JavaScriptCore/bytecompiler/BytecodeGenerator.cpp

/*
 * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
 * Copyright (C) 2008 Cameron Zwarich <cwzwarich@uwaterloo.ca>
 *
 * 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.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE 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 OR ITS 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.
 */

#include "config.h"
#include "BytecodeGenerator.h"

#include "BatchedTransitionOptimizer.h"
#include "PrototypeFunction.h"
#include "JSFunction.h"
#include "Interpreter.h"
#include "UString.h"

using namespace std;

namespace JSC {

/*
    The layout of a register frame looks like this:

    For

    function f(x, y) {
        var v1;
        function g() { }
        var v2;
        return (x) * (y);
    }

    assuming (x) and (y) generated temporaries t1 and t2, you would have

    ------------------------------------
    |  x |  y |  g | v2 | v1 | t1 | t2 | <-- value held
    ------------------------------------
    | -5 | -4 | -3 | -2 | -1 | +0 | +1 | <-- register index
    ------------------------------------
    | params->|<-locals      | temps->

    Because temporary registers are allocated in a stack-like fashion, we
    can reclaim them with a simple popping algorithm. The same goes for labels.
    (We never reclaim parameter or local registers, because parameters and
    locals are DontDelete.)

    The register layout before a function call looks like this:

    For

    function f(x, y)
    {
    }

    f(1);

    >                        <------------------------------
    <                        >  reserved: call frame  |  1 | <-- value held
    >         >snip<         <------------------------------
    <                        > +0 | +1 | +2 | +3 | +4 | +5 | <-- register index
    >                        <------------------------------
    | params->|<-locals      | temps->

    The call instruction fills in the "call frame" registers. It also pads
    missing arguments at the end of the call:

    >                        <-----------------------------------
    <                        >  reserved: call frame  |  1 |  ? | <-- value held ("?" stands for "undefined")
    >         >snip<         <-----------------------------------
    <                        > +0 | +1 | +2 | +3 | +4 | +5 | +6 | <-- register index
    >                        <-----------------------------------
    | params->|<-locals      | temps->

    After filling in missing arguments, the call instruction sets up the new
    stack frame to overlap the end of the old stack frame:

                             |---------------------------------->                        <
                             |  reserved: call frame  |  1 |  ? <                        > <-- value held ("?" stands for "undefined")
                             |---------------------------------->         >snip<         <
                             | -7 | -6 | -5 | -4 | -3 | -2 | -1 <                        > <-- register index
                             |---------------------------------->                        <
                             |                        | params->|<-locals       | temps->

    That way, arguments are "copied" into the callee's stack frame for free.

    If the caller supplies too many arguments, this trick doesn't work. The
    extra arguments protrude into space reserved for locals and temporaries.
    In that case, the call instruction makes a real copy of the call frame header,
    along with just the arguments expected by the callee, leaving the original
    call frame header and arguments behind. (The call instruction can't just discard
    extra arguments, because the "arguments" object may access them later.)
    This copying strategy ensures that all named values will be at the indices
    expected by the callee.
*/

#ifndef NDEBUG
static bool s_dumpsGeneratedCode = false;
#endif

void BytecodeGenerator::setDumpsGeneratedCode(bool dumpsGeneratedCode)
{
#ifndef NDEBUG
    s_dumpsGeneratedCode = dumpsGeneratedCode;
#else
    UNUSED_PARAM(dumpsGeneratedCode);
#endif
}

bool BytecodeGenerator::dumpsGeneratedCode()
{
#ifndef NDEBUG
    return s_dumpsGeneratedCode;
#else
    return false;
#endif
}

void BytecodeGenerator::generate()
{
    m_codeBlock->setThisRegister(m_thisRegister.index());

    m_scopeNode->emitBytecode(*this);

#ifndef NDEBUG
    m_codeBlock->setInstructionCount(m_codeBlock->instructions().size());

    if (s_dumpsGeneratedCode)
        m_codeBlock->dump(m_scopeChain->globalObject()->globalExec());
#endif

    if ((m_codeType == FunctionCode && !m_codeBlock->needsFullScopeChain() && !m_codeBlock->usesArguments()) || m_codeType == EvalCode)
        symbolTable().clear();

    m_codeBlock->setIsNumericCompareFunction(instructions() == m_globalData->numericCompareFunction(m_scopeChain->globalObject()->globalExec()));

#if !ENABLE(OPCODE_SAMPLING)
    if (!m_regeneratingForExceptionInfo && (m_codeType == FunctionCode || m_codeType == EvalCode))
        m_codeBlock->clearExceptionInfo();
#endif

    m_codeBlock->shrinkToFit();
}

bool BytecodeGenerator::addVar(const Identifier& ident, bool isConstant, RegisterID*& r0)
{
    int index = m_calleeRegisters.size();
    SymbolTableEntry newEntry(index, isConstant ? ReadOnly : 0);
    pair<SymbolTable::iterator, bool> result = symbolTable().add(ident.ustring().rep(), newEntry);

    if (!result.second) {
        r0 = &registerFor(result.first->second.getIndex());
        return false;
    }

    ++m_codeBlock->m_numVars;
    r0 = newRegister();
    return true;
}

bool BytecodeGenerator::addGlobalVar(const Identifier& ident, bool isConstant, RegisterID*& r0)
{
    int index = m_nextGlobalIndex;
    SymbolTableEntry newEntry(index, isConstant ? ReadOnly : 0);
    pair<SymbolTable::iterator, bool> result = symbolTable().add(ident.ustring().rep(), newEntry);

    if (!result.second)
        index = result.first->second.getIndex();
    else {
        --m_nextGlobalIndex;
        m_globals.append(index + m_globalVarStorageOffset);
    }

    r0 = &registerFor(index);
    return result.second;
}

void BytecodeGenerator::preserveLastVar()
{
    if ((m_firstConstantIndex = m_calleeRegisters.size()) != 0)
        m_lastVar = &m_calleeRegisters.last();
}

BytecodeGenerator::BytecodeGenerator(ProgramNode* programNode, const Debugger* debugger, const ScopeChain& scopeChain, SymbolTable* symbolTable, ProgramCodeBlock* codeBlock)
    : m_shouldEmitDebugHooks(!!debugger)
    , m_shouldEmitProfileHooks(scopeChain.globalObject()->supportsProfiling())
    , m_scopeChain(&scopeChain)
    , m_symbolTable(symbolTable)
    , m_scopeNode(programNode)
    , m_codeBlock(codeBlock)
    , m_thisRegister(RegisterFile::ProgramCodeThisRegister)
    , m_finallyDepth(0)
    , m_dynamicScopeDepth(0)
    , m_baseScopeDepth(0)
    , m_codeType(GlobalCode)
    , m_nextGlobalIndex(-1)
    , m_nextConstantOffset(0)
    , m_globalConstantIndex(0)
    , m_globalData(&scopeChain.globalObject()->globalExec()->globalData())
    , m_lastOpcodeID(op_end)
    , m_emitNodeDepth(0)
    , m_regeneratingForExceptionInfo(false)
    , m_codeBlockBeingRegeneratedFrom(0)
{
    if (m_shouldEmitDebugHooks)
        m_codeBlock->setNeedsFullScopeChain(true);

    emitOpcode(op_enter);
    codeBlock->setGlobalData(m_globalData);

