src/third_party/WebKit/Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp

/*
 * Copyright (C) 2008, 2009, 2012 Apple Inc. All rights reserved.
 * Copyright (C) 2008 Cameron Zwarich <cwzwarich@uwaterloo.ca>
 * Copyright (C) 2012 Igalia, S.L.
 *
 * 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 "Comment.h"
#include "Interpreter.h"
#include "JSActivation.h"
#include "JSFunction.h"
#include "JSNameScope.h"
#include "LowLevelInterpreter.h"
#include "Options.h"
#include "StrongInlines.h"
#include <wtf/text/WTFString.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.
*/

void Label::setLocation(unsigned location)
{
    m_location = location;
    
    unsigned size = m_unresolvedJumps.size();
    for (unsigned i = 0; i < size; ++i)
        m_generator->m_instructions[m_unresolvedJumps[i].second].u.operand = m_location - m_unresolvedJumps[i].first;
}

#ifndef NDEBUG
void ResolveResult::checkValidity()
{
    switch (m_type) {
    case Register:
    case ReadOnlyRegister:
        ASSERT(m_local);
        return;
    case Dynamic:
        ASSERT(!m_local);
        return;
    default:
        ASSERT_NOT_REACHED();
    }
}
#endif

ParserError BytecodeGenerator::generate()
{
    SamplingRegion samplingRegion("Bytecode Generation");
    
    m_codeBlock->setThisRegister(m_thisRegister.index());

    m_scopeNode->emitBytecode(*this);
    
    for (unsigned i = 0; i < m_tryRanges.size(); ++i) {
        TryRange& range = m_tryRanges[i];
        int start = range.start->bind();
        int end = range.end->bind();
        
        // This will happen for empty try blocks and for some cases of finally blocks:
        //
        // try {
        //    try {
        //    } finally {
        //        return 42;
        //        // *HERE*
        //    }
        // } finally {
        //    print("things");
        // }
        //
        // The return will pop scopes to execute the outer finally block. But this includes
        // popping the try context for the inner try. The try context is live in the fall-through
        // part of the finally block not because we will emit a handler that overlaps the finally,
        // but because we haven't yet had a chance to plant the catch target. Then when we finish
        // emitting code for the outer finally block, we repush the try contex, this time with a
        // new start index. But that means that the start index for the try range corresponding
        // to the inner-finally-following-the-return (marked as "*HERE*" above) will be greater
        // than the end index of the try block. This is harmless since end < start handlers will
        // never get matched in our logic, but we do the runtime a favor and choose to not emit
        // such handlers at all.
        if (end <= start)
            continue;
        
        ASSERT(range.tryData->targetScopeDepth != UINT_MAX);
        UnlinkedHandlerInfo info = {
            static_cast<uint32_t>(start), static_cast<uint32_t>(end),
            static_cast<uint32_t>(range.tryData->target->bind()),
            range.tryData->targetScopeDepth
        };
        m_codeBlock->addExceptionHandler(info);
    }
    
    m_codeBlock->instructions() = RefCountedArray<UnlinkedInstruction>(m_instructions);

    m_codeBlock->shrinkToFit();

    if (m_expressionTooDeep)
        return ParserError::OutOfMemory;
    return ParserError::ErrorNone;
}

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

    if (!result.isNewEntry) {
        r0 = &registerFor(result.iterator->value.getIndex());
        return false;
    }

    r0 = addVar();
    return true;
}

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

BytecodeGenerator::BytecodeGenerator(JSGlobalData& globalData, ProgramNode* programNode, UnlinkedProgramCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
    : m_shouldEmitDebugHooks(debuggerMode == DebuggerOn)
    , m_shouldEmitProfileHooks(profilerMode == ProfilerOn)
#if ENABLE(BYTECODE_COMMENTS)
    , m_currentCommentString(0)
#endif
    , m_symbolTable(0)
    , m_scopeNode(programNode)
    , m_codeBlock(globalData, codeBlock)
    , m_thisRegister(CallFrame::thisArgumentOffset())
    , m_emptyValueRegister(0)
    , m_finallyDepth(0)
    , m_dynamicScopeDepth(0)
    , m_codeType(GlobalCode)
    , m_nextConstantOffset(0)
    , m_globalConstantIndex(0)
    , m_hasCreatedActivation(true)
    , m_firstLazyFunction(0)
    , m_lastLazyFunction(0)
    , m_globalData(&globalData)
    , m_lastOpcodeID(op_end)
#ifndef NDEBUG
    , m_lastOpcodePosition(0)
#endif
    , m_stack(wtfThreadData().stack())
    , m_usesExceptions(false)
    , m_expressionTooDeep(false)
{
    if (m_shouldEmitDebugHooks)
        m_codeBlock->setNeedsFullScopeChain(true);

    m_codeBlock->setNumParameters(1); // Allocate space for "this"

    prependComment("entering Program block");
    emitOpcode(op_enter);

    const VarStack& varStack = programNode->varStack();
    const FunctionStack& functionStack = programNode->functionStack();

    for (size_t i = 0; i < functionStack.size(); ++i) {
        FunctionBodyNode* function = functionStack[i];
        UnlinkedFunctionExecutable* unlinkedFunction = makeFunction(function);
        codeBlock->addFunctionDeclaration(*m_globalData, function->ident(), unlinkedFunction);
    }

    for (size_t i = 0; i < varStack.size(); ++i)
        codeBlock->addVariableDeclaration(*varStack[i].first, !!(varStack[i].second & DeclarationStacks::IsConstant));

}

BytecodeGenerator::BytecodeGenerator(JSGlobalData& globalData, FunctionBodyNode* functionBody, UnlinkedFunctionCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
    : m_shouldEmitDebugHooks(debuggerMode == DebuggerOn)
    , m_shouldEmitProfileHooks(profilerMode == ProfilerOn)
    , m_symbolTable(codeBlock->symbolTable())
#if ENABLE(BYTECODE_COMMENTS)
    , m_currentCommentString(0)
#endif
    , m_scopeNode(functionBody)
    , m_codeBlock(globalData, codeBlock)
    , m_activationRegister(0)
    , m_emptyValueRegister(0)
    , m_finallyDepth(0)
    , m_dynamicScopeDepth(0)
    , m_codeType(FunctionCode)
    , m_nextConstantOffset(0)
    , m_globalConstantIndex(0)
    , m_hasCreatedActivation(false)
    , m_firstLazyFunction(0)
    , m_lastLazyFunction(0)
    , m_globalData(&globalData)
    , m_lastOpcodeID(op_end)
#ifndef NDEBUG
    , m_lastOpcodePosition(0)
#endif
    , m_stack(wtfThreadData().stack())
    , m_usesExceptions(false)
    , m_expressionTooDeep(false)
{
    if (m_shouldEmitDebugHooks)
        m_codeBlock->setNeedsFullScopeChain(true);

    m_symbolTable->setUsesNonStrictEval(codeBlock->usesEval() && !codeBlock->isStrictMode());
    m_symbolTable->setParameterCountIncludingThis(functionBody->parameters()->size() + 1);

    prependComment("entering Function block");
    emitOpcode(op_enter);
    if (m_codeBlock->needsFullScopeChain()) {
        m_activationRegister = addVar();
        prependComment("activation for Full Scope Chain");
        emitInitLazyRegister(m_activationRegister);
        m_codeBlock->setActivationRegister(m_activationRegister->index());
    }

    m_symbolTable->setCaptureStart(m_codeBlock->m_numVars);

    if (functionBody->usesArguments() || codeBlock->usesEval() || m_shouldEmitDebugHooks) { // May reify arguments object.
        RegisterID* unmodifiedArgumentsRegister = addVar(); // Anonymous, so it can't be modified by user code.
        RegisterID* argumentsRegister = addVar(propertyNames().arguments, false); // Can be changed by assigning to 'arguments'.

