src/heap/objects-visiting.cc - platform/external/v8 - Git at Google

 // Copyright 2011 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/v8.h"

 #include "src/heap/objects-visiting.h"

 namespace v8 {
 namespace internal {


 StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
     int instance_type, int instance_size, bool has_unboxed_fields) {
   if (instance_type < FIRST_NONSTRING_TYPE) {
     switch (instance_type & kStringRepresentationMask) {
       case kSeqStringTag:
         if ((instance_type & kStringEncodingMask) == kOneByteStringTag) {
           return kVisitSeqOneByteString;
         } else {
           return kVisitSeqTwoByteString;
         }

       case kConsStringTag:
         if (IsShortcutCandidate(instance_type)) {
           return kVisitShortcutCandidate;
         } else {
           return kVisitConsString;
         }

       case kSlicedStringTag:
         return kVisitSlicedString;

       case kExternalStringTag:
         return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
                                    instance_size, has_unboxed_fields);
     }
     UNREACHABLE();
   }

   switch (instance_type) {
     case BYTE_ARRAY_TYPE:
       return kVisitByteArray;

     case FREE_SPACE_TYPE:
       return kVisitFreeSpace;

     case FIXED_ARRAY_TYPE:
       return kVisitFixedArray;

     case FIXED_DOUBLE_ARRAY_TYPE:
       return kVisitFixedDoubleArray;

     case CONSTANT_POOL_ARRAY_TYPE:
       return kVisitConstantPoolArray;

     case ODDBALL_TYPE:
       return kVisitOddball;

     case MAP_TYPE:
       return kVisitMap;

     case CODE_TYPE:
       return kVisitCode;

     case CELL_TYPE:
       return kVisitCell;

     case PROPERTY_CELL_TYPE:
       return kVisitPropertyCell;

     case WEAK_CELL_TYPE:
       return kVisitWeakCell;

     case JS_SET_TYPE:
       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
                                  JSSet::kSize, has_unboxed_fields);

     case JS_MAP_TYPE:
       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
                                  JSMap::kSize, has_unboxed_fields);

     case JS_WEAK_MAP_TYPE:
     case JS_WEAK_SET_TYPE:
       return kVisitJSWeakCollection;

     case JS_REGEXP_TYPE:
       return kVisitJSRegExp;

     case SHARED_FUNCTION_INFO_TYPE:
       return kVisitSharedFunctionInfo;

     case JS_PROXY_TYPE:
       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
                                  JSProxy::kSize, has_unboxed_fields);

     case JS_FUNCTION_PROXY_TYPE:
       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
                                  JSFunctionProxy::kSize, has_unboxed_fields);

     case FOREIGN_TYPE:
       return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
                                  Foreign::kSize, has_unboxed_fields);

     case SYMBOL_TYPE:
       return kVisitSymbol;

     case FILLER_TYPE:
       return kVisitDataObjectGeneric;

     case JS_ARRAY_BUFFER_TYPE:
       return kVisitJSArrayBuffer;

     case JS_TYPED_ARRAY_TYPE:
       return kVisitJSTypedArray;

     case JS_DATA_VIEW_TYPE:
       return kVisitJSDataView;

     case JS_OBJECT_TYPE:
     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
     case JS_GENERATOR_OBJECT_TYPE:
     case JS_MODULE_TYPE:
     case JS_VALUE_TYPE:
     case JS_DATE_TYPE:
     case JS_ARRAY_TYPE:
     case JS_GLOBAL_PROXY_TYPE:
     case JS_GLOBAL_OBJECT_TYPE:
     case JS_BUILTINS_OBJECT_TYPE:
     case JS_MESSAGE_OBJECT_TYPE:
     case JS_SET_ITERATOR_TYPE:
     case JS_MAP_ITERATOR_TYPE:
       return GetVisitorIdForSize(kVisitJSObject, kVisitJSObjectGeneric,
                                  instance_size, has_unboxed_fields);

     case JS_FUNCTION_TYPE:
       return kVisitJSFunction;

     case HEAP_NUMBER_TYPE:
     case MUTABLE_HEAP_NUMBER_TYPE:
 #define EXTERNAL_ARRAY_CASE(Type, type, TYPE, ctype, size) \
   case EXTERNAL_##TYPE##_ARRAY_TYPE:

