Sharing of descriptor arrays.

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 159 matching lines @@
   OMIT_CREATION
 };
 
 
 // Indicates whether transitions can be added to a source map or not.
 enum TransitionFlag {
   INSERT_TRANSITION,
   OMIT_TRANSITION
 };
 
+// Indicates whether we are only interested in the descriptors of a particular
+// map, or in all descriptors in the descriptor array.
+enum DescriptorFlag {
+  ALL_DESCRIPTORS,
+  OWN_DESCRIPTORS
+};
+
 
 // Instance size sentinel for objects of variable size.
 const int kVariableSizeSentinel = 0;
 
 const int kStubMajorKeyBits = 6;
 const int kStubMinorKeyBits = kBitsPerInt - kSmiTagSize - kStubMajorKeyBits;
 
 // All Maps have a field instance_type containing a InstanceType.
 // It describes the type of the instances.
 //
@@ skipping 2282 matching lines @@
   inline bool IsEmpty();
 
   // Returns the number of descriptors in the array.
   int number_of_descriptors() {
     ASSERT(length() >= kFirstIndex || 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; }
 
   bool HasEnumCache() {
     return !IsEmpty() && !get(kEnumCacheIndex)->IsSmi();
   }
 
+  void CopyEnumCacheFrom(DescriptorArray* array) {
+    set(kEnumCacheIndex, array->get(kEnumCacheIndex));
+  }
+
   Object* GetEnumCache() {
     ASSERT(HasEnumCache());
     FixedArray* bridge = FixedArray::cast(get(kEnumCacheIndex));
     return bridge->get(kEnumCacheBridgeCacheIndex);
   }
 
   Object** GetEnumCacheSlot() {
     ASSERT(HasEnumCache());
     return HeapObject::RawField(reinterpret_cast<HeapObject*>(this),
                                 kEnumCacheOffset);
@@ skipping 34 matching lines @@
                      const WhitenessWitness&,
                      int number_of_set_descriptors);
 
   // Transfer a complete descriptor from the src descriptor array to this
   // descriptor array.
   void CopyFrom(int dst_index,
                 DescriptorArray* src,
                 int src_index,
                 const WhitenessWitness&);
 
+  MUST_USE_RESULT MaybeObject* CopyUpTo(int enumeration_index);
+
   // Sort the instance descriptors by the hash codes of their keys.
   void Sort();
-  inline void SwapSortedKeys(int first, int second);
 
   // Search the instance descriptors for given name.
-  INLINE(int Search(String* name));
+  INLINE(int Search(String* name, int number_of_own_descriptors));
 
   // As the above, but uses DescriptorLookupCache and updates it when
   // necessary.
-  INLINE(int SearchWithCache(String* name));
-
-  // Tells whether the name is present int the array.
-  bool Contains(String* name) { return kNotFound != Search(name); }
+  INLINE(int SearchWithCache(String* name, Map* map));
 
   // Allocates a DescriptorArray, but returns the singleton
   // empty descriptor array object if number_of_descriptors is 0.
   MUST_USE_RESULT static MaybeObject* Allocate(int number_of_descriptors);
 
   // Casting.
   static inline DescriptorArray* cast(Object* obj);
 
   // Constant for denoting key was not found.
   static const int kNotFound = -1;
@@ skipping 22 matching lines @@
 #ifdef OBJECT_PRINT
   // Print all the descriptors.
   inline void PrintDescriptors() {
     PrintDescriptors(stdout);
   }
   void PrintDescriptors(FILE* out);
 #endif
 
 #ifdef DEBUG
   // Is the descriptor array sorted and without duplicates?
-  bool IsSortedNoDuplicates();
+  bool IsSortedNoDuplicates(int valid_descriptors = -1);
 
   // Is the descriptor array consistent with the back pointers in targets?
   bool IsConsistentWithBackPointers(Map* current_map);
 
   // Are two DescriptorArrays equal?
   bool IsEqualTo(DescriptorArray* other);
 #endif
 
   // The maximum number of descriptors we want in a descriptor array (should
   // fit in a page).
@@ skipping 32 matching lines @@
            (descriptor_number * kDescriptorSize) +
            kDescriptorDetails;
   }
 
   static int ToValueIndex(int descriptor_number) {
     return kFirstIndex +
            (descriptor_number * kDescriptorSize) +
            kDescriptorValue;
   }
 