        // We can save a little space by hard-coding the knowledge that the two
        // 'arguments' values are stored in consecutive registers, and storing
        // only the index of the assignable one.
        codeBlock->setArgumentsRegister(argumentsRegister->index());
        ASSERT_UNUSED(unmodifiedArgumentsRegister, unmodifiedArgumentsRegister->index() == JSC::unmodifiedArgumentsRegister(codeBlock->argumentsRegister()));

        prependComment("arguments for Full Scope Chain");
        emitInitLazyRegister(argumentsRegister);
        prependComment("unmodified arguments for Full Scope Chain");
        emitInitLazyRegister(unmodifiedArgumentsRegister);
        
        if (m_codeBlock->isStrictMode()) {
            prependComment("create arguments for strict mode");
            emitOpcode(op_create_arguments);
            instructions().append(argumentsRegister->index());
        }

        // 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) {
            prependComment("create arguments for debug hooks");
            emitOpcode(op_create_arguments);
            instructions().append(argumentsRegister->index());
        }
    }

    bool shouldCaptureAllTheThings = m_shouldEmitDebugHooks || codeBlock->usesEval();

    bool capturesAnyArgumentByName = false;
    Vector<RegisterID*> capturedArguments;
    if (functionBody->hasCapturedVariables() || shouldCaptureAllTheThings) {
        FunctionParameters& parameters = *functionBody->parameters();
        capturedArguments.resize(parameters.size());
        for (size_t i = 0; i < parameters.size(); ++i) {
            capturedArguments[i] = 0;
            if (!functionBody->captures(parameters[i]) && !shouldCaptureAllTheThings)
                continue;
            capturesAnyArgumentByName = true;
            capturedArguments[i] = addVar();
        }
    }

    if (capturesAnyArgumentByName && !codeBlock->isStrictMode()) {
        size_t parameterCount = m_symbolTable->parameterCount();
        OwnArrayPtr<SlowArgument> slowArguments = adoptArrayPtr(new SlowArgument[parameterCount]);
        for (size_t i = 0; i < parameterCount; ++i) {
            if (!capturedArguments[i]) {
                ASSERT(slowArguments[i].status == SlowArgument::Normal);
                slowArguments[i].index = CallFrame::argumentOffset(i);
                continue;
            }
            slowArguments[i].status = SlowArgument::Captured;
            slowArguments[i].index = capturedArguments[i]->index();
        }
        m_symbolTable->setSlowArguments(slowArguments.release());
    }

    RegisterID* calleeRegister = resolveCallee(functionBody); // May push to the scope chain and/or add a captured var.

    const DeclarationStacks::FunctionStack& functionStack = functionBody->functionStack();
    const DeclarationStacks::VarStack& varStack = functionBody->varStack();

    // Captured variables and functions go first so that activations don't have
    // to step over the non-captured locals to mark them.
    m_hasCreatedActivation = false;
    if (functionBody->hasCapturedVariables()) {
        for (size_t i = 0; i < functionStack.size(); ++i) {
            FunctionBodyNode* function = functionStack[i];
            const Identifier& ident = function->ident();
            if (functionBody->captures(ident)) {
                if (!m_hasCreatedActivation) {
                    m_hasCreatedActivation = true;
                    prependComment("activation for captured vars");
                    emitOpcode(op_create_activation);
                    instructions().append(m_activationRegister->index());
                }
                m_functions.add(ident.impl());
                prependComment("captured function var");
                emitNewFunction(addVar(ident, false), function);
            }
        }
        for (size_t i = 0; i < varStack.size(); ++i) {
            const Identifier& ident = *varStack[i].first;
            if (functionBody->captures(ident))
                addVar(ident, varStack[i].second & DeclarationStacks::IsConstant);
        }
    }
    bool canLazilyCreateFunctions = !functionBody->needsActivationForMoreThanVariables() && !m_shouldEmitDebugHooks;
    if (!canLazilyCreateFunctions && !m_hasCreatedActivation) {
        m_hasCreatedActivation = true;
        prependComment("cannot lazily create functions");
        emitOpcode(op_create_activation);
        instructions().append(m_activationRegister->index());
    }

    m_symbolTable->setCaptureEnd(codeBlock->m_numVars);

    m_firstLazyFunction = codeBlock->m_numVars;
    for (size_t i = 0; i < functionStack.size(); ++i) {
        FunctionBodyNode* function = functionStack[i];
        const Identifier& ident = function->ident();
        if (!functionBody->captures(ident)) {
            m_functions.add(ident.impl());
            RefPtr<RegisterID> reg = addVar(ident, false);
            // Don't lazily create functions that override the name 'arguments'
            // as this would complicate lazy instantiation of actual arguments.
            prependComment("a function that override 'arguments'");
            if (!canLazilyCreateFunctions || ident == propertyNames().arguments)
                emitNewFunction(reg.get(), function);
            else {
                emitInitLazyRegister(reg.get());
                m_lazyFunctions.set(reg->index(), function);
            }
        }
    }
    m_lastLazyFunction = canLazilyCreateFunctions ? codeBlock->m_numVars : m_firstLazyFunction;
    for (size_t i = 0; i < varStack.size(); ++i) {
        const Identifier& ident = *varStack[i].first;
        if (!functionBody->captures(ident))
            addVar(ident, varStack[i].second & DeclarationStacks::IsConstant);
    }

    if (shouldCaptureAllTheThings)
        m_symbolTable->setCaptureEnd(codeBlock->m_numVars);

    FunctionParameters& parameters = *functionBody->parameters();
    m_parameters.grow(parameters.size() + 1); // reserve space for "this"

    // Add "this" as a parameter
    int nextParameterIndex = CallFrame::thisArgumentOffset();
    m_thisRegister.setIndex(nextParameterIndex--);
    m_codeBlock->addParameter();
    
    for (size_t i = 0; i < parameters.size(); ++i, --nextParameterIndex) {
        int index = nextParameterIndex;
        if (capturedArguments.size() && capturedArguments[i]) {
            ASSERT((functionBody->hasCapturedVariables() && functionBody->captures(parameters[i])) || shouldCaptureAllTheThings);
            index = capturedArguments[i]->index();
            RegisterID original(nextParameterIndex);
            emitMove(capturedArguments[i], &original);
        }
        addParameter(parameters[i], index);
    }
    preserveLastVar();

    // We declare the callee's name last because it should lose to a var, function, and/or parameter declaration.
    addCallee(functionBody, calleeRegister);

    if (isConstructor()) {
        prependComment("'this' because we are a Constructor function");

        RefPtr<RegisterID> func = newTemporary(); 

        UnlinkedValueProfile profile = emitProfiledOpcode(op_get_callee);
        instructions().append(func->index());
        instructions().append(profile);

        emitOpcode(op_create_this); 
        instructions().append(m_thisRegister.index()); 
        instructions().append(func->index()); 
    } else if (!codeBlock->isStrictMode() && (functionBody->usesThis() || codeBlock->usesEval() || m_shouldEmitDebugHooks)) {
        UnlinkedValueProfile profile = emitProfiledOpcode(op_convert_this);
        instructions().append(m_thisRegister.index());
        instructions().append(profile);
    }
}

