File dl-runtime-resolve-opt-avx512f.patch of Package glibc.22972

2017-08-06  H.J. Lu  <hongjiu.lu@intel.com>

	[BZ #21871]
	* sysdeps/x86/cpu-features.c (init_cpu_features): Set
	bit_arch_Use_dl_runtime_resolve_opt only with AVX512F.

Index: glibc-2.26/sysdeps/x86/cpu-features.c
===================================================================
--- glibc-2.26.orig/sysdeps/x86/cpu-features.c
+++ glibc-2.26/sysdeps/x86/cpu-features.c
@@ -244,10 +244,13 @@ init_cpu_features (struct cpu_features *
 	  |= bit_arch_Prefer_No_AVX512;
 
       /* To avoid SSE transition penalty, use _dl_runtime_resolve_slow.
-         If XGETBV suports ECX == 1, use _dl_runtime_resolve_opt.  */
+         If XGETBV suports ECX == 1, use _dl_runtime_resolve_opt.
+	 Use _dl_runtime_resolve_opt only with AVX512F since it is
+	 slower than _dl_runtime_resolve_slow with AVX.  */
       cpu_features->feature[index_arch_Use_dl_runtime_resolve_slow]
 	|= bit_arch_Use_dl_runtime_resolve_slow;
-      if (cpu_features->max_cpuid >= 0xd)
+      if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable)
+	  && cpu_features->max_cpuid >= 0xd)
 	{
 	  unsigned int eax;