	   restored via	the -mno-pid command-line option.

       -mno-warn-multiple-fast-interrupts
       -mwarn-multiple-fast-interrupts
	   Prevents GCC	from issuing a warning message if it finds  more  than
	   one	fast  interrupt	 handler  when	it  is	compiling a file.  The
	   default is to issue a warning for each extra	fast interrupt handler
	   found, as the RX only supports one such interrupt.

       -mallow-string-insns
       -mno-allow-string-insns
	   Enables or disables the use of the string manipulation instructions
	   "SMOVF", "SCMPU", "SMOVB", "SMOVU", "SUNTIL"	"SWHILE" and also  the
	   "RMPA" instruction.	These instructions may prefetch	data, which is
	   not	safe  to do if accessing an I/O	register.  (See	section	12.2.7
	   of the RX62N	Group User's Manual for	more information).

	   The default is to allow these instructions, but it is not  possible
	   for	GCC  to	 reliably  detect  all	circumstances  where  a	string
	   instruction might be	used to	access an I/O register,	so  their  use
	   cannot  be  disabled	automatically.	Instead	it is reliant upon the
	   programmer to  use  the  -mno-allow-string-insns  option  if	 their
	   program accesses I/O	space.

	   When	 the  instructions  are	enabled	GCC defines the	C preprocessor
	   symbol "__RX_ALLOW_STRING_INSNS__", otherwise it defines the	symbol
	   "__RX_DISALLOW_STRING_INSNS__".

       -mjsr
       -mno-jsr
	   Use only (or	not only)  "JSR"  instructions	to  access  functions.
	   This	 option	 can be	used when code size exceeds the	range of "BSR"
	   instructions.  Note that -mno-jsr does not mean to  not  use	 "JSR"
	   but instead means that any type of branch may be used.

       Note:  The  generic  GCC	 command-line  option  -ffixed-reg has special
       significance to the RX port when	used  with  the	 "interrupt"  function
       attribute.   This  attribute  indicates	a function intended to process
       fast interrupts.	 GCC ensures that it only uses	the  registers	"r10",
       "r11",  "r12" and/or "r13" and only provided that the normal use	of the
       corresponding registers have been restricted  via  the  -ffixed-reg  or
       -mint-register command-line options.

       S/390 and zSeries Options

       These   are   the   -m  options	defined	 for  the  S/390  and  zSeries
       architecture.

       -mhard-float
       -msoft-float
	   Use (do not	use)  the  hardware  floating-point  instructions  and
	   registers  for  floating-point  operations.	 When  -msoft-float is
	   specified, functions	in libgcc.a are	used to	perform	floating-point
	   operations.	When -mhard-float is specified,	the compiler generates
	   IEEE	floating-point instructions.  This is the default.

       -mhard-dfp
       -mno-hard-dfp
	   Use (do not use) the	hardware  decimal-floating-point  instructions
	   for	 decimal-floating-point	 operations.   When  -mno-hard-dfp  is
	   specified, functions	in  libgcc.a  are  used	 to  perform  decimal-
	   floating-point  operations.	 When  -mhard-dfp  is  specified,  the
	   compiler generates  decimal-floating-point  hardware	 instructions.
	   This	is the default for -march=z9-ec	or higher.

       -mlong-double-64
       -mlong-double-128
	   These switches control the size of "long double" type. A size of 64
	   bits	 makes the "long double" type equivalent to the	"double" type.
	   This	is the default.

       -mbackchain
       -mno-backchain
	   Store (do not store)	the address of the caller's frame as backchain
	   pointer into	the callee's stack frame.  A backchain may  be	needed
	   to  allow  debugging	 using tools that do not understand DWARF call
	   frame  information.	 When  -mno-packed-stack  is  in  effect,  the
	   backchain  pointer is stored	at the bottom of the stack frame; when
	   -mpacked-stack is in	effect,	 the  backchain	 is  placed  into  the
	   topmost word	of the 96/160 byte register save area.

	   In  general,	code compiled with -mbackchain is call-compatible with
	   code	compiled with -mno-backchain; however, use  of	the  backchain
	   for	debugging  purposes  usually requires that the whole binary is
	   built with -mbackchain.  Note that the combination of  -mbackchain,
	   -mpacked-stack  and	-mhard-float  is  not  supported.  In order to
	   build a linux kernel	use -msoft-float.

	   The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
	   Use (do not use) the	packed stack layout.   When  -mno-packed-stack
	   is  specified,  the compiler	uses the all fields of the 96/160 byte
	   register save area only for their default  purpose;	unused	fields
	   still  take	up  stack  space.   When  -mpacked-stack is specified,
	   register save slots are densely packed at the top of	 the  register
	   save	 area; unused space is reused for other	purposes, allowing for
	   more	efficient use of the available	stack  space.	However,  when
	   -mbackchain is also in effect, the topmost word of the save area is
	   always used to store	the backchain, and the return address register
	   is always saved two words below the backchain.

	   As  long  as	 the stack frame backchain is not used,	code generated
	   with	-mpacked-stack is call-compatible  with	 code  generated  with
	   -mno-packed-stack.  Note that some non-FSF releases of GCC 2.95 for
	   S/390 or zSeries generated code that	uses the stack frame backchain
	   at  run  time,  not	just for debugging purposes.  Such code	is not
	   call-compatible with	code compiled with -mpacked-stack.  Also, note
	   that	  the	combination   of   -mbackchain,	  -mpacked-stack   and
	   -mhard-float	 is  not  supported.  In order to build	a linux	kernel
	   use -msoft-float.

	   The default is to not use the packed	stack layout.

       -msmall-exec
       -mno-small-exec
	   Generate (or	do not generate) code using the	"bras" instruction  to
	   do  subroutine  calls.   This  only	works  reliably	 if  the total
	   executable size does	not exceed 64k.	 The default  is  to  use  the
	   "basr" instruction instead, which does not have this	limitation.

       -m64
       -m31
	   When	 -m31  is  specified, generate code compliant to the GNU/Linux
	   for S/390 ABI.  When	-m64 is	specified, generate code compliant  to
	   the	GNU/Linux  for	zSeries	ABI.  This allows GCC in particular to
	   generate 64-bit instructions.  For the s390 targets,	the default is
	   -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
	   When	-mzarch	is specified, generate	code  using  the  instructions
	   available  on  z/Architecture.   When  -mesa	is specified, generate
	   code	using the instructions available on ESA/390.  Note that	 -mesa
	   is  not  possible with -m64.	 When generating code compliant	to the
	   GNU/Linux for S/390 ABI, the	default	 is  -mesa.   When  generating
	   code	 compliant  to	the  GNU/Linux for zSeries ABI,	the default is
	   -mzarch.

       -mhtm
       -mno-htm
	   The	-mhtm  option  enables	a  set	of  builtins  making  use   of
	   instructions	 available  with  the transactional execution facility
	   introduced with the IBM zEnterprise EC12 machine  generation	 S/390
	   System  z  Built-in	Functions.   -mhtm  is enabled by default when
	   using -march=zEC12.

       -mvx
       -mno-vx
	   When	-mvx  is  specified,  generate	code  using  the  instructions
	   available  with  the	 vector	extension facility introduced with the
	   IBM z13 machine generation.	This option changes the	ABI  for  some
	   vector   type   values   with   regard  to  alignment  and  calling
	   conventions.	 In case vector	type values are	being used in an  ABI-
	   relevant context a GAS .gnu_attribute command will be added to mark
	   the resulting binary	with the ABI used.  -mvx is enabled by default
	   when	using -march=z13.

       -mzvector
       -mno-zvector
	   The	 -mzvector  option  enables  vector  language  extensions  and
	   builtins using instructions available  with	the  vector  extension
	   facility  introduced	 with  the  IBM	 z13 machine generation.  This
	   option adds support for vector to be	used as	a  keyword  to	define
	   vector type variables and arguments.	 vector	is only	available when
	   GNU	 extensions  are  enabled.   It	 will  not  be	expanded  when
	   requesting strict  standard	compliance  e.g.  with	-std=c99.   In
	   addition  to	 the GCC low-level builtins -mzvector enables a	set of
	   builtins added for compatibility with AltiVec-style implementations
	   like	Power and Cell.	 In order to make use of  these	 builtins  the
	   header  file	 vecintrin.h  needs  to	 be  included.	 -mzvector  is
	   disabled by default.

       -mmvcle
       -mno-mvcle
	   Generate (or	do not generate) code using the	"mvcle"	instruction to
	   perform block moves.	 When -mno-mvcle is  specified,	 use  a	 "mvc"
	   loop	instead.  This is the default unless optimizing	for size.

       -mdebug
       -mno-debug
	   Print   (or	 do  not  print)  additional  debug  information  when
	   compiling.  The default is to not print debug information.

       -march=cpu-type
	   Generate code that runs on cpu-type,	which is the name of a	system
	   representing	 a  certain  processor type.  Possible values for cpu-
	   type	are z900/arch5,	z990/arch6,  z9-109,  z9-ec/arch7,  z10/arch8,
	   z196/arch9,	zEC12, z13/arch11, z14/arch12, z15/arch13, z16/arch14,
	   and native.

	   The default is -march=z900.

	   Specifying native as	cpu type  can  be  used	 to  select  the  best
	   architecture	 option	 for the host processor.  -march=native	has no
	   effect if GCC does not recognize the	processor.

       -mtune=cpu-type
	   Tune	to cpu-type everything applicable about	 the  generated	 code,
	   except for the ABI and the set of available instructions.  The list
	   of  cpu-type	 values	is the same as for -march.  The	default	is the
	   value used for -march.

       -mtpf-trace
       -mno-tpf-trace
	   Generate code that adds (does not add) in TPF OS specific  branches
	   to  trace  routines in the operating	system.	 This option is	off by
	   default, even when compiling	for the	TPF OS.

       -mtpf-trace-skip
       -mno-tpf-trace-skip
	   Generate code that changes (does not	 change)  the  default	branch
	   targets  enabled  by	 -mtpf-trace  to  point	 to  specialized trace
	   routines providing the ability  of  selectively  skipping  function
	   trace  entries for the TPF OS.  This	option is off by default, even
	   when	compiling for the TPF OS and specifying	-mtpf-trace.

       -mfused-madd
       -mno-fused-madd
	   Generate code that uses (does not use) the floating-point  multiply
	   and	accumulate  instructions.  These instructions are generated by
	   default if hardware floating	point is used.

       -mwarn-framesize=framesize
	   Emit	a warning if the current  function  exceeds  the  given	 frame
	   size.  Because this is a compile-time check it doesn't need to be a
	   real	 problem  when	the  program runs.  It is intended to identify
	   functions that most probably	cause a	stack overflow.	 It is	useful
	   to be used in an environment	with limited stack size	e.g. the linux
	   kernel.

       -mwarn-dynamicstack
	   Emit	 a warning if the function calls "alloca" or uses dynamically-
	   sized arrays.  This is generally a bad idea with  a	limited	 stack
	   size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
	   If  these  options are provided the S/390 back end emits additional
	   instructions	in the function	prologue that trigger a	 trap  if  the
	   stack size is stack-guard bytes above the stack-size	(remember that
	   the	stack  on S/390	grows downward).  If the stack-guard option is
	   omitted the smallest	power of 2 larger than the frame size  of  the
	   compiled function is	chosen.	 These options are intended to be used
	   to  help  debugging	stack  overflow	 problems.   The  additionally
	   emitted code	causes only little overhead and	hence can also be used
	   in production-like systems without greater performance degradation.
	   The given values have to be exact powers of 2 and stack-size	has to
	   be greater than stack-guard without exceeding 64k.  In order	to  be
	   efficient the extra code makes the assumption that the stack	starts
	   at an address aligned to the	value given by stack-size.  The	stack-
	   guard option	can only be used in conjunction	with stack-size.

       -mhotpatch=pre-halfwords,post-halfwords
	   If  the  hotpatch  option  is  enabled,  a  "hot-patching" function
	   prologue is generated for all functions in  the  compilation	 unit.
	   The	funtion	 label	is prepended with the given number of two-byte
	   NOP	instructions  (pre-halfwords,  maximum	1000000).   After  the
	   label, 2 * post-halfwords bytes are appended, using the largest NOP
	   like	instructions the architecture allows (maximum 1000000).

	   If both arguments are zero, hotpatching is disabled.

	   This	 option	 can  be  overridden for individual functions with the
	   "hotpatch" attribute.

       Score Options

       These options are defined for Score implementations:

       -meb
	   Compile code	for big-endian mode.  This is the default.

       -mel
	   Compile code	for little-endian mode.

       -mnhwloop
	   Disable generation of "bcnz"	instructions.

       -muls
	   Enable generation of	unaligned load and store instructions.

       -mmac
	   Enable the use of  multiply-accumulate  instructions.  Disabled  by
	   default.

       -mscore5
	   Specify the SCORE5 as the target architecture.

       -mscore5u
	   Specify the SCORE5U of the target architecture.

       -mscore7
	   Specify the SCORE7 as the target architecture. This is the default.

       -mscore7d
	   Specify the SCORE7D as the target architecture.

       SH Options

       These -m	options	are defined for	the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
	   Generate code for the SH2e.

       -m2a-nofpu
	   Generate code for the SH2a without FPU, or for a SH2a-FPU in	such a
	   way that the	floating-point unit is not used.

       -m2a-single-only
	   Generate  code  for	the  SH2a-FPU,	in  such a way that no double-
	   precision floating-point operations are used.

       -m2a-single
	   Generate code for the SH2a-FPU assuming the floating-point unit  is
	   in single-precision mode by default.

       -m2a
	   Generate  code for the SH2a-FPU assuming the	floating-point unit is
	   in double-precision mode by default.

       -m3 Generate code for the SH3.

       -m3e
	   Generate code for the SH3e.

       -m4-nofpu
	   Generate code for the SH4 without a floating-point unit.

       -m4-single-only
	   Generate code for the SH4 with  a  floating-point  unit  that  only
	   supports single-precision arithmetic.

       -m4-single
	   Generate  code  for	the SH4	assuming the floating-point unit is in
	   single-precision mode by default.

       -m4 Generate code for the SH4.

       -m4-100
	   Generate code for SH4-100.

       -m4-100-nofpu
	   Generate code for SH4-100 in	such a	way  that  the	floating-point
	   unit	is not used.

       -m4-100-single
	   Generate  code  for	SH4-100	assuming the floating-point unit is in
	   single-precision mode by default.

       -m4-100-single-only
	   Generate code for SH4-100 in	such a way  that  no  double-precision
	   floating-point operations are used.

       -m4-200
	   Generate code for SH4-200.

       -m4-200-nofpu
	   Generate  code for SH4-200 without in such a	way that the floating-
	   point unit is not used.

       -m4-200-single
	   Generate code for SH4-200 assuming the floating-point  unit	is  in
	   single-precision mode by default.

       -m4-200-single-only
	   Generate  code  for	SH4-200	in such	a way that no double-precision
	   floating-point operations are used.

       -m4-300
	   Generate code for SH4-300.

       -m4-300-nofpu
	   Generate code for SH4-300 without in	such a way that	the  floating-
	   point unit is not used.

       -m4-300-single
	   Generate  code  for	SH4-300	in such	a way that no double-precision
	   floating-point operations are used.

       -m4-300-single-only
	   Generate code for SH4-300 in	such a way  that  no  double-precision
	   floating-point operations are used.

       -m4-340
	   Generate code for SH4-340 (no MMU, no FPU).

       -m4-500
	   Generate  code  for SH4-500 (no FPU).  Passes -isa=sh4-nofpu	to the
	   assembler.

       -m4a-nofpu
	   Generate code for the SH4al-dsp, or for a SH4a in such a  way  that
	   the floating-point unit is not used.

       -m4a-single-only
	   Generate  code for the SH4a,	in such	a way that no double-precision
	   floating-point operations are used.

       -m4a-single
	   Generate code for the SH4a assuming the floating-point unit	is  in
	   single-precision mode by default.

       -m4a
	   Generate code for the SH4a.

       -m4al
	   Same	 as  -m4a-nofpu,  except that it implicitly passes -dsp	to the
	   assembler.  GCC  doesn't  generate  any  DSP	 instructions  at  the
	   moment.

       -mb Compile code	for the	processor in big-endian	mode.

       -ml Compile code	for the	processor in little-endian mode.

       -mdalign
	   Align  doubles  at  64-bit  boundaries.  Note that this changes the
	   calling conventions,	and thus some functions	from  the  standard  C
	   library do not work unless you recompile it first with -mdalign.

       -mrelax
	   Shorten  some  address references at	link time, when	possible; uses
	   the linker option -relax.

       -mbigtable
	   Use 32-bit offsets in "switch"  tables.   The  default  is  to  use
	   16-bit offsets.

       -mbitops
	   Enable the use of bit manipulation instructions on SH2A.

       -mfmovd
	   Enable  the	use  of	 the  instruction "fmovd".  Check -mdalign for
	   alignment constraints.

       -mrenesas
	   Comply with the calling conventions defined by Renesas.

       -mno-renesas
	   Comply with the calling conventions	defined	 for  GCC  before  the
	   Renesas conventions were available.	This option is the default for
	   all targets of the SH toolchain.

       -mnomacsave
	   Mark	 the  "MAC"  register  as call-clobbered, even if -mrenesas is
	   given.

       -mieee
       -mno-ieee
	   Control the IEEE compliance of  floating-point  comparisons,	 which
	   affects  the	 handling of cases where the result of a comparison is
	   unordered.	By  default  -mieee   is   implicitly	enabled.    If
	   -ffinite-math-only  is  enabled  -mno-ieee is implicitly set, which
	   results  in	faster	floating-point	greater-equal  and  less-equal
	   comparisons.	 The implicit settings can be overridden by specifying
	   either -mieee or -mno-ieee.

       -minline-ic_invalidate
	   Inline  code	 to invalidate instruction cache entries after setting
	   up nested function trampolines.   This  option  has	no  effect  if
	   -musermode  is  in  effect  and the selected	code generation	option
	   (e.g. -m4) does not allow the use of	the  "icbi"  instruction.   If
	   the	selected  code generation option does not allow	the use	of the
	   "icbi" instruction, and -musermode is not in	 effect,  the  inlined
	   code	 manipulates the instruction cache address array directly with
	   an associative write.  This not only	requires  privileged  mode  at
	   run	time,  but it also fails if the	cache line had been mapped via
	   the TLB and has become unmapped.

       -misize
	   Dump	instruction size and location in the assembly code.

       -mpadstruct
	   This	option is deprecated.  It pads structures  to  multiple	 of  4
	   bytes, which	is incompatible	with the SH ABI.

