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>
(cherry picked from commit 10f79d3670b036925da63dc532b122d27ce65ff8)

diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
index 8d649e263eb24b8a284f39094a6081e612cc42a9..ca64b34c146a76f919cda01000167d8a0230a2c2 100644 (file)
--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
@@ -386,13 +386,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strcasecmp,
              IFUNC_IMPL_ADD (array, i, strcasecmp,
                              (CPU_FEATURE_USABLE (AVX512VL)
-                              && CPU_FEATURE_USABLE (AVX512BW)),
+                              && CPU_FEATURE_USABLE (AVX512BW)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strcasecmp_evex)
              IFUNC_IMPL_ADD (array, i, strcasecmp,
-                             CPU_FEATURE_USABLE (AVX2),
+                             (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strcasecmp_avx2)
              IFUNC_IMPL_ADD (array, i, strcasecmp,
                              (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)
                               && CPU_FEATURE_USABLE (RTM)),
                              __strcasecmp_avx2_rtm)
              IFUNC_IMPL_ADD (array, i, strcasecmp,
@@ -407,13 +410,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strcasecmp_l,
              IFUNC_IMPL_ADD (array, i, strcasecmp,
                              (CPU_FEATURE_USABLE (AVX512VL)
-                              && CPU_FEATURE_USABLE (AVX512BW)),
+                              && CPU_FEATURE_USABLE (AVX512BW)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strcasecmp_l_evex)
              IFUNC_IMPL_ADD (array, i, strcasecmp,
-                             CPU_FEATURE_USABLE (AVX2),
+                             (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strcasecmp_l_avx2)
              IFUNC_IMPL_ADD (array, i, strcasecmp,
                              (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)
                               && CPU_FEATURE_USABLE (RTM)),
                              __strcasecmp_l_avx2_rtm)
              IFUNC_IMPL_ADD (array, i, strcasecmp_l,
@@ -542,13 +548,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strncasecmp,
              IFUNC_IMPL_ADD (array, i, strncasecmp,
                              (CPU_FEATURE_USABLE (AVX512VL)
-                              && CPU_FEATURE_USABLE (AVX512BW)),
+                              && CPU_FEATURE_USABLE (AVX512BW)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strncasecmp_evex)
              IFUNC_IMPL_ADD (array, i, strncasecmp,
-                             CPU_FEATURE_USABLE (AVX2),
+                             (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strncasecmp_avx2)
              IFUNC_IMPL_ADD (array, i, strncasecmp,
                              (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)
                               && CPU_FEATURE_USABLE (RTM)),
                              __strncasecmp_avx2_rtm)
              IFUNC_IMPL_ADD (array, i, strncasecmp,
@@ -564,13 +573,16 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strncasecmp_l,
              IFUNC_IMPL_ADD (array, i, strncasecmp,
                              (CPU_FEATURE_USABLE (AVX512VL)
-                              && CPU_FEATURE_USABLE (AVX512BW)),
+                              & CPU_FEATURE_USABLE (AVX512BW)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strncasecmp_l_evex)
              IFUNC_IMPL_ADD (array, i, strncasecmp,
-                             CPU_FEATURE_USABLE (AVX2),
+                             (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)),
                              __strncasecmp_l_avx2)
              IFUNC_IMPL_ADD (array, i, strncasecmp,
                              (CPU_FEATURE_USABLE (AVX2)
+                              && CPU_FEATURE_USABLE (BMI2)
                               && CPU_FEATURE_USABLE (RTM)),
                              __strncasecmp_l_avx2_rtm)
              IFUNC_IMPL_ADD (array, i, strncasecmp_l,

diff --git a/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h b/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h
index 40819caf5ab10337e69e0daa297e3b9eebc456c0..e61d6e9497bce9d92657c2550515f34cbd377615 100644 (file)
--- a/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h
+++ b/sysdeps/x86_64/multiarch/ifunc-strcasecmp.h
@@ -32,6 +32,7 @@ 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, BMI2)
       && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
     {
       if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)