+#ifdef USE_MMX
+#define memcpy64(dest, src, count) asm volatile ( \
+ "0:\n\t" \
+ "movq (%1), %%mm0\n\t" \
+ "movq %%mm0, (%0)\n\t" \
+ "add $8, %1\n\t" \
+ "add $8, %0\n\t" \
+ "dec %2\n\t" \
+ "jnz 0b\n\t" \
+ "emms\n\t" \
+ :: "r"(dest), "r"(src), "r"(count) \
+ : "%mm0")
+#else
+#define memcpy64(dest, src, count) memcpy(dest, src, (count) << 3)
+#endif
+