/* * memcpy.c */ #include #include void *memcpy(void *dst, const void *src, size_t n) { const char *p = src; char *q = dst; #if defined(__i386__) size_t nl = n >> 2; asm volatile ("cld ; rep ; movsl ; movl %3,%0 ; rep ; movsb":"+c" (nl), "+S"(p), "+D"(q) :"r"(n & 3)); #elif defined(__x86_64__) size_t nq = n >> 3; asm volatile ("cld ; rep ; movsq ; movl %3,%%ecx ; rep ; movsb":"+c" (nq), "+S"(p), "+D"(q) :"r"((uint32_t) (n & 7))); #else while (n--) { *q++ = *p++; } #endif return dst; }