BytecodeGenerator::BytecodeGenerator(JSGlobalData& globalData, EvalNode* evalNode, UnlinkedEvalCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
    : m_shouldEmitDebugHooks(debuggerMode == DebuggerOn)
    , m_shouldEmitProfileHooks(profilerMode == ProfilerOn)
    , m_symbolTable(codeBlock->symbolTable())
#if ENABLE(BYTECODE_COMMENTS)
    , m_currentCommentString(0)
#endif
    , m_scopeNode(evalNode)
    , m_codeBlock(globalData, codeBlock)
    , m_thisRegister(CallFrame::thisArgumentOffset())
    , m_emptyValueRegister(0)
    , m_finallyDepth(0)
    , m_dynamicScopeDepth(0)
    , m_codeType(EvalCode)
    , m_nextConstantOffset(0)
    , m_globalConstantIndex(0)
    , m_hasCreatedActivation(true)
    , m_firstLazyFunction(0)
    , m_lastLazyFunction(0)
    , m_globalData(&globalData)
    , m_lastOpcodeID(op_end)
#ifndef NDEBUG
    , m_lastOpcodePosition(0)
#endif
    , m_stack(wtfThreadData().stack())
    , m_usesExceptions(false)
    , m_expressionTooDeep(false)
{
    m_codeBlock->setNeedsFullScopeChain(true);

    m_symbolTable->setUsesNonStrictEval(codeBlock->usesEval() && !codeBlock->isStrictMode());
    m_codeBlock->setNumParameters(1);

    prependComment("entering Eval block");
    emitOpcode(op_enter);

    const DeclarationStacks::FunctionStack& functionStack = evalNode->functionStack();
    for (size_t i = 0; i < functionStack.size(); ++i)
        m_codeBlock->addFunctionDecl(makeFunction(functionStack[i]));

    const DeclarationStacks::VarStack& varStack = evalNode->varStack();
    unsigned numVariables = varStack.size();
    Vector<Identifier> variables;
    variables.reserveCapacity(numVariables);
    for (size_t i = 0; i < numVariables; ++i)
        variables.append(*varStack[i].first);
    codeBlock->adoptVariables(variables);
    preserveLastVar();
}

BytecodeGenerator::~BytecodeGenerator()
{
}

RegisterID* BytecodeGenerator::emitInitLazyRegister(RegisterID* reg)
{
    emitOpcode(op_init_lazy_reg);
    instructions().append(reg->index());
    return reg;
}

RegisterID* BytecodeGenerator::resolveCallee(FunctionBodyNode* functionBodyNode)
{
    if (functionBodyNode->ident().isNull() || !functionBodyNode->functionNameIsInScope())
        return 0;

    m_calleeRegister.setIndex(JSStack::Callee);

    // If non-strict eval is in play, we use a separate object in the scope chain for the callee's name.
    if ((m_codeBlock->usesEval() && !m_codeBlock->isStrictMode()) || m_shouldEmitDebugHooks) {
        emitOpcode(op_push_name_scope);
        instructions().append(addConstant(functionBodyNode->ident()));
        instructions().append(m_calleeRegister.index());
        instructions().append(ReadOnly | DontDelete);
        return 0;
    }

    if (!functionBodyNode->captures(functionBodyNode->ident()))
        return &m_calleeRegister;

    // Move the callee into the captured section of the stack.
    return emitMove(addVar(), &m_calleeRegister);
}

void BytecodeGenerator::addCallee(FunctionBodyNode* functionBodyNode, RegisterID* calleeRegister)
{
    if (functionBodyNode->ident().isNull() || !functionBodyNode->functionNameIsInScope())
        return;

    // If non-strict eval is in play, we use a separate object in the scope chain for the callee's name.
    if ((m_codeBlock->usesEval() && !m_codeBlock->isStrictMode()) || m_shouldEmitDebugHooks)
        return;

    ASSERT(calleeRegister);
    symbolTable().add(functionBodyNode->ident().impl(), SymbolTableEntry(calleeRegister->index(), ReadOnly));
}

void BytecodeGenerator::addParameter(const Identifier& ident, int parameterIndex)
{
    // Parameters overwrite var declarations, but not function declarations.
    StringImpl* rep = ident.impl();
    if (!m_functions.contains(rep)) {
        symbolTable().set(rep, parameterIndex);
        RegisterID& parameter = registerFor(parameterIndex);
        parameter.setIndex(parameterIndex);
    }

    // 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_codeBlock->addParameter();
}

bool BytecodeGenerator::willResolveToArguments(const Identifier& ident)
{
    if (ident != propertyNames().arguments)
        return false;
    
    if (!shouldOptimizeLocals())
        return false;
    
    SymbolTableEntry entry = symbolTable().get(ident.impl());
    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.impl());
    ASSERT(!entry.isNull());
    return &registerFor(entry.getIndex());
}

RegisterID* BytecodeGenerator::createLazyRegisterIfNecessary(RegisterID* reg)
{
    if (m_lastLazyFunction <= reg->index() || reg->index() < m_firstLazyFunction)
        return reg;
    emitLazyNewFunction(reg, m_lazyFunctions.get(reg->index()));
    return reg;
}

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;
}

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(this);
    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)
{
#ifndef NDEBUG
    size_t opcodePosition = instructions().size();
    ASSERT(opcodePosition - m_lastOpcodePosition == opcodeLength(m_lastOpcodeID) || m_lastOpcodeID == op_end);
    m_lastOpcodePosition = opcodePosition;
#endif
    emitComment();
    instructions().append(opcodeID);
    m_lastOpcodeID = opcodeID;
}

#if ENABLE(BYTECODE_COMMENTS)
// Record a comment in the CodeBlock's comments list for the current opcode
// that is about to be emitted.
void BytecodeGenerator::emitComment()
{
    if (m_currentCommentString) {
        size_t opcodePosition = instructions().size();
        Comment comment = { opcodePosition, m_currentCommentString };
        m_codeBlock->bytecodeComments().append(comment);
        m_currentCommentString = 0;
    }
}

// Register a comment to be associated with the next opcode that will be emitted.
void BytecodeGenerator::prependComment(const char* string)
{
    m_currentCommentString = string;
}
#endif

UnlinkedArrayProfile BytecodeGenerator::newArrayProfile()
{
#if ENABLE(VALUE_PROFILER)
    return m_codeBlock->addArrayProfile();
#else
    return 0;
#endif
}

UnlinkedArrayAllocationProfile BytecodeGenerator::newArrayAllocationProfile()
{
#if ENABLE(VALUE_PROFILER)
    return m_codeBlock->addArrayAllocationProfile();
#else
    return 0;
#endif
}

UnlinkedValueProfile BytecodeGenerator::emitProfiledOpcode(OpcodeID opcodeID)
{
#if ENABLE(VALUE_PROFILER)
    UnlinkedValueProfile result = m_codeBlock->addValueProfile();
#else
    UnlinkedValueProfile result = 0;
#endif
    emitOpcode(opcodeID);
    return result;
}

void BytecodeGenerator::emitLoopHint()
{
#if ENABLE(DFG_JIT)
    emitOpcode(op_loop_hint);
#endif
}

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);
    m_lastOpcodeID = op_end;
}

