memdisk/memcpy.c

   1 /*
   2  * memcpy.c
   3  */
   4
   5 #include <string.h>
   6 #include <stdint.h>
   7
   8 void *memcpy(void *dst, const void *src, size_t n)
   9 {
  10         const char *p = src;
  11         char *q = dst;
  12 #if defined(__i386__)
  13         size_t nl = n >> 2;
  14         asm volatile ("cld ; rep ; movsl ; movl %3,%0 ; rep ; movsb":"+c" (nl),
  15                       "+S"(p), "+D"(q)
  16                       :"r"(n & 3));
  17 #elif defined(__x86_64__)
  18         size_t nq = n >> 3;
  19         asm volatile ("cld ; rep ; movsq ; movl %3,%%ecx ; rep ; movsb":"+c"
  20                       (nq), "+S"(p), "+D"(q)
  21                       :"r"((uint32_t) (n & 7)));
  22 #else
  23         while (n--) {
  24                 *q++ = *p++;
  25         }
  26 #endif
  27
  28         return dst;
  29 }