X-Git-Url: https://git.saurik.com/apple/javascriptcore.git/blobdiff_plain/93a3786624b2768d89bfa27e46598dc64e2fb70a..HEAD:/bytecompiler/BytecodeGenerator.cpp

diff --git a/bytecompiler/BytecodeGenerator.cpp b/bytecompiler/BytecodeGenerator.cpp
index e719380..8b2f8e6 100644
--- a/bytecompiler/BytecodeGenerator.cpp
+++ b/bytecompiler/BytecodeGenerator.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008, 2009, 2012, 2013 Apple Inc. All rights reserved.
+ * Copyright (C) 2008, 2009, 2012-2015 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Cameron Zwarich <cwzwarich@uwaterloo.ca>
  * Copyright (C) 2012 Igalia, S.L.
  *
@@ -12,7 +12,7 @@
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
  *     documentation and/or other materials provided with the distribution.
- * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ * 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.
  *
@@ -31,16 +31,20 @@
 #include "config.h"
 #include "BytecodeGenerator.h"
 
-#include "BatchedTransitionOptimizer.h"
+#include "BuiltinExecutables.h"
 #include "Interpreter.h"
-#include "JSActivation.h"
 #include "JSFunction.h"
+#include "JSLexicalEnvironment.h"
 #include "JSNameScope.h"
+#include "JSTemplateRegistryKey.h"
 #include "LowLevelInterpreter.h"
-#include "Operations.h"
+#include "JSCInlines.h"
 #include "Options.h"
+#include "StackAlignment.h"
 #include "StrongInlines.h"
 #include "UnlinkedCodeBlock.h"
+#include "UnlinkedInstructionStream.h"
+#include <wtf/StdLibExtras.h>
 #include <wtf/text/WTFString.h>
 
 using namespace std;
@@ -53,37 +57,44 @@ void Label::setLocation(unsigned location)
     
     unsigned size = m_unresolvedJumps.size();
     for (unsigned i = 0; i < size; ++i)
-        m_generator->m_instructions[m_unresolvedJumps[i].second].u.operand = m_location - m_unresolvedJumps[i].first;
+        m_generator.instructions()[m_unresolvedJumps[i].second].u.operand = m_location - m_unresolvedJumps[i].first;
 }
 
-#ifndef NDEBUG
-void ResolveResult::checkValidity()
-{
-    switch (m_type) {
-    case Register:
-    case ReadOnlyRegister:
-        ASSERT(m_local);
-        return;
-    case Dynamic:
-        ASSERT(!m_local);
-        return;
-    case Lexical:
-    case ReadOnlyLexical:
-        ASSERT(!m_local);
-        return;
-    default:
-        RELEASE_ASSERT_NOT_REACHED();
-    }
-}
-#endif
-
 ParserError BytecodeGenerator::generate()
 {
     SamplingRegion samplingRegion("Bytecode Generation");
     
-    m_codeBlock->setThisRegister(m_thisRegister.index());
+    m_codeBlock->setThisRegister(m_thisRegister.virtualRegister());
+    
+    // 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);
+
+    for (size_t i = 0; i < m_destructuringParameters.size(); i++) {
+        auto& entry = m_destructuringParameters[i];
+        entry.second->bindValue(*this, entry.first.get());
+    }
 
-    m_scopeNode->emitBytecode(*this);
+    {
+        RefPtr<RegisterID> temp = newTemporary();
+        RefPtr<RegisterID> globalScope = scopeRegister(); // FIXME: With lexical scoping, this won't always be the global object: https://bugs.webkit.org/show_bug.cgi?id=142944 
+        for (auto functionPair : m_functionsToInitialize) {
+            FunctionBodyNode* functionBody = functionPair.first;
+            FunctionVariableType functionType = functionPair.second;
+            emitNewFunction(temp.get(), functionBody);
+            if (functionType == NormalFunctionVariable)
+                initializeVariable(variable(functionBody->ident()) , temp.get());
+            else if (functionType == GlobalFunctionVariable)
+                emitPutToScope(globalScope.get(), Variable(functionBody->ident()), temp.get(), ThrowIfNotFound);
+            else
+                RELEASE_ASSERT_NOT_REACHED();
+        }
+    }
+    
+    bool callingClassConstructor = constructorKind() != ConstructorKind::None && !isConstructor();
+    if (!callingClassConstructor)
+        m_scopeNode->emitBytecode(*this);
 
     m_staticPropertyAnalyzer.kill();
 
@@ -118,324 +129,394 @@ ParserError BytecodeGenerator::generate()
             continue;
         
         ASSERT(range.tryData->targetScopeDepth != UINT_MAX);
-        UnlinkedHandlerInfo info = {
-            static_cast<uint32_t>(start), static_cast<uint32_t>(end),
-            static_cast<uint32_t>(range.tryData->target->bind()),
-            range.tryData->targetScopeDepth
-        };
+        ASSERT(range.tryData->handlerType != HandlerType::Illegal);
+        UnlinkedHandlerInfo info(static_cast<uint32_t>(start), static_cast<uint32_t>(end),
+            static_cast<uint32_t>(range.tryData->target->bind()), range.tryData->targetScopeDepth,
+            range.tryData->handlerType);
         m_codeBlock->addExceptionHandler(info);
     }
     
-    m_codeBlock->instructions() = RefCountedArray<UnlinkedInstruction>(m_instructions);
+    m_codeBlock->setInstructions(std::make_unique<UnlinkedInstructionStream>(m_instructions));
 
     m_codeBlock->shrinkToFit();
 
+    if (m_codeBlock->symbolTable() && !m_codeBlock->vm()->typeProfiler())
+        m_codeBlock->setSymbolTable(m_codeBlock->symbolTable()->cloneScopePart(*m_codeBlock->vm()));
+
     if (m_expressionTooDeep)
         return ParserError(ParserError::OutOfMemory);
     return ParserError(ParserError::ErrorNone);
 }
 
-bool BytecodeGenerator::addVar(const Identifier& ident, bool isConstant, RegisterID*& r0)
-{
-    int index = m_calleeRegisters.size();
-    SymbolTableEntry newEntry(index, isConstant ? ReadOnly : 0);
-    SymbolTable::AddResult result = symbolTable().add(ident.impl(), newEntry);
-
-    if (!result.isNewEntry) {
-        r0 = &registerFor(result.iterator->value.getIndex());
-        return false;
-    }
-
-    r0 = addVar();
-    return true;
-}
-
-void BytecodeGenerator::preserveLastVar()
-{
-    if ((m_firstConstantIndex = m_calleeRegisters.size()) != 0)
-        m_lastVar = &m_calleeRegisters.last();
-}
-
-BytecodeGenerator::BytecodeGenerator(VM& vm, JSScope*, ProgramNode* programNode, UnlinkedProgramCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
-    : m_shouldEmitDebugHooks(debuggerMode == DebuggerOn)
-    , m_shouldEmitProfileHooks(profilerMode == ProfilerOn)
-    , m_symbolTable(0)
+BytecodeGenerator::BytecodeGenerator(VM& vm, ProgramNode* programNode, UnlinkedProgramCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
+    : m_shouldEmitDebugHooks(Options::forceDebuggerBytecodeGeneration() || debuggerMode == DebuggerOn)
+    , m_shouldEmitProfileHooks(Options::forceProfilerBytecodeGeneration() || profilerMode == ProfilerOn)
     , m_scopeNode(programNode)
     , m_codeBlock(vm, codeBlock)
     , m_thisRegister(CallFrame::thisArgumentOffset())
-    , m_emptyValueRegister(0)
-    , m_globalObjectRegister(0)
-    , m_finallyDepth(0)
-    , m_dynamicScopeDepth(0)
     , m_codeType(GlobalCode)
-    , m_nextConstantOffset(0)
-    , m_globalConstantIndex(0)
-    , m_hasCreatedActivation(true)
-    , m_firstLazyFunction(0)
-    , m_lastLazyFunction(0)
-    , m_staticPropertyAnalyzer(&m_instructions)
     , m_vm(&vm)
-    , m_lastOpcodeID(op_end)
-#ifndef NDEBUG
-    , m_lastOpcodePosition(0)
-#endif
-    , m_stack(wtfThreadData().stack())
-    , m_usesExceptions(false)
-    , m_expressionTooDeep(false)
 {
-    if (m_shouldEmitDebugHooks)
-        m_codeBlock->setNeedsFullScopeChain(true);
+    for (auto& constantRegister : m_linkTimeConstantRegisters)
+        constantRegister = nullptr;
 
     m_codeBlock->setNumParameters(1); // Allocate space for "this"
 
     emitOpcode(op_enter);
 
+    allocateAndEmitScope();
+
     const VarStack& varStack = programNode->varStack();
     const FunctionStack& functionStack = programNode->functionStack();
 
     for (size_t i = 0; i < functionStack.size(); ++i) {
         FunctionBodyNode* function = functionStack[i];
-        UnlinkedFunctionExecutable* unlinkedFunction = makeFunction(function);
-        codeBlock->addFunctionDeclaration(*m_vm, function->ident(), unlinkedFunction);
+        m_functionsToInitialize.append(std::make_pair(function, GlobalFunctionVariable));
     }
 
     for (size_t i = 0; i < varStack.size(); ++i)
-        codeBlock->addVariableDeclaration(*varStack[i].first, !!(varStack[i].second & DeclarationStacks::IsConstant));
+        codeBlock->addVariableDeclaration(varStack[i].first, !!(varStack[i].second & DeclarationStacks::IsConstant));
 
 }
 
-BytecodeGenerator::BytecodeGenerator(VM& vm, JSScope* scope, FunctionBodyNode* functionBody, UnlinkedFunctionCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
-    : m_shouldEmitDebugHooks(debuggerMode == DebuggerOn)
-    , m_shouldEmitProfileHooks(profilerMode == ProfilerOn)
+BytecodeGenerator::BytecodeGenerator(VM& vm, FunctionNode* functionNode, UnlinkedFunctionCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
+    : m_shouldEmitDebugHooks(Options::forceDebuggerBytecodeGeneration() || debuggerMode == DebuggerOn)
+    , m_shouldEmitProfileHooks(Options::forceProfilerBytecodeGeneration() || profilerMode == ProfilerOn)
     , m_symbolTable(codeBlock->symbolTable())
-    , m_scopeNode(functionBody)
-    , m_scope(vm, scope)
+    , m_scopeNode(functionNode)
     , m_codeBlock(vm, codeBlock)
-    , m_activationRegister(0)
-    , m_emptyValueRegister(0)
-    , m_globalObjectRegister(0)
-    , m_finallyDepth(0)
-    , m_dynamicScopeDepth(0)
     , m_codeType(FunctionCode)
-    , m_nextConstantOffset(0)
-    , m_globalConstantIndex(0)
-    , m_hasCreatedActivation(false)
-    , m_firstLazyFunction(0)
-    , m_lastLazyFunction(0)
-    , m_staticPropertyAnalyzer(&m_instructions)
     , m_vm(&vm)
-    , m_lastOpcodeID(op_end)
-#ifndef NDEBUG
-    , m_lastOpcodePosition(0)
-#endif
-    , m_stack(wtfThreadData().stack())
-    , m_usesExceptions(false)
-    , m_expressionTooDeep(false)
+    , m_isBuiltinFunction(codeBlock->isBuiltinFunction())
 {
-    if (m_shouldEmitDebugHooks)
-        m_codeBlock->setNeedsFullScopeChain(true);
+    for (auto& constantRegister : m_linkTimeConstantRegisters)
+        constantRegister = nullptr;
 
+    if (m_isBuiltinFunction)
+        m_shouldEmitDebugHooks = false;
+    
     m_symbolTable->setUsesNonStrictEval(codeBlock->usesEval() && !codeBlock->isStrictMode());
-    m_symbolTable->setParameterCountIncludingThis(functionBody->parameters()->size() + 1);
-
-    emitOpcode(op_enter);
-    if (m_codeBlock->needsFullScopeChain()) {
-        m_activationRegister = addVar();
-        emitInitLazyRegister(m_activationRegister);
-        m_codeBlock->setActivationRegister(m_activationRegister->index());
+    Vector<Identifier> boundParameterProperties;
+    FunctionParameters& parameters = *functionNode->parameters();
+    for (size_t i = 0; i < parameters.size(); i++) {
+        auto pattern = parameters.at(i);
+        if (pattern->isBindingNode())
+            continue;
+        pattern->collectBoundIdentifiers(boundParameterProperties);
+        continue;
     }
 
-    m_symbolTable->setCaptureStart(m_codeBlock->m_numVars);
-
-    if (functionBody->usesArguments() || codeBlock->usesEval() || m_shouldEmitDebugHooks) { // May reify arguments object.
-        RegisterID* unmodifiedArgumentsRegister = addVar(); // Anonymous, so it can't be modified by user code.
-        RegisterID* argumentsRegister = addVar(propertyNames().arguments, false); // Can be changed by assigning to 'arguments'.
-
-        // We can save a little space by hard-coding the knowledge that the two
-        // 'arguments' values are stored in consecutive registers, and storing
-        // only the index of the assignable one.
-        codeBlock->setArgumentsRegister(argumentsRegister->index());
-        ASSERT_UNUSED(unmodifiedArgumentsRegister, unmodifiedArgumentsRegister->index() == JSC::unmodifiedArgumentsRegister(codeBlock->argumentsRegister()));
-
-        emitInitLazyRegister(argumentsRegister);
-        emitInitLazyRegister(unmodifiedArgumentsRegister);
-        
-        if (m_codeBlock->isStrictMode()) {
-            emitOpcode(op_create_arguments);
-            instructions().append(argumentsRegister->index());
+    bool shouldCaptureSomeOfTheThings = m_shouldEmitDebugHooks || m_codeBlock->needsFullScopeChain();
+    bool shouldCaptureAllOfTheThings = m_shouldEmitDebugHooks || codeBlock->usesEval();
+    bool needsArguments = functionNode->usesArguments() || codeBlock->usesEval();
+    
+    auto captures = [&] (UniquedStringImpl* uid) -> bool {
+        if (shouldCaptureAllOfTheThings)
+            return true;
+        if (!shouldCaptureSomeOfTheThings)
+            return false;
+        if (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;
+    };
 
-        // The debugger currently retrieves the arguments object from an activation rather than pulling
-        // it from a call frame.  In the long-term it should stop doing that (<rdar://problem/6911886>),
-        // but for now we force eager creation of the arguments object when debugging.
-        if (m_shouldEmitDebugHooks) {
-            emitOpcode(op_create_arguments);
-            instructions().append(argumentsRegister->index());
-        }
-    }
+    emitOpcode(op_enter);
 
-    bool shouldCaptureAllTheThings = m_shouldEmitDebugHooks || codeBlock->usesEval();
+    allocateAndEmitScope();
+    
+    m_calleeRegister.setIndex(JSStack::Callee);
+    
+    if (functionNameIsInScope(functionNode->ident(), functionNode->functionMode())
+        && functionNameScopeIsDynamic(codeBlock->usesEval(), codeBlock->isStrictMode())) {
+        // When we do this, we should make our local scope stack know about the function name symbol
+        // table. Currently this works because bytecode linking creates a phony name scope.
+        // FIXME: https://bugs.webkit.org/show_bug.cgi?id=141885
+        // Also, we could create the scope once per JSFunction instance that needs it. That wouldn't
+        // be any more correct, but it would be more performant.
+        // FIXME: https://bugs.webkit.org/show_bug.cgi?id=141887
+        emitPushFunctionNameScope(m_scopeRegister, functionNode->ident(), &m_calleeRegister, ReadOnly | DontDelete);
+    }
 
