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📁 ..	-	2025-10-13 08:01
📄 api-constants.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_API_CONSTANTS_H_ #define INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_ #include <cstddef> #include <cstdint> #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { // Embedders should not rely on this code! // Internal constants to avoid exposing internal types on the API surface. namespace api_constants { constexpr size_t kKB = 1024; constexpr size_t kMB = kKB * 1024; constexpr size_t kGB = kMB * 1024; // Offset of the uint16_t bitfield from the payload contaning the // in-construction bit. This is subtracted from the payload pointer to get // to the right bitfield. static constexpr size_t kFullyConstructedBitFieldOffsetFromPayload = 2 * sizeof(uint16_t); // Mask for in-construction bit. static constexpr uint16_t kFullyConstructedBitMask = uint16_t{1}; static constexpr size_t kPageSize = size_t{1} << 17; #if defined(V8_TARGET_ARCH_ARM64) && defined(V8_OS_DARWIN) constexpr size_t kGuardPageSize = 0; #else constexpr size_t kGuardPageSize = 4096; #endif static constexpr size_t kLargeObjectSizeThreshold = kPageSize / 2; #if defined(CPPGC_CAGED_HEAP) #if defined(CPPGC_2GB_CAGE) constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(2) * kGB; #else // !defined(CPPGC_2GB_CAGE) constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(4) * kGB; #endif // !defined(CPPGC_2GB_CAGE) constexpr size_t kCagedHeapReservationAlignment = kCagedHeapReservationSize; #endif // defined(CPPGC_CAGED_HEAP) static constexpr size_t kDefaultAlignment = sizeof(void); // Maximum support alignment for a type as in `alignof(T)`. static constexpr size_t kMaxSupportedAlignment = 2 kDefaultAlignment; // Granularity of heap allocations. constexpr size_t kAllocationGranularity = sizeof(void*); // Default cacheline size. constexpr size_t kCachelineSize = 64; } // namespace api_constants } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_	2.11 KB	2025-02-28 19:16
📄 atomic-entry-flag.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_ATOMIC_ENTRY_FLAG_H_ #define INCLUDE_CPPGC_INTERNAL_ATOMIC_ENTRY_FLAG_H_ #include <atomic> namespace cppgc { namespace internal { // A flag which provides a fast check whether a scope may be entered on the // current thread, without needing to access thread-local storage or mutex. Can // have false positives (i.e., spuriously report that it might be entered), so // it is expected that this will be used in tandem with a precise check that the // scope is in fact entered on that thread. // // Example: // g_frobnicating_flag.MightBeEntered() && // ThreadLocalFrobnicator().IsFrobnicating() // // Relaxed atomic operations are sufficient, since: // - all accesses remain atomic // - each thread must observe its own operations in order // - no thread ever exits the flag more times than it enters (if used correctly) // And so if a thread observes zero, it must be because it has observed an equal // number of exits as entries. class AtomicEntryFlag final { public: void Enter() { entries_.fetch_add(1, std::memory_order_relaxed); } void Exit() { entries_.fetch_sub(1, std::memory_order_relaxed); } // Returns false only if the current thread is not between a call to Enter // and a call to Exit. Returns true if this thread or another thread may // currently be in the scope guarded by this flag. bool MightBeEntered() const { return entries_.load(std::memory_order_relaxed) != 0; } private: std::atomic_int entries_{0}; }; } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_ATOMIC_ENTRY_FLAG_H_	1.72 KB	2025-02-28 19:16
📄 base-page-handle.h // Copyright 2022 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_BASE_PAGE_HANDLE_H_ #define INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_ #include "cppgc/heap-handle.h" #include "cppgc/internal/api-constants.h" #include "cppgc/internal/logging.h" #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { // The class is needed in the header to allow for fast access to HeapHandle in // the write barrier. class BasePageHandle { public: static V8_INLINE BasePageHandle* FromPayload(void* payload) { return reinterpret_cast<BasePageHandle>( (reinterpret_cast<uintptr_t>(payload) & ~(api_constants::kPageSize - 1)) + api_constants::kGuardPageSize); } static V8_INLINE const BasePageHandle FromPayload(const void* payload) { return FromPayload(const_cast<void*>(payload)); } HeapHandle& heap_handle() { return heap_handle_; } const HeapHandle& heap_handle() const { return heap_handle_; } protected: explicit BasePageHandle(HeapHandle& heap_handle) : heap_handle_(heap_handle) { CPPGC_DCHECK(reinterpret_cast<uintptr_t>(this) % api_constants::kPageSize == api_constants::kGuardPageSize); } HeapHandle& heap_handle_; }; } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_	1.44 KB	2025-02-28 19:16
📄 caged-heap-local-data.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_CAGED_HEAP_LOCAL_DATA_H_ #define INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_ #include <array> #include <cstddef> #include <cstdint> #include "cppgc/internal/api-constants.h" #include "cppgc/internal/caged-heap.h" #include "cppgc/internal/logging.h" #include "cppgc/platform.h" #include "v8config.h" // NOLINT(build/include_directory) #if __cpp_lib_bitopts #include <bit> #endif // __cpp_lib_bitopts #if defined(CPPGC_CAGED_HEAP) namespace cppgc { namespace internal { class HeapBase; class HeapBaseHandle; #if defined(CPPGC_YOUNG_GENERATION) // AgeTable is the bytemap needed for the fast generation check in the write // barrier. AgeTable contains entries that correspond to 4096 bytes memory // regions (cards). Each entry in the table represents generation of the objects // that reside on the corresponding card (young, old or mixed). class V8_EXPORT AgeTable final { static constexpr size_t kRequiredSize = 1 * api_constants::kMB; static constexpr size_t kAllocationGranularity = api_constants::kAllocationGranularity; public: // Represents age of the objects living on a single card. enum class Age : uint8_t { kOld, kYoung, kMixed }; // When setting age for a range, consider or ignore ages of the adjacent // cards. enum class AdjacentCardsPolicy : uint8_t { kConsider, kIgnore }; static constexpr size_t kCardSizeInBytes = api_constants::kCagedHeapReservationSize / kRequiredSize; void SetAge(uintptr_t cage_offset, Age age) { table_[card(cage_offset)] = age; } V8_INLINE Age GetAge(uintptr_t cage_offset) const { return table_[card(cage_offset)]; } void SetAgeForRange(uintptr_t cage_offset_begin, uintptr_t cage_offset_end, Age