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More small optimizations for x86-64 strlen.

This commit is contained in:
Ulrich Drepper 2009-06-04 16:45:35 -07:00
parent 747785f2b3
commit 2f3f7b9da2
2 changed files with 8 additions and 10 deletions
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2
ChangeLog
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@ -1,6 +1,6 @@
2009-06-04 Ulrich Drepper <drepper@redhat.com>
* sysdeps/x86_64/strlen.S: Remove useless instruction.
* sysdeps/x86_64/strlen.S: Minor optimizations.
2009-06-02 H.J. Lu <hongjiu.lu@intel.com>

16
sysdeps/x86_64/strlen.S
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@ -23,29 +23,27 @@
.text
ENTRY(strlen)
pxor %xmm2, %xmm2
movq %rdi, %rcx
movq %rdi, %r8
andq $~15, %rdi
pxor %xmm1, %xmm1
movdqa %xmm2, %xmm1
pcmpeqb (%rdi), %xmm2
orl $0xffffffff, %esi
movdqa (%rdi), %xmm0
subq %rdi, %rcx
leaq 16(%rdi), %rdi
pcmpeqb %xmm1, %xmm0
shl %cl, %esi
pmovmskb %xmm0, %edx
negq %r8
shll %cl, %esi
pmovmskb %xmm2, %edx
andl %esi, %edx
jnz 1f
2: movdqa (%rdi), %xmm0
2: movdqa 16(%rdi), %xmm0
leaq 16(%rdi), %rdi
pcmpeqb %xmm1, %xmm0
pmovmskb %xmm0, %edx
testl %edx, %edx
jz 2b
1: leaq -16(%rdi,%r8), %rdi
1: subq %r8, %rdi
bsfl %edx, %eax
addq %rdi, %rax
ret