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

src/ia32/builtins-ia32.cc

Index: src/ia32/builtins-ia32.cc
diff --git a/src/ia32/builtins-ia32.cc b/src/ia32/builtins-ia32.cc
index 3a9b4734e34bba0d905e19afef90025da458868c..3e56a584c6ea06dbc23b751e4ea3e6cc88895fd5 100644
--- a/src/ia32/builtins-ia32.cc
+++ b/src/ia32/builtins-ia32.cc
@@ -2663,14 +2663,12 @@ static void CompatibleReceiverCheck(MacroAssembler* masm, Register receiver,
   // Load the next prototype.
   __ bind(&next_prototype);
   __ mov(receiver, FieldOperand(receiver, HeapObject::kMapOffset));
+  __ test(FieldOperand(receiver, Map::kBitField3Offset),
+          Immediate(Map::HasHiddenPrototype::kMask));
+  __ j(zero, receiver_check_failed);
+
   __ mov(receiver, FieldOperand(receiver, Map::kPrototypeOffset));
-  // End if the prototype is null or not hidden.
-  __ CompareRoot(receiver, Heap::kNullValueRootIndex);
-  __ j(equal, receiver_check_failed);
   __ mov(scratch0, FieldOperand(receiver, HeapObject::kMapOffset));
-  __ test(FieldOperand(scratch0, Map::kBitField3Offset),
-          Immediate(Map::IsHiddenPrototype::kMask));
-  __ j(zero, receiver_check_failed);
   // Iterate.
   __ jmp(&prototype_loop_start, Label::kNear);