       -matomic-model=model
	   Sets	 the model of atomic operations	and additional parameters as a
	   comma separated list.  For details on the atomic built-in functions
	   see __atomic	Builtins.  The following  models  and  parameters  are
	   supported:

	   none
	       Disable	compiler  generated  atomic sequences and emit library
	       calls for atomic	operations.  This is the default if the	target
	       is not "sh*-*-linux*".

	   soft-gusa
	       Generate	GNU/Linux compatible gUSA  software  atomic  sequences
	       for  the	 atomic	 built-in  functions.	The  generated	atomic
	       sequences    require    additional     support	  from	   the
	       interrupt/exception  handling  code  of the system and are only
	       suitable	for SH3* and SH4* single-core systems.	This option is
	       enabled by default when the target is "sh*-*-linux*"  and  SH3*
	       or  SH4*.   When	the target is SH4A, this option	also partially
	       utilizes	 the  hardware	atomic	instructions   "movli.l"   and
	       "movco.l"  to  create  more  efficient  code,  unless strict is
	       specified.

	   soft-tcb
	       Generate	software atomic	sequences that use a variable  in  the
	       thread  control	block.	 This  is  a  variation	 of  the  gUSA
	       sequences which can also	be used	on SH1*	and SH2* targets.  The
	       generated atomic	sequences require additional support from  the
	       interrupt/exception  handling  code  of the system and are only
	       suitable	for single-core	systems.  When using this  model,  the
	       gbr-offset= parameter has to be specified as well.

	   soft-imask
	       Generate	 software  atomic  sequences  that temporarily disable
	       interrupts by setting "SR.IMASK = 1111".	 This model works only
	       when the	program	runs in	privileged mode	and is	only  suitable
	       for   single-core   systems.    Additional   support  from  the
	       interrupt/exception  handling  code  of	the  system   is   not
	       required.   This	model is enabled by default when the target is
	       "sh*-*-linux*" and SH1* or SH2*.

	   hard-llcs
	       Generate	hardware atomic	 sequences  using  the	"movli.l"  and
	       "movco.l"  instructions	only.	This is	only available on SH4A
	       and is suitable for multi-core  systems.	  Since	 the  hardware
	       instructions  support  only 32 bit atomic variables access to 8
	       or 16 bit variables is emulated with  32	 bit  accesses.	  Code
	       compiled	 with  this  option  is	 also  compatible  with	 other
	       software	atomic model interrupt/exception handling  systems  if
	       executed	 on  an	 SH4A  system.	 Additional  support  from the
	       interrupt/exception handling code of the	system is not required
	       for this	model.

	   gbr-offset=
	       This parameter specifies	the offset in bytes of the variable in
	       the thread control block	structure that should be used  by  the
	       generated  atomic  sequences  when  the soft-tcb	model has been
	       selected.  For other models this	 parameter  is	ignored.   The
	       specified  value	must be	an integer multiple of four and	in the
	       range 0-1020.

	   strict
	       This parameter prevents mixed usage of multiple atomic  models,
	       even  if	 they  are compatible, and makes the compiler generate
	       atomic sequences	of the specified model only.

       -mtas
	   Generate the	"tas.b"	opcode	for  "__atomic_test_and_set".	Notice
	   that	  depending   on   the	 particular   hardware	 and  software
	   configuration this can  degrade  overall  performance  due  to  the
	   operand  cache  line	 flushes  that	are  implied  by  the  "tas.b"
	   instruction.	 On multi-core SH4A processors the "tas.b" instruction
	   must	be used	with caution since it can result  in  data  corruption
	   for certain cache configurations.

       -mprefergot
	   When	 generating  position-independent  code,  emit	function calls
	   using the Global Offset Table  instead  of  the  Procedure  Linkage
	   Table.

       -musermode
       -mno-usermode
	   Don't  allow	 (allow) the compiler generating privileged mode code.
	   Specifying -musermode also implies -mno-inline-ic_invalidate	if the
	   inlined code	would not  work	 in  user  mode.   -musermode  is  the
	   default  when  the target is	"sh*-*-linux*".	 If the	target is SH1*
	   or SH2* -musermode has no effect, since there is no user mode.

       -multcost=number
	   Set the cost	to assume for a	multiply insn.

       -mdiv=strategy
	   Set	the  division  strategy	 to  be	 used  for  integer   division
	   operations.	strategy can be	one of:

	   call-div1
	       Calls  a	 library  function  that uses the single-step division
	       instruction "div1" to perform the operation.  Division by  zero
	       calculates  an  unspecified  result and does not	trap.  This is
	       the default except for SH4, SH2A	and SHcompact.

	   call-fp
	       Calls a library function	that performs the operation in	double
	       precision  floating point.  Division by zero causes a floating-
	       point exception.	 This is the default for SHcompact  with  FPU.
	       Specifying this for targets that	do not have a double precision
	       FPU defaults to "call-div1".

	   call-table
	       Calls  a	 library  function  that uses a	lookup table for small
	       divisors	and the	"div1" instruction with	case  distinction  for
	       larger  divisors.   Division  by	zero calculates	an unspecified
	       result and does	not  trap.   This  is  the  default  for  SH4.
	       Specifying  this	 for  targets  that  do	not have dynamic shift
	       instructions defaults to	"call-div1".

	   When	a  division  strategy  has  not	 been  specified  the  default
	   strategy  is	 selected  based  on the current target.  For SH2A the
	   default strategy is to  use	the  "divs"  and  "divu"  instructions
	   instead of library function calls.

       -maccumulate-outgoing-args
	   Reserve  space once for outgoing arguments in the function prologue
	   rather than around each call.  Generally beneficial for performance
	   and size.  Also needed for unwinding	to avoid  changing  the	 stack
	   frame around	conditional code.

       -mdivsi3_libfunc=name
	   Set	the  name  of  the  library  function  used  for 32-bit	signed
	   division to name.  This only	affects	the  name  used	 in  the  call
	   division  strategies,  and the compiler still expects the same sets
	   of input/output/clobbered registers as  if  this  option  were  not
	   present.

       -mfixed-range=register-range
	   Generate code treating the given register range as fixed registers.
	   A  fixed  register  is  one that the	register allocator cannot use.
	   This	is useful when compiling kernel	code.	A  register  range  is
	   specified  as two registers separated by a dash.  Multiple register
	   ranges can be specified separated by	a comma.

       -mbranch-cost=num
	   Assume num to be the	cost for a branch instruction.	Higher numbers
	   make	 the  compiler	try  to	 generate  more	 branch-free  code  if
	   possible.   If not specified	the value is selected depending	on the
	   processor type that is being	compiled for.

       -mzdcbranch
       -mno-zdcbranch
	   Assume (do not assume) that zero  displacement  conditional	branch
	   instructions	 "bt" and "bf" are fast.  If -mzdcbranch is specified,
	   the compiler	prefers	zero displacement branch code sequences.  This
	   is enabled by default when generating code for SH4  and  SH4A.   It
	   can be explicitly disabled by specifying -mno-zdcbranch.

       -mcbranch-force-delay-slot
	   Force  the  usage  of  delay	 slots for conditional branches, which
	   stuffs the delay slot with a	"nop" if a suitable instruction	cannot
	   be found.  By default this option is	disabled.  It can  be  enabled
	   to work around hardware bugs	as found in the	original SH7055.

       -mfused-madd
       -mno-fused-madd
	   Generate  code that uses (does not use) the floating-point multiply
	   and accumulate instructions.	 These instructions are	 generated  by
	   default  if hardware	floating point is used.	 The machine-dependent
	   -mfused-madd	 option	 is  now  mapped  to  the  machine-independent
	   -ffp-contract=fast	option,	  and  -mno-fused-madd	is  mapped  to
	   -ffp-contract=off.

       -mfsca
       -mno-fsca
	   Allow or disallow the compiler to emit the "fsca"  instruction  for
	   sine	 and cosine approximations.  The option	-mfsca must be used in
	   combination with -funsafe-math-optimizations.   It  is  enabled  by
	   default  when  generating  code for SH4A.  Using -mno-fsca disables
	   sine	and cosine approximations even if  -funsafe-math-optimizations
	   is in effect.

       -mfsrra
       -mno-fsrra
	   Allow  or disallow the compiler to emit the "fsrra" instruction for
	   reciprocal square root approximations.  The option -mfsrra must  be
	   used	   in	combination   with   -funsafe-math-optimizations   and
	   -ffinite-math-only.	It is enabled by default when generating  code
	   for	 SH4A.	 Using	-mno-fsrra  disables  reciprocal  square  root
	   approximations    even    if	   -funsafe-math-optimizations	   and
	   -ffinite-math-only are in effect.

       -mpretend-cmove
	   Prefer  zero-displacement conditional branches for conditional move
	   instruction patterns.  This can result in faster code  on  the  SH4
	   processor.

       -mfdpic
	   Generate code using the FDPIC ABI.

       Solaris 2 Options

       These -m	options	are supported on Solaris 2:

       -mclear-hwcap
	   -mclear-hwcap   tells   the	 compiler   to	 remove	 the  hardware
	   capabilities	generated by the  Solaris  assembler.	This  is  only
	   necessary when object files use ISA extensions not supported	by the
	   current machine, but	check at runtime whether or not	to use them.

       -mimpure-text
	   -mimpure-text,  used	 in addition to	-shared, tells the compiler to
	   not pass -z text to the linker when linking a shared	object.	 Using
	   this	option,	you can	link position-dependent	 code  into  a	shared
	   object.

	   -mimpure-text    suppresses	 the   "relocations   remain   against
	   allocatable	but  non-writable  sections"  linker  error   message.
	   However,  the  necessary relocations	trigger	copy-on-write, and the
	   shared object is not	actually shared	across processes.  Instead  of
	   using  -mimpure-text, you should compile all	source code with -fpic
	   or -fPIC.

       These switches are supported in addition	to the above on	Solaris	2:

       -pthreads
	   This	is a synonym for -pthread.

       SPARC Options

       These -m	options	are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
	   Specify -mapp-regs to generate output using the global registers  2
	   through  4,	which  the  SPARC  SVR4	ABI reserves for applications.
	   Like	the global register 1, each global register  2	through	 4  is
	   then	treated	as an allocable	register that is clobbered by function
	   calls.  This	is the default.

	   To  be  fully  SVR4	ABI-compliant  at the cost of some performance
	   loss, specify -mno-app-regs.	  You  should  compile	libraries  and
	   system software with	this option.

       -mflat
       -mno-flat
	   With	  -mflat,   the	  compiler   does  not	generate  save/restore
	   instructions	and uses a "flat" or  single  register	window	model.
	   This	 model	is  compatible with the	regular	register window	model.
	   The local registers	and  the  input	 registers  (0--5)  are	 still
	   treated  as	"call-saved"  registers	 and are saved on the stack as
	   needed.

	   With	-mno-flat (the default), the compiler  generates  save/restore
	   instructions	 (except  for  leaf  functions).   This	 is the	normal
	   operating mode.

       -mfpu
       -mhard-float
	   Generate output containing floating-point  instructions.   This  is
	   the default.

       -mno-fpu
       -msoft-float
	   Generate  output  containing	 library  calls	 for  floating	point.
	   Warning: the	requisite libraries are	not available  for  all	 SPARC
	   targets.  Normally the facilities of	the machine's usual C compiler
	   are	used,  but  this cannot	be done	directly in cross-compilation.
	   You must make your own arrangements	to  provide  suitable  library
	   functions for cross-compilation.  The embedded targets sparc-*-aout
	   and sparclite-*-* do	provide	software floating-point	support.

	   -msoft-float	 changes  the  calling	convention in the output file;
	   therefore, it is only useful	if you compile all of a	 program  with
	   this	 option.   In  particular,  you	 need to compile libgcc.a, the
	   library that	comes with GCC,	with -msoft-float in order for this to
	   work.

       -mhard-quad-float
	   Generate output containing quad-word	(long  double)	floating-point
	   instructions.

       -msoft-quad-float
	   Generate  output  containing	 library  calls	 for  quad-word	 (long
	   double) floating-point  instructions.   The	functions  called  are
	   those specified in the SPARC	ABI.  This is the default.

	   As  of  this	 writing, there	are no SPARC implementations that have
	   hardware support for	 the  quad-word	 floating-point	 instructions.
	   They	 all  invoke a trap handler for	one of these instructions, and
	   then	the trap handler  emulates  the	 effect	 of  the  instruction.
	   Because  of	the  trap  handler  overhead, this is much slower than
	   calling the	ABI  library  routines.	  Thus	the  -msoft-quad-float
	   option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
	   Assume that doubles have 8-byte alignment.  This is the default.

	   With	 -munaligned-doubles,  GCC  assumes  that  doubles have	8-byte
	   alignment only if they are contained	in another type,  or  if  they
	   have	 an  absolute address.	Otherwise, it assumes they have	4-byte
	   alignment.  Specifying this option avoids some  rare	 compatibility
	   problems  with  code	 generated  by other compilers.	 It is not the
	   default because it results in a performance	loss,  especially  for
	   floating-point code.

       -muser-mode
       -mno-user-mode
	   Do not generate code	that can only run in supervisor	mode.  This is
	   relevant  only  for	the  "casa"  instruction emitted for the LEON3
	   processor.  This is the default.

       -mfaster-structs
       -mno-faster-structs
	   With	-mfaster-structs, the compiler assumes that structures	should
	   have	 8-byte	alignment.  This enables the use of pairs of "ldd" and
	   "std" instructions for copies in structure assignment, in place  of
	   twice  as  many  "ld"  and  "st"  pairs.   However, the use of this
	   changed alignment directly violates	the  SPARC  ABI.   Thus,  it's
	   intended  only  for use on targets where the	developer acknowledges
	   that	their resulting	code is	not directly in	line with the rules of
	   the ABI.

       -mstd-struct-return
       -mno-std-struct-return
	   With	-mstd-struct-return, the compiler generates checking  code  in
	   functions  returning	structures or unions to	detect size mismatches
	   between the two sides of function calls, as per the 32-bit ABI.

	   The default is -mno-std-struct-return.  This	option has  no	effect
	   in 64-bit mode.

       -mlra
       -mno-lra
	   Enable  Local  Register  Allocation.	 This is the default for SPARC
	   since GCC 7 so -mno-lra needs to be passed to get old Reload.

       -mcpu=cpu_type
	   Set the instruction set, register set, and  instruction  scheduling
	   parameters	for  machine  type  cpu_type.	Supported  values  for
	   cpu_type are	v7, cypress, v8, supersparc, hypersparc, leon,	leon3,
	   leon3v7,  leon5,  sparclite,	 f930,	f934,  sparclite86x, sparclet,
	   tsc701, v9, ultrasparc, ultrasparc3,	niagara,  niagara2,  niagara3,
	   niagara4, niagara7 and m8.

	   Native  Solaris  and	 GNU/Linux  toolchains	also support the value
	   native, which selects the best architecture	option	for  the  host
	   processor.	-mcpu=native  has  no effect if	GCC does not recognize
	   the processor.

	   Default instruction scheduling parameters are used for values  that
	   select  an  architecture  and not an	implementation.	 These are v7,
	   v8, sparclite, sparclet, v9.

	   Here	is a list of each supported architecture and  their  supported
	   implementations.

	   v7  cypress,	leon3v7

	   v8  supersparc, hypersparc, leon, leon3, leon5

	   sparclite
	       f930, f934, sparclite86x

	   sparclet
	       tsc701

	   v9  ultrasparc, ultrasparc3,	niagara, niagara2, niagara3, niagara4,
	       niagara7, m8

	   By  default	(unless	 configured otherwise),	GCC generates code for
	   the V7 variant of the SPARC architecture.  With -mcpu=cypress,  the
	   compiler additionally optimizes it for the Cypress CY7C602 chip, as
	   used	 in  the  SPARCStation/SPARCServer  3xx	 series.  This is also
	   appropriate for the older SPARCStation 1, 2,	IPX etc.

	   With	-mcpu=v8, GCC generates	code for the V8	variant	of  the	 SPARC
	   architecture.   The	only  difference  from	V7  code  is  that the
	   compiler emits the integer multiply and integer divide instructions
	   which   exist   in	SPARC-V8   but	 not   in   SPARC-V7.	  With
	   -mcpu=supersparc,  the  compiler  additionally optimizes it for the
	   SuperSPARC chip, as used in the  SPARCStation  10,  1000  and  2000
	   series.

	   With	 -mcpu=sparclite, GCC generates	code for the SPARClite variant
	   of the SPARC	architecture.  This adds the integer multiply, integer
	   divide step and scan	("ffs")	instructions which exist in  SPARClite
	   but	not  in	 SPARC-V7.  With -mcpu=f930, the compiler additionally
	   optimizes it	for the	Fujitsu	MB86930	chip, which  is	 the  original
	   SPARClite, with no FPU.  With -mcpu=f934, the compiler additionally
	   optimizes it	for the	Fujitsu	MB86934	chip, which is the more	recent
	   SPARClite with FPU.

	   With	-mcpu=sparclet,	GCC generates code for the SPARClet variant of
	   the	 SPARC	 architecture.	  This	 adds  the  integer  multiply,
	   multiply/accumulate,	 integer  divide   step	  and	scan   ("ffs")
	   instructions	 which	exist  in  SPARClet but	not in SPARC-V7.  With
	   -mcpu=tsc701, the compiler additionally optimizes it	for the	 TEMIC
	   SPARClet chip.

	   With	 -mcpu=v9,  GCC	generates code for the V9 variant of the SPARC
	   architecture.  This adds 64-bit  integer  and  floating-point  move
	   instructions,  3 additional floating-point condition	code registers
	   and conditional  move  instructions.	  With	-mcpu=ultrasparc,  the
	   compiler  additionally optimizes it for the Sun UltraSPARC I/II/IIi
	   chips.  With	-mcpu=ultrasparc3, the compiler	additionally optimizes
	   it for the Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+	 chips.	  With
	   -mcpu=niagara,  the	compiler  additionally	optimizes  it  for Sun
	   UltraSPARC	T1   chips.    With   -mcpu=niagara2,	the   compiler
	   additionally	 optimizes  it	for  Sun  UltraSPARC  T2  chips.  With
	   -mcpu=niagara3, the compiler	 additionally  optimizes  it  for  Sun
	   UltraSPARC	T3   chips.    With   -mcpu=niagara4,	the   compiler
	   additionally	optimizes  it  for  Sun	 UltraSPARC  T4	 chips.	  With
	   -mcpu=niagara7,  the	 compiler additionally optimizes it for	Oracle
	   SPARC M7 chips.  With -mcpu=m8, the compiler	additionally optimizes
	   it for Oracle M8 chips.

