[PATCH v1] x86: Add support for building strstr with explicit ISA level

[Noah Goldstein <goldstein.w.n@gmail.com>]

Small changes for this function as the generic implementation remains
the same for all ISA levels.

Only changes are using the X86_ISA_CPU_FEATURE{S}_{USABLE|ARCH}_P
macros so that some of the checks at least can constant evaluate
and some comments explaining the ISA constraints on the function.
---
 sysdeps/x86_64/multiarch/ifunc-impl-list.c | 13 +++++++------
 sysdeps/x86_64/multiarch/strstr.c          | 10 +++++-----
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
index 0d28319905..a1bff560bc 100644
--- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
@@ -620,12 +620,13 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   /* Support sysdeps/x86_64/multiarch/strstr.c.  */
   IFUNC_IMPL (i, name, strstr,
-              IFUNC_IMPL_ADD (array, i, strstr,
-                              (CPU_FEATURE_USABLE (AVX512VL)
-                               && CPU_FEATURE_USABLE (AVX512BW)
-                               && CPU_FEATURE_USABLE (AVX512DQ)
-                               && CPU_FEATURE_USABLE (BMI2)),
-                              __strstr_avx512)
+	      /* All implementations of strstr are built at all ISA levels.  */
+	      IFUNC_IMPL_ADD (array, i, strstr,
+			      (CPU_FEATURE_USABLE (AVX512VL)
+			       && CPU_FEATURE_USABLE (AVX512BW)
+			       && CPU_FEATURE_USABLE (AVX512DQ)
+			       && CPU_FEATURE_USABLE (BMI2)),
+			       __strstr_avx512)
 	      IFUNC_IMPL_ADD (array, i, strstr, 1, __strstr_sse2_unaligned)
 	      IFUNC_IMPL_ADD (array, i, strstr, 1, __strstr_generic))
 
diff --git a/sysdeps/x86_64/multiarch/strstr.c b/sysdeps/x86_64/multiarch/strstr.c
index 2b83199245..3f86bfa5f2 100644
--- a/sysdeps/x86_64/multiarch/strstr.c
+++ b/sysdeps/x86_64/multiarch/strstr.c
@@ -49,13 +49,13 @@ IFUNC_SELECTOR (void)
   const struct cpu_features *cpu_features = __get_cpu_features ();
 
   if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_AVX512)
-      && CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
-      && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
-      && CPU_FEATURE_USABLE_P (cpu_features, AVX512DQ)
-      && CPU_FEATURE_USABLE_P (cpu_features, BMI2))
+      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
+      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
+      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512DQ)
+      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2))
     return __strstr_avx512;
 
-  if (CPU_FEATURES_ARCH_P (cpu_features, Fast_Unaligned_Load))
+  if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features, Fast_Unaligned_Load, ))
     return __strstr_sse2_unaligned;
 
   return __strstr_generic;
-- 
2.34.1