void *memcpy_fast(void *s1, const void *s2, size_t n);
memcpy_fast copies n characters from the object pointed to by s2 into the object pointed to by s1. The behavior of memcpy_fast is undefined if copying takes place between objects that overlap. The implementation of memcpy_fast is optimized for speed for all cases of memcpy and as such has a large code memory requirement. This function is implemented for little-endian ARM and 32-bit Thumb-2 instruction sets only.
memcpy_fast returns the value of s1.