    // FIXME: Move code that modifies the global object to Interpreter::execute.

    m_codeBlock->m_numParameters = 1; // Allocate space for "this"

    JSGlobalObject* globalObject = scopeChain.globalObject();
    ExecState* exec = globalObject->globalExec();
    RegisterFile* registerFile = &exec->globalData().interpreter->registerFile();

    // Shift register indexes in generated code to elide registers allocated by intermediate stack frames.
    m_globalVarStorageOffset = -RegisterFile::CallFrameHeaderSize - m_codeBlock->m_numParameters - registerFile->size();

    // Add previously defined symbols to bookkeeping.
    m_globals.grow(symbolTable->size());
    SymbolTable::iterator end = symbolTable->end();
    for (SymbolTable::iterator it = symbolTable->begin(); it != end; ++it)
        registerFor(it->second.getIndex()).setIndex(it->second.getIndex() + m_globalVarStorageOffset);

    BatchedTransitionOptimizer optimizer(globalObject);

    const VarStack& varStack = programNode->varStack();
    const FunctionStack& functionStack = programNode->functionStack();
    bool canOptimizeNewGlobals = symbolTable->size() + functionStack.size() + varStack.size() < registerFile->maxGlobals();
    if (canOptimizeNewGlobals) {
        // Shift new symbols so they get stored prior to existing symbols.
        m_nextGlobalIndex -= symbolTable->size();

        for (size_t i = 0; i < functionStack.size(); ++i) {
            FuncDeclNode* funcDecl = functionStack[i];
            globalObject->removeDirect(funcDecl->m_ident); // Make sure our new function is not shadowed by an old property.
            emitNewFunction(addGlobalVar(funcDecl->m_ident, false), funcDecl);
        }

        Vector<RegisterID*, 32> newVars;
        for (size_t i = 0; i < varStack.size(); ++i)
            if (!globalObject->hasProperty(exec, varStack[i].first))
                newVars.append(addGlobalVar(varStack[i].first, varStack[i].second & DeclarationStacks::IsConstant));

        preserveLastVar();

        for (size_t i = 0; i < newVars.size(); ++i)
            emitLoad(newVars[i], jsUndefined());
    } else {
        for (size_t i = 0; i < functionStack.size(); ++i) {
            FuncDeclNode* funcDecl = functionStack[i];
            globalObject->putWithAttributes(exec, funcDecl->m_ident, funcDecl->makeFunction(exec, scopeChain.node()), DontDelete);
        }
        for (size_t i = 0; i < varStack.size(); ++i) {
            if (globalObject->hasProperty(exec, varStack[i].first))
                continue;
            int attributes = DontDelete;
            if (varStack[i].second & DeclarationStacks::IsConstant)
                attributes |= ReadOnly;
            globalObject->putWithAttributes(exec, varStack[i].first, jsUndefined(), attributes);
        }

        preserveLastVar();
    }
}

BytecodeGenerator::BytecodeGenerator(FunctionBodyNode* functionBody, const Debugger* debugger, const ScopeChain& scopeChain, SymbolTable* symbolTable, CodeBlock* codeBlock)
    : m_shouldEmitDebugHooks(!!debugger)
    , m_shouldEmitProfileHooks(scopeChain.globalObject()->supportsProfiling())
    , m_scopeChain(&scopeChain)
    , m_symbolTable(symbolTable)
    , m_scopeNode(functionBody)
    , m_codeBlock(codeBlock)
    , m_finallyDepth(0)
    , m_dynamicScopeDepth(0)
    , m_baseScopeDepth(0)
    , m_codeType(FunctionCode)
    , m_nextConstantOffset(0)
    , m_globalConstantIndex(0)
    , m_globalData(&scopeChain.globalObject()->globalExec()->globalData())
    , m_lastOpcodeID(op_end)
    , m_emitNodeDepth(0)
    , m_regeneratingForExceptionInfo(false)
    , m_codeBlockBeingRegeneratedFrom(0)
{
    if (m_shouldEmitDebugHooks)
        m_codeBlock->setNeedsFullScopeChain(true);

    codeBlock->setGlobalData(m_globalData);

    bool usesArguments = functionBody->usesArguments();
    codeBlock->setUsesArguments(usesArguments);
    if (usesArguments) {
        m_argumentsRegister.setIndex(RegisterFile::OptionalCalleeArguments);
        addVar(propertyNames().arguments, false);
    }

    if (m_codeBlock->needsFullScopeChain()) {
        ++m_codeBlock->m_numVars;
        m_activationRegisterIndex = newRegister()->index();
        emitOpcode(op_enter_with_activation);
        instructions().append(m_activationRegisterIndex);
    } else
        emitOpcode(op_enter);

    if (usesArguments) {
        emitOpcode(op_init_arguments);

        // The debugger currently retrieves the arguments object from an activation rather than pulling
        // it from a call frame.  In the long-term it should stop doing that (<rdar://problem/6911886>),
        // but for now we force eager creation of the arguments object when debugging.
        if (m_shouldEmitDebugHooks)
            emitOpcode(op_create_arguments);
    }

    const DeclarationStacks::FunctionStack& functionStack = functionBody->functionStack();
    for (size_t i = 0; i < functionStack.size(); ++i) {
        FuncDeclNode* funcDecl = functionStack[i];
        const Identifier& ident = funcDecl->m_ident;
        m_functions.add(ident.ustring().rep());
        emitNewFunction(addVar(ident, false), funcDecl);
    }

    const DeclarationStacks::VarStack& varStack = functionBody->varStack();
    for (size_t i = 0; i < varStack.size(); ++i)
        addVar(varStack[i].first, varStack[i].second & DeclarationStacks::IsConstant);

    const Identifier* parameters = functionBody->parameters();
    size_t parameterCount = functionBody->parameterCount();
    m_nextParameterIndex = -RegisterFile::CallFrameHeaderSize - parameterCount - 1;
    m_parameters.grow(1 + parameterCount); // reserve space for "this"