       TYPED_ARRAYS(EXTERNAL_ARRAY_CASE)
       return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
                                  instance_size, has_unboxed_fields);
 #undef EXTERNAL_ARRAY_CASE

     case FIXED_UINT8_ARRAY_TYPE:
     case FIXED_INT8_ARRAY_TYPE:
     case FIXED_UINT16_ARRAY_TYPE:
     case FIXED_INT16_ARRAY_TYPE:
     case FIXED_UINT32_ARRAY_TYPE:
     case FIXED_INT32_ARRAY_TYPE:
     case FIXED_FLOAT32_ARRAY_TYPE:
     case FIXED_UINT8_CLAMPED_ARRAY_TYPE:
       return kVisitFixedTypedArray;

     case FIXED_FLOAT64_ARRAY_TYPE:
       return kVisitFixedFloat64Array;

 #define MAKE_STRUCT_CASE(NAME, Name, name) case NAME##_TYPE:
       STRUCT_LIST(MAKE_STRUCT_CASE)
 #undef MAKE_STRUCT_CASE
       if (instance_type == ALLOCATION_SITE_TYPE) {
         return kVisitAllocationSite;
       }

       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
                                  instance_size, has_unboxed_fields);

     default:
       UNREACHABLE();
       return kVisitorIdCount;
   }
 }


 // We don't record weak slots during marking or scavenges. Instead we do it
 // once when we complete mark-compact cycle.  Note that write barrier has no
 // effect if we are already in the middle of compacting mark-sweep cycle and we
 // have to record slots manually.
 static bool MustRecordSlots(Heap* heap) {
   return heap->gc_state() == Heap::MARK_COMPACT &&
          heap->mark_compact_collector()->is_compacting();
 }


 template <class T>
 struct WeakListVisitor;


 template <class T>
 Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer) {
   Object* undefined = heap->undefined_value();
   Object* head = undefined;
   T* tail = NULL;
   MarkCompactCollector* collector = heap->mark_compact_collector();
   bool record_slots = MustRecordSlots(heap);
   while (list != undefined) {
     // Check whether to keep the candidate in the list.
     T* candidate = reinterpret_cast<T*>(list);
     Object* retained = retainer->RetainAs(list);
     if (retained != NULL) {
       if (head == undefined) {
         // First element in the list.
         head = retained;
       } else {
         // Subsequent elements in the list.
         DCHECK(tail != NULL);
         WeakListVisitor<T>::SetWeakNext(tail, retained);
         if (record_slots) {
           Object** next_slot =
               HeapObject::RawField(tail, WeakListVisitor<T>::WeakNextOffset());
           collector->RecordSlot(next_slot, next_slot, retained);
         }
       }
       // Retained object is new tail.
       DCHECK(!retained->IsUndefined());
       candidate = reinterpret_cast<T*>(retained);
       tail = candidate;


       // tail is a live object, visit it.
       WeakListVisitor<T>::VisitLiveObject(heap, tail, retainer);
     } else {
       WeakListVisitor<T>::VisitPhantomObject(heap, candidate);
     }

     // Move to next element in the list.
     list = WeakListVisitor<T>::WeakNext(candidate);
   }

