name : pointer-policies.h // Copyright 2020 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 INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_ #define INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_ #include <cstdint> #include <type_traits> #include "cppgc/internal/member-storage.h" #include "cppgc/internal/write-barrier.h" #include "cppgc/sentinel-pointer.h" #include "cppgc/source-location.h" #include "cppgc/type-traits.h" #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { class HeapBase; class PersistentRegion; class CrossThreadPersistentRegion; // Tags to distinguish between strong and weak member types. class StrongMemberTag; class WeakMemberTag; class UntracedMemberTag; struct DijkstraWriteBarrierPolicy { V8_INLINE static void InitializingBarrier(const void*, const void*) { // Since in initializing writes the source object is always white, having no // barrier doesn't break the tri-color invariant. } template <WriteBarrierSlotType SlotType> V8_INLINE static void AssigningBarrier(const void* slot, const void* value) { #ifdef CPPGC_SLIM_WRITE_BARRIER if (V8_UNLIKELY(WriteBarrier::IsEnabled())) WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot); #else // !CPPGC_SLIM_WRITE_BARRIER WriteBarrier::Params params; const WriteBarrier::Type type = WriteBarrier::GetWriteBarrierType(slot, value, params); WriteBarrier(type, params, slot, value); #endif // !CPPGC_SLIM_WRITE_BARRIER } template <WriteBarrierSlotType SlotType> V8_INLINE static void AssigningBarrier(const void* slot, RawPointer storage) { static_assert( SlotType == WriteBarrierSlotType::kUncompressed, "Assigning storages of Member and UncompressedMember is not supported"); #ifdef CPPGC_SLIM_WRITE_BARRIER if (V8_UNLIKELY(WriteBarrier::IsEnabled())) WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot); #else // !CPPGC_SLIM_WRITE_BARRIER WriteBarrier::Params params; const WriteBarrier::Type type = WriteBarrier::GetWriteBarrierType(slot, storage, params); WriteBarrier(type, params, slot, storage.Load()); #endif // !CPPGC_SLIM_WRITE_BARRIER } #if defined(CPPGC_POINTER_COMPRESSION) template <WriteBarrierSlotType SlotType> V8_INLINE static void AssigningBarrier(const void* slot, CompressedPointer storage) { static_assert( SlotType == WriteBarrierSlotType::kCompressed, "Assigning storages of Member and UncompressedMember is not supported"); #ifdef CPPGC_SLIM_WRITE_BARRIER if (V8_UNLIKELY(WriteBarrier::IsEnabled())) WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot); #else // !CPPGC_SLIM_WRITE_BARRIER WriteBarrier::Params params; const WriteBarrier::Type type = WriteBarrier::GetWriteBarrierType(slot, storage, params); WriteBarrier(type, params, slot, storage.Load()); #endif // !CPPGC_SLIM_WRITE_BARRIER } #endif // defined(CPPGC_POINTER_COMPRESSION) private: V8_INLINE static void WriteBarrier(WriteBarrier::Type type, const WriteBarrier::Params& params, const void* slot, const void* value) { switch (type) { case WriteBarrier::Type::kGenerational: WriteBarrier::GenerationalBarrier< WriteBarrier::GenerationalBarrierType::kPreciseSlot>(params, slot); break; case WriteBarrier::Type::kMarking: WriteBarrier::DijkstraMarkingBarrier(params, value); break; case WriteBarrier::Type::kNone: break; } } }; struct NoWriteBarrierPolicy { V8_INLINE static void InitializingBarrier(const void*, const void*) {} template <WriteBarrierSlotType> V8_INLINE static void AssigningBarrier(const void*, const void*) {} template <WriteBarrierSlotType, typename MemberStorage> V8_INLINE static void AssigningBarrier(const void*, MemberStorage) {} }; class V8_EXPORT SameThreadEnabledCheckingPolicyBase { protected: void CheckPointerImpl(const void* ptr, bool points_to_payload, bool check_off_heap_assignments); const HeapBase* heap_ = nullptr; }; template <bool kCheckOffHeapAssignments> class V8_EXPORT SameThreadEnabledCheckingPolicy : private