Re: [PATCH 2/2] Make option mvzeroupper independent of optimization level.

[Hongtao Liu <crazylht@gmail.com>]

On Tue, Jun 27, 2023 at 2:05 PM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> On Tue, Jun 27, 2023 at 7:55 AM liuhongt <hongtao.liu@intel.com> wrote:
> >
> > pass_insert_vzeroupper is under condition
> >
> > TARGET_AVX && TARGET_VZEROUPPER
> > && flag_expensive_optimizations && !optimize_size
> >
> > But the document of mvzeroupper doesn't mention the insertion
> > required -O2 and above, it may confuse users when they explicitly
> > use -Os -mvzeroupper.
> >
> > ------------
> > mvzeroupper
> > Target Mask(VZEROUPPER) Save
> > Generate vzeroupper instruction before a transfer of control flow out of
> > the function.
> > ------------
> >
> > The patch moves flag_expensive_optimizations && !optimize_size to
> > ix86_option_override_internal. It makes -mvzeroupper independent of
> > optimization level, but still keeps the behavior of architecture
> > tuning(emit_vzeroupper) unchanged.
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> > Ok for trunk?
> >
> > gcc/ChangeLog:
> >
> >         * config/i386/i386-features.cc (pass_insert_vzeroupper:gate):
> >         Move flag_expensive_optimizations && !optimize_size to ..
> >         * config/i386/i386-options.cc (ix86_option_override_internal):
> >         .. this, it makes -mvzeroupper independent of optimization
> >         level, but still keeps the behavior of architecture
> >         tuning(emit_vzeroupper) unchanged.
> >
> > gcc/testsuite/ChangeLog:
> >
> >         * gcc.target/i386/avx-vzeroupper-29.c: New testcase.
>
> OK.
I'd like to backport this patch to GCC10/GCC11/GCC12/GCC13.
>
> Thanks,
> Uros.
>
> > ---
> >  gcc/config/i386/i386-features.cc                  |  3 +--
> >  gcc/config/i386/i386-options.cc                   |  4 +++-
> >  gcc/testsuite/gcc.target/i386/avx-vzeroupper-29.c | 14 ++++++++++++++
> >  3 files changed, 18 insertions(+), 3 deletions(-)
> >  create mode 100644 gcc/testsuite/gcc.target/i386/avx-vzeroupper-29.c
> >
> > diff --git a/gcc/config/i386/i386-features.cc b/gcc/config/i386/i386-features.cc
> > index 4a3b07ae045..92ae08d442e 100644
> > --- a/gcc/config/i386/i386-features.cc
> > +++ b/gcc/config/i386/i386-features.cc
> > @@ -2489,8 +2489,7 @@ public:
> >    /* opt_pass methods: */
> >    bool gate (function *) final override
> >      {
> > -      return TARGET_AVX && TARGET_VZEROUPPER
> > -       && flag_expensive_optimizations && !optimize_size;
> > +      return TARGET_AVX && TARGET_VZEROUPPER;
> >      }
> >
> >    unsigned int execute (function *) final override
> > diff --git a/gcc/config/i386/i386-options.cc b/gcc/config/i386/i386-options.cc
> > index 2cb0bddcd35..f76e7c5947b 100644
> > --- a/gcc/config/i386/i386-options.cc
> > +++ b/gcc/config/i386/i386-options.cc
> > @@ -2727,7 +2727,9 @@ ix86_option_override_internal (bool main_args_p,
> >      sorry ("%<-mcall-ms2sysv-xlogues%> isn%'t currently supported with SEH");
> >
> >    if (!(opts_set->x_target_flags & MASK_VZEROUPPER)
> > -      && TARGET_EMIT_VZEROUPPER)
> > +      && TARGET_EMIT_VZEROUPPER
> > +      && flag_expensive_optimizations
> > +      && !optimize_size)
> >      opts->x_target_flags |= MASK_VZEROUPPER;
> >    if (!(opts_set->x_target_flags & MASK_STV))
> >      opts->x_target_flags |= MASK_STV;
> > diff --git a/gcc/testsuite/gcc.target/i386/avx-vzeroupper-29.c b/gcc/testsuite/gcc.target/i386/avx-vzeroupper-29.c
> > new file mode 100644
> > index 00000000000..4af637757f7
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/avx-vzeroupper-29.c
> > @@ -0,0 +1,14 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O0 -mavx -mtune=generic -mvzeroupper -dp" } */
> > +
> > +#include <immintrin.h>
> > +
> > +extern __m256 x, y;
> > +
> > +void
> > +foo ()
> > +{
> > +  x = y;
> > +}
> > +
> > +/* { dg-final { scan-assembler-times "avx_vzeroupper" 1 } } */
> > --
> > 2.39.1.388.g2fc9e9ca3c
> >



-- 
BR,
Hongtao