age, AdjacentCardsPolicy adjacent_cards_policy); Age GetAgeForRange(uintptr_t cage_offset_begin, uintptr_t cage_offset_end) const; void ResetForTesting(); private: V8_INLINE size_t card(uintptr_t offset) const { constexpr size_t kGranularityBits = #if __cpp_lib_bitopts std::countr_zero(static_cast<uint32_t>(kCardSizeInBytes)); #elif V8_HAS_BUILTIN_CTZ __builtin_ctz(static_cast<uint32_t>(kCardSizeInBytes)); #else //! V8_HAS_BUILTIN_CTZ // Hardcode and check with assert. #if defined(CPPGC_2GB_CAGE) 11; #else // !defined(CPPGC_2GB_CAGE) 12; #endif // !defined(CPPGC_2GB_CAGE) #endif // !V8_HAS_BUILTIN_CTZ static_assert((1 << kGranularityBits) == kCardSizeInBytes); const size_t entry = offset >> kGranularityBits; CPPGC_DCHECK(table_.size() > entry); return entry; } std::array<Age, kRequiredSize> table_; }; static_assert(sizeof(AgeTable) == 1 * api_constants::kMB, "Size of AgeTable is 1MB"); #endif // CPPGC_YOUNG_GENERATION struct CagedHeapLocalData final { V8_INLINE static CagedHeapLocalData& Get() { return reinterpret_cast<CagedHeapLocalData>(CagedHeapBase::GetBase()); } #if defined(CPPGC_YOUNG_GENERATION) AgeTable age_table; #endif }; } // namespace internal } // namespace cppgc #endif // defined(CPPGC_CAGED_HEAP) #endif // INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_	3.28 KB	2025-02-28 19:16
📄 caged-heap.h // Copyright 2022 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_CAGED_HEAP_H_ #define INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_H_ #include <climits> #include <cstddef> #include "cppgc/internal/api-constants.h" #include "cppgc/internal/base-page-handle.h" #include "v8config.h" // NOLINT(build/include_directory) #if defined(CPPGC_CAGED_HEAP) namespace cppgc { namespace internal { class V8_EXPORT CagedHeapBase { public: V8_INLINE static uintptr_t OffsetFromAddress(const void* address) { return reinterpret_cast<uintptr_t>(address) & (api_constants::kCagedHeapReservationAlignment - 1); } V8_INLINE static bool IsWithinCage(const void* address) { CPPGC_DCHECK(g_heap_base_); return (reinterpret_cast<uintptr_t>(address) & ~(api_constants::kCagedHeapReservationAlignment - 1)) == g_heap_base_; } V8_INLINE static bool AreWithinCage(const void* addr1, const void* addr2) { #if defined(CPPGC_2GB_CAGE) static constexpr size_t kHalfWordShift = sizeof(uint32_t) * CHAR_BIT - 1; #else //! defined(CPPGC_2GB_CAGE) static constexpr size_t kHalfWordShift = sizeof(uint32_t) * CHAR_BIT; #endif //! defined(CPPGC_2GB_CAGE) static_assert((static_cast<size_t>(1) << kHalfWordShift) == api_constants::kCagedHeapReservationSize); CPPGC_DCHECK(g_heap_base_); return !(((reinterpret_cast<uintptr_t>(addr1) ^ g_heap_base_) \| (reinterpret_cast<uintptr_t>(addr2) ^ g_heap_base_)) >> kHalfWordShift); } V8_INLINE static uintptr_t GetBase() { return g_heap_base_; } private: friend class CagedHeap; static uintptr_t g_heap_base_; }; } // namespace internal } // namespace cppgc #endif // defined(CPPGC_CAGED_HEAP) #endif // INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_H_	1.88 KB	2025-02-28 19:16
📄 compiler-specific.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_COMPILER_SPECIFIC_H_ #define INCLUDE_CPPGC_INTERNAL_COMPILER_SPECIFIC_H_ namespace cppgc { #if defined(__has_attribute) #define CPPGC_HAS_ATTRIBUTE(FEATURE) __has_attribute(FEATURE) #else #define CPPGC_HAS_ATTRIBUTE(FEATURE) 0 #endif #if defined(__has_cpp_attribute) #define CPPGC_HAS_CPP_ATTRIBUTE(FEATURE) __has_cpp_attribute(FEATURE) #else #define CPPGC_HAS_CPP_ATTRIBUTE(FEATURE) 0 #endif // [[no_unique_address]] comes in C++20 but supported in clang with -std >= // c++11. #if CPPGC_HAS_CPP_ATTRIBUTE(no_unique_address) #define CPPGC_NO_UNIQUE_ADDRESS [[no_unique_address]] #else #define CPPGC_NO_UNIQUE_ADDRESS #endif #if CPPGC_HAS_ATTRIBUTE(unused) #define CPPGC_UNUSED __attribute__((unused)) #else #define CPPGC_UNUSED #endif } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_COMPILER_SPECIFIC_H_	1019 B	2025-02-28 19:16
📄 finalizer-trait.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_FINALIZER_TRAIT_H_ #define INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_ #include <type_traits> #include "cppgc/type-traits.h" namespace cppgc { namespace internal { using FinalizationCallback = void ()(void); template <typename T, typename = void> struct HasFinalizeGarbageCollectedObject : std::false_type {}; template <typename T> struct HasFinalizeGarbageCollectedObject< T, std::void_t<decltype(std::declval<T>().FinalizeGarbageCollectedObject())>> : std::true_type {}; // The FinalizerTraitImpl specifies how to finalize objects. template <typename T, bool isFinalized> struct FinalizerTraitImpl; template <typename T> struct FinalizerTraitImpl<T, true> { private: // Dispatch to custom FinalizeGarbageCollectedObject(). struct Custom { static void Call(void* obj) { static_cast<T>(obj)->FinalizeGarbageCollectedObject(); } }; // Dispatch to regular destructor. struct Destructor { static void Call(void obj) { static_cast<T>(obj)->~T(); } }; using FinalizeImpl = std::conditional_t<HasFinalizeGarbageCollectedObject<T>::value, Custom, Destructor>; public: static void Finalize(void obj) { static_assert(sizeof(T), "T must be fully defined"); FinalizeImpl::Call(obj); } }; template <typename T> struct FinalizerTraitImpl<T, false> { static void Finalize(void* obj) { static_assert(sizeof(T), "T must be fully defined"); } }; // The FinalizerTrait is used to determine if a type requires finalization and // what finalization means. template <typename T> struct FinalizerTrait { private: // Object has a finalizer if it has // - a custom FinalizeGarbageCollectedObject method, or // - a destructor. static constexpr bool kNonTrivialFinalizer = internal::HasFinalizeGarbageCollectedObject<T>::value \|\| !std::is_trivially_destructible<typename std::remove_cv<T>::type>::value; static void Finalize(void* obj) { internal::FinalizerTraitImpl<T, kNonTrivialFinalizer>::Finalize(obj); } public: static constexpr bool HasFinalizer() { return kNonTrivialFinalizer; } // The callback used to finalize an object of type T. static constexpr FinalizationCallback kCallback = kNonTrivialFinalizer ? Finalize : nullptr; }; template <typename T> constexpr FinalizationCallback FinalizerTrait<T>::kCallback; } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_	2.59 KB	2025-02-28 19:16
