#include <string.h>
+#include <stdint.h>
+
+#ifdef __GNUC__
+typedef __attribute__((__may_alias__)) size_t WT;
+#define WS (sizeof(WT))
+#endif
void *memmove(void *dest, const void *src, size_t n)
{
char *d = dest;
const char *s = src;
+
if (d==s) return d;
- if ((size_t)(d-s) < n)
- while (n--) d[n] = s[n];
- else
- while (n--) *d++ = *s++;
+ if ((uintptr_t)s-(uintptr_t)d-n <= -2*n) return memcpy(d, s, n);
+
+ if (d<s) {
+#ifdef __GNUC__
+ if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
+ while ((uintptr_t)d % WS) {
+ if (!n--) return dest;
+ *d++ = *s++;
+ }
+ for (; n>=WS; n-=WS, d+=WS, s+=WS) *(WT *)d = *(WT *)s;
+ }
+#endif
+ for (; n; n--) *d++ = *s++;
+ } else {
+#ifdef __GNUC__
+ if ((uintptr_t)s % WS == (uintptr_t)d % WS) {
+ while ((uintptr_t)(d+n) % WS) {
+ if (!n--) return dest;
+ d[n] = s[n];
+ }
+ while (n>=WS) n-=WS, *(WT *)(d+n) = *(WT *)(s+n);
+ }
+#endif
+ while (n) n--, d[n] = s[n];
+ }
+
return dest;
}