+    if (shouldCaptureSomeOfTheThings) {
+        m_lexicalEnvironmentRegister = addVar();
+        m_codeBlock->setActivationRegister(m_lexicalEnvironmentRegister->virtualRegister());
+        emitOpcode(op_create_lexical_environment);
+        instructions().append(m_lexicalEnvironmentRegister->index());
+        instructions().append(scopeRegister()->index());
+        emitOpcode(op_mov);
+        instructions().append(scopeRegister()->index());
+        instructions().append(m_lexicalEnvironmentRegister->index());
+    }
+    
+    // Make sure the code block knows about all of our parameters, and make sure that parameters
+    // needing destructuring are noted.
+    m_parameters.grow(parameters.size() + 1); // reserve space for "this"
+    m_thisRegister.setIndex(initializeNextParameter()->index()); // this
+    for (unsigned i = 0; i < parameters.size(); ++i) {
+        auto pattern = parameters.at(i);
+        RegisterID* reg = initializeNextParameter();
+        if (!pattern->isBindingNode())
+            m_destructuringParameters.append(std::make_pair(reg, pattern));
+    }
+    
+    // Figure out some interesting facts about our arguments.
     bool capturesAnyArgumentByName = false;
-    Vector<RegisterID*, 0, UnsafeVectorOverflow> capturedArguments;
-    if (functionBody->hasCapturedVariables() || shouldCaptureAllTheThings) {
-        FunctionParameters& parameters = *functionBody->parameters();
-        capturedArguments.resize(parameters.size());
+    if (functionNode->hasCapturedVariables()) {
+        FunctionParameters& parameters = *functionNode->parameters();
         for (size_t i = 0; i < parameters.size(); ++i) {
-            capturedArguments[i] = 0;
-            if (!functionBody->captures(parameters.at(i)) && !shouldCaptureAllTheThings)
+            auto pattern = parameters.at(i);
+            if (!pattern->isBindingNode())
                 continue;
-            capturesAnyArgumentByName = true;
-            capturedArguments[i] = addVar();
+            const Identifier& ident = static_cast<const BindingNode*>(pattern)->boundProperty();
+            capturesAnyArgumentByName |= captures(ident.impl());
         }
     }
 
-    if (capturesAnyArgumentByName && !codeBlock->isStrictMode()) {
-        size_t parameterCount = m_symbolTable->parameterCount();
-        OwnArrayPtr<SlowArgument> slowArguments = adoptArrayPtr(new SlowArgument[parameterCount]);
-        for (size_t i = 0; i < parameterCount; ++i) {
-            if (!capturedArguments[i]) {
-                ASSERT(slowArguments[i].status == SlowArgument::Normal);
-                slowArguments[i].index = CallFrame::argumentOffset(i);
-                continue;
-            }
-            slowArguments[i].status = SlowArgument::Captured;
-            slowArguments[i].index = capturedArguments[i]->index();
-        }
-        m_symbolTable->setSlowArguments(slowArguments.release());
-    }
-
-    RegisterID* calleeRegister = resolveCallee(functionBody); // May push to the scope chain and/or add a captured var.
-
-    const DeclarationStacks::FunctionStack& functionStack = functionBody->functionStack();
-    const DeclarationStacks::VarStack& varStack = functionBody->varStack();
-
-    // Captured variables and functions go first so that activations don't have
-    // to step over the non-captured locals to mark them.
-    m_hasCreatedActivation = false;
-    if (functionBody->hasCapturedVariables()) {
-        for (size_t i = 0; i < functionStack.size(); ++i) {
-            FunctionBodyNode* function = functionStack[i];
-            const Identifier& ident = function->ident();
-            if (functionBody->captures(ident)) {
-                if (!m_hasCreatedActivation) {
-                    m_hasCreatedActivation = true;
-                    emitOpcode(op_create_activation);
-                    instructions().append(m_activationRegister->index());
+    if (capturesAnyArgumentByName)
+        ASSERT(m_lexicalEnvironmentRegister);
+    
+    // Need to know what our functions are called. Parameters have some goofy behaviors when it
+    // comes to functions of the same name.
+    for (FunctionBodyNode* function : functionNode->functionStack())
+        m_functions.add(function->ident().impl());
+    
+    if (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 (needsArguments && !codeBlock->isStrictMode()) {
+        // 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.
+        
+        if (capturesAnyArgumentByName) {
+            m_symbolTable->setArgumentsLength(vm, parameters.size());
+            
+            // 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 = m_symbolTable->takeNextScopeOffset();
+                m_symbolTable->setArgumentOffset(vm, i, offset);
+                if (UniquedStringImpl* name = visibleNameForParameter(parameters.at(i))) {
+                    VarOffset varOffset(offset);
+                    SymbolTableEntry entry(varOffset);
+                    // Stores to these variables via the ScopedArguments object will not do
+                    // notifyWrite(), since that would be cumbersome. Also, watching formal
+                    // parameters when "arguments" is in play is unlikely to be super profitable.
+                    // So, we just disable it.
+                    entry.disableWatching();
+                    m_symbolTable->set(name, entry);
                 }
-                m_functions.add(ident.impl());
-                emitNewFunction(addVar(ident, false), function);
+                emitOpcode(op_put_to_scope);
+                instructions().append(m_lexicalEnvironmentRegister->index());
+                instructions().append(UINT_MAX);
+                instructions().append(virtualRegisterForArgument(1 + i).offset());
+                instructions().append(ResolveModeAndType(ThrowIfNotFound, LocalClosureVar).operand());
+                instructions().append(0);
+                instructions().append(offset.offset());
+            }
+            
+            // This creates a scoped arguments object and copies the overflow arguments into the
+            // scope. It's the equivalent of calling ScopedArguments::createByCopying().
+            emitOpcode(op_create_scoped_arguments);
+            instructions().append(m_argumentsRegister->index());
+            instructions().append(m_lexicalEnvironmentRegister->index());
+        } 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)))
+                    m_symbolTable->set(name, SymbolTableEntry(VarOffset(DirectArgumentsOffset(i))));
             }
+            
+            emitOpcode(op_create_direct_arguments);
+            instructions().append(m_argumentsRegister->index());
         }
-        for (size_t i = 0; i < varStack.size(); ++i) {
-            const Identifier& ident = *varStack[i].first;
-            if (functionBody->captures(ident))
-                addVar(ident, varStack[i].second & DeclarationStacks::IsConstant);
+    } else {
+        // Create the formal parameters the normal way. Any of them could be captured, or not. If
+        // captured, lift them into the scope.
+        for (unsigned i = 0; i < parameters.size(); ++i) {
+            UniquedStringImpl* name = visibleNameForParameter(parameters.at(i));
+            if (!name)
+                continue;
+            
+            if (!captures(name)) {
+                // This is the easy case - just tell the symbol table about the argument. It will
+                // be accessed directly.
+                m_symbolTable->set(name, SymbolTableEntry(VarOffset(virtualRegisterForArgument(1 + i))));
+                continue;
+            }
+            
+            ScopeOffset offset = m_symbolTable->takeNextScopeOffset();
+            const Identifier& ident =
+                static_cast<const BindingNode*>(parameters.at(i))->boundProperty();
+            m_symbolTable->set(name, SymbolTableEntry(VarOffset(offset)));
+            
+            emitOpcode(op_put_to_scope);
+            instructions().append(m_lexicalEnvironmentRegister->index());
+            instructions().append(addConstant(ident));
+            instructions().append(virtualRegisterForArgument(1 + i).offset());
+            instructions().append(ResolveModeAndType(ThrowIfNotFound, LocalClosureVar).operand());
+            instructions().append(0);
+            instructions().append(offset.offset());
         }
     }
-    bool canLazilyCreateFunctions = !functionBody->needsActivationForMoreThanVariables() && !m_shouldEmitDebugHooks;
-    if (!canLazilyCreateFunctions && !m_hasCreatedActivation) {
-        m_hasCreatedActivation = true;
-        emitOpcode(op_create_activation);
-        instructions().append(m_activationRegister->index());
+    
+    if (needsArguments && codeBlock->isStrictMode()) {
+        // Allocate an out-of-bands arguments object.
+        emitOpcode(op_create_out_of_band_arguments);
+        instructions().append(m_argumentsRegister->index());
     }
-
-    m_symbolTable->setCaptureEnd(codeBlock->m_numVars);
-
-    m_firstLazyFunction = codeBlock->m_numVars;
-    for (size_t i = 0; i < functionStack.size(); ++i) {
-        FunctionBodyNode* function = functionStack[i];
+    
+    // Now declare all variables.
+    for (const Identifier& ident : boundParameterProperties)
+        createVariable(ident, varKind(ident.impl()), IsVariable);
+    for (FunctionBodyNode* function : functionNode->functionStack()) {
         const Identifier& ident = function->ident();
-        if (!functionBody->captures(ident)) {
-            m_functions.add(ident.impl());
-            RefPtr<RegisterID> reg = addVar(ident, false);
-            // Don't lazily create functions that override the name 'arguments'
-            // as this would complicate lazy instantiation of actual arguments.
-            if (!canLazilyCreateFunctions || ident == propertyNames().arguments)
-                emitNewFunction(reg.get(), function);
-            else {
-                emitInitLazyRegister(reg.get());
-                m_lazyFunctions.set(reg->index(), function);
+        createVariable(ident, varKind(ident.impl()), IsVariable);
+        m_functionsToInitialize.append(std::make_pair(function, NormalFunctionVariable));
+    }
+    for (auto& entry : functionNode->varStack()) {
+        ConstantMode constantMode = modeForIsConstant(entry.second & DeclarationStacks::IsConstant);
+        // Variables named "arguments" are never const.
+        if (entry.first == propertyNames().arguments)
+            constantMode = IsVariable;
+        createVariable(entry.first, varKind(entry.first.impl()), constantMode, IgnoreExisting);
+    }
+    
+    // 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.
+    //
+    // - callee: unless it's used as a var, function, or parameter, this should refer to the
+    //   callee (i.e. our function).
+    //
+    // - 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 the callee
+    // first, then "arguments", 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).
+    //
+    // We also initialize callee here as well, just because it's so weird. We know whether we want
+    // to do this because we can just check if it's in the symbol table.
+    if (functionNameIsInScope(functionNode->ident(), functionNode->functionMode())
+        && !functionNameScopeIsDynamic(codeBlock->usesEval(), codeBlock->isStrictMode())
+        && m_symbolTable->get(functionNode->ident().impl()).isNull()) {
+        if (captures(functionNode->ident().impl())) {
+            ScopeOffset offset;
+            {
+                ConcurrentJITLocker locker(m_symbolTable->m_lock);
+                offset = m_symbolTable->takeNextScopeOffset(locker);
+                m_symbolTable->add(
+                    locker, functionNode->ident().impl(),
+                    SymbolTableEntry(VarOffset(offset), ReadOnly));
             }
+            
+            emitOpcode(op_put_to_scope);
+            instructions().append(m_lexicalEnvironmentRegister->index());
+            instructions().append(addConstant(functionNode->ident()));
+            instructions().append(m_calleeRegister.index());
+            instructions().append(ResolveModeAndType(ThrowIfNotFound, LocalClosureVar).operand());
+            instructions().append(0);
+            instructions().append(offset.offset());
+        } else {
+            m_symbolTable->add(
+                functionNode->ident().impl(),
+                SymbolTableEntry(VarOffset(m_calleeRegister.virtualRegister()), ReadOnly));
         }
     }
-    m_lastLazyFunction = canLazilyCreateFunctions ? codeBlock->m_numVars : m_firstLazyFunction;
-    for (size_t i = 0; i < varStack.size(); ++i) {
-        const Identifier& ident = *varStack[i].first;
-        if (!functionBody->captures(ident))
-            addVar(ident, varStack[i].second & DeclarationStacks::IsConstant);
-    }
-
-    if (shouldCaptureAllTheThings)
-        m_symbolTable->setCaptureEnd(codeBlock->m_numVars);
-
-    FunctionParameters& parameters = *functionBody->parameters();
-    m_parameters.grow(parameters.size() + 1); // reserve space for "this"
-
-    // Add "this" as a parameter
-    int nextParameterIndex = CallFrame::thisArgumentOffset();
-    m_thisRegister.setIndex(nextParameterIndex--);
-    m_codeBlock->addParameter();
     
-    for (size_t i = 0; i < parameters.size(); ++i, --nextParameterIndex) {
-        int index = nextParameterIndex;
-        if (capturedArguments.size() && capturedArguments[i]) {
-            ASSERT((functionBody->hasCapturedVariables() && functionBody->captures(parameters.at(i))) || shouldCaptureAllTheThings);
-            index = capturedArguments[i]->index();
-            RegisterID original(nextParameterIndex);
-            emitMove(capturedArguments[i], &original);
+    // 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.
+    if (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));
+            if (name == propertyNames().arguments.impl()) {
+                haveParameterNamedArguments = true;
+                break;
+            }
+        }
+        
+        if (!haveParameterNamedArguments) {
+            createVariable(
+                propertyNames().arguments, varKind(propertyNames().arguments.impl()), IsVariable);
+            m_needToInitializeArguments = true;
         }
-        addParameter(parameters.at(i), index);
     }
-    preserveLastVar();
-
-    // We declare the callee's name last because it should lose to a var, function, and/or parameter declaration.
-    addCallee(functionBody, calleeRegister);
-
+    
     if (isConstructor()) {
-        emitCreateThis(&m_thisRegister);
-    } else if (!codeBlock->isStrictMode() && (functionBody->usesThis() || codeBlock->usesEval() || m_shouldEmitDebugHooks)) {
-        UnlinkedValueProfile profile = emitProfiledOpcode(op_convert_this);
+        if (constructorKind() == ConstructorKind::Derived) {
+            m_newTargetRegister = addVar();
+            emitMove(m_newTargetRegister, &m_thisRegister);
+            emitMoveEmptyValue(&m_thisRegister);
+        } else
+            emitCreateThis(&m_thisRegister);
+    } else if (constructorKind() != ConstructorKind::None) {
+        emitThrowTypeError("Cannot call a class constructor");
+    } else if (functionNode->usesThis() || codeBlock->usesEval()) {
+        m_codeBlock->addPropertyAccessInstruction(instructions().size());
+        emitOpcode(op_to_this);
         instructions().append(kill(&m_thisRegister));
-        instructions().append(profile);
+        instructions().append(0);
+        instructions().append(0);
     }
 }
 
-BytecodeGenerator::BytecodeGenerator(VM& vm, JSScope* scope, EvalNode* evalNode, UnlinkedEvalCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
-    : m_shouldEmitDebugHooks(debuggerMode == DebuggerOn)
-    , m_shouldEmitProfileHooks(profilerMode == ProfilerOn)
+BytecodeGenerator::BytecodeGenerator(VM& vm, EvalNode* evalNode, UnlinkedEvalCodeBlock* codeBlock, DebuggerMode debuggerMode, ProfilerMode profilerMode)
+    : m_shouldEmitDebugHooks(Options::forceDebuggerBytecodeGeneration() || debuggerMode == DebuggerOn)
+    , m_shouldEmitProfileHooks(Options::forceProfilerBytecodeGeneration() || profilerMode == ProfilerOn)
     , m_symbolTable(codeBlock->symbolTable())
     , m_scopeNode(evalNode)
-    , m_scope(vm, scope)
     , m_codeBlock(vm, codeBlock)
     , m_thisRegister(CallFrame::thisArgumentOffset())
-    , m_emptyValueRegister(0)
-    , m_globalObjectRegister(0)
-    , m_finallyDepth(0)
-    , m_dynamicScopeDepth(0)
     , m_codeType(EvalCode)
-    , m_nextConstantOffset(0)
-    , m_globalConstantIndex(0)
-    , m_hasCreatedActivation(true)
-    , m_firstLazyFunction(0)
-    , m_lastLazyFunction(0)
-    , m_staticPropertyAnalyzer(&m_instructions)
     , m_vm(&vm)
-    , m_lastOpcodeID(op_end)
-#ifndef NDEBUG
-    , m_lastOpcodePosition(0)
-#endif
-    , m_stack(wtfThreadData().stack())
-    , m_usesExceptions(false)
-    , m_expressionTooDeep(false)
 {
-    m_codeBlock->setNeedsFullScopeChain(true);
+    for (auto& constantRegister : m_linkTimeConstantRegisters)
+        constantRegister = nullptr;
 
     m_symbolTable->setUsesNonStrictEval(codeBlock->usesEval() && !codeBlock->isStrictMode());
     m_codeBlock->setNumParameters(1);
 
     emitOpcode(op_enter);
 
