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x86-64: Require BMI2 and LZCNT for AVX2 memrchr implementation

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The AVX2 memrchr implementation uses the 'shlxl' instruction, which
belongs to the BMI2 CPU feature and uses the 'lzcnt' instruction, which
belongs to the LZCNT CPU feature.

Fixes: af5306a735eb ("x86: Optimize memrchr-avx2.S")
Partially resolves: BZ #29611

Reviewed-by: Noah Goldstein  <goldstein.w.n@gmail.com>
(cherry picked from commit 3c0c78afabfed4b6fc161c159e628fbf14ff370b)
This commit is contained in:
Aurelien Jarno 2022-10-03 23:16:46 +02:00
parent 94b9c1b640
commit 36d6b9be3d
2 changed files with 9 additions and 2 deletions
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1
sysdeps/x86_64/multiarch/ifunc-avx2.h
View File

@ -31,6 +31,7 @@ IFUNC_SELECTOR (void)
if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
&& CPU_FEATURE_USABLE_P (cpu_features, BMI2)
&& CPU_FEATURE_USABLE_P (cpu_features, LZCNT)
&& CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
{
if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)

10
sysdeps/x86_64/multiarch/ifunc-impl-list.c
View File

@ -174,15 +174,21 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
/* Support sysdeps/x86_64/multiarch/memrchr.c. */
IFUNC_IMPL (i, name, memrchr,
IFUNC_IMPL_ADD (array, i, memrchr,
CPU_FEATURE_USABLE (AVX2),
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (BMI2)
&& CPU_FEATURE_USABLE (LZCNT)),
__memrchr_avx2)
IFUNC_IMPL_ADD (array, i, memrchr,
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (BMI2)
&& CPU_FEATURE_USABLE (LZCNT)
&& CPU_FEATURE_USABLE (RTM)),
__memrchr_avx2_rtm)
IFUNC_IMPL_ADD (array, i, memrchr,
(CPU_FEATURE_USABLE (AVX512VL)
&& CPU_FEATURE_USABLE (AVX512BW)),
&& CPU_FEATURE_USABLE (AVX512BW)
&& CPU_FEATURE_USABLE (BMI2)
&& CPU_FEATURE_USABLE (LZCNT)),
__memrchr_evex)
IFUNC_IMPL_ADD (array, i, memrchr, 1, __memrchr_sse2))