From 01b5cac929a3be361dd575bed6673c40a25a6d61 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Wed, 14 Aug 2024 14:37:30 +0800
Subject: [PATCH 08/10] x86: Use `Avoid_Non_Temporal_Memset` to control
 non-temporal path

This is just a refactor and there should be no behavioral change from
this commit.

The goal is to make `Avoid_Non_Temporal_Memset` a more universal knob
for controlling whether we use non-temporal memset rather than having
extra logic based on vendor.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
---
 sysdeps/x86/cpu-features.c | 16 ++++++++++++++++
 sysdeps/x86/dl-cacheinfo.h | 15 +++++++--------
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index b4030776a7..c9f2297524 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -640,6 +640,12 @@ init_cpu_features (struct cpu_features *cpu_features)
   unsigned int stepping = 0;
   enum cpu_features_kind kind;
 
+  /* Default is avoid non-temporal memset for non Intel/AMD hardware. This is,
+     as of writing this, we only have benchmarks indicatings it profitability
+     on Intel/AMD.  */
+  cpu_features->preferred[index_arch_Avoid_Non_Temporal_Memset]
+      |= bit_arch_Avoid_Non_Temporal_Memset;
+
   cpu_features->cachesize_non_temporal_divisor = 4;
 #if !HAS_CPUID
   if (__get_cpuid_max (0, 0) == 0)
@@ -665,6 +671,11 @@ init_cpu_features (struct cpu_features *cpu_features)
 
       update_active (cpu_features);
 
+      /* Benchmarks indicate non-temporal memset can be profitable on Intel
+	hardware.  */
+      cpu_features->preferred[index_arch_Avoid_Non_Temporal_Memset]
+	  &= ~bit_arch_Avoid_Non_Temporal_Memset;
+
       if (family == 0x06)
 	{
 	  model += extended_model;
@@ -874,6 +885,11 @@ https://www.intel.com/content/www/us/en/support/articles/000059422/processors.ht
 
       ecx = cpu_features->features[CPUID_INDEX_1].cpuid.ecx;
 
+      /* Benchmarks indicate non-temporal memset can be profitable on AMD
+	hardware.  */
+      cpu_features->preferred[index_arch_Avoid_Non_Temporal_Memset]
+	  &= ~bit_arch_Avoid_Non_Temporal_Memset;
+
       if (CPU_FEATURE_USABLE_P (cpu_features, AVX))
 	{
 	  /* Since the FMA4 bit is in CPUID_INDEX_80000001 and
diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index de4584116f..d8288f0b0c 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -1048,14 +1048,6 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
   if (CPU_FEATURE_USABLE_P (cpu_features, FSRM))
     rep_movsb_threshold = 2112;
 
-  /* Non-temporal stores are more performant on Intel and AMD hardware above
-     non_temporal_threshold. Enable this for both Intel and AMD hardware. */
-  unsigned long int memset_non_temporal_threshold = SIZE_MAX;
-  if (!CPU_FEATURES_ARCH_P (cpu_features, Avoid_Non_Temporal_Memset)
-      && (cpu_features->basic.kind == arch_kind_intel
-	  || cpu_features->basic.kind == arch_kind_amd))
-    memset_non_temporal_threshold = non_temporal_threshold;
-
   /* For AMD CPUs that support ERMS (Zen3+), REP MOVSB is in a lot of
      cases slower than the vectorized path (and for some alignments,
      it is really slow, check BZ #30994).  */
@@ -1077,6 +1069,13 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
   if (tunable_size != 0)
     shared = tunable_size;
 
+  /* Non-temporal stores are more performant on some hardware above
+     non_temporal_threshold. Currently Prefer_Non_Temporal is set for for both
+     Intel and AMD hardware. */
+  unsigned long int memset_non_temporal_threshold = SIZE_MAX;
+  if (!CPU_FEATURES_ARCH_P (cpu_features, Avoid_Non_Temporal_Memset))
+    memset_non_temporal_threshold = non_temporal_threshold;
+
   tunable_size = TUNABLE_GET (x86_non_temporal_threshold, long int, NULL);
   if (tunable_size > minimum_non_temporal_threshold
       && tunable_size <= maximum_non_temporal_threshold)
-- 
2.17.1

