Bug 1382745 - Improve the hashing of StackShape, especially on 64-bit systems; r=jandem

js/src/vm/Shape.h

@@ -1488,15 +1488,9 @@ struct StackShape
     }
 
     HashNumber hash() const {
-        HashNumber hash = uintptr_t(base);
+        HashNumber hash = HashId(propid);
-
+        return mozilla::AddToHash(hash,
-        /* Accumulate from least to most random so the low bits are most random. */
+                   mozilla::HashGeneric(base, attrs, slot_, rawGetter, rawSetter));
-        hash = mozilla::RotateLeft(hash, 4) ^ attrs;
-        hash = mozilla::RotateLeft(hash, 4) ^ slot_;
-        hash = mozilla::RotateLeft(hash, 4) ^ HashId(propid);
-        hash = mozilla::RotateLeft(hash, 4) ^ uintptr_t(rawGetter);
-        hash = mozilla::RotateLeft(hash, 4) ^ uintptr_t(rawSetter);
-        return hash;
     }
 
     // Traceable implementation.