// 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_OBJECTS_VISITING_INL_H_ #define V8_OBJECTS_VISITING_INL_H_ #include "src/heap/array-buffer-tracker.h" #include "src/heap/mark-compact.h" #include "src/heap/objects-visiting.h" #include "src/ic/ic-state.h" #include "src/macro-assembler.h" #include "src/objects-body-descriptors-inl.h" namespace v8 { namespace internal { template <typename Callback> Callback VisitorDispatchTable<Callback>::GetVisitor(Map* map) { return reinterpret_cast<Callback>(callbacks_[map->visitor_id()]); } template <typename StaticVisitor> void StaticNewSpaceVisitor<StaticVisitor>::Initialize() { table_.Register( kVisitShortcutCandidate, &FixedBodyVisitor<StaticVisitor, ConsString::BodyDescriptor, int>::Visit); table_.Register( kVisitConsString, &FixedBodyVisitor<StaticVisitor, ConsString::BodyDescriptor, int>::Visit); table_.Register( kVisitThinString, &FixedBodyVisitor<StaticVisitor, ThinString::BodyDescriptor, int>::Visit); table_.Register(kVisitSlicedString, &FixedBodyVisitor<StaticVisitor, SlicedString::BodyDescriptor, int>::Visit); table_.Register( kVisitSymbol, &FixedBodyVisitor<StaticVisitor, Symbol::BodyDescriptor, int>::Visit); table_.Register(kVisitFixedArray, &FlexibleBodyVisitor<StaticVisitor, FixedArray::BodyDescriptor, int>::Visit); table_.Register(kVisitFixedDoubleArray, &VisitFixedDoubleArray); table_.Register( kVisitFixedTypedArray, &FlexibleBodyVisitor<StaticVisitor, FixedTypedArrayBase::BodyDescriptor, int>::Visit); table_.Register( kVisitFixedFloat64Array, &FlexibleBodyVisitor<StaticVisitor, FixedTypedArrayBase::BodyDescriptor, int>::Visit); table_.Register( kVisitNativeContext, &FixedBodyVisitor<StaticVisitor, Context::ScavengeBodyDescriptor, int>::Visit); table_.Register(kVisitByteArray, &VisitByteArray); table_.Register( kVisitSharedFunctionInfo, &FixedBodyVisitor<StaticVisitor, SharedFunctionInfo::BodyDescriptor, int>::Visit); table_.Register(kVisitSeqOneByteString, &VisitSeqOneByteString); table_.Register(kVisitSeqTwoByteString, &VisitSeqTwoByteString); // Don't visit code entry. We are using this visitor only during scavenges. table_.Register( kVisitJSFunction, &FlexibleBodyVisitor<StaticVisitor, JSFunction::BodyDescriptorWeakCode, int>::Visit); table_.Register( kVisitJSArrayBuffer, &FlexibleBodyVisitor<StaticVisitor, JSArrayBuffer::BodyDescriptor, int>::Visit); table_.Register(kVisitFreeSpace, &VisitFreeSpace); table_.Register( kVisitJSWeakCollection, &FlexibleBodyVisitor<StaticVisitor, JSWeakCollection::BodyDescriptor, int>::Visit); table_.Register(kVisitJSRegExp, &JSObjectVisitor::Visit); table_.template RegisterSpecializations<DataObjectVisitor, kVisitDataObject, kVisitDataObjectGeneric>(); table_.template RegisterSpecializations<JSObjectVisitor, kVisitJSObject, kVisitJSObjectGeneric>(); // Not using specialized Api object visitor for newspace. table_.template RegisterSpecializations<JSObjectVisitor, kVisitJSApiObject, kVisitJSApiObjectGeneric>(); table_.template RegisterSpecializations<StructVisitor, kVisitStruct, kVisitStructGeneric>(); table_.Register(kVisitBytecodeArray, &UnreachableVisitor); table_.Register(kVisitSharedFunctionInfo, &UnreachableVisitor); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::Initialize() { table_.Register(kVisitShortcutCandidate, &FixedBodyVisitor<StaticVisitor, ConsString::BodyDescriptor, void>::Visit); table_.Register(kVisitConsString, &FixedBodyVisitor<StaticVisitor, ConsString::BodyDescriptor, void>::Visit); table_.Register(kVisitThinString, &FixedBodyVisitor<StaticVisitor, ThinString::BodyDescriptor, void>::Visit); table_.Register(kVisitSlicedString, &FixedBodyVisitor<StaticVisitor, SlicedString::BodyDescriptor, void>::Visit); table_.Register( kVisitSymbol, &FixedBodyVisitor<StaticVisitor, Symbol::BodyDescriptor, void>::Visit); table_.Register(kVisitFixedArray, &FixedArrayVisitor::Visit); table_.Register(kVisitFixedDoubleArray, &DataObjectVisitor::Visit); table_.Register( kVisitFixedTypedArray, &FlexibleBodyVisitor<StaticVisitor, FixedTypedArrayBase::BodyDescriptor, void>::Visit); table_.Register( kVisitFixedFloat64Array, &FlexibleBodyVisitor<StaticVisitor, FixedTypedArrayBase::BodyDescriptor, void>::Visit); table_.Register(kVisitNativeContext, &VisitNativeContext); table_.Register( kVisitAllocationSite, &FixedBodyVisitor<StaticVisitor, AllocationSite::MarkingBodyDescriptor, void>::Visit); table_.Register(kVisitByteArray, &DataObjectVisitor::Visit); table_.Register(kVisitBytecodeArray, &VisitBytecodeArray); table_.Register(kVisitFreeSpace, &DataObjectVisitor::Visit); table_.Register(kVisitSeqOneByteString, &DataObjectVisitor::Visit); table_.Register(kVisitSeqTwoByteString, &DataObjectVisitor::Visit); table_.Register(kVisitJSWeakCollection, &VisitWeakCollection); table_.Register( kVisitOddball, &FixedBodyVisitor<StaticVisitor, Oddball::BodyDescriptor, void>::Visit); table_.Register(kVisitMap, &VisitMap); table_.Register(kVisitCode, &VisitCode); table_.Register(kVisitSharedFunctionInfo, &VisitSharedFunctionInfo); table_.Register(kVisitJSFunction, &VisitJSFunction); table_.Register( kVisitJSArrayBuffer, &FlexibleBodyVisitor<StaticVisitor, JSArrayBuffer::BodyDescriptor, void>::Visit); table_.Register(kVisitJSRegExp, &JSObjectVisitor::Visit); table_.Register( kVisitCell, &FixedBodyVisitor<StaticVisitor, Cell::BodyDescriptor, void>::Visit); table_.Register(kVisitPropertyCell, &FixedBodyVisitor<StaticVisitor, PropertyCell::BodyDescriptor, void>::Visit); table_.Register(kVisitWeakCell, &VisitWeakCell); table_.Register(kVisitTransitionArray, &VisitTransitionArray); table_.template RegisterSpecializations<DataObjectVisitor, kVisitDataObject, kVisitDataObjectGeneric>(); table_.template RegisterSpecializations<JSObjectVisitor, kVisitJSObject, kVisitJSObjectGeneric>(); table_.template RegisterSpecializations<JSApiObjectVisitor, kVisitJSApiObject, kVisitJSApiObjectGeneric>(); table_.template RegisterSpecializations<StructObjectVisitor, kVisitStruct, kVisitStructGeneric>(); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitCodeEntry( Heap* heap, HeapObject* object, Address entry_address) { Code* code = Code::cast(Code::GetObjectFromEntryAddress(entry_address)); heap->mark_compact_collector()->RecordCodeEntrySlot(object, entry_address, code); StaticVisitor::MarkObject(heap, code); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitEmbeddedPointer( Heap* heap, RelocInfo* rinfo) { DCHECK(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT); HeapObject* object = HeapObject::cast(rinfo->target_object()); Code* host = rinfo->host(); heap->mark_compact_collector()->RecordRelocSlot(host, rinfo, object); // TODO(ulan): It could be better to record slots only for strongly embedded // objects here and record slots for weakly embedded object during clearing // of non-live references in mark-compact. if (!host->IsWeakObject(object)) { StaticVisitor::MarkObject(heap, object); } } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitCell(Heap* heap, RelocInfo* rinfo) { DCHECK(rinfo->rmode() == RelocInfo::CELL); Cell* cell = rinfo->target_cell(); Code* host = rinfo->host(); heap->mark_compact_collector()->RecordRelocSlot(host, rinfo, cell); if (!host->IsWeakObject(cell)) { StaticVisitor::MarkObject(heap, cell); } } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitDebugTarget(Heap* heap, RelocInfo* rinfo) { DCHECK(RelocInfo::IsDebugBreakSlot(rinfo->rmode()) && rinfo->IsPatchedDebugBreakSlotSequence()); Code* target = Code::GetCodeFromTargetAddress(rinfo->debug_call_address()); Code* host = rinfo->host(); heap->mark_compact_collector()->RecordRelocSlot(host, rinfo, target); StaticVisitor::MarkObject(heap, target); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitCodeTarget(Heap* heap, RelocInfo* rinfo) { DCHECK(RelocInfo::IsCodeTarget(rinfo->rmode())); Code* target = Code::GetCodeFromTargetAddress(rinfo->target_address()); Code* host = rinfo->host(); heap->mark_compact_collector()->RecordRelocSlot(host, rinfo, target); StaticVisitor::MarkObject(heap, target); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitCodeAgeSequence( Heap* heap, RelocInfo* rinfo) { DCHECK(RelocInfo::IsCodeAgeSequence(rinfo->rmode())); Code* target = rinfo->code_age_stub(); DCHECK(target != NULL); Code* host = rinfo->host(); heap->mark_compact_collector()->RecordRelocSlot(host, rinfo, target); StaticVisitor::MarkObject(heap, target); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitBytecodeArray( Map* map, HeapObject* object) { FixedBodyVisitor<StaticVisitor, BytecodeArray::MarkingBodyDescriptor, void>::Visit(map, object); BytecodeArray::cast(object)->MakeOlder(); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitNativeContext( Map* map, HeapObject* object) { FixedBodyVisitor<StaticVisitor, Context::MarkCompactBodyDescriptor, void>::Visit(map, object); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitMap(Map* map, HeapObject* object) { Heap* heap = map->GetHeap(); Map* map_object = Map::cast(object); // Clears the cache of ICs related to this map. if (FLAG_cleanup_code_caches_at_gc) { map_object->ClearCodeCache(heap); } // When map collection is enabled we have to mark through map's transitions // and back pointers in a special way to make these links weak. if (map_object->CanTransition()) { MarkMapContents(heap, map_object); } else { StaticVisitor::VisitPointers( heap, object, HeapObject::RawField(object, Map::kPointerFieldsBeginOffset), HeapObject::RawField(object, Map::kPointerFieldsEndOffset)); } } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitWeakCell(Map* map, HeapObject* object) { Heap* heap = map->GetHeap(); WeakCell* weak_cell = reinterpret_cast<WeakCell*>(object); // Enqueue weak cell in linked list of encountered weak collections. // We can ignore weak cells with cleared values because they will always // contain smi zero. if (weak_cell->next_cleared() && !weak_cell->cleared()) { HeapObject* value = HeapObject::cast(weak_cell->value()); if (ObjectMarking::IsBlackOrGrey(value)) { // Weak cells with live values are directly processed here to reduce // the processing time of weak cells during the main GC pause. Object** slot = HeapObject::RawField(weak_cell, WeakCell::kValueOffset); map->GetHeap()->mark_compact_collector()->RecordSlot(weak_cell, slot, *slot); } else { // If we do not know about liveness of values of weak cells, we have to // process them when we know the liveness of the whole transitive // closure. weak_cell->set_next(heap->encountered_weak_cells(), UPDATE_WEAK_WRITE_BARRIER); heap->set_encountered_weak_cells(weak_cell); } } } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitTransitionArray( Map* map, HeapObject* object) { TransitionArray* array = TransitionArray::cast(object); Heap* heap = array->GetHeap(); // Visit strong references. if (array->HasPrototypeTransitions()) { StaticVisitor::VisitPointer(heap, array, array->GetPrototypeTransitionsSlot()); } int num_transitions = TransitionArray::NumberOfTransitions(array); for (int i = 0; i < num_transitions; ++i) { StaticVisitor::VisitPointer(heap, array, array->GetKeySlot(i)); } // Enqueue the array in linked list of encountered transition arrays if it is // not already in the list. if (array->next_link()->IsUndefined(heap->isolate())) { Heap* heap = map->GetHeap(); array->set_next_link(heap->encountered_transition_arrays(), UPDATE_WEAK_WRITE_BARRIER); heap->set_encountered_transition_arrays(array); } } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitWeakCollection( Map* map, HeapObject* object) { typedef FlexibleBodyVisitor<StaticVisitor, JSWeakCollection::BodyDescriptorWeak, void> JSWeakCollectionBodyVisitor; Heap* heap = map->GetHeap(); JSWeakCollection* weak_collection = reinterpret_cast<JSWeakCollection*>(object); // Enqueue weak collection in linked list of encountered weak collections. if (weak_collection->next() == heap->undefined_value()) { weak_collection->set_next(heap->encountered_weak_collections()); heap->set_encountered_weak_collections(weak_collection); } // Skip visiting the backing hash table containing the mappings