Optimize x86-64 strlen for SSE4.2.

The SSE4.2 implementation is used in the DSO only.  The patch also adds
some infrastructure to be used in similar code later one.

1 files changed, 87 insertions, 0 deletions

diff --git a/sysdeps/x86_64/multiarch/strlen.S b/sysdeps/x86_64/multiarch/strlen.S
new file mode 100644
index 0000000000..bf889c1ab6
--- /dev/null
+++ b/sysdeps/x86_64/multiarch/strlen.S
@@ -0,0 +1,87 @@
+/* strlen(str) -- determine the length of the string STR.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+   Contributed by Ulrich Drepper <drepper@redhat.com>.
+   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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <sysdep.h>
+#include <ifunc-defines.h>
+
+
+/* Define multiple versions only for the definition in libc and for
+   the DSO.  In static binaries we need strlen before the initialization
+   happened.  */
+#if defined SHARED && !defined NOT_IN_libc
+	.text
+ENTRY(strlen)
+	.type	strlen, @gnu_indirect_function
+	cmpl	$0, __cpu_features+KIND_OFFSET(%rip)
+	jne	1f
+	call	__init_cpu_features
+1:	leaq	__strlen_sse2(%rip), %rax
+	testl	$(1<<20), __cpu_features+CPUID_OFFSET+COMMON_CPUID_INDEX_1*CPUID_SIZE+CPUID_ECX_OFFSET(%rip)
+	jz	2f
+	leaq	__strlen_sse42(%rip), %rax
+2:	ret
+END(strlen)
+
+
+	.type	__strlen_sse42, @function
+__strlen_sse42:
+	pxor	%xmm2, %xmm2
+	movq	%rdi, %rcx
+	movq	%rdi, %r8
+	andq	$~15, %rdi
+	movdqa	%xmm2, %xmm1
+	pcmpeqb	(%rdi), %xmm2
+	orl	$0xffffffff, %esi
+	subq	%rdi, %rcx
+	shll	%cl, %esi
+	pmovmskb %xmm2, %edx
+	andl	%esi, %edx
+	jnz	1f
+
+2:	pcmpistri $0x08, 16(%rdi), %xmm1
+	leaq	16(%rdi), %rdi
+	jnz	2b
+
+	leaq	(%rdi,%rcx), %rax
+	subq	%r8, %rax
+	ret
+
+1:	bsfl	%edx, %eax
+	leaq	(%rdi,%rax), %rax
+	subq	%r8, %rax
+	ret
+	.size	__strlen_sse42, .-__strlen_sse42
+
+
+# undef ENTRY
+# define ENTRY(name) \
+	.type __strlen_sse2, @function; __strlen_sse2:
+# undef END
+# define END(name) \
+	.size __strlen_sse2, .-__strlen_sse2
+# undef libc_hidden_builtin_def
+/* It doesn't make sense to send libc-internal strlen calls through a PLT.
+   The speedup we get from using SSE4.2 instruction is likely eaten away
+   by the indirect call in the PLT.  */
+# define libc_hidden_builtin_def(name) \
+	.globl __GI_strlen; __GI_strlen = __strlen_sse2
+#endif
+
+#include "../strlen.S"