Change LookupForWrite to always do a full lookup and check the result.

src/ia32/stub-cache-ia32.cc

Index: src/ia32/stub-cache-ia32.cc
diff --git a/src/ia32/stub-cache-ia32.cc b/src/ia32/stub-cache-ia32.cc
index f7e795e788f7aab6ec397302f70121496c566d3b..a4523e3314d8a275f23940470dac2d6c5d48b01c 100644
--- a/src/ia32/stub-cache-ia32.cc
+++ b/src/ia32/stub-cache-ia32.cc
@@ -730,7 +730,7 @@ void BaseStoreStubCompiler::GenerateRestoreName(MacroAssembler* masm,
 // but may be destroyed if store is successful.
 void StubCompiler::GenerateStoreField(MacroAssembler* masm,
                                       Handle<JSObject> object,
-                                      int index,
+                                      LookupResult* lookup,
                                       Handle<Map> transition,
                                       Handle<Name> name,
                                       Register receiver_reg,
@@ -740,16 +740,6 @@ void StubCompiler::GenerateStoreField(MacroAssembler* masm,
                                       Register scratch2,
                                       Label* miss_label,
                                       Label* miss_restore_name) {
-  LookupResult lookup(masm->isolate());
-  object->Lookup(*name, &lookup);
-  if (lookup.IsFound() && (lookup.IsReadOnly() || !lookup.IsCacheable())) {
-    // In sloppy mode, we could just return the value and be done. However, we
-    // might be in strict mode, where we have to throw. Since we cannot tell,
-    // go into slow case unconditionally.
-    __ jmp(miss_label);
-    return;
-  }
-
   // Check that the map of the object hasn't changed.
   CompareMapMode mode = transition.is_null() ? ALLOW_ELEMENT_TRANSITION_MAPS
                                              : REQUIRE_EXACT_MAP;
@@ -764,8 +754,8 @@ void StubCompiler::GenerateStoreField(MacroAssembler* masm,
   // Check that we are allowed to write this.
   if (!transition.is_null() && object->GetPrototype()->IsJSObject()) {
     JSObject* holder;
-    if (lookup.IsFound()) {
-      holder = lookup.holder();
+    if (lookup->IsFound()) {
+      holder = lookup->holder();
     } else {
       // Find the top object.
       holder = *object;
@@ -799,6 +789,7 @@ void StubCompiler::GenerateStoreField(MacroAssembler* masm,
     return;
   }
 
+  int index;
   if (!transition.is_null()) {
     // Update the map of the object.
     __ mov(scratch1, Immediate(transition));
@@ -813,8 +804,13 @@ void StubCompiler::GenerateStoreField(MacroAssembler* masm,
                         kDontSaveFPRegs,
                         OMIT_REMEMBERED_SET,
                         OMIT_SMI_CHECK);
+    index = transition->instance_descriptors()->GetFieldIndex(
+        transition->LastAdded());
+  } else {
+    index = lookup->GetFieldIndex().field_index();
   }
 
+
   // Adjust for the number of properties stored in the object. Even in the
   // face of a transition we can use the old map here because the size of the
   // object and the number of in-object properties is not going to change.