   // Terminate the list if there is one or more elements.
   if (tail != NULL) {
     WeakListVisitor<T>::SetWeakNext(tail, undefined);
   }
   return head;
 }


 template <class T>
 static void ClearWeakList(Heap* heap, Object* list) {
   Object* undefined = heap->undefined_value();
   while (list != undefined) {
     T* candidate = reinterpret_cast<T*>(list);
     list = WeakListVisitor<T>::WeakNext(candidate);
     WeakListVisitor<T>::SetWeakNext(candidate, undefined);
   }
 }


 template <>
 struct WeakListVisitor<JSFunction> {
   static void SetWeakNext(JSFunction* function, Object* next) {
     function->set_next_function_link(next);
   }

   static Object* WeakNext(JSFunction* function) {
     return function->next_function_link();
   }

   static int WeakNextOffset() { return JSFunction::kNextFunctionLinkOffset; }

   static void VisitLiveObject(Heap*, JSFunction*, WeakObjectRetainer*) {}

   static void VisitPhantomObject(Heap*, JSFunction*) {}
 };


 template <>
 struct WeakListVisitor<Code> {
   static void SetWeakNext(Code* code, Object* next) {
     code->set_next_code_link(next);
   }

   static Object* WeakNext(Code* code) { return code->next_code_link(); }

   static int WeakNextOffset() { return Code::kNextCodeLinkOffset; }

   static void VisitLiveObject(Heap*, Code*, WeakObjectRetainer*) {}

   static void VisitPhantomObject(Heap*, Code*) {}
 };


 template <>
 struct WeakListVisitor<Context> {
   static void SetWeakNext(Context* context, Object* next) {
     context->set(Context::NEXT_CONTEXT_LINK, next, UPDATE_WRITE_BARRIER);
   }

   static Object* WeakNext(Context* context) {
     return context->get(Context::NEXT_CONTEXT_LINK);
   }

   static int WeakNextOffset() {
     return FixedArray::SizeFor(Context::NEXT_CONTEXT_LINK);
   }

   static void VisitLiveObject(Heap* heap, Context* context,
                               WeakObjectRetainer* retainer) {
     // Process the three weak lists linked off the context.
     DoWeakList<JSFunction>(heap, context, retainer,
                            Context::OPTIMIZED_FUNCTIONS_LIST);
     DoWeakList<Code>(heap, context, retainer, Context::OPTIMIZED_CODE_LIST);
     DoWeakList<Code>(heap, context, retainer, Context::DEOPTIMIZED_CODE_LIST);
   }

   template <class T>
   static void DoWeakList(Heap* heap, Context* context,
                          WeakObjectRetainer* retainer, int index) {
     // Visit the weak list, removing dead intermediate elements.
     Object* list_head = VisitWeakList<T>(heap, context->get(index), retainer);

     // Update the list head.
     context->set(index, list_head, UPDATE_WRITE_BARRIER);

     if (MustRecordSlots(heap)) {
       // Record the updated slot if necessary.
       Object** head_slot =
           HeapObject::RawField(context, FixedArray::SizeFor(index));
       heap->mark_compact_collector()->RecordSlot(head_slot, head_slot,
                                                  list_head);
     }
   }

   static void VisitPhantomObject(Heap* heap, Context* context) {
     ClearWeakList<JSFunction>(heap,
                               context->get(Context::OPTIMIZED_FUNCTIONS_LIST));
     ClearWeakList<Code>(heap, context->get(Context::OPTIMIZED_CODE_LIST));
     ClearWeakList<Code>(heap, context->get(Context::DEOPTIMIZED_CODE_LIST));
   }
 };


 template <>
 struct WeakListVisitor<JSArrayBufferView> {
   static void SetWeakNext(JSArrayBufferView* obj, Object* next) {
     obj->set_weak_next(next);
   }

   static Object* WeakNext(JSArrayBufferView* obj) { return obj->weak_next(); }

   static int WeakNextOffset() { return JSArrayBufferView::kWeakNextOffset; }

   static void VisitLiveObject(Heap*, JSArrayBufferView*, WeakObjectRetainer*) {}

   static void VisitPhantomObject(Heap*, JSArrayBufferView*) {}
 };


 template <>
 struct WeakListVisitor<JSArrayBuffer> {
   static void SetWeakNext(JSArrayBuffer* obj, Object* next) {
     obj->set_weak_next(next);
   }

