diff options
Diffstat (limited to 'sysdeps/i386/stpcpy.S')
-rw-r--r-- | sysdeps/i386/stpcpy.S | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/sysdeps/i386/stpcpy.S b/sysdeps/i386/stpcpy.S new file mode 100644 index 0000000..f38a908 --- /dev/null +++ b/sysdeps/i386/stpcpy.S @@ -0,0 +1,87 @@ +/* stpcpy -- copy SRC to DEST returning the address of the terminating '\0' + in DEST. +For Intel 80x86, x>=3. +Copyright (C) 1994, 1995 Free Software Foundation, Inc. +Contributed by Ulrich Drepper (drepper@gnu.ai.mit.edu). +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 Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, +Boston, MA 02111-1307, USA. */ + +/* This function is defined neither in ANSI nor POSIX standards but is + also not invented here. */ + +#include <sysdep.h> +#include "asm-syntax.h" + +/* + INPUT PARAMETERS: + dest (sp + 4) + src (sp + 8) +*/ + + .text +ENTRY (__stpcpy) + movl 4(%esp), %eax /* load destination pointer */ + movl 8(%esp), %ecx /* load source pointer */ + + 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 adressing mode. As the + loop counter we use the destination address because this is + also the result. */ +L1: 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 L2 /* 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 L3 /* 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 L4 /* 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 L1 /* no, then continue loop */ + + incl %eax /* correct loop counter */ +L4: incl %eax +L3: incl %eax +L2: + ret + +weak_alias (__stpcpy, stpcpy) |