| /* Copy SRC to DEST returning the address of the terminating '\0' in DEST. |
| For Intel 80x86, x>=3. |
| Copyright (C) 1994-2016 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| Contributed by Ulrich Drepper (drepper@gnu.ai.mit.edu). |
| |
| 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 |
| <http://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) |