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/*
* Copyright (C) 2015-2019 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. AND ITS CONTRIBUTORS ``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 ITS 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 <wtf/Assertions.h>
namespace JSC {
// The CellState of a cell is a kind of hint about what the state of the cell is.
enum class CellState : uint8_t {
// The object is either currently being scanned, or it has finished being scanned, or this
// is a full collection and it's actually a white object (you'd know because its mark bit
// would be clear).
PossiblyBlack = 0,
// The object is in eden. During GC, this means that the object has not been marked yet.
DefinitelyWhite = 1,
// This sorta means that the object is grey - i.e. it will be scanned. Or it could be white
// during a full collection if its mark bit is clear. That would happen if it had been black,
// got barriered, and we did a full collection.
PossiblyGrey = 2
};
static constexpr unsigned blackThreshold = 0; // x <= blackThreshold means x is PossiblyOldOrBlack.
static constexpr unsigned tautologicalThreshold = 100; // x <= tautologicalThreshold is always true.
inline bool isWithinThreshold(CellState cellState, unsigned threshold)
{
return static_cast<unsigned>(cellState) <= threshold;
}
} // namespace JSC
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