       -mtune=cpu_type
	   Set	the  instruction  scheduling  parameters  for	machine	  type
	   cpu_type,  but  do not set the instruction set or register set that
	   the option -mcpu=cpu_type does.

	   The same values for -mcpu=cpu_type can be used for -mtune=cpu_type,
	   but the only	useful values are those	that select a  particular  CPU
	   implementation.   Those  are	cypress, supersparc, hypersparc, leon,
	   leon3,  leon3v7,   leon5,   f930,   f934,   sparclite86x,   tsc701,
	   ultrasparc,	ultrasparc3,  niagara,	niagara2,  niagara3, niagara4,
	   niagara7 and	m8.  With native  Solaris  and	GNU/Linux  toolchains,
	   native can also be used.

       -mv8plus
       -mno-v8plus
	   With	 -mv8plus,  GCC	 generates  code  for  the SPARC-V8+ ABI.  The
	   difference from the V8 ABI is that the global and out registers are
	   considered 64 bits wide.  This is enabled by	default	on Solaris  in
	   32-bit mode for all SPARC-V9	processors.

       -mvis
       -mno-vis
	   With	 -mvis,	 GCC  generates	 code  that  takes  advantage  of  the
	   UltraSPARC Visual  Instruction  Set	extensions.   The  default  is
	   -mno-vis.

       -mvis2
       -mno-vis2
	   With	-mvis2,	GCC generates code that	takes advantage	of version 2.0
	   of  the  UltraSPARC Visual Instruction Set extensions.  The default
	   is -mvis2 when targeting a cpu  that	 supports  such	 instructions,
	   such	as UltraSPARC-III and later.  Setting -mvis2 also sets -mvis.

       -mvis3
       -mno-vis3
	   With	-mvis3,	GCC generates code that	takes advantage	of version 3.0
	   of  the  UltraSPARC Visual Instruction Set extensions.  The default
	   is -mvis3 when targeting a cpu  that	 supports  such	 instructions,
	   such	 as  niagara-3 and later.  Setting -mvis3 also sets -mvis2 and
	   -mvis.

       -mvis4
       -mno-vis4
	   With	-mvis4,	GCC generates code that	takes advantage	of version 4.0
	   of the UltraSPARC Visual Instruction	Set extensions.	  The  default
	   is  -mvis4  when  targeting	a cpu that supports such instructions,
	   such	as niagara-7 and later.	  Setting  -mvis4  also	 sets  -mvis3,
	   -mvis2 and -mvis.

       -mvis4b
       -mno-vis4b
	   With	 -mvis4b,  GCC	generates code that takes advantage of version
	   4.0 of the UltraSPARC Visual	Instruction Set	extensions,  plus  the
	   additional	VIS   instructions  introduced	in  the	 Oracle	 SPARC
	   Architecture	2017.  The default is -mvis4b  when  targeting	a  cpu
	   that	 supports  such	 instructions,	such as	m8 and later.  Setting
	   -mvis4b also	sets -mvis4, -mvis3, -mvis2 and	-mvis.

       -mcbcond
       -mno-cbcond
	   With	-mcbcond, GCC generates	 code  that  takes  advantage  of  the
	   UltraSPARC	Compare-and-Branch-on-Condition	  instructions.	   The
	   default is  -mcbcond	 when  targeting  a  CPU  that	supports  such
	   instructions, such as Niagara-4 and later.

       -mfmaf
       -mno-fmaf
	   With	 -mfmaf,  GCC  generates  code	that  takes  advantage	of the
	   UltraSPARC Fused  Multiply-Add  Floating-point  instructions.   The
	   default   is	 -mfmaf	 when  targeting  a  CPU  that	supports  such
	   instructions, such as Niagara-3 and later.

       -mfsmuld
       -mno-fsmuld
	   With	-mfsmuld, GCC generates	 code  that  takes  advantage  of  the
	   Floating-point Multiply Single to Double (FsMULd) instruction.  The
	   default   is	  -mfsmuld   when   targeting  a  CPU  supporting  the
	   architecture	versions V8 or V9 with FPU except -mcpu=leon.

       -mpopc
       -mno-popc
	   With	-mpopc,	 GCC  generates	 code  that  takes  advantage  of  the
	   UltraSPARC  Population  Count  instruction.	 The default is	-mpopc
	   when	targeting a CPU	that supports such  an	instruction,  such  as
	   Niagara-2 and later.

       -msubxc
       -mno-subxc
	   With	 -msubxc,  GCC	generates  code	 that  takes  advantage	of the
	   UltraSPARC Subtract-Extended-with-Carry instruction.	  The  default
	   is  -msubxc when targeting a	CPU that supports such an instruction,
	   such	as Niagara-7 and later.

       -mfix-at697f
	   Enable the documented workaround for	 the  single  erratum  of  the
	   Atmel  AT697F  processor  (which  corresponds to erratum #13	of the
	   AT697E processor).

       -mfix-ut699
	   Enable the documented workarounds for the floating-point errata and
	   the data cache nullify errata of the	UT699 processor.

       -mfix-ut700
	   Enable the documented workaround for	the back-to-back store	errata
	   of the UT699E/UT700 processor.

       -mfix-gr712rc
	   Enable  the documented workaround for the back-to-back store	errata
	   of the GR712RC processor.

       These -m	options	are supported in addition to  the  above  on  SPARC-V9
       processors in 64-bit environments:

       -m32
       -m64
	   Generate  code  for	a  32-bit  or  64-bit environment.  The	32-bit
	   environment sets int, long and pointer  to  32  bits.   The	64-bit
	   environment sets int	to 32 bits and long and	pointer	to 64 bits.

       -mcmodel=which
	   Set the code	model to one of

	   medlow
	       The  Medium/Low	code model: 64-bit addresses, programs must be
	       linked  in  the	low  32	 bits  of  memory.   Programs  can  be
	       statically or dynamically linked.

	   medmid
	       The  Medium/Middle  code	model: 64-bit addresses, programs must
	       be linked in the	low 44 bits  of	 memory,  the  text  and  data
	       segments	 must  be  less	 than 2GB in size and the data segment
	       must be located within 2GB of the text segment.

	   medany
	       The Medium/Anywhere code	model: 64-bit addresses, programs  may
	       be  linked  anywhere in memory, the text	and data segments must
	       be less than 2GB	in size	and the	data segment must  be  located
	       within 2GB of the text segment.

	   embmedany
	       The  Medium/Anywhere  code  model  for embedded systems:	64-bit
	       addresses, the text and data segments must be less than 2GB  in
	       size,  both  starting  anywhere	in  memory (determined at link
	       time).  The global register %g4 points to the base of the  data
	       segment.	  Programs  are	 statically  linked  and  PIC  is  not
	       supported.

       -mmemory-model=mem-model
	   Set the memory model	in force on the	processor to one of

	   default
	       The default  memory  model  for	the  processor	and  operating
	       system.

	   rmo Relaxed Memory Order

	   pso Partial Store Order

	   tso Total Store Order

	   sc  Sequential Consistency

	   These  memory  models  are  formally	 defined  in Appendix D	of the
	   SPARC-V9 architecture manual, as set	in the processor's "PSTATE.MM"
	   field.

       -mstack-bias
       -mno-stack-bias
	   With	-mstack-bias, GCC assumes that the stack  pointer,  and	 frame
	   pointer  if	present,  are offset by	-2047 which must be added back
	   when	making stack frame references.	This is	the default in	64-bit
	   mode.  Otherwise, assume no such offset is present.

       Options for System V

       These  additional  options  are	available  on  System  V Release 4 for
       compatibility with other	compilers on those systems:

       -G  Create a shared  object.   It  is  recommended  that	 -symbolic  or
	   -shared be used instead.

       -Qy Identify  the  versions  of	each  tool  used by the	compiler, in a
	   ".ident" assembler directive	in the output.

       -Qn Refrain from	adding ".ident"	directives to the output file (this is
	   the default).

       -YP,dirs
	   Search the directories dirs,	and no others, for libraries specified
	   with	-l.

       -Ym,dir
	   Look	in the	directory  dir	to  find  the  M4  preprocessor.   The
	   assembler uses this option.

       TILE-Gx Options

       These -m	options	are supported on the TILE-Gx:

       -mcmodel=small
	   Generate  code  for the small model.	 The distance for direct calls
	   is limited to 500M in either	direction.  PC-relative	addresses  are
	   32 bits.  Absolute addresses	support	the full address range.

       -mcmodel=large
	   Generate  code for the large	model.	There is no limitation on call
	   distance, pc-relative addresses, or absolute	addresses.

       -mcpu=name
	   Selects the type  of	 CPU  to  be  targeted.	  Currently  the  only
	   supported type is tilegx.

       -m32
       -m64
	   Generate  code  for	a  32-bit  or  64-bit environment.  The	32-bit
	   environment sets int, long, and pointer to  32  bits.   The	64-bit
	   environment sets int	to 32 bits and long and	pointer	to 64 bits.

       -mbig-endian
       -mlittle-endian
	   Generate code in big/little endian mode, respectively.

       TILEPro Options

       These -m	options	are supported on the TILEPro:

       -mcpu=name
	   Selects  the	 type  of  CPU	to  be	targeted.   Currently the only
	   supported type is tilepro.

       -m32
	   Generate code for a 32-bit environment, which sets int,  long,  and
	   pointer  to	32  bits.   This is the	only supported behavior	so the
	   flag	is essentially ignored.

       V850 Options

       These -m	options	are defined for	V850 implementations:

       -mlong-calls
       -mno-long-calls
	   Treat all calls as being far	away (near).  If calls are assumed  to
	   be  far away, the compiler always loads the function's address into
	   a register, and calls indirect through the pointer.

       -mno-ep
       -mep
	   Do not optimize (do optimize) basic blocks that use the same	 index
	   pointer 4 or	more times to copy pointer into	the "ep" register, and
	   use	the  shorter "sld" and "sst" instructions.  The	-mep option is
	   on by default if you	optimize.

       -mno-prolog-function
       -mprolog-function
	   Do not  use	(do  use)  external  functions	to  save  and  restore
	   registers at	the prologue and epilogue of a function.  The external
	   functions  are  slower,  but	 use  less code	space if more than one
	   function saves the same number of registers.	 The -mprolog-function
	   option is on	by default if you optimize.

       -mspace
	   Try to make the code	as small as possible.  At present,  this  just
	   turns on the	-mep and -mprolog-function options.

       -mtda=n
	   Put	static	or global variables whose size is n bytes or less into
	   the tiny data area that register "ep" points	 to.   The  tiny  data
	   area	 can  hold  up	to  256	 bytes	in  total  (128	bytes for byte
	   references).

       -msda=n
	   Put static or global	variables whose	size is	n bytes	or  less  into
	   the	small  data area that register "gp" points to.	The small data
	   area	can hold up to 64 kilobytes.

       -mzda=n
	   Put static or global	variables whose	size is	n bytes	or  less  into
	   the first 32	kilobytes of memory.

       -mv850
	   Specify that	the target processor is	the V850.

       -mv850e3v5
	   Specify   that   the	  target   processor  is  the  V850E3V5.   The
	   preprocessor	constant "__v850e3v5__"	is defined if this  option  is
	   used.

       -mv850e2v4
	   Specify  that  the  target  processor  is the V850E3V5.  This is an
	   alias for the -mv850e3v5 option.

       -mv850e2v3
	   Specify  that  the  target  processor   is	the   V850E2V3.	   The
	   preprocessor	 constant  "__v850e2v3__" is defined if	this option is
	   used.

       -mv850e2
	   Specify that	the target processor is	the V850E2.  The  preprocessor
	   constant "__v850e2__" is defined if this option is used.

       -mv850e1
	   Specify  that the target processor is the V850E1.  The preprocessor
	   constants "__v850e1__" and "__v850e__" are defined if  this	option
	   is used.

       -mv850es
	   Specify  that the target processor is the V850ES.  This is an alias
	   for the -mv850e1 option.

       -mv850e
	   Specify that	the target processor is	the V850E.   The  preprocessor
	   constant "__v850e__"	is defined if this option is used.

	   If  neither	-mv850	nor  -mv850e  nor  -mv850e1  nor  -mv850e2 nor
	   -mv850e2v3  nor  -mv850e3v5	are  defined  then  a  default	target
	   processor   is  chosen  and	the  relevant  __v850*__  preprocessor
	   constant is defined.

	   The preprocessor  constants	"__v850"  and  "__v851__"  are	always
	   defined, regardless of which	processor variant is the target.

       -mdisable-callt
       -mno-disable-callt
	   This	 option	 suppresses  generation	of the "CALLT" instruction for
	   the v850e, v850e1, v850e2, v850e2v3 and  v850e3v5  flavors  of  the
	   v850	architecture.

	   This	option is enabled by default when the RH850 ABI	is in use (see
	   -mrh850-abi),  and  disabled	by default when	the GCC	ABI is in use.
	   If "CALLT" instructions are being generated then the	C preprocessor
	   symbol "__V850_CALLT__" is defined.

       -mrelax
       -mno-relax
	   Pass	on (or do not pass on) the -mrelax command-line	option to  the
	   assembler.

       -mlong-jumps
       -mno-long-jumps
	   Disable   (or   re-enable)	the  generation	 of  PC-relative  jump
	   instructions.

       -msoft-float
       -mhard-float
	   Disable (or re-enable) the generation of  hardware  floating	 point
	   instructions.   This	 option	 is  only  significant when the	target
	   architecture	is V850E2V3 or higher.	 If  hardware  floating	 point
	   instructions	 are  being  generated	then the C preprocessor	symbol
	   "__FPU_OK__"	is  defined,  otherwise	 the  symbol  "__NO_FPU__"  is
	   defined.

       -mloop
	   Enables  the	 use  of  the  e3v5 LOOP instruction.  The use of this
	   instruction is not enabled by default when the e3v5 architecture is
	   selected because its	use is still experimental.

       -mrh850-abi
       -mghs
	   Enables support for the RH850 version of the	V850 ABI.  This	is the
	   default.  With this version of the ABI the following	rules apply:

	   *   Integer sized structures	and unions are returned	via  a	memory
	       pointer rather than a register.

	   *   Large  structures  and  unions  (more than 8 bytes in size) are
	       passed by value.

	   *   Functions are aligned to	16-bit boundaries.

	   *   The -m8byte-align command-line option is	supported.

	   *   The -mdisable-callt command-line	option is enabled by  default.
	       The -mno-disable-callt command-line option is not supported.

	   When	 this  version of the ABI is enabled the C preprocessor	symbol
	   "__V850_RH850_ABI__"	is defined.

       -mgcc-abi
	   Enables support for the old GCC version of the V850 ABI.  With this
	   version of the ABI the following rules apply:

	   *   Integer sized structures	and unions are	returned  in  register
	       "r10".

	   *   Large  structures  and  unions  (more than 8 bytes in size) are
	       passed by reference.

	   *   Functions are aligned to	32-bit boundaries,  unless  optimizing
	       for size.

	   *   The -m8byte-align command-line option is	not supported.

	   *   The  -mdisable-callt  command-line  option is supported but not
	       enabled by default.

	   When	this version of	the ABI	is enabled the C  preprocessor	symbol
	   "__V850_GCC_ABI__" is defined.

       -m8byte-align
       -mno-8byte-align
	   Enables support for "double"	and "long long"	types to be aligned on
	   8-byte boundaries.  The default is to restrict the alignment	of all
	   objects  to at most 4-bytes.	 When -m8byte-align is in effect the C
	   preprocessor	symbol "__V850_8BYTE_ALIGN__" is defined.

       -mbig-switch
	   Generate code suitable for big switch tables.  Use this option only
	   if the assembler/linker complain about out of range branches	within
	   a switch table.

       -mapp-regs
	   This	option causes r2 and r5	to be used in the  code	 generated  by
	   the compiler.  This setting is the default.

       -mno-app-regs
	   This	option causes r2 and r5	to be treated as fixed registers.

       VAX Options

       These -m	options	are defined for	the VAX:

       -munix
	   Do  not  output certain jump	instructions ("aobleq" and so on) that
	   the Unix assembler for the VAX cannot handle	across long ranges.

       -mgnu
	   Do output those jump	instructions, on the assumption	that  the  GNU
	   assembler is	being used.

       -mg Output   code   for	G-format  floating-point  numbers  instead  of
	   D-format.

       Visium Options

       -mdebug
	   A program which performs file I/O and is destined to	run on an  MCM
	   target  should be linked with this option.  It causes the libraries
	   libc.a and libdebug.a to be linked.	The program should be  run  on
	   the target under the	control	of the GDB remote debugging stub.

       -msim
	   A  program  which  performs	file I/O and is	destined to run	on the
	   simulator should be linked  with  option.   This  causes  libraries
	   libc.a and libsim.a to be linked.

       -mfpu
       -mhard-float
	   Generate  code containing floating-point instructions.  This	is the
	   default.

       -mno-fpu
       -msoft-float
	   Generate code containing library calls for floating-point.

	   -msoft-float	changes	the calling convention	in  the	 output	 file;
	   therefore,  it  is only useful if you compile all of	a program with
	   this	option.	 In particular,	you  need  to  compile	libgcc.a,  the
	   library that	comes with GCC,	with -msoft-float in order for this to
	   work.

       -mcpu=cpu_type
	   Set	the  instruction set, register set, and	instruction scheduling
	   parameters  for  machine  type  cpu_type.   Supported  values   for
	   cpu_type are	mcm, gr5 and gr6.

	   mcm is a synonym of gr5 present for backward	compatibility.

	   By  default	(unless	 configured otherwise),	GCC generates code for
	   the GR5 variant of the Visium architecture.

	   With	-mcpu=gr6, GCC generates code  for  the	 GR6  variant  of  the
	   Visium architecture.	 The only difference from GR5 code is that the
	   compiler will generate block	move instructions.

       -mtune=cpu_type
	   Set	 the   instruction  scheduling	parameters  for	 machine  type
	   cpu_type, but do not	set the	instruction set	or register  set  that
	   the option -mcpu=cpu_type would.

       -msv-mode
	   Generate   code  for	 the  supervisor  mode,	 where	there  are  no
	   restrictions	on the access  to  general  registers.	 This  is  the
	   default.

       -muser-mode
	   Generate  code  for the user	mode, where the	access to some general
	   registers is	forbidden: on the GR5, registers r24 to	r31 cannot  be
	   accessed  in	 this  mode; on	the GR6, only registers	r29 to r31 are
	   affected.