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

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

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

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

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

            size_t begin = instructions().size();
            emitOpcode(target->isForward() ? op_jless : op_loop_if_less);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, 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();

            size_t begin = instructions().size();
            emitOpcode(target->isForward() ? op_jlesseq : op_loop_if_lesseq);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_greater) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

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

            size_t begin = instructions().size();
            emitOpcode(target->isForward() ? op_jgreater : op_loop_if_greater);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_greatereq) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

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

            size_t begin = instructions().size();
            emitOpcode(target->isForward() ? op_jgreatereq : op_loop_if_greatereq);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, 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();

            size_t begin = instructions().size();
            emitOpcode(op_jeq_null);
            instructions().append(srcIndex);
            instructions().append(target->bind(begin, 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();

            size_t begin = instructions().size();
            emitOpcode(op_jneq_null);
            instructions().append(srcIndex);
            instructions().append(target->bind(begin, instructions().size()));
            return target;
        }
    }

    size_t begin = instructions().size();

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

PassRefPtr<Label> BytecodeGenerator::emitJumpIfFalse(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();

            size_t begin = instructions().size();
            emitOpcode(op_jnless);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, 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();

            size_t begin = instructions().size();
            emitOpcode(op_jnlesseq);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_greater && target->isForward()) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

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

            size_t begin = instructions().size();
            emitOpcode(op_jngreater);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, instructions().size()));
            return target;
        }
    } else if (m_lastOpcodeID == op_greatereq && target->isForward()) {
        int dstIndex;
        int src1Index;
        int src2Index;

        retrieveLastBinaryOp(dstIndex, src1Index, src2Index);

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

            size_t begin = instructions().size();
            emitOpcode(op_jngreatereq);
            instructions().append(src1Index);
            instructions().append(src2Index);
            instructions().append(target->bind(begin, 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();

            size_t begin = instructions().size();
            emitOpcode(target->isForward() ? op_jtrue : op_loop_if_true);
            instructions().append(srcIndex);
            instructions().append(target->bind(begin, 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();

            size_t begin = instructions().size();
            emitOpcode(op_jneq_null);
            instructions().append(srcIndex);
            instructions().append(target->bind(begin, 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();

            size_t begin = instructions().size();
            emitOpcode(op_jeq_null);
            instructions().append(srcIndex);
            instructions().append(target->bind(begin, instructions().size()));
            return target;
        }
    }

    size_t begin = instructions().size();
    emitOpcode(target->isForward() ? op_jfalse : op_loop_if_false);
    instructions().append(cond->index());
    instructions().append(target->bind(begin, instructions().size()));
    return target;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpIfNotFunctionCall(RegisterID* cond, Label* target)
{
    size_t begin = instructions().size();

    emitOpcode(op_jneq_ptr);
    instructions().append(cond->index());
    instructions().append(Special::CallFunction);
    instructions().append(target->bind(begin, instructions().size()));
    return target;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpIfNotFunctionApply(RegisterID* cond, Label* target)
{
    size_t begin = instructions().size();

    emitOpcode(op_jneq_ptr);
    instructions().append(cond->index());
    instructions().append(Special::ApplyFunction);
    instructions().append(target->bind(begin, instructions().size()));
    return target;
}

unsigned BytecodeGenerator::addConstant(const Identifier& ident)
{
    StringImpl* rep = ident.impl();
    IdentifierMap::AddResult result = m_identifierMap.add(rep, m_codeBlock->numberOfIdentifiers());
    if (result.isNewEntry)
        m_codeBlock->addIdentifier(Identifier(m_globalData, rep));

    return result.iterator->value;
}

// We can't hash JSValue(), so we use a dedicated data member to cache it.
RegisterID* BytecodeGenerator::addConstantEmptyValue()
{
    if (!m_emptyValueRegister) {
        int index = m_nextConstantOffset;
        m_constantPoolRegisters.append(FirstConstantRegisterIndex + m_nextConstantOffset);
        ++m_nextConstantOffset;
        m_codeBlock->addConstant(JSValue());
        m_emptyValueRegister = &m_constantPoolRegisters[index];
    }

    return m_emptyValueRegister;
}

RegisterID* BytecodeGenerator::addConstantValue(JSValue v)
{
    if (!v)
        return addConstantEmptyValue();

    int index = m_nextConstantOffset;
    JSValueMap::AddResult result = m_jsValueMap.add(JSValue::encode(v), m_nextConstantOffset);
    if (result.isNewEntry) {
        m_constantPoolRegisters.append(FirstConstantRegisterIndex + m_nextConstantOffset);
        ++m_nextConstantOffset;
        m_codeBlock->addConstant(v);
    } else
        index = result.iterator->value;
    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()).get().isString()) {
            const String& value = asString(m_codeBlock->constantRegister(src2->index()).get())->tryGetValue();
            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 JSValue each time.
    // Later we can do the extra work to handle that like the other cases.  They also don't
    // work correctly with NaN as a key.
    if (isnan(number) || number == HashTraits<double>::emptyValue() || HashTraits<double>::isDeletedValue(number))
        return emitLoad(dst, jsNumber(number));
    JSValue& valueInMap = m_numberMap.add(number, JSValue()).iterator->value;
    if (!valueInMap)
        valueInMap = jsNumber(number);
    return emitLoad(dst, valueInMap);
}

RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, const Identifier& identifier)
{
    JSString*& stringInMap = m_stringMap.add(identifier.impl(), 0).iterator->value;
    if (!stringInMap)
        stringInMap = jsOwnedString(globalData(), identifier.string());
    return emitLoad(dst, JSValue(stringInMap));
}

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

ResolveResult BytecodeGenerator::resolve(const Identifier& property)
{
    if (property == propertyNames().thisIdentifier)
        return ResolveResult::registerResolve(thisRegister(), ResolveResult::ReadOnlyFlag);

    // Check if the property should be allocated in a register.
    if (m_codeType != GlobalCode && shouldOptimizeLocals() && m_symbolTable) {
        SymbolTableEntry entry = symbolTable().get(property.impl());
        if (!entry.isNull()) {
            if (property == propertyNames().arguments)
                createArgumentsIfNecessary();
            unsigned flags = entry.isReadOnly() ? ResolveResult::ReadOnlyFlag : 0;
            RegisterID* local = createLazyRegisterIfNecessary(&registerFor(entry.getIndex()));
            return ResolveResult::registerResolve(local, flags);
        }
    }
    return ResolveResult::dynamicResolve();
}

ResolveResult BytecodeGenerator::resolveConstDecl(const Identifier& property)
{
    // Register-allocated const declarations.
    if (m_codeType != EvalCode && m_codeType != GlobalCode && m_symbolTable) {
        SymbolTableEntry entry = symbolTable().get(property.impl());
        if (!entry.isNull()) {
            unsigned flags = entry.isReadOnly() ? ResolveResult::ReadOnlyFlag : 0;
            RegisterID* local = createLazyRegisterIfNecessary(&registerFor(entry.getIndex()));
            return ResolveResult::registerResolve(local, flags);
        }
    }

    return ResolveResult::dynamicResolve();
}

void BytecodeGenerator::emitCheckHasInstance(RegisterID* dst, RegisterID* value, RegisterID* base, Label* target)
{
    size_t begin = instructions().size();
    emitOpcode(op_check_has_instance);
    instructions().append(dst->index());
    instructions().append(value->index());
    instructions().append(base->index());
    instructions().append(target->bind(begin, instructions().size()));
}

