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* sysdeps/x86_64/strlen.S: Optimize by using SSE2 instructions.
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@ -1,3 +1,7 @@
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2009-04-05 Ulrich Drepper <drepper@redhat.com>
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* sysdeps/x86_64/strlen.S: Optimize by using SSE2 instructions.
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2009-04-03 Ulrich Drepper <drepper@redhat.com>
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* configure.in: We need to test for the compiler earlier.
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5
NEWS
5
NEWS
@ -1,4 +1,4 @@
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GNU C Library NEWS -- history of user-visible changes. 2009-4-3
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GNU C Library NEWS -- history of user-visible changes. 2009-4-5
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Copyright (C) 1992-2008, 2009 Free Software Foundation, Inc.
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See the end for copying conditions.
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@ -37,6 +37,9 @@ Version 2.10
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* New locale: nan_TW@latin
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* Faster strlen on x86-64.
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Implemented by Ulrich Drepper.
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Version 2.9
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@ -1,6 +1,6 @@
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/* strlen(str) -- determine the length of the string STR.
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Copyright (C) 2002, 2003 Free Software Foundation, Inc.
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Based on i486 version contributed by Ulrich Drepper <drepper@redhat.com>.
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Copyright (C) 2009 Free Software Foundation, Inc.
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Contributed by Ulrich Drepper <drepper@redhat.com>.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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@ -19,121 +19,35 @@
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02111-1307 USA. */
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#include <sysdep.h>
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#include "asm-syntax.h"
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#include "bp-sym.h"
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#include "bp-asm.h"
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.text
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ENTRY (strlen)
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movq %rdi, %rcx /* Duplicate source pointer. */
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andl $7, %ecx /* mask alignment bits */
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movq %rdi, %rax /* duplicate destination. */
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jz 1f /* aligned => start loop */
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ENTRY(strlen)
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movq %rdi, %rcx
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movq %rdi, %r8
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andq $~15, %rdi
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pxor %xmm1, %xmm1
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orl $0xffffffff, %esi
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movdqa (%rdi), %xmm0
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subq %rdi, %rcx
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leaq 16(%rdi), %rdi
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pcmpeqb %xmm1, %xmm0
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shl %cl, %esi
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pmovmskb %xmm0, %edx
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xorl %eax, %eax
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negq %r8
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andl %esi, %edx
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jnz 1f
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neg %ecx /* We need to align to 8 bytes. */
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addl $8,%ecx
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/* Search the first bytes directly. */
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0: cmpb $0x0,(%rax) /* is byte NUL? */
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je 2f /* yes => return */
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incq %rax /* increment pointer */
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decl %ecx
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jnz 0b
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2: movdqa (%rdi), %xmm0
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leaq 16(%rdi), %rdi
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pcmpeqb %xmm1, %xmm0
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pmovmskb %xmm0, %edx
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testl %edx, %edx
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jz 2b
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1: movq $0xfefefefefefefeff,%r8 /* Save magic. */
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.p2align 4 /* Align loop. */
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4: /* Main Loop is unrolled 4 times. */
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/* First unroll. */
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movq (%rax), %rcx /* get double word (= 8 bytes) in question */
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addq $8,%rax /* adjust pointer for next word */
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movq %r8, %rdx /* magic value */
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addq %rcx, %rdx /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc 3f /* highest byte is NUL => return pointer */
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xorq %rcx, %rdx /* (word+magic)^word */
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orq %r8, %rdx /* set all non-carry bits */
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incq %rdx /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jnz 3f /* found NUL => return pointer */
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/* Second unroll. */
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movq (%rax), %rcx /* get double word (= 8 bytes) in question */
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addq $8,%rax /* adjust pointer for next word */
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movq %r8, %rdx /* magic value */
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addq %rcx, %rdx /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc 3f /* highest byte is NUL => return pointer */
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xorq %rcx, %rdx /* (word+magic)^word */
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orq %r8, %rdx /* set all non-carry bits */
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incq %rdx /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jnz 3f /* found NUL => return pointer */
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/* Third unroll. */
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movq (%rax), %rcx /* get double word (= 8 bytes) in question */
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addq $8,%rax /* adjust pointer for next word */
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movq %r8, %rdx /* magic value */
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addq %rcx, %rdx /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc 3f /* highest byte is NUL => return pointer */
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xorq %rcx, %rdx /* (word+magic)^word */
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orq %r8, %rdx /* set all non-carry bits */
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incq %rdx /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jnz 3f /* found NUL => return pointer */
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/* Fourth unroll. */
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movq (%rax), %rcx /* get double word (= 8 bytes) in question */
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addq $8,%rax /* adjust pointer for next word */
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movq %r8, %rdx /* magic value */
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addq %rcx, %rdx /* add the magic value to the word. We get
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carry bits reported for each byte which
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is *not* 0 */
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jnc 3f /* highest byte is NUL => return pointer */
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xorq %rcx, %rdx /* (word+magic)^word */
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orq %r8, %rdx /* set all non-carry bits */
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incq %rdx /* add 1: if one carry bit was *not* set
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the addition will not result in 0. */
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jz 4b /* no NUL found => continue loop */
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.p2align 4 /* Align, it's a jump target. */
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3: subq $8,%rax /* correct pointer increment. */
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testb %cl, %cl /* is first byte NUL? */
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jz 2f /* yes => return */
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incq %rax /* increment pointer */
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testb %ch, %ch /* is second byte NUL? */
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jz 2f /* yes => return */
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incq %rax /* increment pointer */
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testl $0x00ff0000, %ecx /* is third byte NUL? */
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jz 2f /* yes => return pointer */
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incq %rax /* increment pointer */
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testl $0xff000000, %ecx /* is fourth byte NUL? */
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jz 2f /* yes => return pointer */
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incq %rax /* increment pointer */
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shrq $32, %rcx /* look at other half. */
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testb %cl, %cl /* is first byte NUL? */
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jz 2f /* yes => return */
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incq %rax /* increment pointer */
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testb %ch, %ch /* is second byte NUL? */
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jz 2f /* yes => return */
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incq %rax /* increment pointer */
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testl $0xff0000, %ecx /* is third byte NUL? */
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jz 2f /* yes => return pointer */
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incq %rax /* increment pointer */
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2:
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subq %rdi, %rax /* compute difference to string start */
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1: leaq -16(%rdi,%r8), %rdi
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bsfl %edx, %eax
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addq %rdi, %rax
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ret
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END (strlen)
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END(strlen)
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libc_hidden_builtin_def (strlen)
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