Handlify Map::CopyDropDescriptors().

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 3329 matching lines @@
 // DescriptorArrays are fixed arrays used to hold instance descriptors.
 // The format of the these objects is:
 //   [0]: Number of descriptors
 //   [1]: Either Smi(0) if uninitialized, or a pointer to small fixed array:
 //          [0]: pointer to fixed array with enum cache
 //          [1]: either Smi(0) or pointer to fixed array with indices
 //   [2]: first key
 //   [2 + number of descriptors * kDescriptorSize]: start of slack
 class DescriptorArray: public FixedArray {
  public:
-  // WhitenessWitness is used to prove that a descriptor array is white
-  // (unmarked), so incremental write barriers can be skipped because the
-  // marking invariant cannot be broken and slots pointing into evacuation
-  // candidates will be discovered when the object is scanned. A witness is
-  // always stack-allocated right after creating an array. By allocating a
-  // witness, incremental marking is globally disabled. The witness is then
-  // passed along wherever needed to statically prove that the array is known to
-  // be white.
-  class WhitenessWitness {
-   public:
-    inline explicit WhitenessWitness(FixedArray* array);
-    inline ~WhitenessWitness();
-
-   private:
-    IncrementalMarking* marking_;
-  };
-
   // Returns true for both shared empty_descriptor_array and for smis, which the
   // map uses to encode additional bit fields when the descriptor array is not
   // yet used.
   inline bool IsEmpty();
 
   // Returns the number of descriptors in the array.
   int number_of_descriptors() {
     ASSERT(length() >= kFirstIndex || IsEmpty());
     int len = length();
     return len == 0 ? 0 : Smi::cast(get(kDescriptorLengthIndex))->value();
@@ skipping 69 matching lines @@
 
   inline Name* GetSortedKey(int descriptor_number);
   inline int GetSortedKeyIndex(int descriptor_number);
   inline void SetSortedKey(int pointer, int descriptor_number);
   inline void InitializeRepresentations(Representation representation);
   inline void SetRepresentation(int descriptor_number,
                                 Representation representation);
 
   // Accessor for complete descriptor.
   inline void Get(int descriptor_number, Descriptor* desc);
-  inline void Set(int descriptor_number,
-                  Descriptor* desc,
-                  const WhitenessWitness&);
+  inline void Set(int descriptor_number, Descriptor* desc);
   void Replace(int descriptor_number, Descriptor* descriptor);
 
   // 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 void Append(Descriptor* desc);
 
   static Handle<DescriptorArray> Merge(Handle<Map> left_map,
                                        int verbatim,
                                        int valid,
                                        int new_size,
                                        int modify_index,
                                        StoreMode store_mode,
                                        Handle<Map> right_map)
       V8_WARN_UNUSED_RESULT;
@@ skipping 74 matching lines @@
   bool IsEqualTo(DescriptorArray* other);
 #endif
 
   // Returns the fixed array length required to hold number_of_descriptors
   // descriptors.
   static int LengthFor(int number_of_descriptors) {
     return ToKeyIndex(number_of_descriptors);
   }
 
  private:
+  // WhitenessWitness is used to prove that a descriptor array is white
+  // (unmarked), so incremental write barriers can be skipped because the
+  // marking invariant cannot be broken and slots pointing into evacuation
+  // candidates will be discovered when the object is scanned. A witness is
+  // always stack-allocated right after creating an array. By allocating a
+  // witness, incremental marking is globally disabled. The witness is then
+  // passed along wherever needed to statically prove that the array is known to
+  // be white.
+  class WhitenessWitness {
+   public:
+    inline explicit WhitenessWitness(FixedArray* array);

[Toon Verwaest, 2014/04/11 10:37:59]

DescriptorArray* descriptors?

[mvstanton, 2014/04/11 11:25:20]

Sure.

