Move DescriptorArray into the map

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 2438 matching lines @@
 #endif
   DECLARE_VERIFIER(FixedDoubleArray)
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(FixedDoubleArray);
 };
 
 
 // DescriptorArrays are fixed arrays used to hold instance descriptors.
 // The format of the these objects is:
-//   [0]: Either Smi(0) if uninitialized, or a pointer to small fixed array:
+//   [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
-//   [1]: first key
-//   [length() - kDescriptorSize]: last key
+//   [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.
@@ skipping 2327 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 transition_index, Map* target);
   inline Map* GetTransition(int transition_index);
   MUST_USE_RESULT inline MaybeObject* AddTransition(String* key,
                                                     Map* target,
                                                     SimpleTransitionFlag flag);
@@ skipping 27 matching lines @@
 
   // [prototype]: implicit prototype object.
   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);
-  static void SetDescriptors(Handle<Map> map,
-                             Handle<DescriptorArray> descriptors);
-  MUST_USE_RESULT inline MaybeObject* InitializeDescriptors(
-      DescriptorArray* descriptors);
+  DECL_ACCESSORS(instance_descriptors, DescriptorArray)
+  inline void 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
   // back pointer will be moved into the prototype transitions array if
   // required.
   inline Object* GetBackPointer();
   inline void SetBackPointer(Object* value,
@@ skipping 241 matching lines @@
   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
   // indirection.
   static const int kTransitionsOrBackPointerOffset =
       kConstructorOffset + kPointerSize;
+  static const int kDescriptorsOffset =
+      kTransitionsOrBackPointerOffset + kPointerSize;
   static const int kCodeCacheOffset =
-      kTransitionsOrBackPointerOffset + kPointerSize;
+      kDescriptorsOffset + kPointerSize;
   static const int kBitField3Offset = kCodeCacheOffset + kPointerSize;
-  static const int kPadStart = kBitField3Offset + kPointerSize;
-  static const int kSize = MAP_POINTER_ALIGN(kPadStart);
+  static const int kSize = kBitField3Offset + kPointerSize;
 
   // Layout of pointer fields. Heap iteration code relies on them
   // being continuously allocated.
   static const int kPointerFieldsBeginOffset = Map::kPrototypeOffset;
   static const int kPointerFieldsEndOffset = kBitField3Offset + kPointerSize;
 
   // Byte offsets within kInstanceSizesOffset.
   static const int kInstanceSizeOffset = kInstanceSizesOffset + 0;
   static const int kInObjectPropertiesByte = 1;
   static const int kInObjectPropertiesOffset =
@@ skipping 3790 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_