Add map-based read barrier to WeakCell

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index 77269429821307466e85c9c87554e810808700ee..7fcf70e4ec95085218626352f73ac8212a276a77 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -3777,11 +3777,12 @@ void CompareICStub::GenerateObjects(MacroAssembler* masm) {
 void CompareICStub::GenerateKnownObjects(MacroAssembler* masm) {
   Label miss;
   Handle<WeakCell> cell = Map::WeakCellForMap(known_map_);
+  // Combine two Smi tests into one with bitwise and.
   __ mov(ecx, edx);
   __ and_(ecx, eax);
   __ JumpIfSmi(ecx, &miss, Label::kNear);
 
-  __ GetWeakValue(edi, cell);
+  __ GetWeakValueNoReadBarrier(edi, cell);
   __ mov(ecx, FieldOperand(eax, HeapObject::kMapOffset));
   __ mov(ebx, FieldOperand(edx, HeapObject::kMapOffset));
   __ cmp(ecx, edi);