/* stpcpy -- copy SRC to DEST returning the address of the terminating '\0' in DEST. For Intel 80x86, x>=3. Copyright (C) 1994, 1995, 1996 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 END (__stpcpy) weak_alias (__stpcpy, stpcpy)