From f64058914af3c3a429e5947a8a90220240f7d51b Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 6 Dec 2021 07:14:12 -0800
Subject: [PATCH] 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)
---
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 956bfb4f..5ff2baa0 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -525,8 +525,11 @@ 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. */
--
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