#pragma once
#include "GCAssertions.h"
#include "HandleTypes.h"
#include <type_traits>
#include <wtf/DumbPtrTraits.h>
#include <wtf/DumbValueTraits.h>
namespace JSC {
namespace DFG {
class DesiredWriteBarrier;
}
class JSCell;
class VM;
class JSGlobalObject;
template<class T>
using WriteBarrierTraitsSelect = typename std::conditional<std::is_same<T, Unknown>::value,
DumbValueTraits<T>, DumbPtrTraits<T>
>::type;
template<class T, typename Traits = WriteBarrierTraitsSelect<T>> class WriteBarrierBase;
template<> class WriteBarrierBase<JSValue>;
JS_EXPORT_PRIVATE void slowValidateCell(JSCell*);
JS_EXPORT_PRIVATE void slowValidateCell(JSGlobalObject*);
#if ENABLE(GC_VALIDATION)
template<class T> inline void validateCell(T cell)
{
ASSERT_GC_OBJECT_INHERITS(cell, std::remove_pointer<T>::type::info());
}
template<> inline void validateCell<JSCell*>(JSCell* cell)
{
slowValidateCell(cell);
}
template<> inline void validateCell<JSGlobalObject*>(JSGlobalObject* globalObject)
{
slowValidateCell(globalObject);
}
#else
template<class T> inline void validateCell(T)
{
}
#endif
template <typename T, typename Traits> class WriteBarrierBase {
using StorageType = typename Traits::StorageType;
public:
void set(VM&, const JSCell* owner, T* value);
void copyFrom(const WriteBarrierBase& other)
{
Traits::exchange(m_cell, other.m_cell);
}
void setMayBeNull(VM&, const JSCell* owner, T* value);
void setEarlyValue(VM&, const JSCell* owner, T* value);
T* get() const
{
StorageType cell = m_cell;
if (cell)
validateCell(reinterpret_cast<JSCell*>(static_cast<void*>(Traits::unwrap(cell))));
return Traits::unwrap(cell);
}
T* operator*() const
{
StorageType cell = m_cell;
ASSERT(cell);
auto unwrapped = Traits::unwrap(cell);
validateCell<T>(unwrapped);
return Traits::unwrap(unwrapped);
}
T* operator->() const
{
StorageType cell = m_cell;
ASSERT(cell);
auto unwrapped = Traits::unwrap(cell);
validateCell(unwrapped);
return unwrapped;
}
void clear() { Traits::exchange(m_cell, nullptr); }
template<typename BarrierT, typename BarrierTraits, std::enable_if_t<std::is_same<BarrierTraits, DumbPtrTraits<BarrierT>>::value, void*> = nullptr>
struct SlotHelper {
static BarrierT** reinterpret(typename BarrierTraits::StorageType* cell) { return reinterpret_cast<T**>(cell); }
};
T** slot()
{
return SlotHelper<T, Traits>::reinterpret(&m_cell);
}
explicit operator bool() const { return !!m_cell; }
bool operator!() const { return !m_cell; }
void setWithoutWriteBarrier(T* value)
{
#if ENABLE(WRITE_BARRIER_PROFILING)
WriteBarrierCounters::usesWithoutBarrierFromCpp.count();
#endif
Traits::exchange(this->m_cell, value);
}
T* unvalidatedGet() const { return Traits::unwrap(m_cell); }
private:
StorageType m_cell;
};
template <> class WriteBarrierBase<Unknown, DumbValueTraits<Unknown>> {
public:
void set(VM&, const JSCell* owner, JSValue);
void setWithoutWriteBarrier(JSValue value)
{
m_value = JSValue::encode(value);
}
JSValue get() const
{
return JSValue::decode(m_value);
}
void clear() { m_value = JSValue::encode(JSValue()); }
void setUndefined() { m_value = JSValue::encode(jsUndefined()); }
void setStartingValue(JSValue value) { m_value = JSValue::encode(value); }
bool isNumber() const { return get().isNumber(); }
bool isInt32() const { return get().isInt32(); }
bool isObject() const { return get().isObject(); }
bool isNull() const { return get().isNull(); }
bool isGetterSetter() const { return get().isGetterSetter(); }
bool isCustomGetterSetter() const { return get().isCustomGetterSetter(); }
JSValue* slot() const
{
return bitwise_cast<JSValue*>(&m_value);
}
int32_t* tagPointer() { return &bitwise_cast<EncodedValueDescriptor*>(&m_value)->asBits.tag; }
int32_t* payloadPointer() { return &bitwise_cast<EncodedValueDescriptor*>(&m_value)->asBits.payload; }
explicit operator bool() const { return !!get(); }
bool operator!() const { return !get(); }
private:
EncodedJSValue m_value;
};
template <typename T, typename Traits = WriteBarrierTraitsSelect<T>>
class WriteBarrier : public WriteBarrierBase<T, Traits> {
WTF_MAKE_FAST_ALLOCATED;
public:
WriteBarrier()
{
this->setWithoutWriteBarrier(0);
}
WriteBarrier(VM& vm, const JSCell* owner, T* value)
{
this->set(vm, owner, value);
}
WriteBarrier(DFG::DesiredWriteBarrier&, T* value)
{
ASSERT(isCompilationThread());
this->setWithoutWriteBarrier(value);
}
enum MayBeNullTag { MayBeNull };
WriteBarrier(VM& vm, const JSCell* owner, T* value, MayBeNullTag)
{
this->setMayBeNull(vm, owner, value);
}
};
enum UndefinedWriteBarrierTagType { UndefinedWriteBarrierTag };
template <>
class WriteBarrier<Unknown, DumbValueTraits<Unknown>> : public WriteBarrierBase<Unknown, DumbValueTraits<Unknown>> {
WTF_MAKE_FAST_ALLOCATED;
public:
WriteBarrier()
{
this->setWithoutWriteBarrier(JSValue());
}
WriteBarrier(UndefinedWriteBarrierTagType)
{
this->setWithoutWriteBarrier(jsUndefined());
}
WriteBarrier(VM& vm, const JSCell* owner, JSValue value)
{
this->set(vm, owner, value);
}
WriteBarrier(DFG::DesiredWriteBarrier&, JSValue value)
{
ASSERT(isCompilationThread());
this->setWithoutWriteBarrier(value);
}
};
template <typename U, typename V, typename TraitsU, typename TraitsV>
inline bool operator==(const WriteBarrierBase<U, TraitsU>& lhs, const WriteBarrierBase<V, TraitsV>& rhs)
{
return lhs.get() == rhs.get();
}
}