bytecodegenerator.cpp

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        instructions().append(m_thisRegister.index());
    }
    
    for (size_t i = 0; i < parameterCount; ++i)
        addParameter(parameters[i]);

    allocateConstants(functionBody->neededConstants());
}

BytecodeGenerator::BytecodeGenerator(EvalNode* evalNode, const Debugger* debugger, const ScopeChain& scopeChain, SymbolTable* symbolTable, EvalCodeBlock* codeBlock)
    : m_shouldEmitDebugHooks(!!debugger)
    , m_shouldEmitProfileHooks(scopeChain.globalObject()->supportsProfiling())
    , m_scopeChain(&scopeChain)
    , m_symbolTable(symbolTable)
    , m_scopeNode(evalNode)
    , m_codeBlock(codeBlock)
    , m_thisRegister(RegisterFile::ProgramCodeThisRegister)
    , m_finallyDepth(0)
    , m_dynamicScopeDepth(0)
    , m_baseScopeDepth(codeBlock->baseScopeDepth())
    , m_codeType(EvalCode)
    , m_globalData(&scopeChain.globalObject()->globalExec()->globalData())
    , m_lastOpcodeID(op_end)
    , m_emitNodeDepth(0)
    , m_regeneratingForExceptionInfo(false)
    , m_codeBlockBeingRegeneratedFrom(0)
{
    if (m_shouldEmitDebugHooks || m_baseScopeDepth)
        m_codeBlock->setNeedsFullScopeChain(true);

    emitOpcode(op_enter);
    codeBlock->setGlobalData(m_globalData);
    m_codeBlock->m_numParameters = 1; // Allocate space for "this"

    allocateConstants(evalNode->neededConstants());
}

RegisterID* BytecodeGenerator::addParameter(const Identifier& ident)
{
    // Parameters overwrite var declarations, but not function declarations.
    RegisterID* result = 0;
    UString::Rep* rep = ident.ustring().rep();
    if (!m_functions.contains(rep)) {
        symbolTable().set(rep, m_nextParameterIndex);
        RegisterID& parameter = registerFor(m_nextParameterIndex);
        parameter.setIndex(m_nextParameterIndex);
        result = &parameter;
    }

    // To maintain the calling convention, we have to allocate unique space for
    // each parameter, even if the parameter doesn't make it into the symbol table.
    ++m_nextParameterIndex;
    ++m_codeBlock->m_numParameters;
    return result;
}

RegisterID* BytecodeGenerator::registerFor(const Identifier& ident)
{
    if (ident == propertyNames().thisIdentifier)
        return &m_thisRegister;

    if (!shouldOptimizeLocals())
        return 0;

    SymbolTableEntry entry = symbolTable().get(ident.ustring().rep());
    if (entry.isNull())
        return 0;

    return &registerFor(entry.getIndex());
}

RegisterID* BytecodeGenerator::constRegisterFor(const Identifier& ident)
{
    if (m_codeType == EvalCode)
        return 0;

    SymbolTableEntry entry = symbolTable().get(ident.ustring().rep());
    ASSERT(!entry.isNull());

    return &registerFor(entry.getIndex());
}

bool BytecodeGenerator::isLocal(const Identifier& ident)
{
    if (ident == propertyNames().thisIdentifier)
        return true;
    
    return shouldOptimizeLocals() && symbolTable().contains(ident.ustring().rep());
}

bool BytecodeGenerator::isLocalConstant(const Identifier& ident)
{
    return symbolTable().get(ident.ustring().rep()).isReadOnly();
}

RegisterID* BytecodeGenerator::newRegister()
{
    m_calleeRegisters.append(m_calleeRegisters.size());
    m_codeBlock->m_numCalleeRegisters = max<int>(m_codeBlock->m_numCalleeRegisters, m_calleeRegisters.size());
    return &m_calleeRegisters.last();
}

RegisterID* BytecodeGenerator::newTemporary()
{
    // Reclaim free register IDs.
    while (m_calleeRegisters.size() && !m_calleeRegisters.last().refCount())
        m_calleeRegisters.removeLast();
        
    RegisterID* result = newRegister();
    result->setTemporary();
    return result;
}

RegisterID* BytecodeGenerator::highestUsedRegister()
{
    size_t count = m_codeBlock->m_numCalleeRegisters;
    while (m_calleeRegisters.size() < count)
        newRegister();
    return &m_calleeRegisters.last();
}

PassRefPtr<LabelScope> BytecodeGenerator::newLabelScope(LabelScope::Type type, const Identifier* name)
{
    // Reclaim free label scopes.
    while (m_labelScopes.size() && !m_labelScopes.last().refCount())
        m_labelScopes.removeLast();

    // Allocate new label scope.
    LabelScope scope(type, name, scopeDepth(), newLabel(), type == LabelScope::Loop ? newLabel() : 0); // Only loops have continue targets.
    m_labelScopes.append(scope);
    return &m_labelScopes.last();
}

PassRefPtr<Label> BytecodeGenerator::newLabel()
{
    // Reclaim free label IDs.
    while (m_labels.size() && !m_labels.last().refCount())
        m_labels.removeLast();

    // Allocate new label ID.
    m_labels.append(m_codeBlock);
    return &m_labels.last();
}

