libc/string/i386/strchr.c

   1 /*
   2  * This string-include defines all string functions as inline
   3  * functions. Use gcc. It also assumes ds=es=data space, this should be
   4  * normal. Most of the string-functions are rather heavily hand-optimized,
   5  * see especially strtok,strstr,str[c]spn. They should work, but are not
   6  * very easy to understand. Everything is done entirely within the register
   7  * set, making the functions fast and clean. String instructions have been
   8  * used through-out, making for "slightly" unclear code :-)
   9  *
  10  *              NO Copyright (C) 1991, 1992 Linus Torvalds,
  11  *              consider these trivial functions to be PD.
  12  */
  13
  14 /*
  15  * Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
  16  *
  17  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
  18  */
  19
  20 /*
  21  * Modified for uClibc by Erik Andersen <andersen@codepoet.org>
  22  * These make no attempt to use nifty things like mmx/3dnow/etc.
  23  * These are not inline, and will therefore not be as fast as
  24  * modifying the headers to use inlines (and cannot therefore
  25  * do tricky things when dealing with const memory).  But they
  26  * should (I hope!) be faster than their generic equivalents....
  27  *
  28  * More importantly, these should provide a good example for
  29  * others to follow when adding arch specific optimizations.
  30  *  -Erik
  31  */
  32
  33 #include <string.h>
  34
  35 #undef strchr
  36 char *strchr(const char *s, int c)
  37 {
  38         int esi;
  39         register char * eax;
  40         __asm__ __volatile__(
  41                 "       movb    %%al, %%ah\n"
  42                 "1:     lodsb\n"
  43                 "       cmpb    %%ah, %%al\n"
  44                 "       je      2f\n"
  45                 "       testb   %%al, %%al\n"
  46                 "       jnz     1b\n"
  47                 "       movl    $1, %%esi\n" /* can use shorter xor + inc */
  48                 "2:     leal    -1(%%esi), %%eax\n"
  49                 : "=a" (eax), "=&S" (esi)
  50                 : "0" (c), "1" (s)
  51                 /* no clobbers */
  52         );
  53         return eax;
  54 }
  55 libc_hidden_def(strchr)
  56 #ifdef __UCLIBC_SUSV3_LEGACY__
  57 strong_alias(strchr,index)
  58 #endif