[v3,8/8] x86-64: Require BMI1/BMI2 for AVX2 strrchr and wcsrchr implementations

  The AVX2 strrchr and wcsrchr implementation uses the 'blsmsk'
instruction which belongs to the BMI1 CPU feature and the 'shrx'
instruction, which belongs to the BMI2 CPU feature.

Fixes: df7e295d18ff ("x86: Optimize {str|wcs}rchr-avx2")
Partially resolves: BZ #29611
---
 sysdeps/x86/isa-level.h                    |  1 +
 sysdeps/x86_64/multiarch/ifunc-avx2.h      |  1 +
 sysdeps/x86_64/multiarch/ifunc-impl-list.c | 17 ++++++++++++++---
 3 files changed, 16 insertions(+), 3 deletions(-)
  

On Mon, Oct 3, 2022 at 12:59 PM Aurelien Jarno <aurelien@aurel32.net> wrote:
>
> The AVX2 strrchr and wcsrchr implementation uses the 'blsmsk'
> instruction which belongs to the BMI1 CPU feature and the 'shrx'
> instruction, which belongs to the BMI2 CPU feature.
>
> Fixes: df7e295d18ff ("x86: Optimize {str|wcs}rchr-avx2")
> Partially resolves: BZ #29611
> ---
>  sysdeps/x86/isa-level.h                    |  1 +
>  sysdeps/x86_64/multiarch/ifunc-avx2.h      |  1 +
>  sysdeps/x86_64/multiarch/ifunc-impl-list.c | 17 ++++++++++++++---
>  3 files changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/sysdeps/x86/isa-level.h b/sysdeps/x86/isa-level.h
> index bbb90f5c5e..06f6c9663e 100644
> --- a/sysdeps/x86/isa-level.h
> +++ b/sysdeps/x86/isa-level.h
> @@ -79,6 +79,7 @@
>  /* ISA level >= 3 guaranteed includes.  */
>  #define AVX_X86_ISA_LEVEL 3
>  #define AVX2_X86_ISA_LEVEL 3
> +#define BMI1_X86_ISA_LEVEL 3
>  #define BMI2_X86_ISA_LEVEL 3
>  #define LZCNT_X86_ISA_LEVEL 3
>  #define MOVBE_X86_ISA_LEVEL 3
> diff --git a/sysdeps/x86_64/multiarch/ifunc-avx2.h b/sysdeps/x86_64/multiarch/ifunc-avx2.h
> index f1741083fd..f2f5e8a211 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-avx2.h
> +++ b/sysdeps/x86_64/multiarch/ifunc-avx2.h
> @@ -36,6 +36,7 @@ IFUNC_SELECTOR (void)
>    const struct cpu_features *cpu_features = __get_cpu_features ();
>
>    if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> +      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI1)
>        && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
>        && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, LZCNT)
>        && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index ec1c5b55fb..00a91123d3 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -578,13 +578,19 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>    IFUNC_IMPL (i, name, strrchr,
>               X86_IFUNC_IMPL_ADD_V4 (array, i, strrchr,
>                                      (CPU_FEATURE_USABLE (AVX512VL)
> -                                     && CPU_FEATURE_USABLE (AVX512BW)),
> +                                     && CPU_FEATURE_USABLE (AVX512BW)
> +                                     && CPU_FEATURE_USABLE (BMI1)
> +                                     && CPU_FEATURE_USABLE (BMI2)),
>                                      __strrchr_evex)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, strrchr,
> -                                    CPU_FEATURE_USABLE (AVX2),
> +                                    (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI1)
> +                                     && CPU_FEATURE_USABLE (BMI2)),
>                                      __strrchr_avx2)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, strrchr,
>                                      (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI1)
> +                                     && CPU_FEATURE_USABLE (BMI2)
>                                       && CPU_FEATURE_USABLE (RTM)),
>                                      __strrchr_avx2_rtm)
>               /* ISA V2 wrapper for SSE2 implementation because the SSE2
> @@ -797,13 +803,18 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>               X86_IFUNC_IMPL_ADD_V4 (array, i, wcsrchr,
>                                      (CPU_FEATURE_USABLE (AVX512VL)
>                                       && CPU_FEATURE_USABLE (AVX512BW)
> +                                     && CPU_FEATURE_USABLE (BMI1)
>                                       && CPU_FEATURE_USABLE (BMI2)),
>                                      __wcsrchr_evex)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, wcsrchr,
> -                                    CPU_FEATURE_USABLE (AVX2),
> +                                    (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI1)
> +                                     && CPU_FEATURE_USABLE (BMI2)),
>                                      __wcsrchr_avx2)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, wcsrchr,
>                                      (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI1)
> +                                     && CPU_FEATURE_USABLE (BMI2)
>                                       && CPU_FEATURE_USABLE (RTM)),
>                                      __wcsrchr_avx2_rtm)
>               /* ISA V2 wrapper for SSE2 implementation because the SSE2
> --
> 2.35.1
>

LGTM.
Reviewed-by: Noah Goldstein  <goldstein.w.n@gmail.com>