   static Object* WeakNext(JSArrayBuffer* obj) { return obj->weak_next(); }

   static int WeakNextOffset() { return JSArrayBuffer::kWeakNextOffset; }

   static void VisitLiveObject(Heap* heap, JSArrayBuffer* array_buffer,
                               WeakObjectRetainer* retainer) {
     Object* typed_array_obj = VisitWeakList<JSArrayBufferView>(
         heap, array_buffer->weak_first_view(), retainer);
     array_buffer->set_weak_first_view(typed_array_obj);
     if (typed_array_obj != heap->undefined_value() && MustRecordSlots(heap)) {
       Object** slot = HeapObject::RawField(array_buffer,
                                            JSArrayBuffer::kWeakFirstViewOffset);
       heap->mark_compact_collector()->RecordSlot(slot, slot, typed_array_obj);
     }
   }

   static void VisitPhantomObject(Heap* heap, JSArrayBuffer* phantom) {
     Runtime::FreeArrayBuffer(heap->isolate(), phantom);
   }
 };


 template <>
 struct WeakListVisitor<AllocationSite> {
   static void SetWeakNext(AllocationSite* obj, Object* next) {
     obj->set_weak_next(next);
   }

   static Object* WeakNext(AllocationSite* obj) { return obj->weak_next(); }

   static int WeakNextOffset() { return AllocationSite::kWeakNextOffset; }

   static void VisitLiveObject(Heap*, AllocationSite*, WeakObjectRetainer*) {}

   static void VisitPhantomObject(Heap*, AllocationSite*) {}
 };


 template Object* VisitWeakList<Code>(Heap* heap, Object* list,
                                      WeakObjectRetainer* retainer);


 template Object* VisitWeakList<JSFunction>(Heap* heap, Object* list,
                                            WeakObjectRetainer* retainer);


 template Object* VisitWeakList<Context>(Heap* heap, Object* list,
                                         WeakObjectRetainer* retainer);


 template Object* VisitWeakList<JSArrayBuffer>(Heap* heap, Object* list,
                                               WeakObjectRetainer* retainer);


 template Object* VisitWeakList<AllocationSite>(Heap* heap, Object* list,
                                                WeakObjectRetainer* retainer);
 }
 }  // namespace v8::internal
	// Copyright 2011 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/v8.h"

	#include "src/heap/objects-visiting.h"

	namespace v8 {
	namespace internal {


	StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
	int instance_type, int instance_size, bool has_unboxed_fields) {
	if (instance_type < FIRST_NONSTRING_TYPE) {
	switch (instance_type & kStringRepresentationMask) {
	case kSeqStringTag:
	if ((instance_type & kStringEncodingMask) == kOneByteStringTag) {
	return kVisitSeqOneByteString;
	} else {
	return kVisitSeqTwoByteString;
	}

	case kConsStringTag:
	if (IsShortcutCandidate(instance_type)) {
	return kVisitShortcutCandidate;
	} else {
	return kVisitConsString;
	}

	case kSlicedStringTag:
	return kVisitSlicedString;

	case kExternalStringTag:
	return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
	instance_size, has_unboxed_fields);
	}
	UNREACHABLE();
	}

	switch (instance_type) {
	case BYTE_ARRAY_TYPE:
	return kVisitByteArray;

	case FREE_SPACE_TYPE:
	return kVisitFreeSpace;

	case FIXED_ARRAY_TYPE:
	return kVisitFixedArray;

	case FIXED_DOUBLE_ARRAY_TYPE:
	return kVisitFixedDoubleArray;

	case CONSTANT_POOL_ARRAY_TYPE:
	return kVisitConstantPoolArray;

	case ODDBALL_TYPE:
	return kVisitOddball;

	case MAP_TYPE:
	return kVisitMap;

	case CODE_TYPE:
	return kVisitCode;

	case CELL_TYPE:
	return kVisitCell;

	case PROPERTY_CELL_TYPE:
	return kVisitPropertyCell;

	case WEAK_CELL_TYPE:
	return kVisitWeakCell;

	case JS_SET_TYPE:
	return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
	JSSet::kSize, has_unboxed_fields);

