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/*
* Copyright (C) 2017-2023 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "MarkedBlock.h"
#include <wtf/BitSet.h>
#include <wtf/ConcurrentVector.h>
#include <wtf/FastBitVector.h>
#include <wtf/Noncopyable.h>
#include <wtf/Nonmovable.h>
#include <wtf/SentinelLinkedList.h>
#include <wtf/SharedTask.h>
namespace JSC {
class HeapCell;
class IsoSubspace;
// Create a set of cells that are in an IsoSubspace. This allows concurrent O(1) set insertion and
// removal. Each such set should be thought of as a 0.8% increase in object size for objects in that
// IsoSubspace (it's like adding 1 bit every 16 bytes, or 1 bit every 128 bits).
class IsoCellSet final : public BasicRawSentinelNode<IsoCellSet> {
WTF_MAKE_NONCOPYABLE(IsoCellSet);
WTF_MAKE_NONMOVABLE(IsoCellSet);
public:
IsoCellSet(IsoSubspace& subspace);
~IsoCellSet();
bool add(HeapCell* cell); // Returns true if the cell was newly added.
bool remove(HeapCell* cell); // Returns true if the cell was previously present and got removed.
bool contains(HeapCell* cell) const;
JS_EXPORT_PRIVATE Ref<SharedTask<MarkedBlock::Handle*()>> parallelNotEmptyMarkedBlockSource();
// This will have to do a combined search over whatever Subspace::forEachMarkedCell uses and
// our m_blocksWithBits.
template<typename Func>
void forEachMarkedCell(const Func&);
template<typename Visitor, typename Func>
Ref<SharedTask<void(Visitor&)>> forEachMarkedCellInParallel(const Func&);
template<typename Func>
void forEachLiveCell(const Func&);
private:
friend class IsoSubspace;
WTF::BitSet<MarkedBlock::atomsPerBlock>* addSlow(unsigned blockIndex);
void didResizeBits(unsigned newSize);
void didRemoveBlock(unsigned blockIndex);
void sweepToFreeList(MarkedBlock::Handle*);
void clearLowerTierCell(unsigned);
WTF::BitSet<MarkedBlock::maxNumberOfLowerTierCells> m_lowerTierBits;
IsoSubspace& m_subspace;
// Idea: sweeping to free-list clears bits for those cells that were free-listed. The first time
// we add a cell in a block, that block gets a free-list. Unless we do something that obviously
// clears all bits for a block, we keep it set in blocksWithBits.
FastBitVector m_blocksWithBits;
ConcurrentVector<std::unique_ptr<WTF::BitSet<MarkedBlock::atomsPerBlock>>> m_bits;
};
} // namespace JSC
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