Cache multiple ElementsKind map transition per map.

src/objects.h

 // Copyright 2011 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 162 matching lines @@
 static const int kElementsKindCount =
     LAST_ELEMENTS_KIND - FIRST_ELEMENTS_KIND + 1;
 
 // PropertyDetails captures type and attributes for a property.
 // They are used both in property dictionaries and instance descriptors.
 class PropertyDetails BASE_EMBEDDED {
  public:
   PropertyDetails(PropertyAttributes attributes,
                   PropertyType type,
                   int index = 0) {
-    ASSERT(type != ELEMENTS_TRANSITION);
     ASSERT(TypeField::is_valid(type));
     ASSERT(AttributesField::is_valid(attributes));
     ASSERT(StorageField::is_valid(index));
 
     value_ = TypeField::encode(type)
         | AttributesField::encode(attributes)
         | StorageField::encode(index);
 
     ASSERT(type == this->type());
     ASSERT(attributes == this->attributes());
     ASSERT(index == this->index());
   }
 
-  PropertyDetails(PropertyAttributes attributes,
-                  PropertyType type,
-                  ElementsKind elements_kind) {
-    ASSERT(type == ELEMENTS_TRANSITION);
-    ASSERT(TypeField::is_valid(type));
-    ASSERT(AttributesField::is_valid(attributes));
-    ASSERT(StorageField::is_valid(static_cast<int>(elements_kind)));
-
-    value_ = TypeField::encode(type)
-        | AttributesField::encode(attributes)
-        | StorageField::encode(static_cast<int>(elements_kind));
-
-    ASSERT(type == this->type());
-    ASSERT(attributes == this->attributes());
-    ASSERT(elements_kind == this->elements_kind());
-  }
-
   // Conversion for storing details as Object*.
   explicit inline PropertyDetails(Smi* smi);
   inline Smi* AsSmi();
 
   PropertyType type() { return TypeField::decode(value_); }
 
   bool IsTransition() {
     PropertyType t = type();
     ASSERT(t != INTERCEPTOR);
     return t == MAP_TRANSITION || t == CONSTANT_TRANSITION ||
         t == ELEMENTS_TRANSITION;
   }
 
   bool IsProperty() {
     return type() < FIRST_PHANTOM_PROPERTY_TYPE;
   }
 
   PropertyAttributes attributes() { return AttributesField::decode(value_); }
 
   int index() { return StorageField::decode(value_); }
 
-  ElementsKind elements_kind() {
-    ASSERT(type() == ELEMENTS_TRANSITION);
-    return static_cast<ElementsKind>(StorageField::decode(value_));
-  }
-
   inline PropertyDetails AsDeleted();
 
   static bool IsValidIndex(int index) {
     return StorageField::is_valid(index);
   }
 
   bool IsReadOnly() { return (attributes() & READ_ONLY) != 0; }
   bool IsDontDelete() { return (attributes() & DONT_DELETE) != 0; }
   bool IsDontEnum() { return (attributes() & DONT_ENUM) != 0; }
   bool IsDeleted() { return DeletedField::decode(value_) != 0;}
@@ skipping 3919 matching lines @@
   int IndexInCodeCache(Object* name, Code* code);
 
   // Removes a code object from the code cache at the given index.
   void RemoveFromCodeCache(String* name, Code* code, int index);
 
   // For every transition in this map, makes the transition's
   // target's prototype pointer point back to this map.
   // This is undone in MarkCompactCollector::ClearNonLiveTransitions().
   void CreateBackPointers();
 
+  void CreateOneBackPointer(Map* transition_target);
+
   // Set all map transitions from this map to dead maps to null.
   // Also, restore the original prototype on the targets of these
   // transitions, so that we do not process this map again while
   // following back pointers.
   void ClearNonLiveTransitions(Heap* heap, Object* real_prototype);
 
   // Computes a hash value for this map, to be used in HashTables and such.
   int Hash();
 
   // Compares this map to another to see if they describe equivalent objects.
@@ skipping 3305 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_