StructureTransitionTable.h [plain text]
#pragma once
#include "IndexingType.h"
#include "WeakGCMap.h"
#include <wtf/HashFunctions.h>
#include <wtf/text/UniquedStringImpl.h>
namespace JSC {
class JSCell;
class Structure;
static const unsigned FirstInternalAttribute = 1 << 6;
enum class NonPropertyTransition : unsigned {
AllocateUndecided,
AllocateInt32,
AllocateDouble,
AllocateContiguous,
AllocateArrayStorage,
AllocateSlowPutArrayStorage,
SwitchToSlowPutArrayStorage,
AddIndexedAccessors,
PreventExtensions,
Seal,
Freeze
};
inline unsigned toAttributes(NonPropertyTransition transition)
{
return static_cast<unsigned>(transition) + FirstInternalAttribute;
}
inline bool changesIndexingType(NonPropertyTransition transition)
{
switch (transition) {
case NonPropertyTransition::AllocateUndecided:
case NonPropertyTransition::AllocateInt32:
case NonPropertyTransition::AllocateDouble:
case NonPropertyTransition::AllocateContiguous:
case NonPropertyTransition::AllocateArrayStorage:
case NonPropertyTransition::AllocateSlowPutArrayStorage:
case NonPropertyTransition::SwitchToSlowPutArrayStorage:
case NonPropertyTransition::AddIndexedAccessors:
return true;
default:
return false;
}
}
inline IndexingType newIndexingType(IndexingType oldType, NonPropertyTransition transition)
{
switch (transition) {
case NonPropertyTransition::AllocateUndecided:
ASSERT(!hasIndexedProperties(oldType));
return oldType | UndecidedShape;
case NonPropertyTransition::AllocateInt32:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType));
return (oldType & ~IndexingShapeMask) | Int32Shape;
case NonPropertyTransition::AllocateDouble:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType));
return (oldType & ~IndexingShapeMask) | DoubleShape;
case NonPropertyTransition::AllocateContiguous:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType));
return (oldType & ~IndexingShapeMask) | ContiguousShape;
case NonPropertyTransition::AllocateArrayStorage:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType) || hasContiguous(oldType));
return (oldType & ~IndexingShapeMask) | ArrayStorageShape;
case NonPropertyTransition::AllocateSlowPutArrayStorage:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType) || hasContiguous(oldType) || hasContiguous(oldType));
return (oldType & ~IndexingShapeMask) | SlowPutArrayStorageShape;
case NonPropertyTransition::SwitchToSlowPutArrayStorage:
ASSERT(hasArrayStorage(oldType));
return (oldType & ~IndexingShapeMask) | SlowPutArrayStorageShape;
case NonPropertyTransition::AddIndexedAccessors:
return oldType | MayHaveIndexedAccessors;
default:
return oldType;
}
}
inline bool preventsExtensions(NonPropertyTransition transition)
{
switch (transition) {
case NonPropertyTransition::PreventExtensions:
case NonPropertyTransition::Seal:
case NonPropertyTransition::Freeze:
return true;
default:
return false;
}
}
inline bool setsDontDeleteOnAllProperties(NonPropertyTransition transition)
{
switch (transition) {
case NonPropertyTransition::Seal:
case NonPropertyTransition::Freeze:
return true;
default:
return false;
}
}
inline bool setsReadOnlyOnNonAccessorProperties(NonPropertyTransition transition)
{
switch (transition) {
case NonPropertyTransition::Freeze:
return true;
default:
return false;
}
}
class StructureTransitionTable {
static const intptr_t UsingSingleSlotFlag = 1;
struct Hash {
typedef std::pair<UniquedStringImpl*, unsigned> Key;
static unsigned hash(const Key& p)
{
return PtrHash<UniquedStringImpl*>::hash(p.first) + p.second;
}
static bool equal(const Key& a, const Key& b)
{
return a == b;
}
static const bool safeToCompareToEmptyOrDeleted = true;
};
typedef WeakGCMap<Hash::Key, Structure, Hash> TransitionMap;
public:
StructureTransitionTable()
: m_data(UsingSingleSlotFlag)
{
}
~StructureTransitionTable()
{
if (!isUsingSingleSlot()) {
delete map();
return;
}
WeakImpl* impl = this->weakImpl();
if (!impl)
return;
WeakSet::deallocate(impl);
}
void add(VM&, Structure*);
bool contains(UniquedStringImpl*, unsigned attributes) const;
Structure* get(UniquedStringImpl*, unsigned attributes) const;
private:
friend class SingleSlotTransitionWeakOwner;
bool isUsingSingleSlot() const
{
return m_data & UsingSingleSlotFlag;
}
TransitionMap* map() const
{
ASSERT(!isUsingSingleSlot());
return reinterpret_cast<TransitionMap*>(m_data);
}
WeakImpl* weakImpl() const
{
ASSERT(isUsingSingleSlot());
return reinterpret_cast<WeakImpl*>(m_data & ~UsingSingleSlotFlag);
}
void setMap(TransitionMap* map)
{
ASSERT(isUsingSingleSlot());
if (WeakImpl* impl = this->weakImpl())
WeakSet::deallocate(impl);
m_data = reinterpret_cast<intptr_t>(map);
ASSERT(!isUsingSingleSlot());
}
Structure* singleTransition() const;
void setSingleTransition(Structure*);
intptr_t m_data;
};
}