gcc 4.3.2 miscompiles byte_diff :-(

byte/byte_diff.c

@@ -6,6 +6,8 @@
  * one[len-1]. When the strings are different, byte_diff does not read
  * bytes past the first difference. */
 int byte_diff(const void* a, size_t len, const void* b) {
+#if 0
+  /* this gets miscompiled by gcc 4.3.2 on x86_64 */
   register const unsigned char* s=a;
   register const unsigned char* t=b;
   register const unsigned char* u=t+len;
@@ -18,4 +20,12 @@ int byte_diff(const void* a, size_t len, const void* b) {
     if (t==u) break; if ((j=((unsigned int)*s-*t))) break; ++s; ++t;
   }
   return j;
+#else
+  size_t i;
+  for (i=0; i<len; ++i) {
+    int r=((unsigned char*)a)[i] - ((unsigned char*)b)[i];
+    if (r) return r;
+  }
+  return 0;
+#endif
 }