BytecodeGenerator.cpp

/*
 * Copyright (C) 2008-2023 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 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 "AbstractModuleRecord.h"
#include "BuiltinExecutables.h"
#include "BuiltinNames.h"
#include "BytecodeGeneratorBaseInlines.h"
#include "BytecodeGeneratorification.h"
#include "BytecodeUseDef.h"
#include "DefinePropertyAttributes.h"
#include "Interpreter.h"
#include "JSAsyncGenerator.h"
#include "JSBigInt.h"
#include "JSCInlines.h"
#include "JSCellButterfly.h"
#include "JSTemplateObjectDescriptor.h"
#include "Options.h"
#include "PrivateFieldPutKind.h"
#include "StrongInlines.h"
#include "SuperSampler.h"
#include "SymbolTableInlines.h"
#include "TopExceptionScope.h"
#include "UnlinkedCodeBlock.h"
#include "UnlinkedEvalCodeBlock.h"
#include "UnlinkedFunctionCodeBlock.h"
#include "UnlinkedMetadataTableInlines.h"
#include "UnlinkedModuleProgramCodeBlock.h"
#include "UnlinkedProgramCodeBlock.h"
#include "VMTrapsInlines.h"
#include "VariableEnvironmentInlines.h"
#include <wtf/BitVector.h>
#include <wtf/HashSet.h>
#include <wtf/StdLibExtras.h>
#include <wtf/TZoneMallocInlines.h>
#include <wtf/text/WTFString.h>

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

namespace JSC {

WTF_MAKE_TZONE_ALLOCATED_IMPL(BytecodeGenerator);
WTF_MAKE_TZONE_ALLOCATED_IMPL(ForInContext);

template<typename CallOp>
struct VarArgsOp;

template<>
struct VarArgsOp<OpCall> {
    using type = OpCallVarargs;
};

template<>
struct VarArgsOp<OpCallIgnoreResult> {
    using type = OpCallVarargs;
};

template<>
struct VarArgsOp<OpCallDirectEval> {
    using type = OpCallVarargs;
};

template<>
struct VarArgsOp<OpTailCall> {
    using type = OpTailCallVarargs;
};

template<>
struct VarArgsOp<OpConstruct> {
    using type = OpConstructVarargs;
};

template<>
struct VarArgsOp<OpSuperConstruct> {
    using type = OpSuperConstructVarargs;
};

template<>
void GenericLabel<JSGeneratorTraits>::setLocation(BytecodeGenerator& generator, unsigned location)
{
    m_location = location;
    
    for (auto offset : m_unresolvedJumps) {
        auto instruction = generator.m_writer.ref(offset);
        int target = m_location - offset;

#define CASE(__op) \
    case __op::opcodeID:  \
        instruction->cast<__op>()->setTargetLabel(BoundLabel(target), [&]() { \
            generator.m_codeBlock->addOutOfLineJumpTarget(instruction.offset(), target); \
            return BoundLabel(); \
        }); \
        break;

        switch (instruction->opcodeID()) {
        CASE(OpJmp)
        CASE(OpJtrue)
        CASE(OpJfalse)
        CASE(OpJeqNull)
        CASE(OpJneqNull)
        CASE(OpJundefinedOrNull)
        CASE(OpJnundefinedOrNull)
        CASE(OpJeq)
        CASE(OpJstricteq)
        CASE(OpJneq)
        CASE(OpJeqPtr)
        CASE(OpJneqPtr)
        CASE(OpJnstricteq)
        CASE(OpJless)
        CASE(OpJlesseq)
        CASE(OpJgreater)
        CASE(OpJgreatereq)
        CASE(OpJnless)
        CASE(OpJnlesseq)
        CASE(OpJngreater)
        CASE(OpJngreatereq)
        CASE(OpJbelow)
        CASE(OpJbeloweq)
        default:
            ASSERT_NOT_REACHED();
        }
#undef CASE
    }
}

void Variable::dump(PrintStream& out) const
{
    out.print(
        "{ident = ", m_ident,
        ", offset = ", m_offset,
        ", local = ", RawPointer(m_local),
        ", attributes = ", m_attributes,
        ", kind = ", m_kind,
        ", symbolTableConstantIndex = ", m_symbolTableConstantIndex,
        ", isLexicallyScoped = ", m_isLexicallyScoped, "}");
}

FinallyContext::FinallyContext(BytecodeGenerator& generator, Label& finallyLabel)
    : m_outerContext(generator.m_currentFinallyContext)
    , m_finallyLabel(&finallyLabel)
{
    ASSERT(m_jumps.isEmpty());
    m_completionRecord.typeRegister = generator.newTemporary();
    m_completionRecord.valueRegister = generator.newTemporary();
    generator.emitLoad(completionTypeRegister(), CompletionType::Normal);
    generator.moveEmptyValue(completionValueRegister());
}

template<typename EmitBytecodeFunctor>
void BytecodeGenerator::asyncFuncParametersTryCatchWrap(const EmitBytecodeFunctor& emitBytecode)
{
    TryData* tryData = nullptr;
    if (m_asyncFuncParametersTryCatchInfo) {
        AsyncFuncParametersTryCatchInfo& info = m_asyncFuncParametersTryCatchInfo.value();
        ASSERT(info.catchStartLabel && info.thrownValue);
        Ref<Label> tryStartLabel = newEmittedLabel();
        tryData = pushTry(tryStartLabel.get(), *info.catchStartLabel.get(), HandlerType::SynthesizedCatch);
    }

    emitBytecode();

    if (m_asyncFuncParametersTryCatchInfo) {
        AsyncFuncParametersTryCatchInfo& info = m_asyncFuncParametersTryCatchInfo.value();
        Ref<Label> tryEndLabel = newEmittedLabel();
        popTry(tryData, tryEndLabel.get());

        emitOutOfLineCatchHandler(info.thrownValue.get(), nullptr, tryData);
    }
}

ParserError BytecodeGenerator::generate(unsigned& size)
{
    if (m_outOfMemoryDuringConstruction) [[unlikely]]
        return ParserError(ParserError::OutOfMemory);

    bool callingNonCallableConstructor = false;
    switch (constructorKind()) {
    case ConstructorKind::None:
        break;
    case ConstructorKind::Naked:
    case ConstructorKind::Base:
    case ConstructorKind::Extends:
        callingNonCallableConstructor = !isConstructor();
        break;
    }

    m_codeBlock->setThisRegister(m_thisRegister.virtualRegister());

    emitLogShadowChickenPrologueIfNecessary();
    
    if (!callingNonCallableConstructor) {
        // If we have declared a variable named "arguments" and we are using arguments then we should
        // perform that assignment now.
        if (m_needToInitializeArguments)
            initializeVariable(variable(propertyNames().arguments), m_argumentsRegister);

        {
            bool shouldHoistInEval = m_codeType == EvalCode && !m_ecmaMode.isStrict();
            RefPtr<RegisterID> topLevelScope;
            for (auto functionPair : m_functionsToInitialize) {
                FunctionMetadataNode* metadata = functionPair.first;
                FunctionVariableType functionType = functionPair.second;
                if (functionType == NormalFunctionVariable) {
                    Variable var = variable(metadata->ident());
                    if (RegisterID* local = var.local())
                        emitNewFunction(local, metadata);
                    else {
                        RefPtr<RegisterID> temp = newTemporary();
                        emitNewFunction(temp.get(), metadata);
                        initializeVariable(var, temp.get());
                    }
                } else if (functionType == TopLevelFunctionVariable) {
                    RefPtr<RegisterID> temp = newTemporary();
                    emitNewFunction(temp.get(), metadata);
                    if (!topLevelScope) {
                        // We know this will resolve to the top level scope or global object because our parser/global initialization code 
                        // doesn't allow let/const/class variables to have the same names as functions.
                        // This is a top level function, and it's an error to ever create a top level function
                        // name that would resolve to a lexical variable. E.g:
                        // ```
                        //     function f() {
                        //         {
                        //             let x;
                        //             {
                        //             //// error thrown here
                        //                  eval("function x(){}");
                        //             }
                        //         }
                        //     }
                        // ```
                        // Therefore, we're guaranteed to have this resolve to a top level variable.
                        RefPtr<RegisterID> topLevelObjectScope = shouldHoistInEval
                            ? emitResolveScopeForHoistingFuncDeclInEval(nullptr, metadata->ident())
                            : emitResolveScope(nullptr, Variable(metadata->ident()));

                        topLevelScope = newBlockScopeVariable();
                        move(topLevelScope.get(), topLevelObjectScope.get());
                    }
                    if (shouldHoistInEval)
                        emitPutToScopeDynamic(topLevelScope.get(), metadata->ident(), temp.get(), ThrowIfNotFound, InitializationMode::NotInitialization);
                    else
                        emitPutToScope(topLevelScope.get(), Variable(metadata->ident()), temp.get(), ThrowIfNotFound, InitializationMode::NotInitialization);
                } else
                    RELEASE_ASSERT_NOT_REACHED();
            }
        }
    
        m_scopeNode->emitBytecode(*this);
    } else {
        // At this point we would have emitted an unconditional throw followed by some nonsense that's
        // just an artifact of how this generator is structured. That code never runs, but it confuses
        // bytecode analyses because it constitutes an unterminated basic block. So, we terminate the
        // basic block the strongest way possible.
        emitUnreachable();
    }

    for (auto& handler : m_exceptionHandlersToEmit) {
        Ref<Label> realCatchTarget = newLabel();
        TryData* tryData = handler.tryData;

        OpCatch::emit(this, handler.exceptionRegister, handler.thrownValueRegister);
        realCatchTarget->setLocation(*this, m_lastInstruction.offset());
        if (handler.completionTypeRegister.isValid()) {
            RegisterID completionTypeRegister { handler.completionTypeRegister };
            CompletionType completionType =
                tryData->handlerType == HandlerType::Finally || tryData->handlerType == HandlerType::SynthesizedFinally
                ? CompletionType::Throw
                : CompletionType::Normal;
            emitLoad(&completionTypeRegister, completionType);
        }

        emitJump(tryData->target.get());
        tryData->target = WTF::move(realCatchTarget);
    }

    if (m_asyncFuncParametersTryCatchInfo) {
        AsyncFuncParametersTryCatchInfo& info = m_asyncFuncParametersTryCatchInfo.value();
        ASSERT(info.catchStartLabel && info.thrownValue);
        emitLabel(*info.catchStartLabel.get());
        JSTextPosition divot(m_scopeNode->firstLine(), m_scopeNode->startOffset(), m_scopeNode->lineStartOffset());
        if (promiseRegister()) {
            RefPtr<RegisterID> rejectPromise = moveLinkTimeConstant(nullptr, LinkTimeConstant::rejectPromiseWithFirstResolvingFunctionCallCheck);
            CallArguments args(*this, nullptr, 2);
            emitLoad(args.thisRegister(), jsUndefined());
            move(args.argumentRegister(0), promiseRegister());
            move(args.argumentRegister(1), info.thrownValue.get());
            emitCallIgnoreResult(newTemporary(), rejectPromise.get(), NoExpectedFunction, args, divot, divot, divot, DebuggableCall::No);
            emitReturn(promiseRegister());
        } else {
            // If we are not creating a promise yet, we can just do `return @newRejectedPromise(thrownValue)`.
            RefPtr<RegisterID> newRejectedPromise = moveLinkTimeConstant(nullptr, LinkTimeConstant::newRejectedPromise);
            CallArguments args(*this, nullptr, 1);
            emitLoad(args.thisRegister(), jsUndefined());
            move(args.argumentRegister(0), info.thrownValue.get());
            RefPtr<RegisterID> result = newTemporary();
            emitCall(result.get(), newRejectedPromise.get(), NoExpectedFunction, args, divot, divot, divot, DebuggableCall::No);
            emitReturn(result.get());
        }
    }

    m_staticPropertyAnalyzer.kill();

    for (auto& range : m_tryRanges) {
        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;
        
        UnlinkedHandlerInfo info(static_cast<uint32_t>(start), static_cast<uint32_t>(end),
            static_cast<uint32_t>(range.tryData->target->bind()), range.tryData->handlerType);
        m_codeBlock->addExceptionHandler(info);
    }
    

    if (m_needsGeneratorification)
        performGeneratorification(*this, m_codeBlock.get(), m_writer, m_generatorFrameSymbolTable.get(), m_generatorFrameSymbolTableIndex);

    RELEASE_ASSERT(m_codeBlock->numCalleeLocals() < static_cast<unsigned>(FirstConstantRegisterIndex));
    size = instructions().size();
    m_codeBlock->finalize(m_writer.finalize());

    // We limit total bytecode sequence size to int32_t so that we can use int32_t jump offsets.
    // Also, this allows us to use one bit of bytecode for some flag, including "ignore-result-flag".
    if (size > static_cast<unsigned>(INT32_MAX))
        return ParserError(ParserError::OutOfMemory);

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

BytecodeGenerator::BytecodeGenerator(VM& vm, ProgramNode* programNode, UnlinkedProgramCodeBlock* codeBlock, OptionSet<CodeGenerationMode> codeGenerationMode, const RefPtr<TDZEnvironmentLink>& parentScopeTDZVariables, const FixedVector<Identifier>*, const PrivateNameEnvironment*)
    : BytecodeGeneratorBase(makeUnique<UnlinkedCodeBlockGenerator>(vm, codeBlock), CodeBlock::llintBaselineCalleeSaveSpaceAsVirtualRegisters())
    , m_codeGenerationMode(codeGenerationMode)
    , m_scopeNode(programNode)
    , m_thisRegister(CallFrame::thisArgumentOffset())
    , m_codeType(GlobalCode)
    , m_vm(vm)
    , m_usesExceptions(false)
    , m_expressionTooDeep(false)
    , m_isBuiltinFunction(false)
    , m_usesSloppyEval(false)
    , m_allowTailCallOptimization(false)
    , m_allowCallIgnoreResultOptimization(m_defaultAllowCallIgnoreResultOptimization)
    , m_needsToUpdateArrowFunctionContext(programNode->usesArrowFunction() || programNode->usesEval())
    , m_ecmaMode(ECMAMode::fromBool(programNode->isStrictMode()))
{
    ASSERT_UNUSED(parentScopeTDZVariables, !parentScopeTDZVariables);

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

    emitEnter();

    allocateScope();

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

    for (auto* function : functionStack)
        m_functionsToInitialize.append(std::make_pair(function, TopLevelFunctionVariable));

    if (Options::validateBytecode()) {
        for (auto& entry : programNode->varDeclarations())
            RELEASE_ASSERT(entry.value.isVar());
    }
    codeBlock->setVariableDeclarations(programNode->varDeclarations());
    codeBlock->setLexicalDeclarations(programNode->lexicalVariables());
    // Even though this program may have lexical variables that go under TDZ, when linking the get_from_scope/put_to_scope
    // operations we emit we will have ResolveTypes that implictly do TDZ checks. Therefore, we don't need
    // additional TDZ checks on top of those. This is why we can omit pushing programNode->lexicalVariables()
    // to the TDZ stack.
    
    if (needsToUpdateArrowFunctionContext()) {
        initializeArrowFunctionContextScopeIfNeeded();
        emitPutThisToArrowFunctionContextScope();
    }
}

BytecodeGenerator::BytecodeGenerator(VM& vm, FunctionNode* functionNode, UnlinkedFunctionCodeBlock* codeBlock, OptionSet<CodeGenerationMode> codeGenerationMode, const RefPtr<TDZEnvironmentLink>& parentScopeTDZVariables, const FixedVector<Identifier>* generatorOrAsyncWrapperFunctionParameterNames, const PrivateNameEnvironment* parentPrivateNameEnvironment)
    : BytecodeGeneratorBase(makeUnique<UnlinkedCodeBlockGenerator>(vm, codeBlock), CodeBlock::llintBaselineCalleeSaveSpaceAsVirtualRegisters())
    , m_codeGenerationMode(codeGenerationMode)
    , m_scopeNode(functionNode)
    , m_codeType(FunctionCode)
    , m_vm(vm)
    , m_defaultAllowCallIgnoreResultOptimization(!Options::evalMode())
    // FIXME: This should be a flag
    , m_usesExceptions(false)
    , m_expressionTooDeep(false)
    , m_isBuiltinFunction(codeBlock->isBuiltinFunction())
    , m_isBuiltinDefaultClassConstructor(codeBlock->isBuiltinDefaultClassConstructor())
    , m_usesSloppyEval(functionNode->usesEval() && !functionNode->isStrictMode())
    // FIXME: We should be able to have tail call elimination with the profiler
    // enabled. This is currently not possible because the profiler expects
    // op_will_call / op_did_call pairs before and after a call, which are not
    // compatible with tail calls (we have no way of emitting op_did_call).
    // https://bugs.webkit.org/show_bug.cgi?id=148819
    //
    // Note that we intentionally enable tail call for naked constructors since it does not have special code for "return".
    , m_allowTailCallOptimization(Options::useTailCalls() && !isConstructor() && constructorKind() == ConstructorKind::None && functionNode->isStrictMode())
    , m_allowCallIgnoreResultOptimization(m_defaultAllowCallIgnoreResultOptimization)
    , m_needsToUpdateArrowFunctionContext(functionNode->usesArrowFunction() || functionNode->usesEval())
    , m_ecmaMode(ECMAMode::fromBool(functionNode->isStrictMode()))
    , m_derivedContextType(codeBlock->derivedContextType())
{
#if USE(BUN_JSC_ADDITIONS)
    m_isPrivateBuiltinFunction = m_isBuiltinFunction && (!m_scopeNode->source().provider() || !m_scopeNode->source().provider()->sourceURL());
#endif
    ECMAMode ecmaMode = m_ecmaMode;
    pushPrivateAccessNames(parentPrivateNameEnvironment);

    SymbolTable* functionSymbolTable = SymbolTable::create(m_vm);
    functionSymbolTable->setUsesSloppyEval(m_usesSloppyEval);
    int symbolTableConstantIndex = 0;

    m_cachedParentTDZ = parentScopeTDZVariables;
    m_generatorOrAsyncWrapperFunctionParameterNames = generatorOrAsyncWrapperFunctionParameterNames;

    FunctionParameters& parameters = *functionNode->parameters(); 
    // http://www.ecma-international.org/ecma-262/6.0/index.html#sec-functiondeclarationinstantiation
    // This implements IsSimpleParameterList in the Ecma 2015 spec.
    // If IsSimpleParameterList is false, we will create a strict-mode like arguments object.
    // IsSimpleParameterList is false if the argument list contains any default parameter values,
    // a rest parameter, or any destructuring patterns.
    // If we do have default parameters, destructuring parameters, or a rest parameter, our parameters will be allocated in a different scope.
    bool isSimpleParameterList = parameters.isSimpleParameterList();

    SourceParseMode parseMode = codeBlock->parseMode();

    bool containsArrowOrEvalButNotInArrowBlock = ((functionNode->usesArrowFunction() && functionNode->doAnyInnerArrowFunctionsUseAnyFeature()) || usesEval()) && !m_codeBlock->isArrowFunction();
    bool shouldCaptureSomeOfTheThings = shouldEmitDebugHooks() || functionNode->needsActivation() || containsArrowOrEvalButNotInArrowBlock;

    bool shouldCaptureAllOfTheThings = shouldEmitDebugHooks() || usesEval();
    m_needsArguments = ([&] () {
        if (parseMode != SourceParseMode::ClassFieldInitializerMode) {
            if (!codeBlock->isArrowFunction()) {
                if (functionNode->usesArrowFunction() && isArgumentsUsedInInnerArrowFunction())
                    return true;
                if (functionNode->usesArguments())
                    return true;
                if (shouldEmitDebugHooks())
                    return true;
            }
            if (usesEval())
                return true;
        }
        return false;
    })();

    if (isGeneratorOrAsyncFunctionBodyParseMode(parseMode)) {
        m_needsGeneratorification = true;
        // Generator and AsyncFunction never provides "arguments". "arguments" reference will be resolved in an upper generator function scope.
        m_needsArguments = false;
    } else if (isGeneratorOrAsyncFunctionWrapperParseMode(parseMode)) {
        // Generator does not provide "arguments". Instead, wrapping GeneratorFunction provides "arguments".
        // This is because arguments of a generator should be evaluated before starting it.
        // To workaround it, we evaluate these arguments as arguments of a wrapping generator function, and reference it from a generator.
        //
        //    function *gen(a, b = hello())
        //    {
        //        return {
        //            @generatorNext: function (@generator, @generatorState, @generatorValue, @generatorResumeMode, @generatorFrame)
        //            {
        //                arguments;  // This `arguments` should reference to the gen's arguments.
        //                ...
        //            }
        //        }
        //    }
        //
        // For async functions without await, the body is inlined directly - no body function exists.
        // So we don't need to capture parameters for the body function to access them.
        if (!(isAsyncFunctionWrapperParseMode(parseMode) && functionNode->isAsyncFunctionWithoutAwait())) {
            if (m_needsArguments)
                shouldCaptureSomeOfTheThings = true;
            if (parameters.size()) {
                shouldCaptureSomeOfTheThings = true;
                shouldCaptureAllOfTheThings = true;
            }
        }
    }

    if (shouldCaptureAllOfTheThings)
        functionNode->varDeclarations().markAllVariablesAsCaptured();
    
    auto captures = scopedLambda<bool (UniquedStringImpl*)>([&] (UniquedStringImpl* uid) -> bool {
        if (!shouldCaptureSomeOfTheThings)
            return false;
        if (m_needsArguments && uid == propertyNames().arguments.impl()) {
            // Actually, we only need to capture the arguments object when we "need full activation"
            // because of name scopes. But historically we did it this way, so for now we just preserve
            // the old behavior.
            // FIXME: https://bugs.webkit.org/show_bug.cgi?id=143072
            return true;
        }
        return functionNode->captures(uid);
    });
    auto varKind = [&] (UniquedStringImpl* uid) -> VarKind {
        return captures(uid) ? VarKind::Scope : VarKind::Stack;
    };

    m_calleeRegister.setIndex(CallFrameSlot::callee);

    initializeParameters(parameters);
    ASSERT(!(isSimpleParameterList && m_restParameter));

    emitEnter();

    if (isGeneratorOrAsyncFunctionBodyParseMode(parseMode))
        m_generatorRegister = &m_parameters[static_cast<unsigned>(JSGenerator::Argument::Generator)];

    allocateScope();

    switch (constructorKind()) {
    case ConstructorKind::None:
        break;
    case ConstructorKind::Naked:
        if (!isConstructor()) {
            String constructorName = functionNode->ident().string();
            if (!constructorName || constructorName.isEmpty())
                emitThrowTypeError("Cannot call a constructor without |new|"_s);
            else {
                auto errorMessageStr = tryMakeString("Cannot call a constructor "_s, constructorName, " without |new|"_s);
                if (!errorMessageStr)
                    emitThrowTypeError("Cannot call a constructor without |new|"_s);
                else
                    emitThrowTypeError(Identifier::fromString(m_vm, errorMessageStr));
            }
            return;
        }
        break;
    case ConstructorKind::Base:
    case ConstructorKind::Extends:
        if (!isConstructor()) {
            String constructorName = functionNode->ident().string();
            if (!constructorName || constructorName.isEmpty())
                emitThrowTypeError("Cannot call a class constructor without |new|"_s);
            else {
                auto errorMessageStr = tryMakeString("Cannot call a class constructor "_s, constructorName, " without |new|"_s);
                if (!errorMessageStr)
                    emitThrowTypeError("Cannot call a class constructor without |new|"_s);
                else
                    emitThrowTypeError(Identifier::fromString(m_vm, errorMessageStr));
            }
            return;
        }
        break;
    }
    
    if (functionNameIsInScope(functionNode->ident(), functionNode->functionMode())) {
        ASSERT(parseMode != SourceParseMode::GeneratorBodyMode);
        ASSERT(!isAsyncFunctionBodyParseMode(parseMode));
        bool isDynamicScope = functionNameScopeIsDynamic(usesEval(), ecmaMode.isStrict());
        bool isFunctionNameCaptured = captures(functionNode->ident().impl());
        bool markAsCaptured = isDynamicScope || isFunctionNameCaptured;
        emitPushFunctionNameScope(functionNode->ident(), &m_calleeRegister, markAsCaptured);
    }

    if (shouldCaptureSomeOfTheThings)
        m_lexicalEnvironmentRegister = addVar();

    if (isGeneratorOrAsyncFunctionBodyParseMode(parseMode) || shouldCaptureSomeOfTheThings || shouldEmitTypeProfilerHooks())
        symbolTableConstantIndex = addConstantValue(functionSymbolTable)->index();

    // We can allocate the "var" environment if we don't have default parameter expressions. If we have
    // default parameter expressions, we have to hold off on allocating the "var" environment because
    // the parent scope of the "var" environment is the parameter environment.
    if (isSimpleParameterList)
        initializeVarLexicalEnvironment(symbolTableConstantIndex, functionSymbolTable, shouldCaptureSomeOfTheThings);

    // Need to know what our functions are called. Parameters have some goofy behaviors when it
    // comes to functions of the same name.
    for (FunctionMetadataNode* function : functionNode->functionStack())
        m_functions.add(function->ident().impl());
    
    if (m_needsArguments) {
        // Create the arguments object now. We may put the arguments object into the activation if
        // it is captured. Either way, we create two arguments object variables: one is our
        // private variable that is immutable, and another that is the user-visible variable. The
        // immutable one is only used here, or during formal parameter resolutions if we opt for
        // DirectArguments.
        
        m_argumentsRegister = addVar();
        m_argumentsRegister->ref();
    }
    
    if (m_needsArguments && !ecmaMode.isStrict() && isSimpleParameterList) {
        // If we captured any formal parameter by name, then we use ScopedArguments. Otherwise we
        // use DirectArguments. With ScopedArguments, we lift all of our arguments into the
        // activation.
        bool capturesAnyParameterByName = false;
        if (functionNode->hasCapturedVariables()) {
            for (size_t i = 0; i < parameters.size(); ++i) {
                auto pattern = parameters.at(i).first;
                ASSERT(pattern->isBindingNode());
                const Identifier& ident = static_cast<const BindingNode*>(pattern)->boundProperty();
                if (captures(ident.impl())) {
                    capturesAnyParameterByName = true;
                    break;
                }
            }
        }
        
        if (capturesAnyParameterByName) {
            ASSERT(m_lexicalEnvironmentRegister);
            bool success = functionSymbolTable->trySetArgumentsLength(vm, parameters.size());
            if (!success) [[unlikely]] {
                m_outOfMemoryDuringConstruction = true;
                return;
            }

            // For each parameter, we have two possibilities:
            // Either it's a binding node with no function overlap, in which case it gets a name
            // in the symbol table - or it just gets space reserved in the symbol table. Either
            // way we lift the value into the scope.
            for (unsigned i = 0; i < parameters.size(); ++i) {
                ScopeOffset offset = functionSymbolTable->takeNextScopeOffset(NoLockingNecessary);
                bool success = functionSymbolTable->trySetArgumentOffset(vm, i, offset);
                if (!success) [[unlikely]] {
                    m_outOfMemoryDuringConstruction = true;
                    return;
                }

                unsigned varOrAnonymous = UINT_MAX;

                if (UniquedStringImpl* name = visibleNameForParameter(parameters.at(i).first)) {
                    VarOffset varOffset(offset);
                    SymbolTableEntry entry(varOffset);
                    functionSymbolTable->set(NoLockingNecessary, name, WTF::move(entry));

IGNORE_GCC_WARNINGS_BEGIN("dangling-reference")
                    const Identifier& ident =
                        static_cast<const BindingNode*>(parameters.at(i).first)->boundProperty();
IGNORE_GCC_WARNINGS_END

                    varOrAnonymous = addConstant(ident);
                }

                OpPutToScope::emit(this, m_lexicalEnvironmentRegister, varOrAnonymous, virtualRegisterForArgumentIncludingThis(1 + i), GetPutInfo(ThrowIfNotFound, ResolvedClosureVar, InitializationMode::ScopedArgumentInitialization, ecmaMode), SymbolTableOrScopeDepth::symbolTable(VirtualRegister { symbolTableConstantIndex }), offset.offset());
            }
            
            // This creates a scoped arguments object and copies the overflow arguments into the
            // scope. It's the equivalent of calling ScopedArguments::createByCopying().
            OpCreateScopedArguments::emit(this, m_argumentsRegister, m_lexicalEnvironmentRegister);
        } else {
            // We're going to put all parameters into the DirectArguments object. First ensure
            // that the symbol table knows that this is happening.
            for (unsigned i = 0; i < parameters.size(); ++i) {
                if (UniquedStringImpl* name = visibleNameForParameter(parameters.at(i).first))
                    functionSymbolTable->set(NoLockingNecessary, name, SymbolTableEntry(VarOffset(DirectArgumentsOffset(i))));
            }
            
            OpCreateDirectArguments::emit(this, m_argumentsRegister);
        }
    } else if (isSimpleParameterList) {
        // Create the formal parameters the normal way. Any of them could be captured, or not. If
        // captured, lift them into the scope. We cannot do this if we have default parameter expressions
        // because when default parameter expressions exist, they belong in their own lexical environment
        // separate from the "var" lexical environment.
        for (unsigned i = 0; i < parameters.size(); ++i) {
            UniquedStringImpl* name = visibleNameForParameter(parameters.at(i).first);
            if (!name)
                continue;
            
            if (!captures(name)) {
                // This is the easy case - just tell the symbol table about the argument. It will
                // be accessed directly.
                functionSymbolTable->set(NoLockingNecessary, name, SymbolTableEntry(VarOffset(virtualRegisterForArgumentIncludingThis(1 + i))));
                continue;
            }
            
            ScopeOffset offset = functionSymbolTable->takeNextScopeOffset(NoLockingNecessary);
            functionSymbolTable->set(NoLockingNecessary, name, SymbolTableEntry(VarOffset(offset)));
IGNORE_GCC_WARNINGS_BEGIN("dangling-reference")
            const Identifier& ident =
                static_cast<const BindingNode*>(parameters.at(i).first)->boundProperty();
IGNORE_GCC_WARNINGS_END
            
            OpPutToScope::emit(this, m_lexicalEnvironmentRegister, addConstant(ident), virtualRegisterForArgumentIncludingThis(1 + i), GetPutInfo(ThrowIfNotFound, ResolvedClosureVar, InitializationMode::NotInitialization, ecmaMode), SymbolTableOrScopeDepth::symbolTable(VirtualRegister { symbolTableConstantIndex }), offset.offset());
        }
    }
    
    if (m_needsArguments && (ecmaMode.isStrict() || !isSimpleParameterList)) {
        // Allocate a cloned arguments object.
        OpCreateClonedArguments::emit(this, m_argumentsRegister);
    }
    
    // There are some variables that need to be preinitialized to something other than Undefined:
    //
    // - "arguments": unless it's used as a function or parameter, this should refer to the
    //   arguments object.
    //
    // - functions: these always override everything else.
    //
    // The most logical way to do all of this is to initialize none of the variables until now,
    // and then initialize them in BytecodeGenerator::generate() in such an order that the rules
    // for how these things override each other end up holding. We would initialize "arguments" first, 
    // then all arguments, then the functions.
    //
    // But some arguments are already initialized by default, since if they aren't captured and we
    // don't have "arguments" then we just point the symbol table at the stack slot of those
    // arguments. We end up initializing the rest of the arguments that have an uncomplicated
    // binding (i.e. don't involve destructuring) above when figuring out how to lay them out,
    // because that's just the simplest thing. This means that when we initialize them, we have to
    // watch out for the things that override arguments (namely, functions).
    
