libc/string/i386/memmove.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 memmove
  36 /*#define memmove TESTING*/
  37 void *memmove(void *dest, const void *src, size_t n)
  38 {
  39         int eax, ecx, esi, edi;
  40         __asm__ __volatile__(
  41                 "       movl    %%eax, %%edi\n"
  42                 "       cmpl    %%esi, %%eax\n"
  43                 "       je      2f\n" /* (optional) src == dest -> NOP */
  44                 "       jb      1f\n" /* src > dest -> simple copy */
  45                 "       leal    -1(%%esi,%%ecx), %%esi\n"
  46                 "       leal    -1(%%eax,%%ecx), %%edi\n"
  47                 "       std\n"
  48                 "1:     rep; movsb\n"
  49                 "       cld\n"
  50                 "2:\n"
  51                 : "=&c" (ecx), "=&S" (esi), "=&a" (eax), "=&D" (edi)
  52                 : "0" (n), "1" (src), "2" (dest)
  53                 : "memory"
  54         );
  55         return (void*)eax;
  56 }
  57 #ifndef memmove
  58 libc_hidden_def(memmove)
  59 #else
  60 /* Uncomment TESTING, gcc -D_GNU_SOURCE -m32 -Os memmove.c -o memmove
  61  * and run ./memmove
  62  */
  63 int main()
  64 {
  65         static char str[] = "abcdef.123";
  66         memmove(str + 1, str, 5);
  67         printf(strcmp(str, "aabcde.123") == 0 ? "ok\n" : "BAD!\n");
  68         memmove(str, str + 1, 5);
  69         printf(strcmp(str, "abcdee.123") == 0 ? "ok\n" : "BAD!\n");
  70 }
  71 #endif