       VMS Options

       These -m	options	are defined for	the VMS	implementations:

       -mvms-return-codes
	   Return VMS condition	codes from "main". The default	is  to	return
	   POSIX-style condition (e.g. error) codes.

       -mdebug-main=prefix
	   Flag	 the  first  routine whose name	starts with prefix as the main
	   routine for the debugger.

       -mmalloc64
	   Default to 64-bit memory allocation routines.

       -mpointer-size=size
	   Set the default size	of pointers. Possible options for size are  32
	   or  short  for 32 bit pointers, 64 or long for 64 bit pointers, and
	   no for supporting only 32 bit pointers.  The	later option  disables
	   "pragma pointer_size".

       VxWorks Options

       The  options  in	 this  section	are  defined  for all VxWorks targets.
       Options specific	to the target  hardware	 are  listed  with  the	 other
       options for that	target.

       -mrtp
	   GCC	can  generate  code  for  both	VxWorks	 kernels and real time
	   processes (RTPs).  This option switches  from  the  former  to  the
	   latter.  It also defines the	preprocessor macro "__RTP__".

       -non-static
	   Link	 an RTP	executable against shared libraries rather than	static
	   libraries.  The options -static and -shared can also	 be  used  for
	   RTPs; -static is the	default.

       -Bstatic
       -Bdynamic
	   These  options are passed down to the linker.  They are defined for
	   compatibility with Diab.

       -Xbind-lazy
	   Enable lazy binding of function calls.  This	option	is  equivalent
	   to -Wl,-z,now and is	defined	for compatibility with Diab.

       -Xbind-now
	   Disable lazy	binding	of function calls.  This option	is the default
	   and is defined for compatibility with Diab.

       x86 Options

       These -m	options	are defined for	the x86	family of computers.

       -march=cpu-type
	   Generate  instructions  for the machine type	cpu-type.  In contrast
	   to -mtune=cpu-type, which merely tunes the generated	code  for  the
	   specified  cpu-type,	 -march=cpu-type  allows  GCC to generate code
	   that	may not	run at all on processors other than the	one indicated.
	   Specifying -march=cpu-type implies  -mtune=cpu-type,	 except	 where
	   noted otherwise.

	   The choices for cpu-type are:

	   native
	       This  selects  the CPU to generate code for at compilation time
	       by determining the processor type  of  the  compiling  machine.
	       Using  -march=native  enables all instruction subsets supported
	       by the local  machine  (hence  the  result  might  not  run  on
	       different   machines).	 Using	 -mtune=native	produces  code
	       optimized for the local machine under the  constraints  of  the
	       selected	instruction set.

	   x86-64
	       A generic CPU with 64-bit extensions.

	   x86-64-v2
	   x86-64-v3
	   x86-64-v4
	       These  choices  for  cpu-type  select  the corresponding	micro-
	       architecture level from the x86-64 psABI.  On ABIs  other  than
	       the  x86-64  psABI  they	 select	 the  same CPU features	as the
	       x86-64 psABI documents for  the	particular  micro-architecture
	       level.

	       Since  these cpu-type values do not have	a corresponding	-mtune
	       setting,	using -march with these	values enables generic tuning.
	       Specific	tuning can be enabled using the	 -mtune=other-cpu-type
	       option with an appropriate other-cpu-type value.

	   i386
	       Original	Intel i386 CPU.

	   i486
	       Intel i486 CPU.	(No scheduling is implemented for this chip.)

	   i586
	   pentium
	       Intel Pentium CPU with no MMX support.

	   lakemont
	       Intel Lakemont MCU, based on Intel Pentium CPU.

	   pentium-mmx
	       Intel   Pentium	MMX  CPU,  based  on  Pentium  core  with  MMX
	       instruction set support.

	   pentiumpro
	       Intel Pentium Pro CPU.

	   i686
	       When used with -march, the Pentium Pro instruction set is used,
	       so the code runs	on all i686  family  chips.   When  used  with
	       -mtune, it has the same meaning as generic.

	   pentium2
	       Intel  Pentium  II  CPU,	 based	on  Pentium  Pro core with MMX
	       instruction set support.

	   pentium3
	   pentium3m
	       Intel Pentium III CPU, based on Pentium Pro core	with  MMX  and
	       SSE instruction set support.

	   pentium-m
	       Intel  Pentium  M;  low-power  version of Intel Pentium III CPU
	       with MMX, SSE  and  SSE2	 instruction  set  support.   Used  by
	       Centrino	notebooks.

	   pentium4
	   pentium4m
	       Intel  Pentium  4  CPU  with  MMX, SSE and SSE2 instruction set
	       support.

	   prescott
	       Improved	version	of Intel Pentium 4 CPU with MMX, SSE, SSE2 and
	       SSE3 instruction	set support.

	   nocona
	       Improved	version	of Intel Pentium 4 CPU with 64-bit extensions,
	       MMX, SSE, SSE2 and SSE3 instruction set support.

	   core2
	       Intel Core 2 CPU	with 64-bit extensions,	MMX, SSE,  SSE2,  SSE3
	       and SSSE3 instruction set support.

	   nehalem
	       Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3,
	       SSSE3, SSE4.1, SSE4.2 and POPCNT	instruction set	support.

	   westmere
	       Intel  Westmere	CPU  with  64-bit  extensions, MMX, SSE, SSE2,
	       SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES	and PCLMUL instruction
	       set support.

	   sandybridge
	       Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE,	 SSE2,
	       SSE3,  SSSE3,  SSE4.1,  SSE4.2,	POPCNT,	 AVX,  AES  and	PCLMUL
	       instruction set support.

	   ivybridge
	       Intel Ivy Bridge	CPU with 64-bit	extensions,  MMX,  SSE,	 SSE2,
	       SSE3,   SSSE3,	SSE4.1,	 SSE4.2,  POPCNT,  AVX,	 AES,  PCLMUL,
	       FSGSBASE, RDRND and F16C	instruction set	support.

	   haswell
	       Intel Haswell CPU with  64-bit  extensions,  MOVBE,  MMX,  SSE,
	       SSE2,  SSE3,  SSSE3,  SSE4.1,  SSE4.2,  POPCNT, AVX, AVX2, AES,
	       PCLMUL, FSGSBASE, RDRND,	FMA, BMI, BMI2	and  F16C  instruction
	       set support.

	   broadwell
	       Intel  Broadwell	 CPU  with 64-bit extensions, MOVBE, MMX, SSE,
	       SSE2, SSE3, SSSE3, SSE4.1,  SSE4.2,  POPCNT,  AVX,  AVX2,  AES,
	       PCLMUL,	FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED ADCX and
	       PREFETCHW instruction set support.

	   skylake
	       Intel Skylake CPU with  64-bit  extensions,  MOVBE,  MMX,  SSE,
	       SSE2,  SSE3,  SSSE3,  SSE4.1,  SSE4.2,  POPCNT, AVX, AVX2, AES,
	       PCLMUL, FSGSBASE, RDRND,	FMA, BMI, BMI2,	 F16C,	RDSEED,	 ADCX,
	       PREFETCHW,   CLFLUSHOPT,	 XSAVEC	 and  XSAVES  instruction  set
	       support.

	   bonnell
	       Intel Bonnell CPU with  64-bit  extensions,  MOVBE,  MMX,  SSE,
	       SSE2, SSE3 and SSSE3 instruction	set support.

	   silvermont
	       Intel  Silvermont  CPU with 64-bit extensions, MOVBE, MMX, SSE,
	       SSE2, SSE3, SSSE3,  SSE4.1,  SSE4.2,  POPCNT,  AES,  PREFETCHW,
	       PCLMUL and RDRND	instruction set	support.

	   goldmont
	       Intel  Goldmont	CPU  with  64-bit extensions, MOVBE, MMX, SSE,
	       SSE2, SSE3, SSSE3,  SSE4.1,  SSE4.2,  POPCNT,  AES,  PREFETCHW,
	       PCLMUL,	RDRND,	XSAVE,	XSAVEC,	 XSAVES, XSAVEOPT and FSGSBASE
	       instruction set support.

	   goldmont-plus
	       Intel Goldmont Plus CPU with  64-bit  extensions,  MOVBE,  MMX,
	       SSE, SSE2, SSE3,	SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PREFETCHW,
	       PCLMUL,	RDRND,	XSAVE,	XSAVEC,	 XSAVES,  XSAVEOPT,  FSGSBASE,
	       PTWRITE,	RDPID, SGX and UMIP instruction	set support.

	   tremont
	       Intel Tremont CPU with  64-bit  extensions,  MOVBE,  MMX,  SSE,
	       SSE2,  SSE3,  SSSE3,  SSE4.1,  SSE4.2,  POPCNT, AES, PREFETCHW,
	       PCLMUL,	RDRND,	XSAVE,	XSAVEC,	 XSAVES,  XSAVEOPT,  FSGSBASE,
	       PTWRITE,	 RDPID,	SGX, UMIP, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B,
	       CLDEMOTE	and WAITPKG instruction	set support.

	   knl Intel Knight's Landing CPU with 64-bit extensions, MOVBE,  MMX,
	       SSE, SSE2, SSE3,	SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
	       PCLMUL,	FSGSBASE,  RDRND,  FMA,	BMI, BMI2, F16C, RDSEED, ADCX,
	       PREFETCHW,  PREFETCHWT1,	 AVX512F,   AVX512PF,	AVX512ER   and
	       AVX512CD	instruction set	support.

	   knm Intel Knights Mill CPU with 64-bit extensions, MOVBE, MMX, SSE,
	       SSE2,  SSE3,  SSSE3,  SSE4.1,  SSE4.2,  POPCNT, AVX, AVX2, AES,
	       PCLMUL, FSGSBASE, RDRND,	FMA, BMI, BMI2,	 F16C,	RDSEED,	 ADCX,
	       PREFETCHW,  PREFETCHWT1,	AVX512F, AVX512PF, AVX512ER, AVX512CD,
	       AVX5124VNNIW, AVX5124FMAPS and AVX512VPOPCNTDQ instruction  set
	       support.

	   skylake-avx512
	       Intel  Skylake  Server  CPU with	64-bit extensions, MOVBE, MMX,
	       SSE, SSE2, SSE3,	SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2,
	       AES, PCLMUL, FSGSBASE, RDRND, FMA,  BMI,	 BMI2,	F16C,  RDSEED,
	       ADCX,  PREFETCHW,  CLFLUSHOPT,  XSAVEC,	XSAVES,	AVX512F, CLWB,
	       AVX512VL,  AVX512BW,  AVX512DQ  and  AVX512CD  instruction  set
	       support.

	   cannonlake
	       Intel Cannonlake	Server CPU with	64-bit extensions, MOVBE, MMX,
	       SSE, SSE2, SSE3,	SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2,
	       AES,  PCLMUL,  FSGSBASE,	 RDRND,	 FMA, BMI, BMI2, F16C, RDSEED,
	       ADCX, PREFETCHW,	CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
	       AVX512BW, AVX512DQ, AVX512CD, AVX512VBMI, AVX512IFMA,  SHA  and
	       UMIP instruction	set support.

	   icelake-client
	       Intel  Icelake  Client  CPU with	64-bit extensions, MOVBE, MMX,
	       SSE, SSE2, SSE3,	SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2,
	       AES, PCLMUL, FSGSBASE, RDRND, FMA,  BMI,	 BMI2,	F16C,  RDSEED,
	       ADCX, PREFETCHW,	CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
	       AVX512BW,  AVX512DQ,  AVX512CD,	AVX512VBMI,  AVX512IFMA,  SHA,
	       CLWB,  UMIP,   RDPID,   GFNI,   AVX512VBMI2,   AVX512VPOPCNTDQ,
	       AVX512BITALG,  AVX512VNNI,  VPCLMULQDQ,	VAES  instruction  set
	       support.

	   icelake-server
	       Intel Icelake Server CPU	with 64-bit  extensions,  MOVBE,  MMX,
	       SSE, SSE2, SSE3,	SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2,
	       AES,  PCLMUL,  FSGSBASE,	 RDRND,	 FMA, BMI, BMI2, F16C, RDSEED,
	       ADCX, PREFETCHW,	CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
	       AVX512BW,  AVX512DQ,  AVX512CD,	AVX512VBMI,  AVX512IFMA,  SHA,
	       CLWB,   UMIP,   RDPID,	GFNI,	AVX512VBMI2,  AVX512VPOPCNTDQ,
	       AVX512BITALG,  AVX512VNNI,  VPCLMULQDQ,	 VAES,	 PCONFIG   and
	       WBNOINVD	instruction set	support.

	   cascadelake
	       Intel  Cascadelake CPU with 64-bit extensions, MOVBE, MMX, SSE,
	       SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES,
	       PCLMUL, FSGSBASE, RDRND,	FMA, BMI, BMI2,	 F16C,	RDSEED,	 ADCX,
	       PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, CLWB, AVX512VL,
	       AVX512BW,  AVX512DQ,  AVX512CD  and  AVX512VNNI instruction set
	       support.

	   cooperlake
	       Intel cooperlake	CPU with 64-bit	extensions, MOVBE,  MMX,  SSE,
	       SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES,
	       PCLMUL,	FSGSBASE,  RDRND,  FMA,	BMI, BMI2, F16C, RDSEED, ADCX,
	       PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, CLWB, AVX512VL,
	       AVX512BW,  AVX512DQ,  AVX512CD,	 AVX512VNNI   and   AVX512BF16
	       instruction set support.

	   tigerlake
	       Intel  Tigerlake	 CPU  with 64-bit extensions, MOVBE, MMX, SSE,
	       SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES,
	       PCLMUL, FSGSBASE, RDRND,	FMA, BMI, BMI2,	 F16C,	RDSEED,	 ADCX,
	       PREFETCHW,   CLFLUSHOPT,	 XSAVEC,  XSAVES,  AVX512F,  AVX512VL,
	       AVX512BW,  AVX512DQ,  AVX512CD,	AVX512VBMI,  AVX512IFMA,  SHA,
	       CLWB,   UMIP,   RDPID,	GFNI,	AVX512VBMI2,  AVX512VPOPCNTDQ,
	       AVX512BITALG, AVX512VNNI, VPCLMULQDQ, VAES, PCONFIG,  WBNOINVD,
	       MOVDIRI,	   MOVDIR64B,	 AVX512VP2INTERSECT    and   KEYLOCKER
	       instruction set support.

	   sapphirerapids
	       Intel sapphirerapids CPU	with 64-bit  extensions,  MOVBE,  MMX,
	       SSE,  SSE2,  SSE3,  SSSE3,  SSE4.1, SSE4.2, POPCNT, CX16, SAHF,
	       FXSR, AVX, XSAVE, PCLMUL, FSGSBASE,  RDRND,  F16C,  AVX2,  BMI,
	       BMI2,  LZCNT,  FMA,  MOVBE,  HLE, RDSEED, ADCX, PREFETCHW, AES,
	       CLFLUSHOPT, XSAVEC, XSAVES, SGX,	AVX512F,  AVX512VL,  AVX512BW,
	       AVX512DQ,   AVX512CD,   PKU,   AVX512VBMI,   AVX512IFMA,	  SHA,
	       AVX512VNNI, GFNI, VAES, AVX512VBMI2  VPCLMULQDQ,	 AVX512BITALG,
	       RDPID,	AVX512VPOPCNTDQ,  PCONFIG,  WBNOINVD,  CLWB,  MOVDIRI,
	       MOVDIR64B,  AVX512VP2INTERSECT,	ENQCMD,	  CLDEMOTE,   PTWRITE,
	       WAITPKG,	  SERIALIZE,   TSXLDTRK,  UINTR,  AMX-BF16,  AMX-TILE,
	       AMX-INT8, AVX-VNNI and AVX512BF16 instruction set support.

	   alderlake
	       Intel Alderlake CPU with	64-bit extensions,  MOVBE,  MMX,  SSE,
	       SSE2,  SSE3,  SSSE3,  SSE4.1,  SSE4.2,  POPCNT, AES, PREFETCHW,
	       PCLMUL,	RDRND,	XSAVE,	XSAVEC,	 XSAVES,  XSAVEOPT,  FSGSBASE,
	       PTWRITE,	 RDPID,	SGX, UMIP, GFNI-SSE, CLWB, MOVDIRI, MOVDIR64B,
	       CLDEMOTE, WAITPKG, ADCX,	 AVX,  AVX2,  BMI,  BMI2,  F16C,  FMA,
	       LZCNT,  PCONFIG,	 PKU, VAES, VPCLMULQDQ,	SERIALIZE, HRESET, KL,
	       WIDEKL and AVX-VNNI instruction set support.

	   rocketlake
	       Intel Rocketlake	CPU with 64-bit	extensions, MOVBE,  MMX,  SSE,
	       SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2, AES,
	       PCLMUL,	FSGSBASE,  RDRND,  FMA,	BMI, BMI2, F16C, RDSEED, ADCX,
	       PREFETCHW,  CLFLUSHOPT,	XSAVEC,	 XSAVES,  AVX512F,   AVX512VL,
	       AVX512BW,  AVX512DQ,  AVX512CD,	AVX512VBMI,  AVX512IFMA,  SHA,
	       CLWB,  UMIP,   RDPID,   GFNI,   AVX512VBMI2,   AVX512VPOPCNTDQ,
	       AVX512BITALG,  AVX512VNNI,  VPCLMULQDQ,	VAES  instruction  set
	       support.

	   k6  AMD K6 CPU with MMX instruction set support.

	   k6-2
	   k6-3
	       Improved	versions of AMD	K6 CPU with MMX	and 3DNow! instruction
	       set support.

	   athlon
	   athlon-tbird
	       AMD Athlon CPU  with  MMX,  3dNOW!,  enhanced  3DNow!  and  SSE
	       prefetch	instructions support.

	   athlon-4
	   athlon-xp
	   athlon-mp
	       Improved	 AMD  Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and
	       full SSE	instruction set	support.

	   k8
	   opteron
	   athlon64
	   athlon-fx
	       Processors based	on the AMD K8 core with	x86-64 instruction set
	       support,	including the AMD Opteron, Athlon 64, and Athlon 64 FX
	       processors.  (This supersets MMX, SSE, SSE2,  3DNow!,  enhanced
	       3DNow! and 64-bit instruction set extensions.)

	   k8-sse3
	   opteron-sse3
	   athlon64-sse3
	       Improved	 versions  of  AMD  K8 cores with SSE3 instruction set
	       support.

	   amdfam10
	   barcelona
	       CPUs based on AMD Family	10h cores with x86-64 instruction  set
	       support.	  (This	supersets MMX, SSE, SSE2, SSE3,	SSE4A, 3DNow!,
	       enhanced	3DNow!,	ABM and	64-bit instruction set extensions.)