    // Add "this" as a parameter
    m_thisRegister.setIndex(m_nextParameterIndex);
    ++m_nextParameterIndex;
    ++m_codeBlock->m_numParameters;

    if (functionBody->usesThis() || m_shouldEmitDebugHooks) {
        emitOpcode(op_convert_this);
        instructions().append(m_thisRegister.index());
    }

    for (size_t i = 0; i < parameterCount; ++i)
        addParameter(parameters[i]);

    preserveLastVar();
}

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_nextConstantOffset(0)
    , m_globalConstantIndex(0)
    , 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"

    preserveLastVar();
}

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;

    if (ident == propertyNames().arguments)
        createArgumentsIfNecessary();

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

bool BytecodeGenerator::willResolveToArguments(const Identifier& ident)
{
    if (ident != propertyNames().arguments)
        return false;

    if (!shouldOptimizeLocals())
        return false;

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

    if (m_codeBlock->usesArguments() && m_codeType == FunctionCode)
        return true;

    return false;
}

RegisterID* BytecodeGenerator::uncheckedRegisterForArguments()
{
    ASSERT(willResolveToArguments(propertyNames().arguments));

    SymbolTableEntry entry = symbolTable().get(propertyNames().arguments.ustring().rep());
    ASSERT(!entry.isNull());
    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() : PassRefPtr<Label>()); // 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_lesseq) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

        if (cond->index() == dstIndex && cond->isTemporary() && !cond->refCount()) {
            rewindBinaryOp();
            emitOpcode(op_jnlesseq);
            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;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpIfNotFunctionCall(RegisterID* cond, Label* target)
{
    emitOpcode(op_jneq_ptr);
    instructions().append(cond->index());
    instructions().append(m_scopeChain->globalObject()->d()->callFunction);
    instructions().append(target->offsetFrom(instructions().size()));
    return target;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpIfNotFunctionApply(RegisterID* cond, Label* target)
{
    emitOpcode(op_jneq_ptr);
    instructions().append(cond->index());
    instructions().append(m_scopeChain->globalObject()->d()->applyFunction);
    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));

    return result.first->second;
}

RegisterID* BytecodeGenerator::addConstantValue(JSValue v)
{
    int index = m_nextConstantOffset;

    pair<JSValueMap::iterator, bool> result = m_jsValueMap.add(JSValue::encode(v), m_nextConstantOffset);
    if (result.second) {
        m_constantPoolRegisters.append(FirstConstantRegisterIndex + m_nextConstantOffset);
        ++m_nextConstantOffset;
        m_codeBlock->addConstantRegister(JSValue(v));
    } else
        index = result.first->second;

    return &m_constantPoolRegisters[index];
}

unsigned BytecodeGenerator::addRegExp(RegExp* r)
{
    return m_codeBlock->addRegExp(r);
}

RegisterID* BytecodeGenerator::emitMove(RegisterID* dst, RegisterID* src)
{
    emitOpcode(op_mov);
    instructions().append(dst->index());
    instructions().append(src->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitUnaryOp(OpcodeID opcodeID, RegisterID* dst, RegisterID* src)
{
    emitOpcode(opcodeID);
    instructions().append(dst->index());
    instructions().append(src->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitPreInc(RegisterID* srcDst)
{
    emitOpcode(op_pre_inc);
    instructions().append(srcDst->index());
    return srcDst;
}

RegisterID* BytecodeGenerator::emitPreDec(RegisterID* srcDst)
{
    emitOpcode(op_pre_dec);
    instructions().append(srcDst->index());
    return srcDst;
}

RegisterID* BytecodeGenerator::emitPostInc(RegisterID* dst, RegisterID* srcDst)
{
    emitOpcode(op_post_inc);
    instructions().append(dst->index());
    instructions().append(srcDst->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitPostDec(RegisterID* dst, RegisterID* srcDst)
{
    emitOpcode(op_post_dec);
    instructions().append(dst->index());
    instructions().append(srcDst->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitBinaryOp(OpcodeID opcodeID, RegisterID* dst, RegisterID* src1, RegisterID* src2, OperandTypes types)
{
    emitOpcode(opcodeID);
    instructions().append(dst->index());
    instructions().append(src1->index());
    instructions().append(src2->index());

    if (opcodeID == op_bitor || opcodeID == op_bitand || opcodeID == op_bitxor ||
        opcodeID == op_add || opcodeID == op_mul || opcodeID == op_sub || opcodeID == op_div)
        instructions().append(types.toInt());

    return dst;
}

RegisterID* BytecodeGenerator::emitEqualityOp(OpcodeID opcodeID, RegisterID* dst, RegisterID* src1, RegisterID* src2)
{
    if (m_lastOpcodeID == op_typeof) {
        int dstIndex;
        int srcIndex;

        retrieveLastUnaryOp(dstIndex, srcIndex);

        if (src1->index() == dstIndex
            && src1->isTemporary()
            && m_codeBlock->isConstantRegisterIndex(src2->index())
            && m_codeBlock->constantRegister(src2->index()).jsValue().isString()) {
            const UString& value = asString(m_codeBlock->constantRegister(src2->index()).jsValue())->value();
            if (value == "undefined") {
                rewindUnaryOp();
                emitOpcode(op_is_undefined);
                instructions().append(dst->index());
                instructions().append(srcIndex);
                return dst;
            }
            if (value == "boolean") {
                rewindUnaryOp();
                emitOpcode(op_is_boolean);
                instructions().append(dst->index());
                instructions().append(srcIndex);
                return dst;
            }
            if (value == "number") {
                rewindUnaryOp();
                emitOpcode(op_is_number);
                instructions().append(dst->index());
                instructions().append(srcIndex);
                return dst;
            }
            if (value == "string") {
                rewindUnaryOp();
                emitOpcode(op_is_string);
                instructions().append(dst->index());
                instructions().append(srcIndex);
                return dst;
            }
            if (value == "object") {
                rewindUnaryOp();
                emitOpcode(op_is_object);
                instructions().append(dst->index());
                instructions().append(srcIndex);
                return dst;
            }
            if (value == "function") {
                rewindUnaryOp();
                emitOpcode(op_is_function);
                instructions().append(dst->index());
                instructions().append(srcIndex);
                return dst;
            }
        }
    }

    emitOpcode(opcodeID);
    instructions().append(dst->index());
    instructions().append(src1->index());
    instructions().append(src2->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, bool b)
{
    return emitLoad(dst, jsBoolean(b));
}

RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, double number)
{
    // FIXME: Our hash tables won't hold infinity, so we make a new JSNumberCell each time.
    // Later we can do the extra work to handle that like the other cases.
    if (number == HashTraits<double>::emptyValue() || HashTraits<double>::isDeletedValue(number))
        return emitLoad(dst, jsNumber(globalData(), number));
    JSValue& valueInMap = m_numberMap.add(number, JSValue()).first->second;
    if (!valueInMap)
        valueInMap = jsNumber(globalData(), number);
    return emitLoad(dst, valueInMap);
}

RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, const Identifier& identifier)
{
    JSString*& stringInMap = m_stringMap.add(identifier.ustring().rep(), 0).first->second;
    if (!stringInMap)
        stringInMap = jsOwnedString(globalData(), identifier.ustring());
    return emitLoad(dst, JSValue(stringInMap));
}

RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, JSValue v)
{
    RegisterID* constantID = addConstantValue(v);
    if (dst)
        return emitMove(dst, constantID);
    return constantID;
}

bool BytecodeGenerator::findScopedProperty(const Identifier& property, int& index, size_t& stackDepth, bool forWriting, JSObject*& globalObject)
{
    // Cases where we cannot statically optimize the lookup.
    if (property == propertyNames().arguments || !canOptimizeNonLocals()) {
        stackDepth = 0;
        index = missingSymbolMarker();

        if (shouldOptimizeLocals() && m_codeType == GlobalCode) {
            ScopeChainIterator iter = m_scopeChain->begin();
            globalObject = *iter;
            ASSERT((++iter) == m_scopeChain->end());
        }
        return false;
    }

    size_t depth = 0;

    ScopeChainIterator iter = m_scopeChain->begin();
    ScopeChainIterator end = m_scopeChain->end();
    for (; iter != end; ++iter, ++depth) {
        JSObject* currentScope = *iter;
        if (!currentScope->isVariableObject())
            break;
        JSVariableObject* currentVariableObject = static_cast<JSVariableObject*>(currentScope);
        SymbolTableEntry entry = currentVariableObject->symbolTable().get(property.ustring().rep());

        // Found the property
        if (!entry.isNull()) {
            if (entry.isReadOnly() && forWriting) {
                stackDepth = 0;
                index = missingSymbolMarker();
                if (++iter == end)
                    globalObject = currentVariableObject;
                return false;
            }
            stackDepth = depth;
            index = entry.getIndex();
            if (++iter == end)
                globalObject = currentVariableObject;
            return true;
        }
        if (currentVariableObject->isDynamicScope())
            break;
    }

    // Can't locate the property but we're able to avoid a few lookups.
    stackDepth = depth;
    index = missingSymbolMarker();
    JSObject* scope = *iter;
    if (++iter == end)
        globalObject = scope;
    return true;
}

RegisterID* BytecodeGenerator::emitInstanceOf(RegisterID* dst, RegisterID* value, RegisterID* base, RegisterID* basePrototype)
{
    emitOpcode(op_instanceof);
    instructions().append(dst->index());
    instructions().append(value->index());
    instructions().append(base->index());
    instructions().append(basePrototype->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitResolve(RegisterID* dst, const Identifier& property)
{
    size_t depth = 0;
    int index = 0;
    JSObject* globalObject = 0;
    if (!findScopedProperty(property, index, depth, false, globalObject) && !globalObject) {
        // We can't optimise at all :-(
        emitOpcode(op_resolve);
        instructions().append(dst->index());
        instructions().append(addConstant(property));
        return dst;
    }

    if (globalObject) {
        bool forceGlobalResolve = false;
        if (m_regeneratingForExceptionInfo) {
#if ENABLE(JIT)
            forceGlobalResolve = m_codeBlockBeingRegeneratedFrom->hasGlobalResolveInfoAtBytecodeOffset(instructions().size());
#else
            forceGlobalResolve = m_codeBlockBeingRegeneratedFrom->hasGlobalResolveInstructionAtBytecodeOffset(instructions().size());
#endif
        }

        if (index != missingSymbolMarker() && !forceGlobalResolve) {
            // Directly index the property lookup across multiple scopes.
            return emitGetScopedVar(dst, depth, index, globalObject);
        }

#if ENABLE(JIT)
        m_codeBlock->addGlobalResolveInfo(instructions().size());
#else
        m_codeBlock->addGlobalResolveInstruction(instructions().size());
#endif
        emitOpcode(op_resolve_global);
        instructions().append(dst->index());
        instructions().append(globalObject);
        instructions().append(addConstant(property));
        instructions().append(0);
        instructions().append(0);
        return dst;
    }

    if (index != missingSymbolMarker()) {
        // Directly index the property lookup across multiple scopes.
        return emitGetScopedVar(dst, depth, index, globalObject);
    }

    // In this case we are at least able to drop a few scope chains from the
    // lookup chain, although we still need to hash from then on.
    emitOpcode(op_resolve_skip);
    instructions().append(dst->index());
    instructions().append(addConstant(property));
    instructions().append(depth);
    return dst;
}

RegisterID* BytecodeGenerator::emitGetScopedVar(RegisterID* dst, size_t depth, int index, JSValue globalObject)
{
    if (globalObject) {
        emitOpcode(op_get_global_var);
        instructions().append(dst->index());
        instructions().append(asCell(globalObject));
        instructions().append(index);
        return dst;
    }

    emitOpcode(op_get_scoped_var);
    instructions().append(dst->index());
    instructions().append(index);
    instructions().append(depth);
    return dst;
}

RegisterID* BytecodeGenerator::emitPutScopedVar(size_t depth, int index, RegisterID* value, JSValue globalObject)
{
    if (globalObject) {
        emitOpcode(op_put_global_var);
        instructions().append(asCell(globalObject));
        instructions().append(index);
        instructions().append(value->index());
        return value;
    }
    emitOpcode(op_put_scoped_var);
    instructions().append(index);
    instructions().append(depth);
    instructions().append(value->index());
    return value;
}

RegisterID* BytecodeGenerator::emitResolveBase(RegisterID* dst, const Identifier& property)
{
    size_t depth = 0;
    int index = 0;
    JSObject* globalObject = 0;
    findScopedProperty(property, index, depth, false, globalObject);
    if (!globalObject) {
        // We can't optimise at all :-(
        emitOpcode(op_resolve_base);
        instructions().append(dst->index());
        instructions().append(addConstant(property));
        return dst;
    }

    // Global object is the base
    return emitLoad(dst, JSValue(globalObject));
}

RegisterID* BytecodeGenerator::emitResolveWithBase(RegisterID* baseDst, RegisterID* propDst, const Identifier& property)
{
    size_t depth = 0;
    int index = 0;
    JSObject* globalObject = 0;
    if (!findScopedProperty(property, index, depth, false, globalObject) || !globalObject) {
        // We can't optimise at all :-(
        emitOpcode(op_resolve_with_base);
        instructions().append(baseDst->index());
        instructions().append(propDst->index());
        instructions().append(addConstant(property));
        return baseDst;
    }

    bool forceGlobalResolve = false;
    if (m_regeneratingForExceptionInfo) {
#if ENABLE(JIT)
        forceGlobalResolve = m_codeBlockBeingRegeneratedFrom->hasGlobalResolveInfoAtBytecodeOffset(instructions().size());
#else
        forceGlobalResolve = m_codeBlockBeingRegeneratedFrom->hasGlobalResolveInstructionAtBytecodeOffset(instructions().size());
#endif
    }

