StructureTransitionTable.h [plain text]
#ifndef StructureTransitionTable_h
#define StructureTransitionTable_h
#include "IndexingType.h"
#include "WeakGCMap.h"
#include <wtf/HashFunctions.h>
#include <wtf/OwnPtr.h>
#include <wtf/text/StringImpl.h>
namespace JSC {
class JSCell;
class Structure;
static const unsigned FirstInternalAttribute = 1 << 6;
enum NonPropertyTransition {
AllocateUndecided,
AllocateInt32,
AllocateDouble,
AllocateContiguous,
AllocateArrayStorage,
AllocateSlowPutArrayStorage,
SwitchToSlowPutArrayStorage,
AddIndexedAccessors
};
inline unsigned toAttributes(NonPropertyTransition transition)
{
return transition + FirstInternalAttribute;
}
inline IndexingType newIndexingType(IndexingType oldType, NonPropertyTransition transition)
{
switch (transition) {
case AllocateUndecided:
ASSERT(!hasIndexedProperties(oldType));
return oldType | UndecidedShape;
case AllocateInt32:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType));
return (oldType & ~IndexingShapeMask) | Int32Shape;
case AllocateDouble:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType));
return (oldType & ~IndexingShapeMask) | DoubleShape;
case AllocateContiguous:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType));
return (oldType & ~IndexingShapeMask) | ContiguousShape;
case AllocateArrayStorage:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType) || hasContiguous(oldType));
return (oldType & ~IndexingShapeMask) | ArrayStorageShape;
case AllocateSlowPutArrayStorage:
ASSERT(!hasIndexedProperties(oldType) || hasUndecided(oldType) || hasInt32(oldType) || hasDouble(oldType) || hasContiguous(oldType) || hasContiguous(oldType));
return (oldType & ~IndexingShapeMask) | SlowPutArrayStorageShape;
case SwitchToSlowPutArrayStorage:
ASSERT(hasArrayStorage(oldType));
return (oldType & ~IndexingShapeMask) | SlowPutArrayStorageShape;
case AddIndexedAccessors:
return oldType | MayHaveIndexedAccessors;
default:
RELEASE_ASSERT_NOT_REACHED();
return oldType;
}
}
class StructureTransitionTable {
static const intptr_t UsingSingleSlotFlag = 1;
struct Hash {
typedef std::pair<StringImpl*, unsigned> Key;
static unsigned hash(const Key& p)
{
return PtrHash<StringImpl*>::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);
}
inline void add(VM&, Structure*);
inline bool contains(StringImpl* rep, unsigned attributes) const;
inline Structure* get(StringImpl* rep, unsigned attributes) const;
private:
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
{
ASSERT(isUsingSingleSlot());
if (WeakImpl* impl = this->weakImpl()) {
if (impl->state() == WeakImpl::Live)
return reinterpret_cast<Structure*>(impl->jsValue().asCell());
}
return 0;
}
void setSingleTransition(VM&, Structure* structure)
{
ASSERT(isUsingSingleSlot());
if (WeakImpl* impl = this->weakImpl())
WeakSet::deallocate(impl);
WeakImpl* impl = WeakSet::allocate(reinterpret_cast<JSCell*>(structure));
m_data = reinterpret_cast<intptr_t>(impl) | UsingSingleSlotFlag;
}
intptr_t m_data;
};
}
#endif // StructureTransitionTable_h