SameThreadEnabledCheckingPolicyBase { protected: template <typename T> void CheckPointer(const T* ptr) { if (!ptr || (kSentinelPointer == ptr)) return; CheckPointersImplTrampoline<T>::Call(this, ptr); } private: template <typename T, bool = IsCompleteV<T>> struct CheckPointersImplTrampoline { static void Call(SameThreadEnabledCheckingPolicy* policy, const T* ptr) { policy->CheckPointerImpl(ptr, false, kCheckOffHeapAssignments); } }; template <typename T> struct CheckPointersImplTrampoline<T, true> { static void Call(SameThreadEnabledCheckingPolicy* policy, const T* ptr) { policy->CheckPointerImpl(ptr, IsGarbageCollectedTypeV<T>, kCheckOffHeapAssignments); } }; }; class DisabledCheckingPolicy { protected: V8_INLINE void CheckPointer(const void*) {} }; #ifdef DEBUG // Off heap members are not connected to object graph and thus cannot ressurect // dead objects. using DefaultMemberCheckingPolicy = SameThreadEnabledCheckingPolicy<false /* kCheckOffHeapAssignments*/>; using DefaultPersistentCheckingPolicy = SameThreadEnabledCheckingPolicy<true /* kCheckOffHeapAssignments*/>; #else // !DEBUG using DefaultMemberCheckingPolicy = DisabledCheckingPolicy; using DefaultPersistentCheckingPolicy = DisabledCheckingPolicy; #endif // !DEBUG // For CT(W)P neither marking information (for value), nor objectstart bitmap // (for slot) are guaranteed to be present because there's no synchronization // between heaps after marking. using DefaultCrossThreadPersistentCheckingPolicy = DisabledCheckingPolicy; class KeepLocationPolicy { public: constexpr const SourceLocation& Location() const { return location_; } protected: constexpr KeepLocationPolicy() = default; constexpr explicit KeepLocationPolicy(const SourceLocation& location) : location_(location) {} // KeepLocationPolicy must not copy underlying source locations. KeepLocationPolicy(const KeepLocationPolicy&) = delete; KeepLocationPolicy& operator=(const KeepLocationPolicy&) = delete; // Location of the original moved from object should be preserved. KeepLocationPolicy(KeepLocationPolicy&&) = default; KeepLocationPolicy& operator=(KeepLocationPolicy&&) = default; private: SourceLocation location_; }; class IgnoreLocationPolicy { public: constexpr SourceLocation Location() const { return {}; } protected: constexpr IgnoreLocationPolicy() = default; constexpr explicit IgnoreLocationPolicy(const SourceLocation&) {} }; #if CPPGC_SUPPORTS_OBJECT_NAMES using DefaultLocationPolicy = KeepLocationPolicy; #else using DefaultLocationPolicy = IgnoreLocationPolicy; #endif struct StrongPersistentPolicy { using IsStrongPersistent = std::true_type; static V8_EXPORT PersistentRegion& GetPersistentRegion(const void* object); }; struct WeakPersistentPolicy { using IsStrongPersistent = std::false_type; static V8_EXPORT PersistentRegion& GetPersistentRegion(const void* object); }; struct StrongCrossThreadPersistentPolicy { using IsStrongPersistent = std::true_type; static V8_EXPORT CrossThreadPersistentRegion& GetPersistentRegion( const void* object); }; struct WeakCrossThreadPersistentPolicy { using IsStrongPersistent = std::false_type; static V8_EXPORT CrossThreadPersistentRegion& GetPersistentRegion( const void* object); }; // Forward declarations setting up the default policies. template <typename T, typename WeaknessPolicy, typename LocationPolicy = DefaultLocationPolicy, typename CheckingPolicy = DefaultCrossThreadPersistentCheckingPolicy> class BasicCrossThreadPersistent; template <typename T, typename WeaknessPolicy, typename LocationPolicy = DefaultLocationPolicy, typename CheckingPolicy = DefaultPersistentCheckingPolicy> class BasicPersistent; template <typename T, typename WeaknessTag, typename WriteBarrierPolicy, typename CheckingPolicy = DefaultMemberCheckingPolicy, typename StorageType = DefaultMemberStorage> class BasicMember; } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_