    // Global object is the base
    emitLoad(baseDst, JSValue(globalObject));

    if (index != missingSymbolMarker() && !forceGlobalResolve) {
        // Directly index the property lookup across multiple scopes.
        emitGetScopedVar(propDst, depth, index, globalObject);
        return baseDst;
    }

#if ENABLE(JIT)
    m_codeBlock->addGlobalResolveInfo(instructions().size());
#else
    m_codeBlock->addGlobalResolveInstruction(instructions().size());
#endif
    emitOpcode(op_resolve_global);
    instructions().append(propDst->index());
    instructions().append(globalObject);
    instructions().append(addConstant(property));
    instructions().append(0);
    instructions().append(0);
    return baseDst;
}

void BytecodeGenerator::emitMethodCheck()
{
    emitOpcode(op_method_check);
}

RegisterID* BytecodeGenerator::emitGetById(RegisterID* dst, RegisterID* base, const Identifier& property)
{
#if ENABLE(JIT)
    m_codeBlock->addStructureStubInfo(StructureStubInfo(access_get_by_id));
#else
    m_codeBlock->addPropertyAccessInstruction(instructions().size());
#endif

    emitOpcode(op_get_by_id);
    instructions().append(dst->index());
    instructions().append(base->index());
    instructions().append(addConstant(property));
    instructions().append(0);
    instructions().append(0);
    instructions().append(0);
    instructions().append(0);
    return dst;
}

RegisterID* BytecodeGenerator::emitPutById(RegisterID* base, const Identifier& property, RegisterID* value)
{
#if ENABLE(JIT)
    m_codeBlock->addStructureStubInfo(StructureStubInfo(access_put_by_id));
#else
    m_codeBlock->addPropertyAccessInstruction(instructions().size());
#endif

    emitOpcode(op_put_by_id);
    instructions().append(base->index());
    instructions().append(addConstant(property));
    instructions().append(value->index());
    instructions().append(0);
    instructions().append(0);
    instructions().append(0);
    instructions().append(0);
    return value;
}

RegisterID* BytecodeGenerator::emitPutGetter(RegisterID* base, const Identifier& property, RegisterID* value)
{
    emitOpcode(op_put_getter);
    instructions().append(base->index());
    instructions().append(addConstant(property));
    instructions().append(value->index());
    return value;
}

RegisterID* BytecodeGenerator::emitPutSetter(RegisterID* base, const Identifier& property, RegisterID* value)
{
    emitOpcode(op_put_setter);
    instructions().append(base->index());
    instructions().append(addConstant(property));
    instructions().append(value->index());
    return value;
}

RegisterID* BytecodeGenerator::emitDeleteById(RegisterID* dst, RegisterID* base, const Identifier& property)
{
    emitOpcode(op_del_by_id);
    instructions().append(dst->index());
    instructions().append(base->index());
    instructions().append(addConstant(property));
    return dst;
}

RegisterID* BytecodeGenerator::emitGetByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    emitOpcode(op_get_by_val);
    instructions().append(dst->index());
    instructions().append(base->index());
    instructions().append(property->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitPutByVal(RegisterID* base, RegisterID* property, RegisterID* value)
{
    emitOpcode(op_put_by_val);
    instructions().append(base->index());
    instructions().append(property->index());
    instructions().append(value->index());
    return value;
}

RegisterID* BytecodeGenerator::emitDeleteByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    emitOpcode(op_del_by_val);
    instructions().append(dst->index());
    instructions().append(base->index());
    instructions().append(property->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitPutByIndex(RegisterID* base, unsigned index, RegisterID* value)
{
    emitOpcode(op_put_by_index);
    instructions().append(base->index());
    instructions().append(index);
    instructions().append(value->index());
    return value;
}

RegisterID* BytecodeGenerator::emitNewObject(RegisterID* dst)
{
    emitOpcode(op_new_object);
    instructions().append(dst->index());
    return dst;
}

RegisterID* BytecodeGenerator::emitNewArray(RegisterID* dst, ElementNode* elements)
{
    Vector<RefPtr<RegisterID>, 16> argv;
    for (ElementNode* n = elements; n; n = n->next()) {
        if (n->elision())
            break;
        argv.append(newTemporary());
        // op_new_array requires the initial values to be a sequential range of registers
        ASSERT(argv.size() == 1 || argv[argv.size() - 1]->index() == argv[argv.size() - 2]->index() + 1);
        emitNode(argv.last().get(), n->value());
    }
    emitOpcode(op_new_array);
    instructions().append(dst->index());
    instructions().append(argv.size() ? argv[0]->index() : 0); // argv
    instructions().append(argv.size()); // argc
    return dst;
}

RegisterID* BytecodeGenerator::emitNewFunction(RegisterID* dst, FuncDeclNode* n)
{
    emitOpcode(op_new_func);
    instructions().append(dst->index());
    instructions().append(addConstant(n));
    return dst;
}

RegisterID* BytecodeGenerator::emitNewRegExp(RegisterID* dst, RegExp* regExp)
{
    emitOpcode(op_new_regexp);
    instructions().append(dst->index());
    instructions().append(addRegExp(regExp));
    return dst;
}


RegisterID* BytecodeGenerator::emitNewFunctionExpression(RegisterID* r0, FuncExprNode* n)
{
    emitOpcode(op_new_func_exp);
    instructions().append(r0->index());
    instructions().append(addConstant(n));
    return r0;
}

RegisterID* BytecodeGenerator::emitCall(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, ArgumentsNode* argumentsNode, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    return emitCall(op_call, dst, func, thisRegister, argumentsNode, divot, startOffset, endOffset);
}

void BytecodeGenerator::createArgumentsIfNecessary()
{
    if (m_codeBlock->usesArguments() && m_codeType == FunctionCode)
        emitOpcode(op_create_arguments);
}

RegisterID* BytecodeGenerator::emitCallEval(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, ArgumentsNode* argumentsNode, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    createArgumentsIfNecessary();
    return emitCall(op_call_eval, dst, func, thisRegister, argumentsNode, divot, startOffset, endOffset);
}

RegisterID* BytecodeGenerator::emitCall(OpcodeID opcodeID, RegisterID* dst, RegisterID* func, RegisterID* thisRegister, ArgumentsNode* argumentsNode, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    ASSERT(opcodeID == op_call || opcodeID == op_call_eval);
    ASSERT(func->refCount());
    ASSERT(thisRegister->refCount());