+    allocateAndEmitScope();
+
     const DeclarationStacks::FunctionStack& functionStack = evalNode->functionStack();
     for (size_t i = 0; i < functionStack.size(); ++i)
         m_codeBlock->addFunctionDecl(makeFunction(functionStack[i]));
@@ -444,113 +525,42 @@ BytecodeGenerator::BytecodeGenerator(VM& vm, JSScope* scope, EvalNode* evalNode,
     unsigned numVariables = varStack.size();
     Vector<Identifier, 0, UnsafeVectorOverflow> variables;
     variables.reserveCapacity(numVariables);
-    for (size_t i = 0; i < numVariables; ++i)
-        variables.append(*varStack[i].first);
+    for (size_t i = 0; i < numVariables; ++i) {
+        ASSERT(varStack[i].first.impl()->isAtomic() || varStack[i].first.impl()->isSymbol());
+        variables.append(varStack[i].first);
+    }
     codeBlock->adoptVariables(variables);
-    preserveLastVar();
 }
 
 BytecodeGenerator::~BytecodeGenerator()
 {
 }
 
-RegisterID* BytecodeGenerator::emitInitLazyRegister(RegisterID* reg)
-{
-    emitOpcode(op_init_lazy_reg);
-    instructions().append(reg->index());
-    return reg;
-}
-
-RegisterID* BytecodeGenerator::resolveCallee(FunctionBodyNode* functionBodyNode)
-{
-    if (functionBodyNode->ident().isNull() || !functionBodyNode->functionNameIsInScope())
-        return 0;
-
-    m_calleeRegister.setIndex(JSStack::Callee);
-
-    // If non-strict eval is in play, we use a separate object in the scope chain for the callee's name.
-    if ((m_codeBlock->usesEval() && !m_codeBlock->isStrictMode()) || m_shouldEmitDebugHooks) {
-        emitOpcode(op_push_name_scope);
-        instructions().append(addConstant(functionBodyNode->ident()));
-        instructions().append(m_calleeRegister.index());
-        instructions().append(ReadOnly | DontDelete);
-        return 0;
-    }
-
-    if (!functionBodyNode->captures(functionBodyNode->ident()))
-        return &m_calleeRegister;
-
-    // Move the callee into the captured section of the stack.
-    return emitMove(addVar(), &m_calleeRegister);
-}
-
-void BytecodeGenerator::addCallee(FunctionBodyNode* functionBodyNode, RegisterID* calleeRegister)
-{
-    if (functionBodyNode->ident().isNull() || !functionBodyNode->functionNameIsInScope())
-        return;
-
-    // If non-strict eval is in play, we use a separate object in the scope chain for the callee's name.
-    if ((m_codeBlock->usesEval() && !m_codeBlock->isStrictMode()) || m_shouldEmitDebugHooks)
-        return;
-
-    ASSERT(calleeRegister);
-    symbolTable().add(functionBodyNode->ident().impl(), SymbolTableEntry(calleeRegister->index(), ReadOnly));
-}
-
-void BytecodeGenerator::addParameter(const Identifier& ident, int parameterIndex)
+RegisterID* BytecodeGenerator::initializeNextParameter()
 {
-    // Parameters overwrite var declarations, but not function declarations.
-    StringImpl* rep = ident.impl();
-    if (!m_functions.contains(rep)) {
-        symbolTable().set(rep, parameterIndex);
-        RegisterID& parameter = registerFor(parameterIndex);
-        parameter.setIndex(parameterIndex);
-    }
-
-    // To maintain the calling convention, we have to allocate unique space for
-    // each parameter, even if the parameter doesn't make it into the symbol table.
+    VirtualRegister reg = virtualRegisterForArgument(m_codeBlock->numParameters());
+    RegisterID& parameter = registerFor(reg);
+    parameter.setIndex(reg.offset());
     m_codeBlock->addParameter();
+    return &parameter;
 }
 
-bool BytecodeGenerator::willResolveToArguments(const Identifier& ident)
-{
-    if (ident != propertyNames().arguments)
-        return false;
-    
-    if (!shouldOptimizeLocals())
-        return false;
-    
-    SymbolTableEntry entry = symbolTable().get(ident.impl());
-    if (entry.isNull())
-        return false;
-
-    if (m_codeBlock->usesArguments() && m_codeType == FunctionCode)
-        return true;
-    
-    return false;
-}
-
-RegisterID* BytecodeGenerator::uncheckedRegisterForArguments()
+UniquedStringImpl* BytecodeGenerator::visibleNameForParameter(DestructuringPatternNode* pattern)
 {
-    ASSERT(willResolveToArguments(propertyNames().arguments));
-
-    SymbolTableEntry entry = symbolTable().get(propertyNames().arguments.impl());
-    ASSERT(!entry.isNull());
-    return &registerFor(entry.getIndex());
-}
-
-RegisterID* BytecodeGenerator::createLazyRegisterIfNecessary(RegisterID* reg)
-{
-    if (m_lastLazyFunction <= reg->index() || reg->index() < m_firstLazyFunction)
-        return reg;
-    emitLazyNewFunction(reg, m_lazyFunctions.get(reg->index()));
-    return reg;
+    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::newRegister()
 {
-    m_calleeRegisters.append(m_calleeRegisters.size());
-    m_codeBlock->m_numCalleeRegisters = max<int>(m_codeBlock->m_numCalleeRegisters, m_calleeRegisters.size());
+    m_calleeRegisters.append(virtualRegisterForLocal(m_calleeRegisters.size()));
+    int numCalleeRegisters = max<int>(m_codeBlock->m_numCalleeRegisters, m_calleeRegisters.size());
+    numCalleeRegisters = WTF::roundUpToMultipleOf(stackAlignmentRegisters(), numCalleeRegisters);
+    m_codeBlock->m_numCalleeRegisters = numCalleeRegisters;
     return &m_calleeRegisters.last();
 }
 
@@ -574,7 +584,7 @@ LabelScopePtr BytecodeGenerator::newLabelScope(LabelScope::Type type, const Iden
     // Allocate new label scope.
     LabelScope scope(type, name, scopeDepth(), newLabel(), type == LabelScope::Loop ? newLabel() : PassRefPtr<Label>()); // Only loops have continue targets.
     m_labelScopes.append(scope);
-    return LabelScopePtr(&m_labelScopes, m_labelScopes.size() - 1);
+    return LabelScopePtr(m_labelScopes, m_labelScopes.size() - 1);
 }
 
 PassRefPtr<Label> BytecodeGenerator::newLabel()
@@ -584,7 +594,7 @@ PassRefPtr<Label> BytecodeGenerator::newLabel()
         m_labels.removeLast();
 
     // Allocate new label ID.
-    m_labels.append(this);
+    m_labels.append(*this);
     return &m_labels.last();
 }
 
@@ -622,20 +632,12 @@ void BytecodeGenerator::emitOpcode(OpcodeID opcodeID)
 
 UnlinkedArrayProfile BytecodeGenerator::newArrayProfile()
 {
-#if ENABLE(VALUE_PROFILER)
     return m_codeBlock->addArrayProfile();
-#else
-    return 0;
-#endif
 }
 
 UnlinkedArrayAllocationProfile BytecodeGenerator::newArrayAllocationProfile()
 {
-#if ENABLE(VALUE_PROFILER)
     return m_codeBlock->addArrayAllocationProfile();
-#else
-    return 0;
-#endif
 }
 
 UnlinkedObjectAllocationProfile BytecodeGenerator::newObjectAllocationProfile()
@@ -645,11 +647,7 @@ UnlinkedObjectAllocationProfile BytecodeGenerator::newObjectAllocationProfile()
 
 UnlinkedValueProfile BytecodeGenerator::emitProfiledOpcode(OpcodeID opcodeID)
 {
-#if ENABLE(VALUE_PROFILER)
     UnlinkedValueProfile result = m_codeBlock->addValueProfile();
-#else
-    UnlinkedValueProfile result = 0;
-#endif
     emitOpcode(opcodeID);
     return result;
 }
@@ -954,12 +952,18 @@ PassRefPtr<Label> BytecodeGenerator::emitJumpIfNotFunctionApply(RegisterID* cond
     return target;
 }
 
+bool BytecodeGenerator::hasConstant(const Identifier& ident) const
+{
+    UniquedStringImpl* rep = ident.impl();
+    return m_identifierMap.contains(rep);
+}
+
 unsigned BytecodeGenerator::addConstant(const Identifier& ident)
 {
-    StringImpl* rep = ident.impl();
+    UniquedStringImpl* rep = ident.impl();
     IdentifierMap::AddResult result = m_identifierMap.add(rep, m_codeBlock->numberOfIdentifiers());
     if (result.isNewEntry)
-        m_codeBlock->addIdentifier(Identifier(m_vm, rep));
+        m_codeBlock->addIdentifier(ident);
 
     return result.iterator->value;
 }
@@ -978,34 +982,69 @@ RegisterID* BytecodeGenerator::addConstantEmptyValue()
     return m_emptyValueRegister;
 }
 
-RegisterID* BytecodeGenerator::addConstantValue(JSValue v)
+RegisterID* BytecodeGenerator::addConstantValue(JSValue v, SourceCodeRepresentation sourceCodeRepresentation)
 {
     if (!v)
         return addConstantEmptyValue();
 
     int index = m_nextConstantOffset;
-    JSValueMap::AddResult result = m_jsValueMap.add(JSValue::encode(v), m_nextConstantOffset);
+
+    EncodedJSValueWithRepresentation valueMapKey { JSValue::encode(v), sourceCodeRepresentation };
+    JSValueMap::AddResult result = m_jsValueMap.add(valueMapKey, m_nextConstantOffset);
     if (result.isNewEntry) {
         m_constantPoolRegisters.append(FirstConstantRegisterIndex + m_nextConstantOffset);
         ++m_nextConstantOffset;
-        m_codeBlock->addConstant(v);
+        m_codeBlock->addConstant(v, sourceCodeRepresentation);
     } else
         index = result.iterator->value;
     return &m_constantPoolRegisters[index];
 }
 
+RegisterID* BytecodeGenerator::emitMoveLinkTimeConstant(RegisterID* dst, LinkTimeConstant type)
+{
+    unsigned constantIndex = static_cast<unsigned>(type);
+    if (!m_linkTimeConstantRegisters[constantIndex]) {
+        int index = m_nextConstantOffset;
+        m_constantPoolRegisters.append(FirstConstantRegisterIndex + m_nextConstantOffset);
+        ++m_nextConstantOffset;
+        m_codeBlock->addConstant(type);
+        m_linkTimeConstantRegisters[constantIndex] = &m_constantPoolRegisters[index];
+    }
+
+    emitOpcode(op_mov);
+    instructions().append(dst->index());
+    instructions().append(m_linkTimeConstantRegisters[constantIndex]->index());
+
+    return dst;
+}
+
 unsigned BytecodeGenerator::addRegExp(RegExp* r)
 {
     return m_codeBlock->addRegExp(r);
 }
 
+RegisterID* BytecodeGenerator::emitMoveEmptyValue(RegisterID* dst)
+{
+    RefPtr<RegisterID> emptyValue = addConstantEmptyValue();
+
+    emitOpcode(op_mov);
+    instructions().append(dst->index());
+    instructions().append(emptyValue->index());
+    return dst;
+}
+
 RegisterID* BytecodeGenerator::emitMove(RegisterID* dst, RegisterID* src)
 {
-    m_staticPropertyAnalyzer.mov(dst->index(), src->index());
+    ASSERT(src != m_emptyValueRegister);
 
+    m_staticPropertyAnalyzer.mov(dst->index(), src->index());
     emitOpcode(op_mov);
     instructions().append(dst->index());
     instructions().append(src->index());
+
+    if (!dst->isTemporary() && vm()->typeProfiler())
+        emitProfileType(dst, ProfileTypeBytecodeHasGlobalID, nullptr);
+
     return dst;
 }
 
@@ -1088,7 +1127,7 @@ RegisterID* BytecodeGenerator::emitEqualityOp(OpcodeID opcodeID, RegisterID* dst
             }
             if (value == "object") {
                 rewindUnaryOp();
-                emitOpcode(op_is_object);
+                emitOpcode(op_is_object_or_null);
                 instructions().append(dst->index());
                 instructions().append(srcIndex);
                 return dst;
@@ -1110,35 +1149,56 @@ RegisterID* BytecodeGenerator::emitEqualityOp(OpcodeID opcodeID, RegisterID* dst
     return dst;
 }
 
-RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, bool b)
+void BytecodeGenerator::emitTypeProfilerExpressionInfo(const JSTextPosition& startDivot, const JSTextPosition& endDivot)
 {
-    return emitLoad(dst, jsBoolean(b));
+    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, const Identifier* identifier)
+{
+    if (flag == ProfileTypeBytecodeGetFromScope || flag == ProfileTypeBytecodePutToScope)
+        RELEASE_ASSERT(identifier);
+
+    // The format of this instruction is: op_profile_type regToProfile, TypeLocation*, flag, identifier?, resolveType?
+    emitOpcode(op_profile_type);
+    instructions().append(registerToProfile->index());
+    instructions().append(0);
+    instructions().append(flag);
+    instructions().append(identifier ? addConstant(*identifier) : 0);
+    instructions().append(resolveType());
+}
+
+void BytecodeGenerator::emitProfileControlFlow(int textOffset)
+{
+    if (vm()->controlFlowProfiler()) {
+        RELEASE_ASSERT(textOffset >= 0);
+        size_t bytecodeOffset = instructions().size();
+        m_codeBlock->addOpProfileControlFlowBytecodeOffset(bytecodeOffset);
+
+        emitOpcode(op_profile_control_flow);
+        instructions().append(textOffset);
+    }
 }
 
-RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, double number)
+RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, bool b)
 {
-    // FIXME: Our hash tables won't hold infinity, so we make a new JSValue each time.
-    // Later we can do the extra work to handle that like the other cases.  They also don't
-    // work correctly with NaN as a key.
-    if (std::isnan(number) || number == HashTraits<double>::emptyValue() || HashTraits<double>::isDeletedValue(number))
-        return emitLoad(dst, jsNumber(number));
-    JSValue& valueInMap = m_numberMap.add(number, JSValue()).iterator->value;
-    if (!valueInMap)
-        valueInMap = jsNumber(number);
-    return emitLoad(dst, valueInMap);
+    return emitLoad(dst, jsBoolean(b));
 }
 
 RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, const Identifier& identifier)
 {
-    JSString*& stringInMap = m_stringMap.add(identifier.impl(), 0).iterator->value;
+    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)
+RegisterID* BytecodeGenerator::emitLoad(RegisterID* dst, JSValue v, SourceCodeRepresentation sourceCodeRepresentation)
 {
-    RegisterID* constantID = addConstantValue(v);
+    RegisterID* constantID = addConstantValue(v, sourceCodeRepresentation);
     if (dst)
         return emitMove(dst, constantID);
     return constantID;
@@ -1152,83 +1212,103 @@ RegisterID* BytecodeGenerator::emitLoadGlobalObject(RegisterID* dst)
         ++m_nextConstantOffset;
         m_codeBlock->addConstant(JSValue());
         m_globalObjectRegister = &m_constantPoolRegisters[index];
-        m_codeBlock->setGlobalObjectRegister(index);
+        m_codeBlock->setGlobalObjectRegister(VirtualRegister(index));
     }
     if (dst)
         emitMove(dst, m_globalObjectRegister);
     return m_globalObjectRegister;
 }
 