📄 gc-info.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_GC_INFO_H_ #define INCLUDE_CPPGC_INTERNAL_GC_INFO_H_ #include <atomic> #include <cstdint> #include <type_traits> #include "cppgc/internal/finalizer-trait.h" #include "cppgc/internal/logging.h" #include "cppgc/internal/name-trait.h" #include "cppgc/trace-trait.h" #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { using GCInfoIndex = uint16_t; struct V8_EXPORT EnsureGCInfoIndexTrait final { // Acquires a new GC info object and updates `registered_index` with the index // that identifies that new info accordingly. template <typename T> V8_INLINE static void EnsureIndex( std::atomic<GCInfoIndex>& registered_index) { EnsureGCInfoIndexTraitDispatch<T>{}(registered_index); } private: template <typename T, bool = std::is_polymorphic<T>::value, bool = FinalizerTrait<T>::HasFinalizer(), bool = NameTrait<T>::HasNonHiddenName()> struct EnsureGCInfoIndexTraitDispatch; static void V8_PRESERVE_MOST EnsureGCInfoIndexPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback, FinalizationCallback, NameCallback); static void V8_PRESERVE_MOST EnsureGCInfoIndexPolymorphic( std::atomic<GCInfoIndex>&, TraceCallback, FinalizationCallback); static void V8_PRESERVE_MOST EnsureGCInfoIndexPolymorphic( std::atomic<GCInfoIndex>&, TraceCallback, NameCallback); static void V8_PRESERVE_MOST EnsureGCInfoIndexPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback); static void V8_PRESERVE_MOST EnsureGCInfoIndexNonPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback, FinalizationCallback, NameCallback); static void V8_PRESERVE_MOST EnsureGCInfoIndexNonPolymorphic( std::atomic<GCInfoIndex>&, TraceCallback, FinalizationCallback); static void V8_PRESERVE_MOST EnsureGCInfoIndexNonPolymorphic( std::atomic<GCInfoIndex>&, TraceCallback, NameCallback); static void V8_PRESERVE_MOST EnsureGCInfoIndexNonPolymorphic(std::atomic<GCInfoIndex>&, TraceCallback); }; #define DISPATCH(is_polymorphic, has_finalizer, has_non_hidden_name, function) \ template <typename T> \ struct EnsureGCInfoIndexTrait::EnsureGCInfoIndexTraitDispatch< \ T, is_polymorphic, has_finalizer, has_non_hidden_name> { \ V8_INLINE void operator()(std::atomic<GCInfoIndex>& registered_index) { \ function; \ } \ }; // --------------------------------------------------------------------- // // DISPATCH(is_polymorphic, has_finalizer, has_non_hidden_name, function) // --------------------------------------------------------------------- // DISPATCH(true, true, true, // EnsureGCInfoIndexPolymorphic(registered_index, // TraceTrait<T>::Trace, // FinalizerTrait<T>::kCallback, // NameTrait<T>::GetName)) // DISPATCH(true, true, false, // EnsureGCInfoIndexPolymorphic(registered_index, // TraceTrait<T>::Trace, // FinalizerTrait<T>::kCallback)) // DISPATCH(true, false, true, // EnsureGCInfoIndexPolymorphic(registered_index, // TraceTrait<T>::Trace, // NameTrait<T>::GetName)) // DISPATCH(true, false, false, // EnsureGCInfoIndexPolymorphic(registered_index, // TraceTrait<T>::Trace)) // DISPATCH(false, true, true, // EnsureGCInfoIndexNonPolymorphic(registered_index, // TraceTrait<T>::Trace, // FinalizerTrait<T>::kCallback, // NameTrait<T>::GetName)) // DISPATCH(false, true, false, // EnsureGCInfoIndexNonPolymorphic(registered_index, // TraceTrait<T>::Trace, // FinalizerTrait<T>::kCallback)) // DISPATCH(false, false, true, // EnsureGCInfoIndexNonPolymorphic(registered_index, // TraceTrait<T>::Trace, // NameTrait<T>::GetName)) // DISPATCH(false, false, false, // EnsureGCInfoIndexNonPolymorphic(registered_index, // TraceTrait<T>::Trace)) // #undef DISPATCH // Fold types based on finalizer behavior. Note that finalizer characteristics // align with trace behavior, i.e., destructors are virtual when trace methods // are and vice versa. template <typename T, typename ParentMostGarbageCollectedType> struct GCInfoFolding { static constexpr bool kHasVirtualDestructorAtBase = std::has_virtual_destructor<ParentMostGarbageCollectedType>::value; static constexpr bool kBothTypesAreTriviallyDestructible = std::is_trivially_destructible<ParentMostGarbageCollectedType>::value && std::is_trivially_destructible<T>::value; static constexpr bool kHasCustomFinalizerDispatchAtBase = internal::HasFinalizeGarbageCollectedObject< ParentMostGarbageCollectedType>::value; #ifdef CPPGC_SUPPORTS_OBJECT_NAMES static constexpr bool kWantsDetailedObjectNames = true; #else // !CPPGC_SUPPORTS_OBJECT_NAMES static constexpr bool kWantsDetailedObjectNames = false; #endif // !CPPGC_SUPPORTS_OBJECT_NAMES // Folding would regresses name resolution when deriving names from C++ // class names as it would just folds a name to the base class name. using ResultType = std::conditional_t<(kHasVirtualDestructorAtBase \|\| kBothTypesAreTriviallyDestructible \|\| kHasCustomFinalizerDispatchAtBase) && !kWantsDetailedObjectNames, ParentMostGarbageCollectedType, T>; }; // Trait determines how the garbage collector treats objects wrt. to traversing, // finalization, and naming. template <typename T> struct GCInfoTrait final { V8_INLINE static GCInfoIndex Index() { static_assert(sizeof(T), "T must be fully defined"); static std::atomic<GCInfoIndex> registered_index; // Uses zero initialization. GCInfoIndex index = registered_index.load(std::memory_order_acquire); if (V8_UNLIKELY(!index)) { EnsureGCInfoIndexTrait::EnsureIndex<T>(registered_index); // Slow path call uses V8_PRESERVE_MOST which does not support return // values (also preserves RAX). Avoid out parameter by just reloading the // value here which at this point is guaranteed to be set. index = registered_index.load(std::memory_order_acquire); CPPGC_DCHECK(index != 0); } return index; } }; } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_GC_INFO_H_	7.78 KB	2025-02-28 19:16
📄 logging.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_LOGGING_H_ #define INCLUDE_CPPGC_INTERNAL_LOGGING_H_ #include "cppgc/source-location.h" #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { void V8_EXPORT DCheckImpl(const char, const SourceLocation& = SourceLocation::Current()); [[noreturn]] void V8_EXPORT FatalImpl(const char, const SourceLocation& = SourceLocation::Current()); // Used to ignore -Wunused-variable. template <typename> struct EatParams {}; #if defined(DEBUG) #define CPPGC_DCHECK_MSG(condition, message) \ do { \ if (V8_UNLIKELY(!(condition))) { \ ::cppgc::internal::DCheckImpl(message); \ } \ } while (false) #else // !defined(DEBUG) #define CPPGC_DCHECK_MSG(condition, message) \ (static_cast<void>(::cppgc::internal::EatParams<decltype( \ static_cast<void>(condition), message)>{})) #endif // !defined(DEBUG) #define CPPGC_DCHECK(condition) CPPGC_DCHECK_MSG(condition, #condition) #define CPPGC_CHECK_MSG(condition, message) \ do { \ if (V8_UNLIKELY(!(condition))) { \ ::cppgc::internal::FatalImpl(message); \ } \ } while (false) #define CPPGC_CHECK(condition) CPPGC_CHECK_MSG(condition, #condition) } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_LOGGING_H_	1.66 KB	2025-02-28 19:16
