Moving prototype transitions into the header of the transition array.

src/transitions.h

Index: src/transitions.h
diff --git a/src/transitions.h b/src/transitions.h
index 5abdf99f8c3cdbf72bb5650f6691a5834ff06f39..ba7b4dfbf7233c5441f333470dc85a1af68fe665 100644
--- a/src/transitions.h
+++ b/src/transitions.h
@@ -52,6 +52,12 @@ class TransitionArray: public FixedArray {
       WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
   inline void ClearElementsTransition();
   inline bool HasElementsTransition();
+  inline FixedArray* prototype_transitions();
+  inline void set_prototype_transitions(
+      FixedArray* prototype_transitions,
+      WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
+  inline HeapObject* unchecked_prototype_transitions();
+  inline bool HasPrototypeTransitions();
   // Accessors for fetching instance transition at transition number.
   inline String* GetKey(int transition_number);
   inline Object** GetKeySlot(int transition_number);
@@ -62,6 +68,8 @@ class TransitionArray: public FixedArray {
   inline Map* GetTargetMap(int transition_number);
   inline PropertyDetails GetTargetDetails(int transition_number);
   inline Object** GetElementsSlot();
+  inline Object** GetPrototypeTransitionsSlot();

[Michael Starzinger, 2012/07/06 13:53:18]

Can we group these accessors somehow, this is becoming a rather large block.

[Toon Verwaest, 2012/07/09 12:45:27]

Done.

+  bool TransitionsTo(Object* target);
 
   // Returns the number of transitions in the array.
   int number_of_transitions() {
@@ -99,11 +107,14 @@ class TransitionArray: public FixedArray {
   static const int kNotFound = -1;
 
   static const int kElementsTransitionIndex = 0;
-  static const int kFirstIndex = 1;
+  static const int kPrototypeTransitionsIndex = 1;
+  static const int kFirstIndex = 2;
 
   // Layout transition array header.
   static const int kElementsTransitionOffset = FixedArray::kHeaderSize;
-  static const int kFirstOffset = kElementsTransitionOffset + kPointerSize;
+  static const int kPrototypeTransitionsOffset = kElementsTransitionOffset +

[Michael Starzinger, 2012/07/06 13:53:18]

Better break that after the "=", to be consistent with objects.h

+                                                 kPointerSize;
+  static const int kFirstOffset = kPrototypeTransitionsOffset + kPointerSize;
 
   // Layout of map transition.
   static const int kTransitionKey = 0;