[runtime] Minor tweaks to LookupIterator for performance

src/objects.cc

 // Copyright 2015 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/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 3146 matching lines @@
   InvalidatePrototypeChains(object->map());
   Handle<Map> old_map(object->map());
 
   // If the map was registered with its prototype before, ensure that it
   // registers with its new prototype now. This preserves the invariant that
   // when a map on a prototype chain is registered with its prototype, then
   // all prototypes further up the chain are also registered with their
   // respective prototypes.
   UpdatePrototypeUserRegistration(old_map, new_map, new_map->GetIsolate());
 
-  if (object->HasFastProperties()) {
-    if (!new_map->is_dictionary_map()) {
-      MigrateFastToFast(object, new_map);
-      if (old_map->is_prototype_map()) {
-        DCHECK(!old_map->is_stable());
-        DCHECK(new_map->is_stable());
-        // Clear out the old descriptor array to avoid problems to sharing
-        // the descriptor array without using an explicit.
-        old_map->InitializeDescriptors(
-            old_map->GetHeap()->empty_descriptor_array(),
-            LayoutDescriptor::FastPointerLayout());
-        // Ensure that no transition was inserted for prototype migrations.
-        DCHECK_EQ(0, TransitionArray::NumberOfTransitions(
-                         old_map->raw_transitions()));
-        DCHECK(new_map->GetBackPointer()->IsUndefined());
-      }
-    } else {
-      MigrateFastToSlow(object, new_map, expected_additional_properties);
-    }
-  } else {
+  if (old_map->is_dictionary_map()) {
     // For slow-to-fast migrations JSObject::MigrateSlowToFast()
     // must be used instead.
     CHECK(new_map->is_dictionary_map());
 
     // Slow-to-slow migration is trivial.
     object->set_map(*new_map);
+  } else if (!new_map->is_dictionary_map()) {
+    MigrateFastToFast(object, new_map);
+    if (old_map->is_prototype_map()) {
+      DCHECK(!old_map->is_stable());
+      DCHECK(new_map->is_stable());
+      // Clear out the old descriptor array to avoid problems to sharing
+      // the descriptor array without using an explicit.
+      old_map->InitializeDescriptors(
+          old_map->GetHeap()->empty_descriptor_array(),
+          LayoutDescriptor::FastPointerLayout());
+      // Ensure that no transition was inserted for prototype migrations.
+      DCHECK_EQ(
+          0, TransitionArray::NumberOfTransitions(old_map->raw_transitions()));
+      DCHECK(new_map->GetBackPointer()->IsUndefined());
+    }
+  } else {
+    MigrateFastToSlow(object, new_map, expected_additional_properties);
   }
 
   // Careful: Don't allocate here!
   // For some callers of this method, |object| might be in an inconsistent
   // state now: the new map might have a new elements_kind, but the object's
   // elements pointer hasn't been updated yet. Callers will fix this, but in
   // the meantime, (indirectly) calling JSObjectVerify() must be avoided.
   // When adding code here, add a DisallowHeapAllocation too.
 }
 
@@ skipping 1398 matching lines @@
   DCHECK_NE(LookupIterator::INTEGER_INDEXED_EXOTIC, it->state());
 
   Handle<JSObject> receiver = it->GetStoreTarget();
 
   // If the receiver is a JSGlobalProxy, store on the prototype (JSGlobalObject)
   // instead. If the prototype is Null, the proxy is detached.
   if (receiver->IsJSGlobalProxy()) return Just(true);
 
   Isolate* isolate = it->isolate();
 
-  if (!receiver->map()->is_extensible() &&
-      (it->IsElement() || !isolate->IsInternallyUsedPropertyName(it->name()))) {
+  if (it->ExtendingNonExtensible(receiver)) {
     RETURN_FAILURE(
         isolate, should_throw,
         NewTypeError(MessageTemplate::kObjectNotExtensible, it->GetName()));
   }
 
   if (it->IsElement()) {
     if (receiver->IsJSArray()) {
       Handle<JSArray> array = Handle<JSArray>::cast(receiver);
       if (JSArray::WouldChangeReadOnlyLength(array, it->index())) {
         RETURN_FAILURE(array->GetIsolate(), should_throw,
@@ skipping 12 matching lines @@
       }
     }
 
