Handle keyed stores after elements transition monomorphically if possible

src/type-info.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 405 matching lines @@
   } else if (object->IsMap()) {
     types->Add(Handle<Map>::cast(object));
   } else if (Handle<Code>::cast(object)->ic_state() == MEGAMORPHIC) {
     types->Reserve(4);
     ASSERT(object->IsCode());
     isolate_->stub_cache()->CollectMatchingMaps(types, *name, flags);
   }
 }
 
 
+static void AddMapIfMissing(Handle<Map> map, SmallMapList* list) {
+  for (int i = 0; i < list->length(); ++i) {
+    if (list->at(i).is_identical_to(map)) return;
+  }
+  list->Add(map);
+}
+
+
 void TypeFeedbackOracle::CollectKeyedReceiverTypes(unsigned ast_id,
                                                    SmallMapList* types) {
   Handle<Object> object = GetInfo(ast_id);
   if (!object->IsCode()) return;
   Handle<Code> code = Handle<Code>::cast(object);
   if (code->kind() == Code::KEYED_LOAD_IC ||
       code->kind() == Code::KEYED_STORE_IC) {
     AssertNoAllocation no_allocation;
     int mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
     for (RelocIterator it(*code, mask); !it.done(); it.next()) {
       RelocInfo* info = it.rinfo();
       Object* object = info->target_object();
       if (object->IsMap()) {
-        types->Add(Handle<Map>(Map::cast(object)));
+        AddMapIfMissing(Handle<Map>(Map::cast(object)), types);
       }
     }
   }
 }
 
 
 byte TypeFeedbackOracle::ToBooleanTypes(unsigned ast_id) {
   Handle<Object> object = GetInfo(ast_id);
   return object->IsCode() ? Handle<Code>::cast(object)->to_boolean_state() : 0;
 }
@@ skipping 111 matching lines @@
   USE(maybe_result);
 #ifdef DEBUG
   Object* result = NULL;
   // Dictionary has been allocated with sufficient size for all elements.
   ASSERT(maybe_result->ToObject(&result));
   ASSERT(*dictionary_ == result);
 #endif
 }
 
 } }  // namespace v8::internal