Couple the enumeration index of a property to the size of the descriptor array where it first appea…

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2457 matching lines @@
   inline void ClearTransitions();
 
   // Returns the number of descriptors in the array.
   int number_of_descriptors() {
     ASSERT(MayContainTransitions() || IsEmpty());
     int len = length();
     return len <= kFirstIndex ? 0 : (len - kFirstIndex) / kDescriptorSize;
   }
 
   inline int number_of_entries() { return number_of_descriptors(); }
+  inline int NextEnumerationIndex() { return number_of_descriptors() + 1; }
 
   int LastAdded() {
     ASSERT(!IsEmpty());
     Object* obj = get(kLastAddedIndex);
     if (obj->IsSmi()) {
       return Smi::cast(obj)->value();
     } else {
       Object* index = FixedArray::cast(obj)->get(kEnumCacheBridgeLastAdded);
       return Smi::cast(index)->value();
     }
   }
 
-  int NextEnumerationIndex() {
-    if (number_of_descriptors() == 0) {
-      return PropertyDetails::kInitialIndex;
-    }
-    return GetDetails(LastAdded()).index() + 1;
-  }
-
   // Set index of the last added descriptor and flush any enum cache.
   void SetLastAdded(int index) {
     ASSERT(!IsEmpty() || index > 0);
     set(kLastAddedIndex, Smi::FromInt(index));
   }
 
+  int NumberOfSetDescriptors() {
+    ASSERT(!IsEmpty());
+    if (LastAdded() == kNoneAdded) return 0;
+    return GetDetails(LastAdded()).index();
+  }
+
   bool HasEnumCache() {
     return !IsEmpty() && !get(kLastAddedIndex)->IsSmi();
   }
 
   Object* GetEnumCache() {
     ASSERT(HasEnumCache());
     FixedArray* bridge = FixedArray::cast(get(kLastAddedIndex));
     return bridge->get(kEnumCacheBridgeCacheIndex);
   }
 
@@ skipping 26 matching lines @@
   inline int GetFieldIndex(int descriptor_number);
   inline JSFunction* GetConstantFunction(int descriptor_number);
   inline Object* GetCallbacksObject(int descriptor_number);
   inline AccessorDescriptor* GetCallbacks(int descriptor_number);
 
   // Accessor for complete descriptor.
   inline void Get(int descriptor_number, Descriptor* desc);
   inline void Set(int descriptor_number,
                   Descriptor* desc,
                   const WhitenessWitness&);
+  // 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&);
 
   // Transfer a complete descriptor from the src descriptor array to the dst
   // one, dropping map transitions in CALLBACKS.
   static void CopyFrom(Handle<DescriptorArray> dst,
                        int dst_index,
                        Handle<DescriptorArray> src,
                        int src_index,
                        const WhitenessWitness& witness);
 
   // Transfer a complete descriptor from the src descriptor array to this
@@ skipping 47 matching lines @@
   // empty descriptor array object if number_of_descriptors is 0.
   MUST_USE_RESULT static MaybeObject* Allocate(int number_of_descriptors,
                                                SharedMode shared_mode);
 
   // Casting.
   static inline DescriptorArray* cast(Object* obj);
 
   // Constant for denoting key was not found.
   static const int kNotFound = -1;
 
+  // Constant for denoting that the LastAdded field was not yet set.
+  static const int kNoneAdded = -1;
+
   static const int kBackPointerStorageIndex = 0;
   static const int kLastAddedIndex = 1;
   static const int kTransitionsIndex = 2;
   static const int kFirstIndex = 3;
 
   // The length of the "bridge" to the enum cache.
   static const int kEnumCacheBridgeLength = 3;
   static const int kEnumCacheBridgeLastAdded = 0;
   static const int kEnumCacheBridgeCacheIndex = 1;
   static const int kEnumCacheBridgeIndicesCacheIndex = 2;
@@ skipping 6259 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_