    // This is our final act of weirdness. "arguments" is overridden by everything except the
    // callee. We add it to the symbol table if it's not already there and it's not an argument.
    bool shouldCreateArgumentsVariableInParameterScope = false;
    if (m_needsArguments) {
        // If "arguments" is overridden by a function or destructuring parameter name, then it's
        // OK for us to call createVariable() because it won't change anything. It's also OK for
        // us to them tell BytecodeGenerator::generate() to write to it because it will do so
        // before it initializes functions and destructuring parameters. But if "arguments" is
        // overridden by a "simple" function parameter, then we have to bail: createVariable()
        // would assert and BytecodeGenerator::generate() would write the "arguments" after the
        // argument value had already been properly initialized.
        
        bool haveParameterNamedArguments = false;
        for (unsigned i = 0; i < parameters.size(); ++i) {
            UniquedStringImpl* name = visibleNameForParameter(parameters.at(i).first);
            if (name == propertyNames().arguments.impl()) {
                haveParameterNamedArguments = true;
                break;
            }
        }

        bool shouldCreateArgumensVariable = !haveParameterNamedArguments
            && !SourceParseModeSet(SourceParseMode::ArrowFunctionMode, SourceParseMode::AsyncArrowFunctionMode, SourceParseMode::ClassFieldInitializerMode).contains(m_codeBlock->parseMode());
        shouldCreateArgumentsVariableInParameterScope = shouldCreateArgumensVariable && !isSimpleParameterList;
        // Do not create arguments variable in case of Arrow function. Value will be loaded from parent scope
        if (shouldCreateArgumensVariable && !shouldCreateArgumentsVariableInParameterScope) {
            createVariable(
                propertyNames().arguments, varKind(propertyNames().arguments.impl()), functionSymbolTable);

            m_needToInitializeArguments = true;
        }
    }

    for (FunctionMetadataNode* function : functionNode->functionStack()) {
        const Identifier& ident = function->ident();
        createVariable(ident, varKind(ident.impl()), functionSymbolTable);
        m_functionsToInitialize.append(std::make_pair(function, NormalFunctionVariable));
    }
    for (auto& entry : functionNode->varDeclarations()) {
        ASSERT(!entry.value.isLet() && !entry.value.isConst());
        if (!entry.value.isVar()) // This is either a parameter or callee.
            continue;
        if (shouldCreateArgumentsVariableInParameterScope && entry.key.get() == propertyNames().arguments.impl())
            continue;
        if (generatorOrAsyncWrapperFunctionParameterNames && generatorOrAsyncWrapperFunctionParameterNames->contains(entry.key.get()))
            continue;
        createVariable(Identifier::fromUid(m_vm, entry.key.get()), varKind(entry.key.get()), functionSymbolTable, IgnoreExisting);
    }


    if (functionNode->needsNewTargetRegisterForThisScope() || isNewTargetUsedInInnerArrowFunction() || usesEval())
        m_newTargetRegister = addVar();

    auto shouldEmitToThis = [&] {
        if (functionNode->usesThis() || usesEval() || m_scopeNode->doAnyInnerArrowFunctionsUseThis() || m_scopeNode->doAnyInnerArrowFunctionsUseEval())
            return true;
        if ((functionNode->usesSuperProperty() || m_scopeNode->doAnyInnerArrowFunctionsUseSuperProperty()) && !ecmaMode.isStrict()) {
            // We must emit to_this when we're not in strict mode because we
            // will convert |this| to an object, and that object may be passed
            // to a strict function as |this|. This is observable because that
            // strict function's to_this will just return the object.
            //
            // We don't need to emit this for strict-mode code because
            // strict-mode code may call another strict function, which will
            // to_this if it directly uses this; this is OK, because we defer
            // to_this until |this| is used directly. Strict-mode code might
            // also call a sloppy mode function, and that will to_this, which
            // will defer the conversion, again, until necessary.
            return true;
        }
        return false;
    };

    switch (parseMode) {
    case SourceParseMode::GeneratorWrapperFunctionMode:
    case SourceParseMode::GeneratorWrapperMethodMode:
    case SourceParseMode::AsyncGeneratorWrapperMethodMode:
    case SourceParseMode::AsyncGeneratorWrapperFunctionMode: {
        m_generatorRegister = addVar();

        // FIXME: Emit to_this only when Generator uses it.
        // https://bugs.webkit.org/show_bug.cgi?id=151586
        emitToThis();

        break;
    }

    case SourceParseMode::AsyncArrowFunctionMode:
    case SourceParseMode::AsyncMethodMode:
    case SourceParseMode::AsyncFunctionMode: {
        ASSERT(!isConstructor());
        ASSERT(constructorKind() == ConstructorKind::None);

        bool isAsyncFunctionWithoutAwait = m_scopeNode->isAsyncFunctionWithoutAwait();
        // Check if this async function body doesn't use await.
        // If so, we can skip generator creation entirely.
        if (!isAsyncFunctionWithoutAwait) {
            m_generatorRegister = addVar();
            m_promiseRegister = addVar();
        }

        bool willEmitToThis = false;
        if (parseMode != SourceParseMode::AsyncArrowFunctionMode) {
            // FIXME: Emit to_this only when AsyncFunctionBody uses it.
            // https://bugs.webkit.org/show_bug.cgi?id=151586
            if (isAsyncFunctionWithoutAwait)
                willEmitToThis = shouldEmitToThis();
            else
                willEmitToThis = true;
        }
        if (willEmitToThis)
            emitToThis();

        if (!isAsyncFunctionWithoutAwait) {
            emitNewPromise(promiseRegister());
            emitNewAsyncFunctionGenerator(m_generatorRegister);
            emitPutInternalField(generatorRegister(), static_cast<unsigned>(JSAsyncFunctionGenerator::Field::Context), promiseRegister());
        }
        break;
    }

    case SourceParseMode::AsyncGeneratorBodyMode:
    case SourceParseMode::AsyncFunctionBodyMode:
    case SourceParseMode::AsyncArrowFunctionBodyMode:
    case SourceParseMode::GeneratorBodyMode: {
        // |this| is already filled correctly before here.
        if (m_newTargetRegister)
            emitLoad(m_newTargetRegister, jsUndefined());
        break;
    }

    case SourceParseMode::ArrowFunctionMode:
        break;

    default: {
        if (isConstructor()) {
            if (m_newTargetRegister)
                move(m_newTargetRegister, &m_thisRegister);
            switch (constructorKind()) {
            case ConstructorKind::Naked:
                // Naked constructor not create |this| automatically.
                break;
            case ConstructorKind::None:
            case ConstructorKind::Base:
                emitCreateThis(&m_thisRegister);
                if (privateBrandRequirement() == PrivateBrandRequirement::Needed)
                    emitInstallPrivateBrand(&m_thisRegister);

                emitInstanceFieldInitializationIfNeeded(&m_thisRegister, &m_calleeRegister, m_scopeNode->position(), m_scopeNode->position(), m_scopeNode->position());
                break;
            case ConstructorKind::Extends:
                moveEmptyValue(&m_thisRegister);
                break;
            }
        } else {
            switch (constructorKind()) {
            case ConstructorKind::None: {
                if (shouldEmitToThis())
                    emitToThis();
                break;
            }
            case ConstructorKind::Naked:
            case ConstructorKind::Base:
            case ConstructorKind::Extends:
                RELEASE_ASSERT_NOT_REACHED();
                break;
            }
        }
        break;
    }
    }

    // We need load |super| & |this| for arrow function before initializeDefaultParameterValuesAndSetupFunctionScopeStack
    // if we have default parameter expression. Because |super| & |this| values can be used there
    if ((SourceParseModeSet(SourceParseMode::ArrowFunctionMode, SourceParseMode::AsyncArrowFunctionMode).contains(parseMode) && !isSimpleParameterList) || parseMode == SourceParseMode::AsyncArrowFunctionBodyMode) {
        if (functionNode->usesThis() || functionNode->usesSuperProperty())
            emitLoadThisFromArrowFunctionLexicalEnvironment();

        if (m_scopeNode->needsNewTargetRegisterForThisScope())
            emitLoadNewTargetFromArrowFunctionLexicalEnvironment();
    }

    if (needsToUpdateArrowFunctionContext() && !codeBlock->isArrowFunction()) {
        bool canReuseLexicalEnvironment = isSimpleParameterList;
        initializeArrowFunctionContextScopeIfNeeded(functionSymbolTable, canReuseLexicalEnvironment);
        emitPutThisToArrowFunctionContextScope();
        emitPutNewTargetToArrowFunctionContextScope();
        emitPutDerivedConstructorToArrowFunctionContextScope();
    }

    if (isAsyncFunctionWrapperParseMode(parseMode) && !isSimpleParameterList)
        m_asyncFuncParametersTryCatchInfo = { newLabel(), newTemporary() };

    asyncFuncParametersTryCatchWrap([&]() {
        // All "addVar()"s needs to happen before "initializeDefaultParameterValuesAndSetupFunctionScopeStack()" is called
        // because a function's default parameter ExpressionNodes will use temporary registers.
        initializeDefaultParameterValuesAndSetupFunctionScopeStack(parameters, isSimpleParameterList, functionNode, functionSymbolTable, symbolTableConstantIndex, captures, shouldCreateArgumentsVariableInParameterScope);
    });

    // If we don't have  default parameter expression, then loading |this| inside an arrow function must be done
    // after initializeDefaultParameterValuesAndSetupFunctionScopeStack() because that function sets up the
    // SymbolTable stack and emitLoadThisFromArrowFunctionLexicalEnvironment() consults the SymbolTable stack
    if (SourceParseModeSet(SourceParseMode::ArrowFunctionMode, SourceParseMode::AsyncArrowFunctionMode).contains(parseMode) && isSimpleParameterList) {
        if (functionNode->usesThis() || functionNode->usesSuperProperty())
            emitLoadThisFromArrowFunctionLexicalEnvironment();
    
        if (m_scopeNode->needsNewTargetRegisterForThisScope())
            emitLoadNewTargetFromArrowFunctionLexicalEnvironment();
    }

    if (isGeneratorWrapperParseMode(parseMode))
        emitCreateGenerator(m_generatorRegister, &m_calleeRegister);
    else if (isAsyncGeneratorWrapperParseMode(parseMode))
        emitCreateAsyncGenerator(m_generatorRegister, &m_calleeRegister);
    
    // Set up the lexical environment scope as the generator frame. We store the saved and resumed generator registers into this scope with the symbol keys.
    // Since they are symbol keyed, these variables cannot be reached from the usual code.
    if (isGeneratorOrAsyncFunctionBodyParseMode(parseMode)) {
        m_generatorFrameSymbolTable.set(m_vm, functionSymbolTable);
        m_generatorFrameSymbolTableIndex = symbolTableConstantIndex;
        if (m_lexicalEnvironmentRegister)
            move(generatorFrameRegister(), m_lexicalEnvironmentRegister);
        else {
            // It would be possible that generator does not need to suspend and resume any registers.
            // In this case, we would like to avoid creating a lexical environment as much as possible.
            // op_create_generator_frame_environment is a marker, which is similar to op_yield.
            // Generatorification inserts lexical environment creation if necessary. Otherwise, we convert it to op_mov frame, `undefined`.
            OpCreateGeneratorFrameEnvironment::emit(this, generatorFrameRegister(), scopeRegister(), VirtualRegister { symbolTableConstantIndex }, addConstantValue(jsUndefined()));
        }
        static_assert(static_cast<unsigned>(JSGenerator::Field::Frame) == static_cast<unsigned>(JSAsyncGenerator::Field::Frame));
        emitPutInternalField(generatorRegister(), static_cast<unsigned>(JSGenerator::Field::Frame), generatorFrameRegister());
    }

    bool shouldInitializeBlockScopedFunctions = false; // We generate top-level function declarations in ::generate().
    pushLexicalScope(m_scopeNode, ScopeType::LetConstScope, TDZCheckOptimization::Optimize, NestedScopeType::IsNotNested, nullptr, shouldInitializeBlockScopedFunctions);
}

BytecodeGenerator::BytecodeGenerator(VM& vm, EvalNode* evalNode, UnlinkedEvalCodeBlock* codeBlock, OptionSet<CodeGenerationMode> codeGenerationMode, const RefPtr<TDZEnvironmentLink>& parentScopeTDZVariables, const FixedVector<Identifier>*, const PrivateNameEnvironment* parentPrivateNameEnvironment)
    : BytecodeGeneratorBase(makeUnique<UnlinkedCodeBlockGenerator>(vm, codeBlock), CodeBlock::llintBaselineCalleeSaveSpaceAsVirtualRegisters())
    , m_codeGenerationMode(codeGenerationMode)
    , m_scopeNode(evalNode)
    , m_thisRegister(CallFrame::thisArgumentOffset())
    , m_codeType(EvalCode)
    , m_vm(vm)
    , m_usesExceptions(false)
    , m_expressionTooDeep(false)
    , m_isBuiltinFunction(false)
    , m_usesSloppyEval(evalNode->usesEval() && !evalNode->isStrictMode())
    , m_allowTailCallOptimization(false)
    , m_allowCallIgnoreResultOptimization(m_defaultAllowCallIgnoreResultOptimization)
    , m_needsToUpdateArrowFunctionContext(evalNode->usesArrowFunction() || evalNode->usesEval())
    , m_ecmaMode(ECMAMode::fromBool(evalNode->isStrictMode()))
    , m_derivedContextType(codeBlock->derivedContextType())
{
    m_codeBlock->setNumParameters(1);

    pushPrivateAccessNames(parentPrivateNameEnvironment);

    m_cachedParentTDZ = parentScopeTDZVariables;

    emitEnter();
    allocateScope();
    m_topLevelScopeRegister = addVar();
    m_topLevelScopeRegister->ref();
    move(m_topLevelScopeRegister, scopeRegister());

    for (FunctionMetadataNode* function : evalNode->functionStack()) {
        m_codeBlock->addFunctionDecl(makeFunction(function));
        m_functionsToInitialize.append(std::make_pair(function, TopLevelFunctionVariable));
    }

    const VariableEnvironment& varDeclarations = evalNode->varDeclarations();
    Vector<Identifier, 0, UnsafeVectorOverflow> variables;
    Vector<Identifier, 0, UnsafeVectorOverflow> hoistedFunctions;
    for (auto& entry : varDeclarations) {
        ASSERT(entry.value.isVar());
        ASSERT(entry.key->isAtom() || entry.key->isSymbol());
        if (entry.value.isSloppyModeHoistedFunction())
            hoistedFunctions.append(Identifier::fromUid(m_vm, entry.key.get()));
        else if (!entry.value.isFunction())
            variables.append(Identifier::fromUid(m_vm, entry.key.get()));
    }
    codeBlock->adoptVariables(WTF::move(variables));
    codeBlock->adoptFunctionHoistingCandidates(WTF::move(hoistedFunctions));
    
    if (evalNode->needsNewTargetRegisterForThisScope())
        m_newTargetRegister = addVar();

    if (codeBlock->isArrowFunctionContext() && (evalNode->usesThis() || evalNode->usesSuperProperty()))
        emitLoadThisFromArrowFunctionLexicalEnvironment();

    if (evalNode->needsNewTargetRegisterForThisScope())
        emitLoadNewTargetFromArrowFunctionLexicalEnvironment();

    if (needsToUpdateArrowFunctionContext() && !codeBlock->isArrowFunctionContext() && !isDerivedConstructorContext()) {
        initializeArrowFunctionContextScopeIfNeeded();
        emitPutThisToArrowFunctionContextScope();
    }
    
    bool shouldInitializeBlockScopedFunctions = false; // We generate top-level function declarations in ::generate().
    pushLexicalScope(m_scopeNode, ScopeType::LetConstScope, TDZCheckOptimization::Optimize, NestedScopeType::IsNotNested, nullptr, shouldInitializeBlockScopedFunctions);
}

BytecodeGenerator::BytecodeGenerator(VM& vm, ModuleProgramNode* moduleProgramNode, UnlinkedModuleProgramCodeBlock* codeBlock, OptionSet<CodeGenerationMode> codeGenerationMode, const RefPtr<TDZEnvironmentLink>& parentScopeTDZVariables, const FixedVector<Identifier>*, const PrivateNameEnvironment*)
    : BytecodeGeneratorBase(makeUnique<UnlinkedCodeBlockGenerator>(vm, codeBlock), CodeBlock::llintBaselineCalleeSaveSpaceAsVirtualRegisters())
    , m_codeGenerationMode(codeGenerationMode)
    , m_scopeNode(moduleProgramNode)
    , m_thisRegister(CallFrame::thisArgumentOffset())
    , m_codeType(ModuleCode)
    , m_vm(vm)
    , m_defaultAllowCallIgnoreResultOptimization(!Options::evalMode())
    , m_usesExceptions(false)
    , m_expressionTooDeep(false)
    , m_isBuiltinFunction(false)
    , m_usesSloppyEval(false)
    , m_allowTailCallOptimization(false)
    , m_allowCallIgnoreResultOptimization(m_defaultAllowCallIgnoreResultOptimization)
    , m_needsToUpdateArrowFunctionContext(moduleProgramNode->usesArrowFunction() || moduleProgramNode->usesEval())
    , m_ecmaMode(ECMAMode::strict())
{
    ASSERT_UNUSED(parentScopeTDZVariables, !parentScopeTDZVariables);
    codeBlock->setVariableDeclarations(moduleProgramNode->varDeclarations());

    SymbolTable* moduleEnvironmentSymbolTable = SymbolTable::create(m_vm);
    moduleEnvironmentSymbolTable->setUsesSloppyEval(m_usesSloppyEval);
    moduleEnvironmentSymbolTable->setScopeType(SymbolTable::ScopeType::LexicalScope);

    bool shouldCaptureAllOfTheThings = shouldEmitDebugHooks() || usesEval();
    if (shouldCaptureAllOfTheThings)
        moduleProgramNode->varDeclarations().markAllVariablesAsCaptured();

    auto captures = [&] (UniquedStringImpl* uid) -> bool {
        return moduleProgramNode->captures(uid);
    };
    auto lookUpVarKind = [&] (UniquedStringImpl* uid, const VariableEnvironmentEntry& entry) -> VarKind {
        // Allocate the exported variables in the module environment.
        if (entry.isExported())
            return VarKind::Scope;

        // Allocate the namespace variables in the module environment to instantiate
        // it from the outside of the module code.
        if (entry.isImportedNamespace())
            return VarKind::Scope;

        if (entry.isCaptured())
            return VarKind::Scope;
        return captures(uid) ? VarKind::Scope : VarKind::Stack;
    };

    if (moduleProgramNode->usesAwait()) {
        m_needsGeneratorification = true;
        initializeNextParameter(); // |this|
        for (unsigned i = 0; i < JSGenerator::Argument::NumberOfArguments; ++i)
            initializeNextParameter();
        m_generatorRegister = &m_parameters[static_cast<unsigned>(AbstractModuleRecord::Argument::Generator)];
    }

    emitEnter();
    allocateScope();
    m_topLevelScopeRegister = addVar();
    m_topLevelScopeRegister->ref();
    move(m_topLevelScopeRegister, scopeRegister());

    m_calleeRegister.setIndex(CallFrameSlot::callee);

    m_codeBlock->setNumParameters(static_cast<unsigned>(AbstractModuleRecord::Argument::NumberOfArguments) + 1); // Allocate space for "this" + async module arguments.

    // Now declare all variables.

    createVariable(m_vm.propertyNames->starNamespacePrivateName, VarKind::Scope, moduleEnvironmentSymbolTable, VerifyExisting);
    if (moduleProgramNode->features() & ImportMetaFeature)
        createVariable(m_vm.propertyNames->builtinNames().metaPrivateName(), VarKind::Scope, moduleEnvironmentSymbolTable, VerifyExisting);

    for (auto& entry : moduleProgramNode->varDeclarations()) {
        ASSERT(!entry.value.isLet() && !entry.value.isConst());
        if (!entry.value.isVar()) // This is either a parameter or callee.
            continue;
        // Imported bindings are not allocated in the module environment as usual variables' way.
        // These references remain the "Dynamic" in the unlinked code block. Later, when linking
        // the code block, we resolve the reference to the "ModuleVar".
        if (entry.value.isImported() && !entry.value.isImportedNamespace())
            continue;
        createVariable(Identifier::fromUid(m_vm, entry.key.get()), lookUpVarKind(entry.key.get(), entry.value), moduleEnvironmentSymbolTable, IgnoreExisting);
    }

    VariableEnvironment& lexicalVariables = moduleProgramNode->lexicalVariables();
    instantiateLexicalVariables(lexicalVariables, ScopeType::LetConstScope, moduleEnvironmentSymbolTable, ScopeRegisterType::Block, lookUpVarKind);

    // We keep the symbol table in the constant pool.
    RegisterID* constantSymbolTable = nullptr;
    if (shouldEmitTypeProfilerHooks() || moduleProgramNode->usesAwait())
        constantSymbolTable = addConstantValue(moduleEnvironmentSymbolTable);
    else
        constantSymbolTable = addConstantValue(moduleEnvironmentSymbolTable->cloneScopePart(m_vm, SymbolTable::PropagateCloneInvalidationToOriginal::No));

    if (moduleProgramNode->usesAwait()) {
        m_generatorFrameSymbolTable.set(m_vm, moduleEnvironmentSymbolTable);
        m_generatorFrameSymbolTableIndex = constantSymbolTable->index();
        emitPutInternalField(generatorRegister(), static_cast<unsigned>(AbstractModuleRecord::Field::Frame), generatorFrameRegister());
    }

    pushTDZVariables(lexicalVariables, TDZCheckOptimization::Optimize, TDZRequirement::UnderTDZ);
    bool isWithScope = false;

    m_lexicalScopeStack.append({ moduleEnvironmentSymbolTable, m_topLevelScopeRegister, isWithScope, constantSymbolTable->index() });
    emitPrefillStackTDZVariables(lexicalVariables, moduleEnvironmentSymbolTable);

    // makeFunction assumes that there's correct TDZ stack entries.
    // So it should be called after putting our lexical environment to the TDZ stack correctly.

    for (FunctionMetadataNode* function : moduleProgramNode->functionStack()) {
        const auto& iterator = moduleProgramNode->lexicalVariables().find(function->ident().impl());
        RELEASE_ASSERT(iterator != moduleProgramNode->lexicalVariables().end());
        RELEASE_ASSERT(!iterator->value.isImported());

        VarKind varKind = lookUpVarKind(iterator->key.get(), iterator->value);
        if (varKind == VarKind::Scope) {
            // http://www.ecma-international.org/ecma-262/6.0/#sec-moduledeclarationinstantiation
            // Section 15.2.1.16.4, step 16-a-iv-1.
            // All heap allocated function declarations should be instantiated when the module environment
            // is created. They include the exported function declarations and not-exported-but-heap-allocated
            // function declarations. This is required because exported function should be instantiated before
            // executing the any module in the dependency graph. This enables the modules to link the imported
            // bindings before executing the any module code.
            //
            // And since function declarations are instantiated before executing the module body code, the spec
            // allows the functions inside the module to be executed before its module body is executed under
            // the circular dependencies. The following is the example.
            //
            // Module A (executed first):
            //    import { b } from "B";
            //    // Here, the module "B" is not executed yet, but the function declaration is already instantiated.
            //    // So we can call the function exported from "B".
            //    b();
            //
            //    export function a() {
            //    }
            //
            // Module B (executed second):
            //    import { a } from "A";
            //
            //    export function b() {
            //        c();
            //    }
            //
            //    // c is not exported, but since it is referenced from the b, we should instantiate it before
            //    // executing the "B" module code.
            //    function c() {
            //        a();
            //    }
            //
            // Module Entrypoint (executed last):
            //    import "B";
            //    import "A";
            //
            m_codeBlock->addFunctionDecl(makeFunction(function));
        } else {
            // Stack allocated functions can be allocated when executing the module's body.
            m_functionsToInitialize.append(std::make_pair(function, NormalFunctionVariable));
        }
    }

    // Remember the constant register offset to the top-most symbol table. This symbol table will be
    // cloned in the code block linking. After that, to create the module environment, we retrieve
    // the cloned symbol table from the linked code block by using this offset.
    codeBlock->setModuleEnvironmentSymbolTableConstantRegisterOffset(constantSymbolTable->index());
}

BytecodeGenerator::~BytecodeGenerator() = default;

void BytecodeGenerator::initializeDefaultParameterValuesAndSetupFunctionScopeStack(
    FunctionParameters& parameters, bool isSimpleParameterList, FunctionNode* functionNode, SymbolTable* functionSymbolTable, 
    int symbolTableConstantIndex, const ScopedLambda<bool (UniquedStringImpl*)>& captures, bool shouldCreateArgumentsVariableInParameterScope)
{
    Vector<std::pair<Identifier, RefPtr<RegisterID>>> valuesToMoveIntoVars;
    ASSERT(!(isSimpleParameterList && shouldCreateArgumentsVariableInParameterScope));
    if (!isSimpleParameterList) {
        // Refer to the ES6 spec section 9.2.12: http://www.ecma-international.org/ecma-262/6.0/index.html#sec-functiondeclarationinstantiation
        // This implements step 21.
        VariableEnvironment environment;
        Vector<Identifier> allParameterNames; 
        for (unsigned i = 0; i < parameters.size(); i++)
            parameters.at(i).first->collectBoundIdentifiers(allParameterNames);
        if (shouldCreateArgumentsVariableInParameterScope)
            allParameterNames.append(propertyNames().arguments);
        IdentifierSet parameterSet;
        for (auto& ident : allParameterNames) {
            parameterSet.add(ident.impl());
            auto addResult = environment.add(ident);
            addResult.iterator->value.setIsLet(); // When we have default parameter expressions, parameters act like "let" variables.
            if (captures(ident.impl()))
                addResult.iterator->value.setIsCaptured();
        }
        // This implements step 25 of section 9.2.12.
        pushLexicalScopeInternal(environment, TDZCheckOptimization::Optimize, NestedScopeType::IsNotNested, nullptr, TDZRequirement::UnderTDZ, ScopeType::LetConstScope, ScopeRegisterType::Block);

        if (shouldCreateArgumentsVariableInParameterScope) {
            Variable argumentsVariable = variable(propertyNames().arguments); 
            initializeVariable(argumentsVariable, m_argumentsRegister);
            liftTDZCheckIfPossible(argumentsVariable);
        }

        RefPtr<RegisterID> temp = newTemporary();
        for (unsigned i = 0; i < parameters.size(); i++) {
            std::pair<DestructuringPatternNode*, ExpressionNode*> parameter = parameters.at(i);
            if (parameter.first->isRestParameter())
                continue;
            if ((i + 1) < m_parameters.size())
                move(temp.get(), &m_parameters[i + 1]);
            else
                emitGetArgument(temp.get(), i);
            if (parameter.second) {
                Ref<Label> skipDefaultParameterBecauseNotUndefined = newLabel();
                emitJumpIfFalse(emitIsUndefined(newTemporary(), temp.get()), skipDefaultParameterBecauseNotUndefined.get());
                emitNode(temp.get(), parameter.second);
                emitLabel(skipDefaultParameterBecauseNotUndefined.get());
            }

            parameter.first->bindValue(*this, temp.get());
        }

        if (m_restParameter)
            m_restParameter->emit(*this);

        // Final act of weirdness for default parameters. If a "var" also
        // has the same name as a parameter, it should start out as the
        // value of that parameter. Note, though, that they will be distinct
        // bindings.
        // This is step 28 of section 9.2.12. 
        for (auto& entry : functionNode->varDeclarations()) {
            if (!entry.value.isVar()) // This is either a parameter or callee.
                continue;

            if (parameterSet.contains(entry.key)) {
                Identifier ident = Identifier::fromUid(m_vm, entry.key.get());
                Variable var = variable(ident);
                RegisterID* scope = emitResolveScope(nullptr, var);
                RefPtr<RegisterID> value = emitGetFromScope(newTemporary(), scope, var, DoNotThrowIfNotFound);
                valuesToMoveIntoVars.append(std::make_pair(ident, value));
            }
        }

        // Functions with default parameter expressions must have a separate environment
        // record for parameters and "var"s. The "var" environment record must have the
        // parameter environment record as its parent.
        // See step 28 of section 9.2.12.
        bool hasCapturedVariables = !!m_lexicalEnvironmentRegister; 
        initializeVarLexicalEnvironment(symbolTableConstantIndex, functionSymbolTable, hasCapturedVariables);
    }

    // This completes step 28 of section 9.2.12.
    for (unsigned i = 0; i < valuesToMoveIntoVars.size(); i++) {
        ASSERT(!isSimpleParameterList);
        Variable var = variable(valuesToMoveIntoVars[i].first);
        RegisterID* scope = emitResolveScope(nullptr, var);
        emitPutToScope(scope, var, valuesToMoveIntoVars[i].second.get(), DoNotThrowIfNotFound, InitializationMode::NotInitialization);
    }
}

bool BytecodeGenerator::needsDerivedConstructorInArrowFunctionLexicalEnvironment()
{
    ASSERT(m_codeBlock->isClassContext() || !(isConstructor() && constructorKind() == ConstructorKind::Extends));
    return m_codeBlock->isClassContext() && isSuperUsedInInnerArrowFunction();
}

void BytecodeGenerator::initializeArrowFunctionContextScopeIfNeeded(SymbolTable* functionSymbolTable, bool canReuseLexicalEnvironment)
{
    ASSERT(!m_arrowFunctionContextLexicalEnvironmentRegister);

    if (canReuseLexicalEnvironment && m_lexicalEnvironmentRegister) {
        RELEASE_ASSERT(!m_codeBlock->isArrowFunction());
        RELEASE_ASSERT(functionSymbolTable);

        m_arrowFunctionContextLexicalEnvironmentRegister = m_lexicalEnvironmentRegister;
        
        ScopeOffset offset;
        
        if (isThisUsedInInnerArrowFunction()) {
            offset = functionSymbolTable->takeNextScopeOffset(NoLockingNecessary);
            functionSymbolTable->add(NoLockingNecessary, propertyNames().builtinNames().thisPrivateName().impl(), SymbolTableEntry(VarOffset(offset)));
        }

        if (m_codeType == FunctionCode && isNewTargetUsedInInnerArrowFunction()) {
            offset = functionSymbolTable->takeNextScopeOffset();
            functionSymbolTable->add(NoLockingNecessary, propertyNames().builtinNames().newTargetLocalPrivateName().impl(), SymbolTableEntry(VarOffset(offset)));
        }
        
        if (needsDerivedConstructorInArrowFunctionLexicalEnvironment()) {
            offset = functionSymbolTable->takeNextScopeOffset(NoLockingNecessary);
            functionSymbolTable->add(NoLockingNecessary, propertyNames().builtinNames().derivedConstructorPrivateName().impl(), SymbolTableEntry(VarOffset(offset)));
        }

        return;
    }

    VariableEnvironment environment;

    if (isThisUsedInInnerArrowFunction()) {
        auto addResult = environment.add(propertyNames().builtinNames().thisPrivateName());
        addResult.iterator->value.setIsCaptured();
        addResult.iterator->value.setIsLet();
    }
    
    if (m_codeType == FunctionCode && isNewTargetUsedInInnerArrowFunction()) {
        auto addTarget = environment.add(propertyNames().builtinNames().newTargetLocalPrivateName());
        addTarget.iterator->value.setIsCaptured();
        addTarget.iterator->value.setIsLet();
    }

    if (needsDerivedConstructorInArrowFunctionLexicalEnvironment()) {
        auto derivedConstructor = environment.add(propertyNames().builtinNames().derivedConstructorPrivateName());
        derivedConstructor.iterator->value.setIsCaptured();
        derivedConstructor.iterator->value.setIsLet();
    }

    if (environment.size() > 0) {
        size_t size = m_lexicalScopeStack.size();
        pushLexicalScopeInternal(environment, TDZCheckOptimization::Optimize, NestedScopeType::IsNotNested, nullptr, TDZRequirement::UnderTDZ, ScopeType::LetConstScope, ScopeRegisterType::Block);

        ASSERT_UNUSED(size, m_lexicalScopeStack.size() == size + 1);

        m_arrowFunctionContextLexicalEnvironmentRegister = m_lexicalScopeStack.last().m_scope;
    }
}

