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commit 67e863742d98c990b3d3b814b80042c0fa0d50a5
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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 wcs(n)cmp implementations
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The AVX2 wcs(n)cmp implementations use 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 f31a5a884ed84bd37032729d4d1eb9d06c9f3c29)
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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 34d5f6efe5421014..e76a991dc671c1a9 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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@@ -693,10 +693,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
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/* Support sysdeps/x86_64/multiarch/wcscmp.c. */
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IFUNC_IMPL (i, name, wcscmp,
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IFUNC_IMPL_ADD (array, i, wcscmp,
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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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__wcscmp_avx2)
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IFUNC_IMPL_ADD (array, i, wcscmp,
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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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__wcscmp_avx2_rtm)
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IFUNC_IMPL_ADD (array, i, wcscmp,
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@@ -709,10 +711,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
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/* Support sysdeps/x86_64/multiarch/wcsncmp.c. */
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IFUNC_IMPL (i, name, wcsncmp,
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IFUNC_IMPL_ADD (array, i, wcsncmp,
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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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__wcsncmp_avx2)
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IFUNC_IMPL_ADD (array, i, wcsncmp,
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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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__wcsncmp_avx2_rtm)
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IFUNC_IMPL_ADD (array, i, wcsncmp,
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