From 458d2c689963d8461d84670a3d8988cd6ecbfd81 Mon Sep 17 00:00:00 2001 From: Martin Jambor Date: Fri, 19 Nov 2021 18:46:00 +0100 Subject: [PATCH] options: Make -Ofast switch off -fsemantic-interposition Using -fno-semantic-interposition has been reported by various people to bring about considerable speed up at the cost of strict compliance to the ELF symbol interposition rules See for example https://fedoraproject.org/wiki/Changes/PythonNoSemanticInterpositionSpeedup As such I believe it should be implied by our -Ofast optimization level, not only so that benchmarks that can benefit run faster, but also so that people looking at -Ofast documentation for options that could speed their programs find it. gcc/ChangeLog: 2021-11-12 Martin Jambor * opts.c (default_options_table): Switch off flag_semantic_interposition at Ofast. * doc/invoke.texi (Optimize Options): Document that Ofast switches off -fsemantic-interposition. --- gcc/doc/invoke.texi | 1 + gcc/opts.c | 1 + 2 files changed, 2 insertions(+) diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 11ef79703787..1cfb70291f68 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -10677,6 +10677,7 @@ valid for all standard-compliant programs. It turns on @option{-ffast-math}, @option{-fallow-store-data-races} and the Fortran-specific @option{-fstack-arrays}, unless @option{-fmax-stack-var-size} is specified, and @option{-fno-protect-parens}. +It turns off @option {-fsemantic-interposition}. @item -Og @opindex Og diff --git a/gcc/opts.c b/gcc/opts.c index 175b4635bb4d..b16497e45b30 100644 --- a/gcc/opts.c +++ b/gcc/opts.c @@ -682,6 +682,7 @@ static const struct default_options default_options_table[] = /* -Ofast adds optimizations to -O3. */ { OPT_LEVELS_FAST, OPT_ffast_math, NULL, 1 }, { OPT_LEVELS_FAST, OPT_fallow_store_data_races, NULL, 1 }, + { OPT_LEVELS_FAST, OPT_fsemantic_interposition, NULL, 0 }, { OPT_LEVELS_NONE, 0, NULL, 0 } }; -- 2.47.2