RegisterID* BytecodeGenerator::initializeNextParameter()
{
    VirtualRegister reg = virtualRegisterForArgumentIncludingThis(m_codeBlock->numParameters());
    m_parameters.grow(m_parameters.size() + 1);
    auto& parameter = registerFor(reg);
    parameter.setIndex(reg);
    m_codeBlock->setNumParameters(m_codeBlock->numParameters() + 1);
    return &parameter;
}

void BytecodeGenerator::initializeParameters(FunctionParameters& parameters)
{
    // Make sure the code block knows about all of our parameters, and make sure that parameters
    // needing destructuring are noted.
    m_thisRegister.setIndex(VirtualRegister(initializeNextParameter()->index())); // this

    bool nonSimpleArguments = false;
    for (unsigned i = 0; i < parameters.size(); ++i) {
        auto parameter = parameters.at(i);
        auto pattern = parameter.first;
        if (pattern->isRestParameter()) {
            RELEASE_ASSERT(!m_restParameter);
            m_restParameter = static_cast<RestParameterNode*>(pattern);
            nonSimpleArguments = true;
            continue;
        }
        if (parameter.second) {
            nonSimpleArguments = true;
            continue;
        }
        if (!nonSimpleArguments)
            initializeNextParameter();
    }
}

void BytecodeGenerator::initializeVarLexicalEnvironment(int symbolTableConstantIndex, SymbolTable* functionSymbolTable, bool hasCapturedVariables)
{
    if (hasCapturedVariables) {
        RELEASE_ASSERT(m_lexicalEnvironmentRegister);
        OpCreateLexicalEnvironment::emit(this, m_lexicalEnvironmentRegister, scopeRegister(), VirtualRegister { symbolTableConstantIndex }, addConstantValue(jsUndefined()));

        move(scopeRegister(), m_lexicalEnvironmentRegister);

        pushLocalControlFlowScope();
    }
    bool isWithScope = false;
    m_lexicalScopeStack.append({ functionSymbolTable, m_lexicalEnvironmentRegister, isWithScope, symbolTableConstantIndex });
    m_varScopeLexicalScopeStackIndex = m_lexicalScopeStack.size() - 1;
}

UniquedStringImpl* BytecodeGenerator::visibleNameForParameter(DestructuringPatternNode* pattern)
{
    if (pattern->isBindingNode()) {
        const Identifier& ident = static_cast<const BindingNode*>(pattern)->boundProperty();
        if (!m_functions.contains(ident.impl()))
            return ident.impl();
    }
    return nullptr;
}

RegisterID* BytecodeGenerator::newBlockScopeVariable()
{
    reclaimFreeRegisters();

    return newRegister();
}

Ref<LabelScope> BytecodeGenerator::newLabelScope(LabelScope::Type type, const Identifier* name)
{
    shrinkToFit(m_labelScopes);

    // Allocate new label scope.
    m_labelScopes.append(type, name, labelScopeDepth(), newLabel(), type == LabelScope::Loop ? RefPtr<Label>(newLabel()) : RefPtr<Label>()); // Only loops have continue targets.
    return m_labelScopes.last();
}

void BytecodeGenerator::emitEnter()
{
    OpEnter::emit(this);

    if (Options::optimizeRecursiveTailCalls()) [[likely]] {
        // We must add the end of op_enter as a potential jump target, because the bytecode parser may decide to split its basic block
        // to have somewhere to jump to if there is a recursive tail-call that points to this function.
        // This disables peephole optimizations when an instruction is a jump target
        disablePeepholeOptimization();
    }
}

void BytecodeGenerator::emitLoopHint()
{
    OpLoopHint::emit(this);
    emitCheckTraps();
}

void BytecodeGenerator::emitJump(Label& target)
{
    OpJmp::emit(this, target.bind(this));
}

void BytecodeGenerator::emitCheckTraps()
{
    OpCheckTraps::emit(this);
}

void ALWAYS_INLINE BytecodeGenerator::rewind()
{
    ASSERT(m_lastInstruction.isValid());
    disablePeepholeOptimization();
    m_writer.rewind(m_lastInstruction);
}

template<typename BinOp, typename JmpOp>
bool BytecodeGenerator::fuseCompareAndJump(RegisterID* cond, Label& target, bool swapOperands)
{
    ASSERT(canDoPeepholeOptimization());
    auto binop = m_lastInstruction->as<BinOp>();
    if (cond->index() == binop.m_dst.offset() && cond->isTemporary() && !cond->refCount()) {
        rewind();

        if (swapOperands)
            std::swap(binop.m_lhs, binop.m_rhs);

        JmpOp::emit(this, binop.m_lhs, binop.m_rhs, target.bind(this));
        return true;
    }
    return false;
}

template<typename UnaryOp, typename JmpOp>
bool BytecodeGenerator::fuseTestAndJmp(RegisterID* cond, Label& target)
{
    ASSERT(canDoPeepholeOptimization());
    auto unop = m_lastInstruction->as<UnaryOp>();
    if (cond->index() == unop.m_dst.offset() && cond->isTemporary() && !cond->refCount()) {
        rewind();

        JmpOp::emit(this, unop.m_operand, target.bind(this));
        return true;
    }
    return false;
}

void BytecodeGenerator::emitJumpIfTrue(RegisterID* cond, Label& target)
{
    if (canDoPeepholeOptimization()) {
        if (m_lastOpcodeID == op_less) {
            if (fuseCompareAndJump<OpLess, OpJless>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_lesseq) {
            if (fuseCompareAndJump<OpLesseq, OpJlesseq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_greater) {
            if (fuseCompareAndJump<OpGreater, OpJgreater>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_greatereq) {
            if (fuseCompareAndJump<OpGreatereq, OpJgreatereq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_eq) {
            if (fuseCompareAndJump<OpEq, OpJeq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_stricteq) {
            if (fuseCompareAndJump<OpStricteq, OpJstricteq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_neq) {
            if (fuseCompareAndJump<OpNeq, OpJneq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_nstricteq) {
            if (fuseCompareAndJump<OpNstricteq, OpJnstricteq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_below) {
            if (fuseCompareAndJump<OpBelow, OpJbelow>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_beloweq) {
            if (fuseCompareAndJump<OpBeloweq, OpJbeloweq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_eq_null && target.isForward()) {
            if (fuseTestAndJmp<OpEqNull, OpJeqNull>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_neq_null && target.isForward()) {
            if (fuseTestAndJmp<OpNeqNull, OpJneqNull>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_is_undefined_or_null && target.isForward()) {
            if (fuseTestAndJmp<OpIsUndefinedOrNull, OpJundefinedOrNull>(cond, target))
                return;
        }
    }

    OpJtrue::emit(this, cond, target.bind(this));
}

void BytecodeGenerator::emitJumpIfFalse(RegisterID* cond, Label& target)
{
    if (canDoPeepholeOptimization()) {
        if (m_lastOpcodeID == op_less && target.isForward()) {
            if (fuseCompareAndJump<OpLess, OpJnless>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_lesseq && target.isForward()) {
            if (fuseCompareAndJump<OpLesseq, OpJnlesseq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_greater && target.isForward()) {
            if (fuseCompareAndJump<OpGreater, OpJngreater>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_greatereq && target.isForward()) {
            if (fuseCompareAndJump<OpGreatereq, OpJngreatereq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_eq && target.isForward()) {
            if (fuseCompareAndJump<OpEq, OpJneq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_stricteq && target.isForward()) {
            if (fuseCompareAndJump<OpStricteq, OpJnstricteq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_neq && target.isForward()) {
            if (fuseCompareAndJump<OpNeq, OpJeq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_nstricteq && target.isForward()) {
            if (fuseCompareAndJump<OpNstricteq, OpJstricteq>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_below && target.isForward()) {
            if (fuseCompareAndJump<OpBelow, OpJbeloweq>(cond, target, true))
                return;
        } else if (m_lastOpcodeID == op_beloweq && target.isForward()) {
            if (fuseCompareAndJump<OpBeloweq, OpJbelow>(cond, target, true))
                return;
        } else if (m_lastOpcodeID == op_not) {
            if (fuseTestAndJmp<OpNot, OpJtrue>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_eq_null && target.isForward()) {
            if (fuseTestAndJmp<OpEqNull, OpJneqNull>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_neq_null && target.isForward()) {
            if (fuseTestAndJmp<OpNeqNull, OpJeqNull>(cond, target))
                return;
        } else if (m_lastOpcodeID == op_is_undefined_or_null && target.isForward()) {
            if (fuseTestAndJmp<OpIsUndefinedOrNull, OpJnundefinedOrNull>(cond, target))
                return;
        }
    }

    OpJfalse::emit(this, cond, target.bind(this));
}

void BytecodeGenerator::emitJumpIfNotFunctionCall(RegisterID* cond, Label& target)
{
    OpJneqPtr::emit(this, cond, moveLinkTimeConstant(nullptr, LinkTimeConstant::callFunction), target.bind(this));
}

void BytecodeGenerator::emitJumpIfNotFunctionApply(RegisterID* cond, Label& target)
{
    OpJneqPtr::emit(this, cond, moveLinkTimeConstant(nullptr, LinkTimeConstant::applyFunction), target.bind(this));
}

void BytecodeGenerator::emitJumpIfNotEvalFunction(RegisterID* cond, Label& target)
{
    OpJneqPtr::emit(this, cond, moveLinkTimeConstant(nullptr, LinkTimeConstant::evalFunction), target.bind(this));
}

void BytecodeGenerator::emitJumpIfEmptyPropertyNameEnumerator(RegisterID* cond, Label& target)
{
    OpJeqPtr::emit(this, cond, moveLinkTimeConstant(nullptr, LinkTimeConstant::emptyPropertyNameEnumerator), target.bind(this));
}

void BytecodeGenerator::emitJumpIfSentinelString(RegisterID* cond, Label& target)
{
    OpJeqPtr::emit(this, cond, moveLinkTimeConstant(nullptr, LinkTimeConstant::sentinelString), target.bind(this));
}

unsigned BytecodeGenerator::emitWideJumpIfNotFunctionHasOwnProperty(RegisterID* cond, Label& target)
{
    OpJneqPtr::emit<OpcodeSize::Wide32>(this, cond, moveLinkTimeConstant(nullptr, LinkTimeConstant::hasOwnPropertyFunction), target.bind(this));
    return m_lastInstruction.offset();
}

void BytecodeGenerator::recordHasOwnPropertyInForInLoop(ForInContext& context, unsigned branchOffset, Label& genericPath)
{
    RELEASE_ASSERT(genericPath.isBound());
    RELEASE_ASSERT(!genericPath.isForward());
    context.addHasOwnPropertyJump(branchOffset, genericPath.location());
}

bool BytecodeGenerator::hasConstant(const Identifier& ident) const
{
    UniquedStringImpl* rep = ident.impl();
    return m_identifierMap.contains(rep);
}

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

    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 = addConstantIndex();
        m_codeBlock->addConstant(JSValue());
        m_emptyValueRegister = &m_constantPoolRegisters[index];
    }

    return m_emptyValueRegister;
}

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

    int index = m_nextConstantOffset;

    if (sourceCodeRepresentation == SourceCodeRepresentation::Double && v.isInt32())
        v = jsDoubleNumber(v.asNumber());
    EncodedJSValueWithRepresentation valueMapKey { JSValue::encode(v), sourceCodeRepresentation };
    JSValueMap::AddResult result = m_jsValueMap.add(valueMapKey, m_nextConstantOffset);
    if (result.isNewEntry) {
        addConstantIndex();
        m_codeBlock->addConstant(v, sourceCodeRepresentation);
    } else
        index = result.iterator->value;
    return &m_constantPoolRegisters[index];
}

RegisterID* BytecodeGenerator::moveLinkTimeConstant(RegisterID* dst, LinkTimeConstant type)
{
    RegisterID* constant = m_linkTimeConstantRegisters.ensure(type, [&] {
        int index = addConstantIndex();
        m_codeBlock->addConstant(type);
        return &m_constantPoolRegisters[index];
    }).iterator->value;
    if (!dst)
        return constant;

    return move(dst, constant);
}

RegisterID* BytecodeGenerator::moveEmptyValue(RegisterID* dst)
{
    RefPtr<RegisterID> emptyValue = addConstantEmptyValue();

    return move(dst, emptyValue.get());
}

RegisterID* BytecodeGenerator::emitMove(RegisterID* dst, RegisterID* src)
{
    m_staticPropertyAnalyzer.mov(dst, src);
    if (canDoPeepholeOptimization() && m_lastInstruction->is<OpMov>()) {
        auto op = m_lastInstruction->as<OpMov>();
        if (op.m_dst == dst->virtualRegister())
            rewind();
    }
    OpMov::emit(this, dst, src);

    return dst;
}

// We treat `typeof x > "u"` as `typeof x === "undefined`
template<BytecodeGenerator::IsNotTypeofUndefined isNotTypeofUndefined>
bool BytecodeGenerator::tryEmitTypeofIsUndefinedForStringComparison(RegisterID* dst, RegisterID* src1, RegisterID* src2)
{
    if (!canDoPeepholeOptimization() || !m_lastInstruction->is<OpTypeof>())
        return false;

    auto op = m_lastInstruction->as<OpTypeof>();
    if (src1->virtualRegister() != op.m_dst
        || !src1->isTemporary()
        || !src2->virtualRegister().isConstant()
        || !m_codeBlock->constantRegister(src2->virtualRegister()).get().isString())
        return false;

    String value = asString(m_codeBlock->constantRegister(src2->virtualRegister()).get())->tryGetValue();
    if (value != "u"_s)
        return false;

    rewind();
    if constexpr (isNotTypeofUndefined == IsNotTypeofUndefined::Yes) {
        RefPtr<RegisterID> temp = newTemporary();
        OpTypeofIsUndefined::emit(this, temp.get(), op.m_value);
        emitUnaryOp<OpNot>(dst, temp.get());
    } else
        OpTypeofIsUndefined::emit(this, dst, op.m_value);
    return true;
}

RegisterID* BytecodeGenerator::emitUnaryOp(OpcodeID opcodeID, RegisterID* dst, RegisterID* src, ResultType type)
{
    switch (opcodeID) {
    case op_not:
        emitUnaryOp<OpNot>(dst, src);
        break;
    case op_negate:
        OpNegate::emit(this, dst, src, m_codeBlock->addUnaryArithProfile(), type);
        break;
    case op_bitnot:
        OpBitnot::emit(this, dst, src, m_codeBlock->addUnaryArithProfile());
        break;
    case op_to_number:
        OpToNumber::emit(this, dst, src, m_codeBlock->addUnaryArithProfile());
        break;
    case op_to_numeric:
        OpToNumeric::emit(this, dst, src, m_codeBlock->addUnaryArithProfile());
        break;
    default:
        ASSERT_NOT_REACHED();
    }
    return dst;
}

RegisterID* BytecodeGenerator::emitBinaryOp(OpcodeID opcodeID, RegisterID* dst, RegisterID* src1, RegisterID* src2, OperandTypes types)
{
    switch (opcodeID) {
    case op_eq:
        return emitBinaryOp<OpEq>(dst, src1, src2, types);
    case op_neq:
        return emitBinaryOp<OpNeq>(dst, src1, src2, types);
    case op_stricteq:
        return emitBinaryOp<OpStricteq>(dst, src1, src2, types);
    case op_nstricteq:
        return emitBinaryOp<OpNstricteq>(dst, src1, src2, types);
    case op_less: {
        if (tryEmitTypeofIsUndefinedForStringComparison<BytecodeGenerator::IsNotTypeofUndefined::Yes>(dst, src1, src2))
            return dst;
        return emitBinaryOp<OpLess>(dst, src1, src2, types);
    }
    case op_lesseq:
        return emitBinaryOp<OpLesseq>(dst, src1, src2, types);
    case op_greater: {
        if (tryEmitTypeofIsUndefinedForStringComparison<BytecodeGenerator::IsNotTypeofUndefined::No>(dst, src1, src2))
            return dst;
        return emitBinaryOp<OpGreater>(dst, src1, src2, types);
    }
    case op_greatereq:
        return emitBinaryOp<OpGreatereq>(dst, src1, src2, types);
    case op_below:
        return emitBinaryOp<OpBelow>(dst, src1, src2, types);
    case op_beloweq:
        return emitBinaryOp<OpBeloweq>(dst, src1, src2, types);
    case op_mod:
        return emitBinaryOp<OpMod>(dst, src1, src2, types);
    case op_pow:
        return emitBinaryOp<OpPow>(dst, src1, src2, types);
    case op_lshift:
        return emitBinaryOp<OpLshift>(dst, src1, src2, types);
    case op_rshift:
        return emitBinaryOp<OpRshift>(dst, src1, src2, types);
    case op_urshift:
        return emitBinaryOp<OpUrshift>(dst, src1, src2, types);
    case op_add: {
        auto isConstantEmptyString = [&](RegisterID* src) {
            if (!src->virtualRegister().isConstant())
                return false;
            if (!m_codeBlock->constantRegister(src->virtualRegister()).get().isString())
                return false;
            String value = asString(m_codeBlock->constantRegister(src->virtualRegister()).get())->tryGetValue();
            return value.isEmpty();
        };

        if (isConstantEmptyString(src1)) {
            emitToPrimitive(dst, src2);
            return emitToString(dst, dst);
        }

        if (isConstantEmptyString(src2)) {
            emitToPrimitive(dst, src1);
            return emitToString(dst, dst);
        }

        return emitBinaryOp<OpAdd>(dst, src1, src2, types);
    }
    case op_mul:
        return emitBinaryOp<OpMul>(dst, src1, src2, types);
    case op_div:
        return emitBinaryOp<OpDiv>(dst, src1, src2, types);
    case op_sub:
        return emitBinaryOp<OpSub>(dst, src1, src2, types);
    case op_bitand:
        return emitBinaryOp<OpBitand>(dst, src1, src2, types);
    case op_bitxor:
        return emitBinaryOp<OpBitxor>(dst, src1, src2, types);
    case op_bitor:
        return emitBinaryOp<OpBitor>(dst, src1, src2, types);
    default:
        ASSERT_NOT_REACHED();
        return nullptr;
    }
}

RegisterID* BytecodeGenerator::emitToObject(RegisterID* dst, RegisterID* src, const Identifier& message)
{
    OpToObject::emit(this, dst, src, addConstant(message), nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitToNumber(RegisterID* dst, RegisterID* src)
{
    OpToNumber::emit(this, dst, src, m_codeBlock->addUnaryArithProfile());
    return dst;
}

RegisterID* BytecodeGenerator::emitToNumeric(RegisterID* dst, RegisterID* src)
{
    OpToNumeric::emit(this, dst, src, m_codeBlock->addUnaryArithProfile());
    return dst;
}

RegisterID* BytecodeGenerator::emitToString(RegisterID* dst, RegisterID* src)
{
    return emitUnaryOp<OpToString>(dst, src);
}

RegisterID* BytecodeGenerator::emitTypeOf(RegisterID* dst, RegisterID* src)
{
    return emitUnaryOp<OpTypeof>(dst, src);
}

RegisterID* BytecodeGenerator::emitInc(RegisterID* srcDst)
{
    OpInc::emit(this, srcDst, m_codeBlock->addUnaryArithProfile());
    return srcDst;
}

RegisterID* BytecodeGenerator::emitDec(RegisterID* srcDst)
{
    OpDec::emit(this, srcDst, m_codeBlock->addUnaryArithProfile());
    return srcDst;
}

bool BytecodeGenerator::emitEqualityOpImpl(RegisterID* dst, RegisterID* src1, RegisterID* src2)
{
    if (!canDoPeepholeOptimization())
        return false;

    if (m_lastInstruction->is<OpTypeof>()) {
        auto op = m_lastInstruction->as<OpTypeof>();
        if (src1->virtualRegister() == op.m_dst
            && src1->isTemporary()
            && src2->virtualRegister().isConstant()
            && m_codeBlock->constantRegister(src2->virtualRegister()).get().isString()) {
            String value = asString(m_codeBlock->constantRegister(src2->virtualRegister()).get())->tryGetValue();
            if (value == "undefined"_s) {
                rewind();
                OpTypeofIsUndefined::emit(this, dst, op.m_value);
                return true;
            }
            if (value == "boolean"_s) {
                rewind();
                OpIsBoolean::emit(this, dst, op.m_value);
                return true;
            }
            if (value == "number"_s) {
                rewind();
                OpIsNumber::emit(this, dst, op.m_value);
                return true;
            }
            if (value == "string"_s) {
                rewind();
                OpIsCellWithType::emit(this, dst, op.m_value, StringType);
                return true;
            }
            if (value == "symbol"_s) {
                rewind();
                OpIsCellWithType::emit(this, dst, op.m_value, SymbolType);
                return true;
            }
            if (value == "bigint"_s) {
                rewind();
#if USE(BIGINT32)
                OpIsBigInt::emit(this, dst, op.m_value);
#else
                OpIsCellWithType::emit(this, dst, op.m_value, HeapBigIntType);
#endif
                return true;
            }
            if (value == "object"_s) {
                rewind();
                OpTypeofIsObject::emit(this, dst, op.m_value);
                return true;
            }
            if (value == "function"_s) {
                rewind();
                OpTypeofIsFunction::emit(this, dst, op.m_value);
                return true;
            }
        }
    }

    return false;
}

void BytecodeGenerator::emitTypeProfilerExpressionInfo(const JSTextPosition& startDivot, const JSTextPosition& endDivot)
{
    ASSERT(shouldEmitTypeProfilerHooks());

    unsigned start = startDivot.offset; // Ranges are inclusive of their endpoints, AND 0 indexed.
    unsigned end = endDivot.offset - 1; // End Ranges already go one past the inclusive range, so subtract 1.
    unsigned instructionOffset = instructions().size() - 1;
    m_codeBlock->addTypeProfilerExpressionInfo(instructionOffset, start, end);
}

void BytecodeGenerator::emitProfileType(RegisterID* registerToProfile, ProfileTypeBytecodeFlag flag)
{
    if (!shouldEmitTypeProfilerHooks())
        return;

    if (!registerToProfile)
        return;

    OpProfileType::emit(this, registerToProfile, { }, flag, { }, resolveType());

    // Don't emit expression info for this version of profile type. This generally means
    // we're profiling information for something that isn't in the actual text of a JavaScript
    // program. For example, implicit return undefined from a function call.
}

void BytecodeGenerator::emitProfileType(RegisterID* registerToProfile, const JSTextPosition& startDivot, const JSTextPosition& endDivot)
{
    emitProfileType(registerToProfile, ProfileTypeBytecodeDoesNotHaveGlobalID, startDivot, endDivot);
}

void BytecodeGenerator::emitProfileType(RegisterID* registerToProfile, ProfileTypeBytecodeFlag flag, const JSTextPosition& startDivot, const JSTextPosition& endDivot)
{
    if (!shouldEmitTypeProfilerHooks())
        return;

    if (!registerToProfile)
        return;

    OpProfileType::emit(this, registerToProfile, { },  flag, { }, resolveType());
    emitTypeProfilerExpressionInfo(startDivot, endDivot);
}

void BytecodeGenerator::emitProfileType(RegisterID* registerToProfile, const Variable& var, const JSTextPosition& startDivot, const JSTextPosition& endDivot)
{
    if (!shouldEmitTypeProfilerHooks())
        return;

    if (!registerToProfile)
        return;

    ProfileTypeBytecodeFlag flag;
    SymbolTableOrScopeDepth symbolTableOrScopeDepth;
    if (var.local() || var.offset().isScope()) {
        flag = ProfileTypeBytecodeLocallyResolved;
        ASSERT(var.symbolTableConstantIndex());
        symbolTableOrScopeDepth = SymbolTableOrScopeDepth::symbolTable(VirtualRegister { var.symbolTableConstantIndex() });
    } else {
        flag = ProfileTypeBytecodeClosureVar;
        symbolTableOrScopeDepth = SymbolTableOrScopeDepth::scopeDepth(localScopeDepth());
    }

    OpProfileType::emit(this, registerToProfile, symbolTableOrScopeDepth, flag, addConstant(var.ident()), resolveType());
    emitTypeProfilerExpressionInfo(startDivot, endDivot);
}

void BytecodeGenerator::emitProfileControlFlow(int textOffset)
{
    if (shouldEmitControlFlowProfilerHooks()) {
        RELEASE_ASSERT(textOffset >= 0);

        OpProfileControlFlow::emit(this, textOffset);
        m_codeBlock->addOpProfileControlFlowBytecodeOffset(m_lastInstruction.offset());
    }
}

unsigned BytecodeGenerator::addConstantIndex()
{
    unsigned index = m_nextConstantOffset;
    m_constantPoolRegisters.append(FirstConstantRegisterIndex + m_nextConstantOffset);
    ++m_nextConstantOffset;
    return index;
}

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

RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, const Identifier& identifier)
{
    ASSERT(!identifier.isSymbol());
    JSString*& stringInMap = m_stringMap.add(identifier.impl(), nullptr).iterator->value;
    if (!stringInMap)
        stringInMap = jsOwnedString(vm(), identifier.string());

    return emitLoad(dst, JSValue(stringInMap));
}

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

RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, IdentifierSet&& set)
{
    unsigned setIndex = m_codeBlock->addSetConstant(WTF::move(set));
    return emitLoad(dst, jsNumber(setIndex));
}

template<typename LookUpVarKindFunctor>
bool BytecodeGenerator::instantiateLexicalVariables(const VariableEnvironment& lexicalVariables, ScopeType scopeType, SymbolTable* symbolTable, ScopeRegisterType scopeRegisterType, LookUpVarKindFunctor lookUpVarKind)
{
    bool hasCapturedVariables = false;
    {
        bool hasPrivateNames = lexicalVariables.privateNamesSize();
        // We need to ensure that @privateClassBrand and @privateBrand offsets are 0 and 1 respectively.
        // To ensure that, we first define them, and later, we filter them out from lexicalVariables.
        if (scopeType == ScopeType::ClassScope) {
            if (hasPrivateNames) {
                hasCapturedVariables = true;
                VarOffset privateClassBrandOffset = VarOffset(symbolTable->takeNextScopeOffset(NoLockingNecessary));
                ASSERT(privateClassBrandOffset.rawOffset() == PrivateNameEntry::privateClassBrandOffset);
                symbolTable->add(NoLockingNecessary, propertyNames().builtinNames().privateClassBrandPrivateName().impl(), SymbolTableEntry { privateClassBrandOffset, static_cast<unsigned>(PropertyAttribute::ReadOnly) });

                VarOffset privateBrandOffset = VarOffset(symbolTable->takeNextScopeOffset(NoLockingNecessary));
                ASSERT(privateBrandOffset.rawOffset() == PrivateNameEntry::privateBrandOffset);
                symbolTable->add(NoLockingNecessary, propertyNames().builtinNames().privateBrandPrivateName().impl(), SymbolTableEntry { privateBrandOffset, static_cast<unsigned>(PropertyAttribute::ReadOnly) });
            }
        }

        for (auto& entry : lexicalVariables) {
            ASSERT(entry.value.isLet() || entry.value.isConst() || entry.value.isFunction());
            ASSERT(!entry.value.isVar());

            auto* key = entry.key.get();
            if (scopeType == ScopeType::ClassScope) {
                if (hasPrivateNames) {
                    if (key == propertyNames().builtinNames().privateClassBrandPrivateName()) {
                        ASSERT(entry.value.isConst());
                        continue;
                    }
                    if (key == propertyNames().builtinNames().privateBrandPrivateName()) {
                        ASSERT(entry.value.isConst());
                        continue;
                    }
                } else {
                    ASSERT(key != propertyNames().builtinNames().privateClassBrandPrivateName());
                    ASSERT(key != propertyNames().builtinNames().privateBrandPrivateName());
                }
            }

#if ASSERT_ENABLED
            SymbolTableEntry::Fast symbolTableEntry = symbolTable->get(NoLockingNecessary, key);
            ASSERT(symbolTableEntry.isNull());
#endif

            // Imported bindings which are not the namespace bindings are not allocated
            // in the module environment as usual variables' way.
            // And since these types of the variables only seen in the module environment,
            // other lexical environment need not to take care this.
            if (entry.value.isImported() && !entry.value.isImportedNamespace())
                continue;

            VarKind varKind = lookUpVarKind(key, entry.value);
            VarOffset varOffset;
            if (varKind == VarKind::Scope) {
                varOffset = VarOffset(symbolTable->takeNextScopeOffset(NoLockingNecessary));
                hasCapturedVariables = true;
            } else {
                ASSERT(varKind == VarKind::Stack);
                RegisterID* local;
                if (scopeRegisterType == ScopeRegisterType::Block) {
                    local = newBlockScopeVariable();
                    local->ref();
                } else
                    local = addVar();
                varOffset = VarOffset(local->virtualRegister());
            }

            SymbolTableEntry newEntry(varOffset, static_cast<unsigned>(entry.value.isConst() ? PropertyAttribute::ReadOnly : PropertyAttribute::None));
            symbolTable->add(NoLockingNecessary, key, WTF::move(newEntry));

            // FIXME: only do this if there is an eval() within a nested scope --- otherwise it isn't needed.
            // https://bugs.webkit.org/show_bug.cgi?id=206663
            
            const PrivateNameEnvironment* privateEnvironment = lexicalVariables.privateNameEnvironment();
            if (!privateEnvironment)
                continue;

            auto findResult = privateEnvironment->find(key);

            if (findResult == privateEnvironment->end())
                continue;

            symbolTable->addPrivateName(findResult->key.get(), findResult->value);
        }
    }
    return hasCapturedVariables;
}

void BytecodeGenerator::emitPrefillStackTDZVariables(const VariableEnvironment& lexicalVariables, SymbolTable* symbolTable)
{
    // Prefill stack variables with the TDZ empty value.
    // Scope variables will be initialized to the TDZ empty value when JSLexicalEnvironment is allocated.
    for (auto& entry : lexicalVariables) {
        // Imported bindings which are not the namespace bindings are not allocated
        // in the module environment as usual variables' way.
        // And since these types of the variables only seen in the module environment,
        // other lexical environment need not to take care this.
        if (entry.value.isImported() && !entry.value.isImportedNamespace())
            continue;

        if (entry.value.isFunction())
            continue;

        SymbolTableEntry::Fast symbolTableEntry = symbolTable->get(NoLockingNecessary, entry.key.get());
        ASSERT(!symbolTableEntry.isNull());
        VarOffset offset = symbolTableEntry.varOffset();
        if (offset.isScope())
            continue;

        ASSERT(offset.isStack());
        moveEmptyValue(&registerFor(offset.stackOffset()));
    }
}

void BytecodeGenerator::pushLexicalScope(VariableEnvironmentNode* node, ScopeType scopeType, TDZCheckOptimization tdzCheckOptimization, NestedScopeType nestedScopeType, RegisterID** constantSymbolTableResult, bool shouldInitializeBlockScopedFunctions)
{
    VariableEnvironment& environment = node->lexicalVariables();
    RegisterID* constantSymbolTableResultTemp = nullptr;
    pushLexicalScopeInternal(environment, tdzCheckOptimization, nestedScopeType, &constantSymbolTableResultTemp, TDZRequirement::UnderTDZ, scopeType, ScopeRegisterType::Block);

    if (shouldInitializeBlockScopedFunctions)
        initializeBlockScopedFunctions(environment, node->functionStack(), constantSymbolTableResultTemp);

    if (constantSymbolTableResult && constantSymbolTableResultTemp)
        *constantSymbolTableResult = constantSymbolTableResultTemp;
}

void BytecodeGenerator::pushClassHeadLexicalScope(VariableEnvironment& environment)
{
    pushLexicalScopeInternal(environment, TDZCheckOptimization::Optimize, NestedScopeType::IsNested, nullptr, TDZRequirement::UnderTDZ, ScopeType::LetConstScope, ScopeRegisterType::Block);
}

void BytecodeGenerator::popClassHeadLexicalScope(VariableEnvironment& environment)
{
    popLexicalScopeInternal(environment);
}

void BytecodeGenerator::pushLexicalScopeInternal(VariableEnvironment& environment, TDZCheckOptimization tdzCheckOptimization, NestedScopeType nestedScopeType,
    RegisterID** constantSymbolTableResult, TDZRequirement tdzRequirement, ScopeType scopeType, ScopeRegisterType scopeRegisterType)
{
    if (!environment.size())
        return;

    if (shouldEmitDebugHooks())
        environment.markAllVariablesAsCaptured();

    SymbolTable* symbolTable = SymbolTable::create(m_vm);
    switch (scopeType) {
    case ScopeType::CatchScope:
        symbolTable->setScopeType(SymbolTable::ScopeType::CatchScope);
        break;
    case ScopeType::CatchScopeWithSimpleParameter:
        symbolTable->setScopeType(SymbolTable::ScopeType::CatchScopeWithSimpleParameter);
        break;
    case ScopeType::LetConstScope:
    case ScopeType::ClassScope:
        symbolTable->setScopeType(SymbolTable::ScopeType::LexicalScope);
        break;
    case ScopeType::FunctionNameScope:
        symbolTable->setScopeType(SymbolTable::ScopeType::FunctionNameScope);
        break;
    }

    if (nestedScopeType == NestedScopeType::IsNested)
        symbolTable->markIsNestedLexicalScope();

    auto lookUpVarKind = [] (UniquedStringImpl*, const VariableEnvironmentEntry& entry) -> VarKind {
        return entry.isCaptured() ? VarKind::Scope : VarKind::Stack;
    };

    bool hasCapturedVariables = instantiateLexicalVariables(environment, scopeType, symbolTable, scopeRegisterType, lookUpVarKind);

    RegisterID* newScope = nullptr;
    RegisterID* constantSymbolTable = nullptr;
    int symbolTableConstantIndex = 0;
    if (shouldEmitTypeProfilerHooks()) {
        constantSymbolTable = addConstantValue(symbolTable);
        symbolTableConstantIndex = constantSymbolTable->index();
    }
    if (hasCapturedVariables) {
        if (scopeRegisterType == ScopeRegisterType::Block) {
            newScope = newBlockScopeVariable();
            newScope->ref();
        } else
            newScope = addVar();
        if (!constantSymbolTable) {
            ASSERT(!shouldEmitTypeProfilerHooks());
            constantSymbolTable = addConstantValue(symbolTable->cloneScopePart(m_vm, SymbolTable::PropagateCloneInvalidationToOriginal::No));
            symbolTableConstantIndex = constantSymbolTable->index();
        }
        if (constantSymbolTableResult)
            *constantSymbolTableResult = constantSymbolTable;

        OpCreateLexicalEnvironment::emit(this, newScope, scopeRegister(), VirtualRegister { symbolTableConstantIndex }, addConstantValue(tdzRequirement == TDZRequirement::UnderTDZ ? jsTDZValue() : jsUndefined()));

        move(scopeRegister(), newScope);

        pushLocalControlFlowScope();
    }

    bool isWithScope = false;
    m_lexicalScopeStack.append({ symbolTable, newScope, isWithScope, symbolTableConstantIndex });
    pushTDZVariables(environment, tdzCheckOptimization, tdzRequirement);

    if (tdzRequirement == TDZRequirement::UnderTDZ)
        emitPrefillStackTDZVariables(environment, symbolTable);
}

void BytecodeGenerator::initializeBlockScopedFunctions(VariableEnvironment& environment, FunctionStack& functionStack, RegisterID* constantSymbolTable)
{
    /*
     * We must transform block scoped function declarations in strict mode like so:
     *
     * function foo() {
     *     if (c) {
     *           function foo() { ... }
     *           if (bar) { ... }
     *           else { ... }
     *           function baz() { ... }
     *     }
     * }
     *
     * to:
     *
     * function foo() {
     *     if (c) {
     *         let foo = function foo() { ... }
     *         let baz = function baz() { ... }
     *         if (bar) { ... }
     *         else { ... }
     *     }
     * }
     * 
     * But without the TDZ checks.
    */

    if (!environment.size()) {
        RELEASE_ASSERT(!functionStack.size());
        return;
    }

    if (!functionStack.size())
        return;

    SymbolTable* symbolTable = m_lexicalScopeStack.last().m_symbolTable;
    RegisterID* scope = m_lexicalScopeStack.last().m_scope;
    RefPtr<RegisterID> temp = newTemporary();
    int symbolTableIndex = constantSymbolTable ? constantSymbolTable->index() : 0;
    for (FunctionMetadataNode* function : functionStack) {
        const Identifier& name = function->ident();
        auto iter = environment.find(name.impl());
        RELEASE_ASSERT(iter != environment.end());
        RELEASE_ASSERT(iter->value.isFunction());
        // We purposefully don't hold the symbol table lock around this loop because emitNewFunctionExpressionCommon may GC.
        SymbolTableEntry::Fast entry = symbolTable->get(NoLockingNecessary, name.impl());
        RELEASE_ASSERT(!entry.isNull());
        emitNewFunctionExpressionCommon(temp.get(), function);
        bool isLexicallyScoped = true;
        emitPutToScope(scope, variableForLocalEntry(name, entry, symbolTableIndex, isLexicallyScoped), temp.get(), DoNotThrowIfNotFound, InitializationMode::Initialization);
    }
}

void BytecodeGenerator::hoistSloppyModeFunctionIfNecessary(FunctionMetadataNode* metadata)
{
    if (metadata->isSloppyModeHoistedFunction()) {
        const Identifier& functionName = metadata->ident();

        if (m_generatorOrAsyncWrapperFunctionParameterNames && m_generatorOrAsyncWrapperFunctionParameterNames->contains(functionName))
            return;

        Variable currentFunctionVariable = variable(functionName);
        RefPtr<RegisterID> currentValue;
        if (RegisterID* local = currentFunctionVariable.local())
            currentValue = local;
        else {
            RefPtr<RegisterID> scope = emitResolveScope(nullptr, currentFunctionVariable);
            currentValue = emitGetFromScope(newTemporary(), scope.get(), currentFunctionVariable, DoNotThrowIfNotFound);
        }

        switch (codeType()) {
        case FunctionCode: {
            ASSERT(m_varScopeLexicalScopeStackIndex);
            ASSERT(*m_varScopeLexicalScopeStackIndex < m_lexicalScopeStack.size());
            LexicalScopeStackEntry varScope = m_lexicalScopeStack[*m_varScopeLexicalScopeStackIndex];
            SymbolTable* varSymbolTable = varScope.m_symbolTable;
            ASSERT(varSymbolTable->scopeType() == SymbolTable::ScopeType::VarScope);
            SymbolTableEntry::Fast entry = varSymbolTable->get(NoLockingNecessary, functionName.impl());
            if (functionName == propertyNames().arguments && entry.isNull()) {
                // "arguments" might be put in the parameter scope when we have a non-simple
                // parameter list since "arguments" is visible to expressions inside the
                // parameter evaluation list.
                // e.g:
                // function foo(x = arguments) { { function arguments() { } } }
                RELEASE_ASSERT(*m_varScopeLexicalScopeStackIndex > 0);
                varScope = m_lexicalScopeStack[*m_varScopeLexicalScopeStackIndex - 1];
                SymbolTable* parameterSymbolTable = varScope.m_symbolTable;
                entry = parameterSymbolTable->get(NoLockingNecessary, functionName.impl());
            }
            RELEASE_ASSERT(!entry.isNull());
            bool isLexicallyScoped = false;
            emitPutToScope(varScope.m_scope, variableForLocalEntry(functionName, entry, varScope.m_symbolTableConstantIndex, isLexicallyScoped), currentValue.get(), DoNotThrowIfNotFound, InitializationMode::NotInitialization);
            break;
        }
        case GlobalCode:
        case EvalCode: {
            RefPtr<RegisterID> scopeId = emitResolveScopeForHoistingFuncDeclInEval(nullptr, functionName);
            Ref<Label> isNotVarScopeLabel = newLabel();
            emitJumpIfTrue(emitIsUndefined(newTemporary(), scopeId.get()), isNotVarScopeLabel.get());
            // Put to outer scope
            emitPutToScopeDynamic(scopeId.get(), functionName, currentValue.get(), DoNotThrowIfNotFound, InitializationMode::NotInitialization);
            emitLabel(isNotVarScopeLabel.get());
            break;
        }
        case ModuleCode:
            RELEASE_ASSERT_NOT_REACHED();
        }
    }
}

RegisterID* BytecodeGenerator::emitResolveScopeForHoistingFuncDeclInEval(RegisterID* dst, const Identifier& property)
{
    RefPtr<RegisterID> result = finalDestination(dst);
    RefPtr<RegisterID> scope = newTemporary();
    if (m_topLevelScopeRegister)
        move(scope.get(), m_topLevelScopeRegister);
    else
        OpGetScope::emit(this, scope.get());
    OpResolveScopeForHoistingFuncDeclInEval::emit(this, kill(result.get()), scope.get(), addConstant(property));
    return result.unsafeGet();
}

void BytecodeGenerator::popLexicalScope(VariableEnvironmentNode* node)
{
    VariableEnvironment& environment = node->lexicalVariables();
    popLexicalScopeInternal(environment);
}

void BytecodeGenerator::popLexicalScopeInternal(VariableEnvironment& environment)
{
    // NOTE: This function only makes sense for scopes that aren't ScopeRegisterType::Var (only function name scope right now is ScopeRegisterType::Var).
    // This doesn't make sense for ScopeRegisterType::Var because we deref RegisterIDs here.
    if (!environment.size())
        return;

    if (shouldEmitDebugHooks())
        environment.markAllVariablesAsCaptured();

    auto stackEntry = m_lexicalScopeStack.takeLast();
    SymbolTable* symbolTable = stackEntry.m_symbolTable;
    bool hasCapturedVariables = false;
    for (auto& entry : environment) {
        if (entry.value.isCaptured()) {
            hasCapturedVariables = true;
            continue;
        }
        SymbolTableEntry::Fast symbolTableEntry = symbolTable->get(NoLockingNecessary, entry.key.get());
        ASSERT(!symbolTableEntry.isNull());
        VarOffset offset = symbolTableEntry.varOffset();
        ASSERT(offset.isStack());
        RegisterID* local = &registerFor(offset.stackOffset());
        local->deref();
    }

    if (hasCapturedVariables) {
        RELEASE_ASSERT(stackEntry.m_scope);
        emitGetParentScope(scopeRegister(), stackEntry.m_scope);
        popLocalControlFlowScope();
        stackEntry.m_scope->deref();
    }

    m_TDZStack.removeLast();
}

void BytecodeGenerator::prepareLexicalScopeForNextForLoopIteration(VariableEnvironmentNode* node, RegisterID* loopSymbolTable)
{
    VariableEnvironment& environment = node->lexicalVariables();
    if (!environment.size())
        return;
    if (shouldEmitDebugHooks())
        environment.markAllVariablesAsCaptured();
    if (!environment.hasCapturedVariables())
        return;

    RELEASE_ASSERT(loopSymbolTable);

    // This function needs to do setup for a for loop's activation if any of
    // the for loop's lexically declared variables are captured (that is, variables
    // declared in the loop header, not the loop body). This function needs to
    // make a copy of the current activation and copy the values from the previous
    // activation into the new activation because each iteration of a for loop
    // gets a new activation.

    auto stackEntry = m_lexicalScopeStack.last();
    SymbolTable* symbolTable = stackEntry.m_symbolTable;
    RegisterID* loopScope = stackEntry.m_scope;
    ASSERT(symbolTable->scopeSize());
    ASSERT(loopScope);

    struct SymbolTableNoLocks {
        auto NODELETE begin() const { return symbolTable->begin(NoLockingNecessary); }
        auto NODELETE end() const { return symbolTable->end(NoLockingNecessary); }
        size_t NODELETE size() const { return symbolTable->scopeSize(); }
        SymbolTable* symbolTable;
    } symbolTableWithoutLocks { symbolTable };

    auto activationValuesToCopyOver = WTF::compactMap(symbolTableWithoutLocks, [&](auto& pair) -> std::optional<std::pair<RegisterID*, Identifier>> {
        if (!pair.value.varOffset().isScope())
            return std::nullopt;

        RefPtr ident = pair.key;
        auto identifier = Identifier::fromUid(m_vm, ident.get());

        auto* transitionValue = newBlockScopeVariable();
        transitionValue->ref();
        emitGetFromScope(transitionValue, loopScope, variableForLocalEntry(identifier, pair.value, loopSymbolTable->index(), true), DoNotThrowIfNotFound);
        return std::make_pair(transitionValue, identifier);
    });

    // We need this dynamic behavior of the executing code to ensure
    // each loop iteration has a new activation object. (It's pretty ugly).
    // Also, this new activation needs to be assigned to the same register
    // as the previous scope because the loop body is compiled under
    // the assumption that the scope's register index is constant even
    // though the value in that register will change on each loop iteration.
    emitGetParentScope(scopeRegister(), loopScope);

    OpCreateLexicalEnvironment::emit(this, loopScope, scopeRegister(), loopSymbolTable, addConstantValue(jsTDZValue()));

    move(scopeRegister(), loopScope);

    {
        for (const auto& pair : activationValuesToCopyOver) {
            const Identifier& identifier = pair.second;
            SymbolTableEntry::Fast entry = symbolTable->get(NoLockingNecessary, identifier.impl());
            RELEASE_ASSERT(!entry.isNull());
            RegisterID* transitionValue = pair.first;
            emitPutToScope(loopScope, variableForLocalEntry(identifier, entry, loopSymbolTable->index(), true), transitionValue, DoNotThrowIfNotFound, InitializationMode::NotInitialization);
            transitionValue->deref();
        }
    }
}

Variable BytecodeGenerator::variable(const Identifier& property, ThisResolutionType thisResolutionType)
{
    if (property == propertyNames().builtinNames().thisPrivateName() && thisResolutionType == ThisResolutionType::Local)
        return Variable(property, VarOffset(thisRegister()->virtualRegister()), thisRegister(), static_cast<unsigned>(PropertyAttribute::ReadOnly), Variable::SpecialVariable, 0, false);
    
    // We can optimize lookups if the lexical variable is found before a "with" or "catch"
    // scope because we're guaranteed static resolution. If we have to pass through
    // a "with" or "catch" scope we loose this guarantee.
    // We can't optimize cases like this:
    // {
    //     let x = ...;
    //     with (o) {
    //         doSomethingWith(x);
    //     }
    // }
    // Because we can't gaurantee static resolution on x.
    // But, in this case, we are guaranteed static resolution:
    // {
    //     let x = ...;
    //     with (o) {
    //         let x = ...;
    //         doSomethingWith(x);
    //     }
    // }
    for (unsigned i = m_lexicalScopeStack.size(); i--; ) {
        auto& stackEntry = m_lexicalScopeStack[i];
        if (stackEntry.m_isWithScope)
            return Variable(property);
        SymbolTable* symbolTable = stackEntry.m_symbolTable;
        SymbolTableEntry::Fast symbolTableEntry = symbolTable->get(NoLockingNecessary, property.impl());
        if (symbolTableEntry.isNull())
            continue;
        bool resultIsCallee = false;
        if (symbolTable->scopeType() == SymbolTable::ScopeType::FunctionNameScope) {
            if (m_usesSloppyEval) {
                // We don't know if an eval has introduced a "var" named the same thing as the function name scope variable name.
                // We resort to dynamic lookup to answer this question.
                Variable result = Variable(property);
                return result;
            }
            resultIsCallee = true;
        }
        Variable result = variableForLocalEntry(property, symbolTableEntry, stackEntry.m_symbolTableConstantIndex, symbolTable->scopeType() == SymbolTable::ScopeType::LexicalScope);
        if (resultIsCallee)
            result.setIsReadOnly();
        return result;
    }
    
    return Variable(property);
}

Variable BytecodeGenerator::variableForLocalEntry(
    const Identifier& property, const SymbolTableEntry::Fast& entry, int symbolTableConstantIndex, bool isLexicallyScoped)
{
    VarOffset offset = entry.varOffset();
    
    RegisterID* local;
    if (offset.isStack())
        local = &registerFor(offset.stackOffset());
    else
        local = nullptr;
    
    return Variable(property, offset, local, entry.getAttributes(), Variable::NormalVariable, symbolTableConstantIndex, isLexicallyScoped);
}

void BytecodeGenerator::createVariable(
    const Identifier& property, VarKind varKind, SymbolTable* symbolTable, ExistingVariableMode existingVariableMode)
{
    ASSERT(property != propertyNames().builtinNames().thisPrivateName());
    SymbolTableEntry::Fast entry = symbolTable->get(NoLockingNecessary, property.impl());
    
    if (!entry.isNull()) {
        if (existingVariableMode == IgnoreExisting)
            return;
        
        // Do some checks to ensure that the variable we're being asked to create is sufficiently
        // compatible with the one we have already created.

        VarOffset offset = entry.varOffset();
        
        // We can't change our minds about whether it's captured.
        if (offset.kind() != varKind) {
            dataLog(
                "Trying to add variable called ", property, " as ", varKind,
                " but it was already added as ", offset, ".\n");
            RELEASE_ASSERT_NOT_REACHED();
        }

        return;
    }
    
    VarOffset varOffset;
    if (varKind == VarKind::Scope)
        varOffset = VarOffset(symbolTable->takeNextScopeOffset(NoLockingNecessary));
    else {
        ASSERT(varKind == VarKind::Stack);
        varOffset = VarOffset(virtualRegisterForLocal(m_calleeLocals.size()));
    }
    SymbolTableEntry newEntry(varOffset, 0);
    symbolTable->add(NoLockingNecessary, property.impl(), WTF::move(newEntry));
    
    if (varKind == VarKind::Stack) {
        RegisterID* local = addVar();
        RELEASE_ASSERT(local->index() == varOffset.stackOffset().offset());
    }
}

std::optional<Variable> BytecodeGenerator::tryResolveVariable(ExpressionNode* expr)
{
    if (expr->isResolveNode())
        return variable(static_cast<ResolveNode*>(expr)->identifier());

    if (expr->isAssignResolveNode())
        return variable(static_cast<AssignResolveNode*>(expr)->identifier());

    if (expr->isThisNode()) {
        // After generator.ensureThis (which must be invoked in |base|'s materialization), we can ensure that |this| is in local this-register.
        return variable(propertyNames().builtinNames().thisPrivateName(), ThisResolutionType::Local);
    }

    if (expr->isCommaNode()) {
        CommaNode* node = static_cast<CommaNode*>(expr);
        for (; node->next(); node = node->next()) { }
        return tryResolveVariable(node->expr());
    }

    return std::nullopt;
}

// Indicates the least upper bound of resolve type based on local scope. The bytecode linker
// will start with this ResolveType and compute the least upper bound including intercepting scopes.
ResolveType BytecodeGenerator::resolveType()
{
    for (unsigned i = m_lexicalScopeStack.size(); i--; ) {
        if (m_lexicalScopeStack[i].m_isWithScope)
            return Dynamic;
        if (m_usesSloppyEval && m_lexicalScopeStack[i].m_symbolTable->scopeType() == SymbolTable::ScopeType::FunctionNameScope) {
            // We never want to assign to a FunctionNameScope. Returning Dynamic here achieves this goal.
            // If we aren't in non-strict eval mode, then NodesCodeGen needs to take care not to emit
            // a put_to_scope with the destination being the function name scope variable.
            return Dynamic;
        }
    }

    if (m_usesSloppyEval)
        return GlobalPropertyWithVarInjectionChecks;
    return GlobalProperty;
}

RegisterID* BytecodeGenerator::emitResolveScope(RegisterID* dst, const Variable& variable)
{
    switch (variable.offset().kind()) {
    case VarKind::Stack:
        return nullptr;
        
    case VarKind::DirectArgument:
        return argumentsRegister();
        
    case VarKind::Scope: {
        // This always refers to the activation that *we* allocated, and not the current scope that code
        // lives in. Note that this will change once we have proper support for block scoping. Once that
        // changes, it will be correct for this code to return scopeRegister(). The only reason why we
        // don't do that already is that m_lexicalEnvironment is required by ConstDeclNode. ConstDeclNode
        // requires weird things because it is a shameful pile of nonsense, but block scoping would make
        // that code sensible and obviate the need for us to do bad things.
        for (unsigned i = m_lexicalScopeStack.size(); i--; ) {
            auto& stackEntry = m_lexicalScopeStack[i];
            // We should not resolve a variable to VarKind::Scope if a "with" scope lies in between the current
            // scope and the resolved scope.
            RELEASE_ASSERT(!stackEntry.m_isWithScope);

            if (stackEntry.m_symbolTable->get(NoLockingNecessary, variable.ident().impl()).isNull())
                continue;
            
            RegisterID* scope = stackEntry.m_scope;
            RELEASE_ASSERT(scope);
            return scope;
        }

        RELEASE_ASSERT_NOT_REACHED();
        return nullptr;
        
    }
    case VarKind::Invalid:
        // Indicates non-local resolution.
        
        dst = tempDestination(dst);
        OpResolveScope::emit(this, kill(dst), scopeRegister(), addConstant(variable.ident()), resolveType(), localScopeDepth());
        return dst;
    }
    
    RELEASE_ASSERT_NOT_REACHED();
    return nullptr;
}

RegisterID* BytecodeGenerator::emitGetFromScope(RegisterID* dst, RegisterID* scope, const Variable& variable, ResolveMode resolveMode)
{
    switch (variable.offset().kind()) {
    case VarKind::Stack:
        return move(dst, variable.local());
        
    case VarKind::DirectArgument: {
        OpGetFromArguments::emit(this, kill(dst), scope, variable.offset().capturedArgumentsOffset().offset(), nextValueProfileIndex());
        return dst;
    }
        
    case VarKind::Scope:
    case VarKind::Invalid: {
        OpGetFromScope::emit(
            this,
            kill(dst),
            scope,
            addConstant(variable.ident()),
            GetPutInfo(resolveMode, variable.offset().isScope() ? ResolvedClosureVar : resolveType(), InitializationMode::NotInitialization, ecmaMode()),
            localScopeDepth(),
            variable.offset().isScope() ? variable.offset().scopeOffset().offset() : 0,
            nextValueProfileIndex());
        return dst;
    } }
    
    RELEASE_ASSERT_NOT_REACHED();
}

RegisterID* BytecodeGenerator::emitResolveAndGetFromScope(RegisterID* dst, const Variable& variable, ResolveMode resolveMode)
{
    // A `with` scope resolves dynamically and may run observable traps; keep those as two instructions so an OSR exit
    // between them never resolves twice.
    if (!canFuseResolveAndGet(variable)) {
        RefPtr<RegisterID> scope = emitResolveScope(nullptr, variable);
        return emitGetFromScope(dst, scope.get(), variable, resolveMode);
    }
    OpResolveAndGetFromScope::emit(
        this,
        kill(dst),
        scopeRegister(),
        addConstant(variable.ident()),
        GetPutInfo(resolveMode, resolveType(), InitializationMode::NotInitialization, ecmaMode()),
        localScopeDepth(),
        0,
        nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitPutToScope(RegisterID* scope, const Variable& variable, RegisterID* value, ResolveMode resolveMode, InitializationMode initializationMode)
{
    switch (variable.offset().kind()) {
    case VarKind::Stack:
        move(variable.local(), value);
        return value;
        
    case VarKind::DirectArgument:
        OpPutToArguments::emit(this, scope, variable.offset().capturedArgumentsOffset().offset(), value);
        return value;
        
    case VarKind::Scope:
    case VarKind::Invalid: {
        GetPutInfo getPutInfo(0);
        SymbolTableOrScopeDepth symbolTableOrScopeDepth;
        ScopeOffset offset;
        if (variable.offset().isScope()) {
            offset = variable.offset().scopeOffset();
            getPutInfo = GetPutInfo(resolveMode, ResolvedClosureVar, initializationMode, ecmaMode());
            symbolTableOrScopeDepth = SymbolTableOrScopeDepth::symbolTable(VirtualRegister { variable.symbolTableConstantIndex() });
        } else {
            ASSERT(resolveType() != ResolvedClosureVar);
            getPutInfo = GetPutInfo(resolveMode, resolveType(), initializationMode, ecmaMode());
            symbolTableOrScopeDepth = SymbolTableOrScopeDepth::scopeDepth(localScopeDepth());
        }
        OpPutToScope::emit(this, scope, addConstant(variable.ident()), value, getPutInfo, symbolTableOrScopeDepth, !!offset ? offset.offset() : 0);
        return value;
    } }
    
    RELEASE_ASSERT_NOT_REACHED();
}

RegisterID* BytecodeGenerator::emitPutToScopeDynamic(RegisterID* scope, const Identifier& ident, RegisterID* value, ResolveMode resolveMode, InitializationMode initializationMode)
{
    GetPutInfo getPutInfo(resolveMode, Dynamic, initializationMode, ecmaMode());
    unsigned scopeOffset = 0;
    OpPutToScope::emit(this, scope, addConstant(ident), value, getPutInfo, SymbolTableOrScopeDepth::scopeDepth(localScopeDepth()), scopeOffset);
    return value;
}

RegisterID* BytecodeGenerator::initializeVariable(const Variable& variable, RegisterID* value)
{
    RELEASE_ASSERT(variable.offset().kind() != VarKind::Invalid);
    RegisterID* scope = emitResolveScope(nullptr, variable);
    return emitPutToScope(scope, variable, value, ThrowIfNotFound, InitializationMode::NotInitialization);
}

RegisterID* BytecodeGenerator::emitInstanceof(RegisterID* dst, RegisterID* value, RegisterID* constructor, RegisterID* hasInstanceOrPrototype)
{
    OpInstanceof::emit(this, dst, value, constructor, hasInstanceOrPrototype, nextValueProfileIndex(), nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitInByVal(RegisterID* dst, RegisterID* property, RegisterID* base)
{
    for (size_t i = m_forInContextStack.size(); i--; ) {
        ForInContext& context = m_forInContextStack[i].get();
        if (context.local() != property)
            continue;

        OpEnumeratorInByVal::emit<OpcodeSize::Wide32>(this, dst, base, context.mode(), property, context.propertyOffset(), context.enumerator());
        context.addInInst(m_lastInstruction.offset(), property->index());
        return dst;
    }

    OpInByVal::emit(this, dst, base, property);
    return dst;
}

RegisterID* BytecodeGenerator::emitInById(RegisterID* dst, RegisterID* base, const Identifier& property)
{
    OpInById::emit(this, dst, base, addConstant(property));
    return dst;
}

RegisterID* BytecodeGenerator::emitGetLength(RegisterID* dst, RegisterID* base)
{
    OpGetLength::emit(this, kill(dst), base, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitGetById(RegisterID* dst, RegisterID* base, const Identifier& property)
{
    ASSERT_WITH_MESSAGE(!parseIndex(property), "Indexed properties should be handled with get_by_val.");

    if (property == m_vm.propertyNames->length)
        OpGetLength::emit(this, kill(dst), base, nextValueProfileIndex());
    else
        OpGetById::emit(this, kill(dst), base, addConstant(property), nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitGetById(RegisterID* dst, RegisterID* base, RegisterID* thisVal, const Identifier& property)
{
    ASSERT_WITH_MESSAGE(!parseIndex(property), "Indexed properties should be handled with get_by_val.");

    OpGetByIdWithThis::emit(this, kill(dst), base, thisVal, addConstant(property), nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitDirectGetById(RegisterID* dst, RegisterID* base, const Identifier& property)
{
    ASSERT_WITH_MESSAGE(!parseIndex(property), "Indexed properties should be handled with get_by_val_direct.");

    OpGetByIdDirect::emit(this, kill(dst), base, addConstant(property), nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitPutById(RegisterID* base, const Identifier& property, RegisterID* value)
{
    ASSERT_WITH_MESSAGE(!parseIndex(property), "Indexed properties should be handled with put_by_val.");

    unsigned propertyIndex = addConstant(property);

    m_staticPropertyAnalyzer.putById(base, propertyIndex);

    OpPutById::emit(this, base, propertyIndex, value, PutByIdFlags::create(ecmaMode())); // is not direct
    return value;
}

RegisterID* BytecodeGenerator::emitPutById(RegisterID* base, RegisterID* thisValue, const Identifier& property, RegisterID* value)
{
    ASSERT_WITH_MESSAGE(!parseIndex(property), "Indexed properties should be handled with put_by_val.");

    unsigned propertyIndex = addConstant(property);

    OpPutByIdWithThis::emit(this, base, thisValue, propertyIndex, value, ecmaMode());

    return value;
}

RegisterID* BytecodeGenerator::emitDirectPutById(RegisterID* base, const Identifier& property, RegisterID* value)
{
    ASSERT_WITH_MESSAGE(!parseIndex(property), "Indexed properties should be handled with put_by_val(direct).");

    unsigned propertyIndex = addConstant(property);

    m_staticPropertyAnalyzer.putById(base, propertyIndex);

    PutByIdFlags type = PutByIdFlags::createDirect(ecmaMode());
    OpPutById::emit(this, base, propertyIndex, value, type);
    return value;
}

void BytecodeGenerator::emitPutGetterById(RegisterID* base, const Identifier& property, unsigned attributes, RegisterID* getter)
{
    unsigned propertyIndex = addConstant(property);
    m_staticPropertyAnalyzer.putById(base, propertyIndex);

    OpPutGetterById::emit(this, base, propertyIndex, attributes, getter);
}

void BytecodeGenerator::emitPutSetterById(RegisterID* base, const Identifier& property, unsigned attributes, RegisterID* setter)
{
    unsigned propertyIndex = addConstant(property);
    m_staticPropertyAnalyzer.putById(base, propertyIndex);

    OpPutSetterById::emit(this, base, propertyIndex, attributes, setter);
}

void BytecodeGenerator::emitPutGetterSetter(RegisterID* base, const Identifier& property, unsigned attributes, RegisterID* getter, RegisterID* setter)
{
    unsigned propertyIndex = addConstant(property);

    m_staticPropertyAnalyzer.putById(base, propertyIndex);

    OpPutGetterSetterById::emit(this, base, propertyIndex, attributes, getter, setter);
}

void BytecodeGenerator::emitPutGetterByVal(RegisterID* base, RegisterID* property, unsigned attributes, RegisterID* getter)
{
    OpPutGetterByVal::emit(this, base, property, attributes, getter);
}

void BytecodeGenerator::emitPutSetterByVal(RegisterID* base, RegisterID* property, unsigned attributes, RegisterID* setter)
{
    OpPutSetterByVal::emit(this, base, property, attributes, setter);
}

void BytecodeGenerator::emitPutGeneratorFields(RegisterID* nextFunction)
{
    emitPutInternalField(m_generatorRegister, static_cast<unsigned>(JSGenerator::Field::Next), nextFunction);

    // We do not store 'this' in arrow function within constructor,
    // because it might be not initialized, if super is called later.
    if (!(isDerivedConstructorContext() && m_codeBlock->parseMode() == SourceParseMode::AsyncArrowFunctionMode))
        emitPutInternalField(m_generatorRegister, static_cast<unsigned>(JSGenerator::Field::This), &m_thisRegister);
}

void BytecodeGenerator::emitPutAsyncGeneratorFields(RegisterID* nextFunction)
{
    ASSERT(isAsyncGeneratorWrapperParseMode(parseMode()));

    emitPutInternalField(m_generatorRegister, static_cast<unsigned>(JSAsyncGenerator::Field::Next), nextFunction);
    emitPutInternalField(m_generatorRegister, static_cast<unsigned>(JSAsyncGenerator::Field::This), &m_thisRegister);
}

RegisterID* BytecodeGenerator::emitDeleteById(RegisterID* dst, RegisterID* base, const Identifier& property)
{
    OpDelById::emit(this, dst, base, addConstant(property), ecmaMode());
    return dst;
}

RegisterID* BytecodeGenerator::emitGetByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    for (size_t i = m_forInContextStack.size(); i--; ) {
        ForInContext& context = m_forInContextStack[i].get();
        if (context.local() != property)
            continue;

        // FIXME: We should have a better bytecode rewriter that can resize chunks.
        OpEnumeratorGetByVal::emit<OpcodeSize::Wide32>(this, kill(dst), base, context.mode(), property, context.propertyOffset(), context.enumerator(), nextValueProfileIndex());
        context.addGetInst(m_lastInstruction.offset(), property->index());
        return dst;
    }

    OpGetByVal::emit(this, kill(dst), base, property, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitGetByVal(RegisterID* dst, RegisterID* base, RegisterID* thisValue, RegisterID* property)
{
    OpGetByValWithThis::emit(this, kill(dst), base, thisValue, property, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitGetPrototypeOf(RegisterID* dst, RegisterID* value)
{
    OpGetPrototypeOf::emit(this, dst, value, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitPutByVal(RegisterID* base, RegisterID* property, RegisterID* value)
{
    for (size_t i = m_forInContextStack.size(); i--; ) {
        ForInContext& context = m_forInContextStack[i].get();
        if (context.local() != property)
            continue;
        return emitEnumeratorPutByVal(context, base, property, value);
    }

    OpPutByVal::emit(this, base, property, value, ecmaMode());
    return value;
}

RegisterID* BytecodeGenerator::emitPutByVal(RegisterID* base, RegisterID* thisValue, RegisterID* property, RegisterID* value)
{
    OpPutByValWithThis::emit(this, base, thisValue, property, value, ecmaMode());
    return value;
}

