Mark maps having a hidden prototype rather than maps of hidden prototypes.

src/x64/builtins-x64.cc

Index: src/x64/builtins-x64.cc
diff --git a/src/x64/builtins-x64.cc b/src/x64/builtins-x64.cc
index 381b9411c53a2d7696ef975a7dd3f9305b43a9a9..d9ff366ed85345fb7a8b3b7b13a07803273d1833 100644
--- a/src/x64/builtins-x64.cc
+++ b/src/x64/builtins-x64.cc
@@ -2741,14 +2741,11 @@ static void CompatibleReceiverCheck(MacroAssembler* masm, Register receiver,
 
   // Load the next prototype.
   __ bind(&next_prototype);
-  __ movp(receiver, FieldOperand(map, Map::kPrototypeOffset));
-  // End if the prototype is null or not hidden.
-  __ CompareRoot(receiver, Heap::kNullValueRootIndex);
-  __ j(equal, receiver_check_failed);
-  __ movp(map, FieldOperand(receiver, HeapObject::kMapOffset));
   __ testq(FieldOperand(map, Map::kBitField3Offset),
-           Immediate(Map::IsHiddenPrototype::kMask));
+           Immediate(Map::HasHiddenPrototype::kMask));
   __ j(zero, receiver_check_failed);
+  __ movp(receiver, FieldOperand(map, Map::kPrototypeOffset));
+  __ movp(map, FieldOperand(receiver, HeapObject::kMapOffset));
   // Iterate.
   __ jmp(&prototype_loop_start, Label::kNear);