[COMMITTED 2.36 5/8] x86-64: Require BMI2 for AVX2 wcs(n)cmp implementations

[Aurelien Jarno]

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)
---
 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 aebef3daaf..fec8790c11 100644
--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
@@ -810,10 +810,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcscmp_evex)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcscmp,
-				     CPU_FEATURE_USABLE (AVX2),
+				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcscmp_avx2)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcscmp,
 				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)
 				      && CPU_FEATURE_USABLE (RTM)),
 				     __wcscmp_avx2_rtm)
 	      /* ISA V2 wrapper for SSE2 implementation because the SSE2
@@ -830,10 +832,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcsncmp_evex)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcsncmp,
-				     CPU_FEATURE_USABLE (AVX2),
+				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)),
 				     __wcsncmp_avx2)
 	      X86_IFUNC_IMPL_ADD_V3 (array, i, wcsncmp,
 				     (CPU_FEATURE_USABLE (AVX2)
+				      && CPU_FEATURE_USABLE (BMI2)
 				      && CPU_FEATURE_USABLE (RTM)),
 				     __wcsncmp_avx2_rtm)
 	      /* ISA V2 wrapper for GENERIC implementation because the
-- 
2.35.1