mirror of
git://sourceware.org/git/glibc.git
synced 2024-12-15 04:20:28 +08:00
264 lines
9.5 KiB
ArmAsm
264 lines
9.5 KiB
ArmAsm
/* strcat(dest, src) -- Append SRC on the end of DEST.
|
|
For Intel 80x86, x>=4.
|
|
Copyright (C) 1994-2024 Free Software Foundation, Inc.
|
|
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, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <sysdep.h>
|
|
#include "asm-syntax.h"
|
|
|
|
#define PARMS 4+4 /* space for 1 saved reg */
|
|
#define RTN PARMS
|
|
#define DEST RTN
|
|
#define SRC DEST+4
|
|
|
|
.text
|
|
ENTRY (strcat)
|
|
|
|
pushl %edi /* Save callee-safe register. */
|
|
cfi_adjust_cfa_offset (4)
|
|
|
|
movl DEST(%esp), %edx
|
|
movl SRC(%esp), %ecx
|
|
|
|
testb $0xff, (%ecx) /* Is source string empty? */
|
|
jz L(8) /* yes => return */
|
|
|
|
/* Test the first bytes separately until destination is aligned. */
|
|
testl $3, %edx /* destination pointer aligned? */
|
|
jz L(1) /* yes => begin scan loop */
|
|
testb $0xff, (%edx) /* is end of string? */
|
|
jz L(2) /* yes => start appending */
|
|
incl %edx /* increment source pointer */
|
|
|
|
testl $3, %edx /* destination pointer aligned? */
|
|
jz L(1) /* yes => begin scan loop */
|
|
testb $0xff, (%edx) /* is end of string? */
|
|
jz L(2) /* yes => start appending */
|
|
incl %edx /* increment source pointer */
|
|
|
|
testl $3, %edx /* destination pointer aligned? */
|
|
jz L(1) /* yes => begin scan loop */
|
|
testb $0xff, (%edx) /* is end of string? */
|
|
jz L(2) /* yes => start appending */
|
|
incl %edx /* increment source pointer */
|
|
|
|
/* Now we are aligned. Begin scan loop. */
|
|
jmp L(1)
|
|
|
|
cfi_rel_offset (edi, 0)
|
|
ALIGN(4)
|
|
|
|
L(4): addl $16,%edx /* increment destination pointer for round */
|
|
|
|
L(1): movl (%edx), %eax /* get word (= 4 bytes) in question */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
|
|
/* If you compare this with the algorithm in memchr.S you will
|
|
notice that here is an `xorl' statement missing. But you must
|
|
not forget that we are looking for C == 0 and `xorl $0, %eax'
|
|
is a no-op. */
|
|
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
|
|
/* According to the algorithm we had to reverse the effect of the
|
|
XOR first and then test the overflow bits. But because the
|
|
following XOR would destroy the carry flag and it would (in a
|
|
representation with more than 32 bits) not alter then last
|
|
overflow, we can now test this condition. If no carry is signaled
|
|
no overflow must have occurred in the last byte => it was 0. */
|
|
jnc L(3)
|
|
|
|
/* We are only interested in carry bits that change due to the
|
|
previous add, so remove original bits */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
|
|
/* Now test for the other three overflow bits. */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
|
|
/* If at least one byte of the word is C we don't get 0 in %ecx. */
|
|
jnz L(3)
|
|
|
|
movl 4(%edx), %eax /* get word from source */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc L(5) /* highest byte is C => stop copying */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz L(5) /* one byte is NUL => stop copying */
|
|
|
|
movl 8(%edx), %eax /* get word from source */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc L(6) /* highest byte is C => stop copying */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz L(6) /* one byte is NUL => stop copying */
|
|
|
|
movl 12(%edx), %eax /* get word from source */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc L(7) /* highest byte is C => stop copying */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jz L(4) /* no byte is NUL => carry on copying */
|
|
|
|
L(7): addl $4, %edx /* adjust source pointer */
|
|
L(6): addl $4, %edx
|
|
L(5): addl $4, %edx
|
|
|
|
L(3): testb %al, %al /* is first byte NUL? */
|
|
jz L(2) /* yes => start copying */
