File dl-runtime-resolve-opt-avx512f.patch of Package glibc.10713
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;