diff options
Diffstat (limited to 'gcc/doc/invoke.texi')
| -rw-r--r-- | gcc/doc/invoke.texi | 45 |
1 files changed, 36 insertions, 9 deletions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index fbaa29f..0b6644b 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -593,7 +593,7 @@ Objective-C and Objective-C++ Dialects}. -finline-functions -finline-functions-called-once -finline-limit=@var{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-reference -fipa-reference-addressable -fipa-reorder-for-locality -fipa-stack-alignment -fipa-icf -fira-algorithm=@var{algorithm} -flate-combine-instructions -flifetime-dse -flive-patching=@var{level} -fira-region=@var{region} -fira-hoist-pressure @@ -12746,6 +12746,7 @@ complexity than at @option{-O}. -fipa-pure-const -fipa-reference -fipa-reference-addressable +-fivopts -fmerge-constants -fmove-loop-invariants -fmove-loop-stores @@ -12854,6 +12855,13 @@ by @option{-O2} and also turns on the following optimization flags: Reduce compilation time and make debugging produce the expected results. This is the default. +At @option{-O0}, GCC completely disables most optimization passes; +they are not run even if you explicitly enable them on the command +line, or are listed by @option{-Q --help=optimizers} as being enabled by +default. Many optimizations performed by GCC depend on code analysis +or canonicalization passes that are enabled by @option{-O}, and it would +not be useful to run individual optimization passes in isolation. + @opindex Os @item -Os Optimize for size. @option{-Os} enables all @option{-O2} optimizations @@ -13871,6 +13879,21 @@ Enabled by default at @option{-O1} and higher. Discover read-only, write-only and non-addressable static variables. Enabled by default at @option{-O1} and higher. +@opindex fipa-reorder-for-locality +@item -fipa-reorder-for-locality +Group call chains close together in the binary layout to improve code +locality and minimize jump distances between frequently called functions. +Unlike @option{-freorder-functions} this pass considers the call +chains between functions and groups them together, rather than grouping all +hot/normal/cold/never-executed functions into separate sections. +Unlike @option{-fprofile-reorder-functions} it aims to improve code locality +throughout the runtime of the program rather than focusing on program startup. +This option is incompatible with an explicit +@option{-flto-partition=} option since it enforces a custom partitioning +scheme. +If using this option it is recommended to also use profile feedback, but this +option is not enabled by default otherwise. + @opindex fipa-stack-alignment @item -fipa-stack-alignment Reduce stack alignment on call sites if possible. @@ -14291,6 +14314,7 @@ Enabled by default at @option{-O1} and higher. @item -fivopts Perform induction variable optimizations (strength reduction, induction variable merging and induction variable elimination) on trees. +Enabled by default at @option{-O1} and higher. @opindex ftree-parallelize-loops @item -ftree-parallelize-loops=n @@ -14606,11 +14630,13 @@ Enabled for x86 at levels @option{-O2}, @option{-O3}, @option{-Os}. @opindex freorder-functions @item -freorder-functions Reorder functions in the object file in order to -improve code locality. This is implemented by using special -subsections @code{.text.hot} for most frequently executed functions and -@code{.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. +improve code locality. Unlike @option{-fipa-reorder-for-locality} this option +prioritises grouping all functions within a category +(hot/normal/cold/never-executed) together. +This is implemented by using special subsections @code{.text.hot} for most +frequently executed functions and @code{.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 @option{-fprofile-arcs} for details) or manually annotate functions with @@ -15635,7 +15661,8 @@ Enabled by @option{-fprofile-generate}, @option{-fprofile-use}, and @item -fprofile-reorder-functions Function reordering based on profile instrumentation collects first time of execution of a function and orders these functions -in ascending order. +in ascending order, aiming to optimize program startup through more +efficient loading of text segments. Enabled with @option{-fprofile-use}. @@ -33344,7 +33371,7 @@ system representing a certain processor type. Possible values for @samp{z9-109}, @samp{z9-ec}/@samp{arch7}, @samp{z10}/@samp{arch8}, @samp{z196}/@samp{arch9}, @samp{zEC12}, @samp{z13}/@samp{arch11}, @samp{z14}/@samp{arch12}, @samp{z15}/@samp{arch13}, -@samp{z16}/@samp{arch14}, and @samp{native}. +@samp{z16}/@samp{arch14}, @samp{z17}/@samp{arch15}, and @samp{native}. The default is @option{-march=z900}. @@ -34872,7 +34899,7 @@ Intel Lakemont MCU, based on Intel Pentium CPU. Intel Pentium MMX CPU, based on Pentium core with MMX instruction set support. @item pentiumpro -Intel Pentium Pro CPU@. +Intel Pentium Pro CPU with no MMX support. @item i686 When used with @option{-march}, the Pentium Pro |