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// 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_HEAP_OBJECTS_VISITING_H_
#define V8_HEAP_OBJECTS_VISITING_H_
#include "src/base/logging.h"
#include "src/objects/bytecode-array.h"
#include "src/objects/contexts.h"
#include "src/objects/fixed-array.h"
#include "src/objects/js-weak-refs.h"
#include "src/objects/map.h"
#include "src/objects/object-list-macros.h"
#include "src/objects/objects.h"
#include "src/objects/shared-function-info.h"
#include "src/objects/string.h"
#include "src/objects/visitors.h"
namespace v8 {
namespace internal {
#define TYPED_VISITOR_ID_LIST(V) \
V(AccessorInfo) \
V(AllocationSite) \
V(BigInt) \
V(ByteArray) \
V(BytecodeArray) \
V(ExternalPointerArray) \
V(CallHandlerInfo) \
V(Cell) \
V(InstructionStream) \
V(Code) \
V(CoverageInfo) \
V(DataHandler) \
V(EmbedderDataArray) \
V(EphemeronHashTable) \
V(ExternalString) \
V(FeedbackCell) \
V(FeedbackMetadata) \
V(FixedArray) \
V(FixedDoubleArray) \
V(JSArrayBuffer) \
V(JSDataViewOrRabGsabDataView) \
V(JSExternalObject) \
V(JSFinalizationRegistry) \
V(JSFunction) \
V(JSObject) \
V(JSSynchronizationPrimitive) \
V(JSTypedArray) \
V(WeakCell) \
V(JSWeakCollection) \
V(JSWeakRef) \
V(Map) \
V(NativeContext) \
V(Oddball) \
V(Hole) \
V(PreparseData) \
V(PromiseOnStack) \
V(PropertyArray) \
V(PropertyCell) \
V(PrototypeInfo) \
V(SharedFunctionInfo) \
V(SloppyArgumentsElements) \
V(SmallOrderedHashMap) \
V(SmallOrderedHashSet) \
V(SmallOrderedNameDictionary) \
V(SourceTextModule) \
V(SwissNameDictionary) \
V(Symbol) \
V(SyntheticModule) \
V(TransitionArray) \
IF_WASM(V, WasmApiFunctionRef) \
IF_WASM(V, WasmArray) \
IF_WASM(V, WasmCapiFunctionData) \
IF_WASM(V, WasmExportedFunctionData) \
IF_WASM(V, WasmFunctionData) \
IF_WASM(V, WasmIndirectFunctionTable) \
IF_WASM(V, WasmInstanceObject) \
IF_WASM(V, WasmInternalFunction) \
IF_WASM(V, WasmJSFunctionData) \
IF_WASM(V, WasmStruct) \
IF_WASM(V, WasmSuspenderObject) \
IF_WASM(V, WasmResumeData) \
IF_WASM(V, WasmTypeInfo) \
IF_WASM(V, WasmContinuationObject) \
IF_WASM(V, WasmNull)
#define FORWARD_DECLARE(TypeName) class TypeName;
TYPED_VISITOR_ID_LIST(FORWARD_DECLARE)
TORQUE_VISITOR_ID_LIST(FORWARD_DECLARE)
#undef FORWARD_DECLARE
// The base class for visitors that need to dispatch on object type. The default
// behavior of all visit functions is to iterate body of the given object using
// the BodyDescriptor of the object.
//
// The visit functions return the size of the object cast to ResultType.
//
// This class is intended to be used in the following way:
//
// class SomeVisitor : public HeapVisitor<ResultType, SomeVisitor> {
// ...
// }
template <typename ResultType, typename ConcreteVisitor>
class HeapVisitor : public ObjectVisitorWithCageBases {
public:
inline HeapVisitor(PtrComprCageBase cage_base,
PtrComprCageBase code_cage_base);
inline explicit HeapVisitor(Isolate* isolate);
inline explicit HeapVisitor(Heap* heap);
V8_INLINE ResultType Visit(Tagged<HeapObject> object);
V8_INLINE ResultType Visit(Tagged<Map> map, Tagged<HeapObject> object);
protected:
// If this predicate returns false the default implementations of Visit*
// functions bail out from visiting the map pointer.
V8_INLINE static constexpr bool ShouldVisitMapPointer() { return true; }
// If this predicate returns false the default implementations of Visit*
// functions bail out from visiting known read-only maps.
V8_INLINE static constexpr bool ShouldVisitReadOnlyMapPointer() {
return true;
}
// Only visits the Map pointer if `ShouldVisitMapPointer()` returns true.