|
|
incl %edx /* increment source pointer */
|
|
|
|
testb %ah, %ah /* is second byte NUL? */
|
|
jz L(2) /* yes => start copying */
|
|
incl %edx /* increment source pointer */
|
|
|
|
testl $0xff0000, %eax /* is third byte NUL? */
|
|
jz L(2) /* yes => start copying */
|
|
incl %edx /* increment source pointer */
|
|
|
|
L(2): subl %ecx, %edx /* reduce number of loop variants */
|
|
|
|
/* Now we have to align the source pointer. */
|
|
testl $3, %ecx /* pointer correctly aligned? */
|
|
jz L(29) /* yes => start copy loop */
|
|
movb (%ecx), %al /* get first byte */
|
|
movb %al, (%ecx,%edx) /* and store it */
|
|
andb %al, %al /* is byte NUL? */
|
|
jz L(8) /* yes => return */
|
|
incl %ecx /* increment pointer */
|
|
|
|
testl $3, %ecx /* pointer correctly aligned? */
|
|
jz L(29) /* yes => start copy loop */
|
|
movb (%ecx), %al /* get first byte */
|
|
movb %al, (%ecx,%edx) /* and store it */
|
|
andb %al, %al /* is byte NUL? */
|
|
jz L(8) /* yes => return */
|
|
incl %ecx /* increment pointer */
|
|
|
|
testl $3, %ecx /* pointer correctly aligned? */
|
|
jz L(29) /* yes => start copy loop */
|
|
movb (%ecx), %al /* get first byte */
|
|
movb %al, (%ecx,%edx) /* and store it */
|
|
andb %al, %al /* is byte NUL? */
|
|
jz L(8) /* yes => return */
|
|
incl %ecx /* increment pointer */
|
|
|
|
/* Now we are aligned. */
|
|
jmp L(29) /* start copy loop */
|
|
|
|
ALIGN(4)
|
|
|
|
L(28): movl %eax, 12(%ecx,%edx)/* store word at destination */
|
|
addl $16, %ecx /* adjust pointer for full round */
|
|
|
|
L(29): movl (%ecx), %eax /* get word from source */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc L(9) /* highest byte is C => stop copying */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz L(9) /* one byte is NUL => stop copying */
|
|
movl %eax, (%ecx,%edx) /* store word to destination */
|
|
|
|
movl 4(%ecx), %eax /* get word from source */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc L(91) /* highest byte is C => stop copying */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz L(91) /* one byte is NUL => stop copying */
|
|
movl %eax, 4(%ecx,%edx) /* store word to destination */
|
|
|
|
movl 8(%ecx), %eax /* get word from source */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc L(92) /* highest byte is C => stop copying */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jnz L(92) /* one byte is NUL => stop copying */
|
|
movl %eax, 8(%ecx,%edx) /* store word to destination */
|
|
|
|
movl 12(%ecx), %eax /* get word from source */
|
|
movl $0xfefefeff, %edi /* magic value */
|
|
addl %eax, %edi /* add the magic value to the word. We get
|
|
carry bits reported for each byte which
|
|
is *not* 0 */
|
|
jnc L(93) /* highest byte is C => stop copying */
|
|
xorl %eax, %edi /* ((word^charmask)+magic)^(word^charmask) */
|
|
orl $0xfefefeff, %edi /* set all non-carry bits */
|
|
incl %edi /* add 1: if one carry bit was *not* set
|
|
the addition will not result in 0. */
|
|
jz L(28) /* no is NUL => carry on copying */
|
|
|
|
L(93): addl $4, %ecx /* adjust pointer */
|
|
L(92): addl $4, %ecx
|
|
L(91): addl $4, %ecx
|
|
|
|
L(9): movb %al, (%ecx,%edx) /* store first byte of last word */
|
|
orb %al, %al /* is it NUL? */
|
|
jz L(8) /* yes => return */
|
|
|
|
movb %ah, 1(%ecx,%edx) /* store second byte of last word */
|
|
orb %ah, %ah /* is it NUL? */
|
|
jz L(8) /* yes => return */
|
|
|
|
shrl $16, %eax /* make upper bytes accessible */
|
|
movb %al, 2(%ecx,%edx) /* store third byte of last word */
|
|
orb %al, %al /* is it NUL? */
|
|
jz L(8) /* yes => return */
|
|
|
|
movb %ah, 3(%ecx,%edx) /* store fourth byte of last word */
|
|
|
|
L(8): movl DEST(%esp), %eax /* start address of destination is result */
|
|
popl %edi /* restore saved register */
|
|
cfi_adjust_cfa_offset (-4)
|
|
cfi_restore (edi)
|
|
|
|
ret
|
|
END (strcat)
|
|
libc_hidden_builtin_def (strcat)
|