diff options
Diffstat (limited to 'sysdeps/x86_64/strlen.S')
| -rw-r--r-- | sysdeps/x86_64/strlen.S | 146 |
1 files changed, 30 insertions, 116 deletions
diff --git a/sysdeps/x86_64/strlen.S b/sysdeps/x86_64/strlen.S index fd950edaaa..b83332c90c 100644 --- a/sysdeps/x86_64/strlen.S +++ b/sysdeps/x86_64/strlen.S @@ -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 */ - - 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 - -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 */ +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 + +2: movdqa (%rdi), %xmm0 + leaq 16(%rdi), %rdi + pcmpeqb %xmm1, %xmm0 + pmovmskb %xmm0, %edx + testl %edx, %edx + jz 2b + +1: leaq -16(%rdi,%r8), %rdi + bsfl %edx, %eax + addq %rdi, %rax ret -END (strlen) +END(strlen) libc_hidden_builtin_def (strlen) |