	case JS_MAP_TYPE:
	return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
	JSMap::kSize, has_unboxed_fields);

	case JS_WEAK_MAP_TYPE:
	case JS_WEAK_SET_TYPE:
	return kVisitJSWeakCollection;

	case JS_REGEXP_TYPE:
	return kVisitJSRegExp;

	case SHARED_FUNCTION_INFO_TYPE:
	return kVisitSharedFunctionInfo;

	case JS_PROXY_TYPE:
	return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
	JSProxy::kSize, has_unboxed_fields);

	case JS_FUNCTION_PROXY_TYPE:
	return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
	JSFunctionProxy::kSize, has_unboxed_fields);

	case FOREIGN_TYPE:
	return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
	Foreign::kSize, has_unboxed_fields);

	case SYMBOL_TYPE:
	return kVisitSymbol;

	case FILLER_TYPE:
	return kVisitDataObjectGeneric;

	case JS_ARRAY_BUFFER_TYPE:
	return kVisitJSArrayBuffer;

	case JS_TYPED_ARRAY_TYPE:
	return kVisitJSTypedArray;

	case JS_DATA_VIEW_TYPE:
	return kVisitJSDataView;

	case JS_OBJECT_TYPE:
	case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
	case JS_GENERATOR_OBJECT_TYPE:
	case JS_MODULE_TYPE:
	case JS_VALUE_TYPE:
	case JS_DATE_TYPE:
	case JS_ARRAY_TYPE:
	case JS_GLOBAL_PROXY_TYPE:
	case JS_GLOBAL_OBJECT_TYPE:
	case JS_BUILTINS_OBJECT_TYPE:
	case JS_MESSAGE_OBJECT_TYPE:
	case JS_SET_ITERATOR_TYPE:
	case JS_MAP_ITERATOR_TYPE:
	return GetVisitorIdForSize(kVisitJSObject, kVisitJSObjectGeneric,
	instance_size, has_unboxed_fields);

	case JS_FUNCTION_TYPE:
	return kVisitJSFunction;

	case HEAP_NUMBER_TYPE:
	case MUTABLE_HEAP_NUMBER_TYPE:
	#define EXTERNAL_ARRAY_CASE(Type, type, TYPE, ctype, size) \
	case EXTERNAL_##TYPE##_ARRAY_TYPE:

	TYPED_ARRAYS(EXTERNAL_ARRAY_CASE)
	return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
	instance_size, has_unboxed_fields);
	#undef EXTERNAL_ARRAY_CASE

	case FIXED_UINT8_ARRAY_TYPE:
	case FIXED_INT8_ARRAY_TYPE:
	case FIXED_UINT16_ARRAY_TYPE:
	case FIXED_INT16_ARRAY_TYPE:
	case FIXED_UINT32_ARRAY_TYPE:
	case FIXED_INT32_ARRAY_TYPE:
	case FIXED_FLOAT32_ARRAY_TYPE:
	case FIXED_UINT8_CLAMPED_ARRAY_TYPE:
	return kVisitFixedTypedArray;

	case FIXED_FLOAT64_ARRAY_TYPE:
	return kVisitFixedFloat64Array;

	#define MAKE_STRUCT_CASE(NAME, Name, name) case NAME##_TYPE:
	STRUCT_LIST(MAKE_STRUCT_CASE)
	#undef MAKE_STRUCT_CASE
	if (instance_type == ALLOCATION_SITE_TYPE) {
	return kVisitAllocationSite;
	}

	return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
	instance_size, has_unboxed_fields);

	default:
	UNREACHABLE();
	return kVisitorIdCount;
	}
	}


	// We don't record weak slots during marking or scavenges. Instead we do it
	// once when we complete mark-compact cycle. Note that write barrier has no
	// effect if we are already in the middle of compacting mark-sweep cycle and we
	// have to record slots manually.
	static bool MustRecordSlots(Heap* heap) {
	return heap->gc_state() == Heap::MARK_COMPACT &&
	heap->mark_compact_collector()->is_compacting();
	}