     Maybe<bool> result = JSObject::AddDataElement(receiver, it->index(), value,
                                                   attributes, should_throw);
     JSObject::ValidateElements(receiver);
     return result;
   } else {
     // Migrate to the most up-to-date map that will be able to store |value|
     // under it->name() with |attributes|.
-    it->PrepareTransitionToDataProperty(value, attributes, store_mode);
+    it->PrepareTransitionToDataProperty(receiver, value, attributes,
+                                        store_mode);
     DCHECK_EQ(LookupIterator::TRANSITION, it->state());
-    it->ApplyTransitionToDataProperty();
+    it->ApplyTransitionToDataProperty(receiver);
 
     // TODO(verwaest): Encapsulate dictionary handling better.
     if (receiver->map()->is_dictionary_map()) {
       // TODO(verwaest): Probably should ensure this is done beforehand.
       it->InternalizeName();
       // TODO(dcarney): just populate TransitionPropertyCell here?
       JSObject::AddSlowProperty(receiver, it->name(), value, attributes);
     } else {
       // Write the property value.
       it->WriteDataValue(value);
@@ skipping 5265 matching lines @@
 
     case ACCESSOR:
     case ACCESSOR_CONSTANT:
       return false;
   }
 
   UNREACHABLE();
   return false;
 }
 
+namespace {
+
+Handle<Map> UpdateDescriptorForValue(Handle<Map> map, int descriptor,
+                                     Handle<Object> value) {
+  if (map->instance_descriptors()->CanHoldValue(descriptor, *value)) return map;
+
+  Isolate* isolate = map->GetIsolate();
+  PropertyAttributes attributes =
+      map->instance_descriptors()->GetDetails(descriptor).attributes();
+  Representation representation = value->OptimalRepresentation();
+  Handle<FieldType> type = value->OptimalType(isolate, representation);
+
+  return Map::ReconfigureProperty(map, descriptor, kData, attributes,
+                                  representation, type, FORCE_FIELD);
+}
+
+}  // namespace
 
 // static
 Handle<Map> Map::PrepareForDataProperty(Handle<Map> map, int descriptor,
                                         Handle<Object> value) {
   // Dictionaries can store any property value.
   if (map->is_dictionary_map()) return map;
 
-  // Migrate to the newest map before storing the property.
-  map = Update(map);
-
-  Handle<DescriptorArray> descriptors(map->instance_descriptors());
-
-  if (descriptors->CanHoldValue(descriptor, *value)) return map;
-
-  Isolate* isolate = map->GetIsolate();
-  PropertyAttributes attributes =
-      descriptors->GetDetails(descriptor).attributes();
-  Representation representation = value->OptimalRepresentation();
-  Handle<FieldType> type = value->OptimalType(isolate, representation);
-
-  return ReconfigureProperty(map, descriptor, kData, attributes, representation,
-                             type, FORCE_FIELD);
+  // Update to the newest map before storing the property.
+  return UpdateDescriptorForValue(Update(map), descriptor, value);
 }
 
 
 Handle<Map> Map::TransitionToDataProperty(Handle<Map> map, Handle<Name> name,
                                           Handle<Object> value,
                                           PropertyAttributes attributes,
                                           StoreFromKeyed store_mode) {
   // Dictionary maps can always have additional data properties.
   if (map->is_dictionary_map()) return map;
 
   // Migrate to the newest map before storing the property.
   map = Update(map);
 
   Map* maybe_transition =
       TransitionArray::SearchTransition(*map, kData, *name, attributes);
   if (maybe_transition != NULL) {
     Handle<Map> transition(maybe_transition);
     int descriptor = transition->LastAdded();
 
     DCHECK_EQ(attributes, transition->instance_descriptors()
                               ->GetDetails(descriptor)
                               .attributes());
 
-    return Map::PrepareForDataProperty(transition, descriptor, value);
+    return UpdateDescriptorForValue(transition, descriptor, value);
   }
 
   TransitionFlag flag = INSERT_TRANSITION;
   MaybeHandle<Map> maybe_map;
   if (value->IsJSFunction()) {
     maybe_map = Map::CopyWithConstant(map, name, value, attributes, flag);
   } else if (!map->TooManyFastProperties(store_mode)) {
     Isolate* isolate = name->GetIsolate();
     Representation representation = value->OptimalRepresentation();
     Handle<FieldType> type = value->OptimalType(isolate, representation);
@@ skipping 9994 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8