-  // Swap operation on FixedArray without using write barriers.
-  static inline void NoIncrementalWriteBarrierSwap(
-      FixedArray* array, int first, int second);
-
   // Swap first and second descriptor.
-  inline void NoIncrementalWriteBarrierSwapDescriptors(
-      int first, int second);
+  inline void SwapSortedKeys(int first, int second);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(DescriptorArray);
 };
 
 
-template<typename T>
-inline int LinearSearch(T* array, String* name, int len);
+enum SearchMode { ALL_ENTRIES, VALID_ENTRIES };
+
+template<SearchMode search_mode, typename T>
+inline int LinearSearch(T* array, String* name, int len, int valid_entries);
 
 
-template<typename T>
-inline int Search(T* array, String* name);
+template<SearchMode search_mode, typename T>
+inline int Search(T* array, String* name, int valid_entries = 0);
 
 
 // HashTable is a subclass of FixedArray that implements a hash table
 // that uses open addressing and quadratic probing.
 //
 // In order for the quadratic probing to work, elements that have not
 // yet been used and elements that have been deleted are
 // distinguished.  Probing continues when deleted elements are
 // encountered and stops when unused elements are encountered.
 //
@@ skipping 1985 matching lines @@
 
   // Bit field 3.
   inline int bit_field3();
   inline void set_bit_field3(int value);
 
   class EnumLengthBits:             public BitField<int,   0, 11> {};
   class NumberOfOwnDescriptorsBits: public BitField<int,  11, 11> {};
   class IsShared:                   public BitField<bool, 22,  1> {};
   class FunctionWithPrototype:      public BitField<bool, 23,  1> {};
   class DictionaryMap:              public BitField<bool, 24,  1> {};
+  class OwnsDescriptors:            public BitField<bool, 25,  1> {};
 
   // Tells whether the object in the prototype property will be used
   // for instances created from this function.  If the prototype
   // property is set to a value that is not a JSObject, the prototype
   // property will not be used to create instances of the function.
   // See ECMA-262, 13.2.2.
   inline void set_non_instance_prototype(bool value);
   inline bool has_non_instance_prototype();
 
   // Tells whether function has special prototype property. If not, prototype
@@ skipping 100 matching lines @@
   }
 
   inline bool has_slow_elements_kind() {
     return elements_kind() == DICTIONARY_ELEMENTS
         || elements_kind() == NON_STRICT_ARGUMENTS_ELEMENTS;
   }
 
   static bool IsValidElementsTransition(ElementsKind from_kind,
                                         ElementsKind to_kind);
 
+  bool StoresOwnDescriptors() { return HasTransitionArray(); }
   inline bool HasTransitionArray();
   inline bool HasElementsTransition();
   inline Map* elements_transition_map();
   MUST_USE_RESULT inline MaybeObject* set_elements_transition_map(
       Map* transitioned_map);
   inline void SetTransition(int index, Map* target);
   MUST_USE_RESULT inline MaybeObject* AddTransition(String* key, Map* target);
   DECL_ACCESSORS(transitions, TransitionArray)
   inline void ClearTransitions(Heap* heap,
                                WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
@@ skipping 26 matching lines @@
   DECL_ACCESSORS(prototype, Object)
 
   // [constructor]: points back to the function responsible for this map.
   DECL_ACCESSORS(constructor, Object)
 
   inline JSFunction* unchecked_constructor();
 
   // [instance descriptors]: describes the object.
   inline DescriptorArray* instance_descriptors();
   MUST_USE_RESULT inline MaybeObject* SetDescriptors(
-      DescriptorArray* descriptors,
-      WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
+      DescriptorArray* descriptors);
   static void SetDescriptors(Handle<Map> map,
                              Handle<DescriptorArray> descriptors);
   MUST_USE_RESULT inline MaybeObject* InitializeDescriptors(
       DescriptorArray* descriptors);
 
   // [stub cache]: contains stubs compiled for this map.
   DECL_ACCESSORS(code_cache, Object)
 