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

bool BytecodeGenerator::shouldAvoidResolveGlobal()
{
    return !m_labelScopes.size();
}

RegisterID* BytecodeGenerator::emitResolve(RegisterID* dst, const ResolveResult& resolveResult, const Identifier& property)
{

    if (resolveResult.isRegister())
        return emitGetLocalVar(dst, resolveResult, property);

    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve);
    instructions().append(dst->index());
    instructions().append(addConstant(property));
    instructions().append(getResolveOperations(property));
    instructions().append(profile);
    return dst;
}

RegisterID* BytecodeGenerator::emitResolveBase(RegisterID* dst, const ResolveResult& resolveResult, const Identifier& property)
{
    ASSERT_UNUSED(resolveResult, !resolveResult.isRegister());
    // We can't optimise at all :-(
    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_base);
    instructions().append(dst->index());
    instructions().append(addConstant(property));
    instructions().append(false);
    instructions().append(getResolveBaseOperations(property));
    instructions().append(0);
    instructions().append(profile);
    return dst;
}

RegisterID* BytecodeGenerator::emitResolveBaseForPut(RegisterID* dst, const ResolveResult& resolveResult, const Identifier& property, NonlocalResolveInfo& verifier)
{
    ASSERT_UNUSED(resolveResult, !resolveResult.isRegister());
    // We can't optimise at all :-(
    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_base);
    instructions().append(dst->index());
    instructions().append(addConstant(property));
    instructions().append(m_codeBlock->isStrictMode());
    uint32_t putToBaseIndex = 0;
    instructions().append(getResolveBaseForPutOperations(property, putToBaseIndex));
    verifier.resolved(putToBaseIndex);
    instructions().append(putToBaseIndex);
    instructions().append(profile);
    return dst;
}

RegisterID* BytecodeGenerator::emitResolveWithBaseForPut(RegisterID* baseDst, RegisterID* propDst, const ResolveResult& resolveResult, const Identifier& property, NonlocalResolveInfo& verifier)
{
    ASSERT_UNUSED(resolveResult, !resolveResult.isRegister());
    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_with_base);
    instructions().append(baseDst->index());
    instructions().append(propDst->index());
    instructions().append(addConstant(property));
    uint32_t putToBaseIndex = 0;
    instructions().append(getResolveWithBaseForPutOperations(property, putToBaseIndex));
    verifier.resolved(putToBaseIndex);
    instructions().append(putToBaseIndex);
    instructions().append(profile);
    return baseDst;
}

RegisterID* BytecodeGenerator::emitResolveWithThis(RegisterID* baseDst, RegisterID* propDst, const ResolveResult& resolveResult, const Identifier& property)
{
    if (resolveResult.isRegister()) {
        emitLoad(baseDst, jsUndefined());
        emitGetLocalVar(propDst, resolveResult, property);
        return baseDst;
    }

    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_with_this);
    instructions().append(baseDst->index());
    instructions().append(propDst->index());
    instructions().append(addConstant(property));
    instructions().append(getResolveWithThisOperations(property));
    instructions().append(profile);
    return baseDst;
}

RegisterID* BytecodeGenerator::emitGetLocalVar(RegisterID* dst, const ResolveResult& resolveResult, const Identifier&)
{
    switch (resolveResult.type()) {
    case ResolveResult::Register:
    case ResolveResult::ReadOnlyRegister:
        if (dst == ignoredResult())
            return 0;
        return moveToDestinationIfNeeded(dst, resolveResult.local());

    default:
        ASSERT_NOT_REACHED();
        return 0;
    }
}

RegisterID* BytecodeGenerator::emitInitGlobalConst(const Identifier& identifier, RegisterID* value)
{
    ASSERT(m_codeType == GlobalCode);
    emitOpcode(op_init_global_const_nop);
    instructions().append(0);
    instructions().append(value->index());
    instructions().append(0);
    instructions().append(addConstant(identifier));
    return value;
}

RegisterID* BytecodeGenerator::emitGetById(RegisterID* dst, RegisterID* base, const Identifier& property)
{
    m_codeBlock->addPropertyAccessInstruction(instructions().size());

    UnlinkedValueProfile profile = emitProfiledOpcode(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);
    instructions().append(profile);
    return dst;
}

RegisterID* BytecodeGenerator::emitGetArgumentsLength(RegisterID* dst, RegisterID* base)
{
    emitOpcode(op_get_arguments_length);
    instructions().append(dst->index());
    ASSERT(base->index() == m_codeBlock->argumentsRegister());
    instructions().append(base->index());
    instructions().append(addConstant(propertyNames().length));
    return dst;
}

RegisterID* BytecodeGenerator::emitPutById(RegisterID* base, const Identifier& property, RegisterID* value)
{
    m_codeBlock->addPropertyAccessInstruction(instructions().size());

    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);
    instructions().append(0);
    return value;
}

RegisterID* BytecodeGenerator::emitPutToBase(RegisterID* base, const Identifier& property, RegisterID* value, NonlocalResolveInfo& resolveInfo)
{
    emitOpcode(op_put_to_base);
    instructions().append(base->index());
    instructions().append(addConstant(property));
    instructions().append(value->index());
    instructions().append(resolveInfo.put());
    return value;
}

RegisterID* BytecodeGenerator::emitDirectPutById(RegisterID* base, const Identifier& property, RegisterID* value)
{
    m_codeBlock->addPropertyAccessInstruction(instructions().size());
    
    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);
    instructions().append(
        property != m_globalData->propertyNames->underscoreProto
        && PropertyName(property).asIndex() == PropertyName::NotAnIndex);
    return value;
}

void BytecodeGenerator::emitPutGetterSetter(RegisterID* base, const Identifier& property, RegisterID* getter, RegisterID* setter)
{
    emitOpcode(op_put_getter_setter);
    instructions().append(base->index());
    instructions().append(addConstant(property));
    instructions().append(getter->index());
    instructions().append(setter->index());
}

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::emitGetArgumentByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    UnlinkedArrayProfile arrayProfile = newArrayProfile();
    UnlinkedValueProfile profile = emitProfiledOpcode(op_get_argument_by_val);
    instructions().append(dst->index());
    ASSERT(base->index() == m_codeBlock->argumentsRegister());
    instructions().append(base->index());
    instructions().append(property->index());
    instructions().append(arrayProfile);
    instructions().append(profile);
    return dst;
}

RegisterID* BytecodeGenerator::emitGetByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    for (size_t i = m_forInContextStack.size(); i > 0; i--) {
        ForInContext& context = m_forInContextStack[i - 1];
        if (context.propertyRegister == property) {
            emitOpcode(op_get_by_pname);
            instructions().append(dst->index());
            instructions().append(base->index());
            instructions().append(property->index());
            instructions().append(context.expectedSubscriptRegister->index());
            instructions().append(context.iterRegister->index());
            instructions().append(context.indexRegister->index());
            return dst;
        }
    }
    UnlinkedArrayProfile arrayProfile = newArrayProfile();
    UnlinkedValueProfile profile = emitProfiledOpcode(op_get_by_val);
    instructions().append(dst->index());
    instructions().append(base->index());
    instructions().append(property->index());
    instructions().append(arrayProfile);
    instructions().append(profile);
    return dst;
}

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

unsigned BytecodeGenerator::addConstantBuffer(unsigned length)
{
    return m_codeBlock->addConstantBuffer(length);
}