    RegisterID* originalFunc = func;
    if (m_shouldEmitProfileHooks) {
        // If codegen decided to recycle func as this call's destination register,
        // we need to undo that optimization here so that func will still be around
        // for the sake of op_profile_did_call.
        if (dst == func) {
            RefPtr<RegisterID> movedThisRegister = emitMove(newTemporary(), thisRegister);
            RefPtr<RegisterID> movedFunc = emitMove(thisRegister, func);

            thisRegister = movedThisRegister.release().releaseRef();
            func = movedFunc.release().releaseRef();
        }
    }

    // Generate code for arguments.
    Vector<RefPtr<RegisterID>, 16> argv;
    argv.append(thisRegister);
    for (ArgumentListNode* n = argumentsNode->m_listNode; n; n = n->m_next) {
        argv.append(newTemporary());
        // op_call requires the arguments to be a sequential range of registers
        ASSERT(argv[argv.size() - 1]->index() == argv[argv.size() - 2]->index() + 1);
        emitNode(argv.last().get(), n);
    }

    // Reserve space for call frame.
    Vector<RefPtr<RegisterID>, RegisterFile::CallFrameHeaderSize> callFrame;
    for (int i = 0; i < RegisterFile::CallFrameHeaderSize; ++i)
        callFrame.append(newTemporary());

    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_will_call);
        instructions().append(func->index());

#if ENABLE(JIT)
        m_codeBlock->addFunctionRegisterInfo(instructions().size(), func->index());
#endif
    }

    emitExpressionInfo(divot, startOffset, endOffset);

#if ENABLE(JIT)
    m_codeBlock->addCallLinkInfo();
#endif

    // Emit call.
    emitOpcode(opcodeID);
    instructions().append(dst->index()); // dst
    instructions().append(func->index()); // func
    instructions().append(argv.size()); // argCount
    instructions().append(argv[0]->index() + argv.size() + RegisterFile::CallFrameHeaderSize); // registerOffset

    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_did_call);
        instructions().append(func->index());

        if (dst == originalFunc) {
            thisRegister->deref();
            func->deref();
        }
    }

    return dst;
}

RegisterID* BytecodeGenerator::emitLoadVarargs(RegisterID* argCountDst, RegisterID* arguments)
{
    ASSERT(argCountDst->index() < arguments->index());
    emitOpcode(op_load_varargs);
    instructions().append(argCountDst->index());
    instructions().append(arguments->index());
    return argCountDst;
}

RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* argCountRegister, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    ASSERT(func->refCount());
    ASSERT(thisRegister->refCount());
    ASSERT(dst != func);
    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_will_call);
        instructions().append(func->index());

#if ENABLE(JIT)
        m_codeBlock->addFunctionRegisterInfo(instructions().size(), func->index());
#endif
    }

    emitExpressionInfo(divot, startOffset, endOffset);

    // Emit call.
    emitOpcode(op_call_varargs);
    instructions().append(dst->index()); // dst
    instructions().append(func->index()); // func
    instructions().append(argCountRegister->index()); // arg count
    instructions().append(thisRegister->index() + RegisterFile::CallFrameHeaderSize); // initial registerOffset
    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_did_call);
        instructions().append(func->index());
    }
    return dst;
}

RegisterID* BytecodeGenerator::emitReturn(RegisterID* src)
{
    if (m_codeBlock->needsFullScopeChain()) {
        emitOpcode(op_tear_off_activation);
        instructions().append(m_activationRegisterIndex);
    } else if (m_codeBlock->usesArguments() && m_codeBlock->m_numParameters > 1)
        emitOpcode(op_tear_off_arguments);

    return emitUnaryNoDstOp(op_ret, src);
}

RegisterID* BytecodeGenerator::emitUnaryNoDstOp(OpcodeID opcodeID, RegisterID* src)
{
    emitOpcode(opcodeID);
    instructions().append(src->index());
    return src;
}

RegisterID* BytecodeGenerator::emitConstruct(RegisterID* dst, RegisterID* func, ArgumentsNode* argumentsNode, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    ASSERT(func->refCount());

    RegisterID* originalFunc = func;
    if (m_shouldEmitProfileHooks) {
        // If codegen decided to recycle func as this call's destination register,
        // we need to undo that optimization here so that func will still be around
        // for the sake of op_profile_did_call.
        if (dst == func) {
            RefPtr<RegisterID> movedFunc = emitMove(newTemporary(), func);
            func = movedFunc.release().releaseRef();
        }
    }

    RefPtr<RegisterID> funcProto = newTemporary();

    // Generate code for arguments.
    Vector<RefPtr<RegisterID>, 16> argv;
    argv.append(newTemporary()); // reserve space for "this"
    for (ArgumentListNode* n = argumentsNode ? argumentsNode->m_listNode : 0; n; n = n->m_next) {
        argv.append(newTemporary());
        // op_construct requires the arguments to be a sequential range of registers
        ASSERT(argv[argv.size() - 1]->index() == argv[argv.size() - 2]->index() + 1);
        emitNode(argv.last().get(), n);
    }

    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_will_call);
        instructions().append(func->index());
    }

    // Load prototype.
    emitExpressionInfo(divot, startOffset, endOffset);
    emitGetByIdExceptionInfo(op_construct);
    emitGetById(funcProto.get(), func, globalData()->propertyNames->prototype);

    // Reserve space for call frame.
    Vector<RefPtr<RegisterID>, RegisterFile::CallFrameHeaderSize> callFrame;
    for (int i = 0; i < RegisterFile::CallFrameHeaderSize; ++i)
        callFrame.append(newTemporary());

    emitExpressionInfo(divot, startOffset, endOffset);

#if ENABLE(JIT)
    m_codeBlock->addCallLinkInfo();
#endif

    emitOpcode(op_construct);
    instructions().append(dst->index()); // dst
    instructions().append(func->index()); // func
    instructions().append(argv.size()); // argCount
    instructions().append(argv[0]->index() + argv.size() + RegisterFile::CallFrameHeaderSize); // registerOffset
    instructions().append(funcProto->index()); // proto
    instructions().append(argv[0]->index()); // thisRegister

    emitOpcode(op_construct_verify);
    instructions().append(dst->index());
    instructions().append(argv[0]->index());

    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_did_call);
        instructions().append(func->index());

        if (dst == originalFunc)
            func->deref();
    }

    return dst;
}

RegisterID* BytecodeGenerator::emitStrcat(RegisterID* dst, RegisterID* src, int count)
{
    emitOpcode(op_strcat);
    instructions().append(dst->index());
    instructions().append(src->index());
    instructions().append(count);

    return dst;
}

void BytecodeGenerator::emitToPrimitive(RegisterID* dst, RegisterID* src)
{
    emitOpcode(op_to_primitive);
    instructions().append(dst->index());
    instructions().append(src->index());
}

