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

[Uros Bizjak <ubizjak@gmail.com>]

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.

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
>