   // [back pointer]: points back to the parent map from which a transition
   // leads to this map. The field overlaps with prototype transitions and the
@@ skipping 60 matching lines @@
     int number_of_own_descriptors = NumberOfOwnDescriptors();
     ASSERT(number_of_own_descriptors > 0);
     return number_of_own_descriptors - 1;
   }
 
   int NumberOfOwnDescriptors() {
     return NumberOfOwnDescriptorsBits::decode(bit_field3());
   }
 
   void SetNumberOfOwnDescriptors(int number) {
+    ASSERT(number <= instance_descriptors()->number_of_descriptors());
     set_bit_field3(NumberOfOwnDescriptorsBits::update(bit_field3(), number));
   }
 
+  inline JSGlobalPropertyCell* RetrieveDescriptorsPointer();
+
   int EnumLength() {
     return EnumLengthBits::decode(bit_field3());
   }
 
-  void SetEnumLength(int index) {
-    set_bit_field3(EnumLengthBits::update(bit_field3(), index));
+  void SetEnumLength(int length) {
+    if (length != kInvalidEnumCache) {
+      ASSERT(length >= 0);
+      ASSERT(length == 0 || instance_descriptors()->HasEnumCache());
+      ASSERT(length <= NumberOfOwnDescriptors());
+    }
+    set_bit_field3(EnumLengthBits::update(bit_field3(), length));
   }
 
+
+  inline bool OwnsDescriptors();
+  inline void SetOwnsDescriptors(bool is_shared);
+
   MUST_USE_RESULT MaybeObject* RawCopy(int instance_size);
   MUST_USE_RESULT MaybeObject* CopyWithPreallocatedFieldDescriptors();
   MUST_USE_RESULT MaybeObject* CopyDropDescriptors();
   MUST_USE_RESULT MaybeObject* CopyReplaceDescriptors(
       DescriptorArray* descriptors,
       String* name,
       TransitionFlag flag);
+  MUST_USE_RESULT MaybeObject* ShareDescriptor(Descriptor* descriptor);
   MUST_USE_RESULT MaybeObject* CopyAddDescriptor(Descriptor* descriptor,
                                                  TransitionFlag flag);
   MUST_USE_RESULT MaybeObject* CopyInsertDescriptor(Descriptor* descriptor,
                                                     TransitionFlag flag);
   MUST_USE_RESULT MaybeObject* CopyReplaceDescriptor(Descriptor* descriptor,
                                                      int index,
                                                      TransitionFlag flag);
   MUST_USE_RESULT MaybeObject* CopyAsElementsKind(ElementsKind kind,
                                                   TransitionFlag flag);
 
   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();
 
   // Returns the property index for name (only valid for FAST MODE).
   int PropertyIndexFor(String* name);
 
   // Returns the next free property index (only valid for FAST MODE).
   int NextFreePropertyIndex();
 
   // Returns the number of properties described in instance_descriptors
   // filtering out properties with the specified attributes.
-  int NumberOfDescribedProperties(PropertyAttributes filter = NONE);
+  int NumberOfDescribedProperties(DescriptorFlag which = OWN_DESCRIPTORS,
+                                  PropertyAttributes filter = NONE);
 
   // Casting.
   static inline Map* cast(Object* obj);
 
   // Locate an accessor in the instance descriptor.
   AccessorDescriptor* FindAccessor(String* name);
 
   // Code cache operations.
 
   // Clears the code cache.
@@ skipping 83 matching lines @@
   // and the values are the maps the are transitioned to.
   static const int kMaxCachedPrototypeTransitions = 256;
 
   Map* GetPrototypeTransition(Object* prototype);
 
   MUST_USE_RESULT MaybeObject* PutPrototypeTransition(Object* prototype,
                                                       Map* map);
 
   static const int kMaxPreAllocatedPropertyFields = 255;
 
-  // Constant for denoting that the Enum Cache field was not yet used.
+  // Constant for denoting that the enum cache is not yet initialized.
   static const int kInvalidEnumCache = EnumLengthBits::kMax;
 
   // Layout description.
   static const int kInstanceSizesOffset = HeapObject::kHeaderSize;
   static const int kInstanceAttributesOffset = kInstanceSizesOffset + kIntSize;
   static const int kPrototypeOffset = kInstanceAttributesOffset + kIntSize;
   static const int kConstructorOffset = kPrototypeOffset + kPointerSize;
   // Storage for the transition array is overloaded to directly contain a back
   // pointer if unused. When the map has transitions, the back pointer is
   // transferred to the transition array and accessed through an extra
@@ skipping 3868 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_