-ResolveResult BytecodeGenerator::resolve(const Identifier& property)
+Variable BytecodeGenerator::variable(const Identifier& property)
 {
-    if (property == propertyNames().thisIdentifier)
-        return ResolveResult::registerResolve(thisRegister(), ResolveResult::ReadOnlyFlag);
-
-    // Check if the property should be allocated in a register.
-    if (m_codeType != GlobalCode && shouldOptimizeLocals() && m_symbolTable) {
-        SymbolTableEntry entry = symbolTable().get(property.impl());
-        if (!entry.isNull()) {
-            if (property == propertyNames().arguments)
-                createArgumentsIfNecessary();
-            unsigned flags = entry.isReadOnly() ? ResolveResult::ReadOnlyFlag : 0;
-            RegisterID* local = createLazyRegisterIfNecessary(&registerFor(entry.getIndex()));
-            return ResolveResult::registerResolve(local, flags);
-        }
+    if (property == propertyNames().thisIdentifier) {
+        return Variable(
+            property, VarOffset(thisRegister()->virtualRegister()), thisRegister(),
+            ReadOnly, Variable::SpecialVariable);
     }
-    // Cases where we cannot statically optimize the lookup.
-    if (property == propertyNames().arguments || !canOptimizeNonLocals())
-        return ResolveResult::dynamicResolve();
-
-    if (!m_scope || m_codeType != FunctionCode || m_shouldEmitDebugHooks)
-        return ResolveResult::dynamicResolve();
-
-    ScopeChainIterator iter = m_scope->begin();
-    ScopeChainIterator end = m_scope->end();
-    size_t depth = m_codeBlock->needsFullScopeChain();
-    unsigned flags = 0;
-    for (; iter != end; ++iter, ++depth) {
-        JSObject* currentScope = iter.get();
-        if (!currentScope->isStaticScopeObject())
-            return ResolveResult::dynamicResolve();
-
-        JSSymbolTableObject* currentVariableObject = jsCast<JSSymbolTableObject*>(currentScope);
-        SymbolTableEntry entry = currentVariableObject->symbolTable()->get(property.impl());
-
-        // Found the property
-        if (!entry.isNull()) {
-            if (entry.isReadOnly())
-                flags |= ResolveResult::ReadOnlyFlag;
-            if (++iter == end)
-                return ResolveResult::dynamicResolve();
-#if !ASSERT_DISABLED
-            if (JSActivation* activation = jsDynamicCast<JSActivation*>(currentVariableObject))
-                ASSERT(activation->isValid(entry));
-#endif
-            return ResolveResult::lexicalResolve(entry.getIndex(), depth, flags);
-        }
-        bool scopeRequiresDynamicChecks = false;
-        if (currentVariableObject->isDynamicScope(scopeRequiresDynamicChecks))
-            break;
-        if (scopeRequiresDynamicChecks)
-            flags |= ResolveResult::DynamicFlag;
+    
+    if (!shouldOptimizeLocals())
+        return Variable(property);
+    
+    SymbolTableEntry entry = symbolTable().get(property.impl());
+    if (entry.isNull())
+        return Variable(property);
+    
+    if (entry.varOffset().isScope() && m_localScopeDepth) {
+        // FIXME: We should be able to statically resolve through our local scopes.
+        // https://bugs.webkit.org/show_bug.cgi?id=141885
+        return Variable(property);
     }
+    
+    return variableForLocalEntry(property, entry);
+}
+
+Variable BytecodeGenerator::variablePerSymbolTable(const Identifier& property)
+{
+    SymbolTableEntry entry = symbolTable().get(property.impl());
+    if (entry.isNull())
+        return Variable(property);
+    
+    return variableForLocalEntry(property, entry);
+}
 
-    return ResolveResult::dynamicResolve();
+Variable BytecodeGenerator::variableForLocalEntry(
+    const Identifier& property, const SymbolTableEntry& entry)
+{
+    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);
 }
 
-ResolveResult BytecodeGenerator::resolveConstDecl(const Identifier& property)
+void BytecodeGenerator::createVariable(
+    const Identifier& property, VarKind varKind, ConstantMode constantMode,
+    ExistingVariableMode existingVariableMode)
 {
-    // Register-allocated const declarations.
-    if (m_codeType == FunctionCode && m_symbolTable) {
-        SymbolTableEntry entry = symbolTable().get(property.impl());
-        if (!entry.isNull()) {
-            unsigned flags = entry.isReadOnly() ? ResolveResult::ReadOnlyFlag : 0;
-            RegisterID* local = createLazyRegisterIfNecessary(&registerFor(entry.getIndex()));
-            return ResolveResult::registerResolve(local, flags);
+    ASSERT(property != propertyNames().thisIdentifier);
+    
+    ConcurrentJITLocker locker(symbolTable().m_lock);
+    SymbolTableEntry entry = symbolTable().get(locker, 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 || constantMode != entry.constantMode()) {
+            dataLog(
+                "Trying to add variable called ", property, " as ", varKind, "/", constantMode,
+                " but it was already added as ", offset, "/", entry.constantMode(), ".\n");
+            RELEASE_ASSERT_NOT_REACHED();
         }
-    }
 
-    return ResolveResult::dynamicResolve();
+        return;
+    }
+    
+    VarOffset varOffset;
+    if (varKind == VarKind::Scope)
+        varOffset = VarOffset(symbolTable().takeNextScopeOffset(locker));
+    else {
+        ASSERT(varKind == VarKind::Stack);
+        varOffset = VarOffset(virtualRegisterForLocal(m_calleeRegisters.size()));
+    }
+    SymbolTableEntry newEntry(varOffset, constantMode == IsConstant ? ReadOnly : 0);
+    symbolTable().add(locker, property.impl(), newEntry);
+    
+    if (varKind == VarKind::Stack) {
+        RegisterID* local = addVar();
+        RELEASE_ASSERT(local->index() == varOffset.stackOffset().offset());
+    }
 }
 
 void BytecodeGenerator::emitCheckHasInstance(RegisterID* dst, RegisterID* value, RegisterID* base, Label* target)
@@ -1241,123 +1321,163 @@ void BytecodeGenerator::emitCheckHasInstance(RegisterID* dst, RegisterID* value,
     instructions().append(target->bind(begin, instructions().size()));
 }
 
-RegisterID* BytecodeGenerator::emitInstanceOf(RegisterID* dst, RegisterID* value, RegisterID* basePrototype)
-{ 
-    emitOpcode(op_instanceof);
-    instructions().append(dst->index());
-    instructions().append(value->index());
-    instructions().append(basePrototype->index());
-    return dst;
-}
-
-bool BytecodeGenerator::shouldAvoidResolveGlobal()
+// 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()
 {
-    return !m_labelScopes.size();
+    if (m_localScopeDepth)
+        return Dynamic;
+    if (m_symbolTable && m_symbolTable->usesNonStrictEval())
+        return GlobalPropertyWithVarInjectionChecks;
+    return GlobalProperty;
 }
 
-RegisterID* BytecodeGenerator::emitResolve(RegisterID* dst, const ResolveResult& resolveResult, const Identifier& property)
+RegisterID* BytecodeGenerator::emitResolveScope(RegisterID* dst, const Variable& variable)
 {
-
-    if (resolveResult.isStatic())
-        return emitGetStaticVar(dst, resolveResult, property);
-
-    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve);
-    instructions().append(kill(dst));
-    instructions().append(addConstant(property));
-    instructions().append(getResolveOperations(property));
-    instructions().append(profile);
-    return dst;
+    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.
+        return m_lexicalEnvironmentRegister;
+        
+    case VarKind::Invalid:
+        // Indicates non-local resolution.
+        
+        ASSERT(!m_symbolTable || !m_symbolTable->contains(variable.ident().impl()) || resolveType() == Dynamic);
+        
+        m_codeBlock->addPropertyAccessInstruction(instructions().size());
+        
+        // resolve_scope dst, id, ResolveType, depth
+        emitOpcode(op_resolve_scope);
+        dst = tempDestination(dst);
+        instructions().append(kill(dst));
+        instructions().append(scopeRegister()->index());
+        instructions().append(addConstant(variable.ident()));
+        instructions().append(resolveType());
+        instructions().append(0);
+        instructions().append(0);
+        return dst;
+    }
+    
+    RELEASE_ASSERT_NOT_REACHED();
+    return nullptr;
 }
 
-RegisterID* BytecodeGenerator::emitResolveBase(RegisterID* dst, const ResolveResult& resolveResult, const Identifier& property)
+RegisterID* BytecodeGenerator::emitGetFromScope(RegisterID* dst, RegisterID* scope, const Variable& variable, ResolveMode resolveMode)
 {
-    if (!resolveResult.isDynamic()) {
-        // Global object is the base
-        return emitLoadGlobalObject(dst);
-    }
-
-    // We can't optimise at all :-(
-    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_base);
-    instructions().append(kill(dst));
-    instructions().append(addConstant(property));
-    instructions().append(false);
-    instructions().append(getResolveBaseOperations(property));
-    instructions().append(0);
-    instructions().append(profile);
-    return dst;
-}
-
-RegisterID* BytecodeGenerator::emitResolveBaseForPut(RegisterID* dst, const ResolveResult&, const Identifier& property, NonlocalResolveInfo& verifier)
-{
-    // We can't optimise at all :-(
-    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_base);
-    instructions().append(kill(dst));
-    instructions().append(addConstant(property));
-    instructions().append(m_codeBlock->isStrictMode());
-    uint32_t putToBaseIndex = 0;
-    instructions().append(getResolveBaseForPutOperations(property, putToBaseIndex));
-    verifier.resolved(putToBaseIndex);
-    instructions().append(putToBaseIndex);
-    instructions().append(profile);
-    return dst;
+    switch (variable.offset().kind()) {
+    case VarKind::Stack:
+        return emitMove(dst, variable.local());
+        
+    case VarKind::DirectArgument: {
+        UnlinkedValueProfile profile = emitProfiledOpcode(op_get_from_arguments);
+        instructions().append(kill(dst));
+        instructions().append(scope->index());
+        instructions().append(variable.offset().capturedArgumentsOffset().offset());
+        instructions().append(profile);
+        return dst;
+    }
+        
+    case VarKind::Scope:
+    case VarKind::Invalid: {
+        m_codeBlock->addPropertyAccessInstruction(instructions().size());
+        
+        // get_from_scope dst, scope, id, ResolveModeAndType, Structure, Operand
+        UnlinkedValueProfile profile = emitProfiledOpcode(op_get_from_scope);
+        instructions().append(kill(dst));
+        instructions().append(scope->index());
+        instructions().append(addConstant(variable.ident()));
+        instructions().append(ResolveModeAndType(resolveMode, variable.offset().isScope() ? LocalClosureVar : resolveType()).operand());
+        instructions().append(0);
+        instructions().append(variable.offset().isScope() ? variable.offset().scopeOffset().offset() : 0);
+        instructions().append(profile);
+        return dst;
+    } }
+    
+    RELEASE_ASSERT_NOT_REACHED();
 }
 
-RegisterID* BytecodeGenerator::emitResolveWithBaseForPut(RegisterID* baseDst, RegisterID* propDst, const ResolveResult& resolveResult, const Identifier& property, NonlocalResolveInfo& verifier)
+RegisterID* BytecodeGenerator::emitPutToScope(RegisterID* scope, const Variable& variable, RegisterID* value, ResolveMode resolveMode)
 {
-    ASSERT_UNUSED(resolveResult, !resolveResult.isStatic());
-    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_with_base);
-    instructions().append(kill(baseDst));
-    instructions().append(propDst->index());
-    instructions().append(addConstant(property));
-    uint32_t putToBaseIndex = 0;
-    instructions().append(getResolveWithBaseForPutOperations(property, putToBaseIndex));
-    verifier.resolved(putToBaseIndex);
-    instructions().append(putToBaseIndex);
-    instructions().append(profile);
-    return baseDst;
+    switch (variable.offset().kind()) {
+    case VarKind::Stack:
+        emitMove(variable.local(), value);
+        return value;
+        
+    case VarKind::DirectArgument:
+        emitOpcode(op_put_to_arguments);
+        instructions().append(scope->index());
+        instructions().append(variable.offset().capturedArgumentsOffset().offset());
+        instructions().append(value->index());
+        return value;
+        
+    case VarKind::Scope:
+    case VarKind::Invalid: {
+        m_codeBlock->addPropertyAccessInstruction(instructions().size());
+        
+        // put_to_scope scope, id, value, ResolveModeAndType, Structure, Operand
+        emitOpcode(op_put_to_scope);
+        instructions().append(scope->index());
+        instructions().append(addConstant(variable.ident()));
+        instructions().append(value->index());
+        ScopeOffset offset;
+        if (variable.offset().isScope()) {
+            offset = variable.offset().scopeOffset();
+            instructions().append(ResolveModeAndType(resolveMode, LocalClosureVar).operand());
+        } else {
+            ASSERT(resolveType() != LocalClosureVar);
+            instructions().append(ResolveModeAndType(resolveMode, resolveType()).operand());
+        }
+        instructions().append(0);
+        instructions().append(!!offset ? offset.offset() : 0);
+        return value;
+    } }
+    
+    RELEASE_ASSERT_NOT_REACHED();
 }
 
-RegisterID* BytecodeGenerator::emitResolveWithThis(RegisterID* baseDst, RegisterID* propDst, const ResolveResult& resolveResult, const Identifier& property)
+RegisterID* BytecodeGenerator::initializeVariable(const Variable& variable, RegisterID* value)
 {
-    if (resolveResult.isStatic()) {
-        emitLoad(baseDst, jsUndefined());
-        emitGetStaticVar(propDst, resolveResult, property);
-        return baseDst;
+    RegisterID* scope;
+    switch (variable.offset().kind()) {
+    case VarKind::Stack:
+        scope = nullptr;
+        break;
+        
+    case VarKind::DirectArgument:
+        scope = argumentsRegister();
+        break;
+        
+    case VarKind::Scope:
+        scope = scopeRegister();
+        break;
+        
+    default:
+        scope = nullptr;
+        RELEASE_ASSERT_NOT_REACHED();
+        break;
     }
 
-    UnlinkedValueProfile profile = emitProfiledOpcode(op_resolve_with_this);
-    instructions().append(kill(baseDst));
-    instructions().append(propDst->index());
-    instructions().append(addConstant(property));
-    instructions().append(getResolveWithThisOperations(property));
-    instructions().append(profile);
-    return baseDst;
+    return emitPutToScope(scope, variable, value, ThrowIfNotFound);
 }
 
-RegisterID* BytecodeGenerator::emitGetStaticVar(RegisterID* dst, const ResolveResult& resolveResult, const Identifier&)
+RegisterID* BytecodeGenerator::emitInstanceOf(RegisterID* dst, RegisterID* value, RegisterID* basePrototype)
 {
-    ASSERT(m_codeType == FunctionCode);
-    switch (resolveResult.type()) {
-    case ResolveResult::Register:
-    case ResolveResult::ReadOnlyRegister:
-        if (dst == ignoredResult())
-            return 0;
-        return moveToDestinationIfNeeded(dst, resolveResult.local());
-
-    case ResolveResult::Lexical:
-    case ResolveResult::ReadOnlyLexical: {
-        UnlinkedValueProfile profile = emitProfiledOpcode(op_get_scoped_var);
-        instructions().append(dst->index());
-        instructions().append(resolveResult.index());
-        instructions().append(resolveResult.depth());
-        instructions().append(profile);
-        return dst;
-    }
-
-    default:
-        RELEASE_ASSERT_NOT_REACHED();
-        return 0;
-    }
+    emitOpcode(op_instanceof);
+    instructions().append(dst->index());
+    instructions().append(value->index());
+    instructions().append(basePrototype->index());
+    return dst;
 }
 
 RegisterID* BytecodeGenerator::emitInitGlobalConst(const Identifier& identifier, RegisterID* value)
@@ -1371,28 +1491,6 @@ RegisterID* BytecodeGenerator::emitInitGlobalConst(const Identifier& identifier,
     return value;
 }
 
