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// 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_HEAP_CONSISTENCY_H_
#define INCLUDE_CPPGC_HEAP_CONSISTENCY_H_
#include <cstddef>
#include "cppgc/internal/write-barrier.h"
#include "cppgc/macros.h"
#include "cppgc/member.h"
#include "cppgc/trace-trait.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
class HeapHandle;
namespace subtle {
/**
* **DO NOT USE: Use the appropriate managed types.**
*
* Consistency helpers that aid in maintaining a consistent internal state of
* the garbage collector.
*/
class HeapConsistency final {
public:
using WriteBarrierParams = internal::WriteBarrier::Params;
using WriteBarrierType = internal::WriteBarrier::Type;
/**
* Gets the required write barrier type for a specific write.
*
* \param slot Slot containing the pointer to the object. The slot itself
* must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
* \param value The pointer to the object. May be an interior pointer to an
* interface of the actual object.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
static V8_INLINE WriteBarrierType GetWriteBarrierType(
const void* slot, const void* value, WriteBarrierParams& params) {
return internal::WriteBarrier::GetWriteBarrierType(slot, value, params);
}
/**
* Gets the required write barrier type for a specific write. This override is
* only used for all the BasicMember types.
*
* \param slot Slot containing the pointer to the object. The slot itself
* must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
* \param value The pointer to the object held via `BasicMember`.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,
typename CheckingPolicy, typename StorageType>
static V8_INLINE WriteBarrierType GetWriteBarrierType(
const internal::BasicMember<T, WeaknessTag, WriteBarrierPolicy,
CheckingPolicy, StorageType>& value,
WriteBarrierParams& params) {
return internal::WriteBarrier::GetWriteBarrierType(
value.GetRawSlot(), value.GetRawStorage(), params);
}
/**
* Gets the required write barrier type for a specific write.
*
* \param slot Slot to some part of an object. The object must not necessarily
have been allocated using `MakeGarbageCollected()` but can also live
off-heap or on stack.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \param callback Callback returning the corresponding heap handle. The
* callback is only invoked if the heap cannot otherwise be figured out. The
* callback must not allocate.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrierType
GetWriteBarrierType(const void* slot, WriteBarrierParams& params,
HeapHandleCallback callback) {
return internal::WriteBarrier::GetWriteBarrierType(slot, params, callback);
}
/**
* Gets the required write barrier type for a specific write.
* This version is meant to be used in conjunction with with a marking write
* barrier barrier which doesn't consider the slot.
*
* \param value The pointer to the object. May be an interior pointer to an
* interface of the actual object.
* \param params Parameters that may be used for actual write barrier calls.
* Only filled if return value indicates that a write barrier is needed. The
* contents of the `params` are an implementation detail.
* \returns whether a write barrier is needed and which barrier to invoke.
*/
static V8_INLINE WriteBarrierType
GetWriteBarrierType(const void* value, WriteBarrierParams& params) {
return internal::WriteBarrier::GetWriteBarrierType(value, params);
}
/**
* Conservative Dijkstra-style write barrier that processes an object if it
* has not yet been processed.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param object The pointer to the object. May be an interior pointer to a
* an interface of the actual object.
*/
static V8_INLINE void DijkstraWriteBarrier(const WriteBarrierParams& params,
const void* object) {
internal::WriteBarrier::DijkstraMarkingBarrier(params, object);
}
/**
* Conservative Dijkstra-style write barrier that processes a range of
* elements if they have not yet been processed.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param first_element Pointer to the first element that should be processed.
* The slot itself must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
* \param element_size Size of the element in bytes.
* \param number_of_elements Number of elements that should be processed,
* starting with `first_element`.
* \param trace_callback The trace callback that should be invoked for each
* element if necessary.
*/
static V8_INLINE void DijkstraWriteBarrierRange(
const WriteBarrierParams& params, const void* first_element,
size_t element_size, size_t number_of_elements,
TraceCallback trace_callback) {
internal::WriteBarrier::DijkstraMarkingBarrierRange(
params, first_element, element_size, number_of_elements,
trace_callback);
}
/**
* Steele-style write barrier that re-processes an object if it has already
* been processed.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param object The pointer to the object which must point to an object that
* has been allocated using `MakeGarbageCollected()`. Interior pointers are
* not supported.