template <VisitorId visitor_id>
V8_INLINE void VisitMapPointerIfNeeded(Tagged<HeapObject> host);
ConcreteVisitor* concrete_visitor() {
return static_cast<ConcreteVisitor*>(this);
}
const ConcreteVisitor* concrete_visitor() const {
return static_cast<const ConcreteVisitor*>(this);
}
#define VISIT(TypeName) \
V8_INLINE ResultType Visit##TypeName(Tagged<Map> map, \
Tagged<TypeName> object);
TYPED_VISITOR_ID_LIST(VISIT)
TORQUE_VISITOR_ID_LIST(VISIT)
#undef VISIT
V8_INLINE ResultType VisitShortcutCandidate(Tagged<Map> map,
Tagged<ConsString> object);
V8_INLINE ResultType VisitDataObject(Tagged<Map> map,
Tagged<HeapObject> object);
V8_INLINE ResultType VisitJSObjectFast(Tagged<Map> map,
Tagged<JSObject> object);
V8_INLINE ResultType VisitJSApiObject(Tagged<Map> map,
Tagged<JSObject> object);
V8_INLINE ResultType VisitStruct(Tagged<Map> map, Tagged<HeapObject> object);
V8_INLINE ResultType VisitFreeSpace(Tagged<Map> map,
Tagged<FreeSpace> object);
template <typename T, typename TBodyDescriptor = typename T::BodyDescriptor>
V8_INLINE ResultType VisitJSObjectSubclass(Tagged<Map> map, Tagged<T> object);
template <typename T>
static V8_INLINE Tagged<T> Cast(Tagged<HeapObject> object);
};
// These strings can be sources of safe string transitions. Transitions are safe
// if they don't result in invalidated slots. It's safe to read the length field
// on such strings as that's common for all.
//
// No special visitors are generated for such strings.
// V(VisitorId, TypeName)
#define SAFE_STRING_TRANSITION_SOURCES(V) \
V(SeqOneByteString, SeqOneByteString) \
V(SeqTwoByteString, SeqTwoByteString)
// These strings can be sources of unsafe string transitions.
// V(VisitorId, TypeName)
#define UNSAFE_STRING_TRANSITION_SOURCES(V) \
V(ExternalString, ExternalString) \
V(ConsString, ConsString) \
V(SlicedString, SlicedString)
// V(VisitorId, TypeName)
#define UNSAFE_STRING_TRANSITION_TARGETS(V) \
UNSAFE_STRING_TRANSITION_SOURCES(V) \
V(ShortcutCandidate, ConsString) \
V(ThinString, ThinString)
// A HeapVisitor that allows for concurrently tracing through objects. Tracing
// through objects with unsafe shape changes is guarded by
// `EnableConcurrentVisitation()` which defaults to off.
template <typename ResultType, typename ConcreteVisitor>
class ConcurrentHeapVisitor : public HeapVisitor<ResultType, ConcreteVisitor> {
public:
V8_INLINE explicit ConcurrentHeapVisitor(Isolate* isolate);
V8_INLINE static constexpr bool EnableConcurrentVisitation() { return false; }
protected:
#define VISIT_AS_LOCKED_STRING(VisitorId, TypeName) \
V8_INLINE ResultType Visit##TypeName(Tagged<Map> map, \
Tagged<TypeName> object);
UNSAFE_STRING_TRANSITION_SOURCES(VISIT_AS_LOCKED_STRING)
#undef VISIT_AS_LOCKED_STRING
template <typename T>
static V8_INLINE Tagged<T> Cast(Tagged<HeapObject> object);
private:
template <typename T>
V8_INLINE ResultType VisitStringLocked(Tagged<T> object);
friend class HeapVisitor<ResultType, ConcreteVisitor>;
};
template <typename ConcreteVisitor>
class NewSpaceVisitor : public ConcurrentHeapVisitor<int, ConcreteVisitor> {
public:
V8_INLINE explicit NewSpaceVisitor(Isolate* isolate);
// Special cases: Unreachable visitors for objects that are never found in the
// young generation.
void VisitInstructionStreamPointer(Tagged<Code>,
InstructionStreamSlot) final {
UNREACHABLE();
}
void VisitCodeTarget(Tagged<InstructionStream> host, RelocInfo*) final {
UNREACHABLE();
}
void VisitEmbeddedPointer(Tagged<InstructionStream> host, RelocInfo*) final {
UNREACHABLE();
}
void VisitMapPointer(Tagged<HeapObject>) override { UNREACHABLE(); }
protected:
V8_INLINE static constexpr bool ShouldVisitMapPointer() { return false; }
// Special cases: Unreachable visitors for objects that are never found in the
// young generation.
int VisitNativeContext(Tagged<Map>, Tagged<NativeContext>) { UNREACHABLE(); }
int VisitBytecodeArray(Tagged<Map>, Tagged<BytecodeArray>) { UNREACHABLE(); }
int VisitSharedFunctionInfo(Tagged<Map> map, Tagged<SharedFunctionInfo>) {
UNREACHABLE();
}
int VisitWeakCell(Tagged<Map>, Tagged<WeakCell>) { UNREACHABLE(); }
friend class HeapVisitor<int, ConcreteVisitor>;
};
class WeakObjectRetainer;
// A weak list is single linked list where each element has a weak pointer to
// the next element. Given the head of the list, this function removes dead
// elements from the list and if requested records slots for next-element
// pointers. The template parameter T is a WeakListVisitor that defines how to
// access the next-element pointers.
template <class T>
Tagged<Object> VisitWeakList(Heap* heap, Tagged<Object> list,
WeakObjectRetainer* retainer);
} // namespace internal
} // namespace v8
#endif // V8_HEAP_OBJECTS_VISITING_H_
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