JSString* BytecodeGenerator::addStringConstant(const Identifier& identifier)
{
    JSString*& stringInMap = m_stringMap.add(identifier.impl(), 0).iterator->value;
    if (!stringInMap) {
        stringInMap = jsString(globalData(), identifier.string());
        addConstantValue(stringInMap);
    }
    return stringInMap;
}

RegisterID* BytecodeGenerator::emitNewArray(RegisterID* dst, ElementNode* elements, unsigned length)
{
#if !ASSERT_DISABLED
    unsigned checkLength = 0;
#endif
    bool hadVariableExpression = false;
    if (length) {
        for (ElementNode* n = elements; n; n = n->next()) {
            if (!n->value()->isNumber() && !n->value()->isString()) {
                hadVariableExpression = true;
                break;
            }
            if (n->elision())
                break;
#if !ASSERT_DISABLED
            checkLength++;
#endif
        }
        if (!hadVariableExpression) {
            ASSERT(length == checkLength);
            unsigned constantBufferIndex = addConstantBuffer(length);
            JSValue* constantBuffer = m_codeBlock->constantBuffer(constantBufferIndex).data();
            unsigned index = 0;
            for (ElementNode* n = elements; index < length; n = n->next()) {
                if (n->value()->isNumber())
                    constantBuffer[index++] = jsNumber(static_cast<NumberNode*>(n->value())->value());
                else {
                    ASSERT(n->value()->isString());
                    constantBuffer[index++] = addStringConstant(static_cast<StringNode*>(n->value())->value());
                }
            }
            emitOpcode(op_new_array_buffer);
            instructions().append(dst->index());
            instructions().append(constantBufferIndex);
            instructions().append(length);
            instructions().append(newArrayAllocationProfile());
            return dst;
        }
    }

    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
    instructions().append(newArrayAllocationProfile());
    return dst;
}

RegisterID* BytecodeGenerator::emitNewFunction(RegisterID* dst, FunctionBodyNode* function)
{
    return emitNewFunctionInternal(dst, m_codeBlock->addFunctionDecl(makeFunction(function)), false);
}

RegisterID* BytecodeGenerator::emitLazyNewFunction(RegisterID* dst, FunctionBodyNode* function)
{
    FunctionOffsetMap::AddResult ptr = m_functionOffsets.add(function, 0);
    if (ptr.isNewEntry)
        ptr.iterator->value = m_codeBlock->addFunctionDecl(makeFunction(function));
    return emitNewFunctionInternal(dst, ptr.iterator->value, true);
}

RegisterID* BytecodeGenerator::emitNewFunctionInternal(RegisterID* dst, unsigned index, bool doNullCheck)
{
    createActivationIfNecessary();
    emitOpcode(op_new_func);
    instructions().append(dst->index());
    instructions().append(index);
    instructions().append(doNullCheck);
    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)
{
    FunctionBodyNode* function = n->body();
    unsigned index = m_codeBlock->addFunctionExpr(makeFunction(function));
    
    createActivationIfNecessary();
    emitOpcode(op_new_func_exp);
    instructions().append(r0->index());
    instructions().append(index);
    return r0;
}

RegisterID* BytecodeGenerator::emitCall(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    return emitCall(op_call, dst, func, expectedFunction, callArguments, divot, startOffset, endOffset);
}

void BytecodeGenerator::createArgumentsIfNecessary()
{
    if (m_codeType != FunctionCode)
        return;
    
    if (!m_codeBlock->usesArguments())
        return;

    // If we're in strict mode we tear off the arguments on function
    // entry, so there's no need to check if we need to create them
    // now
    if (m_codeBlock->isStrictMode())
        return;

    emitOpcode(op_create_arguments);
    instructions().append(m_codeBlock->argumentsRegister());
}

void BytecodeGenerator::createActivationIfNecessary()
{
    if (m_hasCreatedActivation)
        return;
    if (!m_codeBlock->needsFullScopeChain())
        return;
    emitOpcode(op_create_activation);
    instructions().append(m_activationRegister->index());
}

RegisterID* BytecodeGenerator::emitCallEval(RegisterID* dst, RegisterID* func, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    return emitCall(op_call_eval, dst, func, NoExpectedFunction, callArguments, divot, startOffset, endOffset);
}

ExpectedFunction BytecodeGenerator::expectedFunctionForIdentifier(const Identifier& identifier)
{
    if (identifier == m_globalData->propertyNames->Object)
        return ExpectObjectConstructor;
    if (identifier == m_globalData->propertyNames->Array)
        return ExpectArrayConstructor;
    return NoExpectedFunction;
}

ExpectedFunction BytecodeGenerator::emitExpectedFunctionSnippet(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, Label* done)
{
    RefPtr<Label> realCall = newLabel();
    switch (expectedFunction) {
    case ExpectObjectConstructor: {
        // If the number of arguments is non-zero, then we can't do anything interesting.
        if (callArguments.argumentCountIncludingThis() >= 2)
            return NoExpectedFunction;
        
        size_t begin = instructions().size();
        emitOpcode(op_jneq_ptr);
        instructions().append(func->index());
        instructions().append(Special::ObjectConstructor);
        instructions().append(realCall->bind(begin, instructions().size()));
        
        if (dst != ignoredResult()) {
            emitOpcode(op_new_object);
            instructions().append(dst->index());
        }
        break;
    }
        
    case ExpectArrayConstructor: {
        // If you're doing anything other than "new Array()" or "new Array(foo)" then we
        // don't do inline it, for now. The only reason is that call arguments are in
        // the opposite order of what op_new_array expects, so we'd either need to change
        // how op_new_array works or we'd need an op_new_array_reverse. Neither of these
        // things sounds like it's worth it.
        if (callArguments.argumentCountIncludingThis() > 2)
            return NoExpectedFunction;
        
        size_t begin = instructions().size();
        emitOpcode(op_jneq_ptr);
        instructions().append(func->index());
        instructions().append(Special::ArrayConstructor);
        instructions().append(realCall->bind(begin, instructions().size()));
        
        if (dst != ignoredResult()) {
            if (callArguments.argumentCountIncludingThis() == 2) {
                emitOpcode(op_new_array_with_size);
                instructions().append(dst->index());
                instructions().append(callArguments.argumentRegister(0)->index());
                instructions().append(newArrayAllocationProfile());
            } else {
                ASSERT(callArguments.argumentCountIncludingThis() == 1);
                emitOpcode(op_new_array);
                instructions().append(dst->index());
                instructions().append(0);
                instructions().append(0);
                instructions().append(newArrayAllocationProfile());
            }
        }
        break;
    }
        
    default:
        ASSERT(expectedFunction == NoExpectedFunction);
        return NoExpectedFunction;
    }
    
    size_t begin = instructions().size();
    emitOpcode(op_jmp);
    instructions().append(done->bind(begin, instructions().size()));
    emitLabel(realCall.get());
    
    return expectedFunction;
}

RegisterID* BytecodeGenerator::emitCall(OpcodeID opcodeID, RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    ASSERT(opcodeID == op_call || opcodeID == op_call_eval);
    ASSERT(func->refCount());

    if (m_shouldEmitProfileHooks)
        emitMove(callArguments.profileHookRegister(), func);

    // Generate code for arguments.
    unsigned argument = 0;
    for (ArgumentListNode* n = callArguments.argumentsNode()->m_listNode; n; n = n->m_next)
        emitNode(callArguments.argumentRegister(argument++), n);

