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authorLing Ma <ling.ml@alibaba-inc.com>2014-06-19 13:00:56 -0700
committerH.J. Lu <hjl.tools@gmail.com>2014-06-19 15:14:08 -0700
commit5c74e47cd628a6fcd2e4eba021301e275f8a95a3 (patch)
treeb85959ae1a65bc526d683807213027115886d96d /sysdeps/x86_64/multiarch/memset.S
parent4d43ef1e7434d7d419afbcd754931cb0c794763c (diff)
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Add x86_64 memset optimized for AVX2
In this patch we take advantage of HSW memory bandwidth, manage to
reduce miss branch prediction by avoiding using branch instructions and
force destination to be aligned with avx & avx2 instruction.

The CPU2006 403.gcc benchmark indicates this patch improves performance
from 26% to 59%.

	* sysdeps/x86_64/multiarch/Makefile: Add memset-avx2.
	* sysdeps/x86_64/multiarch/memset-avx2.S: New file.
	* sysdeps/x86_64/multiarch/memset.S: Likewise.
	* sysdeps/x86_64/multiarch/memset_chk.S: Likewise.
	* sysdeps/x86_64/multiarch/rtld-memset.S: Likewise.
Diffstat (limited to 'sysdeps/x86_64/multiarch/memset.S')
-rw-r--r--sysdeps/x86_64/multiarch/memset.S59
1 files changed, 59 insertions, 0 deletions
diff --git a/sysdeps/x86_64/multiarch/memset.S b/sysdeps/x86_64/multiarch/memset.S
new file mode 100644
index 0000000000..3113d1cbc0
--- /dev/null
+++ b/sysdeps/x86_64/multiarch/memset.S
@@ -0,0 +1,59 @@
+/* Multiple versions of memset
+   All versions must be listed in ifunc-impl-list.c.
+   Copyright (C) 2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <shlib-compat.h>
+#include <init-arch.h>
+
+/* Define multiple versions only for the definition in lib.  */
+#ifndef NOT_IN_libc
+ENTRY(memset)
+	.type	memset, @gnu_indirect_function
+	cmpl	$0, __cpu_features+KIND_OFFSET(%rip)
+	jne	1f
+	call	__init_cpu_features
+1:	leaq	__memset_sse2(%rip), %rax
+	testl	$bit_AVX2_Usable, __cpu_features+FEATURE_OFFSET+index_AVX2_Usable(%rip)
+	jz	2f
+	leaq	__memset_avx2(%rip), %rax
+2:	ret
+END(memset)
+#endif
+
+#if !defined NOT_IN_libc
+# undef memset
+# define memset __memset_sse2
+
+# undef __memset_chk
+# define __memset_chk __memset_chk_sse2
+
+# ifdef SHARED
+#  undef libc_hidden_builtin_def
+/* It doesn't make sense to send libc-internal memset calls through a PLT.
+   The speedup we get from using GPR instruction is likely eaten away
+   by the indirect call in the PLT.  */
+#  define libc_hidden_builtin_def(name) \
+	.globl __GI_memset; __GI_memset = __memset_sse2
+# endif
+
+# undef strong_alias
+# define strong_alias(original, alias)
+#endif
+
+#include "../memset.S"