[runtime] More LookupIterator / Transition related performance tweaks

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 9826 matching lines @@
 FieldType* DescriptorArray::GetFieldType(int descriptor_number) {
   DCHECK(GetDetails(descriptor_number).location() == kField);
   Object* value = GetValue(descriptor_number);
   if (value->IsWeakCell()) {
     if (WeakCell::cast(value)->cleared()) return FieldType::None();
     value = WeakCell::cast(value)->value();
   }
   return FieldType::cast(value);
 }
 
-bool DescriptorArray::CanHoldValue(int descriptor, Object* value) {
-  PropertyDetails details = GetDetails(descriptor);
+namespace {
+
+bool CanHoldValue(DescriptorArray* descriptors, int descriptor, Object* value) {
+  PropertyDetails details = descriptors->GetDetails(descriptor);
   switch (details.type()) {
     case DATA:
       return value->FitsRepresentation(details.representation()) &&
-             GetFieldType(descriptor)->NowContains(value);
+             descriptors->GetFieldType(descriptor)->NowContains(value);
 
     case DATA_CONSTANT:
-      DCHECK(GetConstant(descriptor) != value ||
+      DCHECK(descriptors->GetConstant(descriptor) != value ||
              value->FitsRepresentation(details.representation()));
-      return GetConstant(descriptor) == value;
+      return descriptors->GetConstant(descriptor) == value;
 
     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;
+  if (CanHoldValue(map->instance_descriptors(), 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;
-
+  DCHECK(!map->is_dictionary_map());
   // 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;
+  DCHECK(!map->is_dictionary_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();
 
@@ skipping 10009 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