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* sysdeps/x86_64/strlen.S: Optimize by using SSE2 instructions.

This commit is contained in:
Ulrich Drepper 2009-04-05 18:49:28 +00:00
parent c0bac8b05a
commit a152f366dc
4 changed files with 3071 additions and 3966 deletions
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4
ChangeLog
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@ -1,3 +1,7 @@
2009-04-05 Ulrich Drepper <drepper@redhat.com>
* sysdeps/x86_64/strlen.S: Optimize by using SSE2 instructions.
2009-04-03 Ulrich Drepper <drepper@redhat.com>
* configure.in: We need to test for the compiler earlier.

5
NEWS
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@ -1,4 +1,4 @@
GNU C Library NEWS -- history of user-visible changes. 2009-4-3
GNU C Library NEWS -- history of user-visible changes. 2009-4-5
Copyright (C) 1992-2008, 2009 Free Software Foundation, Inc.
See the end for copying conditions.
@ -37,6 +37,9 @@ Version 2.10
* New locale: nan_TW@latin
* Faster strlen on x86-64.
Implemented by Ulrich Drepper.
Version 2.9

6886
configure vendored
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142
sysdeps/x86_64/strlen.S
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@ -1,6 +1,6 @@
/* strlen(str) -- determine the length of the string STR.
Copyright (C) 2002, 2003 Free Software Foundation, Inc.
Based on i486 version contributed by Ulrich Drepper <drepper@redhat.com>.
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
@ -19,121 +19,35 @@
02111-1307 USA. */
#include <sysdep.h>
#include "asm-syntax.h"
#include "bp-sym.h"
#include "bp-asm.h"
.text
ENTRY (strlen)
movq %rdi, %rcx /* Duplicate source pointer. */
andl $7, %ecx /* mask alignment bits */
movq %rdi, %rax /* duplicate destination. */
jz 1f /* aligned => start loop */
ENTRY(strlen)
movq %rdi, %rcx
movq %rdi, %r8
andq $~15, %rdi
pxor %xmm1, %xmm1
orl $0xffffffff, %esi
movdqa (%rdi), %xmm0
subq %rdi, %rcx
leaq 16(%rdi), %rdi
pcmpeqb %xmm1, %xmm0
shl %cl, %esi
pmovmskb %xmm0, %edx
xorl %eax, %eax
negq %r8
andl %esi, %edx
jnz 1f
neg %ecx /* We need to align to 8 bytes. */
addl $8,%ecx
/* Search the first bytes directly. */
0: cmpb $0x0,(%rax) /* is byte NUL? */
je 2f /* yes => return */
incq %rax /* increment pointer */
decl %ecx
jnz 0b
2: movdqa (%rdi), %xmm0
leaq 16(%rdi), %rdi
pcmpeqb %xmm1, %xmm0
pmovmskb %xmm0, %edx
testl %edx, %edx
jz 2b
1: movq $0xfefefefefefefeff,%r8 /* Save magic. */
.p2align 4 /* Align loop. */
4: /* Main Loop is unrolled 4 times. */
/* First unroll. */
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
addq $8,%rax /* adjust pointer for next word */
movq %r8, %rdx /* magic value */
addq %rcx, %rdx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rcx, %rdx /* (word+magic)^word */
orq %r8, %rdx /* set all non-carry bits */
incq %rdx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz 3f /* found NUL => return pointer */
/* Second unroll. */
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
addq $8,%rax /* adjust pointer for next word */
movq %r8, %rdx /* magic value */
addq %rcx, %rdx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rcx, %rdx /* (word+magic)^word */
orq %r8, %rdx /* set all non-carry bits */
incq %rdx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz 3f /* found NUL => return pointer */
/* Third unroll. */
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
addq $8,%rax /* adjust pointer for next word */
movq %r8, %rdx /* magic value */
addq %rcx, %rdx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rcx, %rdx /* (word+magic)^word */
orq %r8, %rdx /* set all non-carry bits */
incq %rdx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jnz 3f /* found NUL => return pointer */
/* Fourth unroll. */
movq (%rax), %rcx /* get double word (= 8 bytes) in question */
addq $8,%rax /* adjust pointer for next word */
movq %r8, %rdx /* magic value */
addq %rcx, %rdx /* add the magic value to the word. We get
carry bits reported for each byte which
is *not* 0 */
jnc 3f /* highest byte is NUL => return pointer */
xorq %rcx, %rdx /* (word+magic)^word */
orq %r8, %rdx /* set all non-carry bits */
incq %rdx /* add 1: if one carry bit was *not* set
the addition will not result in 0. */
jz 4b /* no NUL found => continue loop */
.p2align 4 /* Align, it's a jump target. */
3: subq $8,%rax /* correct pointer increment. */
testb %cl, %cl /* is first byte NUL? */
jz 2f /* yes => return */
incq %rax /* increment pointer */
testb %ch, %ch /* is second byte NUL? */
jz 2f /* yes => return */
incq %rax /* increment pointer */
testl $0x00ff0000, %ecx /* is third byte NUL? */
jz 2f /* yes => return pointer */
incq %rax /* increment pointer */
testl $0xff000000, %ecx /* is fourth byte NUL? */
jz 2f /* yes => return pointer */
incq %rax /* increment pointer */
shrq $32, %rcx /* look at other half. */
testb %cl, %cl /* is first byte NUL? */
jz 2f /* yes => return */
incq %rax /* increment pointer */
testb %ch, %ch /* is second byte NUL? */
jz 2f /* yes => return */
incq %rax /* increment pointer */
testl $0xff0000, %ecx /* is third byte NUL? */
jz 2f /* yes => return pointer */
incq %rax /* increment pointer */
2:
subq %rdi, %rax /* compute difference to string start */
1: leaq -16(%rdi,%r8), %rdi
bsfl %edx, %eax
addq %rdi, %rax
ret
END (strlen)
END(strlen)
libc_hidden_builtin_def (strlen)