-RegisterID* BytecodeGenerator::emitPutStaticVar(const ResolveResult& resolveResult, const Identifier&, RegisterID* value)
-{
-    ASSERT(m_codeType == FunctionCode);
-    switch (resolveResult.type()) {
-    case ResolveResult::Register:
-    case ResolveResult::ReadOnlyRegister:
-        return moveToDestinationIfNeeded(resolveResult.local(), value);
-
-    case ResolveResult::Lexical:
-    case ResolveResult::ReadOnlyLexical:
-        emitOpcode(op_put_scoped_var);
-        instructions().append(resolveResult.index());
-        instructions().append(resolveResult.depth());
-        instructions().append(value->index());
-        return value;
-
-    default:
-        RELEASE_ASSERT_NOT_REACHED();
-        return 0;
-    }
-}
-
 RegisterID* BytecodeGenerator::emitGetById(RegisterID* dst, RegisterID* base, const Identifier& property)
 {
     m_codeBlock->addPropertyAccessInstruction(instructions().size());
@@ -1409,16 +1507,6 @@ RegisterID* BytecodeGenerator::emitGetById(RegisterID* dst, RegisterID* base, co
     return dst;
 }
 
-RegisterID* BytecodeGenerator::emitGetArgumentsLength(RegisterID* dst, RegisterID* base)
-{
-    emitOpcode(op_get_arguments_length);
-    instructions().append(dst->index());
-    ASSERT(base->index() == m_codeBlock->argumentsRegister());
-    instructions().append(base->index());
-    instructions().append(addConstant(propertyNames().length));
-    return dst;
-}
-
 RegisterID* BytecodeGenerator::emitPutById(RegisterID* base, const Identifier& property, RegisterID* value)
 {
     unsigned propertyIndex = addConstant(property);
@@ -1436,21 +1524,13 @@ RegisterID* BytecodeGenerator::emitPutById(RegisterID* base, const Identifier& p
     instructions().append(0);
     instructions().append(0);
     instructions().append(0);
-    return value;
-}
 
-RegisterID* BytecodeGenerator::emitPutToBase(RegisterID* base, const Identifier& property, RegisterID* value, NonlocalResolveInfo& resolveInfo)
-{
-    emitOpcode(op_put_to_base);
-    instructions().append(base->index());
-    instructions().append(addConstant(property));
-    instructions().append(value->index());
-    instructions().append(resolveInfo.put());
     return value;
 }
 
-RegisterID* BytecodeGenerator::emitDirectPutById(RegisterID* base, const Identifier& property, RegisterID* value)
+RegisterID* BytecodeGenerator::emitDirectPutById(RegisterID* base, const Identifier& property, RegisterID* value, PropertyNode::PutType putType)
 {
+    ASSERT(!parseIndex(property));
     unsigned propertyIndex = addConstant(property);
 
     m_staticPropertyAnalyzer.putById(base->index(), propertyIndex);
@@ -1465,12 +1545,32 @@ RegisterID* BytecodeGenerator::emitDirectPutById(RegisterID* base, const Identif
     instructions().append(0);
     instructions().append(0);
     instructions().append(0);
-    instructions().append(
-        property != m_vm->propertyNames->underscoreProto
-        && PropertyName(property).asIndex() == PropertyName::NotAnIndex);
+    instructions().append(putType == PropertyNode::KnownDirect || property != m_vm->propertyNames->underscoreProto);
     return value;
 }
 
+void BytecodeGenerator::emitPutGetterById(RegisterID* base, const Identifier& property, RegisterID* getter)
+{
+    unsigned propertyIndex = addConstant(property);
+    m_staticPropertyAnalyzer.putById(base->index(), propertyIndex);
+
+    emitOpcode(op_put_getter_by_id);
+    instructions().append(base->index());
+    instructions().append(propertyIndex);
+    instructions().append(getter->index());
+}
+
+void BytecodeGenerator::emitPutSetterById(RegisterID* base, const Identifier& property, RegisterID* setter)
+{
+    unsigned propertyIndex = addConstant(property);
+    m_staticPropertyAnalyzer.putById(base->index(), propertyIndex);
+
+    emitOpcode(op_put_setter_by_id);
+    instructions().append(base->index());
+    instructions().append(propertyIndex);
+    instructions().append(setter->index());
+}
+
 void BytecodeGenerator::emitPutGetterSetter(RegisterID* base, const Identifier& property, RegisterID* getter, RegisterID* setter)
 {
     unsigned propertyIndex = addConstant(property);
@@ -1493,34 +1593,33 @@ RegisterID* BytecodeGenerator::emitDeleteById(RegisterID* dst, RegisterID* base,
     return dst;
 }
 
-RegisterID* BytecodeGenerator::emitGetArgumentByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
-{
-    UnlinkedArrayProfile arrayProfile = newArrayProfile();
-    UnlinkedValueProfile profile = emitProfiledOpcode(op_get_argument_by_val);
-    instructions().append(kill(dst));
-    ASSERT(base->index() == m_codeBlock->argumentsRegister());
-    instructions().append(base->index());
-    instructions().append(property->index());
-    instructions().append(arrayProfile);
-    instructions().append(profile);
-    return dst;
-}
-
 RegisterID* BytecodeGenerator::emitGetByVal(RegisterID* dst, RegisterID* base, RegisterID* property)
 {
     for (size_t i = m_forInContextStack.size(); i > 0; i--) {
-        ForInContext& context = m_forInContextStack[i - 1];
-        if (context.propertyRegister == property) {
-            emitOpcode(op_get_by_pname);
-            instructions().append(dst->index());
-            instructions().append(base->index());
-            instructions().append(property->index());
-            instructions().append(context.expectedSubscriptRegister->index());
-            instructions().append(context.iterRegister->index());
-            instructions().append(context.indexRegister->index());
-            return dst;
+        ForInContext* context = m_forInContextStack[i - 1].get();
+        if (context->local() != property)
+            continue;
+
+        if (!context->isValid())
+            break;
+
+        if (context->type() == ForInContext::IndexedForInContextType) {
+            property = static_cast<IndexedForInContext*>(context)->index();
+            break;
         }
+
+        ASSERT(context->type() == ForInContext::StructureForInContextType);
+        StructureForInContext* structureContext = static_cast<StructureForInContext*>(context);
+        UnlinkedValueProfile profile = emitProfiledOpcode(op_get_direct_pname);
+        instructions().append(kill(dst));
+        instructions().append(base->index());
+        instructions().append(property->index());
+        instructions().append(structureContext->index()->index());
+        instructions().append(structureContext->enumerator()->index());
+        instructions().append(profile);
+        return dst;
     }
+
     UnlinkedArrayProfile arrayProfile = newArrayProfile();
     UnlinkedValueProfile profile = emitProfiledOpcode(op_get_by_val);
     instructions().append(kill(dst));
@@ -1539,6 +1638,18 @@ RegisterID* BytecodeGenerator::emitPutByVal(RegisterID* base, RegisterID* proper
     instructions().append(property->index());
     instructions().append(value->index());
     instructions().append(arrayProfile);
+
+    return value;
+}
+
+RegisterID* BytecodeGenerator::emitDirectPutByVal(RegisterID* base, RegisterID* property, RegisterID* value)
+{
+    UnlinkedArrayProfile arrayProfile = newArrayProfile();
+    emitOpcode(op_put_by_val_direct);
+    instructions().append(base->index());
+    instructions().append(property->index());
+    instructions().append(value->index());
+    instructions().append(arrayProfile);
     return value;
 }
 
@@ -1562,22 +1673,24 @@ RegisterID* BytecodeGenerator::emitPutByIndex(RegisterID* base, unsigned index,
 
 RegisterID* BytecodeGenerator::emitCreateThis(RegisterID* dst)
 {
-    RefPtr<RegisterID> func = newTemporary(); 
-
-    UnlinkedValueProfile profile = emitProfiledOpcode(op_get_callee);
-    instructions().append(func->index());
-    instructions().append(profile);
-
     size_t begin = instructions().size();
     m_staticPropertyAnalyzer.createThis(m_thisRegister.index(), begin + 3);
 
+    m_codeBlock->addPropertyAccessInstruction(instructions().size());
     emitOpcode(op_create_this); 
     instructions().append(m_thisRegister.index()); 
-    instructions().append(func->index()); 
+    instructions().append(m_thisRegister.index()); 
+    instructions().append(0);
     instructions().append(0);
     return dst;
 }
 
+void BytecodeGenerator::emitTDZCheck(RegisterID* target)
+{
+    emitOpcode(op_check_tdz);
+    instructions().append(target->index());
+}
+
 RegisterID* BytecodeGenerator::emitNewObject(RegisterID* dst)
 {
     size_t begin = instructions().size();
@@ -1597,7 +1710,7 @@ unsigned BytecodeGenerator::addConstantBuffer(unsigned length)
 
 JSString* BytecodeGenerator::addStringConstant(const Identifier& identifier)
 {
-    JSString*& stringInMap = m_stringMap.add(identifier.impl(), 0).iterator->value;
+    JSString*& stringInMap = m_stringMap.add(identifier.impl(), nullptr).iterator->value;
     if (!stringInMap) {
         stringInMap = jsString(vm(), identifier.string());
         addConstantValue(stringInMap);
@@ -1605,6 +1718,16 @@ JSString* BytecodeGenerator::addStringConstant(const Identifier& identifier)
     return stringInMap;
 }
 
+JSTemplateRegistryKey* BytecodeGenerator::addTemplateRegistryKeyConstant(const TemplateRegistryKey& templateRegistryKey)
+{
+    JSTemplateRegistryKey*& templateRegistryKeyInMap = m_templateRegistryKeyMap.add(templateRegistryKey, nullptr).iterator->value;
+    if (!templateRegistryKeyInMap) {
+        templateRegistryKeyInMap = JSTemplateRegistryKey::create(*vm(), templateRegistryKey);
+        addConstantValue(templateRegistryKeyInMap);
+    }
+    return templateRegistryKeyInMap;
+}
+
 RegisterID* BytecodeGenerator::emitNewArray(RegisterID* dst, ElementNode* elements, unsigned length)
 {
 #if !ASSERT_DISABLED
@@ -1643,13 +1766,16 @@ RegisterID* BytecodeGenerator::emitNewArray(RegisterID* dst, ElementNode* elemen
 
     Vector<RefPtr<RegisterID>, 16, UnsafeVectorOverflow> argv;
     for (ElementNode* n = elements; n; n = n->next()) {
-        if (n->elision())
+        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);
+        ASSERT(argv.size() == 1 || argv[argv.size() - 1]->index() == argv[argv.size() - 2]->index() - 1);
         emitNode(argv.last().get(), n->value());
     }
+    ASSERT(!length);
     emitOpcode(op_new_array);
     instructions().append(dst->index());
     instructions().append(argv.size() ? argv[0]->index() : 0); // argv
@@ -1660,24 +1786,15 @@ RegisterID* BytecodeGenerator::emitNewArray(RegisterID* dst, ElementNode* elemen
 
 RegisterID* BytecodeGenerator::emitNewFunction(RegisterID* dst, FunctionBodyNode* function)
 {
-    return emitNewFunctionInternal(dst, m_codeBlock->addFunctionDecl(makeFunction(function)), false);
-}
-
-RegisterID* BytecodeGenerator::emitLazyNewFunction(RegisterID* dst, FunctionBodyNode* function)
-{
-    FunctionOffsetMap::AddResult ptr = m_functionOffsets.add(function, 0);
-    if (ptr.isNewEntry)
-        ptr.iterator->value = m_codeBlock->addFunctionDecl(makeFunction(function));
-    return emitNewFunctionInternal(dst, ptr.iterator->value, true);
+    return emitNewFunctionInternal(dst, m_codeBlock->addFunctionDecl(makeFunction(function)));
 }
 
-RegisterID* BytecodeGenerator::emitNewFunctionInternal(RegisterID* dst, unsigned index, bool doNullCheck)
+RegisterID* BytecodeGenerator::emitNewFunctionInternal(RegisterID* dst, unsigned index)
 {
-    createActivationIfNecessary();
     emitOpcode(op_new_func);
     instructions().append(dst->index());
+    instructions().append(scopeRegister()->index());
     instructions().append(index);
-    instructions().append(doNullCheck);
     return dst;
 }
 
@@ -1693,57 +1810,42 @@ RegisterID* BytecodeGenerator::emitNewFunctionExpression(RegisterID* r0, FuncExp
 {
     FunctionBodyNode* function = n->body();
     unsigned index = m_codeBlock->addFunctionExpr(makeFunction(function));
-    
-    createActivationIfNecessary();
+
     emitOpcode(op_new_func_exp);
     instructions().append(r0->index());
+    instructions().append(scopeRegister()->index());
     instructions().append(index);
     return r0;
 }
 
-RegisterID* BytecodeGenerator::emitCall(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset, unsigned line, unsigned lineStart)
+RegisterID* BytecodeGenerator::emitNewDefaultConstructor(RegisterID* dst, ConstructorKind constructorKind, const Identifier& name)
 {
-    return emitCall(op_call, dst, func, expectedFunction, callArguments, divot, startOffset, endOffset, line, lineStart);
-}
+    UnlinkedFunctionExecutable* executable = m_vm->builtinExecutables()->createDefaultConstructor(constructorKind, name);
 
-void BytecodeGenerator::createArgumentsIfNecessary()
-{
-    if (m_codeType != FunctionCode)
-        return;
-    
-    if (!m_codeBlock->usesArguments())
-        return;
+    unsigned index = m_codeBlock->addFunctionExpr(executable);
 
-    // If we're in strict mode we tear off the arguments on function
-    // entry, so there's no need to check if we need to create them
-    // now
-    if (m_codeBlock->isStrictMode())
-        return;
-
-    emitOpcode(op_create_arguments);
-    instructions().append(m_codeBlock->argumentsRegister());
+    emitOpcode(op_new_func_exp);
+    instructions().append(dst->index());
+    instructions().append(scopeRegister()->index());
+    instructions().append(index);
+    return dst;
 }
 
-void BytecodeGenerator::createActivationIfNecessary()
+RegisterID* BytecodeGenerator::emitCall(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
 {
-    if (m_hasCreatedActivation)
-        return;
-    if (!m_codeBlock->needsFullScopeChain())
-        return;
-    emitOpcode(op_create_activation);
-    instructions().append(m_activationRegister->index());
+    return emitCall(op_call, dst, func, expectedFunction, callArguments, divot, divotStart, divotEnd);
 }
 
-RegisterID* BytecodeGenerator::emitCallEval(RegisterID* dst, RegisterID* func, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset, unsigned line, unsigned lineStart)
+RegisterID* BytecodeGenerator::emitCallEval(RegisterID* dst, RegisterID* func, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
 {
-    return emitCall(op_call_eval, dst, func, NoExpectedFunction, callArguments, divot, startOffset, endOffset, line, lineStart);
+    return emitCall(op_call_eval, dst, func, NoExpectedFunction, callArguments, divot, divotStart, divotEnd);
 }
 
 ExpectedFunction BytecodeGenerator::expectedFunctionForIdentifier(const Identifier& identifier)
 {
-    if (identifier == m_vm->propertyNames->Object)
+    if (identifier == m_vm->propertyNames->Object || identifier == m_vm->propertyNames->ObjectPrivateName)
         return ExpectObjectConstructor;
-    if (identifier == m_vm->propertyNames->Array)
+    if (identifier == m_vm->propertyNames->Array || identifier == m_vm->propertyNames->ArrayPrivateName)
         return ExpectArrayConstructor;
     return NoExpectedFunction;
 }
@@ -1814,7 +1916,7 @@ ExpectedFunction BytecodeGenerator::emitExpectedFunctionSnippet(RegisterID* dst,
     return expectedFunction;
 }
 