📄 member-storage.h // Copyright 2022 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_MEMBER_STORAGE_H_ #define INCLUDE_CPPGC_INTERNAL_MEMBER_STORAGE_H_ #include <atomic> #include <cstddef> #include <type_traits> #include "cppgc/internal/api-constants.h" #include "cppgc/internal/logging.h" #include "cppgc/sentinel-pointer.h" #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { enum class WriteBarrierSlotType { kCompressed, kUncompressed, }; #if defined(CPPGC_POINTER_COMPRESSION) #if defined(__clang__) // Attribute const allows the compiler to assume that CageBaseGlobal::g_base_ // doesn't change (e.g. across calls) and thereby avoid redundant loads. #define CPPGC_CONST __attribute__((const)) #define CPPGC_REQUIRE_CONSTANT_INIT \ __attribute__((require_constant_initialization)) #else // defined(__clang__) #define CPPGC_CONST #define CPPGC_REQUIRE_CONSTANT_INIT #endif // defined(__clang__) class V8_EXPORT CageBaseGlobal final { public: V8_INLINE CPPGC_CONST static uintptr_t Get() { CPPGC_DCHECK(IsBaseConsistent()); return g_base_.base; } V8_INLINE CPPGC_CONST static bool IsSet() { CPPGC_DCHECK(IsBaseConsistent()); return (g_base_.base & ~kLowerHalfWordMask) != 0; } private: // We keep the lower halfword as ones to speed up decompression. static constexpr uintptr_t kLowerHalfWordMask = (api_constants::kCagedHeapReservationAlignment - 1); static union alignas(api_constants::kCachelineSize) Base { uintptr_t base; char cache_line[api_constants::kCachelineSize]; } g_base_ CPPGC_REQUIRE_CONSTANT_INIT; CageBaseGlobal() = delete; V8_INLINE static bool IsBaseConsistent() { return kLowerHalfWordMask == (g_base_.base & kLowerHalfWordMask); } friend class CageBaseGlobalUpdater; }; #undef CPPGC_REQUIRE_CONSTANT_INIT #undef CPPGC_CONST class V8_TRIVIAL_ABI CompressedPointer final { public: using IntegralType = uint32_t; static constexpr auto kWriteBarrierSlotType = WriteBarrierSlotType::kCompressed; V8_INLINE CompressedPointer() : value_(0u) {} V8_INLINE explicit CompressedPointer(const void* ptr) : value_(Compress(ptr)) {} V8_INLINE explicit CompressedPointer(std::nullptr_t) : value_(0u) {} V8_INLINE explicit CompressedPointer(SentinelPointer) : value_(kCompressedSentinel) {} V8_INLINE const void* Load() const { return Decompress(value_); } V8_INLINE const void* LoadAtomic() const { return Decompress( reinterpret_cast<const std::atomic<IntegralType>&>(value_).load( std::memory_order_relaxed)); } V8_INLINE void Store(const void* ptr) { value_ = Compress(ptr); } V8_INLINE void StoreAtomic(const void* value) { reinterpret_cast<std::atomic<IntegralType>&>(value_).store( Compress(value), std::memory_order_relaxed); } V8_INLINE void Clear() { value_ = 0u; } V8_INLINE bool IsCleared() const { return !value_; } V8_INLINE bool IsSentinel() const { return value_ == kCompressedSentinel; } V8_INLINE uint32_t GetAsInteger() const { return value_; } V8_INLINE friend bool operator==(CompressedPointer a, CompressedPointer b) { return a.value_ == b.value_; } V8_INLINE friend bool operator!=(CompressedPointer a, CompressedPointer b) { return a.value_ != b.value_; } V8_INLINE friend bool operator<(CompressedPointer a, CompressedPointer b) { return a.value_ < b.value_; } V8_INLINE friend bool operator<=(CompressedPointer a, CompressedPointer b) { return a.value_ <= b.value_; } V8_INLINE friend bool operator>(CompressedPointer a, CompressedPointer b) { return a.value_ > b.value_; } V8_INLINE friend bool operator>=(CompressedPointer a, CompressedPointer b) { return a.value_ >= b.value_; } static V8_INLINE IntegralType Compress(const void* ptr) { static_assert( SentinelPointer::kSentinelValue == 0b10, "The compression scheme relies on the sentinel encoded as 0b10"); static constexpr size_t kGigaCageMask = ~(api_constants::kCagedHeapReservationAlignment - 1); CPPGC_DCHECK(CageBaseGlobal::IsSet()); const uintptr_t base = CageBaseGlobal::Get(); CPPGC_DCHECK(!ptr \|\| ptr == kSentinelPointer \|\| (base & kGigaCageMask) == (reinterpret_cast<uintptr_t>(ptr) & kGigaCageMask)); #if defined(CPPGC_2GB_CAGE) // Truncate the pointer. auto compressed = static_cast<IntegralType>(reinterpret_cast<uintptr_t>(ptr)); #else // !defined(CPPGC_2GB_CAGE) const auto uptr = reinterpret_cast<uintptr_t>(ptr); // Shift the pointer by one and truncate. auto compressed = static_cast<IntegralType>(uptr >> 1); #endif // !defined(CPPGC_2GB_CAGE) // Normal compressed pointers must have the MSB set. CPPGC_DCHECK((!compressed \|\| compressed == kCompressedSentinel) \|\| (compressed & (1 << 31))); return compressed; } static V8_INLINE void* Decompress(IntegralType ptr) { CPPGC_DCHECK(CageBaseGlobal::IsSet()); const uintptr_t base = CageBaseGlobal::Get(); // Treat compressed pointer as signed and cast it to uint64_t, which will // sign-extend it. #if defined(CPPGC_2GB_CAGE) const uint64_t mask = static_cast<uint64_t>(static_cast<int32_t>(ptr)); #else // !defined(CPPGC_2GB_CAGE) // Then, shift the result by one. It's important to shift the unsigned // value, as otherwise it would result in undefined behavior. const uint64_t mask = static_cast<uint64_t>(static_cast<int32_t>(ptr)) << 1; #endif // !defined(CPPGC_2GB_CAGE) return reinterpret_cast<void>(mask & base); } private: #if defined(CPPGC_2GB_CAGE) static constexpr IntegralType kCompressedSentinel = SentinelPointer::kSentinelValue; #else // !defined(CPPGC_2GB_CAGE) static constexpr IntegralType kCompressedSentinel = SentinelPointer::kSentinelValue >> 1; #endif // !defined(CPPGC_2GB_CAGE) // All constructors initialize `value_`. Do not add a default value here as it // results in a non-atomic write on some builds, even when the atomic version // of the constructor is used. IntegralType value_; }; #endif // defined(CPPGC_POINTER_COMPRESSION) class V8_TRIVIAL_ABI RawPointer final { public: using IntegralType = uintptr_t; static constexpr auto kWriteBarrierSlotType = WriteBarrierSlotType::kUncompressed; V8_INLINE RawPointer() : ptr_(nullptr) {} V8_INLINE explicit RawPointer(const void ptr) : ptr_(ptr) {} V8_INLINE const void* Load() const { return ptr_; } V8_INLINE const void* LoadAtomic() const { return reinterpret_cast<const std::atomic<const void>&>(ptr_).load( std::memory_order_relaxed); } V8_INLINE void Store(const void ptr) { ptr_ = ptr; } V8_INLINE void StoreAtomic(const void* ptr) { reinterpret_cast<std::atomic<const void>&>(ptr_).store( ptr, std::memory_order_relaxed); } V8_INLINE void Clear() { ptr_ = nullptr; } V8_INLINE bool IsCleared() const { return !ptr_; } V8_INLINE bool IsSentinel() const { return ptr_ == kSentinelPointer; } V8_INLINE uintptr_t GetAsInteger() const { return reinterpret_cast<uintptr_t>(ptr_); } V8_INLINE friend bool operator==(RawPointer a, RawPointer b) { return a.ptr_ == b.ptr_; } V8_INLINE friend bool operator!