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/*
* Copyright (C) 2019-2025 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
#include <wtf/HashTraits.h>
#include <wtf/MathExtras.h>
namespace WTF {
class PrintStream;
}
namespace JSC {
using Checkpoint = uint8_t;
static constexpr Checkpoint noCheckpoints = 0;
class BytecodeIndex {
public:
BytecodeIndex() = default;
BytecodeIndex(WTF::HashTableDeletedValueType)
: m_packedBits(deletedValue().asBits())
{
}
explicit BytecodeIndex(uint32_t bytecodeOffset, Checkpoint checkpoint = noCheckpoints)
: m_packedBits(pack(bytecodeOffset, checkpoint))
{
ASSERT(*this);
}
static constexpr uint32_t numberOfCheckpoints = 4;
static_assert(hasOneBitSet(numberOfCheckpoints), "numberOfCheckpoints should be a power of 2");
static constexpr uint32_t checkpointMask = numberOfCheckpoints - 1;
static constexpr uint32_t checkpointShift = WTF::getMSBSetConstexpr(numberOfCheckpoints);
uint32_t offset() const { return m_packedBits >> checkpointShift; }
Checkpoint checkpoint() const { return m_packedBits & checkpointMask; }
uint32_t asBits() const { return m_packedBits; }
unsigned hash() const { return intHash(m_packedBits); }
static BytecodeIndex deletedValue() { return fromBits(invalidOffset - 1); }
bool isHashTableDeletedValue() const { return *this == deletedValue(); }
static constexpr bool safeToCompareToHashTableEmptyOrDeletedValue = true;
static BytecodeIndex fromBits(uint32_t bits);
BytecodeIndex withCheckpoint(Checkpoint checkpoint) const { return BytecodeIndex(offset(), checkpoint); }
// Comparison operators.
explicit operator bool() const { return m_packedBits != invalidOffset && m_packedBits != deletedValue().offset(); }
friend auto operator<=>(const BytecodeIndex&, const BytecodeIndex&) = default;
void dump(WTF::PrintStream&) const;
private:
static constexpr uint32_t invalidOffset = std::numeric_limits<uint32_t>::max();
static uint32_t pack(uint32_t bytecodeIndex, Checkpoint);
uint32_t m_packedBits { invalidOffset };
};
inline uint32_t BytecodeIndex::pack(uint32_t bytecodeIndex, Checkpoint checkpoint)
{
ASSERT(checkpoint < numberOfCheckpoints);
ASSERT((bytecodeIndex << checkpointShift) >> checkpointShift == bytecodeIndex);
return bytecodeIndex << checkpointShift | checkpoint;
}
inline BytecodeIndex BytecodeIndex::fromBits(uint32_t bits)
{
BytecodeIndex result;
result.m_packedBits = bits;
return result;
}
} // namespace JSC
namespace WTF {
template<typename T> struct HashTraits;
template<> struct HashTraits<JSC::BytecodeIndex> : SimpleClassHashTraits<JSC::BytecodeIndex> {
static constexpr bool emptyValueIsZero = false;
};
} // namespace WTF
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