-RegisterID* BytecodeGenerator::emitCall(OpcodeID opcodeID, RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset, unsigned line, unsigned lineStart)
+RegisterID* BytecodeGenerator::emitCall(OpcodeID opcodeID, RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
 {
     ASSERT(opcodeID == op_call || opcodeID == op_call_eval);
     ASSERT(func->refCount());
@@ -1824,9 +1926,20 @@ RegisterID* BytecodeGenerator::emitCall(OpcodeID opcodeID, RegisterID* dst, Regi
 
     // Generate code for arguments.
     unsigned argument = 0;
-    for (ArgumentListNode* n = callArguments.argumentsNode()->m_listNode; n; n = n->m_next)
-        emitNode(callArguments.argumentRegister(argument++), n);
-
+    if (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();
+            RefPtr<RegisterID> argumentRegister;
+            argumentRegister = expression->emitBytecode(*this, callArguments.argumentRegister(0));
+            RefPtr<RegisterID> thisRegister = emitMove(newTemporary(), callArguments.thisRegister());
+            return emitCallVarargs(dst, func, callArguments.thisRegister(), argumentRegister.get(), newTemporary(), 0, callArguments.profileHookRegister(), divot, divotStart, divotEnd);
+        }
+        for (; n; n = n->m_next)
+            emitNode(callArguments.argumentRegister(argument++), n);
+    }
+    
     // Reserve space for call frame.
     Vector<RefPtr<RegisterID>, JSStack::CallFrameHeaderSize, UnsafeVectorOverflow> callFrame;
     for (int i = 0; i < JSStack::CallFrameHeaderSize; ++i)
@@ -1837,28 +1950,24 @@ RegisterID* BytecodeGenerator::emitCall(OpcodeID opcodeID, RegisterID* dst, Regi
         instructions().append(callArguments.profileHookRegister()->index());
     }
 
-    emitExpressionInfo(divot, startOffset, endOffset, line, lineStart);
+    emitExpressionInfo(divot, divotStart, divotEnd);
 
     RefPtr<Label> done = newLabel();
     expectedFunction = emitExpectedFunctionSnippet(dst, func, expectedFunction, callArguments, done.get());
     
     // Emit call.
     UnlinkedArrayProfile arrayProfile = newArrayProfile();
-    emitOpcode(opcodeID);
-    instructions().append(func->index()); // func
-    instructions().append(callArguments.argumentCountIncludingThis()); // argCount
-    instructions().append(callArguments.registerOffset()); // registerOffset
-#if ENABLE(LLINT)
+    UnlinkedValueProfile profile = emitProfiledOpcode(opcodeID);
+    ASSERT(dst);
+    ASSERT(dst != ignoredResult());
+    instructions().append(dst->index());
+    instructions().append(func->index());
+    instructions().append(callArguments.argumentCountIncludingThis());
+    instructions().append(callArguments.stackOffset());
     instructions().append(m_codeBlock->addLLIntCallLinkInfo());
-#else
     instructions().append(0);
-#endif
     instructions().append(arrayProfile);
-    if (dst != ignoredResult()) {
-        UnlinkedValueProfile profile = emitProfiledOpcode(op_call_put_result);
-        instructions().append(kill(dst));
-        instructions().append(profile);
-    }
+    instructions().append(profile);
     
     if (expectedFunction != NoExpectedFunction)
         emitLabel(done.get());
@@ -1871,7 +1980,17 @@ RegisterID* BytecodeGenerator::emitCall(OpcodeID opcodeID, RegisterID* dst, Regi
     return dst;
 }
 
-RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, RegisterID* profileHookRegister, unsigned divot, unsigned startOffset, unsigned endOffset, unsigned line, unsigned lineStart)
+RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, RegisterID* profileHookRegister, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
+{
+    return emitCallVarargs(op_call_varargs, dst, func, thisRegister, arguments, firstFreeRegister, firstVarArgOffset, profileHookRegister, divot, divotStart, divotEnd);
+}
+
+RegisterID* BytecodeGenerator::emitConstructVarargs(RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, RegisterID* profileHookRegister, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
+{
+    return emitCallVarargs(op_construct_varargs, dst, func, thisRegister, arguments, firstFreeRegister, firstVarArgOffset, profileHookRegister, divot, divotStart, divotEnd);
+}
+    
+RegisterID* BytecodeGenerator::emitCallVarargs(OpcodeID opcode, RegisterID* dst, RegisterID* func, RegisterID* thisRegister, RegisterID* arguments, RegisterID* firstFreeRegister, int32_t firstVarArgOffset, RegisterID* profileHookRegister, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
 {
     if (m_shouldEmitProfileHooks) {
         emitMove(profileHookRegister, func);
@@ -1879,19 +1998,20 @@ RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func
         instructions().append(profileHookRegister->index());
     }
     
-    emitExpressionInfo(divot, startOffset, endOffset, line, lineStart);
+    emitExpressionInfo(divot, divotStart, divotEnd);
 
     // Emit call.
-    emitOpcode(op_call_varargs);
+    UnlinkedArrayProfile arrayProfile = newArrayProfile();
+    UnlinkedValueProfile profile = emitProfiledOpcode(opcode);
+    ASSERT(dst != ignoredResult());
+    instructions().append(dst->index());
     instructions().append(func->index());
-    instructions().append(thisRegister->index());
+    instructions().append(thisRegister ? thisRegister->index() : 0);
     instructions().append(arguments->index());
     instructions().append(firstFreeRegister->index());
-    if (dst != ignoredResult()) {
-        UnlinkedValueProfile profile = emitProfiledOpcode(op_call_put_result);
-        instructions().append(kill(dst));
-        instructions().append(profile);
-    }
+    instructions().append(firstVarArgOffset);
+    instructions().append(arrayProfile);
+    instructions().append(profile);
     if (m_shouldEmitProfileHooks) {
         emitOpcode(op_profile_did_call);
         instructions().append(profileHookRegister->index());
@@ -1899,28 +2019,65 @@ RegisterID* BytecodeGenerator::emitCallVarargs(RegisterID* dst, RegisterID* func
     return dst;
 }
 
-RegisterID* BytecodeGenerator::emitReturn(RegisterID* src)
+void BytecodeGenerator::emitCallDefineProperty(RegisterID* newObj, RegisterID* propertyNameRegister,
+    RegisterID* valueRegister, RegisterID* getterRegister, RegisterID* setterRegister, unsigned options, const JSTextPosition& position)
 {
-    if (m_codeBlock->needsFullScopeChain()) {
-        emitOpcode(op_tear_off_activation);
-        instructions().append(m_activationRegister->index());
-    }
+    RefPtr<RegisterID> descriptorRegister = emitNewObject(newTemporary());
 
-    if (m_codeBlock->usesArguments() && m_codeBlock->numParameters() != 1 && !m_codeBlock->isStrictMode()) {
-        emitOpcode(op_tear_off_arguments);
-        instructions().append(m_codeBlock->argumentsRegister());
-        instructions().append(m_activationRegister ? m_activationRegister->index() : emitLoad(0, JSValue())->index());
+    RefPtr<RegisterID> trueRegister = emitLoad(newTemporary(), true);
+    if (options & PropertyConfigurable)
+        emitDirectPutById(descriptorRegister.get(), propertyNames().configurable, trueRegister.get(), PropertyNode::Unknown);
+    if (options & PropertyWritable)
+        emitDirectPutById(descriptorRegister.get(), propertyNames().writable, trueRegister.get(), PropertyNode::Unknown);
+    else if (valueRegister) {
+        RefPtr<RegisterID> falseRegister = emitLoad(newTemporary(), false);
+        emitDirectPutById(descriptorRegister.get(), propertyNames().writable, falseRegister.get(), PropertyNode::Unknown);
     }
+    if (options & PropertyEnumerable)
+        emitDirectPutById(descriptorRegister.get(), propertyNames().enumerable, trueRegister.get(), PropertyNode::Unknown);
+
+    if (valueRegister)
+        emitDirectPutById(descriptorRegister.get(), propertyNames().value, valueRegister, PropertyNode::Unknown);
+    if (getterRegister)
+        emitDirectPutById(descriptorRegister.get(), propertyNames().get, getterRegister, PropertyNode::Unknown);
+    if (setterRegister)
+        emitDirectPutById(descriptorRegister.get(), propertyNames().set, setterRegister, PropertyNode::Unknown);
+
+    RefPtr<RegisterID> definePropertyRegister = emitMoveLinkTimeConstant(newTemporary(), LinkTimeConstant::DefinePropertyFunction);
+
+    CallArguments callArguments(*this, nullptr, 3);
+    emitLoad(callArguments.thisRegister(), jsUndefined());
+    emitMove(callArguments.argumentRegister(0), newObj);
+    emitMove(callArguments.argumentRegister(1), propertyNameRegister);
+    emitMove(callArguments.argumentRegister(2), descriptorRegister.get());
+
+    emitCall(newTemporary(), definePropertyRegister.get(), NoExpectedFunction, callArguments, position, position, position);
+}
+
+RegisterID* BytecodeGenerator::emitReturn(RegisterID* src)
+{
+    if (isConstructor()) {
+        bool derived = constructorKind() == ConstructorKind::Derived;
+        if (derived && src->index() == m_thisRegister.index())
+            emitTDZCheck(src);
+
+        RefPtr<Label> isObjectLabel = newLabel();
+        emitJumpIfTrue(emitIsObject(newTemporary(), src), isObjectLabel.get());
+
+        if (derived) {
+            RefPtr<Label> isUndefinedLabel = newLabel();
+            emitJumpIfTrue(emitIsUndefined(newTemporary(), src), isUndefinedLabel.get());
+            emitThrowTypeError("Cannot return a non-object type in the constructor of a derived class.");
+            emitLabel(isUndefinedLabel.get());
+            if (constructorKind() == ConstructorKind::Derived)
+                emitTDZCheck(&m_thisRegister);
+        }
 
-    // Constructors use op_ret_object_or_this to check the result is an
-    // object, unless we can trivially determine the check is not
-    // necessary (currently, if the return value is 'this').
-    if (isConstructor() && (src->index() != m_thisRegister.index())) {
-        emitOpcode(op_ret_object_or_this);
-        instructions().append(src->index());
-        instructions().append(m_thisRegister.index());
-        return src;
+        emitUnaryNoDstOp(op_ret, &m_thisRegister);
+
+        emitLabel(isObjectLabel.get());
     }
+
     return emitUnaryNoDstOp(op_ret, src);
 }
 
@@ -1931,7 +2088,7 @@ RegisterID* BytecodeGenerator::emitUnaryNoDstOp(OpcodeID opcodeID, RegisterID* s
     return src;
 }
 
-RegisterID* BytecodeGenerator::emitConstruct(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, unsigned divot, unsigned startOffset, unsigned endOffset, unsigned line, unsigned lineStart)
+RegisterID* BytecodeGenerator::emitConstruct(RegisterID* dst, RegisterID* func, ExpectedFunction expectedFunction, CallArguments& callArguments, const JSTextPosition& divot, const JSTextPosition& divotStart, const JSTextPosition& divotEnd)
 {
     ASSERT(func->refCount());
 
@@ -1941,6 +2098,16 @@ RegisterID* BytecodeGenerator::emitConstruct(RegisterID* dst, RegisterID* func,
     // 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();
+            RefPtr<RegisterID> argumentRegister;
+            argumentRegister = expression->emitBytecode(*this, callArguments.argumentRegister(0));
+            return emitConstructVarargs(dst, func, callArguments.thisRegister(), argumentRegister.get(), newTemporary(), 0, callArguments.profileHookRegister(), divot, divotStart, divotEnd);
+        }
+        
         for (ArgumentListNode* n = argumentsNode->m_listNode; n; n = n->m_next)
             emitNode(callArguments.argumentRegister(argument++), n);
     }
@@ -1955,26 +2122,21 @@ RegisterID* BytecodeGenerator::emitConstruct(RegisterID* dst, RegisterID* func,
     for (int i = 0; i < JSStack::CallFrameHeaderSize; ++i)
         callFrame.append(newTemporary());
 
-    emitExpressionInfo(divot, startOffset, endOffset, line, lineStart);
+    emitExpressionInfo(divot, divotStart, divotEnd);
     
     RefPtr<Label> done = newLabel();
     expectedFunction = emitExpectedFunctionSnippet(dst, func, expectedFunction, callArguments, done.get());
 
-    emitOpcode(op_construct);
-    instructions().append(func->index()); // func
-    instructions().append(callArguments.argumentCountIncludingThis()); // argCount
-    instructions().append(callArguments.registerOffset()); // registerOffset
-#if ENABLE(LLINT)
+    UnlinkedValueProfile profile = emitProfiledOpcode(op_construct);
+    ASSERT(dst != ignoredResult());
+    instructions().append(dst->index());
+    instructions().append(func->index());
+    instructions().append(callArguments.argumentCountIncludingThis());
+    instructions().append(callArguments.stackOffset());
     instructions().append(m_codeBlock->addLLIntCallLinkInfo());
-#else
     instructions().append(0);
-#endif
     instructions().append(0);
-    if (dst != ignoredResult()) {
-        UnlinkedValueProfile profile = emitProfiledOpcode(op_call_put_result);
-        instructions().append(kill(dst));
-        instructions().append(profile);
-    }
+    instructions().append(profile);
 
     if (expectedFunction != NoExpectedFunction)
         emitLabel(done.get());
@@ -2004,28 +2166,35 @@ void BytecodeGenerator::emitToPrimitive(RegisterID* dst, RegisterID* src)
     instructions().append(src->index());
 }
 
-RegisterID* BytecodeGenerator::emitPushWithScope(RegisterID* scope)
+void BytecodeGenerator::emitGetScope()
+{
+    emitOpcode(op_get_scope);
+    instructions().append(scopeRegister()->index());
+}
+
+RegisterID* BytecodeGenerator::emitPushWithScope(RegisterID* dst, RegisterID* scope)
 {
     ControlFlowContext context;
     context.isFinallyBlock = false;
     m_scopeContextStack.append(context);
-    m_dynamicScopeDepth++;
+    m_localScopeDepth++;
 
-    return emitUnaryNoDstOp(op_push_with_scope, scope);
+    return emitUnaryOp(op_push_with_scope, dst, scope);
 }
 
-void BytecodeGenerator::emitPopScope()
+void BytecodeGenerator::emitPopScope(RegisterID* srcDst)
 {
     ASSERT(m_scopeContextStack.size());
     ASSERT(!m_scopeContextStack.last().isFinallyBlock);
 
     emitOpcode(op_pop_scope);
+    instructions().append(srcDst->index());
 
     m_scopeContextStack.removeLast();
-    m_dynamicScopeDepth--;
+    m_localScopeDepth--;
 }
 
