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62 lines
2.6 KiB
62 lines
2.6 KiB
commit b9cbb8dd48b545f3b36b5d411481dc0bd118ee94 |
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Author: Aurelien Jarno <aurelien@aurel32.net> |
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Date: Mon Oct 3 23:16:46 2022 +0200 |
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x86-64: Require BMI2 for AVX2 strncmp implementation |
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The AVX2 strncmp implementations uses the 'bzhi' instruction, which |
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belongs to the BMI2 CPU feature. |
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NB: It also uses the 'tzcnt' BMI1 instruction, but it is executed as BSF |
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as BSF if the CPU doesn't support TZCNT, and produces the same result |
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for non-zero input. |
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Partially fixes: b77b06e0e296 ("x86: Optimize strcmp-avx2.S") |
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Partially resolves: BZ #29611 |
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Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com> |
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(cherry picked from commit fc7de1d9b99ae1676bc626ddca422d7abee0eb48) |
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diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c |
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index 70931f15985334af..34d5f6efe5421014 100644 |
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--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c |
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+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c |
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@@ -1022,15 +1022,18 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array, |
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/* Support sysdeps/x86_64/multiarch/strncmp.c. */ |
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IFUNC_IMPL (i, name, strncmp, |
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IFUNC_IMPL_ADD (array, i, strncmp, |
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- CPU_FEATURE_USABLE (AVX2), |
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+ (CPU_FEATURE_USABLE (AVX2) |
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+ && CPU_FEATURE_USABLE (BMI2)), |
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__strncmp_avx2) |
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IFUNC_IMPL_ADD (array, i, strncmp, |
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(CPU_FEATURE_USABLE (AVX2) |
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+ && CPU_FEATURE_USABLE (BMI2) |
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&& CPU_FEATURE_USABLE (RTM)), |
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__strncmp_avx2_rtm) |
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IFUNC_IMPL_ADD (array, i, strncmp, |
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(CPU_FEATURE_USABLE (AVX512VL) |
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- && CPU_FEATURE_USABLE (AVX512BW)), |
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+ && CPU_FEATURE_USABLE (AVX512BW) |
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+ && CPU_FEATURE_USABLE (BMI2)), |
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__strncmp_evex) |
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IFUNC_IMPL_ADD (array, i, strncmp, CPU_FEATURE_USABLE (SSE4_2), |
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__strncmp_sse42) |
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diff --git a/sysdeps/x86_64/multiarch/strncmp.c b/sysdeps/x86_64/multiarch/strncmp.c |
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index f94a421784bfe923..7632d7b2dd4447aa 100644 |
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--- a/sysdeps/x86_64/multiarch/strncmp.c |
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+++ b/sysdeps/x86_64/multiarch/strncmp.c |
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@@ -39,11 +39,11 @@ IFUNC_SELECTOR (void) |
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const struct cpu_features* cpu_features = __get_cpu_features (); |
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if (CPU_FEATURE_USABLE_P (cpu_features, AVX2) |
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+ && CPU_FEATURE_USABLE_P (cpu_features, BMI2) |
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&& CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load)) |
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{ |
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if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL) |
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- && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW) |
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- && CPU_FEATURE_USABLE_P (cpu_features, BMI2)) |
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+ && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)) |
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return OPTIMIZE (evex); |
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if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
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