memcpy.c 1.7 KB

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  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. * Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
  15. *
  16. * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
  17. */
  18. /*
  19. * Modified for uClibc by Erik Andersen <andersen@codepoet.org>
  20. * These make no attempt to use nifty things like mmx/3dnow/etc.
  21. * These are not inline, and will therefore not be as fast as
  22. * modifying the headers to use inlines (and cannot therefore
  23. * do tricky things when dealing with const memory). But they
  24. * should (I hope!) be faster than their generic equivalents....
  25. *
  26. * More importantly, these should provide a good example for
  27. * others to follow when adding arch specific optimizations.
  28. * -Erik
  29. */
  30. #include <string.h>
  31. #undef memcpy
  32. void *memcpy(void * to, const void * from, size_t n)
  33. {
  34. int d0, d1, d2;
  35. __asm__ __volatile__(
  36. " rep; movsl\n"
  37. " movl %4, %%ecx\n"
  38. " andl $3, %%ecx\n"
  39. /* jz is optional. avoids "rep; movsb" with ecx == 0,
  40. * but adds a branch, which is currently (2008) faster */
  41. " jz 1f\n"
  42. " rep; movsb\n"
  43. "1:\n"
  44. : "=&c" (d0), "=&D" (d1), "=&S" (d2)
  45. : "0" (n / 4), "g" (n), "1" ((long)to), "2" ((long)from)
  46. : "memory"
  47. );
  48. return to;
  49. }
  50. libc_hidden_def(memcpy)