PassRefPtr<Label> BytecodeGenerator::emitLabel(Label* l0)
{
    unsigned newLabelIndex = instructions().size();
    l0->setLocation(newLabelIndex);

    if (m_codeBlock->numberOfJumpTargets()) {
        unsigned lastLabelIndex = m_codeBlock->lastJumpTarget();
        ASSERT(lastLabelIndex <= newLabelIndex);
        if (newLabelIndex == lastLabelIndex) {
            // Peephole optimizations have already been disabled by emitting the last label
            return l0;
        }
    }

    m_codeBlock->addJumpTarget(newLabelIndex);

    // This disables peephole optimizations when an instruction is a jump target
    m_lastOpcodeID = op_end;
    return l0;
}

void BytecodeGenerator::emitOpcode(OpcodeID opcodeID)
{
    instructions().append(globalData()->interpreter->getOpcode(opcodeID));
    m_lastOpcodeID = opcodeID;
}

void BytecodeGenerator::retrieveLastBinaryOp(int& dstIndex, int& src1Index, int& src2Index)
{
    ASSERT(instructions().size() >= 4);
    size_t size = instructions().size();
    dstIndex = instructions().at(size - 3).u.operand;
    src1Index = instructions().at(size - 2).u.operand;
    src2Index = instructions().at(size - 1).u.operand;
}

void BytecodeGenerator::retrieveLastUnaryOp(int& dstIndex, int& srcIndex)
{
    ASSERT(instructions().size() >= 3);
    size_t size = instructions().size();
    dstIndex = instructions().at(size - 2).u.operand;
    srcIndex = instructions().at(size - 1).u.operand;
}

void ALWAYS_INLINE BytecodeGenerator::rewindBinaryOp()
{
    ASSERT(instructions().size() >= 4);
    instructions().shrink(instructions().size() - 4);
}

void ALWAYS_INLINE BytecodeGenerator::rewindUnaryOp()
{
    ASSERT(instructions().size() >= 3);
    instructions().shrink(instructions().size() - 3);
}

PassRefPtr<Label> BytecodeGenerator::emitJump(Label* target)
{
    emitOpcode(target->isForward() ? op_jmp : op_loop);
    instructions().append(target->offsetFrom(instructions().size()));
    return target;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpIfTrue(RegisterID* cond, Label* target)
{
    if (m_lastOpcodeID == op_less && !target->isForward()) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindBinaryOp();
            emitOpcode(op_loop_if_less);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_lesseq && !target->isForward()) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindBinaryOp();
            emitOpcode(op_loop_if_lesseq);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_eq_null && target->isForward()) {
        int dstIndex;
        int srcIndex;

        retrieveLastUnaryOp(dstIndex, srcIndex);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindUnaryOp();
            emitOpcode(op_jeq_null);
            instructions().append(srcIndex);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_neq_null && target->isForward()) {
        int dstIndex;
        int srcIndex;

        retrieveLastUnaryOp(dstIndex, srcIndex);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindUnaryOp();
            emitOpcode(op_jneq_null);
            instructions().append(srcIndex);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    }

    emitOpcode(target->isForward() ? op_jtrue : op_loop_if_true);
    instructions().append(cond->index());
    instructions().append(target->offsetFrom(instructions().size()));
    return target;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpIfFalse(RegisterID* cond, Label* target)
{
    ASSERT(target->isForward());

    if (m_lastOpcodeID == op_less) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindBinaryOp();
            emitOpcode(op_jnless);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_not) {
        int dstIndex;
        int srcIndex;

        retrieveLastUnaryOp(dstIndex, srcIndex);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindUnaryOp();
            emitOpcode(op_jtrue);
            instructions().append(srcIndex);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_eq_null) {
        int dstIndex;
        int srcIndex;

        retrieveLastUnaryOp(dstIndex, srcIndex);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindUnaryOp();
            emitOpcode(op_jneq_null);
            instructions().append(srcIndex);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_neq_null) {
        int dstIndex;
        int srcIndex;

        retrieveLastUnaryOp(dstIndex, srcIndex);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindUnaryOp();
            emitOpcode(op_jeq_null);
            instructions().append(srcIndex);
            instructions().append(target->offsetFrom(instructions().size()));
            return target;
        }
    }

    emitOpcode(op_jfalse);
    instructions().append(cond->index());
    instructions().append(target->offsetFrom(instructions().size()));
    return target;
}

unsigned BytecodeGenerator::addConstant(FuncDeclNode* n)
{
    // No need to explicitly unique function body nodes -- they're unique already.
    return m_codeBlock->addFunction(n);
}

unsigned BytecodeGenerator::addConstant(FuncExprNode* n)
{
    // No need to explicitly unique function expression nodes -- they're unique already.
    return m_codeBlock->addFunctionExpression(n);
}

unsigned BytecodeGenerator::addConstant(const Identifier& ident)
{
    UString::Rep* rep = ident.ustring().rep();
    pair<IdentifierMap::iterator, bool> result = m_identifierMap.add(rep, m_codeBlock->numberOfIdentifiers());
    if (result.second) // new entry
        m_codeBlock->addIdentifier(Identifier(m_globalData, rep));