1/*
2 * Copyright (C) 2017 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. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#if ENABLE(WEBASSEMBLY)
29
30#include "Options.h"
31#include <wtf/Atomics.h>
32#include <wtf/StdLibExtras.h>
33
34namespace JSC { namespace Wasm {
35
36// This class manages the tier up counts for Wasm binaries. The main interesting thing about
37// wasm tiering up counts is that the least significant bit indicates if the tier up has already
38// started. Also, wasm code does not atomically update this count. This is because we
39// don't care too much if the countdown is slightly off. The tier up trigger is atomic, however,
40// so tier up will be triggered exactly once.
41class TierUpCount {
42 WTF_MAKE_NONCOPYABLE(TierUpCount);
43public:
44 TierUpCount()
45 : m_count(Options::webAssemblyOMGTierUpCount())
46 , m_tierUpStarted(false)
47 {
48 }
49
50 TierUpCount(TierUpCount&& other)
51 {
52 ASSERT(other.m_count == Options::webAssemblyOMGTierUpCount());
53 m_count = other.m_count;
54 }
55
56 static uint32_t loopDecrement() { return Options::webAssemblyLoopDecrement(); }
57 static uint32_t functionEntryDecrement() { return Options::webAssemblyFunctionEntryDecrement(); }
58
59 bool shouldStartTierUp()
60 {
61 return !m_tierUpStarted.exchange(true);
62 }
63
64 int32_t count() { return bitwise_cast<int32_t>(m_count); }
65
66private:
67 uint32_t m_count;
68 Atomic<bool> m_tierUpStarted;
69};
70
71} } // namespace JSC::Wasm
72
73#endif // ENABLE(WEBASSEMBLY)
74