From: H.J. Lu <hjl.tools@gmail.com>
Date: Mon, 6 Dec 2021 15:14:12 +0000 (-0800)
Subject: x86: Don't set Prefer_No_AVX512 for processors with AVX512 and AVX-VNNI
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=63fd074112505b4b3faf74070db8c3698fe9235c;p=thirdparty%2Fglibc.git

x86: Don't set Prefer_No_AVX512 for processors with AVX512 and AVX-VNNI

Don't set Prefer_No_AVX512 on processors with AVX512 and AVX-VNNI since
they won't lower CPU frequency when ZMM load and store instructions are
used.

(cherry picked from commit ceeffe968c01b1202e482f4855cb6baf5c6cb713)
---

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index e7dc25aaf53..42b02d1d339 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -555,8 +555,11 @@ disable_tsx:
 	  |= bit_arch_Prefer_No_VZEROUPPER;
       else
 	{
-	  cpu_features->preferred[index_arch_Prefer_No_AVX512]
-	    |= bit_arch_Prefer_No_AVX512;
+	  /* Processors with AVX512 and AVX-VNNI won't lower CPU frequency
+	     when ZMM load and store instructions are used.  */
+	  if (!CPU_FEATURES_CPU_P (cpu_features, AVX_VNNI))
+	    cpu_features->preferred[index_arch_Prefer_No_AVX512]
+	      |= bit_arch_Prefer_No_AVX512;
 
 	  /* Avoid RTM abort triggered by VZEROUPPER inside a
 	     transactionally executing RTM region.  */