From: Aurelien Jarno <aurelien@aurel32.net>
Date: Mon, 3 Oct 2022 21:16:46 +0000 (+0200)
Subject: x86-64: Require BMI1/BMI2 for AVX2 strrchr and wcsrchr implementations
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=67e310afb91fa27295f7cf5140176efd6ba5dd51;p=thirdparty%2Fglibc.git

x86-64: Require BMI1/BMI2 for AVX2 strrchr and wcsrchr implementations

The AVX2 strrchr and wcsrchr implementation uses the 'blsmsk'
instruction which belongs to the BMI1 CPU feature and the 'shrx'
instruction, which belongs to the BMI2 CPU feature.

Fixes: df7e295d18ff ("x86: Optimize {str|wcs}rchr-avx2")
Partially resolves: BZ #29611

Reviewed-by: Noah Goldstein  <goldstein.w.n@gmail.com>
(cherry picked from commit 7e8283170c5d6805b609a040801d819e362a6292)
---

diff --git a/sysdeps/x86_64/multiarch/ifunc-avx2.h b/sysdeps/x86_64/multiarch/ifunc-avx2.h
index 52bd00ea5ca..877f007dd6e 100644
--- a/sysdeps/x86_64/multiarch/ifunc-avx2.h
+++ b/sysdeps/x86_64/multiarch/ifunc-avx2.h
@@ -30,6 +30,7 @@ IFUNC_SELECTOR (void)
   const struct cpu_features* cpu_features = __get_cpu_features ();
 
   if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
+      && CPU_FEATURE_USABLE_P (cpu_features, BMI1)
       && CPU_FEATURE_USABLE_P (cpu_features, BMI2)
       && CPU_FEATURE_USABLE_P (cpu_features, LZCNT)
       && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
index d1fc1e75d67..84f9e73e2b7 100644
--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
@@ -498,15 +498,21 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   /* Support sysdeps/x86_64/multiarch/strrchr.c.  */
   IFUNC_IMPL (i, name, strrchr,
 	      IFUNC_IMPL_ADD (array, i, strrchr,
-			      CPU_FEATURE_USABLE (AVX2),
+			      (CPU_FEATURE_USABLE (AVX2)
+			       && CPU_FEATURE_USABLE (BMI1)
+			       && CPU_FEATURE_USABLE (BMI2)),
 			      __strrchr_avx2)
 	      IFUNC_IMPL_ADD (array, i, strrchr,
 			      (CPU_FEATURE_USABLE (AVX2)
+			       && CPU_FEATURE_USABLE (BMI1)
+			       && CPU_FEATURE_USABLE (BMI2)
 			       && CPU_FEATURE_USABLE (RTM)),
 			      __strrchr_avx2_rtm)
 	      IFUNC_IMPL_ADD (array, i, strrchr,
 			      (CPU_FEATURE_USABLE (AVX512VL)
-			       && CPU_FEATURE_USABLE (AVX512BW)),
+			       && CPU_FEATURE_USABLE (AVX512BW)
+			       && CPU_FEATURE_USABLE (BMI1)
+			       && CPU_FEATURE_USABLE (BMI2)),
 			      __strrchr_evex)
 	      IFUNC_IMPL_ADD (array, i, strrchr, 1, __strrchr_sse2))
 
@@ -687,15 +693,20 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   /* Support sysdeps/x86_64/multiarch/wcsrchr.c.  */
   IFUNC_IMPL (i, name, wcsrchr,
 	      IFUNC_IMPL_ADD (array, i, wcsrchr,
-			      CPU_FEATURE_USABLE (AVX2),
+			      (CPU_FEATURE_USABLE (AVX2)
+			       && CPU_FEATURE_USABLE (BMI1)
+			       && CPU_FEATURE_USABLE (BMI2)),
 			      __wcsrchr_avx2)
 	      IFUNC_IMPL_ADD (array, i, wcsrchr,
 			      (CPU_FEATURE_USABLE (AVX2)
+			       && CPU_FEATURE_USABLE (BMI1)
+			       && CPU_FEATURE_USABLE (BMI2)
 			       && CPU_FEATURE_USABLE (RTM)),
 			      __wcsrchr_avx2_rtm)
 	      IFUNC_IMPL_ADD (array, i, wcsrchr,
 			      (CPU_FEATURE_USABLE (AVX512VL)
 			       && CPU_FEATURE_USABLE (AVX512BW)
+			       && CPU_FEATURE_USABLE (BMI1)
 			       && CPU_FEATURE_USABLE (BMI2)),
 			      __wcsrchr_evex)
 	      IFUNC_IMPL_ADD (array, i, wcsrchr, 1, __wcsrchr_sse2))