RegisterID* BytecodeGenerator::emitPutByValWithECMAMode(RegisterID* base, RegisterID* thisValue, RegisterID* property, RegisterID* value, ECMAMode ecmaMode)
{
    OpPutByValWithThis::emit(this, base, thisValue, property, value, ecmaMode);
    return value;
}

RegisterID* BytecodeGenerator::emitEnumeratorPutByVal(ForInContext& context, RegisterID* base, RegisterID* property, RegisterID* value)
{
    // FIXME: We should have a better bytecode rewriter that can resize chunks.
    OpEnumeratorPutByVal::emit<OpcodeSize::Wide32>(this, base, context.mode(), property, context.propertyOffset(), context.enumerator(), value, ecmaMode());
    context.addPutInst(m_lastInstruction.offset(), property->index());
    return value;
}

RegisterID* BytecodeGenerator::emitGetPrivateName(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    OpGetPrivateName::emit(this, dst, base, property, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitHasPrivateName(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    OpHasPrivateName::emit(this, dst, base, property);
    return dst;
}

RegisterID* BytecodeGenerator::emitHasStructureWithFlags(RegisterID* dst, RegisterID* src, unsigned flags)
{
    OpHasStructureWithFlags::emit(this, dst, src, flags);
    return dst;
}

RegisterID* BytecodeGenerator::emitDirectPutByVal(RegisterID* base, RegisterID* property, RegisterID* value)
{
    OpPutByValDirect::emit(this, base, property, value, ecmaMode());
    return value;
}

RegisterID* BytecodeGenerator::emitDeleteByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
{
    OpDelByVal::emit(this, dst, base, property, ecmaMode());
    return dst;
}

RegisterID* BytecodeGenerator::emitGetInternalField(RegisterID* dst, RegisterID* base, unsigned index)
{
    OpGetInternalField::emit(this, dst, base, index, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitPutInternalField(RegisterID* base, unsigned index, RegisterID* value)
{
    OpPutInternalField::emit(this, base, index, value);
    return value;
}

RegisterID* BytecodeGenerator::emitDefinePrivateField(RegisterID* base, RegisterID* property, RegisterID* value)
{
    OpPutPrivateName::emit(this, base, property, value, PrivateFieldPutKind::define());
    return value;
}

void BytecodeGenerator::emitCreatePrivateBrand(const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
{
    RefPtr<RegisterID> createPrivateSymbol = moveLinkTimeConstant(nullptr, LinkTimeConstant::createPrivateSymbol);

    CallArguments arguments(*this, nullptr, 1);
    emitLoad(arguments.thisRegister(), jsUndefined());
    emitLoad(arguments.argumentRegister(0), jsEmptyString(m_vm));
    RegisterID* newSymbol = emitCall(finalDestination(nullptr, createPrivateSymbol.get()), createPrivateSymbol.get(), NoExpectedFunction, arguments, divot, divotStart, divotEnd, DebuggableCall::No);

    Variable privateBrandVar = variable(propertyNames().builtinNames().privateBrandPrivateName());

    emitPutToScope(scopeRegister(), privateBrandVar, newSymbol, DoNotThrowIfNotFound, InitializationMode::ConstInitialization);
}

void BytecodeGenerator::emitInstallPrivateBrand(RegisterID* target)
{
    Variable privateBrandVar = variable(propertyNames().builtinNames().privateBrandPrivateName());
    RefPtr<RegisterID> privateBrandVarScope = emitResolveScope(nullptr, privateBrandVar);
    bool isStatic = false;
    RegisterID* privateBrandSymbol = emitGetPrivateBrand(newTemporary(), privateBrandVarScope.get(), isStatic);
    OpSetPrivateBrand::emit(this, target, privateBrandSymbol);
}

void BytecodeGenerator::emitInstallPrivateClassBrand(RegisterID* target)
{
    Variable privateBrandVar = variable(propertyNames().builtinNames().privateClassBrandPrivateName());
    emitPutToScope(scopeRegister(), privateBrandVar, target, DoNotThrowIfNotFound, InitializationMode::ConstInitialization);
}

RegisterID* BytecodeGenerator::emitGetPrivateBrand(RegisterID* dst, RegisterID* scope, bool isStatic)
{
    ASSERT(scope);
    OpGetFromScope::emit(
        this,
        kill(dst),
        scope,
        addConstant(isStatic ? propertyNames().builtinNames().privateClassBrandPrivateName() : propertyNames().builtinNames().privateBrandPrivateName()),
        GetPutInfo(ThrowIfNotFound, ResolvedClosureVar, InitializationMode::NotInitialization, ecmaMode()),
        0,
        isStatic ? PrivateNameEntry::privateClassBrandOffset : PrivateNameEntry::privateBrandOffset,
        nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitPrivateFieldPut(RegisterID* base, RegisterID* property, RegisterID* value)
{
    OpPutPrivateName::emit(this, base, property, value, PrivateFieldPutKind::set());
    return value;
}

RegisterID* BytecodeGenerator::emitHasPrivateBrand(RegisterID* dst, RegisterID* base, RegisterID* brand, bool isStatic)
{
    if (isStatic) {
        Ref<Label> isObjectLabel = newLabel();
        emitJumpIfTrue(emitIsObject(newTemporary(), base), isObjectLabel.get());
        emitThrowTypeError("Cannot access static private method or accessor of a non-Object"_s);
        emitLabel(isObjectLabel.get());
        emitEqualityOp<OpStricteq>(dst, base, brand);
    } else
        OpHasPrivateBrand::emit(this, dst, base, brand);
    return dst;
}

void BytecodeGenerator::emitCheckPrivateBrand(RegisterID* base, RegisterID* brand, bool isStatic)
{
    if (isStatic) {
        Ref<Label> brandCheckOkLabel = newLabel();
        emitTDZCheck(brand);
        emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), base, brand), brandCheckOkLabel.get());
        emitThrowTypeError("Cannot access static private method or accessor"_s);
        emitLabel(brandCheckOkLabel.get());
        return;
    
    }
    OpCheckPrivateBrand::emit(this, base, brand);
}

void BytecodeGenerator::emitSuperSamplerBegin()
{
    OpSuperSamplerBegin::emit(this);
}

void BytecodeGenerator::emitSuperSamplerEnd()
{
    OpSuperSamplerEnd::emit(this);
}

RegisterID* BytecodeGenerator::emitIdWithProfile(RegisterID* src, SpeculatedType profile)
{
    OpIdentityWithProfile::emit(this, src, static_cast<uint32_t>(profile >> 32), static_cast<uint32_t>(profile));
    return src;
}

void BytecodeGenerator::emitUnreachable()
{
    OpUnreachable::emit(this);
}

RegisterID* BytecodeGenerator::emitGetArgument(RegisterID* dst, int32_t index)
{
    OpGetArgument::emit(this, dst, index + 1 /* Including |this| */, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitCreateThis(RegisterID* dst)
{
    OpCreateThis::emit(this, dst, dst, 0);
    m_staticPropertyAnalyzer.createThis(dst, m_lastInstruction);
    return dst;
}

RegisterID* BytecodeGenerator::emitCreatePromise(RegisterID* dst, RegisterID* newTarget)
{
    OpCreatePromise::emit(this, dst, newTarget);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewPromise(RegisterID* dst)
{
    OpNewPromise::emit(this, dst);
    return dst;
}

RegisterID* BytecodeGenerator::emitCreateGenerator(RegisterID* dst, RegisterID* newTarget)
{
    OpCreateGenerator::emit(this, dst, newTarget);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewGenerator(RegisterID* dst)
{
    OpNewGenerator::emit(this, dst);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewAsyncFunctionGenerator(RegisterID* dst)
{
    OpNewAsyncFunctionGenerator::emit(this, dst);
    return dst;
}

RegisterID* BytecodeGenerator::emitCreateAsyncGenerator(RegisterID* dst, RegisterID* newTarget)
{
    OpCreateAsyncGenerator::emit(this, dst, newTarget);
    return dst;
}

RegisterID* BytecodeGenerator::emitInstanceFieldInitializationIfNeeded(RegisterID* dst, RegisterID* constructor, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
{
    if (!(isConstructor() || isDerivedConstructorContext()) || needsClassFieldInitializer() == NeedsClassFieldInitializer::No)
        return dst;

    RefPtr<RegisterID> initializer = emitDirectGetById(newTemporary(), constructor, propertyNames().builtinNames().instanceFieldInitializerPrivateName());
    CallArguments args(*this, nullptr);
    emitMove(args.thisRegister(), dst);
    emitCallIgnoreResult(newTemporary(), initializer.get(), NoExpectedFunction, args, divot, divotStart, divotEnd, DebuggableCall::No);

    return dst;
}

void BytecodeGenerator::emitTDZCheck(RegisterID* target, const Variable& variable)
{
    OpCheckTdz::emit(this, target, addConstantValue(addStringConstant(variable.ident())));
}

void BytecodeGenerator::emitTDZCheck(RegisterID* target)
{
    OpCheckTdz::emit(this, target, addConstantValue(jsUndefined()));
}

bool BytecodeGenerator::needsTDZCheck(const Variable& variable)
{
    for (unsigned i = m_TDZStack.size(); i--;) {
        auto iter = m_TDZStack[i].first.find(variable.ident().impl());
        if (iter == m_TDZStack[i].first.end())
            continue;
        return iter->value != TDZNecessityLevel::NotNeeded;
    }

    {
        TDZEnvironmentLink* environment = m_cachedParentTDZ.get();
        while (environment) {
            if (environment->contains(variable.ident().impl()))
                return true;
            environment = environment->parent();
        }
    }
    return false;
}

void BytecodeGenerator::emitTDZCheckIfNecessary(const Variable& variable, RegisterID* target, RegisterID* scope)
{
    if (needsTDZCheck(variable)) {
        if (target)
            emitTDZCheck(target, variable);
        else {
            RELEASE_ASSERT(!variable.isLocal() && scope);
            RefPtr<RegisterID> result = emitGetFromScope(newTemporary(), scope, variable, DoNotThrowIfNotFound);
            emitTDZCheck(result.get(), variable);
        }
    }
}

void BytecodeGenerator::liftTDZCheckIfPossible(const Variable& variable)
{
    UniquedStringImpl* identifier = variable.ident().impl();
    for (unsigned i = m_TDZStack.size(); i--;) {
        auto iter = m_TDZStack[i].first.find(identifier);
        if (iter != m_TDZStack[i].first.end()) {
            if (iter->value == TDZNecessityLevel::Optimize)
                iter->value = TDZNecessityLevel::NotNeeded;
            break;
        }
    }
}

// This should be called only with PrivateNames available.
PrivateNameEntry BytecodeGenerator::getPrivateTraits(const Identifier& ident)
{
    for (unsigned i = m_privateNamesStack.size(); i--; ) {
        auto& map = m_privateNamesStack[i];
        auto it = map.find(ident.impl());
        if (it != map.end())
            return it->value;
    }

    RELEASE_ASSERT_NOT_REACHED();
    return PrivateNameEntry();
}

void BytecodeGenerator::pushPrivateAccessNames(const PrivateNameEnvironment* environment)
{
    if (!environment || !environment->size())
        return;

    m_privateNamesStack.append(*environment);
}

void BytecodeGenerator::popPrivateAccessNames()
{
    ASSERT(m_privateNamesStack.size());
    m_privateNamesStack.removeLast();
}

void BytecodeGenerator::pushTDZVariables(const VariableEnvironment& environment, TDZCheckOptimization optimization, TDZRequirement requirement)
{
    if (!environment.size())
        return;
    
    TDZNecessityLevel level;
    if (requirement == TDZRequirement::UnderTDZ) {
        if (optimization == TDZCheckOptimization::Optimize)
            level = TDZNecessityLevel::Optimize;
        else
            level = TDZNecessityLevel::DoNotOptimize;
    } else
        level = TDZNecessityLevel::NotNeeded;
    
    TDZMap map;
    for (const auto& entry : environment)
        map.add(entry.key, entry.value.isFunction() ? TDZNecessityLevel::NotNeeded : level);

    m_TDZStack.append(TDZStackEntry { WTF::move(map), nullptr });
}

Vector<Identifier> BytecodeGenerator::getParameterNames() const
{
    RELEASE_ASSERT(m_scopeNode->isFunctionNode());
    FunctionParameters& parameters = *static_cast<FunctionNode*>(m_scopeNode)->parameters();
    Vector<Identifier> parameterNames;
    for (unsigned i = 0; i < parameters.size(); i++)
        parameters.at(i).first->collectBoundIdentifiers(parameterNames);
    return parameterNames;
}

std::optional<PrivateNameEnvironment> BytecodeGenerator::getAvailablePrivateAccessNames()
{
    PrivateNameEnvironment result;
    UncheckedKeyHashSet<UniquedStringImpl*> excludedNames;
    for (unsigned i = m_privateNamesStack.size(); i--; ) {
        auto& map = m_privateNamesStack[i];
        for (auto& entry : map)  {
            auto addResult = excludedNames.add(entry.key.get());
            if (addResult.isNewEntry)
                result.add(entry.key, entry.value);
        }
    }

    if (!result.size())
        return std::nullopt;
    return result;
}

RefPtr<TDZEnvironmentLink> BytecodeGenerator::getVariablesUnderTDZ()
{
    RefPtr<TDZEnvironmentLink> parent = m_cachedParentTDZ;
    if (!m_TDZStack.size())
        return parent;

    auto assertCacheIsCoherent = [&] {
#if ASSERT_ENABLED
        TDZEnvironmentLink* parent = m_cachedParentTDZ.get();
        for (auto& entry : m_TDZStack) {
            ASSERT(entry.second);
            ASSERT(entry.second->parent() == parent);
            parent = entry.second.get();
        }
#endif
    };

    if (m_TDZStack.last().second) {
        assertCacheIsCoherent();
        return m_TDZStack.last().second;
    }

    for (auto& entry : m_TDZStack) {
        if (!entry.second) {
            auto& map = entry.first;
            TDZEnvironment environment;
            for (auto& entry : map) {
                if (entry.value != TDZNecessityLevel::NotNeeded)
                    environment.add(entry.key.get());
            }
            entry.second = TDZEnvironmentLink::create(m_vm.m_compactVariableMap->get(environment), parent);
        }
        parent = entry.second;
    }

    assertCacheIsCoherent();

    return parent;
}

void BytecodeGenerator::preserveTDZStack(BytecodeGenerator::PreservedTDZStack& preservedStack)
{
    preservedStack.m_preservedTDZStack = m_TDZStack;
}

void BytecodeGenerator::restoreTDZStack(const BytecodeGenerator::PreservedTDZStack& preservedStack)
{
    m_TDZStack = preservedStack.m_preservedTDZStack;
}

RegisterID* BytecodeGenerator::emitNewObject(RegisterID* dst)
{
    OpNewObject::emit(this, dst, 0);
    m_staticPropertyAnalyzer.newObject(dst, m_lastInstruction);

    return dst;
}

JSValue BytecodeGenerator::addBigIntConstant(const Identifier& identifier, uint8_t radix, bool sign)
{
    return m_bigIntMap.ensure(BigIntMapEntry(identifier.impl(), radix, sign), [&] {
        VM& vm = this->vm();
        DeferTermination deferScope(vm);
        auto scope = DECLARE_TOP_EXCEPTION_SCOPE(vm);
        auto parseIntSign = sign ? JSBigInt::ParseIntSign::Signed : JSBigInt::ParseIntSign::Unsigned;
        JSValue bigIntInMap = JSBigInt::parseInt(nullptr, vm, identifier.string(), radix, JSBigInt::ErrorParseMode::ThrowExceptions, parseIntSign);
        scope.assertNoException();
        addConstantValue(bigIntInMap);

        return bigIntInMap;
    }).iterator->value;
}

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

RegisterID* BytecodeGenerator::addTemplateObjectConstant(Ref<TemplateObjectDescriptor>&& descriptor, int endOffset)
{
    auto result = m_templateObjectDescriptorSet.add(WTF::move(descriptor));
    JSTemplateObjectDescriptor* descriptorValue = m_templateDescriptorMap.ensure(endOffset, [&] {
        return JSTemplateObjectDescriptor::create(vm(), result.iterator->copyRef(), endOffset);
    }).iterator->value;
    int index = addConstantIndex();
    m_codeBlock->addConstant(descriptorValue);
    return &m_constantPoolRegisters[index];
}

RegisterID* BytecodeGenerator::emitNewArrayBuffer(RegisterID* dst, JSCellButterfly* array, IndexingType recommendedIndexingType)
{
    OpNewArrayBuffer::emit(this, dst, addConstantValue(array), recommendedIndexingType);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewArray(RegisterID* dst, ElementNode* elements, unsigned length, IndexingType recommendedIndexingType)
{
    Vector<RefPtr<RegisterID>, 16, UnsafeVectorOverflow> argv;
    for (ElementNode* n = elements; n; n = n->next()) {
        if (!length)
            break;
        length--;
        ASSERT(!n->value()->isSpreadExpression());
        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());
    }
    ASSERT(!length);
    OpNewArray::emit(this, dst, argv.size() ? argv[0].get() : VirtualRegister { 0 }, argv.size(), recommendedIndexingType);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewArrayWithSpread(RegisterID* dst, ElementNode* elements)
{
    BitVector bitVector;
    Vector<RefPtr<RegisterID>, 16> argv;
    for (ElementNode* node = elements; node; node = node->next()) {
        bitVector.set(argv.size(), node->value()->isSpreadExpression());

        argv.append(newTemporary());
        // op_new_array_with_spread requires the initial values to be a sequential range of registers.
        RELEASE_ASSERT(argv.size() == 1 || argv[argv.size() - 1]->index() == argv[argv.size() - 2]->index() - 1);
    }

    RELEASE_ASSERT(argv.size());

    {
        unsigned i = 0;
        for (ElementNode* node = elements; node; node = node->next()) {
            if (node->value()->isSpreadExpression()) {
                auto* spread = static_cast<SpreadExpressionNode*>(node->value());
                ExpressionNode* expression = spread->expression();
                RefPtr<RegisterID> tmp = newTemporary();
                emitNode(tmp.get(), expression);

                emitExpressionInfo(spread->divot(), spread->divotStart(), spread->divotEnd());
                OpSpread::emit(this, argv[i].get(), tmp.get());
            } else {
                ExpressionNode* expression = node->value();
                emitNode(argv[i].get(), expression);
            }
            i++;
        }
    }

    unsigned bitVectorIndex = m_codeBlock->addBitVector(WTF::move(bitVector));
    OpNewArrayWithSpread::emit(this, dst, argv[0].get(), argv.size(), bitVectorIndex);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewArrayWithSize(RegisterID* dst, RegisterID* length)
{
    OpNewArrayWithSize::emit(this, dst, length);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewArrayWithSpecies(RegisterID* dst, RegisterID* length, RegisterID* array)
{
    OpNewArrayWithSpecies::emit(this, dst, length, array, nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitNewRegExp(RegisterID* dst, RegExp* regExp)
{
    OpNewRegExp::emit(this, dst, addConstantValue(regExp));
    return dst;
}

void BytecodeGenerator::emitNewFunctionExpressionCommon(RegisterID* dst, FunctionMetadataNode* function)
{
    unsigned index = m_codeBlock->addFunctionExpr(makeFunction(function));

    switch (function->parseMode()) {
    case SourceParseMode::GeneratorWrapperFunctionMode:
    case SourceParseMode::GeneratorWrapperMethodMode:
        OpNewGeneratorFuncExp::emit(this, dst, scopeRegister(), index);
        break;
    case SourceParseMode::AsyncFunctionMode:
    case SourceParseMode::AsyncMethodMode:
    case SourceParseMode::AsyncArrowFunctionMode:
        OpNewAsyncFuncExp::emit(this, dst, scopeRegister(), index);
        break;
    case SourceParseMode::AsyncGeneratorWrapperFunctionMode:
    case SourceParseMode::AsyncGeneratorWrapperMethodMode:
        OpNewAsyncGeneratorFuncExp::emit(this, dst, scopeRegister(), index);
        break;
    default:
        OpNewFuncExp::emit(this, dst, scopeRegister(), index);
        break;
    }
}

RegisterID* BytecodeGenerator::emitNewFunctionExpression(RegisterID* dst, FuncExprNode* func)
{
    emitNewFunctionExpressionCommon(dst, func->metadata());
    return dst;
}

RegisterID* BytecodeGenerator::emitNewArrowFunctionExpression(RegisterID* dst, ArrowFuncExprNode* func)
{
    ASSERT(SourceParseModeSet(SourceParseMode::ArrowFunctionMode, SourceParseMode::AsyncArrowFunctionMode).contains(func->metadata()->parseMode()));
    emitNewFunctionExpressionCommon(dst, func->metadata());
    return dst;
}

RegisterID* BytecodeGenerator::emitNewMethodDefinition(RegisterID* dst, MethodDefinitionNode* func)
{
    ASSERT(isMethodParseMode(func->metadata()->parseMode()));
    emitNewFunctionExpressionCommon(dst, func->metadata());
    return dst;
}

RegisterID* BytecodeGenerator::emitNewDefaultConstructor(RegisterID* dst, ConstructorKind constructorKind, const Identifier& name,
    const Identifier& ecmaName, const SourceCode& classSource, NeedsClassFieldInitializer needsClassFieldInitializer, PrivateBrandRequirement privateBrandRequirement)
{
    UnlinkedFunctionExecutable* executable = m_vm.builtinExecutables()->createDefaultConstructor(constructorKind, name, needsClassFieldInitializer, privateBrandRequirement);
    executable->setEcmaName(ecmaName);
    executable->setClassSource(classSource);

    unsigned index = m_codeBlock->addFunctionExpr(executable);

    OpNewFuncExp::emit(this, dst, scopeRegister(), index);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewClassFieldInitializerFunction(RegisterID* dst, Vector<UnlinkedFunctionExecutable::ClassElementDefinition>&& classElementDefinitions, bool isDerived)
{
    DerivedContextType newDerivedContextType;
    SuperBinding superBinding;
    if (!isDerived) {
        newDerivedContextType = DerivedContextType::None;
        superBinding = SuperBinding::NotNeeded;
    } else {
        newDerivedContextType = DerivedContextType::DerivedMethodContext;
        superBinding = SuperBinding::Needed;
    }

    auto variablesUnderTDZ = getVariablesUnderTDZ();
    std::optional<PrivateNameEnvironment> parentPrivateNameEnvironment = getAvailablePrivateAccessNames();
    SourceParseMode parseMode = SourceParseMode::ClassFieldInitializerMode;
    ConstructAbility constructAbility = ConstructAbility::CannotConstruct;

    FunctionMetadataNode metadata(parserArena(), JSTokenLocation(), JSTokenLocation(), 0, 0, 0, 0, 0, ImplementationVisibility::Private, StrictModeLexicallyScopedFeature, ConstructorKind::None, superBinding, 0, parseMode, false);
    metadata.finishParsing(m_scopeNode->source(), Identifier(), FunctionMode::MethodDefinition);
    auto initializer = UnlinkedFunctionExecutable::create(m_vm, m_scopeNode->source(), &metadata, isBuiltinFunction() ? UnlinkedBuiltinFunction : UnlinkedNormalFunction, constructAbility, InlineAttribute::Always, scriptMode(), WTF::move(variablesUnderTDZ), { }, WTF::move(parentPrivateNameEnvironment), newDerivedContextType, EvalContextType::InstanceFieldEvalContext, NeedsClassFieldInitializer::No, PrivateBrandRequirement::None);
    initializer->setClassElementDefinitions(WTF::move(classElementDefinitions));

    unsigned index = m_codeBlock->addFunctionExpr(initializer);
    OpNewFuncExp::emit(this, dst, scopeRegister(), index);
    return dst;
}

RegisterID* BytecodeGenerator::emitNewFunction(RegisterID* dst, FunctionMetadataNode* function)
{
    unsigned index = m_codeBlock->addFunctionDecl(makeFunction(function));
    if (isGeneratorWrapperParseMode(function->parseMode()))
        OpNewGeneratorFunc::emit(this, dst, scopeRegister(), index);
    else if (function->parseMode() == SourceParseMode::AsyncFunctionMode)
        OpNewAsyncFunc::emit(this, dst, scopeRegister(), index);
    else if (isAsyncGeneratorWrapperParseMode(function->parseMode()))
        OpNewAsyncGeneratorFunc::emit(this, dst, scopeRegister(), index);
    else
        OpNewFunc::emit(this, dst, scopeRegister(), index);
    return dst;
}

bool BytecodeGenerator::shouldSetFunctionName(ExpressionNode* node)
{
    if (node->isBaseFuncExprNode()) {
        FunctionMetadataNode* metadata = static_cast<BaseFuncExprNode*>(node)->metadata();
        if (!metadata->ecmaName().isNull())
            return false;
    } else if (node->isClassExprNode()) {
        ClassExprNode* classExprNode = static_cast<ClassExprNode*>(node);
        if (!classExprNode->ecmaName().isNull())
            return false;
        if (classExprNode->hasStaticProperty(m_vm.propertyNames->name))
            return false;
    } else
        return false;

    return true;
}

void BytecodeGenerator::emitSetFunctionName(RegisterID* value, const Identifier& ident)
{
    RefPtr<RegisterID> name = emitLoad(newTemporary(), ident);

    // FIXME: We should use an op_call to an internal function here instead.
    // https://bugs.webkit.org/show_bug.cgi?id=155547
    OpSetFunctionName::emit(this, value, name);
}

void BytecodeGenerator::emitSetFunctionName(RegisterID* value, RegisterID* name)
{
    // FIXME: We should use an op_call to an internal function here instead.
    // https://bugs.webkit.org/show_bug.cgi?id=155547
    OpSetFunctionName::emit(this, value, name);
}

void BytecodeGenerator::emitAsyncIteratorOpen(RegisterID* iterator, RegisterID* next, RegisterID* symbolIterator, CallArguments& iterable, const ThrowableExpressionData* node)
{
    // Reserve space for call frame. Mirrors emitIteratorOpen.
    Vector<RefPtr<RegisterID>, CallFrame::headerSizeInRegisters, UnsafeVectorOverflow> callFrame;
    for (int i = 0; i < CallFrame::headerSizeInRegisters; ++i)
        callFrame.append(newTemporary());

    if (shouldEmitDebugHooks())
        emitDebugHook(WillExecuteExpression, node->divotStart());

    emitExpressionInfo(node->divot(), node->divotStart(), node->divotEnd());
    OpAsyncIteratorOpen::emit(this, iterator, next, symbolIterator, iterable.thisRegister(), iterable.stackOffset(), nextValueProfileIndex(), nextValueProfileIndex(), nextValueProfileIndex());
}

void BytecodeGenerator::emitGetGenericAsyncIterator(RegisterID* iterator, RegisterID* next, RegisterID* subject, const ThrowableExpressionData* node)
{
    emitExpressionInfo(node->divot(), node->divotStart(), node->divotEnd());
    RefPtr<RegisterID> symbolAsyncIterator = emitGetById(newTemporary(), subject, propertyNames().asyncIteratorSymbol);
    CallArguments args(*this, nullptr, 0);
    move(args.thisRegister(), subject);
    emitAsyncIteratorOpen(iterator, next, symbolAsyncIterator.get(), args, node);
}

RegisterID* BytecodeGenerator::emitAsyncIteratorNext(RegisterID* dst, RegisterID* next, RegisterID* iterator, RegisterID* value, const ThrowableExpressionData* node)
{
    // dst is allowed to alias value (emitDelegateYield's async path reuses one temporary for both):
    // value is read into the call's argument register below before dst is written by OpAsyncIteratorNext::emit.
    CallArguments nextArguments(*this, nullptr, value ? 1 : 0);
    move(nextArguments.thisRegister(), iterator);
    if (value)
        move(nextArguments.argumentRegister(0), value);

    // Reserve space for call frame. Mirrors emitIteratorNext / emitAsyncIteratorOpen; the generic
    // branch of op_async_iterator_next makes a real next.call(iterator), so numCalleeLocals must
    // cover the callee frame header sitting below argv.
    Vector<RefPtr<RegisterID>, CallFrame::headerSizeInRegisters, UnsafeVectorOverflow> callFrame;
    for (int i = 0; i < CallFrame::headerSizeInRegisters; ++i)
        callFrame.append(newTemporary());

    emitExpressionInfo(node->divot(), node->divotStart(), node->divotEnd());
    OpAsyncIteratorNext::emit(this, kill(dst), next, nextArguments.thisRegister(), generatorRegister(), !!value, nextArguments.stackOffset(), nextValueProfileIndex());
    return dst;
}

RegisterID* BytecodeGenerator::emitCall(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    return emitCall<OpCall>(dst, func, expectedFunction, callArguments, divot, divotStart, divotEnd, debuggableCall);
}

void BytecodeGenerator::emitCallIgnoreResult(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    emitCall<OpCallIgnoreResult>(dst, func, expectedFunction, callArguments, divot, divotStart, divotEnd, debuggableCall);
}

RegisterID* BytecodeGenerator::emitCallInTailPosition(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    if (m_allowTailCallOptimization) {
        m_codeBlock->setHasTailCalls();
        return emitCall<OpTailCall>(dst, func, expectedFunction, callArguments, divot, divotStart, divotEnd, debuggableCall);
    }
    if (m_allowCallIgnoreResultOptimization)
        return emitCall<OpCallIgnoreResult>(dst, func, expectedFunction, callArguments, divot, divotStart, divotEnd, debuggableCall);
    return emitCall<OpCall>(dst, func, expectedFunction, callArguments, divot, divotStart, divotEnd, debuggableCall);
}

RegisterID* BytecodeGenerator::emitCallDirectEval(RegisterID* dst, RegisterID* func, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    return emitCall<OpCallDirectEval>(dst, func, NoExpectedFunction, callArguments, divot, divotStart, divotEnd, debuggableCall);
}

ExpectedFunction BytecodeGenerator::expectedFunctionForIdentifier(const Identifier& identifier)
{
    if (shouldEmitDebugHooks()) [[unlikely]]
        return NoExpectedFunction;
    if (identifier == propertyNames().Object || identifier == propertyNames().builtinNames().ObjectPrivateName())
        return ExpectObjectConstructor;
    if (identifier == propertyNames().Array || identifier == propertyNames().builtinNames().ArrayPrivateName())
        return ExpectArrayConstructor;
    return NoExpectedFunction;
}

ExpectedFunction BytecodeGenerator::emitExpectedFunctionSnippet(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, Label& done)
{
    Ref<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;
        
        OpJneqPtr::emit(this, func, moveLinkTimeConstant(nullptr, LinkTimeConstant::Object), realCall->bind(this));
        
        if (dst != ignoredResult())
            emitNewObject(dst);
        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;
        
        OpJneqPtr::emit(this, func, moveLinkTimeConstant(nullptr, LinkTimeConstant::Array), realCall->bind(this));
        
        if (dst != ignoredResult()) {
            if (callArguments.argumentCountIncludingThis() == 2)
                emitNewArrayWithSize(dst, callArguments.argumentRegister(0));
            else {
                ASSERT(callArguments.argumentCountIncludingThis() == 1);
                OpNewArray::emit(this, dst, VirtualRegister { 0 }, 0, ArrayWithUndecided);
            }
        }
        break;
    }
        
    default:
        ASSERT(expectedFunction == NoExpectedFunction);
        return NoExpectedFunction;
    }
    
    OpJmp::emit(this, done.bind(this));
    emitLabel(realCall.get());
    
    return expectedFunction;
}

LexicallyScopedFeatures BytecodeGenerator::computeFeaturesForCallDirectEval()
{
    LexicallyScopedFeatures features = lexicallyScopedFeatures();

    for (unsigned i = m_lexicalScopeStack.size(); i--; ) {
        if (m_lexicalScopeStack[i].m_isWithScope) {
            features |= TaintedByWithScopeLexicallyScopedFeature;
            break;
        }
    }

    return features;
}

template<typename CallOp>
RegisterID* BytecodeGenerator::emitCall(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    constexpr auto opcodeID = CallOp::opcodeID;
    ASSERT(opcodeID == op_call || opcodeID == op_call_direct_eval || opcodeID == op_tail_call || opcodeID == op_call_ignore_result);
    ASSERT(func->refCount());
    
