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57 lines
2.5 KiB
C++
57 lines
2.5 KiB
C++
/*
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* Copyright (C) 2015-2019 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <wtf/Assertions.h>
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namespace JSC {
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// The CellState of a cell is a kind of hint about what the state of the cell is.
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enum class CellState : uint8_t {
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// The object is either currently being scanned, or it has finished being scanned, or this
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// is a full collection and it's actually a white object (you'd know because its mark bit
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// would be clear).
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PossiblyBlack = 0,
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// The object is in eden. During GC, this means that the object has not been marked yet.
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DefinitelyWhite = 1,
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// This sorta means that the object is grey - i.e. it will be scanned. Or it could be white
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// during a full collection if its mark bit is clear. That would happen if it had been black,
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// got barriered, and we did a full collection.
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PossiblyGrey = 2
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};
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static constexpr unsigned blackThreshold = 0; // x <= blackThreshold means x is PossiblyOldOrBlack.
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static constexpr unsigned tautologicalThreshold = 100; // x <= tautologicalThreshold is always true.
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inline bool isWithinThreshold(CellState cellState, unsigned threshold)
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{
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return static_cast<unsigned>(cellState) <= threshold;
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}
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} // namespace JSC
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