sysdeps/i386/i686/strcmp.S

   1 /* Highly optimized version for ix86, x>=6.
   2    Copyright (C) 1999-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1999.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <sysdep.h>
  21 #include "asm-syntax.h"
  22
  23 #define PARMS   4               /* no space for saved regs */
  24 #define STR1    PARMS
  25 #define STR2    STR1+4
  26
  27         .text
  28 ENTRY (strcmp)
  29
  30         movl    STR1(%esp), %ecx
  31         movl    STR2(%esp), %edx
  32
  33 L(oop): movb    (%ecx), %al
  34         cmpb    (%edx), %al
  35         jne     L(neq)
  36         incl    %ecx
  37         incl    %edx
  38         testb   %al, %al
  39         jnz     L(oop)
  40
  41         xorl    %eax, %eax
  42         /* when strings are equal, pointers rest one beyond
  43            the end of the NUL terminators.  */
  44         ret
  45
  46 L(neq): movl    $1, %eax
  47         movl    $-1, %ecx
  48         cmovbl  %ecx, %eax
  49
  50         ret
  51 END (strcmp)
  52 libc_hidden_builtin_def (strcmp)