	template <class T>
	struct WeakListVisitor;


	template <class T>
	Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer) {
	Object* undefined = heap->undefined_value();
	Object* head = undefined;
	T* tail = NULL;
	MarkCompactCollector* collector = heap->mark_compact_collector();
	bool record_slots = MustRecordSlots(heap);
	while (list != undefined) {
	// Check whether to keep the candidate in the list.
	T* candidate = reinterpret_cast<T*>(list);
	Object* retained = retainer->RetainAs(list);
	if (retained != NULL) {
	if (head == undefined) {
	// First element in the list.
	head = retained;
	} else {
	// Subsequent elements in the list.
	DCHECK(tail != NULL);
	WeakListVisitor<T>::SetWeakNext(tail, retained);
	if (record_slots) {
	Object** next_slot =
	HeapObject::RawField(tail, WeakListVisitor<T>::WeakNextOffset());
	collector->RecordSlot(next_slot, next_slot, retained);
	}
	}
	// Retained object is new tail.
	DCHECK(!retained->IsUndefined());
	candidate = reinterpret_cast<T*>(retained);
	tail = candidate;


	// tail is a live object, visit it.
	WeakListVisitor<T>::VisitLiveObject(heap, tail, retainer);
	} else {
	WeakListVisitor<T>::VisitPhantomObject(heap, candidate);
	}

	// Move to next element in the list.
	list = WeakListVisitor<T>::WeakNext(candidate);
	}

	// Terminate the list if there is one or more elements.
	if (tail != NULL) {
	WeakListVisitor<T>::SetWeakNext(tail, undefined);
	}
	return head;
	}


	template <class T>
	static void ClearWeakList(Heap* heap, Object* list) {
	Object* undefined = heap->undefined_value();
	while (list != undefined) {
	T* candidate = reinterpret_cast<T*>(list);
	list = WeakListVisitor<T>::WeakNext(candidate);
	WeakListVisitor<T>::SetWeakNext(candidate, undefined);
	}
	}


	template <>
	struct WeakListVisitor<JSFunction> {
	static void SetWeakNext(JSFunction* function, Object* next) {
	function->set_next_function_link(next);
	}

	static Object* WeakNext(JSFunction* function) {
	return function->next_function_link();
	}

	static int WeakNextOffset() { return JSFunction::kNextFunctionLinkOffset; }

	static void VisitLiveObject(Heap, JSFunction, WeakObjectRetainer*) {}

	static void VisitPhantomObject(Heap, JSFunction) {}
	};


	template <>
	struct WeakListVisitor<Code> {
	static void SetWeakNext(Code* code, Object* next) {
	code->set_next_code_link(next);
	}

	static Object* WeakNext(Code* code) { return code->next_code_link(); }

	static int WeakNextOffset() { return Code::kNextCodeLinkOffset; }

	static void VisitLiveObject(Heap, Code, WeakObjectRetainer*) {}

	static void VisitPhantomObject(Heap, Code) {}
	};


	template <>
	struct WeakListVisitor<Context> {
	static void SetWeakNext(Context* context, Object* next) {
	context->set(Context::NEXT_CONTEXT_LINK, next, UPDATE_WRITE_BARRIER);
	}

	static Object* WeakNext(Context* context) {
	return context->get(Context::NEXT_CONTEXT_LINK);
	}

	static int WeakNextOffset() {
	return FixedArray::SizeFor(Context::NEXT_CONTEXT_LINK);
	}

	static void VisitLiveObject(Heap* heap, Context* context,
	WeakObjectRetainer* retainer) {
	// Process the three weak lists linked off the context.
	DoWeakList<JSFunction>(heap, context, retainer,
	Context::OPTIMIZED_FUNCTIONS_LIST);
	DoWeakList<Code>(heap, context, retainer, Context::OPTIMIZED_CODE_LIST);
	DoWeakList<Code>(heap, context, retainer, Context::DEOPTIMIZED_CODE_LIST);
	}

	template <class T>
	static void DoWeakList(Heap* heap, Context* context,
	WeakObjectRetainer* retainer, int index) {
	// Visit the weak list, removing dead intermediate elements.
	Object* list_head = VisitWeakList<T>(heap, context->get(index), retainer);