	   bdver1
	       CPUs based on AMD Family	15h cores with x86-64 instruction  set
	       support.	  (This	 supersets  FMA4,  AVX,	XOP, LWP, AES, PCLMUL,
	       CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,  SSE4.2,  ABM
	       and 64-bit instruction set extensions.)

	   bdver2
	       AMD  Family  15h	 core  based  CPUs with	x86-64 instruction set
	       support.	 (This supersets BMI, TBM, F16C, FMA, FMA4, AVX,  XOP,
	       LWP,  AES,  PCLMUL,  CX16,  MMX,	SSE, SSE2, SSE3, SSE4A,	SSSE3,
	       SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

	   bdver3
	       AMD Family 15h core based  CPUs	with  x86-64  instruction  set
	       support.	  (This	supersets BMI, TBM, F16C, FMA, FMA4, FSGSBASE,
	       AVX, XOP, LWP, AES, PCLMUL, CX16, MMX, SSE, SSE2, SSE3,	SSE4A,
	       SSSE3,	SSE4.1,	  SSE4.2,   ABM	 and  64-bit  instruction  set
	       extensions.)

	   bdver4
	       AMD Family 15h core based  CPUs	with  x86-64  instruction  set
	       support.	  (This	 supersets  BMI,  BMI2,	 TBM, F16C, FMA, FMA4,
	       FSGSBASE, AVX, AVX2, XOP, LWP, AES, PCLMUL, CX16,  MOVBE,  MMX,
	       SSE,  SSE2,  SSE3, SSE4A, SSSE3,	SSE4.1,	SSE4.2,	ABM and	64-bit
	       instruction set extensions.)

	   znver1
	       AMD Family 17h core based  CPUs	with  x86-64  instruction  set
	       support.	  (This	supersets BMI, BMI2, F16C, FMA,	FSGSBASE, AVX,
	       AVX2, ADCX, RDSEED, MWAITX, SHA,	 CLZERO,  AES,	PCLMUL,	 CX16,
	       MOVBE, MMX, SSE,	SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM,
	       XSAVEC,	XSAVES,	CLFLUSHOPT, POPCNT, and	64-bit instruction set
	       extensions.)

	   znver2
	       AMD Family 17h core based  CPUs	with  x86-64  instruction  set
	       support.	 (This supersets BMI, BMI2, CLWB, F16C,	FMA, FSGSBASE,
	       AVX, AVX2, ADCX,	RDSEED,	 MWAITX,  SHA,	CLZERO,	 AES,  PCLMUL,
	       CX16,  MOVBE,  MMX,  SSE,  SSE2,	 SSE3,	SSE4A,	SSSE3, SSE4.1,
	       SSE4.2,	ABM,  XSAVEC,  XSAVES,	CLFLUSHOPT,   POPCNT,	RDPID,
	       WBNOINVD, and 64-bit instruction	set extensions.)

	   znver3
	       AMD  Family  19h	 core  based  CPUs with	x86-64 instruction set
	       support.	(This supersets	BMI, BMI2, CLWB, F16C, FMA,  FSGSBASE,
	       AVX,  AVX2,  ADCX,  RDSEED,  MWAITX,  SHA, CLZERO, AES, PCLMUL,
	       CX16, MOVBE,  MMX,  SSE,	 SSE2,	SSE3,  SSE4A,  SSSE3,  SSE4.1,
	       SSE4.2,	 ABM,	XSAVEC,	 XSAVES,  CLFLUSHOPT,  POPCNT,	RDPID,
	       WBNOINVD, PKU, VPCLMULQDQ, VAES,	 and  64-bit  instruction  set
	       extensions.)

	   znver4
	       AMD  Family  19h	 core  based  CPUs with	x86-64 instruction set
	       support.	(This supersets	BMI, BMI2, CLWB, F16C, FMA,  FSGSBASE,
	       AVX,  AVX2,  ADCX,  RDSEED,  MWAITX,  SHA, CLZERO, AES, PCLMUL,
	       CX16, MOVBE,  MMX,  SSE,	 SSE2,	SSE3,  SSE4A,  SSSE3,  SSE4.1,
	       SSE4.2,	 ABM,	XSAVEC,	 XSAVES,  CLFLUSHOPT,  POPCNT,	RDPID,
	       WBNOINVD, PKU, VPCLMULQDQ, VAES,	AVX512F, AVX512DQ, AVX512IFMA,
	       AVX512CD,   AVX512BW,   AVX512VL,    AVX512BF16,	   AVX512VBMI,
	       AVX512VBMI2,  AVX512VNNI,  AVX512BITALG,	 AVX512VPOPCNTDQ, GFNI
	       and 64-bit instruction set extensions.)

	   btver1
	       CPUs based on AMD Family	14h cores with x86-64 instruction  set
	       support.	  (This	 supersets MMX,	SSE, SSE2, SSE3, SSSE3,	SSE4A,
	       CX16, ABM and 64-bit instruction	set extensions.)

	   btver2
	       CPUs based on AMD Family	16h cores with x86-64 instruction  set
	       support.	 This  includes	 MOVBE,	 F16C,	BMI, AVX, PCLMUL, AES,
	       SSE4.2, SSE4.1, CX16, ABM, SSE4A, SSSE3,	SSE3, SSE2,  SSE,  MMX
	       and 64-bit instruction set extensions.

	   winchip-c6
	       IDT  WinChip  C6	CPU, dealt in same way as i486 with additional
	       MMX instruction set support.

	   winchip2
	       IDT WinChip 2 CPU, dealt	in same	way as	i486  with  additional
	       MMX and 3DNow!  instruction set support.

	   c3  VIA  C3	CPU  with MMX and 3DNow! instruction set support.  (No
	       scheduling is implemented for this chip.)

	   c3-2
	       VIA C3-2	(Nehemiah/C5XL)	CPU with MMX and SSE  instruction  set
	       support.	 (No scheduling	is implemented for this	chip.)

	   c7  VIA  C7	(Esther)  CPU with MMX,	SSE, SSE2 and SSE3 instruction
	       set support.  (No scheduling is implemented for this chip.)

	   samuel-2
	       VIA Eden	Samuel 2 CPU  with  MMX	 and  3DNow!  instruction  set
	       support.	 (No scheduling	is implemented for this	chip.)

	   nehemiah
	       VIA Eden	Nehemiah CPU with MMX and SSE instruction set support.
	       (No scheduling is implemented for this chip.)

	   esther
	       VIA  Eden  Esther  CPU with MMX,	SSE, SSE2 and SSE3 instruction
	       set support.  (No scheduling is implemented for this chip.)

	   eden-x2
	       VIA  Eden  X2  CPU  with	 x86-64,  MMX,	SSE,  SSE2  and	  SSE3
	       instruction  set	 support.   (No	 scheduling is implemented for
	       this chip.)

	   eden-x4
	       VIA Eden	X4 CPU with  x86-64,  MMX,  SSE,  SSE2,	 SSE3,	SSSE3,
	       SSE4.1,	SSE4.2,	 AVX  and  AVX2	 instruction set support.  (No
	       scheduling is implemented for this chip.)

	   nano
	       Generic VIA Nano	CPU with x86-64,  MMX,	SSE,  SSE2,  SSE3  and
	       SSSE3  instruction  set support.	 (No scheduling	is implemented
	       for this	chip.)

	   nano-1000
	       VIA Nano	1xxx CPU with x86-64, MMX, SSE,	SSE2, SSE3  and	 SSSE3
	       instruction  set	 support.   (No	 scheduling is implemented for
	       this chip.)

	   nano-2000
	       VIA Nano	2xxx CPU with x86-64, MMX, SSE,	SSE2, SSE3  and	 SSSE3
	       instruction  set	 support.   (No	 scheduling is implemented for
	       this chip.)

	   nano-3000
	       VIA Nano	3xxx CPU with x86-64, MMX, SSE,	SSE2, SSE3, SSSE3  and
	       SSE4.1  instruction set support.	 (No scheduling	is implemented
	       for this	chip.)

	   nano-x2
	       VIA Nano	Dual Core CPU with x86-64, MMX,	SSE, SSE2, SSE3, SSSE3
	       and  SSE4.1  instruction	 set  support.	 (No   scheduling   is
	       implemented for this chip.)

	   nano-x4
	       VIA Nano	Quad Core CPU with x86-64, MMX,	SSE, SSE2, SSE3, SSSE3
	       and   SSE4.1   instruction  set	support.   (No	scheduling  is
	       implemented for this chip.)

	   geode
	       AMD Geode embedded processor with MMX  and  3DNow!  instruction
	       set support.

       -mtune=cpu-type
	   Tune	 to  cpu-type  everything applicable about the generated code,
	   except for the ABI and the set of  available	 instructions.	 While
	   picking a specific cpu-type schedules things	appropriately for that
	   particular  chip,  the  compiler  does  not	generate any code that
	   cannot run on the default machine type unless you use a -march=cpu-
	   type	  option.    For   example,   if   GCC	 is   configured   for
	   i686-pc-linux-gnu then -mtune=pentium4 generates code that is tuned
	   for Pentium 4 but still runs	on i686	machines.

	   The	choices	for cpu-type are the same as for -march.  In addition,
	   -mtune supports 2 extra choices for cpu-type:

	   generic
	       Produce code optimized for  the	most  common  IA32/AMD64/EM64T
	       processors.   If	 you know the CPU on which your	code will run,
	       then you	should use the corresponding -mtune or	-march	option
	       instead	of  -mtune=generic.   But,  if you do not know exactly
	       what CPU	users of your application will have, then  you	should
	       use this	option.

	       As new processors are deployed in the marketplace, the behavior
	       of  this	 option	 will  change.	Therefore, if you upgrade to a
	       newer version of	GCC, code generation controlled	by this	option
	       will change to reflect the processors that are most  common  at
	       the time	that version of	GCC is released.

	       There  is no -march=generic option because -march indicates the
	       instruction set the compiler can	use, and there is  no  generic
	       instruction  set	 applicable  to	 all processors.  In contrast,
	       -mtune indicates	the processor (or, in this case, collection of
	       processors) for which the code is optimized.

	   intel
	       Produce code optimized for the most current  Intel  processors,
	       which  are  Haswell and Silvermont for this version of GCC.  If
	       you know	the CPU	on which your code will	run, then  you	should
	       use  the	 corresponding	-mtune	or  -march  option  instead of
	       -mtune=intel.  But,  if	you  want  your	 application  performs
	       better on both Haswell and Silvermont, then you should use this
	       option.

	       As  new	Intel  processors are deployed in the marketplace, the
	       behavior	of this	option will change.  Therefore,	if you upgrade
	       to a newer version of GCC, code generation controlled  by  this
	       option will change to reflect the most current Intel processors
	       at the time that	version	of GCC is released.

	       There  is  no  -march=intel option because -march indicates the
	       instruction set the compiler can	use, and there	is  no	common
	       instruction  set	 applicable  to	 all processors.  In contrast,
	       -mtune indicates	the processor (or, in this case, collection of
	       processors) for which the code is optimized.

       -mcpu=cpu-type
	   A deprecated	synonym	for -mtune.

       -mfpmath=unit
	   Generate floating-point arithmetic for  selected  unit  unit.   The
	   choices for unit are:

	   387 Use  the	standard 387 floating-point coprocessor	present	on the
	       majority	of chips and emulated otherwise.  Code	compiled  with
	       this  option runs almost	everywhere.  The temporary results are
	       computed	in 80-bit precision instead of the precision specified
	       by the type, resulting in slightly different  results  compared
	       to  most	 of  other chips.  See -ffloat-store for more detailed
	       description.

	       This is the default choice for non-Darwin x86-32	targets.

	   sse Use scalar  floating-point  instructions	 present  in  the  SSE
	       instruction  set.  This instruction set is supported by Pentium
	       III and newer chips, and	in the AMD line	by Athlon-4, Athlon XP
	       and  Athlon  MP	chips.	 The  earlier  version	of   the   SSE
	       instruction set supports	only single-precision arithmetic, thus
	       the  double  and	 extended-precision  arithmetic	are still done
	       using 387.  A later version, present only in Pentium 4 and  AMD
	       x86-64 chips, supports double-precision arithmetic too.

	       For the x86-32 compiler,	you must use -march=cpu-type, -msse or
	       -msse2  switches	 to enable SSE extensions and make this	option
	       effective.  For	the  x86-64  compiler,	these  extensions  are
	       enabled by default.

	       The  resulting  code  should  be	 considerably  faster  in  the
	       majority	of cases and avoid the numerical instability  problems
	       of  387	code,  but  may	 break some existing code that expects
	       temporaries to be 80 bits.

	       This is the default choice  for	the  x86-64  compiler,	Darwin
	       x86-32  targets,	and the	default	choice for x86-32 targets with
	       the SSE2	instruction set	when -ffast-math is enabled.

	   sse,387
	   sse+387
	   both
	       Attempt	to  utilize  both  instruction	sets  at  once.	  This
	       effectively  doubles  the amount	of available registers,	and on
	       chips with  separate  execution	units  for  387	 and  SSE  the
	       execution  resources  too.  Use this option with	care, as it is
	       still experimental, because the GCC register allocator does not
	       model separate functional units	well,  resulting  in  unstable
	       performance.

       -masm=dialect
	   Output  assembly instructions using selected	dialect.  Also affects
	   which dialect is used for basic "asm" and extended "asm". Supported
	   choices (in dialect order) are att or intel.	The  default  is  att.
	   Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
	   Control  whether  or	 not  the  compiler  uses  IEEE	floating-point
	   comparisons.	 These correctly handle	the case where the result of a
	   comparison is unordered.

       -m80387
       -mhard-float
	   Generate output containing 80387 instructions for floating point.

       -mno-80387
       -msoft-float
	   Generate output containing library calls for	floating point.

	   Warning: the	requisite libraries are	not part of GCC.  Normally the
	   facilities of the machine's usual C compiler	 are  used,  but  this
	   cannot  be  done directly in	cross-compilation.  You	must make your
	   own arrangements to provide suitable	library	functions  for	cross-
	   compilation.

	   On  machines	where a	function returns floating-point	results	in the
	   80387 register stack, some floating-point opcodes  may  be  emitted
	   even	if -msoft-float	is used.

       -mno-fp-ret-in-387
	   Do not use the FPU registers	for return values of functions.

	   The	usual  calling convention has functions	return values of types
	   "float" and "double"	in an FPU register, even if there is  no  FPU.
	   The idea is that the	operating system should	emulate	an FPU.

	   The	option -mno-fp-ret-in-387 causes such values to	be returned in
	   ordinary CPU	registers instead.

       -mno-fancy-math-387
	   Some	387 emulators do not  support  the  "sin",  "cos"  and	"sqrt"
	   instructions	 for the 387.  Specify this option to avoid generating
	   those  instructions.	  This	option	is  overridden	 when	-march
	   indicates  that  the	 target	 CPU  always  has  an  FPU  and	so the
	   instruction does not	need emulation.	 These	instructions  are  not
	   generated  unless  you  also	 use  the  -funsafe-math-optimizations
	   switch.

       -malign-double
       -mno-align-double
	   Control whether GCC aligns "double",	"long double", and "long long"
	   variables on	a two-word boundary or a one-word boundary.   Aligning
	   "double"  variables	on a two-word boundary produces	code that runs
	   somewhat faster on a	Pentium	at the expense of more memory.

	   On x86-64, -malign-double is	enabled	by default.

	   Warning:  if	 you  use  the	 -malign-double	  switch,   structures
	   containing  the  above  types  are  aligned	differently  than  the
	   published  application  binary  interface  specifications  for  the
	   x86-32  and	are  not  binary  compatible  with  structures in code
	   compiled without that switch.

       -m96bit-long-double
       -m128bit-long-double
	   These switches control the size of "long double" type.  The	x86-32
	   application	binary	interface specifies the	size to	be 96 bits, so
	   -m96bit-long-double is the default in 32-bit	mode.

	   Modern architectures	(Pentium and newer) prefer "long double" to be
	   aligned to an 8- or 16-byte	boundary.   In	arrays	or  structures
	   conforming  to  the	ABI,  this  is	not  possible.	 So specifying
	   -m128bit-long-double	aligns "long double" to	a 16-byte boundary  by
	   padding the "long double" with an additional	32-bit zero.

	   In  the x86-64 compiler, -m128bit-long-double is the	default	choice
	   as its ABI specifies	that  "long  double"  is  aligned  on  16-byte
	   boundary.

	   Notice  that	 neither  of  these options enable any extra precision
	   over	the x87	standard of 80 bits for	a "long	double".

	   Warning: if you override the	default	value  for  your  target  ABI,
	   this	 changes  the  size  of	structures and arrays containing "long
	   double" variables,  as  well	 as  modifying	the  function  calling
	   convention  for functions taking "long double".  Hence they are not
	   binary-compatible with code compiled	without	that switch.

       -mlong-double-64
       -mlong-double-80
       -mlong-double-128
	   These switches control the size of "long double" type. A size of 64
	   bits	makes the "long	double"	type equivalent	to the "double"	 type.
	   This	 is  the  default  for 32-bit Bionic C library.	 A size	of 128
	   bits	makes the "long	double"	type equivalent	 to  the  "__float128"
	   type. This is the default for 64-bit	Bionic C library.

	   Warning:  if	 you  override	the default value for your target ABI,
	   this	changes	the size of structures	and  arrays  containing	 "long
	   double"  variables,	as  well  as  modifying	 the  function calling
	   convention for functions taking "long double".  Hence they are  not
	   binary-compatible with code compiled	without	that switch.

       -malign-data=type
	   Control  how	 GCC  aligns variables.	 Supported values for type are
	   compat uses increased alignment value compatible uses GCC  4.8  and
	   earlier,  abi  uses	alignment value	as specified by	the psABI, and
	   cacheline uses increased alignment value to match  the  cache  line
	   size.  compat is the	default.

       -mlarge-data-threshold=threshold
	   When	  -mcmodel=medium  is  specified,  data	 objects  larger  than
	   threshold are placed	in the large data section.  This value must be
	   the same across all objects linked into the binary, and defaults to
	   65535.

       -mrtd
	   Use a different function-calling  convention,  in  which  functions
	   that	 take  a  fixed	 number	of arguments return with the "ret num"
	   instruction,	which pops  their  arguments  while  returning.	  This
	   saves  one  instruction in the caller since there is	no need	to pop
	   the arguments there.

	   You can specify that	an individual function	is  called  with  this
	   calling  sequence  with  the	function attribute "stdcall".  You can
	   also	override the -mrtd option  by  using  the  function  attribute
	   "cdecl".