+    inline ~WhitenessWitness();
+
+   private:
+    IncrementalMarking* marking_;
+  };
+
   // An entry in a DescriptorArray, represented as an (array, index) pair.
   class Entry {
    public:
     inline explicit Entry(DescriptorArray* descs, int index) :
         descs_(descs), index_(index) { }
 
     inline PropertyType type() { return descs_->GetType(index_); }
     inline Object* GetCallbackObject() { return descs_->GetValue(index_); }
 
    private:
@@ skipping 19 matching lines @@
            (descriptor_number * kDescriptorSize) +
            kDescriptorValue;
   }
 
   // Transfer a complete descriptor from the src descriptor array to this
   // descriptor array.
   void CopyFrom(int index,
                 DescriptorArray* src,
                 const WhitenessWitness&);
 
-  inline void Set(int descriptor_number, Descriptor* desc);
+  inline void Set(int descriptor_number,
+                  Descriptor* desc,
+                  const WhitenessWitness&);
+
+  inline void Append(Descriptor* desc, const WhitenessWitness&);
 
   // Swap first and second descriptor.
   inline void SwapSortedKeys(int first, int second);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(DescriptorArray);
 };
 
 
 enum SearchMode { ALL_ENTRIES, VALID_ENTRIES };
 
@@ skipping 482 matching lines @@
     ASSERT(obj->IsDictionary());
     return reinterpret_cast<NameDictionary*>(obj);
   }
 
   // Copies enumerable keys to preallocated fixed array.
   void CopyEnumKeysTo(FixedArray* storage);
   static void DoGenerateNewEnumerationIndices(
       Handle<NameDictionary> dictionary);
 
   // For transforming properties of a JSObject.
-  MUST_USE_RESULT MaybeObject* TransformPropertiesToFastFor(
-      JSObject* obj,
-      int unused_property_fields);
+  static void TransformPropertiesToFastFor(Handle<NameDictionary> dictionary,
+                                           Handle<JSObject> obj,
+                                           int unused_property_fields);
 
   // Find entry for key, otherwise return kNotFound. Optimized version of
   // HashTable::FindEntry.
   int FindEntry(Name* key);
 };
 
 
 class NumberDictionaryShape : public BaseShape<uint32_t> {
  public:
   static inline bool IsMatch(uint32_t key, Object* other);
@@ skipping 2274 matching lines @@
   // is found by re-transitioning from the root of the transition tree using the
   // descriptor array of the map. Returns NULL if no updated map is found.
   // This method also applies any pending migrations along the prototype chain.
   static Handle<Map> CurrentMapForDeprecated(Handle<Map> map);
   // Same as above, but does not touch the prototype chain.
   static Handle<Map> CurrentMapForDeprecatedInternal(Handle<Map> map);
 
   static Handle<Map> RawCopy(Handle<Map> map, int instance_size);
   MUST_USE_RESULT MaybeObject* RawCopy(int instance_size);
   static Handle<Map> CopyDropDescriptors(Handle<Map> map);
-  MUST_USE_RESULT MaybeObject* CopyDropDescriptors();
   static Handle<Map> CopyReplaceDescriptors(
       Handle<Map> map,
       Handle<DescriptorArray> descriptors,
       TransitionFlag flag,
       Handle<Name> name,
       SimpleTransitionFlag simple_flag = FULL_TRANSITION);
   static Handle<Map> CopyReplaceDescriptors(
       Handle<Map> map,
       Handle<DescriptorArray> descriptors,
       TransitionFlag flag,
@@ skipping 23 matching lines @@
   static Handle<Map> CopyAsElementsKind(Handle<Map> map,
                                         ElementsKind kind,
                                         TransitionFlag flag);
 
   static Handle<Map> CopyForObserved(Handle<Map> map);
 
   static Handle<Map> CopyNormalized(Handle<Map> map,
                                     PropertyNormalizationMode mode,
                                     NormalizedMapSharingMode sharing);
 
-  inline void AppendDescriptor(Descriptor* desc,
-                               const DescriptorArray::WhitenessWitness&);
+  inline void AppendDescriptor(Descriptor* desc);
 
   // Returns a copy of the map, with all transitions dropped from the
   // instance descriptors.
   static Handle<Map> Copy(Handle<Map> map);
   static Handle<Map> Create(Handle<JSFunction> constructor,
                             int extra_inobject_properties);
 
   // Returns the next free property index (only valid for FAST MODE).
   int NextFreePropertyIndex();
 
@@ skipping 4561 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_