	// Update the list head.
	context->set(index, list_head, UPDATE_WRITE_BARRIER);

	if (MustRecordSlots(heap)) {
	// Record the updated slot if necessary.
	Object** head_slot =
	HeapObject::RawField(context, FixedArray::SizeFor(index));
	heap->mark_compact_collector()->RecordSlot(head_slot, head_slot,
	list_head);
	}
	}

	static void VisitPhantomObject(Heap* heap, Context* context) {
	ClearWeakList<JSFunction>(heap,
	context->get(Context::OPTIMIZED_FUNCTIONS_LIST));
	ClearWeakList<Code>(heap, context->get(Context::OPTIMIZED_CODE_LIST));
	ClearWeakList<Code>(heap, context->get(Context::DEOPTIMIZED_CODE_LIST));
	}
	};


	template <>
	struct WeakListVisitor<JSArrayBufferView> {
	static void SetWeakNext(JSArrayBufferView* obj, Object* next) {
	obj->set_weak_next(next);
	}

	static Object* WeakNext(JSArrayBufferView* obj) { return obj->weak_next(); }

	static int WeakNextOffset() { return JSArrayBufferView::kWeakNextOffset; }

	static void VisitLiveObject(Heap, JSArrayBufferView, WeakObjectRetainer*) {}

	static void VisitPhantomObject(Heap, JSArrayBufferView) {}
	};


	template <>
	struct WeakListVisitor<JSArrayBuffer> {
	static void SetWeakNext(JSArrayBuffer* obj, Object* next) {
	obj->set_weak_next(next);
	}

	static Object* WeakNext(JSArrayBuffer* obj) { return obj->weak_next(); }

	static int WeakNextOffset() { return JSArrayBuffer::kWeakNextOffset; }

	static void VisitLiveObject(Heap* heap, JSArrayBuffer* array_buffer,
	WeakObjectRetainer* retainer) {
	Object* typed_array_obj = VisitWeakList<JSArrayBufferView>(
	heap, array_buffer->weak_first_view(), retainer);
	array_buffer->set_weak_first_view(typed_array_obj);
	if (typed_array_obj != heap->undefined_value() && MustRecordSlots(heap)) {
	Object** slot = HeapObject::RawField(array_buffer,
	JSArrayBuffer::kWeakFirstViewOffset);
	heap->mark_compact_collector()->RecordSlot(slot, slot, typed_array_obj);
	}
	}

	static void VisitPhantomObject(Heap* heap, JSArrayBuffer* phantom) {
	Runtime::FreeArrayBuffer(heap->isolate(), phantom);
	}
	};


	template <>
	struct WeakListVisitor<AllocationSite> {
	static void SetWeakNext(AllocationSite* obj, Object* next) {
	obj->set_weak_next(next);
	}

	static Object* WeakNext(AllocationSite* obj) { return obj->weak_next(); }

	static int WeakNextOffset() { return AllocationSite::kWeakNextOffset; }

	static void VisitLiveObject(Heap, AllocationSite, WeakObjectRetainer*) {}

	static void VisitPhantomObject(Heap, AllocationSite) {}
	};


	template Object* VisitWeakList<Code>(Heap* heap, Object* list,
	WeakObjectRetainer* retainer);


	template Object* VisitWeakList<JSFunction>(Heap* heap, Object* list,
	WeakObjectRetainer* retainer);


	template Object* VisitWeakList<Context>(Heap* heap, Object* list,
	WeakObjectRetainer* retainer);


	template Object* VisitWeakList<JSArrayBuffer>(Heap* heap, Object* list,
	WeakObjectRetainer* retainer);


	template Object* VisitWeakList<AllocationSite>(Heap* heap, Object* list,
	WeakObjectRetainer* retainer);
	}
	} // namespace v8::internal