	   Warning:  this  calling  convention	is  incompatible  with the one
	   normally used on Unix, so you cannot	use it if  you	need  to  call
	   libraries compiled with the Unix compiler.

	   Also,  you  must provide function prototypes	for all	functions that
	   take	variable numbers of arguments (including "printf");  otherwise
	   incorrect code is generated for calls to those functions.

	   In  addition,  seriously  incorrect	code  results  if  you	call a
	   function with too many arguments.  (Normally, extra	arguments  are
	   harmlessly ignored.)

       -mregparm=num
	   Control  how	many registers are used	to pass	integer	arguments.  By
	   default, no registers are used to pass arguments,  and  at  most  3
	   registers  can  be  used.   You  can	 control  this	behavior for a
	   specific function by	using the function attribute "regparm".

	   Warning: if you use this switch, and	num is nonzero,	then you  must
	   build  all  modules	with  the same value, including	any libraries.
	   This	includes the system libraries and startup modules.

       -msseregparm
	   Use SSE register passing conventions	for float and double arguments
	   and return values.  You can control this behavior  for  a  specific
	   function by using the function attribute "sseregparm".

	   Warning:  if	 you  use  this	switch then you	must build all modules
	   with	the same value,	including any libraries.   This	 includes  the
	   system libraries and	startup	modules.

       -mvect8-ret-in-mem
	   Return  8-byte vectors in memory instead of MMX registers.  This is
	   the default on VxWorks to match the ABI of the Sun Studio compilers
	   until version 12.  Only use this  option  if	 you  need  to	remain
	   compatible  with  existing code produced by those previous compiler
	   versions or older versions of GCC.

       -mpc32
       -mpc64
       -mpc80
	   Set 80387 floating-point precision to 32,  64  or  80  bits.	  When
	   -mpc32  is specified, the significands of results of	floating-point
	   operations are rounded to 24	bits (single precision); -mpc64	rounds
	   the significands of results of floating-point operations to 53 bits
	   (double precision) and -mpc80 rounds	the significands of results of
	   floating-point operations to	64 bits	(extended  double  precision),
	   which  is  the  default.   When this	option is used,	floating-point
	   operations in higher	precisions are not available to	the programmer
	   without setting the FPU control word	explicitly.

	   Setting the rounding	of floating-point operations to	less than  the
	   default  80	bits can speed some programs by	2% or more.  Note that
	   some	mathematical libraries assume that extended-precision (80-bit)
	   floating-point operations are enabled by default; routines in  such
	   libraries  could  suffer  significant  loss	of accuracy, typically
	   through so-called "catastrophic cancellation", when this option  is
	   used	to set the precision to	less than extended precision.

       -mdaz-ftz
	   The	flush-to-zero  (FTZ) and denormals-are-zero (DAZ) flags	in the
	   MXCSR register are used to control floating-point  calculations.SSE
	   and AVX instructions	including scalar and vector instructions could
	   benefit  from  enabling  the	 FTZ  and  DAZ flags when -mdaz-ftz is
	   specified. Don't set	FTZ/DAZ	flags when -mno-daz-ftz	is specified.

       -mstackrealign
	   Realign the stack at	entry.	On the x86, the	-mstackrealign	option
	   generates an	alternate prologue and epilogue	that realigns the run-
	   time	 stack	if  necessary.	This supports mixing legacy codes that
	   keep	4-byte stack alignment with modern  codes  that	 keep  16-byte
	   stack  alignment  for  SSE  compatibility.	See also the attribute
	   "force_align_arg_pointer", applicable to individual functions.

       -mpreferred-stack-boundary=num
	   Attempt to keep the stack boundary aligned to a  2  raised  to  num
	   byte	boundary.  If -mpreferred-stack-boundary is not	specified, the
	   default is 4	(16 bytes or 128 bits).

	   Warning:  When generating code for the x86-64 architecture with SSE
	   extensions disabled,	-mpreferred-stack-boundary=3 can  be  used  to
	   keep	 the  stack boundary aligned to	8 byte boundary.  Since	x86-64
	   ABI require 16 byte stack alignment,	this is	ABI  incompatible  and
	   intended  to	be used	in controlled environment where	stack space is
	   important  limitation.   This  option  leads	 to  wrong  code  when
	   functions  compiled with 16 byte stack alignment (such as functions
	   from	a standard library) are	called with misaligned stack.  In this
	   case, SSE instructions may lead to misaligned memory	access	traps.
	   In addition,	variable arguments are handled incorrectly for 16 byte
	   aligned  objects  (including	x87 long double	and __int128), leading
	   to	wrong	results.    You	  must	 build	 all   modules	  with
	   -mpreferred-stack-boundary=3,   including   any   libraries.	  This
	   includes the	system libraries and startup modules.

       -mincoming-stack-boundary=num
	   Assume the incoming stack is	aligned	to a  2	 raised	 to  num  byte
	   boundary.   If  -mincoming-stack-boundary is	not specified, the one
	   specified by	-mpreferred-stack-boundary is used.

	   On Pentium and Pentium  Pro,	 "double"  and	"long  double"	values
	   should  be  aligned	to  an 8-byte boundary (see -malign-double) or
	   suffer significant run time performance penalties.  On Pentium III,
	   the Streaming SIMD Extension	(SSE) data type	"__m128" may not  work
	   properly if it is not 16-byte aligned.

	   To  ensure  proper alignment	of this	values on the stack, the stack
	   boundary must be as aligned as that required	by any value stored on
	   the stack.  Further,	every function must be generated such that  it
	   keeps  the  stack aligned.  Thus calling a function compiled	with a
	   higher preferred stack boundary from	a  function  compiled  with  a
	   lower preferred stack boundary most likely misaligns	the stack.  It
	   is  recommended  that  libraries  that use callbacks	always use the
	   default setting.

	   This	extra alignment	does consume extra stack space,	and  generally
	   increases  code size.  Code that is sensitive to stack space	usage,
	   such	as embedded systems and	operating system kernels, may want  to
	   reduce the preferred	alignment to -mpreferred-stack-boundary=2.

       -mmmx
       -msse
       -msse2
       -msse3
       -mssse3
       -msse4
       -msse4a
       -msse4.1
       -msse4.2
       -mavx
       -mavx2
       -mavx512f
       -mavx512pf
       -mavx512er
       -mavx512cd
       -mavx512vl
       -mavx512bw
       -mavx512dq
       -mavx512ifma
       -mavx512vbmi
       -msha
       -maes
       -mpclmul
       -mclflushopt
       -mclwb
       -mfsgsbase
       -mptwrite
       -mrdrnd
       -mf16c
       -mfma
       -mpconfig
       -mwbnoinvd
       -mfma4
       -mprfchw
       -mrdpid
       -mprefetchwt1
       -mrdseed
       -msgx
       -mxop
       -mlwp
       -m3dnow
       -m3dnowa
       -mpopcnt
       -mabm
       -madx
       -mbmi
       -mbmi2
       -mlzcnt
       -mfxsr
       -mxsave
       -mxsaveopt
       -mxsavec
       -mxsaves
       -mrtm
       -mhle
       -mtbm
       -mmwaitx
       -mclzero
       -mpku
       -mavx512vbmi2
       -mavx512bf16
       -mgfni
       -mvaes
       -mwaitpkg
       -mvpclmulqdq
       -mavx512bitalg
       -mmovdiri
       -mmovdir64b
       -menqcmd
       -muintr
       -mtsxldtrk
       -mavx512vpopcntdq
       -mavx512vp2intersect
       -mavx5124fmaps
       -mavx512vnni
       -mavxvnni
       -mavx5124vnniw
       -mcldemote
       -mserialize
       -mamx-tile
       -mamx-int8
       -mamx-bf16
       -mhreset
       -mkl
       -mwidekl
	   These  switches  enable  the	 use  of instructions in the MMX, SSE,
	   SSE2, SSE3, SSSE3, SSE4, SSE4A, SSE4.1, SSE4.2, AVX,	AVX2, AVX512F,
	   AVX512PF,  AVX512ER,	 AVX512CD,   AVX512VL,	 AVX512BW,   AVX512DQ,
	   AVX512IFMA,	 AVX512VBMI,   SHA,  AES,  PCLMUL,  CLFLUSHOPT,	 CLWB,
	   FSGSBASE, PTWRITE,  RDRND,  F16C,  FMA,  PCONFIG,  WBNOINVD,	 FMA4,
	   PREFETCHW,  RDPID,  PREFETCHWT1,  RDSEED,  SGX,  XOP,  LWP, 3DNow!,
	   enhanced 3DNow!, POPCNT, ABM, ADX, BMI, BMI2, LZCNT,	 FXSR,	XSAVE,
	   XSAVEOPT,  XSAVEC,  XSAVES,	RTM,  HLE,  TBM,  MWAITX, CLZERO, PKU,
	   AVX512VBMI2,	 GFNI,	VAES,	WAITPKG,   VPCLMULQDQ,	 AVX512BITALG,
	   MOVDIRI,    MOVDIR64B,    AVX512BF16,    ENQCMD,   AVX512VPOPCNTDQ,
	   AVX5124FMAPS, AVX512VNNI, AVX5124VNNIW, SERIALIZE,  UINTR,  HRESET,
	   AMXTILE, AMXINT8, AMXBF16, KL, WIDEKL, AVXVNNI or CLDEMOTE extended
	   instruction	sets. Each has a corresponding -mno- option to disable
	   use of these	instructions.

	   These extensions are	also available as built-in functions: see  x86
	   Built-in  Functions,	 for  details  of  the	functions  enabled and
	   disabled by these switches.

	   To generate SSE/SSE2	instructions automatically from	floating-point
	   code	(as opposed to 387 instructions), see -mfpmath=sse.

	   GCC depresses SSEx instructions when	-mavx  is  used.  Instead,  it
	   generates  new  AVX	instructions  or  AVX equivalence for all SSEx
	   instructions	when needed.

	   These options enable	GCC to	use  these  extended  instructions  in
	   generated  code,  even  without  -mfpmath=sse.   Applications  that
	   perform run-time CPU	detection must compile separate	files for each
	   supported  architecture,   using   the   appropriate	  flags.    In
	   particular,	the  file  containing the CPU detection	code should be
	   compiled without these options.

       -mdump-tune-features
	   This	option instructs GCC to	dump the names of the x86  performance
	   tuning  features  and  default  settings.  The names	can be used in
	   -mtune-ctrl=feature-list.

       -mtune-ctrl=feature-list
	   This	option is used to do fine grain	control	of x86 code generation
	   features.  feature-list is a	comma separated	list of	feature	names.
	   See also  -mdump-tune-features.  When  specified,  the  feature  is
	   turned  on  if  it  is not preceded with ^, otherwise, it is	turned
	   off.	 -mtune-ctrl=feature-list  is  intended	 to  be	 used  by  GCC
	   developers.	Using it may lead to code paths	not covered by testing
	   and can potentially result in compiler ICEs or runtime errors.

       -mno-default
	   This	option instructs GCC to	turn off  all  tunable	features.  See
	   also	-mtune-ctrl=feature-list and -mdump-tune-features.

       -mcld
	   This	 option	 instructs  GCC	 to  emit  a  "cld" instruction	in the
	   prologue  of	 functions  that  use  string  instructions.	String
	   instructions	 depend	on the DF flag to select between autoincrement
	   or autodecrement mode.  While the ABI specifies the DF flag	to  be
	   cleared  on	function  entry,  some	operating systems violate this
	   specification by not	 clearing  the	DF  flag  in  their  exception
	   dispatchers.	 The exception handler can be invoked with the DF flag
	   set,	 which	leads to wrong direction mode when string instructions
	   are used.  This option can be enabled  by  default  on  32-bit  x86
	   targets  by configuring GCC with the	--enable-cld configure option.
	   Generation  of  "cld"  instructions	can  be	 suppressed  with  the
	   -mno-cld compiler option in this case.

       -mvzeroupper
	   This	option instructs GCC to	emit a "vzeroupper" instruction	before
	   a  transfer of control flow out of the function to minimize the AVX
	   to SSE transition penalty as	well as	remove unnecessary "zeroupper"
	   intrinsics.

       -mprefer-avx128
	   This	option instructs GCC to	use 128-bit AVX	 instructions  instead
	   of 256-bit AVX instructions in the auto-vectorizer.

       -mprefer-vector-width=opt
	   This	  option   instructs  GCC  to  use  opt-bit  vector  width  in
	   instructions	instead	of default on the selected platform.

	   none
	       No extra	limitations applied to GCC other than defined  by  the
	       selected	platform.

	   128 Prefer 128-bit vector width for instructions.

	   256 Prefer 256-bit vector width for instructions.

	   512 Prefer 512-bit vector width for instructions.

       -mcx16
	   This	 option	 enables  GCC to generate "CMPXCHG16B" instructions in
	   64-bit code to implement compare-and-exchange operations on 16-byte
	   aligned 128-bit objects.  This is useful for	atomic updates of data
	   structures exceeding	one machine word in size.  The	compiler  uses
	   this	 instruction  to  implement  __sync  Builtins.	 However,  for
	   __atomic Builtins operating on 128-bit integers, a library call  is
	   always used.

       -msahf
	   This	 option	 enables  generation  of "SAHF"	instructions in	64-bit
	   code.  Early	Intel Pentium 4	CPUs with Intel	64 support,  prior  to
	   the	introduction of	Pentium	4 G1 step in December 2005, lacked the
	   "LAHF" and "SAHF" instructions which	are supported by AMD64.	 These
	   are load and	store instructions, respectively, for  certain	status
	   flags.   In 64-bit mode, the	"SAHF" instruction is used to optimize
	   "fmod", "drem",  and	 "remainder"  built-in	functions;  see	 Other
	   Builtins for	details.

       -mmovbe
	   This	 option	 enables  use  of the "movbe" instruction to implement
	   "__builtin_bswap32" and "__builtin_bswap64".

       -mshstk
	   The -mshstk option enables shadow stack built-in functions from x86
	   Control-flow	Enforcement Technology (CET).

       -mcrc32
	   This	option enables	built-in  functions  "__builtin_ia32_crc32qi",
	   "__builtin_ia32_crc32hi",	    "__builtin_ia32_crc32si"	   and
	   "__builtin_ia32_crc32di"   to   generate   the   "crc32"    machine
	   instruction.

       -mmwait
	   This	 option	 enables  built-in functions "__builtin_ia32_monitor",
	   and "__builtin_ia32_mwait" to generate the  "monitor"  and  "mwait"
	   machine instructions.

       -mrecip
	   This	 option	enables	use of "RCPSS" and "RSQRTSS" instructions (and
	   their vectorized variants "RCPPS" and "RSQRTPS") with an additional
	   Newton-Raphson step to increase precision instead  of  "DIVSS"  and
	   "SQRTSS"  (and  their  vectorized  variants)	 for  single-precision
	   floating-point arguments.  These instructions  are  generated  only
	   when	  -funsafe-math-optimizations	is   enabled   together	  with
	   -ffinite-math-only and -fno-trapping-math.	Note  that  while  the
	   throughput  of  the	sequence  is higher than the throughput	of the
	   non-reciprocal instruction, the precision of	the  sequence  can  be
	   decreased  by  up  to  2  ulp  (i.e.	 the  inverse  of  1.0	equals
	   0.99999994).

	   Note	that GCC implements "1.0f/sqrtf(x)" in terms of	"RSQRTSS"  (or
	   "RSQRTPS")	already	  with	 -ffast-math   (or  the	 above	option
	   combination), and doesn't need -mrecip.

	   Also	note that GCC emits the	above sequence with additional Newton-
	   Raphson step	for vectorized single-float  division  and  vectorized
	   "sqrtf(x)"	already	  with	 -ffast-math   (or  the	 above	option
	   combination), and doesn't need -mrecip.

       -mrecip=opt
	   This	option controls	which reciprocal estimate instructions may  be
	   used.   opt	is  a  comma-separated	list  of options, which	may be
	   preceded by a ! to invert the option:

	   all Enable all estimate instructions.

	   default
	       Enable the default instructions,	equivalent to -mrecip.

	   none
	       Disable all estimate instructions, equivalent to	-mno-recip.

	   div Enable the approximation	for scalar division.

	   vec-div
	       Enable the approximation	for vectorized division.

	   sqrt
	       Enable the approximation	for scalar square root.

	   vec-sqrt
	       Enable the approximation	for vectorized square root.

	   So, for example, -mrecip=all,!sqrt enables all  of  the  reciprocal
	   approximations, except for square root.

       -mveclibabi=type
	   Specifies  the  ABI type to use for vectorizing intrinsics using an
	   external library.  Supported	values for type	are svml for the Intel
	   short vector	math library and acml for the AMD math	core  library.
	   To	  use	  this	   option,     both    -ftree-vectorize	   and
	   -funsafe-math-optimizations have to be enabled, and an SVML or ACML
	   ABI-compatible library must be specified at link time.

	   GCC currently emits calls to	"vmldExp2",  "vmldLn2",	 "vmldLog102",
	   "vmldPow2",	"vmldTanh2",  "vmldTan2",  "vmldAtan2",	 "vmldAtanh2",
	   "vmldCbrt2",	"vmldSinh2",  "vmldSin2",  "vmldAsinh2",  "vmldAsin2",
	   "vmldCosh2",	 "vmldCos2",  "vmldAcosh2",  "vmldAcos2",  "vmlsExp4",
	   "vmlsLn4",  "vmlsLog104",  "vmlsPow4",   "vmlsTanh4",   "vmlsTan4",
	   "vmlsAtan4",	 "vmlsAtanh4",	"vmlsCbrt4",  "vmlsSinh4", "vmlsSin4",
	   "vmlsAsinh4", "vmlsAsin4",  "vmlsCosh4",  "vmlsCos4",  "vmlsAcosh4"
	   and	  "vmlsAcos4"	 for	corresponding	function   type	  when
	   -mveclibabi=svml   is   used,   and	 "__vrd2_sin",	 "__vrd2_cos",
	   "__vrd2_exp",    "__vrd2_log",    "__vrd2_log2",    "__vrd2_log10",
	   "__vrs4_sinf",   "__vrs4_cosf",    "__vrs4_expf",	"__vrs4_logf",
	   "__vrs4_log2f",   "__vrs4_log10f"   and   "__vrs4_powf"   for   the
	   corresponding function type when -mveclibabi=acml is	used.

       -mabi=name
	   Generate code for the specified  calling  convention.   Permissible
	   values  are	sysv  for the ABI used on GNU/Linux and	other systems,
	   and ms for the Microsoft ABI.  The default is to use	the  Microsoft
	   ABI	when targeting Microsoft Windows and the SysV ABI on all other
	   systems.  You can control this behavior for specific	 functions  by
	   using the function attributes "ms_abi" and "sysv_abi".