RegisterID* BytecodeGenerator::emitPushScope(RegisterID* scope)
{
    ASSERT(scope->isTemporary());
    ControlFlowContext context;
    context.isFinallyBlock = false;
    m_scopeContextStack.append(context);
    m_dynamicScopeDepth++;
    createArgumentsIfNecessary();

    return emitUnaryNoDstOp(op_push_scope, scope);
}

void BytecodeGenerator::emitPopScope()
{
    ASSERT(m_scopeContextStack.size());
    ASSERT(!m_scopeContextStack.last().isFinallyBlock);

    emitOpcode(op_pop_scope);

    m_scopeContextStack.removeLast();
    m_dynamicScopeDepth--;
}

void BytecodeGenerator::emitDebugHook(DebugHookID debugHookID, int firstLine, int lastLine)
{
    if (!m_shouldEmitDebugHooks)
        return;
    emitOpcode(op_debug);
    instructions().append(debugHookID);
    instructions().append(firstLine);
    instructions().append(lastLine);
}

void BytecodeGenerator::pushFinallyContext(Label* target, RegisterID* retAddrDst)
{
    ControlFlowContext scope;
    scope.isFinallyBlock = true;
    FinallyContext context = { target, retAddrDst };
    scope.finallyContext = context;
    m_scopeContextStack.append(scope);
    m_finallyDepth++;
}

void BytecodeGenerator::popFinallyContext()
{
    ASSERT(m_scopeContextStack.size());
    ASSERT(m_scopeContextStack.last().isFinallyBlock);
    ASSERT(m_finallyDepth > 0);
    m_scopeContextStack.removeLast();
    m_finallyDepth--;
}

LabelScope* BytecodeGenerator::breakTarget(const Identifier& name)
{
    // Reclaim free label scopes.
    //
    // The condition was previously coded as 'm_labelScopes.size() && !m_labelScopes.last().refCount()',
    // however sometimes this appears to lead to GCC going a little haywire and entering the loop with
    // size 0, leading to segfaulty badness.  We are yet to identify a valid cause within our code to
    // cause the GCC codegen to misbehave in this fashion, and as such the following refactoring of the
    // loop condition is a workaround.
    while (m_labelScopes.size()) {
        if  (m_labelScopes.last().refCount())
            break;
        m_labelScopes.removeLast();
    }

    if (!m_labelScopes.size())
        return 0;

    // We special-case the following, which is a syntax error in Firefox:
    // label:
    //     break;
    if (name.isEmpty()) {
        for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
            LabelScope* scope = &m_labelScopes[i];
            if (scope->type() != LabelScope::NamedLabel) {
                ASSERT(scope->breakTarget());
                return scope;
            }
        }
        return 0;
    }

    for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
        LabelScope* scope = &m_labelScopes[i];
        if (scope->name() && *scope->name() == name) {
            ASSERT(scope->breakTarget());
            return scope;
        }
    }
    return 0;
}

LabelScope* BytecodeGenerator::continueTarget(const Identifier& name)
{
    // Reclaim free label scopes.
    while (m_labelScopes.size() && !m_labelScopes.last().refCount())
        m_labelScopes.removeLast();

    if (!m_labelScopes.size())
        return 0;

    if (name.isEmpty()) {
        for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
            LabelScope* scope = &m_labelScopes[i];
            if (scope->type() == LabelScope::Loop) {
                ASSERT(scope->continueTarget());
                return scope;
            }
        }
        return 0;
    }

    // Continue to the loop nested nearest to the label scope that matches
    // 'name'.
    LabelScope* result = 0;
    for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
        LabelScope* scope = &m_labelScopes[i];
        if (scope->type() == LabelScope::Loop) {
            ASSERT(scope->continueTarget());
            result = scope;
        }
        if (scope->name() && *scope->name() == name)
            return result; // may be 0
    }
    return 0;
}

PassRefPtr<Label> BytecodeGenerator::emitComplexJumpScopes(Label* target, ControlFlowContext* topScope, ControlFlowContext* bottomScope)
{
    while (topScope > bottomScope) {
        // First we count the number of dynamic scopes we need to remove to get
        // to a finally block.
        int nNormalScopes = 0;
        while (topScope > bottomScope) {
            if (topScope->isFinallyBlock)
                break;
            ++nNormalScopes;
            --topScope;
        }

        if (nNormalScopes) {
            // We need to remove a number of dynamic scopes to get to the next
            // finally block
            emitOpcode(op_jmp_scopes);
            instructions().append(nNormalScopes);

            // If topScope == bottomScope then there isn't actually a finally block
            // left to emit, so make the jmp_scopes jump directly to the target label
            if (topScope == bottomScope) {
                instructions().append(target->offsetFrom(instructions().size()));
                return target;
            }

            // Otherwise we just use jmp_scopes to pop a group of scopes and go
            // to the next instruction
            RefPtr<Label> nextInsn = newLabel();
            instructions().append(nextInsn->offsetFrom(instructions().size()));
            emitLabel(nextInsn.get());
        }

        while (topScope > bottomScope && topScope->isFinallyBlock) {
            emitJumpSubroutine(topScope->finallyContext.retAddrDst, topScope->finallyContext.finallyAddr);
            --topScope;
        }
    }
    return emitJump(target);
}

PassRefPtr<Label> BytecodeGenerator::emitJumpScopes(Label* target, int targetScopeDepth)
{
    ASSERT(scopeDepth() - targetScopeDepth >= 0);
    ASSERT(target->isForward());

    size_t scopeDelta = scopeDepth() - targetScopeDepth;
    ASSERT(scopeDelta <= m_scopeContextStack.size());
    if (!scopeDelta)
        return emitJump(target);

    if (m_finallyDepth)
        return emitComplexJumpScopes(target, &m_scopeContextStack.last(), &m_scopeContextStack.last() - scopeDelta);

    emitOpcode(op_jmp_scopes);
    instructions().append(scopeDelta);
    instructions().append(target->offsetFrom(instructions().size()));
    return target;
}

RegisterID* BytecodeGenerator::emitNextPropertyName(RegisterID* dst, RegisterID* iter, Label* target)
{
    emitOpcode(op_next_pname);
    instructions().append(dst->index());
    instructions().append(iter->index());
    instructions().append(target->offsetFrom(instructions().size()));
    return dst;
}

RegisterID* BytecodeGenerator::emitCatch(RegisterID* targetRegister, Label* start, Label* end)
{
#if ENABLE(JIT)
    HandlerInfo info = { start->offsetFrom(0), end->offsetFrom(0), instructions().size(), m_dynamicScopeDepth + m_baseScopeDepth, CodeLocationLabel() };
#else
    HandlerInfo info = { start->offsetFrom(0), end->offsetFrom(0), instructions().size(), m_dynamicScopeDepth + m_baseScopeDepth };
#endif

    m_codeBlock->addExceptionHandler(info);
    emitOpcode(op_catch);
    instructions().append(targetRegister->index());
    return targetRegister;
}

