[Draft] Stackless map transition tree traversal.

src/objects.cc

 // Copyright 2006-2009 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 5105 matching lines @@
         ASSERT(target->prototype() == this ||
                target->prototype() == real_prototype);
         // Getter prototype() is read-only, set_prototype() has side effects.
         *RawField(target, Map::kPrototypeOffset) = real_prototype;
       }
     }
   }
 }
 
 
+void Map::TraverseTransitionTree() {
+  Map* current = this;
+  while (current != Heap::meta_map()) {
+    DescriptorArray* d = reinterpret_cast<DescriptorArray*>(
+        *RawField(current, Map::kInstanceDescriptorsOffset));
+    if (d == Heap::empty_descriptor_array()) {
+      Map* prev = current->map();
+      current->set_map(Heap::meta_map());
+      current->Print();
+      current = prev;
+      continue;
+    }
+    FixedArray* contents = reinterpret_cast<FixedArray*>(
+        d->get(DescriptorArray::kContentArrayIndex));
+    Object** map_or_index_field = RawField(contents, HeapObject::kMapOffset);
+    Object* map_or_index = *map_or_index_field;
+    ASSERT(map_or_index->IsSmi() || map_or_index == Heap::fixed_array_map());
+    bool map_done = true;
+    for (int i = map_or_index->IsSmi() ? Smi::cast(map_or_index)->value() : 0;
+         i < contents->length();
+         i += 2) {
+      PropertyDetails details(Smi::cast(contents->get(i + 1)));
+      if (details.IsTransition()) {
+        Map* next = Map::cast(contents->get(i));
+        next->set_map(current);
+        *map_or_index_field = Smi::FromInt(i + 2);
+        current = next;
+        map_done = false;
+        break;
+      }
+    }
+    if (!map_done) continue;
+    *map_or_index_field = Heap::fixed_array_map();
+    Map* prev = current->map();
+    current->set_map(Heap::meta_map());
+    current->Print();
+    current = prev;
+  }
+}
+
+
 void JSFunction::JSFunctionIterateBody(int object_size, ObjectVisitor* v) {
   // Iterate over all fields in the body but take care in dealing with
   // the code entry.
   IteratePointers(v, kPropertiesOffset, kCodeEntryOffset);
   v->VisitCodeEntry(this->address() + kCodeEntryOffset);
   IteratePointers(v, kCodeEntryOffset + kPointerSize, object_size);
 }
 
 
 Object* JSFunction::SetInstancePrototype(Object* value) {
@@ skipping 3753 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single beak point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif
 
 
 } }  // namespace v8::internal