Introduce instance type for transition arrays.

src/transitions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_TRANSITIONS_H_
 #define V8_TRANSITIONS_H_
 
 #include "src/checks.h"
 #include "src/elements-kind.h"
 #include "src/heap/heap.h"
@@ skipping 147 matching lines @@
 
   // Returns the number of transitions in the array.
   static int NumberOfTransitions(Object* raw_transitions);
   // Required for templatized Search interface.
   inline int number_of_entries() { return number_of_transitions(); }
 
   inline void SetNumberOfTransitions(int number_of_transitions);
 
   static int Capacity(Object* raw_transitions);
 
-  // Casting.

[Jakob Kummerow, 2015/11/27 14:54:07]

Whaaaaat?! With this comment gone, how am I supposed to know that "cast()" is
for casting? In fact, please extend the comment to say "Returns the input
object, casted to TransitionArray".

Just kidding. It's Friday.

-  static inline TransitionArray* cast(Object* obj);
+  inline static TransitionArray* cast(Object* object);
+
+  // This field should be used only by GC.
+  inline void set_next_link(Object* next, WriteBarrierMode mode);
+  inline Object* next_link();
 
   static const int kTransitionSize = 2;
   static const int kProtoTransitionHeaderSize = 1;
 
 #if defined(DEBUG) || defined(OBJECT_PRINT)
   // For our gdb macros, we should perhaps change these in the future.
   void Print();
 
   // Print all the transitions.
   static void PrintTransitions(std::ostream& os, Object* transitions,
                                bool print_header = true);  // NOLINT
 #endif
 
+#ifdef OBJECT_PRINT
+  void TransitionArrayPrint(std::ostream& os);  // NOLINT
+#endif
+
+#ifdef VERIFY_HEAP
+  void TransitionArrayVerify();
+#endif
+
 #ifdef DEBUG
   bool IsSortedNoDuplicates(int valid_entries = -1);
   static bool IsSortedNoDuplicates(Map* map);
   static bool IsConsistentWithBackPointers(Map* map);
 
   // Returns true for a non-property transitions like elements kind, observed
   // or frozen transitions.
   static inline bool IsSpecialTransition(Name* name);
 #endif
 
   // Constant for denoting key was not found.
   static const int kNotFound = -1;
 
   // The maximum number of transitions we want in a transition array (should
   // fit in a page).
   static const int kMaxNumberOfTransitions = 1024 + 512;
 
  private:
   // Layout for full transition arrays.
-  static const int kPrototypeTransitionsIndex = 0;
-  static const int kTransitionLengthIndex = 1;
-  static const int kFirstIndex = 2;
+  static const int kNextLinkIndex = 0;
+  static const int kPrototypeTransitionsIndex = 1;
+  static const int kTransitionLengthIndex = 2;
+  static const int kFirstIndex = 3;
 
   // Layout of map transition entries in full transition arrays.
   static const int kTransitionKey = 0;
   static const int kTransitionTarget = 1;
   STATIC_ASSERT(kTransitionSize == 2);
 
   static const int kProtoTransitionNumberOfEntriesOffset = 0;
   STATIC_ASSERT(kProtoTransitionHeaderSize == 1);
 
   // Conversion from transition number to array indices.
@@ skipping 82 matching lines @@
                                    PropertyKind kind2,
                                    PropertyAttributes attributes2);
 
   inline void Set(int transition_number, Name* key, Map* target);
 
 #ifdef DEBUG
   static void CheckNewTransitionsAreConsistent(Handle<Map> map,
                                                TransitionArray* old_transitions,
                                                Object* transitions);
 #endif
+  static void ZapTransitionArray(TransitionArray* transitions);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(TransitionArray);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TRANSITIONS_H_