RegisterID* BytecodeGenerator::emitNewError(RegisterID* dst, ErrorType type, JSValue message)
{
    emitOpcode(op_new_error);
    instructions().append(dst->index());
    instructions().append(static_cast<int>(type));
    instructions().append(addConstantValue(message)->index());
    return dst;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpSubroutine(RegisterID* retAddrDst, Label* finally)
{
    emitOpcode(op_jsr);
    instructions().append(retAddrDst->index());
    instructions().append(finally->offsetFrom(instructions().size()));
    emitLabel(newLabel().get()); // Record the fact that the next instruction is implicitly labeled, because op_sret will return to it.
    return finally;
}

void BytecodeGenerator::emitSubroutineReturn(RegisterID* retAddrSrc)
{
    emitOpcode(op_sret);
    instructions().append(retAddrSrc->index());
}

void BytecodeGenerator::emitPushNewScope(RegisterID* dst, Identifier& property, RegisterID* value)
{
    ControlFlowContext context;
    context.isFinallyBlock = false;
    m_scopeContextStack.append(context);
    m_dynamicScopeDepth++;

    createArgumentsIfNecessary();

    emitOpcode(op_push_new_scope);
    instructions().append(dst->index());
    instructions().append(addConstant(property));
    instructions().append(value->index());
}

void BytecodeGenerator::beginSwitch(RegisterID* scrutineeRegister, SwitchInfo::SwitchType type)
{
    SwitchInfo info = { instructions().size(), type };
    switch (type) {
        case SwitchInfo::SwitchImmediate:
            emitOpcode(op_switch_imm);
            break;
        case SwitchInfo::SwitchCharacter:
            emitOpcode(op_switch_char);
            break;
        case SwitchInfo::SwitchString:
            emitOpcode(op_switch_string);
            break;
        default:
            ASSERT_NOT_REACHED();
    }

    instructions().append(0); // place holder for table index
    instructions().append(0); // place holder for default target
    instructions().append(scrutineeRegister->index());
    m_switchContextStack.append(info);
}

static int32_t keyForImmediateSwitch(ExpressionNode* node, int32_t min, int32_t max)
{
    UNUSED_PARAM(max);
    ASSERT(node->isNumber());
    double value = static_cast<NumberNode*>(node)->value();
    int32_t key = static_cast<int32_t>(value);
    ASSERT(key == value);
    ASSERT(key >= min);
    ASSERT(key <= max);
    return key - min;
}

static void prepareJumpTableForImmediateSwitch(SimpleJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, int32_t min, int32_t max)
{
    jumpTable.min = min;
    jumpTable.branchOffsets.resize(max - min + 1);
    jumpTable.branchOffsets.fill(0);
    for (uint32_t i = 0; i < clauseCount; ++i) {
        // We're emitting this after the clause labels should have been fixed, so
        // the labels should not be "forward" references
        ASSERT(!labels[i]->isForward());
        jumpTable.add(keyForImmediateSwitch(nodes[i], min, max), labels[i]->offsetFrom(switchAddress));
    }
}

static int32_t keyForCharacterSwitch(ExpressionNode* node, int32_t min, int32_t max)
{
    UNUSED_PARAM(max);
    ASSERT(node->isString());
    UString::Rep* clause = static_cast<StringNode*>(node)->value().ustring().rep();
    ASSERT(clause->size() == 1);

    int32_t key = clause->data()[0];
    ASSERT(key >= min);
    ASSERT(key <= max);
    return key - min;
}

static void prepareJumpTableForCharacterSwitch(SimpleJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, int32_t min, int32_t max)
{
    jumpTable.min = min;
    jumpTable.branchOffsets.resize(max - min + 1);
    jumpTable.branchOffsets.fill(0);
    for (uint32_t i = 0; i < clauseCount; ++i) {
        // We're emitting this after the clause labels should have been fixed, so
        // the labels should not be "forward" references
        ASSERT(!labels[i]->isForward());
        jumpTable.add(keyForCharacterSwitch(nodes[i], min, max), labels[i]->offsetFrom(switchAddress));
    }
}

static void prepareJumpTableForStringSwitch(StringJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes)
{
    for (uint32_t i = 0; i < clauseCount; ++i) {
        // We're emitting this after the clause labels should have been fixed, so
        // the labels should not be "forward" references
        ASSERT(!labels[i]->isForward());

        ASSERT(nodes[i]->isString());
        UString::Rep* clause = static_cast<StringNode*>(nodes[i])->value().ustring().rep();
        OffsetLocation location;
        location.branchOffset = labels[i]->offsetFrom(switchAddress);
        jumpTable.offsetTable.add(clause, location);
    }
}

void BytecodeGenerator::endSwitch(uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, Label* defaultLabel, int32_t min, int32_t max)
{
    SwitchInfo switchInfo = m_switchContextStack.last();
    m_switchContextStack.removeLast();
    if (switchInfo.switchType == SwitchInfo::SwitchImmediate) {
        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfImmediateSwitchJumpTables();
        instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->offsetFrom(switchInfo.bytecodeOffset + 3);

        SimpleJumpTable& jumpTable = m_codeBlock->addImmediateSwitchJumpTable();
        prepareJumpTableForImmediateSwitch(jumpTable, switchInfo.bytecodeOffset + 3, clauseCount, labels, nodes, min, max);
    } else if (switchInfo.switchType == SwitchInfo::SwitchCharacter) {
        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfCharacterSwitchJumpTables();
        instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->offsetFrom(switchInfo.bytecodeOffset + 3);

        SimpleJumpTable& jumpTable = m_codeBlock->addCharacterSwitchJumpTable();
        prepareJumpTableForCharacterSwitch(jumpTable, switchInfo.bytecodeOffset + 3, clauseCount, labels, nodes, min, max);
    } else {
        ASSERT(switchInfo.switchType == SwitchInfo::SwitchString);
        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfStringSwitchJumpTables();
        instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->offsetFrom(switchInfo.bytecodeOffset + 3);

        StringJumpTable& jumpTable = m_codeBlock->addStringSwitchJumpTable();
        prepareJumpTableForStringSwitch(jumpTable, switchInfo.bytecodeOffset + 3, clauseCount, labels, nodes);
    }
}

RegisterID* BytecodeGenerator::emitThrowExpressionTooDeepException()
{
    // It would be nice to do an even better job of identifying exactly where the expression is.
    // And we could make the caller pass the node pointer in, if there was some way of getting
    // that from an arbitrary node. However, calling emitExpressionInfo without any useful data
    // is still good enough to get us an accurate line number.
    emitExpressionInfo(0, 0, 0);
    RegisterID* exception = emitNewError(newTemporary(), SyntaxError, jsString(globalData(), "Expression too deep"));
    emitThrow(exception);
    return exception;
}

} // namespace JSC