    // Generate code for arguments.
    unsigned argument = 0;
    if (callArguments.argumentsNode()) {
        ArgumentListNode* n = callArguments.argumentsNode()->m_listNode;
        if (n && n->m_expr->isSpreadExpression()) {
            RELEASE_ASSERT(!n->m_next);
            RELEASE_ASSERT(opcodeID != op_call_direct_eval);
            auto expression = static_cast<SpreadExpressionNode*>(n->m_expr)->expression();
            if (expression->isArrayLiteral()) {
                auto* elements = static_cast<ArrayNode*>(expression)->elements();
                if (elements && !elements->next() && elements->value()->isSpreadExpression()) {
                    auto* spread = static_cast<SpreadExpressionNode*>(elements->value());
                    ExpressionNode* expression = spread->expression();
                    RefPtr<RegisterID> argumentRegister = tempDestination(emitNode(callArguments.argumentRegister(0), expression));
                    emitExpressionInfo(spread->divot(), spread->divotStart(), spread->divotEnd());
                    OpSpread::emit(this, argumentRegister.get(), argumentRegister.get());

                    return emitCallVarargs<typename VarArgsOp<CallOp>::type>(dst, func, callArguments.thisRegister(), argumentRegister.get(), newTemporary(), 0, divot, divotStart, divotEnd, debuggableCall);
                }
            }
            RefPtr<RegisterID> argumentRegister;
            argumentRegister = expression->emitBytecode(*this, callArguments.argumentRegister(0));
            return emitCallVarargs<typename VarArgsOp<CallOp>::type>(dst, func, callArguments.thisRegister(), argumentRegister.get(), newTemporary(), 0, divot, divotStart, divotEnd, debuggableCall);
        }
        for (; n; n = n->m_next)
            emitNode(callArguments.argumentRegister(argument++), n);
    }
    
    // Reserve space for call frame.
    Vector<RefPtr<RegisterID>, CallFrame::headerSizeInRegisters, UnsafeVectorOverflow> callFrame;
    for (int i = 0; i < CallFrame::headerSizeInRegisters; ++i)
        callFrame.append(newTemporary());

    if (shouldEmitDebugHooks() && debuggableCall == DebuggableCall::Yes)
        emitDebugHook(WillExecuteExpression, divotStart);

    emitExpressionInfo(divot, divotStart, divotEnd);

    Ref<Label> done = newLabel();
    expectedFunction = emitExpectedFunctionSnippet(dst, func, expectedFunction, callArguments, done.get());
    
    if (opcodeID == op_tail_call)
        emitLogShadowChickenTailIfNecessary();
    
    // Emit call.
    ASSERT(dst);
    ASSERT(dst != ignoredResult());
    if constexpr (opcodeID == op_call_direct_eval)
        CallOp::emit(this, dst, func, callArguments.argumentCountIncludingThis(), callArguments.stackOffset(), thisRegister(), scopeRegister(), computeFeaturesForCallDirectEval(), nextValueProfileIndex());
    else if constexpr (opcodeID == op_call_ignore_result) {
        CallOp::emit(this, func, callArguments.argumentCountIncludingThis(), callArguments.stackOffset());
        if (shouldEmitTypeProfilerHooks())
            emitLoad(dst, jsUndefined());
    } else if constexpr (opcodeID == op_tail_call)
        CallOp::emit(this, dst, func, callArguments.argumentCountIncludingThis(), callArguments.stackOffset());
    else
        CallOp::emit(this, dst, func, callArguments.argumentCountIncludingThis(), callArguments.stackOffset(), nextValueProfileIndex());
    
    if (expectedFunction != NoExpectedFunction)
        emitLabel(done.get());

    return dst;
}

RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    return emitCallVarargs<OpCallVarargs>(dst, func, thisRegister, arguments, firstFreeRegister, firstVarArgOffset, divot, divotStart, divotEnd, debuggableCall);
}

RegisterID* BytecodeGenerator::emitCallVarargsInTailPosition(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    if (m_allowTailCallOptimization)
        return emitCallVarargs<OpTailCallVarargs>(dst, func, thisRegister, arguments, firstFreeRegister, firstVarArgOffset, divot, divotStart, divotEnd, debuggableCall);
    return emitCallVarargs<OpCallVarargs>(dst, func, thisRegister, arguments, firstFreeRegister, firstVarArgOffset, divot, divotStart, divotEnd, debuggableCall);
}

RegisterID* BytecodeGenerator::emitConstructVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    return emitCallVarargs<OpConstructVarargs>(dst, func, thisRegister, arguments, firstFreeRegister, firstVarArgOffset, divot, divotStart, divotEnd, debuggableCall);
}

RegisterID* BytecodeGenerator::emitSuperConstructVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    return emitCallVarargs<OpSuperConstructVarargs>(dst, func, thisRegister, arguments, firstFreeRegister, firstVarArgOffset, divot, divotStart, divotEnd, debuggableCall);
}

template<typename VarargsOp>
RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, DebuggableCall debuggableCall)
{
    if (shouldEmitDebugHooks() && debuggableCall == DebuggableCall::Yes)
        emitDebugHook(WillExecuteExpression, divotStart);

    emitExpressionInfo(divot, divotStart, divotEnd);

    if (VarargsOp::opcodeID == op_tail_call_varargs)
        emitLogShadowChickenTailIfNecessary();
    
    // Emit call.
    ASSERT(dst != ignoredResult());
    if constexpr (VarargsOp::opcodeID == op_tail_call_varargs)
        VarargsOp::emit(this, dst, func, thisRegister, arguments ? arguments : VirtualRegister(0), firstFreeRegister, firstVarArgOffset);
    else
        VarargsOp::emit(this, dst, func, thisRegister, arguments ? arguments : VirtualRegister(0), firstFreeRegister, firstVarArgOffset, nextValueProfileIndex());
    ASSERT(m_codeBlock->hasCheckpoints());
    return dst;
}

void BytecodeGenerator::emitLogShadowChickenPrologueIfNecessary()
{
    if (!shouldEmitDebugHooks() && !Options::alwaysUseShadowChicken())
        return;
    OpLogShadowChickenPrologue::emit(this, scopeRegister());
}

void BytecodeGenerator::emitLogShadowChickenTailIfNecessary()
{
    if (!shouldEmitDebugHooks() && !Options::alwaysUseShadowChicken())
        return;
    OpLogShadowChickenTail::emit(this, thisRegister(), scopeRegister());
}

void BytecodeGenerator::emitCallDefineProperty(RegisterID* newObj, RegisterID* propertyNameRegister,
    RegisterID* valueRegister, RegisterID* getterRegister, RegisterID* setterRegister, unsigned options, const JSTextPosition& position)
{
    DefinePropertyAttributes attributes;
    if (options & PropertyConfigurable)
        attributes.setConfigurable(true);

    if (options & PropertyWritable)
        attributes.setWritable(true);
    else if (valueRegister)
        attributes.setWritable(false);

    if (options & PropertyEnumerable)
        attributes.setEnumerable(true);

    if (valueRegister)
        attributes.setValue();
    if (getterRegister)
        attributes.setGet();
    if (setterRegister)
        attributes.setSet();

    ASSERT(!valueRegister || (!getterRegister && !setterRegister));

    emitExpressionInfo(position, position, position);

    if (attributes.hasGet() || attributes.hasSet()) {
        RefPtr<RegisterID> throwTypeErrorFunction;
        if (!attributes.hasGet() || !attributes.hasSet())
            throwTypeErrorFunction = moveLinkTimeConstant(nullptr, LinkTimeConstant::throwTypeErrorFunction);

        RefPtr<RegisterID> getter;
        if (attributes.hasGet())
            getter = getterRegister;
        else
            getter = throwTypeErrorFunction;

        RefPtr<RegisterID> setter;
        if (attributes.hasSet())
            setter = setterRegister;
        else
            setter = throwTypeErrorFunction;

        OpDefineAccessorProperty::emit(this, newObj, propertyNameRegister, getter.get(), setter.get(), emitLoad(nullptr, jsNumber(attributes.rawRepresentation())));
    } else {
        OpDefineDataProperty::emit(this, newObj, propertyNameRegister, valueRegister, emitLoad(nullptr, jsNumber(attributes.rawRepresentation())));
    }
}

RegisterID* BytecodeGenerator::emitReturn(RegisterID* src)
{
    // Normal functions and naked constructors do not handle `return` specially.
    if (isConstructor() && constructorKind() != ConstructorKind::Naked) {
        bool isDerived = constructorKind() == ConstructorKind::Extends;
        bool srcIsThis = src->index() == m_thisRegister.index();

        if (!srcIsThis) {
            Ref<Label> isObjectLabel = newLabel();
            emitJumpIfTrue(emitIsObject(newTemporary(), src), isObjectLabel.get());

            if (isDerived) {
                Ref<Label> isUndefinedLabel = newLabel();
                emitJumpIfTrue(emitIsUndefined(newTemporary(), src), isUndefinedLabel.get());

                ASSERT(m_scopeNode->isFunctionNode());
                String className = static_cast<FunctionNode*>(m_scopeNode)->ident().string();
                if (!className || className.isEmpty())
                    emitThrowTypeError("Cannot return a non-object type in the constructor of a derived class."_s);
                else {
                    auto errorMessageStr = tryMakeString("Cannot return a non-object type in the constructor of a derived class "_s, className, "."_s);
                    if (!errorMessageStr) [[unlikely]]
                        emitThrowTypeError("Cannot return a non-object type in the constructor of a derived class."_s);
                    else
                        emitThrowTypeError(Identifier::fromString(m_vm, errorMessageStr));
                }

                emitLabel(isUndefinedLabel.get());
            }

            OpRet::emit(this, ensureThis());
            emitLabel(isObjectLabel.get());
        }
    }

    OpRet::emit(this, src);
    return src;
}

template<typename ConstructOp>
RegisterID* BytecodeGenerator::emitConstructImpl(RegisterID* dst, RegisterID* func, RegisterID* lazyThis, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, bool isDefaultDerivedConstructorCall)
{
    ASSERT(func->refCount());

    // Generate code for arguments.
    unsigned argument = 0;
    if (ArgumentsNode* argumentsNode = callArguments.argumentsNode()) {

        ArgumentListNode* n = callArguments.argumentsNode()->m_listNode;
        if (n && n->m_expr->isSpreadExpression()) {
            RELEASE_ASSERT(!n->m_next);
            auto expression = static_cast<SpreadExpressionNode*>(n->m_expr)->expression();
            if (expression->isArrayLiteral()) {
                auto* elements = static_cast<ArrayNode*>(expression)->elements();
                if (elements && !elements->next() && elements->value()->isSpreadExpression()) {
                    auto* spread = static_cast<SpreadExpressionNode*>(elements->value());
                    ExpressionNode* expression = spread->expression();
                    RefPtr<RegisterID> argumentRegister = tempDestination(emitNode(callArguments.argumentRegister(0), expression));

                    if (!isDefaultDerivedConstructorCall) {
                        emitExpressionInfo(spread->divot(), spread->divotStart(), spread->divotEnd());
                        OpSpread::emit(this, argumentRegister.get(), argumentRegister.get());
                    }

                    move(callArguments.thisRegister(), lazyThis);
                    return emitCallVarargs<typename VarArgsOp<ConstructOp>::type>(dst, func, callArguments.thisRegister(), argumentRegister.get(), newTemporary(), 0, divot, divotStart, divotEnd, DebuggableCall::No);
                }
            }
            RefPtr<RegisterID> argumentRegister;
            argumentRegister = expression->emitBytecode(*this, callArguments.argumentRegister(0));
            move(callArguments.thisRegister(), lazyThis);
            return emitCallVarargs<typename VarArgsOp<ConstructOp>::type>(dst, func, callArguments.thisRegister(), argumentRegister.get(), newTemporary(), 0, divot, divotStart, divotEnd, DebuggableCall::No);
        }

        for (ArgumentListNode* n = argumentsNode->m_listNode; n; n = n->m_next)
            emitNode(callArguments.argumentRegister(argument++), n);
    }

    move(callArguments.thisRegister(), lazyThis);

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

    emitExpressionInfo(divot, divotStart, divotEnd);

    Ref<Label> done = newLabel();
    expectedFunction = emitExpectedFunctionSnippet(dst, func, expectedFunction, callArguments, done.get());

    ConstructOp::emit(this, dst, func, callArguments.argumentCountIncludingThis(), callArguments.stackOffset(), nextValueProfileIndex());

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

    return dst;
}

RegisterID* BytecodeGenerator::emitConstruct(RegisterID* dst, RegisterID* func, RegisterID* lazyThis, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
{
    return emitConstructImpl<OpConstruct>(dst, func, lazyThis, expectedFunction, callArguments, divot, divotStart, divotEnd, false);
}

RegisterID* BytecodeGenerator::emitSuperConstruct(RegisterID* dst, RegisterID* func, RegisterID* lazyThis, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd, bool isDefaultDerivedConstructorCall)
{
    return emitConstructImpl<OpSuperConstruct>(dst, func, lazyThis, expectedFunction, callArguments, divot, divotStart, divotEnd, isDefaultDerivedConstructorCall);
}

RegisterID* BytecodeGenerator::emitStrcat(RegisterID* dst, RegisterID* src, int count)
{
    OpStrcat::emit(this, dst, src, count);
    return dst;
}

void BytecodeGenerator::emitToPrimitive(RegisterID* dst, RegisterID* src)
{
    OpToPrimitive::emit(this, dst, src);
}

RegisterID* BytecodeGenerator::emitToPropertyKey(RegisterID* dst, RegisterID* src)
{
    OpToPropertyKey::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitToPropertyKeyOrNumber(RegisterID* dst, RegisterID* src)
{
    OpToPropertyKeyOrNumber::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitPushWithScope(RegisterID* objectScope)
{
    pushLocalControlFlowScope();
    RegisterID* newScope = newBlockScopeVariable();
    newScope->ref();

    OpPushWithScope::emit(this, newScope, scopeRegister(), objectScope);

    move(scopeRegister(), newScope);
    m_lexicalScopeStack.append({ nullptr, newScope, true, 0 });

    return newScope;
}

RegisterID* BytecodeGenerator::emitGetParentScope(RegisterID* dst, RegisterID* scope)
{
    OpGetParentScope::emit(this, dst, scope);
    return dst;
}

void BytecodeGenerator::emitPopWithScope()
{
    emitGetParentScope(scopeRegister(), scopeRegister());
    popLocalControlFlowScope();
    auto stackEntry = m_lexicalScopeStack.takeLast();
    stackEntry.m_scope->deref();
    RELEASE_ASSERT(stackEntry.m_isWithScope);
}

void BytecodeGenerator::emitDebugHook(DebugHookType debugHookType, const JSTextPosition& divot, RegisterID* data)
{
    if (!shouldEmitDebugHooks()) [[likely]]
        return;

    if (m_lastDebugHook.position == divot && m_lastDebugHook.type == debugHookType)
        return;

    m_lastDebugHook.position = divot;
    m_lastDebugHook.type = debugHookType;

    emitExpressionInfo(divot, divot, divot);

    if (!data)
        data = emitLoad(nullptr, jsUndefined());
    OpDebug::emit(this, debugHookType, data);
}

void BytecodeGenerator::emitDebugHook(StatementNode* statement, RegisterID* data)
{
    // DebuggerStatementNode will output its own special debug hook.
    if (statement->isDebuggerStatement())
        return;

    emitDebugHook(WillExecuteStatement, statement->position(), data);
}

void BytecodeGenerator::emitDebugHook(ExpressionNode* expr, RegisterID* data)
{
    emitDebugHook(WillExecuteStatement, expr->position(), data);
}

void BytecodeGenerator::emitWillLeaveCallFrameDebugHook()
{
    emitDebugHook(WillLeaveCallFrame, JSTextPosition(m_scopeNode->lastLine(), m_scopeNode->startOffset(), m_scopeNode->lineStartOffset()));
}

void BytecodeGenerator::pushFinallyControlFlowScope(FinallyContext& finallyContext)
{
    ControlFlowScope scope(ControlFlowScope::Finally, currentLexicalScopeIndex(), &finallyContext);
    m_controlFlowScopeStack.append(WTF::move(scope));

    m_finallyDepth++;
    m_currentFinallyContext = &finallyContext;
}

void BytecodeGenerator::popFinallyControlFlowScope()
{
    ASSERT(m_controlFlowScopeStack.size());
    ASSERT(m_controlFlowScopeStack.last().isFinallyScope());
    ASSERT(m_finallyDepth > 0);
    ASSERT(m_currentFinallyContext);
    m_currentFinallyContext = m_currentFinallyContext->outerContext();
    m_finallyDepth--;
    m_controlFlowScopeStack.removeLast();
}

LabelScope* BytecodeGenerator::breakTarget(const Identifier& name)
{
    shrinkToFit(m_labelScopes);

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

    // 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)
                return &scope;
        }
        return nullptr;
    }

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

LabelScope* BytecodeGenerator::continueTarget(const Identifier& name)
{
    shrinkToFit(m_labelScopes);

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

    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 nullptr;
    }

    // Continue to the loop nested nearest to the label scope that matches
    // 'name'.
    LabelScope* result = nullptr;
    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 null.
    }
    return nullptr;
}

void BytecodeGenerator::allocateScope()
{
    m_scopeRegister = addVar();
    m_scopeRegister->ref();
    m_codeBlock->setScopeRegister(scopeRegister()->virtualRegister());
}

TryData* BytecodeGenerator::pushTry(Label& start, Label& handlerLabel, HandlerType handlerType)
{
    m_tryData.append(TryData { handlerLabel, handlerType });
    TryData* result = &m_tryData.last();
    
    m_tryContextStack.append(TryContext {
        start,
        result
    });
    
    return result;
}

void BytecodeGenerator::popTry(TryData* tryData, Label& end)
{
    m_usesExceptions = true;
    
    ASSERT_UNUSED(tryData, m_tryContextStack.last().tryData == tryData);
    
    m_tryRanges.append(TryRange {
        m_tryContextStack.last().start.copyRef(),
        end,
        m_tryContextStack.last().tryData
    });
    m_tryContextStack.removeLast();
}

void BytecodeGenerator::emitOutOfLineCatchHandler(RegisterID* thrownValueRegister, RegisterID* completionTypeRegister, TryData* data)
{
    RegisterID* unused = newTemporary();
    emitOutOfLineExceptionHandler(unused, thrownValueRegister, completionTypeRegister, data);
}

void BytecodeGenerator::emitOutOfLineFinallyHandler(RegisterID* exceptionRegister, RegisterID* completionTypeRegister, TryData* data)
{
    RegisterID* unused = newTemporary();
    ASSERT(completionTypeRegister);
    emitOutOfLineExceptionHandler(exceptionRegister, unused, completionTypeRegister, data);
}

void BytecodeGenerator::emitOutOfLineExceptionHandler(RegisterID* exceptionRegister, RegisterID* thrownValueRegister, RegisterID* completionTypeRegister, TryData* data)
{
    VirtualRegister completionTypeVirtualRegister = completionTypeRegister ? completionTypeRegister : VirtualRegister();
    m_exceptionHandlersToEmit.append({ data, exceptionRegister, thrownValueRegister, completionTypeVirtualRegister });
}

void BytecodeGenerator::restoreScopeRegister(int lexicalScopeIndex)
{
    if (lexicalScopeIndex == CurrentLexicalScopeIndex)
        return; // No change needed.

    if (lexicalScopeIndex != OutermostLexicalScopeIndex) {
        ASSERT(lexicalScopeIndex < static_cast<int>(m_lexicalScopeStack.size()));
        int endIndex = lexicalScopeIndex + 1;
        for (size_t i = endIndex; i--; ) {
            if (m_lexicalScopeStack[i].m_scope) {
                move(scopeRegister(), m_lexicalScopeStack[i].m_scope);
                return;
            }
        }
    }
    // Note that if we don't find a local scope in the current function/program,
    // we must grab the outer-most scope of this bytecode generation.
    if (m_topLevelScopeRegister)
        move(scopeRegister(), m_topLevelScopeRegister);
    else
        OpGetScope::emit(this, scopeRegister());
}

void BytecodeGenerator::restoreScopeRegister()
{
    restoreScopeRegister(currentLexicalScopeIndex());
}

int BytecodeGenerator::labelScopeDepthToLexicalScopeIndex(int targetLabelScopeDepth)
{
    ASSERT(labelScopeDepth() - targetLabelScopeDepth >= 0);
    size_t scopeDelta = labelScopeDepth() - targetLabelScopeDepth;
    ASSERT(scopeDelta <= m_controlFlowScopeStack.size());
    if (!scopeDelta)
        return CurrentLexicalScopeIndex;

    ControlFlowScope& targetScope = m_controlFlowScopeStack[targetLabelScopeDepth];
    return targetScope.lexicalScopeIndex;
}

void BytecodeGenerator::emitThrow(RegisterID* exc)
{
    m_usesExceptions = true;
    OpThrow::emit(this, exc);
}

RegisterID* BytecodeGenerator::emitArgumentCount(RegisterID* dst)
{
    OpArgumentCount::emit(this, dst);
    return dst;
}

unsigned BytecodeGenerator::localScopeDepth() const
{
    return m_localScopeDepth;
}

int BytecodeGenerator::labelScopeDepth() const
{
    unsigned depth = localScopeDepth() + m_finallyDepth;
    ASSERT(depth == m_controlFlowScopeStack.size());
    return depth;
}

void BytecodeGenerator::emitThrowStaticError(ErrorTypeWithExtension errorType, RegisterID* raw)
{
    RefPtr<RegisterID> message = newTemporary();
    emitToString(message.get(), raw);
    OpThrowStaticError::emit(this, message.get(), errorType);
}

void BytecodeGenerator::emitThrowStaticError(ErrorTypeWithExtension errorType, const Identifier& message)
{
    OpThrowStaticError::emit(this, addConstantValue(addStringConstant(message)), errorType);
}

void BytecodeGenerator::emitThrowReferenceError(ASCIILiteral message)
{
    emitThrowStaticError(ErrorTypeWithExtension::ReferenceError, Identifier::fromString(m_vm, message));
}

void BytecodeGenerator::emitThrowTypeError(ASCIILiteral message)
{
    emitThrowStaticError(ErrorTypeWithExtension::TypeError, Identifier::fromString(m_vm, message));
}

void BytecodeGenerator::emitThrowTypeError(const Identifier& message)
{
    emitThrowStaticError(ErrorTypeWithExtension::TypeError, message);
}

void BytecodeGenerator::emitThrowRangeError(const Identifier& message)
{
    emitThrowStaticError(ErrorTypeWithExtension::RangeError, message);
}

void BytecodeGenerator::emitThrowOutOfMemoryError()
{
    emitThrowStaticError(ErrorTypeWithExtension::OutOfMemoryError, m_vm.propertyNames->emptyIdentifier);
}

void BytecodeGenerator::emitPushFunctionNameScope(const Identifier& property, RegisterID* callee, bool isCaptured)
{
    // There is some nuance here:
    // If we're in strict mode code, the function name scope variable acts exactly like a "const" variable.
    // If we're not in strict mode code, we want to allow bogus assignments to the name scoped variable.
    // This means any assignment to the variable won't throw, but it won't actually assign a new value to it.
    // To accomplish this, we don't report that this scope is a lexical scope. This will prevent
    // any throws when trying to assign to the variable (while still ensuring it keeps its original
    // value). There is some ugliness and exploitation of a leaky abstraction here, but it's better than 
    // having a completely new op code and a class to handle name scopes which are so close in functionality
    // to lexical environments.
    VariableEnvironment nameScopeEnvironment;
    auto addResult = nameScopeEnvironment.add(property);
    if (isCaptured)
        addResult.iterator->value.setIsCaptured();
    addResult.iterator->value.setIsConst(); // The function name scope name acts like a const variable.
    unsigned numVars = m_codeBlock->numVars();
    pushLexicalScopeInternal(nameScopeEnvironment, TDZCheckOptimization::Optimize, NestedScopeType::IsNotNested, nullptr, TDZRequirement::NotUnderTDZ, ScopeType::FunctionNameScope, ScopeRegisterType::Var);
    ASSERT_UNUSED(numVars, m_codeBlock->numVars() == numVars + 1); // Should have only created one new "var" for the function name scope.
    bool shouldTreatAsLexicalVariable = ecmaMode().isStrict();
    Variable functionVar = variableForLocalEntry(property, m_lexicalScopeStack.last().m_symbolTable->get(NoLockingNecessary, property.impl()), m_lexicalScopeStack.last().m_symbolTableConstantIndex, shouldTreatAsLexicalVariable);
    emitPutToScope(m_lexicalScopeStack.last().m_scope, functionVar, callee, ThrowIfNotFound, InitializationMode::NotInitialization);
}

void BytecodeGenerator::pushLocalControlFlowScope()
{
    ControlFlowScope scope(ControlFlowScope::Label, currentLexicalScopeIndex());
    m_controlFlowScopeStack.append(WTF::move(scope));
    m_localScopeDepth++;
    m_localScopeCount++;
}

void BytecodeGenerator::popLocalControlFlowScope()
{
    ASSERT(m_controlFlowScopeStack.size());
    ASSERT(!m_controlFlowScopeStack.last().isFinallyScope());
    m_controlFlowScopeStack.removeLast();
    m_localScopeDepth--;
}

void BytecodeGenerator::emitPushCatchScope(VariableEnvironment& environment, ScopeType scopeType)
{
    pushLexicalScopeInternal(environment, TDZCheckOptimization::Optimize, NestedScopeType::IsNotNested, nullptr, TDZRequirement::UnderTDZ, scopeType, ScopeRegisterType::Block);
}

void BytecodeGenerator::emitPopCatchScope(VariableEnvironment& environment) 
{
    popLexicalScopeInternal(environment);
}

void BytecodeGenerator::beginSwitch(RegisterID* scrutineeRegister, SwitchInfo::SwitchType type)
{
    switch (type) {
    case SwitchInfo::SwitchType::Immediate:
    case SwitchInfo::SwitchType::ImmediateList: {
        size_t tableIndex = m_codeBlock->numberOfUnlinkedSwitchJumpTables();
        m_codeBlock->addUnlinkedSwitchJumpTable();
        OpSwitchImm::emit(this, tableIndex, scrutineeRegister);
        break;
    }
    case SwitchInfo::SwitchType::Character:
    case SwitchInfo::SwitchType::CharacterList: {
        size_t tableIndex = m_codeBlock->numberOfUnlinkedSwitchJumpTables();
        m_codeBlock->addUnlinkedSwitchJumpTable();
        OpSwitchChar::emit(this, tableIndex, scrutineeRegister);
        break;
    }
    case SwitchInfo::SwitchType::String: {
        size_t tableIndex = m_codeBlock->numberOfUnlinkedStringSwitchJumpTables();
        m_codeBlock->addUnlinkedStringSwitchJumpTable();
        OpSwitchString::emit(this, tableIndex, scrutineeRegister);
        break;
    }
    case SwitchInfo::SwitchType::None:
        RELEASE_ASSERT_NOT_REACHED();
    }

    SwitchInfo info = { m_lastInstruction.offset(), type };
    m_switchContextStack.append(info);
}

void BytecodeGenerator::endSwitch(const Vector<Ref<Label>, 8>& labels, ExpressionNode** nodes, Label& defaultLabel, int32_t min, int32_t max)
{
    SwitchInfo switchInfo = m_switchContextStack.last();
    m_switchContextStack.removeLast();

    auto handleSwitch = [&](auto bytecode) {
        UnlinkedSimpleJumpTable& jumpTable = m_codeBlock->unlinkedSwitchJumpTable(bytecode.m_tableIndex);
        jumpTable.m_min = min;
        jumpTable.m_branchOffsets = FixedVector<int32_t>(max - min + 1);
        std::ranges::fill(jumpTable.m_branchOffsets, 0);
        for (uint32_t i = 0; i < labels.size(); ++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());
            int32_t key = 0;
            if (switchInfo.switchType == SwitchInfo::SwitchType::Immediate) {
                ASSERT(nodes[i]->isNumber());
                double value = static_cast<NumberNode*>(nodes[i])->value();
                int32_t extracted = static_cast<int32_t>(value);
                ASSERT(extracted == value);
                ASSERT(extracted >= min);
                ASSERT(extracted <= max);
                key = extracted - min;
            } else {
                ASSERT(nodes[i]->isString());
                StringImpl* clause = static_cast<StringNode*>(nodes[i])->value().impl();
                ASSERT(clause->length() == 1);
                int32_t extracted = (*clause)[0];
                ASSERT(extracted >= min);
                ASSERT(extracted <= max);
                key = extracted - min;
            }
            jumpTable.add(key, labels[i]->bind(switchInfo.bytecodeOffset));
        }
        ASSERT(!defaultLabel.isForward());
        jumpTable.m_defaultOffset = defaultLabel.bind(switchInfo.bytecodeOffset);
    };

    auto handleSwitchList = [&](auto bytecode) {
        UnlinkedSimpleJumpTable& jumpTable = m_codeBlock->unlinkedSwitchJumpTable(bytecode.m_tableIndex);
        jumpTable.m_min = INT32_MAX;
        jumpTable.m_isList = true;

        Vector<int32_t> branchOffsets;
        branchOffsets.reserveInitialCapacity(labels.size() * 2);
        UncheckedKeyHashSet<GenericHashKey<int32_t>> alreadyHandled;

        for (uint32_t i = 0; i < labels.size(); ++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());
            int32_t key = 0;
            if (switchInfo.switchType == SwitchInfo::SwitchType::ImmediateList) {
                double value = static_cast<NumberNode*>(nodes[i])->value();
                key = static_cast<int32_t>(value);
            } else {
                StringImpl* clause = static_cast<StringNode*>(nodes[i])->value().impl();
                ASSERT(clause->length() == 1);
                key = (*clause)[0];
            }

            // There is a chance that we may list up duplicate keys. In this case, the first one wins.
            if (!alreadyHandled.add(key).isNewEntry)
                continue;

            branchOffsets.append(key);
            branchOffsets.append(labels[i]->bind(switchInfo.bytecodeOffset));
        }

        ASSERT(!defaultLabel.isForward());
        jumpTable.m_branchOffsets = WTF::move(branchOffsets);
        jumpTable.m_defaultOffset = defaultLabel.bind(switchInfo.bytecodeOffset);
    };

    auto handleStringSwitch = [&](auto bytecode) {
        UnlinkedStringJumpTable& jumpTable = m_codeBlock->unlinkedStringSwitchJumpTable(bytecode.m_tableIndex);
        for (uint32_t i = 0; i < labels.size(); ++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());
            UniquedStringImpl* clause = static_cast<StringNode*>(nodes[i])->value().impl();
            ASSERT(clause->isAtom());
            auto result = jumpTable.m_offsetTable.add(clause, UnlinkedStringJumpTable::OffsetLocation { labels[i]->bind(switchInfo.bytecodeOffset), 0 });
            if (result.isNewEntry) {
                result.iterator->value.m_indexInTable = jumpTable.m_offsetTable.size() - 1;
                jumpTable.m_minLength = std::min(jumpTable.m_minLength, clause->length());
                jumpTable.m_maxLength = std::max(jumpTable.m_maxLength, clause->length());
            }
        }
        ASSERT(!defaultLabel.isForward());
        jumpTable.m_defaultOffset = defaultLabel.bind(switchInfo.bytecodeOffset);

        if (jumpTable.m_offsetTable.isEmpty()) {
            jumpTable.m_minLength = 0;
            jumpTable.m_maxLength = 0;
        }
    };

    auto ref = m_writer.ref(switchInfo.bytecodeOffset);
    switch (switchInfo.switchType) {
    case SwitchInfo::SwitchType::Immediate: {
        handleSwitch(ref->as<OpSwitchImm>());
        break;
    }

    case SwitchInfo::SwitchType::ImmediateList: {
        handleSwitchList(ref->as<OpSwitchImm>());
        break;
    }

    case SwitchInfo::SwitchType::Character: {
        handleSwitch(ref->as<OpSwitchChar>());
        break;
    }

    case SwitchInfo::SwitchType::CharacterList: {
        handleSwitchList(ref->as<OpSwitchChar>());
        break;
    }

    case SwitchInfo::SwitchType::String: {
        handleStringSwitch(ref->as<OpSwitchString>());
        break;
    }

    case SwitchInfo::SwitchType::None:
        RELEASE_ASSERT_NOT_REACHED();
        break;
    }
}