       -mforce-indirect-call
	   Force  all  calls  to functions to be indirect. This	is useful when
	   using Intel Processor Trace where it	generates more precise	timing
	   information for function calls.

       -mmanual-endbr
	   Insert  ENDBR instruction at	function entry only via	the "cf_check"
	   function attribute. This  is	 useful	 when  used  with  the	option
	   -fcf-protection=branch  to  control ENDBR insertion at the function
	   entry.

       -mcall-ms2sysv-xlogues
	   Due to differences in 64-bit	ABIs, any Microsoft ABI	function  that
	   calls a System V ABI	function must consider RSI, RDI	and XMM6-15 as
	   clobbered.	By  default,  the  code	for saving and restoring these
	   registers is	emitted	inline,	resulting in fairly lengthy  prologues
	   and	epilogues.   Using  -mcall-ms2sysv-xlogues emits prologues and
	   epilogues that use stubs in the static portion of libgcc to perform
	   these saves and restores, thus reducing function size at  the  cost
	   of a	few extra instructions.

       -mtls-dialect=type
	   Generate  code to access thread-local storage using the gnu or gnu2
	   conventions.	  gnu  is  the	conservative  default;	gnu2  is  more
	   efficient,  but  it may add compile-	and run-time requirements that
	   cannot be satisfied on all systems.

       -mpush-args
       -mno-push-args
	   Use PUSH operations to store	outgoing parameters.  This  method  is
	   shorter and usually equally fast as method using SUB/MOV operations
	   and	is enabled by default.	In some	cases disabling	it may improve
	   performance	 because   of	improved   scheduling	and    reduced
	   dependencies.

       -maccumulate-outgoing-args
	   If  enabled,	 the  maximum  amount  of  space required for outgoing
	   arguments is	computed in the	function prologue.  This is faster  on
	   most	  modern   CPUs	 because  of  reduced  dependencies,  improved
	   scheduling  and  reduced  stack  usage  when	 the  preferred	 stack
	   boundary  is	not equal to 2.	 The drawback is a notable increase in
	   code	size.  This switch implies -mno-push-args.

       -mthreads
	   Support thread-safe exception handling  on  MinGW.	Programs  that
	   rely	 on  thread-safe  exception handling must compile and link all
	   code	with the -mthreads option.  When compiling, -mthreads  defines
	   -D_MT;  when	 linking,  it links in a special thread	helper library
	   -lmingwthrd which cleans up per-thread exception-handling data.

       -mms-bitfields
       -mno-ms-bitfields
	   Enable/disable  bit-field  layout  compatible   with	  the	native
	   Microsoft Windows compiler.

	   If  "packed"	 is used on a structure, or if bit-fields are used, it
	   may be that the Microsoft ABI lays out  the	structure  differently
	   than	 the  way  GCC normally	does.  Particularly when moving	packed
	   data	between	functions compiled with	GCC and	the  native  Microsoft
	   compiler (either via	function call or as data in a file), it	may be
	   necessary to	access either format.

	   This	 option	 is  enabled by	default	for Microsoft Windows targets.
	   This	behavior can also be controlled	locally	by use of variable  or
	   type	attributes.  For more information, see x86 Variable Attributes
	   and x86 Type	Attributes.

	   The	Microsoft structure layout algorithm is	fairly simple with the
	   exception of	the bit-field packing.	The padding and	 alignment  of
	   members  of	structures  and	 whether  a  bit-field	can straddle a
	   storage-unit	boundary are determine by these	rules:

	   1. Structure	members	are stored sequentially	in the order in	which
	   they	are
	       declared: the first member has the lowest  memory  address  and
	       the last	member the highest.

	   2. Every data object	has an alignment requirement.  The alignment
	   requirement
	       for  all	 data  except structures, unions, and arrays is	either
	       the size	of the object or the current packing  size  (specified
	       with  either  the  "aligned"  attribute	or the "pack" pragma),
	       whichever is less.  For structures,  unions,  and  arrays,  the
	       alignment  requirement  is the largest alignment	requirement of
	       its members.  Every object is allocated an offset so that:

		       offset %	alignment_requirement == 0

	   3. Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte
	   allocation
	       unit if the integral types are the same size and	 if  the  next
	       bit-field   fits	 into  the  current  allocation	 unit  without
	       crossing	 the  boundary	imposed	 by   the   common   alignment
	       requirements of the bit-fields.

	   MSVC	interprets zero-length bit-fields in the following ways:

	   1. If a zero-length bit-field is inserted between two bit-fields
	   that
	       are normally coalesced, the bit-fields are not coalesced.

	       For example:

		       struct
			{
			  unsigned long	bf_1 : 12;
			  unsigned long	: 0;
			  unsigned long	bf_2 : 12;
			} t1;

	       The size	of "t1"	is 8 bytes with	the zero-length	bit-field.  If
	       the  zero-length	bit-field were removed,	"t1"'s size would be 4
	       bytes.

	   2. If a zero-length bit-field is inserted after a bit-field,	"foo",
	   and the
	       alignment of the	zero-length  bit-field	is  greater  than  the
	       member  that follows it,	"bar", "bar" is	aligned	as the type of
	       the zero-length bit-field.

	       For example:

		       struct
			{
			  char foo : 4;
			  short	: 0;
			  char bar;
			} t2;

		       struct
			{
			  char foo : 4;
			  short	: 0;
			  double bar;
			} t3;

	       For "t2", "bar" is placed at offset 2, rather  than  offset  1.
	       Accordingly,  the size of "t2" is 4.  For "t3", the zero-length
	       bit-field does not affect the  alignment	 of  "bar"  or,	 as  a
	       result, the size	of the structure.

	       Taking	this  into  account,  it  is  important	 to  note  the
	       following:

	       1. If a zero-length bit-field follows a normal bit-field, the
	       type of the
		   zero-length bit-field  may  affect  the  alignment  of  the
		   structure  as  whole.  For  example,	 "t2"  has a size of 4
		   bytes, since	the zero-length	 bit-field  follows  a	normal
		   bit-field, and is of	type short.

	       2. Even if a zero-length	bit-field is not followed by a normal
	       bit-field, it may
		   still affect	the alignment of the structure:

			   struct
			    {
			      char foo : 6;
			      long : 0;
			    } t4;

		   Here, "t4" takes up 4 bytes.

	   3. Zero-length bit-fields following non-bit-field members are
	   ignored:
		       struct
			{
			  char foo;
			  long : 0;
			  char bar;
			} t5;

	       Here, "t5" takes	up 2 bytes.

       -mno-align-stringops
	   Do  not  align  the destination of inlined string operations.  This
	   switch reduces code size  and  improves  performance	 in  case  the
	   destination is already aligned, but GCC doesn't know	about it.

       -minline-all-stringops
	   By  default GCC inlines string operations only when the destination
	   is known to be aligned to least a 4-byte  boundary.	 This  enables
	   more	 inlining and increases	code size, but may improve performance
	   of code that	depends	 on  fast  "memcpy"  and  "memset"  for	 short
	   lengths.   The  option enables inline expansion of "strlen" for all
	   pointer alignments.

       -minline-stringops-dynamically
	   For string operations of unknown size,  use	run-time  checks  with
	   inline code for small blocks	and a library call for large blocks.

       -mstringop-strategy=alg
	   Override   the  internal  decision  heuristic  for  the  particular
	   algorithm to	use  for  inlining  string  operations.	  The  allowed
	   values for alg are:

	   rep_byte
	   rep_4byte
	   rep_8byte
	       Expand using i386 "rep" prefix of the specified size.

	   byte_loop
	   loop
	   unrolled_loop
	       Expand into an inline loop.

	   libcall
	       Always use a library call.

       -mmemcpy-strategy=strategy
	   Override   the   internal   decision	  heuristic   to   decide   if
	   "__builtin_memcpy" should be	inlined	and what inline	 algorithm  to
	   use when the	expected size of the copy operation is known. strategy
	   is a	comma-separated	list of	alg:max_size:dest_align	triplets.  alg
	   is  specified  in  -mstringop-strategy,  max_size specifies the max
	   byte	size with which	inline algorithm alg is	allowed.  For the last
	   triplet, the	max_size must be "-1". The max_size of the triplets in
	   the list must be specified in increasing order.  The	 minimal  byte
	   size	 for  alg is 0 for the first triplet and "max_size + 1"	of the
	   preceding range.

       -mmemset-strategy=strategy
	   The option is similar to -mmemcpy-strategy= except that  it	is  to
	   control "__builtin_memset" expansion.

       -momit-leaf-frame-pointer
	   Don't  keep	the  frame  pointer  in	a register for leaf functions.
	   This	avoids the instructions	to save, set  up,  and	restore	 frame
	   pointers  and  makes	an extra register available in leaf functions.
	   The option -fomit-leaf-frame-pointer	removes	the frame pointer  for
	   leaf	functions, which might make debugging harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
	   Controls  whether  TLS  variables may be accessed with offsets from
	   the TLS segment register (%gs  for  32-bit,	%fs  for  64-bit),  or
	   whether the thread base pointer must	be added.  Whether or not this
	   is  valid  depends on the operating system, and whether it maps the
	   segment to cover the	entire TLS area.

	   For systems that use	the GNU	C Library, the default is on.

       -msse2avx
       -mno-sse2avx
	   Specify that	the assembler should encode SSE	instructions with  VEX
	   prefix.  The	option -mavx turns this	on by default.

       -mfentry
       -mno-fentry
	   If profiling	is active (-pg), put the profiling counter call	before
	   the	 prologue.    Note:   On   x86	 architectures	the  attribute
	   "ms_hook_prologue" isn't possible at	the moment  for	 -mfentry  and
	   -pg.

       -mrecord-mcount
       -mno-record-mcount
	   If  profiling is active (-pg), generate a __mcount_loc section that
	   contains pointers to	 each  profiling  call.	 This  is  useful  for
	   automatically patching and out calls.

       -mnop-mcount
       -mno-nop-mcount
	   If  profiling  is active (-pg), generate the	calls to the profiling
	   functions as	NOPs. This is useful when they should  be  patched  in
	   later  dynamically.	This  is  likely  only	useful	together  with
	   -mrecord-mcount.

       -minstrument-return=type
	   Instrument function exit in	-pg  -mfentry  instrumented  functions
	   with	call to	specified function. This only instruments true returns
	   ending  with	 ret,  but  not	 sibling calls ending with jump. Valid
	   types are none to not  instrument,  call  to	 generate  a  call  to
	   __return__, or nop5 to generate a 5 byte nop.

       -mrecord-return
       -mno-record-return
	   Generate   a	  __return_loc	 section   pointing   to   all	return
	   instrumentation code.

       -mfentry-name=name
	   Set name of __fentry__ symbol called	 at  function  entry  for  -pg
	   -mfentry functions.

       -mfentry-section=name
	   Set	name  of  section  to  record  -mrecord-mcount	calls (default
	   __mcount_loc).

       -mskip-rax-setup
       -mno-skip-rax-setup
	   When	 generating  code  for	the  x86-64  architecture   with   SSE
	   extensions  disabled,  -mskip-rax-setup can be used to skip setting
	   up RAX register when	there are  no  variable	 arguments  passed  in
	   vector registers.

	   Warning:  Since  RAX	register is used to avoid unnecessarily	saving
	   vector registers on stack  when  passing  variable  arguments,  the
	   impacts  of	this  option  are  callees may waste some stack	space,
	   misbehave or	jump to	a random location.  GCC	 4.4  or  newer	 don't
	   have	those issues, regardless the RAX register value.

       -m8bit-idiv
       -mno-8bit-idiv
	   On  some processors,	like Intel Atom, 8-bit unsigned	integer	divide
	   is much faster than	32-bit/64-bit  integer	divide.	  This	option
	   generates  a	 run-time  check.   If	both  dividend and divisor are
	   within range	of 0 to	255, 8-bit unsigned  integer  divide  is  used
	   instead of 32-bit/64-bit integer divide.

       -mavx256-split-unaligned-load
       -mavx256-split-unaligned-store
	   Split 32-byte AVX unaligned load and	store.

       -mstack-protector-guard=guard
       -mstack-protector-guard-reg=reg
       -mstack-protector-guard-offset=offset
	   Generate  stack  protection	code using canary at guard.  Supported
	   locations are global	for global canary or tls for per-thread	canary
	   in the TLS block (the default).  This option	has effect  only  when
	   -fstack-protector or	-fstack-protector-all is specified.

	   With	 the latter choice the options -mstack-protector-guard-reg=reg
	   and -mstack-protector-guard-offset=offset furthermore specify which
	   segment register (%fs or %gs) to use	as base	register  for  reading
	   the	canary,	 and  from  what  offset from that base	register.  The
	   default for those is	as specified in	the relevant ABI.

       -mgeneral-regs-only
	   Generate code that uses only	the general-purpose  registers.	  This
	   prevents  the  compiler from	using floating-point, vector, mask and
	   bound registers.

       -mindirect-branch=choice
	   Convert indirect call and jump with choice.	The default  is	 keep,
	   which  keeps	 indirect  call	 and  jump unmodified.	thunk converts
	   indirect call and jump to  call  and	 return	 thunk.	  thunk-inline
	   converts  indirect  call and	jump to	inlined	call and return	thunk.
	   thunk-extern	converts indirect call and jump	to external  call  and
	   return  thunk  provided in a	separate object	file.  You can control
	   this	behavior  for  a  specific  function  by  using	 the  function
	   attribute "indirect_branch".

	   Note	     that      -mcmodel=large	  is	 incompatible	  with
	   -mindirect-branch=thunk  and	 -mindirect-branch=thunk-extern	 since
	   the thunk function may not be reachable in the large	code model.

	   Note	  that	 -mindirect-branch=thunk-extern	  is  compatible  with
	   -fcf-protection=branch since	the external  thunk  can  be  made  to
	   enable control-flow check.

       -mfunction-return=choice
	   Convert  function  return  with choice.  The	default	is keep, which
	   keeps function return unmodified.  thunk converts  function	return
	   to call and return thunk.  thunk-inline converts function return to
	   inlined  call  and  return  thunk.	thunk-extern converts function
	   return to external call and return thunk  provided  in  a  separate
	   object file.	 You can control this behavior for a specific function
	   by using the	function attribute "function_return".

	   Note	  that	 -mindirect-return=thunk-extern	  is  compatible  with
	   -fcf-protection=branch since	the external  thunk  can  be  made  to
	   enable control-flow check.

	   Note	     that      -mcmodel=large	  is	 incompatible	  with
	   -mfunction-return=thunk  and	 -mfunction-return=thunk-extern	 since
	   the thunk function may not be reachable in the large	code model.

       -mindirect-branch-register
	   Force indirect call and jump	via register.

       -mharden-sls=choice
	   Generate  code  to mitigate against straight	line speculation (SLS)
	   with	choice.	 The default is	none which disables all	SLS hardening.
	   return enables SLS hardening	for  function  returns.	  indirect-jmp
	   enables  SLS	 hardening  for	 indirect  jumps.  all enables all SLS
	   hardening.

       -mindirect-branch-cs-prefix
	   Add CS prefix to call and jmp to indirect thunk with	branch	target
	   in  r8-r15 registers	so that	the call and jmp instruction length is
	   6 bytes to allow them to be replaced	with lfence; call *%r8-r15  or
	   lfence; jmp *%r8-r15	at run-time.

       These  -m  switches  are	 supported  in addition	to the above on	x86-64
       processors in 64-bit environments.

       -m32
       -m64
       -mx32
       -m16
       -miamcu
	   Generate code for a 16-bit, 32-bit or 64-bit	environment.  The -m32
	   option sets "int", "long",  and  pointer  types  to	32  bits,  and
	   generates code that runs in 32-bit mode.

	   The	-m64 option sets "int" to 32 bits and "long" and pointer types
	   to 64 bits, and generates code for the  x86-64  architecture.   For
	   Darwin  only	 the  -m64  option  also  turns	 off  the -fno-pic and
	   -mdynamic-no-pic options.

	   The -mx32 option sets "int",	"long",	and pointer types to 32	 bits,
	   and generates code for the x86-64 architecture.

	   The -m16 option is the same as -m32,	except for that	it outputs the
	   ".code16gcc"	 assembly  directive  at the beginning of the assembly
	   output so that the binary can run in	16-bit mode.

	   The -miamcu option generates	 code  which  conforms	to  Intel  MCU
	   psABI.  It requires the -m32	option to be turned on.

       -mno-red-zone
	   Do not use a	so-called "red zone" for x86-64	code.  The red zone is
	   mandated  by	 the  x86-64  ABI;  it	is  a 128-byte area beyond the
	   location of the stack pointer that is not  modified	by  signal  or
	   interrupt  handlers	and  therefore	can be used for	temporary data
	   without  adjusting  the  stack  pointer.   The  flag	 -mno-red-zone
	   disables this red zone.

       -mcmodel=small
	   Generate code for the small code model: the program and its symbols
	   must	 be  linked  in	the lower 2 GB of the address space.  Pointers
	   are 64 bits.	 Programs can be  statically  or  dynamically  linked.
	   This	is the default code model.

       -mcmodel=kernel
	   Generate  code  for	the kernel code	model.	The kernel runs	in the
	   negative 2 GB of the	address	space.	This model has to be used  for
	   Linux kernel	code.

       -mcmodel=medium
	   Generate  code  for	the medium model: the program is linked	in the
	   lower 2 GB of the address space.  Small  symbols  are  also	placed
	   there.   Symbols  with sizes	larger than -mlarge-data-threshold are
	   put into large data or BSS sections and can be located  above  2GB.
	   Programs can	be statically or dynamically linked.

       -mcmodel=large
	   Generate code for the large model.  This model makes	no assumptions
	   about addresses and sizes of	sections.

       -maddress-mode=long
	   Generate  code  for	long address mode.  This is only supported for
	   64-bit and x32 environments.	 It is the default  address  mode  for
	   64-bit environments.

       -maddress-mode=short
	   Generate  code  for short address mode.  This is only supported for
	   32-bit and x32 environments.	 It is the default  address  mode  for
	   32-bit and x32 environments.

       -mneeded
       -mno-needed
	   Emit	GNU_PROPERTY_X86_ISA_1_NEEDED GNU property for Linux target to
	   indicate  the  micro-architecture ISA level required	to execute the
	   binary.

       x86 Windows Options

       These additional	options	are available for Microsoft Windows targets:

       -mconsole
	   This	 option	 specifies  that  a  console  application  is  to   be
	   generated, by instructing the linker	to set the PE header subsystem
	   type	 required  for console applications.  This option is available
	   for Cygwin and MinGW	targets	and is enabled	by  default  on	 those
	   targets.

