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From 27d3ce1467990f89126e228559dec8f84b96c60e Mon Sep 17 00:00:00 2001
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From: "H.J. Lu" <hjl.tools@gmail.com>
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Date: Fri, 1 Apr 2016 15:08:48 -0700
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Subject: [PATCH] Remove Fast_Copy_Backward from Intel Core processors
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Intel Core i3, i5 and i7 processors have fast unaligned copy and
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copy backward is ignored. Remove Fast_Copy_Backward from Intel Core
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processors to avoid confusion.
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* sysdeps/x86/cpu-features.c (init_cpu_features): Don't set
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bit_arch_Fast_Copy_Backward for Intel Core proessors.
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---
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ChangeLog | 5 +++++
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sysdeps/x86/cpu-features.c | 6 +-----
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2 files changed, 6 insertions(+), 5 deletions(-)
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diff -rup a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
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--- a/sysdeps/x86/cpu-features.c 2020-01-21 16:44:28.637555853 -0500
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+++ b/sysdeps/x86/cpu-features.c 2020-01-21 16:46:51.208756416 -0500
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@@ -116,11 +116,8 @@ init_cpu_features (struct cpu_features *
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case 0x2c:
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case 0x2e:
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case 0x2f:
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- /* Rep string instructions, copy backward, unaligned loads
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+ /* Rep string instructions, unaligned load, unaligned copy,
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and pminub are fast on Intel Core i3, i5 and i7. */
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-#if index_Fast_Rep_String != index_Fast_Copy_Backward
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-# error index_Fast_Rep_String != index_Fast_Copy_Backward
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-#endif
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#if index_Fast_Rep_String != index_Fast_Unaligned_Load
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# error index_Fast_Rep_String != index_Fast_Unaligned_Load
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#endif
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@@ -129,7 +126,6 @@ init_cpu_features (struct cpu_features *
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#endif
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cpu_features->feature[index_Fast_Rep_String]
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|= (bit_Fast_Rep_String
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- | bit_Fast_Copy_Backward
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| bit_Fast_Unaligned_Load
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| bit_Prefer_PMINUB_for_stringop);
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break;
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