-void BytecodeGenerator::emitDebugHook(DebugHookID debugHookID, unsigned firstLine, unsigned lastLine, unsigned charOffset, unsigned lineStart)
+void BytecodeGenerator::emitDebugHook(DebugHookID debugHookID, unsigned line, unsigned charOffset, unsigned lineStart)
 {
 #if ENABLE(DEBUG_WITH_BREAKPOINT)
     if (debugHookID != DidReachBreakpoint)
@@ -2034,28 +2203,57 @@ void BytecodeGenerator::emitDebugHook(DebugHookID debugHookID, unsigned firstLin
     if (!m_shouldEmitDebugHooks)
         return;
 #endif
-    emitExpressionInfo(charOffset, 0, 0, firstLine, lineStart);
-    unsigned charPosition = charOffset - m_scopeNode->source().startOffset();
+    JSTextPosition divot(line, charOffset, lineStart);
+    emitExpressionInfo(divot, divot, divot);
     emitOpcode(op_debug);
     instructions().append(debugHookID);
-    instructions().append(firstLine);
-    instructions().append(lastLine);
-    instructions().append(charPosition);
+    instructions().append(false);
 }
 
 void BytecodeGenerator::pushFinallyContext(StatementNode* finallyBlock)
 {
+    // Reclaim free label scopes.
+    while (m_labelScopes.size() && !m_labelScopes.last().refCount())
+        m_labelScopes.removeLast();
+
     ControlFlowContext scope;
     scope.isFinallyBlock = true;
     FinallyContext context = {
         finallyBlock,
+        nullptr,
+        nullptr,
+        static_cast<unsigned>(m_scopeContextStack.size()),
+        static_cast<unsigned>(m_switchContextStack.size()),
+        static_cast<unsigned>(m_forInContextStack.size()),
+        static_cast<unsigned>(m_tryContextStack.size()),
+        static_cast<unsigned>(m_labelScopes.size()),
+        m_finallyDepth,
+        m_localScopeDepth
+    };
+    scope.finallyContext = context;
+    m_scopeContextStack.append(scope);
+    m_finallyDepth++;
+}
+
+void BytecodeGenerator::pushIteratorCloseContext(RegisterID* iterator, ThrowableExpressionData* node)
+{
+    // Reclaim free label scopes.
+    while (m_labelScopes.size() && !m_labelScopes.last().refCount())
+        m_labelScopes.removeLast();
+
+    ControlFlowContext scope;
+    scope.isFinallyBlock = true;
+    FinallyContext context = {
+        nullptr,
+        iterator,
+        node,
         static_cast<unsigned>(m_scopeContextStack.size()),
         static_cast<unsigned>(m_switchContextStack.size()),
         static_cast<unsigned>(m_forInContextStack.size()),
         static_cast<unsigned>(m_tryContextStack.size()),
         static_cast<unsigned>(m_labelScopes.size()),
         m_finallyDepth,
-        m_dynamicScopeDepth
+        m_localScopeDepth
     };
     scope.finallyContext = context;
     m_scopeContextStack.append(scope);
@@ -2066,12 +2264,27 @@ void BytecodeGenerator::popFinallyContext()
 {
     ASSERT(m_scopeContextStack.size());
     ASSERT(m_scopeContextStack.last().isFinallyBlock);
+    ASSERT(m_scopeContextStack.last().finallyContext.finallyBlock);
+    ASSERT(!m_scopeContextStack.last().finallyContext.iterator);
+    ASSERT(!m_scopeContextStack.last().finallyContext.enumerationNode);
+    ASSERT(m_finallyDepth > 0);
+    m_scopeContextStack.removeLast();
+    m_finallyDepth--;
+}
+
+void BytecodeGenerator::popIteratorCloseContext()
+{
+    ASSERT(m_scopeContextStack.size());
+    ASSERT(m_scopeContextStack.last().isFinallyBlock);
+    ASSERT(!m_scopeContextStack.last().finallyContext.finallyBlock);
+    ASSERT(m_scopeContextStack.last().finallyContext.iterator);
+    ASSERT(m_scopeContextStack.last().finallyContext.enumerationNode);
     ASSERT(m_finallyDepth > 0);
     m_scopeContextStack.removeLast();
     m_finallyDepth--;
 }
 
-LabelScope* BytecodeGenerator::breakTarget(const Identifier& name)
+LabelScopePtr BytecodeGenerator::breakTarget(const Identifier& name)
 {
     // Reclaim free label scopes.
     //
@@ -2087,7 +2300,7 @@ LabelScope* BytecodeGenerator::breakTarget(const Identifier& name)
     }
 
     if (!m_labelScopes.size())
-        return 0;
+        return LabelScopePtr::null();
 
     // We special-case the following, which is a syntax error in Firefox:
     // label:
@@ -2097,58 +2310,66 @@ LabelScope* BytecodeGenerator::breakTarget(const Identifier& name)
             LabelScope* scope = &m_labelScopes[i];
             if (scope->type() != LabelScope::NamedLabel) {
                 ASSERT(scope->breakTarget());
-                return scope;
+                return LabelScopePtr(m_labelScopes, i);
             }
         }
-        return 0;
+        return LabelScopePtr::null();
     }
 
     for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
         LabelScope* scope = &m_labelScopes[i];
         if (scope->name() && *scope->name() == name) {
             ASSERT(scope->breakTarget());
-            return scope;
+            return LabelScopePtr(m_labelScopes, i);
         }
     }
-    return 0;
+    return LabelScopePtr::null();
 }
 
-LabelScope* BytecodeGenerator::continueTarget(const Identifier& name)
+LabelScopePtr BytecodeGenerator::continueTarget(const Identifier& name)
 {
     // Reclaim free label scopes.
     while (m_labelScopes.size() && !m_labelScopes.last().refCount())
         m_labelScopes.removeLast();
 
     if (!m_labelScopes.size())
-        return 0;
+        return LabelScopePtr::null();
 
     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 LabelScopePtr(m_labelScopes, i);
             }
         }
-        return 0;
+        return LabelScopePtr::null();
     }
 
     // Continue to the loop nested nearest to the label scope that matches
     // 'name'.
-    LabelScope* result = 0;
+    LabelScopePtr result = LabelScopePtr::null();
     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;
+            result = LabelScopePtr(m_labelScopes, i);
         }
         if (scope->name() && *scope->name() == name)
-            return result; // may be 0
+            return result; // may be null.
     }
-    return 0;
+    return LabelScopePtr::null();
 }
 
-void BytecodeGenerator::emitComplexPopScopes(ControlFlowContext* topScope, ControlFlowContext* bottomScope)
+void BytecodeGenerator::allocateAndEmitScope()
+{
+    m_scopeRegister = addVar();
+    m_scopeRegister->ref();
+    m_codeBlock->setScopeRegister(scopeRegister()->virtualRegister());
+    emitGetScope();
+}
+
+void BytecodeGenerator::emitComplexPopScopes(RegisterID* scope, ControlFlowContext* topScope, ControlFlowContext* bottomScope)
 {
     while (topScope > bottomScope) {
         // First we count the number of dynamic scopes we need to remove to get
@@ -2164,8 +2385,10 @@ void BytecodeGenerator::emitComplexPopScopes(ControlFlowContext* topScope, Contr
         if (nNormalScopes) {
             // We need to remove a number of dynamic scopes to get to the next
             // finally block
-            while (nNormalScopes--)
+            while (nNormalScopes--) {
                 emitOpcode(op_pop_scope);
+                instructions().append(scope->index());
+            }
 
             // If topScope == bottomScope then there isn't a finally block left to emit.
             if (topScope == bottomScope)
@@ -2174,7 +2397,7 @@ void BytecodeGenerator::emitComplexPopScopes(ControlFlowContext* topScope, Contr
         
         Vector<ControlFlowContext> savedScopeContextStack;
         Vector<SwitchInfo> savedSwitchContextStack;
-        Vector<ForInContext> savedForInContextStack;
+        Vector<std::unique_ptr<ForInContext>> savedForInContextStack;
         Vector<TryContext> poppedTryContexts;
         LabelScopeStore savedLabelScopes;
         while (topScope > bottomScope && topScope->isFinallyBlock) {
@@ -2201,7 +2424,7 @@ void BytecodeGenerator::emitComplexPopScopes(ControlFlowContext* topScope, Contr
                 m_switchContextStack.shrink(finallyContext.switchContextStackSize);
             }
             if (flipForIns) {
-                savedForInContextStack = m_forInContextStack;
+                savedForInContextStack.swap(m_forInContextStack);
                 m_forInContextStack.shrink(finallyContext.forInContextStackSize);
             }
             if (flipTries) {
@@ -2224,12 +2447,18 @@ void BytecodeGenerator::emitComplexPopScopes(ControlFlowContext* topScope, Contr
             }
             int savedFinallyDepth = m_finallyDepth;
             m_finallyDepth = finallyContext.finallyDepth;
-            int savedDynamicScopeDepth = m_dynamicScopeDepth;
-            m_dynamicScopeDepth = finallyContext.dynamicScopeDepth;
-            
-            // Emit the finally block.
-            emitNode(finallyContext.finallyBlock);
+            int savedDynamicScopeDepth = m_localScopeDepth;
+            m_localScopeDepth = finallyContext.dynamicScopeDepth;
             
+            if (finallyContext.finallyBlock) {
+                // Emit the finally block.
+                emitNode(finallyContext.finallyBlock);
+            } else {
+                // Emit the IteratorClose block.
+                ASSERT(finallyContext.iterator);
+                emitIteratorClose(finallyContext.iterator, finallyContext.enumerationNode);
+            }
+
             RefPtr<Label> afterFinally = emitLabel(newLabel().get());
             
             // Restore the state of the world.
@@ -2241,7 +2470,7 @@ void BytecodeGenerator::emitComplexPopScopes(ControlFlowContext* topScope, Contr
             if (flipSwitches)
                 m_switchContextStack = savedSwitchContextStack;
             if (flipForIns)
-                m_forInContextStack = savedForInContextStack;
+                m_forInContextStack.swap(savedForInContextStack);
             if (flipTries) {
                 ASSERT(m_tryContextStack.size() == finallyContext.tryContextStackSize);
                 for (unsigned i = poppedTryContexts.size(); i--;) {
@@ -2254,14 +2483,14 @@ void BytecodeGenerator::emitComplexPopScopes(ControlFlowContext* topScope, Contr
             if (flipLabelScopes)
                 m_labelScopes = savedLabelScopes;
             m_finallyDepth = savedFinallyDepth;
-            m_dynamicScopeDepth = savedDynamicScopeDepth;
+            m_localScopeDepth = savedDynamicScopeDepth;
             
             --topScope;
         }
     }
 }
 
-void BytecodeGenerator::emitPopScopes(int targetScopeDepth)
+void BytecodeGenerator::emitPopScopes(RegisterID* scope, int targetScopeDepth)
 {
     ASSERT(scopeDepth() - targetScopeDepth >= 0);
 
@@ -2271,39 +2500,14 @@ void BytecodeGenerator::emitPopScopes(int targetScopeDepth)
         return;
 
     if (!m_finallyDepth) {
-        while (scopeDelta--)
+        while (scopeDelta--) {
             emitOpcode(op_pop_scope);
+            instructions().append(scope->index());
+        }
         return;
     }
 
-    emitComplexPopScopes(&m_scopeContextStack.last(), &m_scopeContextStack.last() - scopeDelta);
-}
-
-RegisterID* BytecodeGenerator::emitGetPropertyNames(RegisterID* dst, RegisterID* base, RegisterID* i, RegisterID* size, Label* breakTarget)
-{
-    size_t begin = instructions().size();
-
-    emitOpcode(op_get_pnames);
-    instructions().append(dst->index());
-    instructions().append(base->index());
-    instructions().append(i->index());
-    instructions().append(size->index());
-    instructions().append(breakTarget->bind(begin, instructions().size()));
-    return dst;
-}
-
-RegisterID* BytecodeGenerator::emitNextPropertyName(RegisterID* dst, RegisterID* base, RegisterID* i, RegisterID* size, RegisterID* iter, Label* target)
-{
-    size_t begin = instructions().size();
-
-    emitOpcode(op_next_pname);
-    instructions().append(dst->index());
-    instructions().append(base->index());
-    instructions().append(i->index());
-    instructions().append(size->index());
-    instructions().append(iter->index());
-    instructions().append(target->bind(begin, instructions().size()));
-    return dst;
+    emitComplexPopScopes(scope, &m_scopeContextStack.last(), &m_scopeContextStack.last() - scopeDelta);
 }
 
 TryData* BytecodeGenerator::pushTry(Label* start)
@@ -2311,6 +2515,7 @@ TryData* BytecodeGenerator::pushTry(Label* start)
     TryData tryData;
     tryData.target = newLabel();
     tryData.targetScopeDepth = UINT_MAX;
+    tryData.handlerType = HandlerType::Illegal;
     m_tryData.append(tryData);
     TryData* result = &m_tryData.last();
     
@@ -2323,7 +2528,7 @@ TryData* BytecodeGenerator::pushTry(Label* start)
     return result;
 }
 
-RegisterID* BytecodeGenerator::popTryAndEmitCatch(TryData* tryData, RegisterID* targetRegister, Label* end)
+void BytecodeGenerator::popTryAndEmitCatch(TryData* tryData, RegisterID* exceptionRegister, RegisterID* thrownValueRegister, Label* end, HandlerType handlerType)
 {
     m_usesExceptions = true;
     
@@ -2337,31 +2542,49 @@ RegisterID* BytecodeGenerator::popTryAndEmitCatch(TryData* tryData, RegisterID*
     m_tryContextStack.removeLast();
     
     emitLabel(tryRange.tryData->target.get());
-    tryRange.tryData->targetScopeDepth = m_dynamicScopeDepth;
+    tryRange.tryData->targetScopeDepth = m_localScopeDepth;
+    tryRange.tryData->handlerType = handlerType;
 
     emitOpcode(op_catch);
-    instructions().append(targetRegister->index());
-    return targetRegister;
+    instructions().append(exceptionRegister->index());
+    instructions().append(thrownValueRegister->index());
 }
 
 void BytecodeGenerator::emitThrowReferenceError(const String& message)
 {
     emitOpcode(op_throw_static_error);
-    instructions().append(addConstantValue(addStringConstant(Identifier(m_vm, message)))->index());
+    instructions().append(addConstantValue(addStringConstant(Identifier::fromString(m_vm, message)))->index());
     instructions().append(true);
 }
 
-void BytecodeGenerator::emitPushNameScope(const Identifier& property, RegisterID* value, unsigned attributes)
+void BytecodeGenerator::emitThrowTypeError(const String& message)
+{
+    emitOpcode(op_throw_static_error);
+    instructions().append(addConstantValue(addStringConstant(Identifier::fromString(m_vm, message)))->index());
+    instructions().append(false);
+}
+
+void BytecodeGenerator::emitPushFunctionNameScope(RegisterID* dst, const Identifier& property, RegisterID* value, unsigned attributes)
+{
+    emitOpcode(op_push_name_scope);
+    instructions().append(dst->index());
+    instructions().append(value->index());
+    instructions().append(addConstantValue(SymbolTable::createNameScopeTable(*vm(), property, attributes))->index());
+    instructions().append(JSNameScope::FunctionNameScope);
+}
+
+void BytecodeGenerator::emitPushCatchScope(RegisterID* dst, const Identifier& property, RegisterID* value, unsigned attributes)
 {
     ControlFlowContext context;
     context.isFinallyBlock = false;
     m_scopeContextStack.append(context);
-    m_dynamicScopeDepth++;
+    m_localScopeDepth++;
 
     emitOpcode(op_push_name_scope);
-    instructions().append(addConstant(property));
+    instructions().append(dst->index());
     instructions().append(value->index());
-    instructions().append(attributes);
+    instructions().append(addConstantValue(SymbolTable::createNameScopeTable(*vm(), property, attributes))->index());
+    instructions().append(JSNameScope::CatchScope);
 }
 
 void BytecodeGenerator::beginSwitch(RegisterID* scrutineeRegister, SwitchInfo::SwitchType type)
@@ -2399,19 +2622,6 @@ static int32_t keyForImmediateSwitch(ExpressionNode* node, int32_t min, int32_t
     return key - min;
 }
 
-static void prepareJumpTableForImmediateSwitch(UnlinkedSimpleJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, int32_t min, int32_t max)
-{
-    jumpTable.min = min;
-    jumpTable.branchOffsets.resize(max - min + 1);
-    jumpTable.branchOffsets.fill(0);
-    for (uint32_t i = 0; i < clauseCount; ++i) {
-        // We're emitting this after the clause labels should have been fixed, so 
-        // the labels should not be "forward" references
-        ASSERT(!labels[i]->isForward());
-        jumpTable.add(keyForImmediateSwitch(nodes[i], min, max), labels[i]->bind(switchAddress, switchAddress + 3)); 
-    }
-}
-
 static int32_t keyForCharacterSwitch(ExpressionNode* node, int32_t min, int32_t max)
 {
     UNUSED_PARAM(max);
@@ -2425,7 +2635,10 @@ static int32_t keyForCharacterSwitch(ExpressionNode* node, int32_t min, int32_t
     return key - min;
 }
 
