Introduce instance type for transition arrays.

src/transitions.cc

 // 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.
 
 #include "src/transitions.h"
 
 #include "src/objects-inl.h"
 #include "src/transitions-inl.h"
 #include "src/utils.h"
 
@@ skipping 373 matching lines @@
   if (t->length() <= kFirstIndex) return 0;
   return (t->length() - kFirstIndex) / kTransitionSize;
 }
 
 
 // Private static helper functions.
 
 Handle<TransitionArray> TransitionArray::Allocate(Isolate* isolate,
                                                   int number_of_transitions,
                                                   int slack) {
-  Handle<FixedArray> array = isolate->factory()->NewFixedArray(
-      LengthFor(number_of_transitions + slack), TENURED);
+  Handle<FixedArray> array = isolate->factory()->NewTransitionArray(
+      LengthFor(number_of_transitions + slack));
+  array->set(kNextLinkIndex, isolate->heap()->undefined_value());
   array->set(kPrototypeTransitionsIndex, Smi::FromInt(0));
   array->set(kTransitionLengthIndex, Smi::FromInt(number_of_transitions));
   return Handle<TransitionArray>::cast(array);
 }
 
 
-static void ZapTransitionArray(TransitionArray* transitions) {
-  MemsetPointer(transitions->data_start(),
+// static
+void TransitionArray::ZapTransitionArray(TransitionArray* transitions) {
+  // Do not zap the next link that is used by GC.
+  STATIC_ASSERT(kNextLinkIndex + 1 == kPrototypeTransitionsIndex);
+  MemsetPointer(transitions->data_start() + kPrototypeTransitionsIndex,
                 transitions->GetHeap()->the_hole_value(),
-                transitions->length());
+                transitions->length() - kPrototypeTransitionsIndex);
+  transitions->SetNumberOfTransitions(0);
 }
 
 
 void TransitionArray::ReplaceTransitions(Handle<Map> map,
                                          Object* new_transitions) {
   Object* raw_transitions = map->raw_transitions();
   if (IsFullTransitionArray(raw_transitions)) {
     TransitionArray* old_transitions = TransitionArray::cast(raw_transitions);
 #ifdef DEBUG
     CheckNewTransitionsAreConsistent(map, old_transitions, new_transitions);
@@ skipping 124 matching lines @@
                             PropertyAttributes attributes,
                             int* out_insertion_index) {
   int transition = SearchName(name, out_insertion_index);
   if (transition == kNotFound) {
     return kNotFound;
   }
   return SearchDetails(transition, kind, attributes, out_insertion_index);
 }
 }  // namespace internal
 }  // namespace v8