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| author | Aurelien Jarno <aurelien@aurel32.net> | 2022-10-03 23:46:11 +0200 |
|---|---|---|
| committer | Aurelien Jarno <aurelien@aurel32.net> | 2022-10-03 23:46:11 +0200 |
| commit | 4d64c6445735e9b34e2ac8e369312cbfc2f88e17 (patch) | |
| tree | b7a3a4be592c3e14f661db4f209e337c6185f9ee | |
| parent | 10f79d3670b036925da63dc532b122d27ce65ff8 (diff) | |
| download | glibc-4d64c6445735e9b34e2ac8e369312cbfc2f88e17.zip glibc-4d64c6445735e9b34e2ac8e369312cbfc2f88e17.tar.gz glibc-4d64c6445735e9b34e2ac8e369312cbfc2f88e17.tar.bz2 | |
x86-64: Require BMI2 for AVX2 strcmp implementation
The AVX2 strcmp implementation uses 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
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
| -rw-r--r-- | sysdeps/x86_64/multiarch/ifunc-impl-list.c | 4 | ||||
| -rw-r--r-- | sysdeps/x86_64/multiarch/strcmp.c | 4 |
2 files changed, 5 insertions, 3 deletions
diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c index d208fae..a42b0a4 100644 --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c @@ -591,10 +591,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array, && CPU_FEATURE_USABLE (BMI2)), __strcmp_evex) X86_IFUNC_IMPL_ADD_V3 (array, i, strcmp, - CPU_FEATURE_USABLE (AVX2), + (CPU_FEATURE_USABLE (AVX2) + && CPU_FEATURE_USABLE (BMI2)), __strcmp_avx2) X86_IFUNC_IMPL_ADD_V3 (array, i, strcmp, (CPU_FEATURE_USABLE (AVX2) + && CPU_FEATURE_USABLE (BMI2) && CPU_FEATURE_USABLE (RTM)), __strcmp_avx2_rtm) X86_IFUNC_IMPL_ADD_V2 (array, i, strcmp, diff --git a/sysdeps/x86_64/multiarch/strcmp.c b/sysdeps/x86_64/multiarch/strcmp.c index fdd5afe..9d6c9f6 100644 --- a/sysdeps/x86_64/multiarch/strcmp.c +++ b/sysdeps/x86_64/multiarch/strcmp.c @@ -45,12 +45,12 @@ 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, BMI2) && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load, )) { if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL) - && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) - && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)) + && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)) return OPTIMIZE (evex); if (CPU_FEATURE_USABLE_P (cpu_features, RTM)) |