[runtime] Minor tweaks to LookupIterator for performance

src/lookup.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/lookup.h"
 
 #include "src/bootstrapper.h"
 #include "src/deoptimizer.h"
 #include "src/elements.h"
 #include "src/isolate-inl.h"
@@ skipping 104 matching lines @@
 
 
 Handle<Map> LookupIterator::GetReceiverMap() const {
   if (receiver_->IsNumber()) return factory()->heap_number_map();
   return handle(Handle<HeapObject>::cast(receiver_)->map(), isolate_);
 }
 
 
 Handle<JSObject> LookupIterator::GetStoreTarget() const {
   if (receiver_->IsJSGlobalProxy()) {
-    PrototypeIterator iter(isolate(), Handle<JSGlobalProxy>::cast(receiver_));
-    if (iter.IsAtEnd()) return Handle<JSGlobalProxy>::cast(receiver_);
-    return PrototypeIterator::GetCurrent<JSGlobalObject>(iter);
+    Object* prototype = JSGlobalProxy::cast(*receiver_)->map()->prototype();
+    if (!prototype->IsNull()) return handle(JSGlobalObject::cast(prototype));

[Camillo Bruni, 2016/02/16 08:58:39]

handle(JSGlobalObject::cast(prototype), isolate_) ?

   }
   return Handle<JSObject>::cast(receiver_);
 }
 
 
 bool LookupIterator::HasAccess() const {
   DCHECK_EQ(ACCESS_CHECK, state_);
   return isolate_->MayAccess(handle(isolate_->context()),
                              GetHolder<JSObject>());
 }
@@ skipping 87 matching lines @@
   ReloadPropertyInformation();
   WriteDataValue(value);
 
 #if VERIFY_HEAP
   if (FLAG_verify_heap) {
     holder->JSObjectVerify();
   }
 #endif
 }
 
-
+// Can only be called when the receiver is a JSObject. JSProxy has to be handled
+// via a trap. Adding properties to primitive values is not observable.
 void LookupIterator::PrepareTransitionToDataProperty(
-    Handle<Object> value, PropertyAttributes attributes,
-    Object::StoreFromKeyed store_mode) {
+    Handle<JSObject> receiver, Handle<Object> value,
+    PropertyAttributes attributes, Object::StoreFromKeyed store_mode) {
+  DCHECK(receiver.is_identical_to(GetStoreTarget()));
   if (state_ == TRANSITION) return;
   DCHECK(state_ != LookupIterator::ACCESSOR ||
          (GetAccessors()->IsAccessorInfo() &&
           AccessorInfo::cast(*GetAccessors())->is_special_data_property()));
   DCHECK_NE(INTEGER_INDEXED_EXOTIC, state_);
   DCHECK(state_ == NOT_FOUND || !HolderIsReceiverOrHiddenPrototype());
-  // Can only be called when the receiver is a JSObject. JSProxy has to be
-  // handled via a trap. Adding properties to primitive values is not
-  // observable.
-  Handle<JSObject> receiver = GetStoreTarget();
-
-  if (!isolate()->IsInternallyUsedPropertyName(name()) &&
-      !receiver->map()->is_extensible()) {
-    return;
-  }
 
   auto transition = Map::TransitionToDataProperty(
       handle(receiver->map(), isolate_), name_, value, attributes, store_mode);
   state_ = TRANSITION;
   transition_ = transition;
 
   if (receiver->IsJSGlobalObject()) {
     // Install a property cell.
     InternalizeName();
     auto cell = JSGlobalObject::EnsurePropertyCell(
         Handle<JSGlobalObject>::cast(receiver), name());
     DCHECK(cell->value()->IsTheHole());
     transition_ = cell;
   } else if (!transition->is_dictionary_map()) {
     property_details_ = transition->GetLastDescriptorDetails();
     has_property_ = true;
   }
 }
 
-
-void LookupIterator::ApplyTransitionToDataProperty() {
+void LookupIterator::ApplyTransitionToDataProperty(Handle<JSObject> receiver) {
   DCHECK_EQ(TRANSITION, state_);
 
-  Handle<JSObject> receiver = GetStoreTarget();
+  DCHECK(receiver.is_identical_to(GetStoreTarget()));
+
   if (receiver->IsJSGlobalObject()) return;
   holder_ = receiver;
   Handle<Map> transition = transition_map();
   bool simple_transition = transition->GetBackPointer() == receiver->map();
   holder_map_ = transition;
   JSObject::MigrateToMap(receiver, holder_map_);
 
   if (simple_transition) {
     int number = transition->LastAdded();
     number_ = static_cast<uint32_t>(number);
@@ skipping 405 matching lines @@
     // Fall through.
     default:
       return NOT_FOUND;
   }
   UNREACHABLE();
   return state_;
 }
 
 }  // namespace internal
 }  // namespace v8