| // 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" |
| #include "src/isolate.h" |
| #include "src/objects.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| |
| // TransitionArrays are fixed arrays used to hold map transitions for property, |
| // constant, and element changes. They can either be simple transition arrays |
| // that store a single property transition, or a full transition array that has |
| // prototype transitions and multiple property transitons. The details related |
| // to property transitions are accessed in the descriptor array of the target |
| // map. In the case of a simple transition, the key is also read from the |
| // descriptor array of the target map. |
| // |
| // The simple format of the these objects is: |
| // [0] Undefined or back pointer map |
| // [1] Single transition |
| // |
| // The full format is: |
| // [0] Undefined or back pointer map |
| // [1] Smi(0) or fixed array of prototype transitions |
| // [2] First transition |
| // [length() - kTransitionSize] Last transition |
| class TransitionArray: public FixedArray { |
| public: |
| // Accessors for fetching instance transition at transition number. |
| inline Name* GetKey(int transition_number); |
| inline void SetKey(int transition_number, Name* value); |
| inline Object** GetKeySlot(int transition_number); |
| int GetSortedKeyIndex(int transition_number) { return transition_number; } |
| |
| Name* GetSortedKey(int transition_number) { |
| return GetKey(transition_number); |
| } |
| |
| inline Map* GetTarget(int transition_number); |
| inline void SetTarget(int transition_number, Map* target); |
| |
| inline PropertyDetails GetTargetDetails(int transition_number); |
| |
| inline bool HasElementsTransition(); |
| |
| inline Object* back_pointer_storage(); |
| inline void set_back_pointer_storage( |
| Object* back_pointer, |
| WriteBarrierMode mode = UPDATE_WRITE_BARRIER); |
| |
| inline FixedArray* GetPrototypeTransitions(); |
| inline void SetPrototypeTransitions( |
| FixedArray* prototype_transitions, |
| WriteBarrierMode mode = UPDATE_WRITE_BARRIER); |
| inline Object** GetPrototypeTransitionsSlot(); |
| inline bool HasPrototypeTransitions(); |
| |
| // Returns the number of transitions in the array. |
| int number_of_transitions() { |
| if (IsSimpleTransition()) return 1; |
| int len = length(); |
| return len <= kFirstIndex ? 0 : (len - kFirstIndex) / kTransitionSize; |
| } |
| |
| inline int number_of_entries() { return number_of_transitions(); } |
| |
| // Creates a FullTransitionArray from a SimpleTransitionArray in |
| // containing_map. |
| static Handle<TransitionArray> ExtendToFullTransitionArray( |
| Handle<Map> containing_map); |
| |
| // Create a transition array, copying from the owning map if it already has |
| // one, otherwise creating a new one according to flag. |
| // TODO(verwaest): This should not cause an existing transition to be |
| // overwritten. |
| static Handle<TransitionArray> CopyInsert(Handle<Map> map, |
| Handle<Name> name, |
| Handle<Map> target, |
| SimpleTransitionFlag flag); |
| |
| // Search a transition for a given property name. |
| inline int Search(Name* name); |
| |
| // Allocates a TransitionArray. |
| static Handle<TransitionArray> Allocate( |
| Isolate* isolate, int number_of_transitions); |
| |
| bool IsSimpleTransition() { |
| return length() == kSimpleTransitionSize && |
| get(kSimpleTransitionTarget)->IsHeapObject() && |
| // The IntrusivePrototypeTransitionIterator may have set the map of the |
| // prototype transitions array to a smi. In that case, there are |
| // prototype transitions, hence this transition array is a full |
| // transition array. |
| HeapObject::cast(get(kSimpleTransitionTarget))->map()->IsMap() && |
| get(kSimpleTransitionTarget)->IsMap(); |
| } |
| |
| bool IsFullTransitionArray() { |
| return length() > kFirstIndex || |
| (length() == kFirstIndex && !IsSimpleTransition()); |
| } |
| |
| // Casting. |
| static inline TransitionArray* cast(Object* obj); |
| |
| // Constant for denoting key was not found. |
| static const int kNotFound = -1; |
| |
| static const int kBackPointerStorageIndex = 0; |
| |
| // Layout for full transition arrays. |
| static const int kPrototypeTransitionsIndex = 1; |
| static const int kFirstIndex = 2; |
| |
| // Layout for simple transition arrays. |
| static const int kSimpleTransitionTarget = 1; |
| static const int kSimpleTransitionSize = 2; |
| static const int kSimpleTransitionIndex = 0; |
| STATIC_ASSERT(kSimpleTransitionIndex != kNotFound); |
| |
| static const int kBackPointerStorageOffset = FixedArray::kHeaderSize; |
| |
| // Layout for the full transition array header. |
| static const int kPrototypeTransitionsOffset = kBackPointerStorageOffset + |
| kPointerSize; |
| |
| // Layout of map transition entries in full transition arrays. |
| static const int kTransitionKey = 0; |
| static const int kTransitionTarget = 1; |
| static const int kTransitionSize = 2; |
| |
| #ifdef OBJECT_PRINT |
| // Print all the transitions. |
| void PrintTransitions(OStream& os); // NOLINT |
| #endif |
| |
| #ifdef DEBUG |
| bool IsSortedNoDuplicates(int valid_entries = -1); |
| bool IsConsistentWithBackPointers(Map* current_map); |
| bool IsEqualTo(TransitionArray* other); |
| #endif |
| |
| // The maximum number of transitions we want in a transition array (should |
| // fit in a page). |
| static const int kMaxNumberOfTransitions = 1024 + 512; |
| |
| private: |
| // Conversion from transition number to array indices. |
| static int ToKeyIndex(int transition_number) { |
| return kFirstIndex + |
| (transition_number * kTransitionSize) + |
| kTransitionKey; |
| } |
| |
| static int ToTargetIndex(int transition_number) { |
| return kFirstIndex + |
| (transition_number * kTransitionSize) + |
| kTransitionTarget; |
| } |
| |
| static Handle<TransitionArray> AllocateSimple( |
| Isolate* isolate, Handle<Map> target); |
| |
| // Allocate a new transition array with a single entry. |
| static Handle<TransitionArray> NewWith(Handle<Map> map, |
| Handle<Name> name, |
| Handle<Map> target, |
| SimpleTransitionFlag flag); |
| |
| inline void NoIncrementalWriteBarrierSet(int transition_number, |
| Name* key, |
| Map* target); |
| |
| // Copy a single transition from the origin array. |
| inline void NoIncrementalWriteBarrierCopyFrom(TransitionArray* origin, |
| int origin_transition, |
| int target_transition); |
| |
| DISALLOW_IMPLICIT_CONSTRUCTORS(TransitionArray); |
| }; |
| |
| |
| } } // namespace v8::internal |
| |
| #endif // V8_TRANSITIONS_H_ |