       -mdll
	   This	 option	 is  available	for  Cygwin  and  MinGW	 targets.   It
	   specifies that a DLL---a dynamic link library---is to be generated,
	   enabling the	selection of the required runtime startup  object  and
	   entry point.

       -mnop-fun-dllimport
	   This	 option	 is  available	for  Cygwin  and  MinGW	 targets.   It
	   specifies that the "dllimport" attribute should be ignored.

       -mthread
	   This	option is available  for  MinGW	 targets.  It  specifies  that
	   MinGW-specific thread support is to be used.

       -municode
	   This	 option	 is  available	for  MinGW-w64 targets.	 It causes the
	   "UNICODE" preprocessor macro	to be predefined, and chooses Unicode-
	   capable runtime startup code.

       -mwin32
	   This	 option	 is  available	for  Cygwin  and  MinGW	 targets.   It
	   specifies  that the typical Microsoft Windows predefined macros are
	   to be set in	the pre-processor, but does not	influence  the	choice
	   of runtime library/startup code.

       -mwindows
	   This	 option	 is  available	for  Cygwin  and  MinGW	 targets.   It
	   specifies that a GUI	application is to be generated by  instructing
	   the linker to set the PE header subsystem type appropriately.

       -fno-set-stack-executable
	   This	 option	 is available for MinGW	targets. It specifies that the
	   executable flag for the stack used by nested	functions  isn't  set.
	   This	 is necessary for binaries running in kernel mode of Microsoft
	   Windows, as there the User32	API, which is used to  set  executable
	   privileges, isn't available.

       -fwritable-relocated-rdata
	   This	 option	 is  available	for  MinGW  and	 Cygwin	 targets.   It
	   specifies that relocated-data in read-only section is put into  the
	   ".data"  section.   This  is	 a  necessary  for  older runtimes not
	   supporting modification of ".rdata" sections	for pseudo-relocation.

       -mpe-aligned-commons
	   This	 option	 is  available	for  Cygwin  and  MinGW	 targets.   It
	   specifies that the GNU extension to the PE file format that permits
	   the	correct	 alignment  of	COMMON	variables  should be used when
	   generating code.  It	is enabled by default if GCC detects that  the
	   target assembler found during configuration supports	the feature.

       See also	under x86 Options for standard options.

       Xstormy16 Options

       These options are defined for Xstormy16:

       -msim
	   Choose startup files	and linker script suitable for the simulator.

       Xtensa Options

       These options are supported for Xtensa targets:

       -mconst16
       -mno-const16
	   Enable  or  disable	use  of	 "CONST16"  instructions  for  loading
	   constant values.  The "CONST16"  instruction	 is  currently	not  a
	   standard   option   from   Tensilica.    When   enabled,  "CONST16"
	   instructions	are always  used  in  place  of	 the  standard	"L32R"
	   instructions.   The	use of "CONST16" is enabled by default only if
	   the "L32R" instruction is not available.

       -mfused-madd
       -mno-fused-madd
	   Enable or disable use of fused multiply/add	and  multiply/subtract
	   instructions	 in  the floating-point	option.	 This has no effect if
	   the floating-point option is	not  also  enabled.   Disabling	 fused
	   multiply/add	and multiply/subtract instructions forces the compiler
	   to  use  separate  instructions  for	 the multiply and add/subtract
	   operations.	This may be desirable in some cases where strict  IEEE
	   754-compliant results are required: the fused multiply add/subtract
	   instructions	  do   not  round  the	intermediate  result,  thereby
	   producing results with more bits of precision than specified	by the
	   IEEE	standard.  Disabling fused multiply add/subtract  instructions
	   also	 ensures  that	the  program  output  is  not sensitive	to the
	   compiler's ability to combine multiply and add/subtract operations.

       -mserialize-volatile
       -mno-serialize-volatile
	   When	this option is enabled,	GCC inserts "MEMW" instructions	before
	   "volatile" memory references	to guarantee  sequential  consistency.
	   The	default	 is -mserialize-volatile.  Use -mno-serialize-volatile
	   to omit the "MEMW" instructions.

       -mforce-no-pic
	   For targets,	like GNU/Linux,	where all user-mode Xtensa  code  must
	   be  position-independent  code  (PIC), this option disables PIC for
	   compiling kernel code.

       -mtext-section-literals
       -mno-text-section-literals
	   These options control the treatment of literal pools.  The  default
	   is  -mno-text-section-literals, which places	literals in a separate
	   section in the output file.	This allows the	 literal  pool	to  be
	   placed  in a	data RAM/ROM, and it also allows the linker to combine
	   literal pools  from	separate  object  files	 to  remove  redundant
	   literals  and improve code size.  With -mtext-section-literals, the
	   literals are	interspersed in	the text section in order to keep them
	   as close as possible	to their references.  This  may	 be  necessary
	   for	large  assembly	 files.	 Literals for each function are	placed
	   right before	that function.

       -mauto-litpools
       -mno-auto-litpools
	   These options control the treatment of literal pools.  The  default
	   is  -mno-auto-litpools, which places	literals in a separate section
	   in the output file unless -mtext-section-literals  is  used.	  With
	   -mauto-litpools  the	 literals are interspersed in the text section
	   by the assembler.  Compiler does not	 produce  explicit  ".literal"
	   directives	and   loads   literals	 into  registers  with	"MOVI"
	   instructions	instead	of "L32R" to let the assembler	do  relaxation
	   and	place  literals	as necessary.  This option allows assembler to
	   create several literal pools	per function  and  assemble  very  big
	   functions, which may	not be possible	with -mtext-section-literals.

       -mtarget-align
       -mno-target-align
	   When	 this  option  is  enabled,  GCC  instructs  the  assembler to
	   automatically align instructions to reduce branch penalties at  the
	   expense  of	some  code  density.   The assembler attempts to widen
	   density instructions	to align branch	targets	and  the  instructions
	   following  call  instructions.   If	there are not enough preceding
	   safe	density	 instructions  to  align  a  target,  no  widening  is
	   performed.	The  default  is -mtarget-align.  These	options	do not
	   affect the treatment	 of  auto-aligned  instructions	 like  "LOOP",
	   which  the  assembler  always  aligns,  either  by widening density
	   instructions	or by inserting	NOP instructions.

       -mlongcalls
       -mno-longcalls
	   When	this  option  is  enabled,  GCC	 instructs  the	 assembler  to
	   translate  direct  calls  to	indirect calls unless it can determine
	   that	the target of a	direct call is in the  range  allowed  by  the
	   call	 instruction.	This translation typically occurs for calls to
	   functions in	 other	source	files.	 Specifically,	the  assembler
	   translates a	direct "CALL" instruction into an "L32R" followed by a
	   "CALLX"  instruction.   The default is -mno-longcalls.  This	option
	   should be used in programs where the	call target can	potentially be
	   out of range.  This option is implemented in	the assembler, not the
	   compiler, so	the assembly code generated by GCC still shows	direct
	   call	instructions---look at the disassembled	object code to see the
	   actual instructions.	 Note that the assembler uses an indirect call
	   for	every  cross-file  call, not just those	that really are	out of
	   range.

       -mabi=name
	   Generate code for  the  specified  ABI.   Permissible  values  are:
	   call0,  windowed.   Default	ABI  is	 chosen	 by  the  Xtensa  core
	   configuration.

       -mabi=call0
	   When	this option is	enabled	 function  parameters  are  passed  in
	   registers  "a2"  through  "a7",  registers  "a12" through "a15" are
	   caller-saved, and register "a15" may	be used	as  a  frame  pointer.
	   When	 this  version of the ABI is enabled the C preprocessor	symbol
	   "__XTENSA_CALL0_ABI__" is defined.

       -mabi=windowed
	   When	this option is	enabled	 function  parameters  are  passed  in
	   registers "a10" through "a15", and called function rotates register
	   window  by  8 registers on entry so that its	arguments are found in
	   registers "a2" through "a7".	 Register "a7" may be used as a	 frame
	   pointer.   Register window is rotated 8 registers back upon return.
	   When	this version of	the ABI	is enabled the C  preprocessor	symbol
	   "__XTENSA_WINDOWED_ABI__" is	defined.

       zSeries Options

       These are listed	under

ENVIRONMENT
       This  section  describes	 several environment variables that affect how
       GCC operates.  Some of them work	by specifying directories or  prefixes
       to  use	when  searching	 for various kinds of files.  Some are used to
       specify other aspects of	the compilation	environment.

       Note that you can also specify places to	search using options  such  as
       -B,  -I	and  -L.   These  take	precedence over	places specified using
       environment  variables,	which  in  turn	 take  precedence  over	 those
       specified by the	configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
	   These   environment	 variables  control  the  way  that  GCC  uses
	   localization	information which allows GCC to	 work  with  different
	   national  conventions.  GCC inspects	the locale categories LC_CTYPE
	   and LC_MESSAGES if it has been configured to	do so.	 These	locale
	   categories  can be set to any value supported by your installation.
	   A typical value is en_GB.UTF-8 for English in  the  United  Kingdom
	   encoded in UTF-8.

	   The	  LC_CTYPE    environment    variable	 specifies   character
	   classification.  GCC	uses it	to determine the character  boundaries
	   in  a  string;  this	 is  needed  for some multibyte	encodings that
	   contain quote and escape characters that are	otherwise  interpreted
	   as a	string end or escape.

	   The	LC_MESSAGES environment	variable specifies the language	to use
	   in diagnostic messages.

	   If the LC_ALL environment variable is set, it overrides  the	 value
	   of  LC_CTYPE	 and  LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES
	   default to the value	of the LANG environment	variable.  If none  of
	   these  variables  are  set,	GCC  defaults to traditional C English
	   behavior.

       TMPDIR
	   If TMPDIR is	set, it	specifies the directory	to use	for  temporary
	   files.  GCC uses temporary files to hold the	output of one stage of
	   compilation	which  is  to  be used as input	to the next stage: for
	   example, the	output of the preprocessor, which is the input to  the
	   compiler proper.

       GCC_COMPARE_DEBUG
	   Setting   GCC_COMPARE_DEBUG	 is   nearly   equivalent  to  passing
	   -fcompare-debug to the compiler driver.  See	the  documentation  of
	   this	option for more	details.

       GCC_EXEC_PREFIX
	   If  GCC_EXEC_PREFIX	is  set,  it  specifies	a prefix to use	in the
	   names of the	subprograms executed by	the  compiler.	 No  slash  is
	   added  when	this prefix is combined	with the name of a subprogram,
	   but you can specify a prefix	that ends with a slash if you wish.

	   If GCC_EXEC_PREFIX is not  set,  GCC	 attempts  to  figure  out  an
	   appropriate prefix to use based on the pathname it is invoked with.

	   If  GCC  cannot  find the subprogram	using the specified prefix, it
	   tries looking in the	usual places for the subprogram.

	   The default	value  of  GCC_EXEC_PREFIX  is	prefix/lib/gcc/	 where
	   prefix  is  the  prefix  to	the  installed compiler. In many cases
	   prefix is the value of "prefix" when	you ran	the configure script.

	   Other prefixes specified with -B take precedence over this prefix.

	   This	prefix is also used for	finding	files such as crt0.o that  are
	   used	for linking.

	   In  addition,  the  prefix is used in an unusual way	in finding the
	   directories to search for header files.  For	each of	 the  standard
	   directories	whose  name  normally  begins  with /usr/local/lib/gcc
	   (more precisely, with the  value  of	 GCC_INCLUDE_DIR),  GCC	 tries
	   replacing  that  beginning  with the	specified prefix to produce an
	   alternate directory name.  Thus, with -Bfoo/, GCC searches  foo/bar
	   just	 before	it searches the	standard directory /usr/local/lib/bar.
	   If a	standard directory begins with the configured prefix then  the
	   value  of  prefix  is  replaced by GCC_EXEC_PREFIX when looking for
	   header files.

       COMPILER_PATH
	   The	value  of  COMPILER_PATH  is   a   colon-separated   list   of
	   directories,	 much  like  PATH.   GCC  tries	 the  directories thus
	   specified when searching for	subprograms, if	 it  cannot  find  the
	   subprograms using GCC_EXEC_PREFIX.

       LIBRARY_PATH
	   The value of	LIBRARY_PATH is	a colon-separated list of directories,
	   much	 like  PATH.   When configured as a native compiler, GCC tries
	   the directories thus	specified when searching  for  special	linker
	   files, if it	cannot find them using GCC_EXEC_PREFIX.	 Linking using
	   GCC	also  uses  these  directories	when  searching	 for  ordinary
	   libraries for the -l	option (but directories	specified with -L come
	   first).

       LANG
	   This	variable is used to pass locale	information to	the  compiler.
	   One	way  in	 which	this  information  is used is to determine the
	   character set to be used when character literals,  string  literals
	   and	comments  are  parsed  in  C  and  C++.	  When the compiler is
	   configured to allow multibyte characters, the following values  for
	   LANG	are recognized:

	   C-JIS
	       Recognize JIS characters.

	   C-SJIS
	       Recognize SJIS characters.

	   C-EUCJP
	       Recognize EUCJP characters.

	   If  LANG  is	 not  defined, or if it	has some other value, then the
	   compiler uses "mblen" and "mbtowc" as defined by the	default	locale
	   to recognize	and translate multibyte	characters.

       GCC_EXTRA_DIAGNOSTIC_OUTPUT
	   If GCC_EXTRA_DIAGNOSTIC_OUTPUT is  set  to  one  of	the  following
	   values,  then additional text will be emitted to stderr when	fix-it
	   hints    are	   emitted.	-fdiagnostics-parseable-fixits	   and
	   -fno-diagnostics-parseable-fixits   take   precedence   over	  this
	   environment variable.

	   fixits-v1
	       Emit	parseable     fix-it	 hints,	    equivalent	    to
	       -fdiagnostics-parseable-fixits.	 In  particular,  columns  are
	       expressed as a count of bytes,  starting	 at  byte  1  for  the
	       initial column.

	   fixits-v2
	       As  "fixits-v1",	 but columns are expressed as display columns,
	       as per -fdiagnostics-column-unit=display.

       Some additional	environment  variables	affect	the  behavior  of  the
       preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
	   Each	 variable's  value  is	a  list	 of directories	separated by a
	   special character, much like	PATH, in  which	 to  look  for	header
	   files.    The   special  character,	"PATH_SEPARATOR",  is  target-
	   dependent and determined at GCC build time.	For Microsoft Windows-
	   based targets it is a semicolon, and	for almost all	other  targets
	   it is a colon.

	   CPATH  specifies  a	list  of  directories  to  be  searched	 as if
	   specified with -I, but after	any paths given	with -I	options	on the
	   command line.  This environment  variable  is  used	regardless  of
	   which language is being preprocessed.

	   The	remaining  environment variables apply only when preprocessing
	   the particular  language  indicated.	  Each	specifies  a  list  of
	   directories to be searched as if specified with -isystem, but after
	   any paths given with	-isystem options on the	command	line.

	   In  all these variables, an empty element instructs the compiler to
	   search its current working directory.  Empty	elements can appear at
	   the beginning or end	of a path.  For	 instance,  if	the  value  of
	   CPATH   is	":/special/include",  that  has	 the  same  effect  as
	   -I. -I/special/include.

       DEPENDENCIES_OUTPUT
	   If this  variable  is  set,	its  value  specifies  how  to	output
	   dependencies	  for  Make  based  on	the  non-system	 header	 files
	   processed by	the compiler.  System header files are ignored in  the
	   dependency output.

	   The	value of DEPENDENCIES_OUTPUT can be just a file	name, in which
	   case	the Make rules are written to that file, guessing  the	target
	   name	 from  the  source  file name.	Or the value can have the form
	   file	target,	in which case the rules	are written to file file using
	   target as the target	name.

	   In  other  words,  this  environment	 variable  is  equivalent   to
	   combining the options -MM and -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
	   This	 variable  is  the  same  as  DEPENDENCIES_OUTPUT (see above),
	   except that system header files are not ignored, so it  implies  -M
	   rather than -MM.  However, the dependence on	the main input file is
	   omitted.

       SOURCE_DATE_EPOCH
	   If this variable is set, its	value specifies	a UNIX timestamp to be
	   used	 in replacement	of the current date and	time in	the "__DATE__"
	   and "__TIME__" macros,  so  that  the  embedded  timestamps	become
	   reproducible.

	   The value of	SOURCE_DATE_EPOCH must be a UNIX timestamp, defined as
	   the	number	of  seconds (excluding leap seconds) since 01 Jan 1970
	   00:00:00 represented	in ASCII; identical to	the  output  of	 "date
	   +%s"	 on  GNU/Linux and other systems that support the %s extension
	   in the "date" command.

	   The value should be a known timestamp such as the last modification
	   time	of the source or package and it	should be  set	by  the	 build
	   process.

BUGS
       For instructions	on reporting bugs, see <https://gcc.gnu.org/bugs/>.

FOOTNOTES
       1.  On some systems, gcc	-shared	needs to build supplementary stub code
	   for	constructors  to  work.	  On multi-libbed systems, gcc -shared
	   must	select the correct support libraries to	link against.  Failing
	   to supply the correct flags may lead	to subtle defects.   Supplying
	   them	in cases where they are	not necessary is innocuous.

SEE ALSO
       gpl(7), gfdl(7),	fsf-funding(7),	cpp(1),	gcov(1), as(1),	ld(1), gdb(1),
       dbx(1) and the Info entries for gcc, cpp, as, ld, binutils and gdb.

AUTHOR
       See	  the	     Info	 entry	      for	 gcc,	    or
       <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for contributors
       to GCC.

COPYRIGHT
       Copyright (c) 1988-2021 Free Software Foundation, Inc.

       Permission is granted to	copy, distribute and/or	modify	this  document
       under  the  terms of the	GNU Free Documentation License,	Version	1.3 or
       any later version published by the Free Software	Foundation;  with  the
       Invariant Sections being	"GNU General Public License" and "Funding Free
       Software",  the	Front-Cover  texts being (a) (see below), and with the
       Back-Cover Texts	being (b) (see below).	 A  copy  of  the  license  is
       included	in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

	    A GNU Manual

       (b) The FSF's Back-Cover	Text is:

	    You	have freedom to	copy and modify	this GNU Manual, like GNU
	    software.  Copies published	by the Free Software Foundation	raise
	    funds for GNU development.

gcc-11.5.0			  2024-07-19				GCC(1)