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();
}

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

bool BytecodeGenerator::emitReadOnlyExceptionIfNeeded(const Variable& variable)
{
    // If we're in strict mode, we always throw.
    // If we're not in strict mode, we throw for "const" variables but not the function callee.
    if (ecmaMode().isStrict() || variable.isConst()) {
        emitThrowTypeError(Identifier::fromString(m_vm, ReadonlyPropertyWriteError));
        return true;
    }
    return false;
}

void BytecodeGenerator::emitTryWithFinallyThatDoesNotShadowException(const ScopedLambda<void(BytecodeGenerator&)>& emitTry, const ScopedLambda<void(BytecodeGenerator&)>& emitFinally)
{
    Ref<Label> finallyLabel = newLabel();
    FinallyContext finallyContext(*this, finallyLabel.get());
    pushFinallyControlFlowScope(finallyContext);
    emitTryWithFinallyThatDoesNotShadowException(finallyContext, emitTry, emitFinally);
    popFinallyControlFlowScope();
}

void BytecodeGenerator::emitTryWithFinallyThatDoesNotShadowException(FinallyContext& finallyContext, const ScopedLambda<void(BytecodeGenerator&)>& emitTry, const ScopedLambda<void(BytecodeGenerator&)>& emitFinally)
{
    Ref<Label> tryStartLabel = newEmittedLabel();
    TryData* tryData = pushTry(tryStartLabel.get(), *finallyContext.finallyLabel(), HandlerType::SynthesizedFinally);
    emitTry(*this);
    Ref<Label> tryEndLabel = newEmittedLabel();
    popTry(tryData, tryEndLabel.get());

    {
        Ref<Label> done = newLabel();

        emitLabel(*finallyContext.finallyLabel());
        emitOutOfLineFinallyHandler(finallyContext.completionValueRegister(), finallyContext.completionTypeRegister(), tryData);

        Ref<Label> tryInFinallyStartLabel = newEmittedLabel();
        Ref<Label> catchInFinallyLabel = newLabel();
        TryData* tryInFinallyData = pushTry(tryInFinallyStartLabel.get(), catchInFinallyLabel.get(), HandlerType::SynthesizedCatch);
        emitFinally(*this);
        Ref<Label> tryInFinallyEndLabel = newEmittedLabel();
        popTry(tryInFinallyData, tryInFinallyEndLabel.get());

        emitFinallyCompletion(finallyContext, done.get());

        // Catch block for exceptions that may be thrown while executing the finally block.
        // The only reason we need this catch block is because if the above finally block
        // is entered due to a thrown exception, then we want to rethrow the original exception
        // on exiting the finally block. Otherwise, we would let any new exception pass through.
        {
            emitLabel(catchInFinallyLabel.get());

            RefPtr<RegisterID> exceptionRegister = newTemporary();
            emitOutOfLineCatchHandler(exceptionRegister.get(), nullptr, tryInFinallyData);
            // Since this is a synthesized catch block and we are guaranteed to never need to
            // resolve any symbols from the scope, we can skip restoring the scope register here.

            emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), finallyContext.completionTypeRegister(), emitLoad(nullptr, CompletionType::Throw)), tryInFinallyEndLabel.get());
            emitThrow(exceptionRegister.get());
        }

        emitLabel(done.get());
    }
}

void BytecodeGenerator::emitPrepareDisposable(RegisterID* value, const JSTextPosition& divot, bool isAsync)
{
    auto& usingScope = currentUsingScope();
    ASSERT(usingScope.nextSlot < usingScope.slots.size());
    auto& slot = usingScope.slots[usingScope.nextSlot++];
    slot.isAsync = isAsync;
    move(slot.value.get(), value);

    RefPtr<RegisterID> getDisposeMethodFunc = moveLinkTimeConstant(nullptr, isAsync ? LinkTimeConstant::getAsyncDisposeMethod : LinkTimeConstant::getDisposeMethod);
    CallArguments args(*this, nullptr, 1);
    emitLoad(args.thisRegister(), jsUndefined());
    move(args.argumentRegister(0), value);
    emitCall(slot.method.get(), getDisposeMethodFunc.get(), NoExpectedFunction, args, divot, divot, divot, DebuggableCall::No);

    // Mark reached only after method lookup succeeds; if the above call threw, reached stays
    // false so the finally block skips this slot entirely (spec: no resource record is added).
    if (isAsync) {
        ASSERT(usingScope.hasAwaitUsing);
        ASSERT(slot.reached);
        emitLoad(slot.reached.get(), jsBoolean(true));
    }
}

void BytecodeGenerator::emitUsingBodyScope(unsigned usingCount, bool hasAwaitUsing, const ScopedLambda<void(BytecodeGenerator&)>& emitBody)
{
    ASSERT(!hasAwaitUsing || isAsyncFunctionParseMode(parseMode()) || isModuleParseMode(parseMode()));

    // Pre-allocate slots and initialize method registers to undefined BEFORE the try block.
    // This ensures that if an initializer throws, the method register has a known value (undefined)
    // so the finally block can safely check it.
    m_usingScopeStack.append(UsingScope { });
    auto& usingScope = currentUsingScope();
    usingScope.hasAwaitUsing = hasAwaitUsing;
    for (unsigned i = 0; i < usingCount; i++) {
        RefPtr<RegisterID> valueCopy = newTemporary();
        RefPtr<RegisterID> method = newTemporary();
        RefPtr<RegisterID> reached;
        emitLoad(valueCopy.get(), jsUndefined());
        emitLoad(method.get(), jsUndefined());
        if (hasAwaitUsing) {
            reached = newTemporary();
            emitLoad(reached.get(), jsBoolean(false));
        }
        usingScope.slots.append({ valueCopy, method, reached, false });
    }

    RefPtr<RegisterID> thrownValue = newTemporary();
    emitLoad(thrownValue.get(), jsUndefined());

    Ref<Label> finallyLabel = newLabel();
    FinallyContext finallyContext(*this, finallyLabel.get());
    pushFinallyControlFlowScope(finallyContext);

    Ref<Label> tryStartLabel = newEmittedLabel();
    TryData* tryData = pushTry(tryStartLabel.get(), *finallyContext.finallyLabel(), HandlerType::SynthesizedFinally);
    emitBody(*this);
    Ref<Label> tryEndLabel = newEmittedLabel();
    popTry(tryData, tryEndLabel.get());

    // Finally block: unrolled dispose calls in reverse order.
    {
        Ref<Label> done = newLabel();

        emitLabel(*finallyContext.finallyLabel());
        emitOutOfLineExceptionHandler(finallyContext.completionValueRegister(), thrownValue.get(), finallyContext.completionTypeRegister(), tryData);

        RefPtr<RegisterID> pendingError = newTemporary();
        RefPtr<RegisterID> hasError = newTemporary();
        RefPtr<RegisterID> disposeThrew = newTemporary();
        emitLoad(pendingError.get(), jsUndefined());
        emitLoad(hasError.get(), jsBoolean(false));
        emitLoad(disposeThrew.get(), jsBoolean(false));

        // If body threw, seed pendingError with the thrown value.
        {
            Ref<Label> afterInit = newLabel();
            emitJumpIfFalse(emitEqualityOp<OpStricteq>(newTemporary(), finallyContext.completionTypeRegister(), emitLoad(nullptr, CompletionType::Throw)), afterInit.get());
            move(pendingError.get(), thrownValue.get());
            emitLoad(hasError.get(), jsBoolean(true));
            emitLabel(afterInit.get());
        }

        JSTextPosition divot(m_scopeNode->firstLine(), m_scopeNode->startOffset(), m_scopeNode->lineStartOffset());

        // Async disposal state (per DisposeResources spec): needsAwait / hasAwaited.
        // Only allocated when this scope contains at least one await using declaration.
        RefPtr<RegisterID> needsAwait;
        RefPtr<RegisterID> hasAwaited;
        if (hasAwaitUsing) {
            needsAwait = newTemporary();
            hasAwaited = newTemporary();
            emitLoad(needsAwait.get(), jsBoolean(false));
            emitLoad(hasAwaited.get(), jsBoolean(false));
        }

        // Shared temporaries for the catch handler (one pair is enough across all slots).
        RefPtr<RegisterID> caughtException = newTemporary();
        RefPtr<RegisterID> caughtValue = newTemporary();
        RefPtr<RegisterID> suppressedErrorCtor = newTemporary();

        auto emitSuppressedErrorCatch = [&](TryData* trySlotData, Label& catchLabel) {
            emitLabel(catchLabel);
            emitOutOfLineExceptionHandler(caughtException.get(), caughtValue.get(), nullptr, trySlotData);

            Ref<Label> afterCatch = newLabel();
            Ref<Label> firstError = newLabel();
            emitJumpIfFalse(hasError.get(), firstError.get());

            moveLinkTimeConstant(suppressedErrorCtor.get(), LinkTimeConstant::SuppressedError);
            CallArguments seArgs(*this, nullptr, 2);
            move(seArgs.argumentRegister(0), caughtValue.get());
            move(seArgs.argumentRegister(1), pendingError.get());
            emitConstruct(pendingError.get(), suppressedErrorCtor.get(), suppressedErrorCtor.get(), NoExpectedFunction, seArgs, divot, divot, divot);
            emitJump(afterCatch.get());

            emitLabel(firstError.get());
            move(pendingError.get(), caughtValue.get());
            emitLoad(hasError.get(), jsBoolean(true));

            emitLabel(afterCatch.get());
            emitLoad(disposeThrew.get(), jsBoolean(true));
        };

        auto emitAwaitUndefined = [&]() {
            RefPtr<RegisterID> tmp = newTemporary();
            emitLoad(tmp.get(), jsUndefined());
            emitAwait(tmp.get(), tmp.get(), divot);
        };

        // Dispose each resource in reverse declaration order.
        // Track whether we've processed an async slot so far: needsAwait can only become
        // true after an async slot's null-value case, so Step 3.d before the first async
        // slot in disposal order is always dead and can be elided at compile time.
        bool sawAsyncSlotInDisposalOrder = false;
        for (auto& slot : usingScope.slots | std::views::reverse) {
            Ref<Label> skipSlot = newLabel();

            if (slot.isAsync) {
                sawAsyncSlotInDisposalOrder = true;
                // Async disposal slot.
                // If the declaration was never reached (reached == false), skip entirely
                // without setting needsAwait; the spec only adds a resource record on evaluation.
                emitJumpIfFalse(slot.reached.get(), skipSlot.get());

                Ref<Label> methodDefined = newLabel();
                emitJumpIfFalse(emitIsUndefined(newTemporary(), slot.method.get()), methodDefined.get());

                // method is undefined (await using x = null/undefined).
                // Per DisposeResources step 3.f: set needsAwait to true, no call.
                emitLoad(needsAwait.get(), jsBoolean(true));
                emitJump(skipSlot.get());

                // method is defined: call it and Await the result.
                emitLabel(methodDefined.get());
                Ref<Label> catchLabel = newLabel();
                Ref<Label> trySlotStart = newEmittedLabel();
                TryData* trySlotData = pushTry(trySlotStart.get(), catchLabel.get(), HandlerType::SynthesizedCatch);

                RefPtr<RegisterID> result = newTemporary();
                CallArguments disposeArgs(*this, nullptr, 0);
                move(disposeArgs.thisRegister(), slot.value.get());
                emitCall(result.get(), slot.method.get(), NoExpectedFunction, disposeArgs, divot, divot, divot, DebuggableCall::No);

                // Set hasAwaited before Await: emitAwait throws on rejection, but a rejected
                // Await still implies a microtask boundary has occurred.
                emitLoad(hasAwaited.get(), jsBoolean(true));
                emitAwait(result.get(), result.get(), divot);

                Ref<Label> trySlotEnd = newEmittedLabel();
                popTry(trySlotData, trySlotEnd.get());
                emitJump(skipSlot.get());

                emitSuppressedErrorCatch(trySlotData, catchLabel.get());
            } else {
                // Sync disposal slot.
                // Per DisposeResources step 3.d: if needsAwait && !hasAwaited, Await(undefined) first.
                // Only emit if an async slot was already processed (otherwise needsAwait is provably false).
                if (sawAsyncSlotInDisposalOrder) {
                    Ref<Label> skipAwaitCheck = newLabel();
                    emitJumpIfFalse(needsAwait.get(), skipAwaitCheck.get());
                    emitJumpIfTrue(hasAwaited.get(), skipAwaitCheck.get());
                    emitAwaitUndefined();
                    emitLoad(needsAwait.get(), jsBoolean(false));
                    emitLabel(skipAwaitCheck.get());
                }

                emitJumpIfTrue(emitIsUndefined(newTemporary(), slot.method.get()), skipSlot.get());

                Ref<Label> catchLabel = newLabel();
                Ref<Label> trySlotStart = newEmittedLabel();
                TryData* trySlotData = pushTry(trySlotStart.get(), catchLabel.get(), HandlerType::SynthesizedCatch);

                CallArguments disposeArgs(*this, nullptr, 0);
                move(disposeArgs.thisRegister(), slot.value.get());
                emitCallIgnoreResult(newTemporary(), slot.method.get(), NoExpectedFunction, disposeArgs, divot, divot, divot, DebuggableCall::No);

                Ref<Label> trySlotEnd = newEmittedLabel();
                popTry(trySlotData, trySlotEnd.get());
                emitJump(skipSlot.get());

                emitSuppressedErrorCatch(trySlotData, catchLabel.get());
            }

            emitLabel(skipSlot.get());
        }

        // Per DisposeResources step 6: trailing Await(undefined) if needsAwait && !hasAwaited.
        // If the first-declared slot is sync, its Step 3.d (above) already consumed any pending
        // needsAwait, so this trailing check is provably dead and elided.
        if (hasAwaitUsing && usingScope.slots[0].isAsync) {
            Ref<Label> skipFinalAwait = newLabel();
            emitJumpIfFalse(needsAwait.get(), skipFinalAwait.get());
            emitJumpIfTrue(hasAwaited.get(), skipFinalAwait.get());
            emitAwaitUndefined();
            emitLabel(skipFinalAwait.get());
        }

        // If any dispose threw, throw the pending error (which may be a SuppressedError chain).
        // This takes priority over break/continue/return completions.
        {
            Ref<Label> afterDisposeCheck = newLabel();
            emitJumpIfFalse(disposeThrew.get(), afterDisposeCheck.get());
            emitThrow(pendingError.get());
            emitLabel(afterDisposeCheck.get());
        }

        emitFinallyCompletion(finallyContext, done.get());
        emitLabel(done.get());
    }

    popFinallyControlFlowScope();
    m_usingScopeStack.removeLast();
}

void BytecodeGenerator::emitBodyWithUsingIfNeeded(unsigned usingCount, bool hasAwaitUsing, const ScopedLambda<void(BytecodeGenerator&)>& emitBody)
{
    if (usingCount)
        emitUsingBodyScope(usingCount, hasAwaitUsing, emitBody);
    else
        emitBody(*this);
}

void BytecodeGenerator::emitEnumeration(ThrowableExpressionData* node, ExpressionNode* subjectNode, const ScopedLambda<void(BytecodeGenerator&, RegisterID*)>& callBack, ForOfNode* forLoopNode, RegisterID* forLoopSymbolTable)
{
    if (forLoopNode && forLoopNode->isForAwait()) {
        ASSERT(isAsyncFunctionParseMode(parseMode()) || isModuleParseMode(parseMode()));

        RefPtr<RegisterID> subject = newTemporary();
        emitNode(subject.get(), subjectNode);

        RefPtr<RegisterID> iterator = newTemporary();
        RefPtr<RegisterID> nextMethod = newTemporary();

        emitGetGenericAsyncIterator(iterator.get(), nextMethod.get(), subject.get(), node);

        Ref<Label> loopDone = newLabel();

        Ref<Label> finallyLabel = newLabel();
        FinallyContext finallyContext(*this, finallyLabel.get());
        pushFinallyControlFlowScope(finallyContext);

        {
            Ref<LabelScope> scope = newLabelScope(LabelScope::Loop);
            RefPtr<RegisterID> value = newTemporary();
            emitLoad(value.get(), jsUndefined());

            emitJump(*scope->continueTarget());

            Ref<Label> loopStart = newLabel();
            emitLabel(loopStart.get());
            emitLoopHint();

            emitTryWithFinallyThatDoesNotShadowException(finallyContext, scopedLambda<void(BytecodeGenerator&)>([&](BytecodeGenerator& generator) {
                callBack(generator, value.get());
                generator.emitJump(*scope->continueTarget());
            }), scopedLambda<void(BytecodeGenerator&)>([&](BytecodeGenerator& generator) {
                generator.emitIteratorGenericClose(iterator.get(), node, EmitAwait::Yes);
            }));

            emitLabel(*scope->continueTarget());
            RELEASE_ASSERT(forLoopNode->isForOfNode());
            prepareLexicalScopeForNextForLoopIteration(forLoopNode, forLoopSymbolTable);
            emitDebugHook(forLoopNode->lexpr());

            {
                emitAsyncIteratorNext(value.get(), nextMethod.get(), iterator.get(), nullptr, node);
                emitAwait(value.get(), value.get(), node->divot());

                Ref<Label> typeIsObject = newLabel();
                emitJumpIfTrue(emitIsObject(newTemporary(), value.get()), typeIsObject.get());
                emitThrowTypeError("Iterator result interface is not an object."_s);
                emitLabel(typeIsObject.get());

                emitJumpIfTrue(emitGetById(newTemporary(), value.get(), propertyNames().done), loopDone.get());
                emitGetById(value.get(), value.get(), propertyNames().value);
                emitJump(loopStart.get());
            }

            bool breakLabelIsBound = scope->breakTargetMayBeBound();
            if (breakLabelIsBound)
                emitLabel(scope->breakTarget());
            popFinallyControlFlowScope();
            if (breakLabelIsBound) {
                // IteratorClose sequence for break-ed control flow.
                emitIteratorGenericClose(iterator.get(), node, EmitAwait::Yes);
            }
        }
        emitLabel(loopDone.get());
        return;
    }

    RefPtr<RegisterID> iterable = newTemporary();
    emitNode(iterable.get(), subjectNode);

    RefPtr<RegisterID> nextOrIndex = newTemporary();
    RefPtr<RegisterID> iterator = newTemporary();
    {
        emitExpressionInfo(node->divot(), node->divotStart(), node->divotEnd());
        RefPtr<RegisterID> iteratorSymbol = emitGetById(newTemporary(), iterable.get(), propertyNames().iteratorSymbol);
        CallArguments args(*this, nullptr, 0);
        move(args.thisRegister(), iterable.get());
        emitIteratorOpen(iterator.get(), nextOrIndex.get(), iteratorSymbol.get(), args, node);
    }

    Ref<Label> loopDone = newLabel();

    // RefPtr<RegisterID> iterator's lifetime must be longer than IteratorCloseContext.
    Ref<Label> finallyLabel = newLabel();
    FinallyContext finallyContext(*this, finallyLabel.get());
    pushFinallyControlFlowScope(finallyContext);

    {
        Ref<LabelScope> scope = newLabelScope(LabelScope::Loop);
        RefPtr<RegisterID> value = newTemporary();
        emitLoad(value.get(), jsUndefined());

        Ref<Label> loopStart = newLabel();
        emitLabel(loopStart.get());
        emitLabel(*scope->continueTarget());
        emitLoopHint();

        if (forLoopNode) {
            RELEASE_ASSERT(forLoopNode->isForOfNode());
            prepareLexicalScopeForNextForLoopIteration(forLoopNode, forLoopSymbolTable);
            emitDebugHook(forLoopNode->lexpr());
        }

        {
            RefPtr<RegisterID> done = newTemporary();
            CallArguments nextArgs(*this, nullptr, 0);
            move(nextArgs.thisRegister(), iterator.get());

            emitIteratorNext(done.get(), value.get(), iterable.get(), nextOrIndex.get(), nextArgs, node);
            emitJumpIfTrue(done.get(), loopDone.get());
        }

        emitTryWithFinallyThatDoesNotShadowException(finallyContext, scopedLambda<void(BytecodeGenerator&)>([&](BytecodeGenerator& generator) {
            callBack(generator, value.get());
            generator.emitJump(loopStart.get());
        }), scopedLambda<void(BytecodeGenerator&)>([&](BytecodeGenerator& generator) {
            generator.emitIteratorGenericClose(iterator.get(), node);
        }));

        bool breakLabelIsBound = scope->breakTargetMayBeBound();
        if (breakLabelIsBound)
            emitLabel(scope->breakTarget());
        popFinallyControlFlowScope();
        if (breakLabelIsBound) {
            // IteratorClose sequence for break-ed control flow.
            emitIteratorGenericClose(iterator.get(), node, EmitAwait::No);
        }
    }
    emitLabel(loopDone.get());
}

RegisterID* BytecodeGenerator::emitGetTemplateObject(RegisterID* dst, TaggedTemplateNode* taggedTemplate)
{
    TemplateObjectDescriptor::StringVector rawStrings;
    TemplateObjectDescriptor::OptionalStringVector cookedStrings;

    TemplateStringListNode* templateString = taggedTemplate->templateLiteral()->templateStrings();
    for (; templateString; templateString = templateString->next()) {
        auto* string = templateString->value();
        ASSERT(string->raw());
        rawStrings.append(string->raw()->impl());
        if (!string->cooked())
            cookedStrings.append(std::nullopt);
        else
            cookedStrings.append(string->cooked()->impl());
    }
    RefPtr<RegisterID> constant = addTemplateObjectConstant(TemplateObjectDescriptor::create(WTF::move(rawStrings), WTF::move(cookedStrings)), taggedTemplate->endOffset());
    if (!dst)
        return constant.unsafeGet();
    return move(dst, constant.get());
}

RegisterID* BytecodeGenerator::emitGetGlobalPrivate(RegisterID* dst, const Identifier& property)
{
    dst = tempDestination(dst);
    Variable var = variable(property);
    if (RegisterID* local = var.local())
        return move(dst, local);

    RefPtr<RegisterID> scope = newTemporary();
    move(scope.get(), emitResolveScope(scope.get(), var));
    return emitGetFromScope(dst, scope.get(), var, ThrowIfNotFound);
}

void BytecodeGenerator::emitEnumeratorNext(RegisterID* propertyName, RegisterID* mode, RegisterID* index, RegisterID* base, RegisterID* enumerator)
{
    OpEnumeratorNext::emit(this, propertyName, mode, index, base, enumerator);
}

RegisterID* BytecodeGenerator::emitEnumeratorHasOwnProperty(RegisterID* dst, RegisterID* base, RegisterID* mode, RegisterID* propertyName, RegisterID* index, RegisterID* enumerator)
{
    OpEnumeratorHasOwnProperty::emit(this, dst, base, mode, propertyName, index, enumerator);
    return dst;
}

RegisterID* BytecodeGenerator::emitGetPropertyEnumerator(RegisterID* dst, RegisterID* base)
{
    OpGetPropertyEnumerator::emit(this, dst, base);
    return dst;
}

RegisterID* BytecodeGenerator::emitIsCellWithType(RegisterID* dst, RegisterID* src, JSType type)
{
    OpIsCellWithType::emit(this, dst, src, type);
    return dst;
}

RegisterID* BytecodeGenerator::emitIsObject(RegisterID* dst, RegisterID* src)
{
    OpIsObject::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitIsCallable(RegisterID* dst, RegisterID* src)
{
    OpIsCallable::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitIsConstructor(RegisterID* dst, RegisterID* src)
{
    OpIsConstructor::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitIsNumber(RegisterID* dst, RegisterID* src)
{
    OpIsNumber::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitIsUndefinedOrNull(RegisterID* dst, RegisterID* src)
{
    OpIsUndefinedOrNull::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitIsEmpty(RegisterID* dst, RegisterID* src)
{
    OpIsEmpty::emit(this, dst, src);
    return dst;
}

RegisterID* BytecodeGenerator::emitLoadArrowFunctionLexicalEnvironment(const Identifier& identifier)
{
    ASSERT(m_codeBlock->isArrowFunction() || m_codeBlock->isArrowFunctionContext() || constructorKind() == ConstructorKind::Extends || m_codeType == EvalCode || m_codeBlock->parseMode() == SourceParseMode::ClassFieldInitializerMode);

    return emitResolveScope(nullptr, variable(identifier, ThisResolutionType::Scoped));
}

void BytecodeGenerator::emitLoadThisFromArrowFunctionLexicalEnvironment()
{
    emitGetFromScope(thisRegister(), emitLoadArrowFunctionLexicalEnvironment(propertyNames().builtinNames().thisPrivateName()), variable(propertyNames().builtinNames().thisPrivateName(), ThisResolutionType::Scoped), DoNotThrowIfNotFound);
}
    
RegisterID* BytecodeGenerator::emitLoadNewTargetFromArrowFunctionLexicalEnvironment()
{
    Variable newTargetVar = variable(propertyNames().builtinNames().newTargetLocalPrivateName());

    return emitGetFromScope(m_newTargetRegister, emitLoadArrowFunctionLexicalEnvironment(propertyNames().builtinNames().newTargetLocalPrivateName()), newTargetVar, ThrowIfNotFound);
    
}

RegisterID* BytecodeGenerator::emitLoadDerivedConstructorFromArrowFunctionLexicalEnvironment()
{
    Variable protoScopeVar = variable(propertyNames().builtinNames().derivedConstructorPrivateName());
    return emitGetFromScope(newTemporary(), emitLoadArrowFunctionLexicalEnvironment(propertyNames().builtinNames().derivedConstructorPrivateName()), protoScopeVar, ThrowIfNotFound);
}

RegisterID* BytecodeGenerator::emitLoadDerivedConstructor()
{
    ASSERT(constructorKind() == ConstructorKind::Extends || isDerivedConstructorContext());
    if (constructorKind() == ConstructorKind::Extends)
        return &m_calleeRegister;
    return emitLoadDerivedConstructorFromArrowFunctionLexicalEnvironment();
}

RegisterID* BytecodeGenerator::ensureThis()
{
    if (constructorKind() == ConstructorKind::Extends || isDerivedConstructorContext()) {
        if ((needsToUpdateArrowFunctionContext() && isSuperCallUsedInInnerArrowFunction()) || m_codeBlock->parseMode() == SourceParseMode::AsyncArrowFunctionBodyMode)
            emitLoadThisFromArrowFunctionLexicalEnvironment();

        emitTDZCheck(thisRegister());
    }

    return thisRegister();
}
    
bool BytecodeGenerator::isThisUsedInInnerArrowFunction()
{
    return m_scopeNode->doAnyInnerArrowFunctionsUseThis() || m_scopeNode->doAnyInnerArrowFunctionsUseSuperProperty() || m_scopeNode->doAnyInnerArrowFunctionsUseSuperCall() || m_scopeNode->doAnyInnerArrowFunctionsUseEval() || usesEval();
}
    
bool BytecodeGenerator::isArgumentsUsedInInnerArrowFunction()
{
    return m_scopeNode->doAnyInnerArrowFunctionsUseArguments() || m_scopeNode->doAnyInnerArrowFunctionsUseEval();
}

bool BytecodeGenerator::isNewTargetUsedInInnerArrowFunction()
{
    return m_scopeNode->doAnyInnerArrowFunctionsUseNewTarget() || m_scopeNode->doAnyInnerArrowFunctionsUseSuperCall() || m_scopeNode->doAnyInnerArrowFunctionsUseEval() || usesEval();
}

bool BytecodeGenerator::isSuperUsedInInnerArrowFunction()
{
    return m_scopeNode->doAnyInnerArrowFunctionsUseSuperCall() || m_scopeNode->doAnyInnerArrowFunctionsUseSuperProperty() || m_scopeNode->doAnyInnerArrowFunctionsUseEval() || usesEval();
}

bool BytecodeGenerator::isSuperCallUsedInInnerArrowFunction()
{
    return m_scopeNode->doAnyInnerArrowFunctionsUseSuperCall() || m_scopeNode->doAnyInnerArrowFunctionsUseEval() || usesEval();
}
    
void BytecodeGenerator::emitPutNewTargetToArrowFunctionContextScope()
{
    if (isNewTargetUsedInInnerArrowFunction()) {
        ASSERT(m_arrowFunctionContextLexicalEnvironmentRegister);
        
        Variable newTargetVar = variable(propertyNames().builtinNames().newTargetLocalPrivateName());
        emitPutToScope(m_arrowFunctionContextLexicalEnvironmentRegister, newTargetVar, newTarget(), DoNotThrowIfNotFound, InitializationMode::Initialization);
    }
}
    
void BytecodeGenerator::emitPutDerivedConstructorToArrowFunctionContextScope()
{
    if (needsDerivedConstructorInArrowFunctionLexicalEnvironment()) {
        ASSERT(m_arrowFunctionContextLexicalEnvironmentRegister);

        Variable protoScope = variable(propertyNames().builtinNames().derivedConstructorPrivateName());
        emitPutToScope(m_arrowFunctionContextLexicalEnvironmentRegister, protoScope, &m_calleeRegister, DoNotThrowIfNotFound, InitializationMode::Initialization);
    }
}

void BytecodeGenerator::emitPutThisToArrowFunctionContextScope()
{
    if (isThisUsedInInnerArrowFunction() || (m_scopeNode->usesSuperCall() && m_codeType == EvalCode)) {
        ASSERT(isDerivedConstructorContext() || m_arrowFunctionContextLexicalEnvironmentRegister != nullptr);

        Variable thisVar = variable(propertyNames().builtinNames().thisPrivateName(), ThisResolutionType::Scoped);
        RegisterID* scope = isDerivedConstructorContext() ? emitLoadArrowFunctionLexicalEnvironment(propertyNames().builtinNames().thisPrivateName()) : m_arrowFunctionContextLexicalEnvironmentRegister;
    
        emitPutToScope(scope, thisVar, thisRegister(), ThrowIfNotFound, InitializationMode::NotInitialization);
    }
}

void BytecodeGenerator::pushForInScope(RegisterID* localRegister, RegisterID* propertyNameRegister, RegisterID* propertyOffsetRegister, RegisterID* enumeratorRegister, RegisterID* modeRegister, std::optional<Variable> baseVariable)
{
    if (!localRegister)
        return;
    unsigned bodyBytecodeStartOffset = instructions().size();
    m_forInContextStack.append(adoptRef(*new ForInContext(localRegister, propertyNameRegister, propertyOffsetRegister, enumeratorRegister, modeRegister, baseVariable, bodyBytecodeStartOffset)));
    disablePeepholeOptimization();
}

void BytecodeGenerator::popForInScope(RegisterID* localRegister)
{
    if (!localRegister)
        return;
    unsigned bodyBytecodeEndOffset = instructions().size();
    m_forInContextStack.last()->finalize(*this, m_codeBlock.get(), bodyBytecodeEndOffset);
    m_forInContextStack.removeLast();
}

RegisterID* BytecodeGenerator::emitRestParameter(RegisterID* result, unsigned numParametersToSkip)
{
    OpCreateRest::emit(this, result, numParametersToSkip);

    return result;
}

void BytecodeGenerator::emitRequireObjectCoercible(RegisterID* value, ASCIILiteral error)
{
    Ref<Label> target = newLabel();
    OpJnundefinedOrNull::emit(this, value, target->bind(this));
    emitThrowTypeError(error);
    emitLabel(target.get());
}

void BytecodeGenerator::emitRequireObjectCoercibleForDestructuring(RegisterID* value, const Identifier* propertyName)
{
    Ref<Label> target = newLabel();
    OpJnundefinedOrNull::emit(this, value, target->bind(this));

    if (propertyName && !propertyName->isNull()) {
        auto errorMessageStr = tryMakeString("Cannot destructure property '"_s, propertyName->string(), "' from null or undefined value"_s);
        if (!errorMessageStr) [[unlikely]]
            emitThrowTypeError("Cannot destructure null or undefined value"_s);
        else
            emitThrowTypeError(Identifier::fromString(m_vm, errorMessageStr));
    } else
        emitThrowTypeError("Cannot destructure null or undefined value"_s);

    emitLabel(target.get());
}

void BytecodeGenerator::emitYieldPoint(RegisterID* argument, JSAsyncGenerator::AsyncGeneratorSuspendReason result)
{
    Ref<Label> mergePoint = newLabel();
    unsigned yieldPointIndex = m_yieldPoints++;
    auto state = Checked<int32_t>(yieldPointIndex) + 1;
    if (parseMode() == SourceParseMode::AsyncGeneratorBodyMode)
        state = (state << JSAsyncGenerator::reasonShift) | static_cast<unsigned>(result);

    emitGeneratorStateChange(state.value());

