140 lines
4.9 KiB
ArmAsm
140 lines
4.9 KiB
ArmAsm
/* 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>.
|
|
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 "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 */
|
|
ret
|
|
END (strlen)
|
|
libc_hidden_builtin_def (strlen)
|