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

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

    emitExpressionInfo(divot, startOffset, endOffset);

    RefPtr<Label> done = newLabel();
    expectedFunction = emitExpectedFunctionSnippet(dst, func, expectedFunction, callArguments, done.get());
    
    // Emit call.
    UnlinkedArrayProfile arrayProfile = newArrayProfile();
    emitOpcode(opcodeID);
    instructions().append(func->index()); // func
    instructions().append(callArguments.argumentCountIncludingThis()); // argCount
    instructions().append(callArguments.registerOffset()); // registerOffset
#if ENABLE(LLINT)
    instructions().append(m_codeBlock->addLLIntCallLinkInfo());
#else
    instructions().append(0);
#endif
    instructions().append(arrayProfile);
    if (dst != ignoredResult()) {
        UnlinkedValueProfile profile = emitProfiledOpcode(op_call_put_result);
        instructions().append(dst->index()); // dst
        instructions().append(profile);
    }
    
    if (expectedFunction != NoExpectedFunction)
        emitLabel(done.get());

    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_did_call);
        instructions().append(callArguments.profileHookRegister()->index());
    }

    return dst;
}

RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, RegisterID* profileHookRegister, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    if (m_shouldEmitProfileHooks) {
        emitMove(profileHookRegister, func);
        emitOpcode(op_profile_will_call);
        instructions().append(profileHookRegister->index());
    }
    
    emitExpressionInfo(divot, startOffset, endOffset);

    // Emit call.
    emitOpcode(op_call_varargs);
    instructions().append(func->index());
    instructions().append(thisRegister->index());
    instructions().append(arguments->index());
    instructions().append(firstFreeRegister->index());
    if (dst != ignoredResult()) {
        UnlinkedValueProfile profile = emitProfiledOpcode(op_call_put_result);
        instructions().append(dst->index());
        instructions().append(profile);
    }
    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_did_call);
        instructions().append(profileHookRegister->index());
    }
    return dst;
}

RegisterID* BytecodeGenerator::emitReturn(RegisterID* src)
{
    if (m_codeBlock->needsFullScopeChain()) {
        emitOpcode(op_tear_off_activation);
        instructions().append(m_activationRegister->index());
    }

    if (m_codeBlock->usesArguments() && m_codeBlock->numParameters() != 1 && !m_codeBlock->isStrictMode()) {
        emitOpcode(op_tear_off_arguments);
        instructions().append(m_codeBlock->argumentsRegister());
        instructions().append(m_activationRegister ? m_activationRegister->index() : emitLoad(0, JSValue())->index());
    }

    // Constructors use op_ret_object_or_this to check the result is an
    // object, unless we can trivially determine the check is not
    // necessary (currently, if the return value is 'this').
    if (isConstructor() && (src->index() != m_thisRegister.index())) {
        emitOpcode(op_ret_object_or_this);
        instructions().append(src->index());
        instructions().append(m_thisRegister.index());
        return src;
    }
    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, ExpectedFunction expectedFunction, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset)
{
    ASSERT(func->refCount());

    if (m_shouldEmitProfileHooks)
        emitMove(callArguments.profileHookRegister(), func);

    // Generate code for arguments.
    unsigned argument = 0;
    if (ArgumentsNode* argumentsNode = callArguments.argumentsNode()) {
        for (ArgumentListNode* n = argumentsNode->m_listNode; n; n = n->m_next)
            emitNode(callArguments.argumentRegister(argument++), n);
    }

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

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

    emitExpressionInfo(divot, startOffset, endOffset);
    
    RefPtr<Label> done = newLabel();
    expectedFunction = emitExpectedFunctionSnippet(dst, func, expectedFunction, callArguments, done.get());

    emitOpcode(op_construct);
    instructions().append(func->index()); // func
    instructions().append(callArguments.argumentCountIncludingThis()); // argCount
    instructions().append(callArguments.registerOffset()); // registerOffset
#if ENABLE(LLINT)
    instructions().append(m_codeBlock->addLLIntCallLinkInfo());
#else
    instructions().append(0);
#endif
    instructions().append(0);
    if (dst != ignoredResult()) {
        UnlinkedValueProfile profile = emitProfiledOpcode(op_call_put_result);
        instructions().append(dst->index()); // dst
        instructions().append(profile);
    }

    if (expectedFunction != NoExpectedFunction)
        emitLabel(done.get());

    if (m_shouldEmitProfileHooks) {
        emitOpcode(op_profile_did_call);
        instructions().append(callArguments.profileHookRegister()->index());
    }

    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::emitPushWithScope(RegisterID* scope)
{
    ControlFlowContext context;
    context.isFinallyBlock = false;
    m_scopeContextStack.append(context);
    m_dynamicScopeDepth++;

    return emitUnaryNoDstOp(op_push_with_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, int column)
{
#if ENABLE(DEBUG_WITH_BREAKPOINT)
    if (debugHookID != DidReachBreakpoint)
        return;
#else
    if (!m_shouldEmitDebugHooks)
        return;
#endif
    emitOpcode(op_debug);
    instructions().append(debugHookID);
    instructions().append(firstLine);
    instructions().append(lastLine);
    instructions().append(column);
}

void BytecodeGenerator::pushFinallyContext(StatementNode* finallyBlock)
{
    ControlFlowContext scope;
    scope.isFinallyBlock = true;
    FinallyContext context = {
        finallyBlock,
        static_cast<unsigned>(m_scopeContextStack.size()),
        static_cast<unsigned>(m_switchContextStack.size()),
        static_cast<unsigned>(m_forInContextStack.size()),
        static_cast<unsigned>(m_tryContextStack.size()),
        static_cast<unsigned>(m_labelScopes.size()),
        m_finallyDepth,
        m_dynamicScopeDepth
    };
    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) {
            size_t begin = instructions().size();

            // 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->bind(begin, 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->bind(begin, instructions().size()));
            emitLabel(nextInsn.get());
        }
        
        Vector<ControlFlowContext> savedScopeContextStack;
        Vector<SwitchInfo> savedSwitchContextStack;
        Vector<ForInContext> savedForInContextStack;
        Vector<TryContext> poppedTryContexts;
        SegmentedVector<LabelScope, 8> savedLabelScopes;
        while (topScope > bottomScope && topScope->isFinallyBlock) {
            RefPtr<Label> beforeFinally = emitLabel(newLabel().get());
            
