mirror of git://sourceware.org/git/glibc.git
88 lines
2.6 KiB
ArmAsm
88 lines
2.6 KiB
ArmAsm
/* Copy SRC to DEST returning the address of the terminating '\0' in DEST.
|
|
For Intel 80x86, x>=3.
|
|
Copyright (C) 1994-2022 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/>. */
|
|
|
|
/* This function is defined neither in ANSI nor POSIX standards but is
|
|
also not invented here. */
|
|
|
|
#include <sysdep.h>
|
|
#include "asm-syntax.h"
|
|
|
|
#define PARMS 4 /* no space for saved regs */
|
|
#define RTN PARMS
|
|
#define DEST RTN
|
|
#define SRC DEST+4
|
|
|
|
.text
|
|
ENTRY (__stpcpy)
|
|
|
|
movl DEST(%esp), %eax
|
|
movl SRC(%esp), %ecx
|
|
subl %eax, %ecx /* magic: reduce number of loop variants
|
|
to one using addressing mode */
|
|
|
|
/* Here we would like to write
|
|
|
|
subl $4, %eax
|
|
ALIGN (4)
|
|
|
|
but the assembler is too smart and optimizes for the shortest
|
|
form where the number only needs one byte. But if we could
|
|
have the long form we would not need the alignment. */
|
|
|
|
.byte 0x81, 0xe8 /* This is `subl $0x00000004, %eax' */
|
|
.long 0x00000004
|
|
|
|
/* Four times unfolded loop with only one loop counter. This
|
|
is achieved by the use of index+base addressing mode. As the
|
|
loop counter we use the destination address because this is
|
|
also the result. */
|
|
L(1): addl $4, %eax /* increment loop counter */
|
|
|
|
movb (%eax,%ecx), %dl /* load current char */
|
|
movb %dl, (%eax) /* and store it */
|
|
testb %dl, %dl /* was it NUL? */
|
|
jz L(2) /* yes, then exit */
|
|
|
|
movb 1(%eax,%ecx), %dl /* load current char */
|
|
movb %dl, 1(%eax) /* and store it */
|
|
testb %dl, %dl /* was it NUL? */
|
|
jz L(3) /* yes, then exit */
|
|
|
|
movb 2(%eax,%ecx), %dl /* load current char */
|
|
movb %dl, 2(%eax) /* and store it */
|
|
testb %dl, %dl /* was it NUL? */
|
|
jz L(4) /* yes, then exit */
|
|
|
|
movb 3(%eax,%ecx), %dl /* load current char */
|
|
movb %dl, 3(%eax) /* and store it */
|
|
testb %dl, %dl /* was it NUL? */
|
|
jnz L(1) /* no, then continue loop */
|
|
|
|
incl %eax /* correct loop counter */
|
|
L(4): incl %eax
|
|
L(3): incl %eax
|
|
L(2):
|
|
|
|
ret
|
|
END (__stpcpy)
|
|
|
|
weak_alias (__stpcpy, stpcpy)
|
|
libc_hidden_def (__stpcpy)
|
|
libc_hidden_builtin_def (stpcpy)
|