Avoid duplicate lookups when Get+Creating identity hashes

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 5faa79ef646162a8e4cf71c41a0f4748fcd1ccec..8800b99e22300c06b4a8a21392b6c544ecb0aa8a 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -836,14 +836,6 @@ MaybeHandle<Object> JSProxy::GetProperty(Isolate* isolate,
 }
 
 
-Handle<Object> JSReceiver::GetDataProperty(Handle<JSReceiver> object,
-                                           Handle<Name> name) {
-  LookupIterator it(object, name,
-                    LookupIterator::PROTOTYPE_CHAIN_SKIP_INTERCEPTOR);
-  return GetDataProperty(&it);
-}
-
-
 Handle<Object> JSReceiver::GetDataProperty(LookupIterator* it) {
   for (; it->IsFound(); it->Next()) {
     switch (it->state()) {
@@ -5856,14 +5848,6 @@ static Smi* GenerateIdentityHash(Isolate* isolate) {
 }
 
 
-void JSObject::SetIdentityHash(Handle<JSObject> object, Handle<Smi> hash) {
-  DCHECK(!object->IsJSGlobalProxy());
-  Isolate* isolate = object->GetIsolate();
-  Handle<Name> hash_code_symbol = isolate->factory()->hash_code_symbol();
-  JSObject::AddProperty(object, hash_code_symbol, hash, NONE);
-}
-
-
 template<typename ProxyType>
 static Handle<Smi> GetOrCreateIdentityHashHelper(Handle<ProxyType> proxy) {
   Isolate* isolate = proxy->GetIsolate();
@@ -5893,11 +5877,18 @@ Handle<Smi> JSObject::GetOrCreateIdentityHash(Handle<JSObject> object) {
   }
   Isolate* isolate = object->GetIsolate();
 
-  Handle<Object> maybe_hash = JSObject::GetIdentityHash(isolate, object);
-  if (maybe_hash->IsSmi()) return Handle<Smi>::cast(maybe_hash);
+  Handle<Name> hash_code_symbol = isolate->factory()->hash_code_symbol();
+  LookupIterator it(object, hash_code_symbol, LookupIterator::OWN);
+  if (it.IsFound()) {
+    DCHECK_EQ(LookupIterator::DATA, it.state());
+    Handle<Object> maybe_hash = it.GetDataValue();
+    if (maybe_hash->IsSmi()) return Handle<Smi>::cast(maybe_hash);
+  }
 
   Handle<Smi> hash(GenerateIdentityHash(isolate), isolate);
-  SetIdentityHash(object, hash);
+  CHECK(AddDataProperty(&it, hash, NONE, THROW_ON_ERROR,
+                        CERTAINLY_NOT_STORE_FROM_KEYED)
+            .IsJust());
   return hash;
 }