            // Save the current state of the world while instating the state of the world
            // for the finally block.
            FinallyContext finallyContext = topScope->finallyContext;
            bool flipScopes = finallyContext.scopeContextStackSize != m_scopeContextStack.size();
            bool flipSwitches = finallyContext.switchContextStackSize != m_switchContextStack.size();
            bool flipForIns = finallyContext.forInContextStackSize != m_forInContextStack.size();
            bool flipTries = finallyContext.tryContextStackSize != m_tryContextStack.size();
            bool flipLabelScopes = finallyContext.labelScopesSize != m_labelScopes.size();
            int topScopeIndex = -1;
            int bottomScopeIndex = -1;
            if (flipScopes) {
                topScopeIndex = topScope - m_scopeContextStack.begin();
                bottomScopeIndex = bottomScope - m_scopeContextStack.begin();
                savedScopeContextStack = m_scopeContextStack;
                m_scopeContextStack.shrink(finallyContext.scopeContextStackSize);
            }
            if (flipSwitches) {
                savedSwitchContextStack = m_switchContextStack;
                m_switchContextStack.shrink(finallyContext.switchContextStackSize);
            }
            if (flipForIns) {
                savedForInContextStack = m_forInContextStack;
                m_forInContextStack.shrink(finallyContext.forInContextStackSize);
            }
            if (flipTries) {
                while (m_tryContextStack.size() != finallyContext.tryContextStackSize) {
                    ASSERT(m_tryContextStack.size() > finallyContext.tryContextStackSize);
                    TryContext context = m_tryContextStack.last();
                    m_tryContextStack.removeLast();
                    TryRange range;
                    range.start = context.start;
                    range.end = beforeFinally;
                    range.tryData = context.tryData;
                    m_tryRanges.append(range);
                    poppedTryContexts.append(context);
                }
            }
            if (flipLabelScopes) {
                savedLabelScopes = m_labelScopes;
                while (m_labelScopes.size() > finallyContext.labelScopesSize)
                    m_labelScopes.removeLast();
            }
            int savedFinallyDepth = m_finallyDepth;
            m_finallyDepth = finallyContext.finallyDepth;
            int savedDynamicScopeDepth = m_dynamicScopeDepth;
            m_dynamicScopeDepth = finallyContext.dynamicScopeDepth;
            
            // Emit the finally block.
            emitNode(finallyContext.finallyBlock);
            
            RefPtr<Label> afterFinally = emitLabel(newLabel().get());
            
            // Restore the state of the world.
            if (flipScopes) {
                m_scopeContextStack = savedScopeContextStack;
                topScope = &m_scopeContextStack[topScopeIndex]; // assert it's within bounds
                bottomScope = m_scopeContextStack.begin() + bottomScopeIndex; // don't assert, since it the index might be -1.
            }
            if (flipSwitches)
                m_switchContextStack = savedSwitchContextStack;
            if (flipForIns)
                m_forInContextStack = savedForInContextStack;
            if (flipTries) {
                ASSERT(m_tryContextStack.size() == finallyContext.tryContextStackSize);
                for (unsigned i = poppedTryContexts.size(); i--;) {
                    TryContext context = poppedTryContexts[i];
                    context.start = afterFinally;
                    m_tryContextStack.append(context);
                }
                poppedTryContexts.clear();
            }
            if (flipLabelScopes)
                m_labelScopes = savedLabelScopes;
            m_finallyDepth = savedFinallyDepth;
            m_dynamicScopeDepth = savedDynamicScopeDepth;
            
            --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);

    size_t begin = instructions().size();

    emitOpcode(op_jmp_scopes);
    instructions().append(scopeDelta);
    instructions().append(target->bind(begin, instructions().size()));
    return target;
}

RegisterID* BytecodeGenerator::emitGetPropertyNames(RegisterID* dst, RegisterID* base, RegisterID* i, RegisterID* size, Label* breakTarget)
{
    size_t begin = instructions().size();

    emitOpcode(op_get_pnames);
    instructions().append(dst->index());
    instructions().append(base->index());
    instructions().append(i->index());
    instructions().append(size->index());
    instructions().append(breakTarget->bind(begin, instructions().size()));
    return dst;
}

RegisterID* BytecodeGenerator::emitNextPropertyName(RegisterID* dst, RegisterID* base, RegisterID* i, RegisterID* size, RegisterID* iter, Label* target)
{
    size_t begin = instructions().size();

    emitOpcode(op_next_pname);
    instructions().append(dst->index());
    instructions().append(base->index());
    instructions().append(i->index());
    instructions().append(size->index());
    instructions().append(iter->index());
    instructions().append(target->bind(begin, instructions().size()));
    return dst;
}

TryData* BytecodeGenerator::pushTry(Label* start)
{
    TryData tryData;
    tryData.target = newLabel();
    tryData.targetScopeDepth = UINT_MAX;
    m_tryData.append(tryData);
    TryData* result = &m_tryData.last();
    
    TryContext tryContext;
    tryContext.start = start;
    tryContext.tryData = result;
    
    m_tryContextStack.append(tryContext);
    
    return result;
}

RegisterID* BytecodeGenerator::popTryAndEmitCatch(TryData* tryData, RegisterID* targetRegister, Label* end)
{
    m_usesExceptions = true;
    
    ASSERT_UNUSED(tryData, m_tryContextStack.last().tryData == tryData);
    
    TryRange tryRange;
    tryRange.start = m_tryContextStack.last().start;
    tryRange.end = end;
    tryRange.tryData = m_tryContextStack.last().tryData;
    m_tryRanges.append(tryRange);
    m_tryContextStack.removeLast();
    
    emitLabel(tryRange.tryData->target.get());
    tryRange.tryData->targetScopeDepth = m_dynamicScopeDepth;

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

void BytecodeGenerator::emitThrowReferenceError(const String& message)
{
    emitOpcode(op_throw_static_error);
    instructions().append(addConstantValue(jsString(globalData(), message))->index());
    instructions().append(true);
}

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

    emitOpcode(op_push_name_scope);
    instructions().append(addConstant(property));
    instructions().append(value->index());
    instructions().append(attributes);
}

void BytecodeGenerator::beginSwitch(RegisterID* scrutineeRegister, SwitchInfo::SwitchType type)
{
    SwitchInfo info = { static_cast<uint32_t>(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(UnlinkedSimpleJumpTable& 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]->bind(switchAddress, switchAddress + 3)); 
    }
}

static int32_t keyForCharacterSwitch(ExpressionNode* node, int32_t min, int32_t max)
{
    UNUSED_PARAM(max);
    ASSERT(node->isString());
    StringImpl* clause = static_cast<StringNode*>(node)->value().impl();
    ASSERT(clause->length() == 1);
    
    int32_t key = (*clause)[0];
    ASSERT(key >= min);
    ASSERT(key <= max);
    return key - min;
}

static void prepareJumpTableForCharacterSwitch(UnlinkedSimpleJumpTable& 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]->bind(switchAddress, switchAddress + 3)); 
    }
}

static void prepareJumpTableForStringSwitch(UnlinkedStringJumpTable& 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());
        StringImpl* clause = static_cast<StringNode*>(nodes[i])->value().impl();
        jumpTable.offsetTable.add(clause, labels[i]->bind(switchAddress, switchAddress + 3));
    }
}

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->bind(switchInfo.bytecodeOffset, switchInfo.bytecodeOffset + 3);

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

        UnlinkedStringJumpTable& jumpTable = m_codeBlock->addStringSwitchJumpTable();
        prepareJumpTableForStringSwitch(jumpTable, switchInfo.bytecodeOffset, 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.
    m_expressionTooDeep = true;
    return newTemporary();
}

void BytecodeGenerator::setIsNumericCompareFunction(bool isNumericCompareFunction)
{
    m_codeBlock->setIsNumericCompareFunction(isNumericCompareFunction);
}

bool BytecodeGenerator::isArgumentNumber(const Identifier& ident, int argumentNumber)
{
    RegisterID* registerID = resolve(ident).local();
    if (!registerID || registerID->index() >= 0)
         return 0;
    return registerID->index() == CallFrame::argumentOffset(argumentNumber);
}

void BytecodeGenerator::emitReadOnlyExceptionIfNeeded()
{
    if (!isStrictMode())
        return;
    emitOpcode(op_throw_static_error);
    instructions().append(addConstantValue(jsString(globalData(), GetStrictModeReadonlyPropertyWriteError()))->index());
    instructions().append(false);
}

} // namespace JSC