x86-64: Require BMI2 for AVX2 str(n)casecmp implementations

The AVX2 str(n)casecmp 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>

diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
index a71444eccb3cb7cf59775408b3b2524397aaa2ec..d208fae4bfc57c3d09225b12668641cb8a8b6369 100644 (file)
--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
@@ -448,13 +448,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strcasecmp,
              X86_IFUNC_IMPL_ADD_V4 (array, i, strcasecmp,
                                     (CPU_FEATURE_USABLE (AVX512VL)
-                                     && CPU_FEATURE_USABLE (AVX512BW)),
+                                     && CPU_FEATURE_USABLE (AVX512BW)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strcasecmp_evex)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strcasecmp,
-                                    CPU_FEATURE_USABLE (AVX2),
+                                    (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strcasecmp_avx2)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strcasecmp,
                                     (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)
                                      && CPU_FEATURE_USABLE (RTM)),
                                     __strcasecmp_avx2_rtm)
              X86_IFUNC_IMPL_ADD_V2 (array, i, strcasecmp,
@@ -470,13 +473,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strcasecmp_l,
              X86_IFUNC_IMPL_ADD_V4 (array, i, strcasecmp,
                                     (CPU_FEATURE_USABLE (AVX512VL)
-                                     && CPU_FEATURE_USABLE (AVX512BW)),
+                                     && CPU_FEATURE_USABLE (AVX512BW)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strcasecmp_l_evex)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strcasecmp,
-                                    CPU_FEATURE_USABLE (AVX2),
+                                    (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strcasecmp_l_avx2)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strcasecmp,
                                     (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)
                                      && CPU_FEATURE_USABLE (RTM)),
                                     __strcasecmp_l_avx2_rtm)
              X86_IFUNC_IMPL_ADD_V2 (array, i, strcasecmp_l,
@@ -638,13 +644,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strncasecmp,
              X86_IFUNC_IMPL_ADD_V4 (array, i, strncasecmp,
                                     (CPU_FEATURE_USABLE (AVX512VL)
-                                     && CPU_FEATURE_USABLE (AVX512BW)),
+                                     && CPU_FEATURE_USABLE (AVX512BW)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strncasecmp_evex)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strncasecmp,
-                                    CPU_FEATURE_USABLE (AVX2),
+                                    (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strncasecmp_avx2)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strncasecmp,
                                     (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)
                                      && CPU_FEATURE_USABLE (RTM)),
                                     __strncasecmp_avx2_rtm)
              X86_IFUNC_IMPL_ADD_V2 (array, i, strncasecmp,
@@ -660,13 +669,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strncasecmp_l,
              X86_IFUNC_IMPL_ADD_V4 (array, i, strncasecmp,
                                     (CPU_FEATURE_USABLE (AVX512VL)
-                                     && CPU_FEATURE_USABLE (AVX512BW)),
+                                     & CPU_FEATURE_USABLE (AVX512BW)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strncasecmp_l_evex)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strncasecmp,
-                                    CPU_FEATURE_USABLE (AVX2),
+                                    (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)),
                                     __strncasecmp_l_avx2)
              X86_IFUNC_IMPL_ADD_V3 (array, i, strncasecmp,
                                     (CPU_FEATURE_USABLE (AVX2)
+                                     && CPU_FEATURE_USABLE (BMI2)
                                      && CPU_FEATURE_USABLE (RTM)),
                                     __strncasecmp_l_avx2_rtm)
              X86_IFUNC_IMPL_ADD_V2 (array, i, strncasecmp_l,

diff --git a/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h b/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h
index 68646ef199ecb71ce93af9cdc98460c2c771437a..7622af259ca5c08fb0d7c0943d67c2cd5dc85cac 100644 (file)
--- a/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h
+++ b/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h
@@ -34,6 +34,7 @@ IFUNC_SELECTOR (void)
   const struct cpu_features *cpu_features = __get_cpu_features ();
 
   if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
+      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
       && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
                                      AVX_Fast_Unaligned_Load, ))
     {