1/*
2 * Copyright (C) 2015-2019 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#include <wtf/Assertions.h>
29
30namespace JSC {
31
32// The CellState of a cell is a kind of hint about what the state of the cell is.
33enum class CellState : uint8_t {
34 // The object is either currently being scanned, or it has finished being scanned, or this
35 // is a full collection and it's actually a white object (you'd know because its mark bit
36 // would be clear).
37 PossiblyBlack = 0,
38
39 // The object is in eden. During GC, this means that the object has not been marked yet.
40 DefinitelyWhite = 1,
41
42 // This sorta means that the object is grey - i.e. it will be scanned. Or it could be white
43 // during a full collection if its mark bit is clear. That would happen if it had been black,
44 // got barriered, and we did a full collection.
45 PossiblyGrey = 2
46};
47
48static constexpr unsigned blackThreshold = 0; // x <= blackThreshold means x is PossiblyOldOrBlack.
49static constexpr unsigned tautologicalThreshold = 100; // x <= tautologicalThreshold is always true.
50
51inline bool isWithinThreshold(CellState cellState, unsigned threshold)
52{
53 return static_cast<unsigned>(cellState) <= threshold;
54}
55
56} // namespace JSC
57