*/
static V8_INLINE void SteeleWriteBarrier(const WriteBarrierParams& params,
const void* object) {
internal::WriteBarrier::SteeleMarkingBarrier(params, object);
}
/**
* Generational barrier for maintaining consistency when running with multiple
* generations.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param slot Slot containing the pointer to the object. The slot itself
* must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
*/
static V8_INLINE void GenerationalBarrier(const WriteBarrierParams& params,
const void* slot) {
internal::WriteBarrier::GenerationalBarrier<
internal::WriteBarrier::GenerationalBarrierType::kPreciseSlot>(params,
slot);
}
/**
* Generational barrier for maintaining consistency when running with multiple
* generations. This version is used when slot contains uncompressed pointer.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param slot Uncompressed slot containing the direct pointer to the object.
* The slot itself must reside in an object that has been allocated using
* `MakeGarbageCollected()`.
*/
static V8_INLINE void GenerationalBarrierForUncompressedSlot(
const WriteBarrierParams& params, const void* uncompressed_slot) {
internal::WriteBarrier::GenerationalBarrier<
internal::WriteBarrier::GenerationalBarrierType::
kPreciseUncompressedSlot>(params, uncompressed_slot);
}
/**
* Generational barrier for source object that may contain outgoing pointers
* to objects in young generation.
*
* \param params The parameters retrieved from `GetWriteBarrierType()`.
* \param inner_pointer Pointer to the source object.
*/
static V8_INLINE void GenerationalBarrierForSourceObject(
const WriteBarrierParams& params, const void* inner_pointer) {
internal::WriteBarrier::GenerationalBarrier<
internal::WriteBarrier::GenerationalBarrierType::kImpreciseSlot>(
params, inner_pointer);
}
private:
HeapConsistency() = delete;
};
/**
* Disallows garbage collection finalizations. Any garbage collection triggers
* result in a crash when in this scope.
*
* Note that the garbage collector already covers paths that can lead to garbage
* collections, so user code does not require checking
* `IsGarbageCollectionAllowed()` before allocations.
*/
class V8_EXPORT V8_NODISCARD DisallowGarbageCollectionScope final {
CPPGC_STACK_ALLOCATED();
public:
/**
* \returns whether garbage collections are currently allowed.
*/
static bool IsGarbageCollectionAllowed(HeapHandle& heap_handle);
/**
* Enters a disallow garbage collection scope. Must be paired with `Leave()`.
* Prefer a scope instance of `DisallowGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Enter(HeapHandle& heap_handle);
/**
* Leaves a disallow garbage collection scope. Must be paired with `Enter()`.
* Prefer a scope instance of `DisallowGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Leave(HeapHandle& heap_handle);
/**
* Constructs a scoped object that automatically enters and leaves a disallow
* garbage collection scope based on its lifetime.
*
* \param heap_handle The corresponding heap.
*/
explicit DisallowGarbageCollectionScope(HeapHandle& heap_handle);
~DisallowGarbageCollectionScope();
DisallowGarbageCollectionScope(const DisallowGarbageCollectionScope&) =
delete;
DisallowGarbageCollectionScope& operator=(
const DisallowGarbageCollectionScope&) = delete;
private:
HeapHandle& heap_handle_;
};
/**
* Avoids invoking garbage collection finalizations. Already running garbage
* collection phase are unaffected by this scope.
*
* Should only be used temporarily as the scope has an impact on memory usage
* and follow up garbage collections.
*/
class V8_EXPORT V8_NODISCARD NoGarbageCollectionScope final {
CPPGC_STACK_ALLOCATED();
public:
/**
* Enters a no garbage collection scope. Must be paired with `Leave()`. Prefer
* a scope instance of `NoGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Enter(HeapHandle& heap_handle);
/**
* Leaves a no garbage collection scope. Must be paired with `Enter()`. Prefer
* a scope instance of `NoGarbageCollectionScope`.
*
* \param heap_handle The corresponding heap.
*/
static void Leave(HeapHandle& heap_handle);
/**
* Constructs a scoped object that automatically enters and leaves a no
* garbage collection scope based on its lifetime.
*
* \param heap_handle The corresponding heap.
*/
explicit NoGarbageCollectionScope(HeapHandle& heap_handle);
~NoGarbageCollectionScope();
NoGarbageCollectionScope(const NoGarbageCollectionScope&) = delete;
NoGarbageCollectionScope& operator=(const NoGarbageCollectionScope&) = delete;
private:
HeapHandle& heap_handle_;
};
} // namespace subtle
} // namespace cppgc
#endif // INCLUDE_CPPGC_HEAP_CONSISTENCY_H_