=(RawPointer a, RawPointer b) { return a.ptr_ != b.ptr_; } V8_INLINE friend bool operator<(RawPointer a, RawPointer b) { return a.ptr_ < b.ptr_; } V8_INLINE friend bool operator<=(RawPointer a, RawPointer b) { return a.ptr_ <= b.ptr_; } V8_INLINE friend bool operator>(RawPointer a, RawPointer b) { return a.ptr_ > b.ptr_; } V8_INLINE friend bool operator>=(RawPointer a, RawPointer b) { return a.ptr_ >= b.ptr_; } private: // All constructors initialize `ptr_`. Do not add a default value here as it // results in a non-atomic write on some builds, even when the atomic version // of the constructor is used. const void ptr_; }; #if defined(CPPGC_POINTER_COMPRESSION) using DefaultMemberStorage = CompressedPointer; #else // !defined(CPPGC_POINTER_COMPRESSION) using DefaultMemberStorage = RawPointer; #endif // !defined(CPPGC_POINTER_COMPRESSION) } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_MEMBER_STORAGE_H_	8.24 KB	2025-02-28 19:16
📄 name-trait.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_NAME_TRAIT_H_ #define INCLUDE_CPPGC_INTERNAL_NAME_TRAIT_H_ #include <cstddef> #include <cstdint> #include <type_traits> #include "cppgc/name-provider.h" #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { #if CPPGC_SUPPORTS_OBJECT_NAMES && defined(__clang__) #define CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME 1 // Provides constexpr c-string storage for a name of fixed \|Size\| characters. // Automatically appends terminating 0 byte. template <size_t Size> struct NameBuffer { char name[Size + 1]{}; static constexpr NameBuffer FromCString(const char* str) { NameBuffer result; for (size_t i = 0; i < Size; ++i) result.name[i] = str[i]; result.name[Size] = 0; return result; } }; template <typename T> const char* GetTypename() { static constexpr char kSelfPrefix[] = "const char cppgc::internal::GetTypename() [T ="; static_assert(__builtin_strncmp(__PRETTY_FUNCTION__, kSelfPrefix, sizeof(kSelfPrefix) - 1) == 0, "The prefix must match"); static constexpr const char kTypenameStart = __PRETTY_FUNCTION__ + sizeof(kSelfPrefix); static constexpr size_t kTypenameSize = __builtin_strlen(__PRETTY_FUNCTION__) - sizeof(kSelfPrefix) - 1; // NameBuffer is an indirection that is needed to make sure that only a // substring of __PRETTY_FUNCTION__ gets materialized in the binary. static constexpr auto buffer = NameBuffer<kTypenameSize>::FromCString(kTypenameStart); return buffer.name; } #else #define CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME 0 #endif struct HeapObjectName { const char* value; bool name_was_hidden; }; enum class HeapObjectNameForUnnamedObject : uint8_t { kUseClassNameIfSupported, kUseHiddenName, }; class V8_EXPORT NameTraitBase { protected: static HeapObjectName GetNameFromTypeSignature(const char); }; // Trait that specifies how the garbage collector retrieves the name for a // given object. template <typename T> class NameTrait final : public NameTraitBase { public: static constexpr bool HasNonHiddenName() { #if CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME return true; #elif CPPGC_SUPPORTS_OBJECT_NAMES return true; #else // !CPPGC_SUPPORTS_OBJECT_NAMES return std::is_base_of<NameProvider, T>::value; #endif // !CPPGC_SUPPORTS_OBJECT_NAMES } static HeapObjectName GetName( const void obj, HeapObjectNameForUnnamedObject name_retrieval_mode) { return GetNameFor(static_cast<const T>(obj), name_retrieval_mode); } private: static HeapObjectName GetNameFor(const NameProvider name_provider, HeapObjectNameForUnnamedObject) { // Objects inheriting from `NameProvider` are not considered unnamed as // users already provided a name for them. return {name_provider->GetHumanReadableName(), false}; } static HeapObjectName GetNameFor( const void, HeapObjectNameForUnnamedObject name_retrieval_mode) { if (name_retrieval_mode == HeapObjectNameForUnnamedObject::kUseHiddenName) return {NameProvider::kHiddenName, true}; #if CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME return {GetTypename<T>(), false}; #elif CPPGC_SUPPORTS_OBJECT_NAMES #if defined(V8_CC_GNU) #define PRETTY_FUNCTION_VALUE __PRETTY_FUNCTION__ #elif defined(V8_CC_MSVC) #define PRETTY_FUNCTION_VALUE __FUNCSIG__ #else #define PRETTY_FUNCTION_VALUE nullptr #endif static const HeapObjectName leaky_name = GetNameFromTypeSignature(PRETTY_FUNCTION_VALUE); return leaky_name; #undef PRETTY_FUNCTION_VALUE #else // !CPPGC_SUPPORTS_OBJECT_NAMES return {NameProvider::kHiddenName, true}; #endif // !CPPGC_SUPPORTS_OBJECT_NAMES } }; using NameCallback = HeapObjectName ()(const void*, HeapObjectNameForUnnamedObject); } // namespace internal } // namespace cppgc #undef CPPGC_SUPPORTS_COMPILE_TIME_TYPENAME #endif // INCLUDE_CPPGC_INTERNAL_NAME_TRAIT_H_	4.08 KB	2025-02-28 19:16
📄 persistent-node.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_PERSISTENT_NODE_H_ #define INCLUDE_CPPGC_INTERNAL_PERSISTENT_NODE_H_ #include <array> #include <memory> #include <vector> #include "cppgc/internal/logging.h" #include "cppgc/trace-trait.h" #include "v8config.h" // NOLINT(build/include_directory) namespace cppgc { namespace internal { class CrossThreadPersistentRegion; class FatalOutOfMemoryHandler; class RootVisitor; // PersistentNode represents a variant of two states: // 1) traceable node with a back pointer to the Persistent object; // 2) freelist entry. class PersistentNode final { public: PersistentNode() = default; PersistentNode(const PersistentNode&) = delete; PersistentNode& operator=(const PersistentNode&) = delete; void InitializeAsUsedNode(void* owner, TraceRootCallback trace) { CPPGC_DCHECK(trace); owner_ = owner; trace_ = trace; } void InitializeAsFreeNode(PersistentNode* next) { next_ = next; trace_ = nullptr; } void UpdateOwner(void* owner) { CPPGC_DCHECK(IsUsed()); owner_ = owner; } PersistentNode* FreeListNext() const { CPPGC_DCHECK(!IsUsed()); return next_; } void Trace(RootVisitor& root_visitor) const { CPPGC_DCHECK(IsUsed()); trace_(root_visitor, owner_); } bool IsUsed() const { return trace_; } void* owner() const { CPPGC_DCHECK(IsUsed()); return owner_; } private: // PersistentNode acts as a designated union: // If trace_ != nullptr, owner_ points to the corresponding Persistent handle. // Otherwise, next_ points to the next freed PersistentNode. union { void* owner_ = nullptr; PersistentNode* next_; }; TraceRootCallback trace_ = nullptr; }; class V8_EXPORT PersistentRegionBase { using PersistentNodeSlots = std::array<PersistentNode, 256u>; public: // Clears Persistent fields to avoid stale pointers after heap teardown. ~PersistentRegionBase(); PersistentRegionBase(const PersistentRegionBase&) = delete; PersistentRegionBase& operator=(const PersistentRegionBase&) = delete; void Iterate(RootVisitor&); size_t NodesInUse() const; void ClearAllUsedNodes(); protected: explicit PersistentRegionBase(const FatalOutOfMemoryHandler& oom_handler); PersistentNode* TryAllocateNodeFromFreeList(void* owner, TraceRootCallback trace) { PersistentNode* node = nullptr; if (V8_LIKELY(free_list_head_)) { node = free_list_head_; free_list_head_ = free_list_head_->FreeListNext(); CPPGC_DCHECK(!node->IsUsed()); node->InitializeAsUsedNode(owner, trace); nodes_in_use_++; } return node; } void FreeNode(PersistentNode* node) { CPPGC_DCHECK(node); CPPGC_DCHECK(node->IsUsed()); node->InitializeAsFreeNode(free_list_head_); free_list_head_ = node; CPPGC_DCHECK(nodes_in_use_ > 0); nodes_in_use_--; } PersistentNode* RefillFreeListAndAllocateNode(void* owner, TraceRootCallback trace); private: template <typename PersistentBaseClass> void ClearAllUsedNodes(); void RefillFreeList(); std::vector<std::unique_ptr<PersistentNodeSlots>> nodes_; PersistentNode* free_list_head_ = nullptr; size_t nodes_in_use_ = 0; const FatalOutOfMemoryHandler& oom_handler_; friend class CrossThreadPersistentRegion; }; // Variant of PersistentRegionBase that checks whether the allocation and // freeing happens only on the thread that created the region. class V8_EXPORT PersistentRegion final : public PersistentRegionBase { public: explicit PersistentRegion(const FatalOutOfMemoryHandler&); // Clears Persistent fields to avoid stale pointers after heap teardown. ~PersistentRegion() = default; PersistentRegion(const PersistentRegion&) = delete; PersistentRegion& operator=(const PersistentRegion&) = delete; V8_INLINE PersistentNode* AllocateNode(void* owner, TraceRootCallback trace) { CPPGC_DCHECK(IsCreationThread()); auto* node = TryAllocateNodeFromFreeList(owner, trace); if (V8_LIKELY(node)) return node; // Slow path allocation allows for checking thread correspondence. CPPGC_CHECK(IsCreationThread()); return RefillFreeListAndAllocateNode(owner, trace); } V8_INLINE void FreeNode(PersistentNode* node) { CPPGC_DCHECK(IsCreationThread()); PersistentRegionBase::FreeNode(node); } private: bool IsCreationThread(); int creation_thread_id_; }; // CrossThreadPersistent uses PersistentRegionBase but protects it using this // lock when needed. class V8_EXPORT PersistentRegionLock final { public: PersistentRegionLock(); ~PersistentRegionLock(); static void AssertLocked(); }; // Variant of PersistentRegionBase that checks whether the PersistentRegionLock // is locked. class V8_EXPORT CrossThreadPersistentRegion final : protected PersistentRegionBase { public: explicit CrossThreadPersistentRegion(const FatalOutOfMemoryHandler&); // Clears Persistent fields to avoid stale pointers after heap teardown. ~CrossThreadPersistentRegion(); CrossThreadPersistentRegion(const CrossThreadPersistentRegion&) = delete; CrossThreadPersistentRegion& operator=(const CrossThreadPersistentRegion&) = delete; V8_INLINE PersistentNode* AllocateNode(void* owner, TraceRootCallback trace) { PersistentRegionLock::AssertLocked(); auto* node = TryAllocateNodeFromFreeList(owner, trace); if (V8_LIKELY(node)) return node; return RefillFreeListAndAllocateNode(owner, trace); } V8_INLINE void FreeNode(PersistentNode* node) { PersistentRegionLock::AssertLocked(); PersistentRegionBase::FreeNode(node); } void Iterate(RootVisitor&); size_t NodesInUse() const; void ClearAllUsedNodes(); }; } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_PERSISTENT_NODE_H_	5.89 KB	2025-02-28 19:16
📄 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_	8.34 KB	2025-02-28 19:16
📄 write-barrier.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_WRITE_BARRIER_H_ #define INCLUDE_CPPGC_INTERNAL_WRITE_BARRIER_H_ #include <cstddef> #include <cstdint> #include "cppgc/heap-handle.h" #include "cppgc/heap-state.h" #include "cppgc/internal/api-constants.h" #include "cppgc/internal/atomic-entry-flag.h" #include "cppgc/internal/base-page-handle.h" #include "cppgc/internal/member-storage.h" #include "cppgc/platform.h" #include "cppgc/sentinel-pointer.h" #include "cppgc/trace-trait.h" #include "v8config.h" // NOLINT(build/include_directory) #if defined(CPPGC_CAGED_HEAP) #include "cppgc/internal/caged-heap-local-data.h" #include "cppgc/internal/caged-heap.h" #endif namespace cppgc { class HeapHandle; namespace internal { #if defined(CPPGC_CAGED_HEAP) class WriteBarrierTypeForCagedHeapPolicy; #else // !CPPGC_CAGED_HEAP class WriteBarrierTypeForNonCagedHeapPolicy; #endif // !CPPGC_CAGED_HEAP class V8_EXPORT WriteBarrier final { public: enum class Type : uint8_t { kNone, kMarking, kGenerational, }; enum class GenerationalBarrierType : uint8_t { kPreciseSlot, kPreciseUncompressedSlot, kImpreciseSlot, }; struct Params { HeapHandle* heap = nullptr; #if V8_ENABLE_CHECKS Type type = Type::kNone; #endif // !V8_ENABLE_CHECKS #if defined(CPPGC_CAGED_HEAP) uintptr_t slot_offset = 0; uintptr_t value_offset = 0; #endif // CPPGC_CAGED_HEAP }; enum class ValueMode { kValuePresent, kNoValuePresent, }; // Returns the required write barrier for a given `slot` and `value`. static V8_INLINE Type GetWriteBarrierType(const void* slot, const void* value, Params& params); // Returns the required write barrier for a given `slot` and `value`. template <typename MemberStorage> static V8_INLINE Type GetWriteBarrierType(const void* slot, MemberStorage, Params& params); // Returns the required write barrier for a given `slot`. template <typename HeapHandleCallback> static V8_INLINE Type GetWriteBarrierType(const void* slot, Params& params, HeapHandleCallback callback); // Returns the required write barrier for a given `value`. static V8_INLINE Type GetWriteBarrierType(const void* value, Params& params); #ifdef CPPGC_SLIM_WRITE_BARRIER // A write barrier that combines `GenerationalBarrier()` and // `DijkstraMarkingBarrier()`. We only pass a single parameter here to clobber // as few registers as possible. template <WriteBarrierSlotType> static V8_NOINLINE void V8_PRESERVE_MOST CombinedWriteBarrierSlow(const void* slot); #endif // CPPGC_SLIM_WRITE_BARRIER static V8_INLINE void DijkstraMarkingBarrier(const Params& params, const void* object); static V8_INLINE void DijkstraMarkingBarrierRange( const