-static void prepareJumpTableForCharacterSwitch(UnlinkedSimpleJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, int32_t min, int32_t max)
+static void prepareJumpTableForSwitch(
+    UnlinkedSimpleJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount,
+    RefPtr<Label>* labels, ExpressionNode** nodes, int32_t min, int32_t max,
+    int32_t (*keyGetter)(ExpressionNode*, int32_t min, int32_t max))
 {
     jumpTable.min = min;
     jumpTable.branchOffsets.resize(max - min + 1);
@@ -2434,7 +2647,7 @@ static void prepareJumpTableForCharacterSwitch(UnlinkedSimpleJumpTable& jumpTabl
         // We're emitting this after the clause labels should have been fixed, so 
         // the labels should not be "forward" references
         ASSERT(!labels[i]->isForward());
-        jumpTable.add(keyForCharacterSwitch(nodes[i], min, max), labels[i]->bind(switchAddress, switchAddress + 3)); 
+        jumpTable.add(keyGetter(nodes[i], min, max), labels[i]->bind(switchAddress, switchAddress + 3)); 
     }
 }
 
@@ -2455,25 +2668,34 @@ void BytecodeGenerator::endSwitch(uint32_t clauseCount, RefPtr<Label>* labels, E
 {
     SwitchInfo switchInfo = m_switchContextStack.last();
     m_switchContextStack.removeLast();
-    if (switchInfo.switchType == SwitchInfo::SwitchImmediate) {
-        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfImmediateSwitchJumpTables();
+    
+    switch (switchInfo.switchType) {
+    case SwitchInfo::SwitchImmediate:
+    case SwitchInfo::SwitchCharacter: {
+        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfSwitchJumpTables();
         instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->bind(switchInfo.bytecodeOffset, switchInfo.bytecodeOffset + 3);
 
-        UnlinkedSimpleJumpTable& jumpTable = m_codeBlock->addImmediateSwitchJumpTable();
-        prepareJumpTableForImmediateSwitch(jumpTable, switchInfo.bytecodeOffset, clauseCount, labels, nodes, min, max);
-    } else if (switchInfo.switchType == SwitchInfo::SwitchCharacter) {
-        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfCharacterSwitchJumpTables();
-        instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->bind(switchInfo.bytecodeOffset, switchInfo.bytecodeOffset + 3);
+        UnlinkedSimpleJumpTable& jumpTable = m_codeBlock->addSwitchJumpTable();
+        prepareJumpTableForSwitch(
+            jumpTable, switchInfo.bytecodeOffset, clauseCount, labels, nodes, min, max,
+            switchInfo.switchType == SwitchInfo::SwitchImmediate
+                ? keyForImmediateSwitch
+                : keyForCharacterSwitch); 
+        break;
+    }
         
-        UnlinkedSimpleJumpTable& jumpTable = m_codeBlock->addCharacterSwitchJumpTable();
-        prepareJumpTableForCharacterSwitch(jumpTable, switchInfo.bytecodeOffset, clauseCount, labels, nodes, min, max);
-    } else {
-        ASSERT(switchInfo.switchType == SwitchInfo::SwitchString);
+    case SwitchInfo::SwitchString: {
         instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfStringSwitchJumpTables();
         instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->bind(switchInfo.bytecodeOffset, switchInfo.bytecodeOffset + 3);
 
         UnlinkedStringJumpTable& jumpTable = m_codeBlock->addStringSwitchJumpTable();
         prepareJumpTableForStringSwitch(jumpTable, switchInfo.bytecodeOffset, clauseCount, labels, nodes);
+        break;
+    }
+        
+    default:
+        RELEASE_ASSERT_NOT_REACHED();
+        break;
     }
 }
 
@@ -2487,16 +2709,11 @@ RegisterID* BytecodeGenerator::emitThrowExpressionTooDeepException()
     return newTemporary();
 }
 
-void BytecodeGenerator::setIsNumericCompareFunction(bool isNumericCompareFunction)
-{
-    m_codeBlock->setIsNumericCompareFunction(isNumericCompareFunction);
-}
-
 bool BytecodeGenerator::isArgumentNumber(const Identifier& ident, int argumentNumber)
 {
-    RegisterID* registerID = resolve(ident).local();
-    if (!registerID || registerID->index() >= 0)
-         return 0;
+    RegisterID* registerID = variable(ident).local();
+    if (!registerID)
+        return false;
     return registerID->index() == CallFrame::argumentOffset(argumentNumber);
 }
 
@@ -2505,8 +2722,286 @@ void BytecodeGenerator::emitReadOnlyExceptionIfNeeded()
     if (!isStrictMode())
         return;
     emitOpcode(op_throw_static_error);
-    instructions().append(addConstantValue(addStringConstant(Identifier(m_vm, StrictModeReadonlyPropertyWriteError)))->index());
+    instructions().append(addConstantValue(addStringConstant(Identifier::fromString(m_vm, StrictModeReadonlyPropertyWriteError)))->index());
     instructions().append(false);
 }
+    
+void BytecodeGenerator::emitEnumeration(ThrowableExpressionData* node, ExpressionNode* subjectNode, const std::function<void(BytecodeGenerator&, RegisterID*)>& callBack)
+{
+    RefPtr<RegisterID> subject = newTemporary();
+    emitNode(subject.get(), subjectNode);
+    RefPtr<RegisterID> iterator = emitGetById(newTemporary(), subject.get(), propertyNames().iteratorSymbol);
+    {
+        CallArguments args(*this, nullptr);
+        emitMove(args.thisRegister(), subject.get());
+        emitCall(iterator.get(), iterator.get(), NoExpectedFunction, args, node->divot(), node->divotStart(), node->divotEnd());
+    }
+
+    RefPtr<Label> loopDone = newLabel();
+    // RefPtr<Register> iterator's lifetime must be longer than IteratorCloseContext.
+    pushIteratorCloseContext(iterator.get(), node);
+    {
+        LabelScopePtr scope = newLabelScope(LabelScope::Loop);
+        RefPtr<RegisterID> value = newTemporary();
+        emitLoad(value.get(), jsUndefined());
+
+        emitJump(scope->continueTarget());
+
+        RefPtr<Label> loopStart = newLabel();
+        emitLabel(loopStart.get());
+        emitLoopHint();
+
+        RefPtr<Label> tryStartLabel = newLabel();
+        emitLabel(tryStartLabel.get());
+        TryData* tryData = pushTry(tryStartLabel.get());
+        callBack(*this, value.get());
+        emitJump(scope->continueTarget());
+
+        // IteratorClose sequence for throw-ed control flow.
+        {
+            RefPtr<Label> catchHere = emitLabel(newLabel().get());
+            RefPtr<RegisterID> exceptionRegister = newTemporary();
+            RefPtr<RegisterID> thrownValueRegister = newTemporary();
+            popTryAndEmitCatch(tryData, exceptionRegister.get(),
+                thrownValueRegister.get(), catchHere.get(), HandlerType::SynthesizedFinally);
+
+            RefPtr<Label> catchDone = newLabel();
+
+            RefPtr<RegisterID> returnMethod = emitGetById(newTemporary(), iterator.get(), propertyNames().returnKeyword);
+            emitJumpIfTrue(emitIsUndefined(newTemporary(), returnMethod.get()), catchDone.get());
+
+            RefPtr<Label> returnCallTryStart = newLabel();
+            emitLabel(returnCallTryStart.get());
+            TryData* returnCallTryData = pushTry(returnCallTryStart.get());
+
+            CallArguments returnArguments(*this, nullptr);
+            emitMove(returnArguments.thisRegister(), iterator.get());
+            emitCall(value.get(), returnMethod.get(), NoExpectedFunction, returnArguments, node->divot(), node->divotStart(), node->divotEnd());
+
+            emitLabel(catchDone.get());
+            emitThrow(exceptionRegister.get());
+
+            // Absorb exception.
+            popTryAndEmitCatch(returnCallTryData, newTemporary(),
+                newTemporary(), catchDone.get(), HandlerType::SynthesizedFinally);
+            emitThrow(exceptionRegister.get());
+        }
+
+        emitLabel(scope->continueTarget());
+        {
+            emitIteratorNext(value.get(), iterator.get(), node);
+            emitJumpIfTrue(emitGetById(newTemporary(), value.get(), propertyNames().done), loopDone.get());
+            emitGetById(value.get(), value.get(), propertyNames().value);
+            emitJump(loopStart.get());
+        }
+
+        emitLabel(scope->breakTarget());
+    }
+
+    // IteratorClose sequence for break-ed control flow.
+    popIteratorCloseContext();
+    emitIteratorClose(iterator.get(), node);
+    emitLabel(loopDone.get());
+}
+
+#if ENABLE(ES6_TEMPLATE_LITERAL_SYNTAX)
+RegisterID* BytecodeGenerator::emitGetTemplateObject(RegisterID* dst, TaggedTemplateNode* taggedTemplate)
+{
+    TemplateRegistryKey::StringVector rawStrings;
+    TemplateRegistryKey::StringVector cookedStrings;
+
+    TemplateStringListNode* templateString = taggedTemplate->templateLiteral()->templateStrings();
+    for (; templateString; templateString = templateString->next()) {
+        rawStrings.append(templateString->value()->raw().impl());
+        cookedStrings.append(templateString->value()->cooked().impl());
+    }
+
+    RefPtr<RegisterID> getTemplateObject = nullptr;
+    Variable var = variable(propertyNames().getTemplateObjectPrivateName);
+    if (RegisterID* local = var.local())
+        getTemplateObject = emitMove(newTemporary(), local);
+    else {
+        getTemplateObject = newTemporary();
+        RefPtr<RegisterID> scope = newTemporary();
+        moveToDestinationIfNeeded(scope.get(), emitResolveScope(scope.get(), var));
+        emitGetFromScope(getTemplateObject.get(), scope.get(), var, ThrowIfNotFound);
+    }
+
+    CallArguments arguments(*this, nullptr);
+    emitLoad(arguments.thisRegister(), JSValue(addTemplateRegistryKeyConstant(TemplateRegistryKey(rawStrings, cookedStrings))));
+    return emitCall(dst, getTemplateObject.get(), NoExpectedFunction, arguments, taggedTemplate->divot(), taggedTemplate->divotStart(), taggedTemplate->divotEnd());
+}
+#endif
+
+RegisterID* BytecodeGenerator::emitGetEnumerableLength(RegisterID* dst, RegisterID* base)
+{
+    emitOpcode(op_get_enumerable_length);
+    instructions().append(dst->index());
+    instructions().append(base->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitHasGenericProperty(RegisterID* dst, RegisterID* base, RegisterID* propertyName)
+{
+    emitOpcode(op_has_generic_property);
+    instructions().append(dst->index());
+    instructions().append(base->index());
+    instructions().append(propertyName->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitHasIndexedProperty(RegisterID* dst, RegisterID* base, RegisterID* propertyName)
+{
+    UnlinkedArrayProfile arrayProfile = newArrayProfile();
+    emitOpcode(op_has_indexed_property);
+    instructions().append(dst->index());
+    instructions().append(base->index());
+    instructions().append(propertyName->index());
+    instructions().append(arrayProfile);
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitHasStructureProperty(RegisterID* dst, RegisterID* base, RegisterID* propertyName, RegisterID* enumerator)
+{
+    emitOpcode(op_has_structure_property);
+    instructions().append(dst->index());
+    instructions().append(base->index());
+    instructions().append(propertyName->index());
+    instructions().append(enumerator->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitGetPropertyEnumerator(RegisterID* dst, RegisterID* base)
+{
+    emitOpcode(op_get_property_enumerator);
+    instructions().append(dst->index());
+    instructions().append(base->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitEnumeratorStructurePropertyName(RegisterID* dst, RegisterID* enumerator, RegisterID* index)
+{
+    emitOpcode(op_enumerator_structure_pname);
+    instructions().append(dst->index());
+    instructions().append(enumerator->index());
+    instructions().append(index->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitEnumeratorGenericPropertyName(RegisterID* dst, RegisterID* enumerator, RegisterID* index)
+{
+    emitOpcode(op_enumerator_generic_pname);
+    instructions().append(dst->index());
+    instructions().append(enumerator->index());
+    instructions().append(index->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitToIndexString(RegisterID* dst, RegisterID* index)
+{
+    emitOpcode(op_to_index_string);
+    instructions().append(dst->index());
+    instructions().append(index->index());
+    return dst;
+}
+
+
+RegisterID* BytecodeGenerator::emitIsObject(RegisterID* dst, RegisterID* src)
+{
+    emitOpcode(op_is_object);
+    instructions().append(dst->index());
+    instructions().append(src->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitIsUndefined(RegisterID* dst, RegisterID* src)
+{
+    emitOpcode(op_is_undefined);
+    instructions().append(dst->index());
+    instructions().append(src->index());
+    return dst;
+}
+
+RegisterID* BytecodeGenerator::emitIteratorNext(RegisterID* dst, RegisterID* iterator, const ThrowableExpressionData* node)
+{
+    {
+        RefPtr<RegisterID> next = emitGetById(newTemporary(), iterator, propertyNames().next);
+        CallArguments nextArguments(*this, nullptr);
+        emitMove(nextArguments.thisRegister(), iterator);
+        emitCall(dst, next.get(), NoExpectedFunction, nextArguments, node->divot(), node->divotStart(), node->divotEnd());
+    }
+    {
+        RefPtr<Label> typeIsObject = newLabel();
+        emitJumpIfTrue(emitIsObject(newTemporary(), dst), typeIsObject.get());
+        emitThrowTypeError(ASCIILiteral("Iterator result interface is not an object."));
+        emitLabel(typeIsObject.get());
+    }
+    return dst;
+}
+
+void BytecodeGenerator::emitIteratorClose(RegisterID* iterator, const ThrowableExpressionData* node)
+{
+    RefPtr<Label> done = newLabel();
+    RefPtr<RegisterID> returnMethod = emitGetById(newTemporary(), iterator, propertyNames().returnKeyword);
+    emitJumpIfTrue(emitIsUndefined(newTemporary(), returnMethod.get()), done.get());
+
+    RefPtr<RegisterID> value = newTemporary();
+    CallArguments returnArguments(*this, nullptr);
+    emitMove(returnArguments.thisRegister(), iterator);
+    emitCall(value.get(), returnMethod.get(), NoExpectedFunction, returnArguments, node->divot(), node->divotStart(), node->divotEnd());
+    emitJumpIfTrue(emitIsObject(newTemporary(), value.get()), done.get());
+    emitThrowTypeError(ASCIILiteral("Iterator result interface is not an object."));
+    emitLabel(done.get());
+}
+
+void BytecodeGenerator::pushIndexedForInScope(RegisterID* localRegister, RegisterID* indexRegister)
+{
+    if (!localRegister)
+        return;
+    m_forInContextStack.append(std::make_unique<IndexedForInContext>(localRegister, indexRegister));
+}
+
+void BytecodeGenerator::popIndexedForInScope(RegisterID* localRegister)
+{
+    if (!localRegister)
+        return;
+    m_forInContextStack.removeLast();
+}
+
+void BytecodeGenerator::pushStructureForInScope(RegisterID* localRegister, RegisterID* indexRegister, RegisterID* propertyRegister, RegisterID* enumeratorRegister)
+{
+    if (!localRegister)
+        return;
+    m_forInContextStack.append(std::make_unique<StructureForInContext>(localRegister, indexRegister, propertyRegister, enumeratorRegister));
+}
+
+void BytecodeGenerator::popStructureForInScope(RegisterID* localRegister)
+{
+    if (!localRegister)
+        return;
+    m_forInContextStack.removeLast();
+}
+
+void BytecodeGenerator::invalidateForInContextForLocal(RegisterID* localRegister)
+{
+    // 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.
+    for (size_t i = m_forInContextStack.size(); i > 0; i--) {
+        ForInContext* context = m_forInContextStack[i - 1].get();
+        if (context->local() != localRegister)
+            continue;
+        context->invalidate();
+        break;
+    }
+}
 
 } // namespace JSC