and the // pointer to the other enqueued weak collections, both are post-processed. JSWeakCollectionBodyVisitor::Visit(map, object); // Partially initialized weak collection is enqueued, but table is ignored. if (!weak_collection->table()->IsHashTable()) return; // Mark the backing hash table without pushing it on the marking stack. Object** slot = HeapObject::RawField(object, JSWeakCollection::kTableOffset); HeapObject* obj = HeapObject::cast(*slot); heap->mark_compact_collector()->RecordSlot(object, slot, obj); StaticVisitor::MarkObjectWithoutPush(heap, obj); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitCode(Map* map, HeapObject* object) { typedef FlexibleBodyVisitor<StaticVisitor, Code::BodyDescriptor, void> CodeBodyVisitor; Heap* heap = map->GetHeap(); Code* code = Code::cast(object); if (FLAG_age_code && !heap->isolate()->serializer_enabled()) { code->MakeOlder(); } CodeBodyVisitor::Visit(map, object); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfo( Map* map, HeapObject* object) { Heap* heap = map->GetHeap(); SharedFunctionInfo* shared = SharedFunctionInfo::cast(object); if (shared->ic_age() != heap->global_ic_age()) { shared->ResetForNewContext(heap->global_ic_age()); } MarkCompactCollector* collector = heap->mark_compact_collector(); if (collector->is_code_flushing_enabled()) { if (IsFlushable(heap, shared)) { // This function's code looks flushable. But we have to postpone // the decision until we see all functions that point to the same // SharedFunctionInfo because some of them might be optimized. // That would also make the non-optimized version of the code // non-flushable, because it is required for bailing out from // optimized code. collector->code_flusher()->AddCandidate(shared); // Treat the reference to the code object weakly. VisitSharedFunctionInfoWeakCode(map, object); return; } } VisitSharedFunctionInfoStrongCode(map, object); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitJSFunction(Map* map, HeapObject* object) { Heap* heap = map->GetHeap(); JSFunction* function = JSFunction::cast(object); MarkCompactCollector* collector = heap->mark_compact_collector(); if (collector->is_code_flushing_enabled()) { if (IsFlushable(heap, function)) { // This function's code looks flushable. But we have to postpone // the decision until we see all functions that point to the same // SharedFunctionInfo because some of them might be optimized. // That would also make the non-optimized version of the code // non-flushable, because it is required for bailing out from // optimized code. collector->code_flusher()->AddCandidate(function); // Treat the reference to the code object weakly. VisitJSFunctionWeakCode(map, object); return; } else { // Visit all unoptimized code objects to prevent flushing them. StaticVisitor::MarkObject(heap, function->shared()->code()); } } VisitJSFunctionStrongCode(map, object); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::MarkMapContents(Heap* heap, Map* map) { // Since descriptor arrays are potentially shared, ensure that only the // descriptors that belong to this map are marked. The first time a non-empty // descriptor array is marked, its header is also visited. The slot holding // the descriptor array will be implicitly recorded when the pointer fields of // this map are visited. Prototype maps don't keep track of transitions, so // just mark the entire descriptor array. if (!map->is_prototype_map()) { DescriptorArray* descriptors = map->instance_descriptors(); if (StaticVisitor::MarkObjectWithoutPush(heap, descriptors) && descriptors->length() > 0) { StaticVisitor::VisitPointers(heap, descriptors, descriptors->GetFirstElementAddress(), descriptors->GetDescriptorEndSlot(0)); } int start = 0; int end = map->NumberOfOwnDescriptors(); if (start < end) { StaticVisitor::VisitPointers(heap, descriptors, descriptors->GetDescriptorStartSlot(start), descriptors->GetDescriptorEndSlot(end)); } } // Mark the pointer fields of the Map. Since the transitions array has // been marked