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/*
* Copyright (C) 2017 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. ``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
* 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
#if ENABLE(WEBASSEMBLY)
#include "Options.h"
#include <wtf/Atomics.h>
#include <wtf/StdLibExtras.h>
namespace JSC { namespace Wasm {
// This class manages the tier up counts for Wasm binaries. The main interesting thing about
// wasm tiering up counts is that the least significant bit indicates if the tier up has already
// started. Also, wasm code does not atomically update this count. This is because we
// don't care too much if the countdown is slightly off. The tier up trigger is atomic, however,
// so tier up will be triggered exactly once.
class TierUpCount {
WTF_MAKE_NONCOPYABLE(TierUpCount);
public:
TierUpCount()
: m_count(Options::webAssemblyOMGTierUpCount())
, m_tierUpStarted(false)
{
}
TierUpCount(TierUpCount&& other)
{
ASSERT(other.m_count == Options::webAssemblyOMGTierUpCount());
m_count = other.m_count;
}
static uint32_t loopDecrement() { return Options::webAssemblyLoopDecrement(); }
static uint32_t functionEntryDecrement() { return Options::webAssemblyFunctionEntryDecrement(); }
bool shouldStartTierUp()
{
return !m_tierUpStarted.exchange(true);
}
int32_t count() { return bitwise_cast<int32_t>(m_count); }
private:
uint32_t m_count;
Atomic<bool> m_tierUpStarted;
};
} } // namespace JSC::Wasm
#endif // ENABLE(WEBASSEMBLY)
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