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From: "H.J. Lu" <hjl.tools@gmail.com>
To: libc-alpha@sourceware.org
Subject: [PATCH] x86: Don't set Prefer_No_AVX512 for processors with AVX512 and AVX-VNNI
Date: Sun,  5 Dec 2021 19:23:03 -0800	[thread overview]
Message-ID: <20211206032303.7159-1-hjl.tools@gmail.com> (raw)

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.
---
 sysdeps/x86/cpu-features.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index be2498b2e7..311ade1f26 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -538,8 +538,11 @@ init_cpu_features (struct cpu_features *cpu_features)
 	  |= 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.  */
-- 
2.33.1


             reply	other threads:[~2021-12-06  3:23 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-06  3:23 H.J. Lu [this message]
2021-12-07  7:47 ` Noah Goldstein
2021-12-07 12:53   ` H.J. Lu
2021-12-07 13:17     ` Arjan van de Ven
2021-12-07 13:34       ` H.J. Lu
2021-12-07 14:05         ` Florian Weimer
2021-12-07 14:15           ` H.J. Lu
2021-12-07 15:47             ` Florian Weimer
2021-12-07 15:52               ` H.J. Lu
2021-12-07 16:22                 ` Thiago Macieira
2021-12-07 19:32                 ` Noah Goldstein
2022-04-23  1:51                   ` Sunil Pandey

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