already, it is fine that one of these fields contains a // pointer to it. StaticVisitor::VisitPointers( heap, map, HeapObject::RawField(map, Map::kPointerFieldsBeginOffset), HeapObject::RawField(map, Map::kPointerFieldsEndOffset)); } inline static bool HasSourceCode(Heap* heap, SharedFunctionInfo* info) { Object* undefined = heap->undefined_value(); return (info->script() != undefined) && (reinterpret_cast<Script*>(info->script())->source() != undefined); } template <typename StaticVisitor> bool StaticMarkingVisitor<StaticVisitor>::IsFlushable(Heap* heap, JSFunction* function) { SharedFunctionInfo* shared_info = function->shared(); // Code is either on stack, in compilation cache or referenced // by optimized version of function. if (ObjectMarking::IsBlackOrGrey(function->code())) { return false; } // We do not (yet) flush code for optimized functions. if (function->code() != shared_info->code()) { return false; } // Check age of optimized code. if (FLAG_age_code && !function->code()->IsOld()) { return false; } return IsFlushable(heap, shared_info); } template <typename StaticVisitor> bool StaticMarkingVisitor<StaticVisitor>::IsFlushable( Heap* heap, SharedFunctionInfo* shared_info) { // Code is either on stack, in compilation cache or referenced // by optimized version of function. if (ObjectMarking::IsBlackOrGrey(shared_info->code())) { return false; } // The function must be compiled and have the source code available, // to be able to recompile it in case we need the function again. if (!(shared_info->is_compiled() && HasSourceCode(heap, shared_info))) { return false; } // We never flush code for API functions. if (shared_info->IsApiFunction()) { return false; } // Only flush code for functions. if (shared_info->code()->kind() != Code::FUNCTION) { return false; } // Function must be lazy compilable. if (!shared_info->allows_lazy_compilation()) { return false; } // We do not (yet?) flush code for generator functions, or async functions, // because we don't know if there are still live activations // (generator objects) on the heap. if (IsResumableFunction(shared_info->kind())) { return false; } // If this is a full script wrapped in a function we do not flush the code. if (shared_info->is_toplevel()) { return false; } // The function must be user code. if (!shared_info->IsUserJavaScript()) { return false; } // Maintain debug break slots in the code. if (shared_info->HasDebugCode()) { return false; } // If this is a function initialized with %SetCode then the one-to-one // relation between SharedFunctionInfo and Code is broken. if (shared_info->dont_flush()) { return false; } // Check age of code. If code aging is disabled we never flush. if (!FLAG_age_code || !shared_info->code()->IsOld()) { return false; } return true; } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfoStrongCode( Map* map, HeapObject* object) { FixedBodyVisitor<StaticVisitor, SharedFunctionInfo::BodyDescriptor, void>::Visit(map, object); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitSharedFunctionInfoWeakCode( Map* map, HeapObject* object) { // Skip visiting kCodeOffset as it is treated weakly here. STATIC_ASSERT(SharedFunctionInfo::kCodeOffset < SharedFunctionInfo::BodyDescriptorWeakCode::kStartOffset); FixedBodyVisitor<StaticVisitor, SharedFunctionInfo::BodyDescriptorWeakCode, void>::Visit(map, object); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitJSFunctionStrongCode( Map* map, HeapObject* object) { typedef FlexibleBodyVisitor<StaticVisitor, JSFunction::BodyDescriptorStrongCode, void> JSFunctionStrongCodeBodyVisitor; JSFunctionStrongCodeBodyVisitor::Visit(map, object); } template <typename StaticVisitor> void StaticMarkingVisitor<StaticVisitor>::VisitJSFunctionWeakCode( Map* map, HeapObject* object) { typedef FlexibleBodyVisitor<StaticVisitor, JSFunction::BodyDescriptorWeakCode, void> JSFunctionWeakCodeBodyVisitor; JSFunctionWeakCodeBodyVisitor::Visit(map, object); } } // namespace internal } // namespace v8 #endif // V8_OBJECTS_VISITING_INL_H_