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[v3,5/8] x86-64: Require BMI2 for AVX2 wcs(n)cmp implementations

Message ID 20221003195944.3274548-6-aurelien@aurel32.net
State New
Headers show
Series x86: Fix AVX2 string functions requiring BMI1, BMI2 or LZCNT (BZ #29611) | expand

Commit Message

Aurelien Jarno Oct. 3, 2022, 7:59 p.m. UTC
The AVX2 wcs(n)cmp implementations use the 'bzhi' instruction, which
belongs to the BMI2 CPU feature.

NB: It also uses the 'tzcnt' BMI1 instruction, but it is executed as BSF
as BSF if the CPU doesn't support TZCNT, and produces the same result
for non-zero input.

Partially fixes: b77b06e0e296 ("x86: Optimize strcmp-avx2.S")
Partially resolves: BZ #29611
---
 sysdeps/x86_64/multiarch/ifunc-impl-list.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Noah Goldstein Oct. 3, 2022, 9:11 p.m. UTC | #1
On Mon, Oct 3, 2022 at 12:59 PM Aurelien Jarno <aurelien@aurel32.net> wrote:
>
> The AVX2 wcs(n)cmp implementations use the 'bzhi' instruction, which
> belongs to the BMI2 CPU feature.
>
> NB: It also uses the 'tzcnt' BMI1 instruction, but it is executed as BSF
> as BSF if the CPU doesn't support TZCNT, and produces the same result
> for non-zero input.
>
> Partially fixes: b77b06e0e296 ("x86: Optimize strcmp-avx2.S")
> Partially resolves: BZ #29611
> ---
>  sysdeps/x86_64/multiarch/ifunc-impl-list.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index aebef3daaf..fec8790c11 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -810,10 +810,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>                                       && CPU_FEATURE_USABLE (BMI2)),
>                                      __wcscmp_evex)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, wcscmp,
> -                                    CPU_FEATURE_USABLE (AVX2),
> +                                    (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI2)),
>                                      __wcscmp_avx2)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, wcscmp,
>                                      (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI2)
>                                       && CPU_FEATURE_USABLE (RTM)),
>                                      __wcscmp_avx2_rtm)
>               /* ISA V2 wrapper for SSE2 implementation because the SSE2
> @@ -830,10 +832,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>                                       && CPU_FEATURE_USABLE (BMI2)),
>                                      __wcsncmp_evex)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, wcsncmp,
> -                                    CPU_FEATURE_USABLE (AVX2),
> +                                    (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI2)),
>                                      __wcsncmp_avx2)
>               X86_IFUNC_IMPL_ADD_V3 (array, i, wcsncmp,
>                                      (CPU_FEATURE_USABLE (AVX2)
> +                                     && CPU_FEATURE_USABLE (BMI2)
>                                       && CPU_FEATURE_USABLE (RTM)),
>                                      __wcsncmp_avx2_rtm)
>               /* ISA V2 wrapper for GENERIC implementation because the
> --
> 2.35.1
>
LGTM.
Reviewed-by: Noah Goldstein  <goldstein.w.n@gmail.com>
diff mbox series

Patch

diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
index aebef3daaf..fec8790c11 100644
--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
@@ -810,10 +810,12 @@  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcscmp_evex)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcscmp,
-				     CPU_FEATURE_USABLE (AVX2),
+				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcscmp_avx2)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcscmp,
 				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)
 				      && CPU_FEATURE_USABLE (RTM)),
 				     __wcscmp_avx2_rtm)
 	      /* ISA V2 wrapper for SSE2 implementation because the SSE2
@@ -830,10 +832,12 @@  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcsncmp_evex)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcsncmp,
-				     CPU_FEATURE_USABLE (AVX2),
+				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcsncmp_avx2)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcsncmp,
 				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)
 				      && CPU_FEATURE_USABLE (RTM)),
 				     __wcsncmp_avx2_rtm)
 	      /* ISA V2 wrapper for GENERIC implementation because the