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57 lines
2.4 KiB
57 lines
2.4 KiB
1 year ago
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commit 36d6b9be3d7008a78e1f6e2e2db1947b76b206d8
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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 and LZCNT for AVX2 memrchr implementation
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The AVX2 memrchr implementation uses the 'shlxl' instruction, which
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belongs to the BMI2 CPU feature and uses the 'lzcnt' instruction, which
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belongs to the LZCNT CPU feature.
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Fixes: af5306a735eb ("x86: Optimize memrchr-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 3c0c78afabfed4b6fc161c159e628fbf14ff370b)
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diff --git a/sysdeps/x86_64/multiarch/ifunc-avx2.h b/sysdeps/x86_64/multiarch/ifunc-avx2.h
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index 6de72f72724b81ba..52bd00ea5cab6b22 100644
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--- a/sysdeps/x86_64/multiarch/ifunc-avx2.h
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+++ b/sysdeps/x86_64/multiarch/ifunc-avx2.h
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@@ -31,6 +31,7 @@ IFUNC_SELECTOR (void)
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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_FEATURE_USABLE_P (cpu_features, LZCNT)
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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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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 81640cf00664e3ed..d1fc1e75d6706413 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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@@ -174,15 +174,21 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
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/* Support sysdeps/x86_64/multiarch/memrchr.c. */
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IFUNC_IMPL (i, name, memrchr,
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IFUNC_IMPL_ADD (array, i, memrchr,
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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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+ && CPU_FEATURE_USABLE (LZCNT)),
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__memrchr_avx2)
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IFUNC_IMPL_ADD (array, i, memrchr,
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(CPU_FEATURE_USABLE (AVX2)
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+ && CPU_FEATURE_USABLE (BMI2)
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+ && CPU_FEATURE_USABLE (LZCNT)
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&& CPU_FEATURE_USABLE (RTM)),
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__memrchr_avx2_rtm)
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IFUNC_IMPL_ADD (array, i, memrchr,
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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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+ && CPU_FEATURE_USABLE (LZCNT)),
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__memrchr_evex)
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IFUNC_IMPL_ADD (array, i, memrchr, 1, __memrchr_sse2))
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