Params& params, const void* first_element, size_t element_size, size_t number_of_elements, TraceCallback trace_callback); static V8_INLINE void SteeleMarkingBarrier(const Params& params, const void* object); #if defined(CPPGC_YOUNG_GENERATION) template <GenerationalBarrierType> static V8_INLINE void GenerationalBarrier(const Params& params, const void* slot); #else // !CPPGC_YOUNG_GENERATION template <GenerationalBarrierType> static V8_INLINE void GenerationalBarrier(const Params& params, const void* slot){} #endif // CPPGC_YOUNG_GENERATION #if V8_ENABLE_CHECKS static void CheckParams(Type expected_type, const Params& params); #else // !V8_ENABLE_CHECKS static void CheckParams(Type expected_type, const Params& params) {} #endif // !V8_ENABLE_CHECKS // The FlagUpdater class allows cppgc internal to update // \|write_barrier_enabled_\|. class FlagUpdater; static bool IsEnabled() { return write_barrier_enabled_.MightBeEntered(); } private: WriteBarrier() = delete; #if defined(CPPGC_CAGED_HEAP) using WriteBarrierTypePolicy = WriteBarrierTypeForCagedHeapPolicy; #else // !CPPGC_CAGED_HEAP using WriteBarrierTypePolicy = WriteBarrierTypeForNonCagedHeapPolicy; #endif // !CPPGC_CAGED_HEAP static void DijkstraMarkingBarrierSlow(const void* value); static void DijkstraMarkingBarrierSlowWithSentinelCheck(const void* value); static void DijkstraMarkingBarrierRangeSlow(HeapHandle& heap_handle, const void* first_element, size_t element_size, size_t number_of_elements, TraceCallback trace_callback); static void SteeleMarkingBarrierSlow(const void* value); static void SteeleMarkingBarrierSlowWithSentinelCheck(const void* value); #if defined(CPPGC_YOUNG_GENERATION) static CagedHeapLocalData& GetLocalData(HeapHandle&); static void GenerationalBarrierSlow(const CagedHeapLocalData& local_data, const AgeTable& age_table, const void* slot, uintptr_t value_offset, HeapHandle* heap_handle); static void GenerationalBarrierForUncompressedSlotSlow( const CagedHeapLocalData& local_data, const AgeTable& age_table, const void* slot, uintptr_t value_offset, HeapHandle* heap_handle); static void GenerationalBarrierForSourceObjectSlow( const CagedHeapLocalData& local_data, const void* object, HeapHandle* heap_handle); #endif // CPPGC_YOUNG_GENERATION static AtomicEntryFlag write_barrier_enabled_; }; template <WriteBarrier::Type type> V8_INLINE WriteBarrier::Type SetAndReturnType(WriteBarrier::Params& params) { if constexpr (type == WriteBarrier::Type::kNone) return WriteBarrier::Type::kNone; #if V8_ENABLE_CHECKS params.type = type; #endif // !V8_ENABLE_CHECKS return type; } #if defined(CPPGC_CAGED_HEAP) class V8_EXPORT WriteBarrierTypeForCagedHeapPolicy final { public: template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value, WriteBarrier::Params& params, HeapHandleCallback callback) { return ValueModeDispatch<value_mode>::Get(slot, value, params, callback); } template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback, typename MemberStorage> static V8_INLINE WriteBarrier::Type Get(const void* slot, MemberStorage value, WriteBarrier::Params& params, HeapHandleCallback callback) { return ValueModeDispatch<value_mode>::Get(slot, value, params, callback); } template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void* value, WriteBarrier::Params& params, HeapHandleCallback callback) { return GetNoSlot(value, params, callback); } private: WriteBarrierTypeForCagedHeapPolicy() = delete; template <typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type GetNoSlot(const void* value, WriteBarrier::Params& params, HeapHandleCallback) { const bool within_cage = CagedHeapBase::IsWithinCage(value); if (!within_cage) return WriteBarrier::Type::kNone; // We know that \|value\| points either within the normal page or to the // beginning of large-page, so extract the page header by bitmasking. BasePageHandle* page = BasePageHandle::FromPayload(const_cast<void>(value)); HeapHandle& heap_handle = page->heap_handle(); if (V8_UNLIKELY(heap_handle.is_incremental_marking_in_progress())) { return SetAndReturnType<WriteBarrier::Type::kMarking>(params); } return SetAndReturnType<WriteBarrier::Type::kNone>(params); } template <WriteBarrier::ValueMode value_mode> struct ValueModeDispatch; }; template <> struct WriteBarrierTypeForCagedHeapPolicy::ValueModeDispatch< WriteBarrier::ValueMode::kValuePresent> { template <typename HeapHandleCallback, typename MemberStorage> static V8_INLINE WriteBarrier::Type Get(const void slot, MemberStorage storage, WriteBarrier::Params& params, HeapHandleCallback) { if (V8_LIKELY(!WriteBarrier::IsEnabled())) return SetAndReturnType<WriteBarrier::Type::kNone>(params); return BarrierEnabledGet(slot, storage.Load(), params); } template <typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value, WriteBarrier::Params& params, HeapHandleCallback) { if (V8_LIKELY(!WriteBarrier::IsEnabled())) return SetAndReturnType<WriteBarrier::Type::kNone>(params); return BarrierEnabledGet(slot, value, params); } private: static V8_INLINE WriteBarrier::Type BarrierEnabledGet( const void* slot, const void* value, WriteBarrier::Params& params) { const bool within_cage = CagedHeapBase::AreWithinCage(slot, value); if (!within_cage) return WriteBarrier::Type::kNone; // We know that \|value\| points either within the normal page or to the // beginning of large-page, so extract the page header by bitmasking. BasePageHandle* page = BasePageHandle::FromPayload(const_cast<void>(value)); HeapHandle& heap_handle = page->heap_handle(); if (V8_LIKELY(!heap_handle.is_incremental_marking_in_progress())) { #if defined(CPPGC_YOUNG_GENERATION) if (!heap_handle.is_young_generation_enabled()) return WriteBarrier::Type::kNone; params.heap = &heap_handle; params.slot_offset = CagedHeapBase::OffsetFromAddress(slot); params.value_offset = CagedHeapBase::OffsetFromAddress(value); return SetAndReturnType<WriteBarrier::Type::kGenerational>(params); #else // !CPPGC_YOUNG_GENERATION return SetAndReturnType<WriteBarrier::Type::kNone>(params); #endif // !CPPGC_YOUNG_GENERATION } // Use marking barrier. params.heap = &heap_handle; return SetAndReturnType<WriteBarrier::Type::kMarking>(params); } }; template <> struct WriteBarrierTypeForCagedHeapPolicy::ValueModeDispatch< WriteBarrier::ValueMode::kNoValuePresent> { template <typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void slot, const void, WriteBarrier::Params& params, HeapHandleCallback callback) { if (V8_LIKELY(!WriteBarrier::IsEnabled())) return SetAndReturnType<WriteBarrier::Type::kNone>(params); HeapHandle& handle = callback(); #if defined(CPPGC_YOUNG_GENERATION) if (V8_LIKELY(!handle.is_incremental_marking_in_progress())) { if (!handle.is_young_generation_enabled()) { return WriteBarrier::Type::kNone; } params.heap = &handle; // Check if slot is on stack. if (V8_UNLIKELY(!CagedHeapBase::IsWithinCage(slot))) { return SetAndReturnType<WriteBarrier::Type::kNone>(params); } params.slot_offset = CagedHeapBase::OffsetFromAddress(slot); return SetAndReturnType<WriteBarrier::Type::kGenerational>(params); } #else // !defined(CPPGC_YOUNG_GENERATION) if (V8_UNLIKELY(!handle.is_incremental_marking_in_progress())) { return SetAndReturnType<WriteBarrier::Type::kNone>(params); } #endif // !defined(CPPGC_YOUNG_GENERATION) params.heap = &handle; return SetAndReturnType<WriteBarrier::Type::kMarking>(params); } }; #endif // CPPGC_CAGED_HEAP class V8_EXPORT WriteBarrierTypeForNonCagedHeapPolicy final { public: template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void slot, const void* value, WriteBarrier::Params& params, HeapHandleCallback callback) { return ValueModeDispatch<value_mode>::Get(slot, value, params, callback); } template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void* slot, RawPointer value, WriteBarrier::Params& params, HeapHandleCallback callback) { return ValueModeDispatch<value_mode>::Get(slot, value.Load(), params, callback); } template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void* value, WriteBarrier::Params& params, HeapHandleCallback callback) { // The slot will never be used in `Get()` below. return Get<WriteBarrier::ValueMode::kValuePresent>(nullptr, value, params, callback); } private: template <WriteBarrier::ValueMode value_mode> struct ValueModeDispatch; WriteBarrierTypeForNonCagedHeapPolicy() = delete; }; template <> struct WriteBarrierTypeForNonCagedHeapPolicy::ValueModeDispatch< WriteBarrier::ValueMode::kValuePresent> { template <typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void, const void object, WriteBarrier::Params& params, HeapHandleCallback callback) { // The following check covers nullptr as well as sentinel pointer. if (object <= static_cast<void>(kSentinelPointer)) { return SetAndReturnType<WriteBarrier::Type::kNone>(params); } if (V8_LIKELY(!WriteBarrier::IsEnabled())) { return SetAndReturnType<WriteBarrier::Type::kNone>(params); } // We know that \|object\| is within the normal page or in the beginning of a // large page, so extract the page header by bitmasking. BasePageHandle page = BasePageHandle::FromPayload(const_cast<void>(object)); HeapHandle& heap_handle = page->heap_handle(); if (V8_LIKELY(heap_handle.is_incremental_marking_in_progress())) { return SetAndReturnType<WriteBarrier::Type::kMarking>(params); } return SetAndReturnType<WriteBarrier::Type::kNone>(params); } }; template <> struct WriteBarrierTypeForNonCagedHeapPolicy::ValueModeDispatch< WriteBarrier::ValueMode::kNoValuePresent> { template <typename HeapHandleCallback> static V8_INLINE WriteBarrier::Type Get(const void, const void, WriteBarrier::Params& params, HeapHandleCallback callback) { if (V8_UNLIKELY(WriteBarrier::IsEnabled())) { HeapHandle& handle = callback(); if (V8_LIKELY(handle.is_incremental_marking_in_progress())) { params.heap = &handle; return SetAndReturnType<WriteBarrier::Type::kMarking>(params); } } return WriteBarrier::Type::kNone; } }; // static WriteBarrier::Type WriteBarrier::GetWriteBarrierType( const void slot, const void* value, WriteBarrier::Params& params) { return WriteBarrierTypePolicy::Get<ValueMode::kValuePresent>(slot, value, params, []() {}); } // static template <typename MemberStorage> WriteBarrier::Type WriteBarrier::GetWriteBarrierType( const void* slot, MemberStorage value, WriteBarrier::Params& params) { return WriteBarrierTypePolicy::Get<ValueMode::kValuePresent>(slot, value, params, []() {}); } // static template <typename HeapHandleCallback> WriteBarrier::Type WriteBarrier::GetWriteBarrierType( const void* slot, WriteBarrier::Params& params, HeapHandleCallback callback) { return WriteBarrierTypePolicy::Get<ValueMode::kNoValuePresent>( slot, nullptr, params, callback); } // static WriteBarrier::Type WriteBarrier::GetWriteBarrierType( const void* value, WriteBarrier::Params& params) { return WriteBarrierTypePolicy::Get<ValueMode::kValuePresent>(value, params, []() {}); } // static void WriteBarrier::DijkstraMarkingBarrier(const Params& params, const void* object) { CheckParams(Type::kMarking, params); #if defined(CPPGC_CAGED_HEAP) // Caged heap already filters out sentinels. DijkstraMarkingBarrierSlow(object); #else // !CPPGC_CAGED_HEAP DijkstraMarkingBarrierSlowWithSentinelCheck(object); #endif // !CPPGC_CAGED_HEAP } // static void WriteBarrier::DijkstraMarkingBarrierRange(const Params& params, const void* first_element, size_t element_size, size_t number_of_elements, TraceCallback trace_callback) { CheckParams(Type::kMarking, params); DijkstraMarkingBarrierRangeSlow(params.heap, first_element, element_size, number_of_elements, trace_callback); } // static void WriteBarrier::SteeleMarkingBarrier(const Params& params, const void object) { CheckParams(Type::kMarking, params); #if defined(CPPGC_CAGED_HEAP) // Caged heap already filters out sentinels. SteeleMarkingBarrierSlow(object); #else // !CPPGC_CAGED_HEAP SteeleMarkingBarrierSlowWithSentinelCheck(object); #endif // !CPPGC_CAGED_HEAP } #if defined(CPPGC_YOUNG_GENERATION) // static template <WriteBarrier::GenerationalBarrierType type> void WriteBarrier::GenerationalBarrier(const Params& params, const void* slot) { CheckParams(Type::kGenerational, params); const CagedHeapLocalData& local_data = CagedHeapLocalData::Get(); const AgeTable& age_table = local_data.age_table; // Bail out if the slot (precise or imprecise) is in young generation. if (V8_LIKELY(age_table.GetAge(params.slot_offset) == AgeTable::Age::kYoung)) return; // Dispatch between different types of barriers. // TODO(chromium:1029379): Consider reload local_data in the slow path to // reduce register pressure. if constexpr (type == GenerationalBarrierType::kPreciseSlot) { GenerationalBarrierSlow(local_data, age_table, slot, params.value_offset, params.heap); } else if constexpr (type == GenerationalBarrierType::kPreciseUncompressedSlot) { GenerationalBarrierForUncompressedSlotSlow( local_data, age_table, slot, params.value_offset, params.heap); } else { GenerationalBarrierForSourceObjectSlow(local_data, slot, params.heap); } } #endif // !CPPGC_YOUNG_GENERATION } // namespace internal } // namespace cppgc #endif // INCLUDE_CPPGC_INTERNAL_WRITE_BARRIER_H_	19.09 KB	2025-02-28 19:16

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