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x86-64: Require BMI2 for AVX2 wcs(n)cmp implementations

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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: b77b06e0e2 ("x86: Optimize strcmp-avx2.S")
Partially resolves: BZ #29611

Reviewed-by: Noah Goldstein  <goldstein.w.n@gmail.com>
(cherry picked from commit f31a5a884e)
This commit is contained in:
Aurelien Jarno 2022-10-03 23:16:46 +02:00
parent b9cbb8dd48
commit 67e863742d
1 changed files with 6 additions and 2 deletions
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8
sysdeps/x86_64/multiarch/ifunc-impl-list.c
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@ -693,10 +693,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
/* Support sysdeps/x86_64/multiarch/wcscmp.c. */
IFUNC_IMPL (i, name, wcscmp,
IFUNC_IMPL_ADD (array, i, wcscmp,
CPU_FEATURE_USABLE (AVX2),
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (BMI2)),
__wcscmp_avx2)
IFUNC_IMPL_ADD (array, i, wcscmp,
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (BMI2)
&& CPU_FEATURE_USABLE (RTM)),
__wcscmp_avx2_rtm)
IFUNC_IMPL_ADD (array, i, wcscmp,
@ -709,10 +711,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
/* Support sysdeps/x86_64/multiarch/wcsncmp.c. */
IFUNC_IMPL (i, name, wcsncmp,
IFUNC_IMPL_ADD (array, i, wcsncmp,
CPU_FEATURE_USABLE (AVX2),
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (BMI2)),
__wcsncmp_avx2)
IFUNC_IMPL_ADD (array, i, wcsncmp,
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (BMI2)
&& CPU_FEATURE_USABLE (RTM)),
__wcsncmp_avx2_rtm)
IFUNC_IMPL_ADD (array, i, wcsncmp,