1/*
2 * Copyright (C) 2015 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#ifndef CellState_h
27#define CellState_h
28
29namespace JSC {
30
31enum class CellState : uint8_t {
32 // The object is black as far as this GC is concerned. When not in GC, this just means that it's an
33 // old gen object. Note that we deliberately arrange OldBlack to be zero, so that the store barrier on
34 // a target object "from" is just:
35 //
36 // if (!from->cellState())
37 // slowPath(from);
38 //
39 // There is a bunch of code in the LLInt and JITs that rely on this being the case. You'd have to
40 // change a lot of code if you ever wanted the store barrier to be anything but a non-zero check on
41 // cellState.
42 OldBlack = 0,
43
44 // The object is in eden. During GC, this means that the object has not been marked yet.
45 NewWhite = 1,
46
47 // The object is grey - i.e. it will be scanned - but it either belongs to old gen (if this is eden
48 // GC) or it is grey a second time in this current GC (because a concurrent store barrier requested
49 // re-greying).
50 OldGrey = 2,
51
52 // The object is grey - i.e. it will be scanned - and this is the first time in this GC that we are
53 // going to scan it. If this is an eden GC, this also means that the object is in eden.
54 NewGrey = 3
55};
56
57} // namespace JSC
58
59#endif // CellState_h
60
61