Append to descriptors over map.

Review URL: https://chromiumcodereview.appspot.com/10800033

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12141 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/factory.cc

@@ -912,6 +912,8 @@ void Factory::CopyAppendCallbackDescriptors(Handle<Map> map,
     }
   }
 
+  map->set_instance_descriptors(*result);
+
   // Fill in new callback descriptors.  Process the callbacks from
   // back to front so that the last callback with a given name takes
   // precedence over previously added callbacks with that name.
@@ -925,13 +927,16 @@ void Factory::CopyAppendCallbackDescriptors(Handle<Map> map,
     if (LinearSearch(*result, *key, result->NumberOfSetDescriptors()) ==
         DescriptorArray::kNotFound) {
       CallbacksDescriptor desc(*key, *entry, entry->property_attributes());
-      result->Append(&desc, witness);
+      map->AppendDescriptor(&desc, witness);
     }
   }
 
   int new_number_of_descriptors = result->NumberOfSetDescriptors();
-  // Don't replace the descriptor array if there were no new elements.
-  if (new_number_of_descriptors == descriptor_count) return;
+  // Reinstall the original descriptor array if no new elements were added.
+  if (new_number_of_descriptors == descriptor_count) {
+    map->set_instance_descriptors(*array);
+    return;
+  }
 
   // If duplicates were detected, allocate a result of the right size
   // and transfer the elements.
@@ -942,10 +947,8 @@ void Factory::CopyAppendCallbackDescriptors(Handle<Map> map,
       new_result->CopyFrom(i, *result, i, witness);
     }
     new_result->SetLastAdded(result->LastAdded());
-    result = new_result;
+    map->set_instance_descriptors(*new_result);
   }
-
-  map->set_instance_descriptors(*result);
 }
 
 

src/objects-inl.h

@@ -2110,9 +2110,10 @@ void DescriptorArray::Set(int descriptor_number,
 }
 
 
-void DescriptorArray::Append(Descriptor* desc,
-                             const WhitenessWitness& witness) {
-  int descriptor_number = NumberOfSetDescriptors();
+int DescriptorArray::Append(Descriptor* desc,
+                            const WhitenessWitness& witness,
+                            int number_of_set_descriptors) {
+  int descriptor_number = number_of_set_descriptors;
   int enumeration_index = descriptor_number + 1;
   desc->SetEnumerationIndex(enumeration_index);
 
@@ -2128,7 +2129,7 @@ void DescriptorArray::Append(Descriptor* desc,
   }
 
   Set(descriptor_number, desc, witness);
-  SetLastAdded(descriptor_number);
+  return descriptor_number;
 }
 
 
@@ -3554,6 +3555,14 @@ void Map::ClearDescriptorArray(Heap* heap, WriteBarrierMode mode) {
 }
 
 
+void Map::AppendDescriptor(Descriptor* desc,
+                           const DescriptorArray::WhitenessWitness& witness) {
+  DescriptorArray* descriptors = instance_descriptors();
+  int set_descriptors = descriptors->NumberOfSetDescriptors();
+  int new_last_added = descriptors->Append(desc, witness, set_descriptors);
+  descriptors->SetLastAdded(new_last_added);
+}
+
 
 Object* Map::GetBackPointer() {
   Object* object = READ_FIELD(this, kInstanceDescriptorsOrBackPointerOffset);

src/objects.h

@@ -2544,8 +2544,9 @@ class DescriptorArray: public FixedArray {
   // Append automatically sets the enumeration index. This should only be used
   // to add descriptors in bulk at the end, followed by sorting the descriptor
   // array.
-  inline void Append(Descriptor* desc,
-                     const WhitenessWitness&);
+  inline int Append(Descriptor* desc,
+                    const WhitenessWitness&,
+                    int number_of_set_descriptors);
 
   // Transfer a complete descriptor from the src descriptor array to this
   // descriptor array.
@@ -4925,6 +4926,9 @@ class Map: public HeapObject {
   MUST_USE_RESULT MaybeObject* CopyNormalized(PropertyNormalizationMode mode,
                                               NormalizedMapSharingMode sharing);
 
+  inline void AppendDescriptor(Descriptor* desc,
+                               const DescriptorArray::WhitenessWitness&);
+
   // Returns a copy of the map, with all transitions dropped from the
   // instance descriptors.
   MUST_USE_RESULT MaybeObject* Copy(DescriptorArray::SharedMode shared_mode);