    // Split the try range here.
    Ref<Label> savePoint = newEmittedLabel();
    for (unsigned i = m_tryContextStack.size(); i--;) {
        TryContext& context = m_tryContextStack[i];
        m_tryRanges.append(TryRange {
            context.start.copyRef(),
            savePoint.copyRef(),
            context.tryData
        });
        // Try range will be restared at the merge point.
        context.start = mergePoint.get();
    }
    Vector<TryContext> savedTryContextStack;
    m_tryContextStack.swap(savedTryContextStack);


    OpYield::emit(this, yieldPointIndex, argument);

    // Restore the try contexts, which start offset is updated to the merge point.
    m_tryContextStack.swap(savedTryContextStack);
    emitLabel(mergePoint.get());
}

RegisterID* BytecodeGenerator::emitYield(RegisterID* argument)
{
    // For async generators the operand is Awaited by the driver (reason Yield), not here, so there is no
    // extra yield point. `yield*` instead suspends with YieldNoAwait (see emitDelegateYield) so the driver
    // skips that await.
    emitYieldPoint(argument, JSAsyncGenerator::AsyncGeneratorSuspendReason::Yield);

    Ref<Label> normalLabel = newLabel();
    emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), generatorResumeModeRegister(), emitLoad(nullptr, JSGenerator::ResumeMode::NormalMode)), normalLabel.get());

    Ref<Label> throwLabel = newLabel();
    emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), generatorResumeModeRegister(), emitLoad(nullptr, JSGenerator::ResumeMode::ThrowMode)), throwLabel.get());
    // Return.
    {
        RefPtr<RegisterID> returnRegister = generatorValueRegister();
        bool hasFinally = emitReturnViaFinallyIfNeeded(returnRegister.get());
        if (!hasFinally)
            emitReturn(returnRegister.get());
    }

    // Throw.
    emitLabel(throwLabel.get());
    emitThrow(generatorValueRegister());

    // Normal.
    emitLabel(normalLabel.get());
    return generatorValueRegister();
}

RegisterID* BytecodeGenerator::emitAwait(RegisterID* dst, RegisterID* src, const JSTextPosition& position)
{
    emitDebugHook(WillAwait, position, generatorRegister());

    emitYieldPoint(src, JSAsyncGenerator::AsyncGeneratorSuspendReason::Await);

    Ref<Label> normalLabel = newLabel();
    emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), generatorResumeModeRegister(), emitLoad(nullptr, JSGenerator::ResumeMode::NormalMode)), normalLabel.get());

    emitThrow(generatorValueRegister());

    emitLabel(normalLabel.get());
    auto result = move(dst, generatorValueRegister());

    emitDebugHook(DidAwait, position, generatorRegister());

    return result;
}

RegisterID* BytecodeGenerator::emitCallIterator(RegisterID* iterator, RegisterID* argument, ThrowableExpressionData* node)
{
    CallArguments args(*this, nullptr);
    move(args.thisRegister(), argument);
    emitCall(iterator, iterator, NoExpectedFunction, args, node->divot(), node->divotStart(), node->divotEnd(), DebuggableCall::No);

    return iterator;
}

void BytecodeGenerator::emitIteratorOpen(RegisterID* iterator, RegisterID* nextOrIndex, RegisterID* symbolIterator, CallArguments& iterable, const ThrowableExpressionData* node)
{
    // Reserve space for call frame.
    Vector<RefPtr<RegisterID>, CallFrame::headerSizeInRegisters, UnsafeVectorOverflow> callFrame;
    for (int i = 0; i < CallFrame::headerSizeInRegisters; ++i)
        callFrame.append(newTemporary());

    if (shouldEmitDebugHooks())
        emitDebugHook(WillExecuteExpression, node->divotStart());

    emitExpressionInfo(node->divot(), node->divotStart(), node->divotEnd());
    OpIteratorOpen::emit(this, iterator, nextOrIndex, symbolIterator, iterable.thisRegister(), iterable.stackOffset(), nextValueProfileIndex(), nextValueProfileIndex(), nextValueProfileIndex());
}

void BytecodeGenerator::emitIteratorNext(RegisterID* done, RegisterID* value, RegisterID* iterable, RegisterID* nextOrIndex, CallArguments& iterator, const ThrowableExpressionData* node)
{
    // Reserve space for call frame.
    Vector<RefPtr<RegisterID>, CallFrame::headerSizeInRegisters, UnsafeVectorOverflow> callFrame;
    for (int i = 0; i < CallFrame::headerSizeInRegisters; ++i)
        callFrame.append(newTemporary());

    if (shouldEmitDebugHooks())
        emitDebugHook(WillExecuteExpression, node->divotStart());

    emitExpressionInfo(node->divot(), node->divotStart(), node->divotEnd());
    OpIteratorNext::emit(this, done, value, iterable, nextOrIndex, iterator.thisRegister(), iterator.stackOffset(), nextValueProfileIndex(), nextValueProfileIndex(), nextValueProfileIndex());
}

RegisterID* BytecodeGenerator::emitGetGenericIterator(RegisterID* argument, ThrowableExpressionData* node)
{
    emitExpressionInfo(node->divot(), node->divotStart(), node->divotEnd());
    RefPtr<RegisterID> iterator = emitGetById(newTemporary(), argument, propertyNames().iteratorSymbol);
    emitCallIterator(iterator.get(), argument, node);

    return iterator.unsafeGet();
}

RegisterID* BytecodeGenerator::emitIteratorGenericNext(RegisterID* dst, RegisterID* nextMethod, RegisterID* iterator, const ThrowableExpressionData* node, EmitAwait doEmitAwait)
{
    {
        CallArguments nextArguments(*this, nullptr);
        move(nextArguments.thisRegister(), iterator);
        emitCall(dst, nextMethod, NoExpectedFunction, nextArguments, node->divot(), node->divotStart(), node->divotEnd(), DebuggableCall::No);

        if (doEmitAwait == EmitAwait::Yes)
            emitAwait(dst, dst, node->divot());
    }
    {
        Ref<Label> typeIsObject = newLabel();
        emitJumpIfTrue(emitIsObject(newTemporary(), dst), typeIsObject.get());
        emitThrowTypeError("Iterator result interface is not an object."_s);
        emitLabel(typeIsObject.get());
    }
    return dst;
}

RegisterID* BytecodeGenerator::emitIteratorGenericNextWithValue(RegisterID* dst, RegisterID* nextMethod, RegisterID* iterator, RegisterID* value, const ThrowableExpressionData* node)
{
    {
        CallArguments nextArguments(*this, nullptr, 1);
        move(nextArguments.thisRegister(), iterator);
        move(nextArguments.argumentRegister(0), value);
        emitCall(dst, nextMethod, NoExpectedFunction, nextArguments, node->divot(), node->divotStart(), node->divotEnd(), DebuggableCall::No);
    }

    return dst;
}

void BytecodeGenerator::emitIteratorGenericClose(RegisterID* iterator, const ThrowableExpressionData* node, EmitAwait doEmitAwait)
{
    Ref<Label> done = newLabel();
    RefPtr<RegisterID> returnMethod = emitGetById(newTemporary(), iterator, propertyNames().returnKeyword);
    emitJumpIfTrue(emitIsUndefinedOrNull(newTemporary(), returnMethod.get()), done.get());

    RefPtr<RegisterID> value = newTemporary();
    CallArguments returnArguments(*this, nullptr);
    move(returnArguments.thisRegister(), iterator);
    emitCall(value.get(), returnMethod.get(), NoExpectedFunction, returnArguments, node->divot(), node->divotStart(), node->divotEnd(), DebuggableCall::No);

    if (doEmitAwait == EmitAwait::Yes)
        emitAwait(value.get(), value.get(), node->divot());

    emitJumpIfTrue(emitIsObject(newTemporary(), value.get()), done.get());
    emitThrowTypeError("Iterator result interface is not an object."_s);
    emitLabel(done.get());
}


RegisterID* BytecodeGenerator::emitDelegateYield(RegisterID* argument, ThrowableExpressionData* node)
{
    bool isAsync = parseMode() == SourceParseMode::AsyncGeneratorBodyMode;
    EmitAwait emitAwaitInClose = isAsync ? EmitAwait::Yes : EmitAwait::No;

    RefPtr<RegisterID> value = newTemporary();
    {
        RefPtr<RegisterID> iterator;
        RefPtr<RegisterID> nextMethod;
        if (isAsync) {
            iterator = newTemporary();
            nextMethod = newTemporary();
            emitGetGenericAsyncIterator(iterator.get(), nextMethod.get(), argument, node);
        } else {
            iterator = emitGetGenericIterator(argument, node);
            nextMethod = emitGetById(newTemporary(), iterator.get(), propertyNames().next);
        }

        Ref<Label> loopDone = newLabel();
        {
            Ref<Label> nextElement = newLabel();
            emitLoad(value.get(), jsUndefined());

            emitJump(nextElement.get());

            Ref<Label> loopStart = newLabel();
            emitLabel(loopStart.get());
            emitLoopHint();

            Ref<Label> branchOnResult = newLabel();
            {
                // `yield*` delegates the inner iterator's value without an enclosing Await (for the async
                // case, the iterator result is already Awaited below). YieldNoAwait tells the async driver
                // not to await it again.
                emitYieldPoint(value.get(), JSAsyncGenerator::AsyncGeneratorSuspendReason::YieldNoAwait);
                move(value.get(), generatorValueRegister());

                Ref<Label> normalLabel = newLabel();
                emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), generatorResumeModeRegister(), emitLoad(nullptr, JSGenerator::ResumeMode::NormalMode)), normalLabel.get());

                Ref<Label> returnLabel = newLabel();
                emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), generatorResumeModeRegister(), emitLoad(nullptr, JSGenerator::ResumeMode::ReturnMode)), returnLabel.get());

                // Throw. throw()/return() have no dedicated opcode, so call them generically (the fast
                // async driver path only applies to the normal-mode next() below).
                {
                    Ref<Label> throwMethodFound = newLabel();
                    RefPtr<RegisterID> throwMethod = emitGetById(newTemporary(), iterator.get(), propertyNames().throwKeyword);
                    emitJumpIfFalse(emitIsUndefinedOrNull(newTemporary(), throwMethod.get()), throwMethodFound.get());

                    emitIteratorGenericClose(iterator.get(), node, emitAwaitInClose);

                    emitThrowTypeError("The iterator, to which yield* delegated iteration, does not have a 'throw' method."_s);

                    emitLabel(throwMethodFound.get());
                    CallArguments throwArguments(*this, nullptr, 1);
                    move(throwArguments.thisRegister(), iterator.get());
                    move(throwArguments.argumentRegister(0), value.get());
                    emitCall(value.get(), throwMethod.get(), NoExpectedFunction, throwArguments, node->divot(), node->divotStart(), node->divotEnd(), DebuggableCall::No);

                    emitJump(branchOnResult.get());
                }

                // Return.
                emitLabel(returnLabel.get());
                {
                    Ref<Label> returnMethodFound = newLabel();
                    RefPtr<RegisterID> returnMethod = emitGetById(newTemporary(), iterator.get(), propertyNames().returnKeyword);
                    emitJumpIfFalse(emitIsUndefinedOrNull(newTemporary(), returnMethod.get()), returnMethodFound.get());

                    if (isAsync)
                        emitAwait(value.get(), value.get(), node->divot());

                    Ref<Label> returnSequence = newLabel();
                    emitJump(returnSequence.get());

                    emitLabel(returnMethodFound.get());
                    CallArguments returnArguments(*this, nullptr, 1);
                    move(returnArguments.thisRegister(), iterator.get());
                    move(returnArguments.argumentRegister(0), value.get());
                    emitCall(value.get(), returnMethod.get(), NoExpectedFunction, returnArguments, node->divot(), node->divotStart(), node->divotEnd(), DebuggableCall::No);

                    if (isAsync)
                        emitAwait(value.get(), value.get(), node->divot());

                    Ref<Label> returnIteratorResultIsObject = newLabel();
                    emitJumpIfTrue(emitIsObject(newTemporary(), value.get()), returnIteratorResultIsObject.get());
                    emitThrowTypeError("Iterator result interface is not an object."_s);

                    emitLabel(returnIteratorResultIsObject.get());

                    Ref<Label> returnFromGenerator = newLabel();
                    emitJumpIfTrue(emitGetById(newTemporary(), value.get(), propertyNames().done), returnFromGenerator.get());

                    emitGetById(value.get(), value.get(), propertyNames().value);
                    emitJump(loopStart.get());

                    emitLabel(returnFromGenerator.get());
                    emitGetById(value.get(), value.get(), propertyNames().value);

                    emitLabel(returnSequence.get());
                    bool hasFinally = emitReturnViaFinallyIfNeeded(value.get());
                    if (!hasFinally)
                        emitReturn(value.get());
                }

                // Normal.
                emitLabel(normalLabel.get());
            }

            emitLabel(nextElement.get());
            if (isAsync)
                emitAsyncIteratorNext(value.get(), nextMethod.get(), iterator.get(), value.get(), node);
            else
                emitIteratorGenericNextWithValue(value.get(), nextMethod.get(), iterator.get(), value.get(), node);

            emitLabel(branchOnResult.get());

            if (isAsync)
                emitAwait(value.get(), value.get(), node->divot());

            Ref<Label> iteratorValueIsObject = newLabel();
            emitJumpIfTrue(emitIsObject(newTemporary(), value.get()), iteratorValueIsObject.get());
            emitThrowTypeError("Iterator result interface is not an object."_s);
            emitLabel(iteratorValueIsObject.get());

            emitJumpIfTrue(emitGetById(newTemporary(), value.get(), propertyNames().done), loopDone.get());
            emitGetById(value.get(), value.get(), propertyNames().value);

            emitJump(loopStart.get());
        }
        emitLabel(loopDone.get());
    }

    emitGetById(value.get(), value.get(), propertyNames().value);
    return value.unsafeGet();
}

void BytecodeGenerator::emitGeneratorStateChange(int32_t state)
{
    // FIXME: It seems like this will create a lot of constants if there are many yield points. Maybe we should op_inc the old state. https://bugs.webkit.org/show_bug.cgi?id=222254
    RegisterID* completedState = emitLoad(nullptr, jsNumber(state));
    static_assert(static_cast<unsigned>(JSGenerator::Field::State) == static_cast<unsigned>(JSAsyncGenerator::Field::State));
    emitPutInternalField(generatorRegister(), isModuleParseMode(parseMode()) ? static_cast<unsigned>(AbstractModuleRecord::Field::State) : static_cast<unsigned>(JSGenerator::Field::State), completedState);
}

bool BytecodeGenerator::emitJumpViaFinallyIfNeeded(int targetLabelScopeDepth, Label& jumpTarget)
{
    ASSERT(labelScopeDepth() - targetLabelScopeDepth >= 0);
    size_t numberOfScopesToCheckForFinally = labelScopeDepth() - targetLabelScopeDepth;
    ASSERT(numberOfScopesToCheckForFinally <= m_controlFlowScopeStack.size());
    if (!numberOfScopesToCheckForFinally)
        return false;

    FinallyContext* innermostFinallyContext = nullptr;
    FinallyContext* outermostFinallyContext = nullptr;
    size_t scopeIndex = m_controlFlowScopeStack.size() - 1;
    while (numberOfScopesToCheckForFinally--) {
        ControlFlowScope* scope = &m_controlFlowScopeStack[scopeIndex--];
        if (scope->isFinallyScope()) {
            FinallyContext* finallyContext = scope->finallyContext;
            if (!innermostFinallyContext)
                innermostFinallyContext = finallyContext;
            outermostFinallyContext = finallyContext;
            finallyContext->incNumberOfBreaksOrContinues();
        }
    }
    if (!outermostFinallyContext)
        return false; // No finallys to thread through.

    auto jumpID = bytecodeOffsetToJumpID(instructions().size());
    int lexicalScopeIndex = labelScopeDepthToLexicalScopeIndex(targetLabelScopeDepth);
    outermostFinallyContext->registerJump(jumpID, lexicalScopeIndex, jumpTarget);

    emitLoad(innermostFinallyContext->completionTypeRegister(), jumpID);
    emitJump(*innermostFinallyContext->finallyLabel());
    return true; // We'll be jumping to a finally block.
}

bool BytecodeGenerator::emitReturnViaFinallyIfNeeded(RegisterID* returnRegister)
{
    size_t numberOfScopesToCheckForFinally = m_controlFlowScopeStack.size();
    if (!numberOfScopesToCheckForFinally)
        return false;

    FinallyContext* innermostFinallyContext = nullptr;
    while (numberOfScopesToCheckForFinally) {
        size_t scopeIndex = --numberOfScopesToCheckForFinally;
        ControlFlowScope* scope = &m_controlFlowScopeStack[scopeIndex];
        if (scope->isFinallyScope()) {
            FinallyContext* finallyContext = scope->finallyContext;
            if (!innermostFinallyContext)
                innermostFinallyContext = finallyContext;
            finallyContext->setHandlesReturns();
        }
    }
    if (!innermostFinallyContext)
        return false; // No finallys to thread through.

    emitLoad(innermostFinallyContext->completionTypeRegister(), CompletionType::Return);
    move(innermostFinallyContext->completionValueRegister(), returnRegister);
    emitJump(*innermostFinallyContext->finallyLabel());
    return true; // We'll be jumping to a finally block.
}

void BytecodeGenerator::emitFinallyCompletion(FinallyContext& context, Label& normalCompletionLabel)
{
    if (context.numberOfBreaksOrContinues() || context.handlesReturns()) {
        emitJumpIfTrue(emitEqualityOp<OpStricteq>(newTemporary(), context.completionTypeRegister(), emitLoad(nullptr, CompletionType::Normal)), normalCompletionLabel);

        FinallyContext* outerContext = context.outerContext();

        size_t numberOfJumps = context.numberOfJumps();
        ASSERT(outerContext || numberOfJumps == context.numberOfBreaksOrContinues());

        // Handle Break or Continue completions that jumps into this FinallyContext.
        for (size_t i = 0; i < numberOfJumps; i++) {
            Ref<Label> nextLabel = newLabel();
            auto& jump = context.jumps(i);
            emitJumpIfFalse(emitEqualityOp<OpStricteq>(newTemporary(), context.completionTypeRegister(), emitLoad(nullptr, jump.jumpID)), nextLabel.get());

            // This case is for Break / Continue completions from an inner finally context
            // with a jump target that is not beyond the next outer finally context:
            //
            //     try {
            //         for (... stuff ...) {
            //             try {
            //                 continue; // Sets completionType to jumpID of top of the for loop.
            //             } finally {
            //             } // Jump to top of the for loop on completion.
            //         }
            //     } finally {
            //     }
            //
            // Since the jumpID is targetting a label that is inside the outer finally context,
            // we can jump to it directly on completion of this finally context: there is no intermediate
            // finally blocks to run. After the Break / Continue, we will contnue execution as normal.
            // So, we'll set the completionType to Normal (on behalf of the target) before we jump.
            // We can also set the completion value to undefined, but it will never be used for normal
            // completion anyway. So, we'll skip setting it.

            restoreScopeRegister(jump.targetLexicalScopeIndex);
            emitLoad(context.completionTypeRegister(), CompletionType::Normal);
            emitJump(jump.targetLabel.get());

            emitLabel(nextLabel.get());
        }

        // Handle completions that take us out of this FinallyContext.
        if (outerContext) {
            if (context.handlesReturns()) {
                Ref<Label> isNotReturnLabel = newLabel();
                emitJumpIfFalse(emitEqualityOp<OpStricteq>(newTemporary(), context.completionTypeRegister(), emitLoad(nullptr, CompletionType::Return)), isNotReturnLabel.get());

                // This case is for Return completion from an inner finally context:
                //
                //     try {
                //         try {
                //             return result; // Sets completionType to Return, and completionValue to result.
                //         } finally {
                //         } // Jump to outer finally on completion.
                //     } finally {
                //     }
                //
                // Since we know there's at least one outer finally context (beyond the current context),
                // we cannot actually return from here. Instead, we pass the completionType and completionValue
                // on to the next outer finally, and let it decide what to do next on its completion. The
                // outer finally may or may not actual return depending on whether it encounters an abrupt
                // completion in its body that overrrides this Return completion.

                move(outerContext->completionTypeRegister(), context.completionTypeRegister());
                move(outerContext->completionValueRegister(), context.completionValueRegister());
                emitJump(*outerContext->finallyLabel());

                emitLabel(isNotReturnLabel.get());
            }

            bool hasBreaksOrContinuesThatEscapeCurrentFinally = context.numberOfBreaksOrContinues() > numberOfJumps;
            if (hasBreaksOrContinuesThatEscapeCurrentFinally) {
                Ref<Label> isThrowOrNormalLabel = newLabel();
                emitJumpIfTrue(emitBinaryOp<OpBeloweq>(newTemporary(), context.completionTypeRegister(), emitLoad(nullptr, CompletionType::Throw)), isThrowOrNormalLabel.get());

                // A completionType above Throw means we have a Break or Continue encoded as a jumpID.
                // We already ruled out Return above.
                static_assert(CompletionType::Throw < CompletionType::Return && CompletionType::Throw < CompletionType::Return, "jumpIDs are above CompletionType::Return");

                // This case is for Break / Continue completions in an inner finally context:
                //
                // 10: label:
                // 11: try {
                // 12:     try {
                // 13:         for (... stuff ...)
                // 14:             break label; // Sets completionType to jumpID of label.
                // 15:     } finally {
                // 16:     } // Jumps to outer finally on completion.
                // 17:  } finally {
                // 18:  }
                //
                // The break (line 14) says to continue execution at the label at line 10. Before we can
                // goto line 10, the inner context's finally (line 15) needs to be run, followed by the
                // outer context's finally (line 17). 'outerContext' being non-null above tells us that
                // there is at least one outer finally context that we need to run after we complete the
                // current finally. Note that unless the body of the outer finally abruptly completes in a
                // different way, that outer finally also needs to complete with a Break / Continue to
                // the same target label. Hence, we need to pass the jumpID in this finally's completionTypeRegister
                // to the outer finally. The completion value for Break and Continue according to the spec
                // is undefined, but it won't ever be used. So, we'll skip setting it.
                //
                // Note that all we're doing here is passing the Break / Continue completion to the next
                // outer finally context. We don't worry about finally contexts beyond that. It is the
                // responsibility of the next outer finally to determine what to do next at its completion,
                // and pass on to the next outer context if present and needed.

                move(outerContext->completionTypeRegister(), context.completionTypeRegister());
                emitJump(*outerContext->finallyLabel());

                emitLabel(isThrowOrNormalLabel.get());
            }

        } else {
            // We are the outermost finally.
            if (context.handlesReturns()) {
                Ref<Label> notReturnLabel = newLabel();
                emitJumpIfFalse(emitEqualityOp<OpStricteq>(newTemporary(), context.completionTypeRegister(), emitLoad(nullptr, CompletionType::Return)), notReturnLabel.get());

                // This case is for Return completion from the outermost finally context:
                //
                //     try {
                //         return result; // Sets completionType to Return, and completionValue to result.
                //     } finally {
                //     } // Executes the return of the completionValue.
                //
                // Since we know there's no outer finally context (beyond the current context) to run,
                // we can actually execute a return for this Return completion. The value to return
                // is whatever is in the completionValueRegister.

                emitWillLeaveCallFrameDebugHook();
                emitReturn(context.completionValueRegister());

                emitLabel(notReturnLabel.get());
            }
        }
    }

    // By now, we've rule out all Break / Continue / Return completions above. The only remaining
    // possibilities are Normal or Throw.

    emitJumpIfFalse(emitEqualityOp<OpStricteq>(newTemporary(), context.completionTypeRegister(), emitLoad(nullptr, CompletionType::Throw)), normalCompletionLabel);

    // We get here because we entered this finally context with Throw completionType (i.e. we have
    // an exception that we need to rethrow), and we didn't encounter a different abrupt completion
    // that overrides that incoming completionType. All we have to do here is re-throw the exception
    // captured in the completionValue.
    //
    // Note that unlike for Break / Continue / Return, we don't need to worry about outer finally
    // contexts. This is because any outer finally context (if present) will have its own exception
    // handler, which will take care of receiving the Throw completion, and re-capturing the exception
    // in its completionValue.

    emitThrow(context.completionValueRegister());
}

void BytecodeGenerator::pushOptionalChainTarget()
{
    m_optionalChainTargetStack.append(newLabel());
}

void BytecodeGenerator::pushOptionalChainTarget(Label& existingTarget)
{
    m_optionalChainTargetStack.append(existingTarget);
}

void BytecodeGenerator::popOptionalChainTarget()
{
    ASSERT(m_optionalChainTargetStack.size());
    emitLabel(m_optionalChainTargetStack.takeLast().get());
}

void BytecodeGenerator::popOptionalChainTarget(RegisterID* dst, bool isDelete)
{
    Ref<Label> endLabel = newLabel();
    emitJump(endLabel.get());

    popOptionalChainTarget();
    emitLoad(dst, isDelete ? jsBoolean(true) : jsUndefined());

    emitLabel(endLabel.get());
}

void BytecodeGenerator::discardOptionalChainTarget()
{
    ASSERT(m_optionalChainTargetStack.size());
    m_optionalChainTargetStack.removeLast();
}

void BytecodeGenerator::emitOptionalCheck(RegisterID* src)
{
    ASSERT(m_optionalChainTargetStack.size());
    emitJumpIfTrue(emitIsUndefinedOrNull(newTemporary(), src), m_optionalChainTargetStack.last().get());
}

template <typename OldOpType, typename NewOpType, typename TupleType>
ALWAYS_INLINE void rewriteOp(BytecodeGenerator& generator, TupleType& instTuple)
{
    unsigned instIndex = std::get<0>(instTuple);
    int propertyRegIndex = std::get<1>(instTuple);
    auto instruction = generator.m_writer.ref(instIndex);
    auto end = instIndex + instruction->size();
    ASSERT(instruction->isWide32());

    generator.m_writer.seek(instIndex);

    auto bytecode = instruction->as<OldOpType>();

    generator.disablePeepholeOptimization();

    // Change the opcode to get_by_val.
    // 1. dst stays the same.
    // 2. base stays the same.
    // 3. property gets switched to the original property.

    static_assert(sizeof(NewOpType) <= sizeof(OldOpType));
    if constexpr (NewOpType::opcodeID == op_in_by_val)
        NewOpType::emit(&generator, bytecode.m_dst, bytecode.m_base, VirtualRegister(propertyRegIndex));
    else
        NewOpType::emit(&generator, bytecode.m_dst, bytecode.m_base, VirtualRegister(propertyRegIndex), generator.nextValueProfileIndex());

    // 4. nop out the remaining bytes
    while (generator.m_writer.position() < end)
        OpNop::emit<OpcodeSize::Narrow>(&generator);
}

void ForInContext::finalize(BytecodeGenerator& generator, UnlinkedCodeBlockGenerator* codeBlock, unsigned bodyBytecodeEndOffset)
{
    // Lexically invalidating ForInContexts is kind of weak sauce, but it only occurs if
    // either of the following conditions is true:
    //
    // (1) The loop iteration variable is re-assigned within the body of the loop.
    // (2) The loop iteration variable is captured in the lexical scope of the function.
    //
    // These two situations occur sufficiently rarely that it's okay to use this style of
    // "analysis" to make iteration faster. If we didn't want to do this, we would either have
    // to perform some flow-sensitive analysis to see if/when the loop iteration variable was
    // reassigned, or we'd have to resort to runtime checks to see if the variable had been
    // reassigned from its original value.

    bool escaped = false;
    for (unsigned offset = bodyBytecodeStartOffset(); !escaped && offset < bodyBytecodeEndOffset;) {
        auto instruction = generator.instructions().at(offset);
        ASSERT(!instruction->is<OpEnter>());
        for (Checkpoint checkpoint = instruction->numberOfCheckpoints(); checkpoint--;) {
            computeDefsForBytecodeIndex(codeBlock, instruction.ptr(), checkpoint, [&] (VirtualRegister operand) {
                if (local()->virtualRegister() == operand)
                    escaped = true;
            });
        }
        offset += instruction->size();
    }

    if (!escaped)
        return;

    for (const auto& instTuple : m_getInsts)
        rewriteOp<OpEnumeratorGetByVal, OpGetByVal>(generator, instTuple);

    for (const auto& instTuple : m_inInsts)
        rewriteOp<OpEnumeratorInByVal, OpInByVal>(generator, instTuple);

    for (const auto& instTuple : m_putInsts) {
        unsigned instIndex = std::get<0>(instTuple);
        int propertyRegIndex = std::get<1>(instTuple);
        auto instruction = generator.m_writer.ref(instIndex);
        auto end = instIndex + instruction->size();
        ASSERT(instruction->isWide32());

        generator.m_writer.seek(instIndex);

        auto bytecode = instruction->as<OpEnumeratorPutByVal>();

        generator.disablePeepholeOptimization();

        static_assert(sizeof(OpPutByVal) <= sizeof(OpEnumeratorPutByVal));
        OpPutByVal::emit(&generator, bytecode.m_base, VirtualRegister(propertyRegIndex), bytecode.m_value, bytecode.m_ecmaMode);

        // 4. nop out the remaining bytes
        while (generator.m_writer.position() < end)
            OpNop::emit<OpcodeSize::Narrow>(&generator);
    }

    for (const auto& hasOwnPropertyTuple : m_hasOwnPropertyJumpInsts) {
        static_assert(sizeof(OpJmp) <= sizeof(OpJneqPtr));
        unsigned branchInstIndex = std::get<0>(hasOwnPropertyTuple);
        unsigned newBranchTarget = std::get<1>(hasOwnPropertyTuple);

        auto instruction = generator.m_writer.ref(branchInstIndex);
        RELEASE_ASSERT(instruction->is<OpJneqPtr>());
        RELEASE_ASSERT(instruction->isWide32());
        auto end = branchInstIndex + instruction->size();

        generator.m_writer.seek(branchInstIndex);
        generator.disablePeepholeOptimization();

        OpJmp::emit(&generator, BoundLabel(static_cast<int>(newBranchTarget) - static_cast<int>(branchInstIndex)));

        while (generator.m_writer.position() < end)
            OpNop::emit<OpcodeSize::Narrow>(&generator);
    }

    generator.m_writer.seek(generator.m_writer.size());
    generator.disablePeepholeOptimization(); // We might've just changed the last bytecode that was emitted.
}

void StaticPropertyAnalysis::record()
{
    auto* instruction = m_instructionRef.ptr();
    auto size = m_propertyIndexes.size();
    switch (instruction->opcodeID()) {
    case OpNewObject::opcodeID:
        instruction->cast<OpNewObject>()->setInlineCapacity(size, []() {
            return 255;
        });
        return;
    case OpCreateThis::opcodeID:
        instruction->cast<OpCreateThis>()->setInlineCapacity(size, []() {
            return 255;
        });
        return;
    default:
        ASSERT_NOT_REACHED();
    }
}

RegisterID* BytecodeGenerator::emitToThis(RegisterID* srcDst)
{
    OpToThis::emit(this, kill(srcDst), ecmaMode(), nextValueProfileIndex());
    return srcDst;
}

ForInContext* BytecodeGenerator::findForInContext(RegisterID* property)
{
    for (size_t i = m_forInContextStack.size(); i--; ) {
        ForInContext& context = m_forInContextStack[i].get();
        if (context.local() != property)
            continue;

        return &context;
    }

    return nullptr;
}

} // namespace JSC

namespace WTF {

void printInternal(PrintStream& out, JSC::Variable::VariableKind kind)
{
    switch (kind) {
    case JSC::Variable::NormalVariable:
        out.print("Normal");
        return;
    case JSC::Variable::SpecialVariable:
        out.print("Special");
        return;
    }
    RELEASE_ASSERT_NOT_REACHED();
}

} // namespace WTF

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END