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From: Aurelien Jarno <aurel32@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/release/2.35/master] x86-64: Require BMI2 for AVX2 wcs(n)cmp implementations Date: Mon, 3 Oct 2022 21:55:59 +0000 (GMT) [thread overview] Message-ID: <20221003215559.DBD2F3857BB2@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1523fbedff44273c15cb60e269872ff761f574c7 commit 1523fbedff44273c15cb60e269872ff761f574c7 Author: Aurelien Jarno <aurelien@aurel32.net> Date: Mon Oct 3 23:16:46 2022 +0200 x86-64: Require BMI2 for AVX2 wcs(n)cmp implementations The AVX2 wcs(n)cmp implementations use 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> (cherry picked from commit f31a5a884ed84bd37032729d4d1eb9d06c9f3c29) Diff: --- sysdeps/x86_64/multiarch/ifunc-impl-list.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c index b27ae975e4..5824554b4e 100644 --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c @@ -711,10 +711,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array, /* Support sysdeps/x86_64/multiarch/wcscmp.c. */ IFUNC_IMPL (i, name, wcscmp, IFUNC_IMPL_ADD (array, i, wcscmp, - CPU_FEATURE_USABLE (AVX2), + (CPU_FEATURE_USABLE (AVX2) + && CPU_FEATURE_USABLE (BMI2)), __wcscmp_avx2) IFUNC_IMPL_ADD (array, i, wcscmp, (CPU_FEATURE_USABLE (AVX2) + && CPU_FEATURE_USABLE (BMI2) && CPU_FEATURE_USABLE (RTM)), __wcscmp_avx2_rtm) IFUNC_IMPL_ADD (array, i, wcscmp, @@ -727,10 +729,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array, /* Support sysdeps/x86_64/multiarch/wcsncmp.c. */ IFUNC_IMPL (i, name, wcsncmp, IFUNC_IMPL_ADD (array, i, wcsncmp, - CPU_FEATURE_USABLE (AVX2), + (CPU_FEATURE_USABLE (AVX2) + && CPU_FEATURE_USABLE (BMI2)), __wcsncmp_avx2) IFUNC_IMPL_ADD (array, i, wcsncmp, (CPU_FEATURE_USABLE (AVX2) + && CPU_FEATURE_USABLE (BMI2) && CPU_FEATURE_USABLE (RTM)), __wcsncmp_avx2_rtm) IFUNC_IMPL_ADD (array, i, wcsncmp,
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