Source/JavaScriptCore/bytecode/BytecodeLivenessAnalysis.h

/*
 * Copyright (C) 2013, 2015 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
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 * 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. AND ITS CONTRIBUTORS ``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 ITS CONTRIBUTORS
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 */

#pragma once

#include "BytecodeBasicBlock.h"
#include "BytecodeGraph.h"
#include "CodeBlock.h"
#include <wtf/FastBitVector.h>

namespace JSC {

class BytecodeKills;
class FullBytecodeLiveness;

// We model our bytecode effects like the following and insert the liveness calculation points.
//
// <- BeforeUse
//     Use
// <- AfterUse
//     Use by exception handlers
//     Def
enum class LivenessCalculationPoint : uint8_t {
    BeforeUse,
    AfterUse,
};

class BytecodeLivenessPropagation {
public:
    template<typename CodeBlockType, typename UseFunctor>
    static void stepOverInstructionUse(CodeBlockType*, const InstructionStream&, BytecodeGraph&, BytecodeIndex, const UseFunctor&);
    template<typename CodeBlockType, typename UseFunctor>
    static void stepOverInstructionUseInExceptionHandler(CodeBlockType*, const InstructionStream&, BytecodeGraph&, BytecodeIndex, const UseFunctor&);
    template<typename CodeBlockType, typename DefFunctor>
    static void stepOverInstructionDef(CodeBlockType*, const InstructionStream&, BytecodeGraph&, BytecodeIndex, const DefFunctor&);

    template<typename CodeBlockType, typename UseFunctor, typename DefFunctor>
    static void stepOverInstruction(CodeBlockType*, const InstructionStream&, BytecodeGraph&, BytecodeIndex, const UseFunctor&, const DefFunctor&);

    template<typename CodeBlockType>
    static void stepOverInstruction(CodeBlockType*, const InstructionStream&, BytecodeGraph&, BytecodeIndex, FastBitVector& out);

    template<typename CodeBlockType, typename Instructions>
    static bool computeLocalLivenessForBytecodeIndex(CodeBlockType*, const Instructions&, BytecodeGraph&, BytecodeBasicBlock*, BytecodeIndex, FastBitVector& result);

    template<typename CodeBlockType, typename Instructions>
    static bool computeLocalLivenessForBlock(CodeBlockType*, const Instructions&, BytecodeGraph&, BytecodeBasicBlock*);

    template<typename CodeBlockType, typename Instructions>
    static FastBitVector getLivenessInfoAtBytecodeIndex(CodeBlockType*, const Instructions&, BytecodeGraph&, BytecodeIndex);

    template<typename CodeBlockType, typename Instructions>
    static void runLivenessFixpoint(CodeBlockType*, const Instructions&, BytecodeGraph&);
};

class BytecodeLivenessAnalysis : private BytecodeLivenessPropagation {
    WTF_MAKE_FAST_ALLOCATED;
    WTF_MAKE_NONCOPYABLE(BytecodeLivenessAnalysis);
public:
    friend class BytecodeLivenessPropagation;
    BytecodeLivenessAnalysis(CodeBlock*);
    
    FastBitVector getLivenessInfoAtBytecodeIndex(CodeBlock*, BytecodeIndex);
    
    void computeFullLiveness(CodeBlock*, FullBytecodeLiveness& result);
    void computeKills(CodeBlock*, BytecodeKills& result);

    BytecodeGraph& graph() { return m_graph; }

private:
    void dumpResults(CodeBlock*);

    void getLivenessInfoAtBytecodeIndex(CodeBlock*, BytecodeIndex, FastBitVector&);

    BytecodeGraph m_graph;
};

inline bool operandIsAlwaysLive(int operand);
inline bool operandThatIsNotAlwaysLiveIsLive(const FastBitVector& out, int operand);
inline bool operandIsLive(const FastBitVector& out, int operand);
inline bool isValidRegisterForLiveness(int operand);

} // namespace JSC