Merge 'wip/next' into dev

Change-Id: Iff9ee5e23bb326c4371ec8ed81d56f2f05d680e9

19 files changed, 2205 insertions, 2174 deletions

diff --git a/Source/JavaScriptCore/interpreter/AbstractPC.cpp b/Source/JavaScriptCore/interpreter/AbstractPC.cpp
index 8600b7228..09b24d5dc 100644
--- a/Source/JavaScriptCore/interpreter/AbstractPC.cpp
+++ b/Source/JavaScriptCore/interpreter/AbstractPC.cpp
@@ -27,9 +27,9 @@
 #include "AbstractPC.h"
 
 #include "CallFrame.h"
-#include "VM.h"
 #include "JSObject.h"
-
+#include "JSCInlines.h"
+#include "VM.h"
 
 namespace JSC {
 
diff --git a/Source/JavaScriptCore/interpreter/AbstractPC.h b/Source/JavaScriptCore/interpreter/AbstractPC.h
index c30027d9e..ac2aaa7ad 100644
--- a/Source/JavaScriptCore/interpreter/AbstractPC.h
+++ b/Source/JavaScriptCore/interpreter/AbstractPC.h
@@ -27,7 +27,6 @@
 #define AbstractPC_h
 
 #include "MacroAssemblerCodeRef.h"
-#include <wtf/Platform.h>
 
 namespace JSC {
 
diff --git a/Source/JavaScriptCore/interpreter/CachedCall.h b/Source/JavaScriptCore/interpreter/CachedCall.h
index ddf9a40ad..30cad2a14 100644
--- a/Source/JavaScriptCore/interpreter/CachedCall.h
+++ b/Source/JavaScriptCore/interpreter/CachedCall.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2009 Apple Inc. All rights reserved.
+ * Copyright (C) 2009, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -27,9 +27,12 @@
 #define CachedCall_h
 
 #include "CallFrameClosure.h"
+#include "ExceptionHelpers.h"
 #include "JSFunction.h"
 #include "JSGlobalObject.h"
 #include "Interpreter.h"
+#include "ProtoCallFrame.h"
+#include "VMEntryScope.h"
 
 namespace JSC {
     class CachedCall {
@@ -38,10 +41,14 @@ namespace JSC {
         CachedCall(CallFrame* callFrame, JSFunction* function, int argumentCount)
             : m_valid(false)
             , m_interpreter(callFrame->interpreter())
-            , m_globalObjectScope(callFrame->vm(), function->scope()->globalObject())
+            , m_entryScope(callFrame->vm(), function->scope()->globalObject())
         {
-            ASSERT(!function->isHostFunction());
-            m_closure = m_interpreter->prepareForRepeatCall(function->jsExecutable(), callFrame, function, argumentCount + 1, function->scope());
+            ASSERT(!function->isHostFunctionNonInline());
+            if (callFrame->vm().isSafeToRecurse()) {
+                m_arguments.resize(argumentCount);
+                m_closure = m_interpreter->prepareForRepeatCall(function->jsExecutable(), callFrame, &m_protoCallFrame, function, argumentCount + 1, function->scope(), m_arguments.data());
+            } else
+                throwStackOverflowError(callFrame);
             m_valid = !callFrame->hadException();
         }
         
@@ -50,26 +57,15 @@ namespace JSC {
             ASSERT(m_valid);
             return m_interpreter->execute(m_closure);
         }
-        void setThis(JSValue v) { m_closure.setThis(v); }
-        void setArgument(int n, JSValue v) { m_closure.setArgument(n, v); }
+        void setThis(JSValue v) { m_protoCallFrame.setThisValue(v); }
+        void setArgument(int n, JSValue v) { m_protoCallFrame.setArgument(n, v); }
 
-        CallFrame* newCallFrame(ExecState* exec)
-        {
-            CallFrame* callFrame = m_closure.newCallFrame;
-            callFrame->setScope(exec->scope());
-            return callFrame;
-        }
-
-        ~CachedCall()
-        {
-            if (m_valid)
-                m_interpreter->endRepeatCall(m_closure);
-        }
-        
     private:
         bool m_valid;
         Interpreter* m_interpreter;
-        DynamicGlobalObjectScope m_globalObjectScope;
+        VMEntryScope m_entryScope;
+        ProtoCallFrame m_protoCallFrame;
+        Vector<JSValue> m_arguments;
         CallFrameClosure m_closure;
     };
 }
diff --git a/Source/JavaScriptCore/interpreter/CallFrame.cpp b/Source/JavaScriptCore/interpreter/CallFrame.cpp
index bb61020ce..3d3897b6b 100644
--- a/Source/JavaScriptCore/interpreter/CallFrame.cpp
+++ b/Source/JavaScriptCore/interpreter/CallFrame.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008, 2013 Apple Inc. All Rights Reserved.
+ * Copyright (C) 2008, 2013, 2014 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -27,23 +27,74 @@
 #include "CallFrame.h"
 
 #include "CodeBlock.h"
+#include "InlineCallFrame.h"
 #include "Interpreter.h"
-#include "Operations.h"
+#include "JSLexicalEnvironment.h"
+#include "JSCInlines.h"
+#include "VMEntryScope.h"
+#include <wtf/StringPrintStream.h>
 
 namespace JSC {
 
-#ifndef NDEBUG
-void CallFrame::dumpCaller()
+bool CallFrame::callSiteBitsAreBytecodeOffset() const
 {
-    int signedLineNumber;
-    intptr_t sourceID;
-    String urlString;
-    JSValue function;
-    
-    interpreter()->retrieveLastCaller(this, signedLineNumber, sourceID, urlString, function);
-    dataLogF("Callpoint => %s:%d\n", urlString.utf8().data(), signedLineNumber);
+    ASSERT(codeBlock());
+    switch (codeBlock()->jitType()) {
+    case JITCode::InterpreterThunk:
+    case JITCode::BaselineJIT:
+        return true;
+    case JITCode::None:
+    case JITCode::HostCallThunk:
+        RELEASE_ASSERT_NOT_REACHED();
+        return false;
+    default:
+        return false;
+    }
+
+    RELEASE_ASSERT_NOT_REACHED();
+    return false;
+}
+
+bool CallFrame::callSiteBitsAreCodeOriginIndex() const
+{
+    ASSERT(codeBlock());
+    switch (codeBlock()->jitType()) {
+    case JITCode::DFGJIT:
+    case JITCode::FTLJIT:
+        return true;
+    case JITCode::None:
+    case JITCode::HostCallThunk:
+        RELEASE_ASSERT_NOT_REACHED();
+        return false;
+    default:
+        return false;
+    }
+
+    RELEASE_ASSERT_NOT_REACHED();
+    return false;
+}
+
+unsigned CallFrame::callSiteAsRawBits() const
+{
+    return this[JSStack::ArgumentCount].tag();
+}
+
+SUPPRESS_ASAN unsigned CallFrame::unsafeCallSiteAsRawBits() const
+{
+    return this[JSStack::ArgumentCount].unsafeTag();
+}
+
+CallSiteIndex CallFrame::callSiteIndex() const
+{
+    return CallSiteIndex(callSiteAsRawBits());
+}
+
+SUPPRESS_ASAN CallSiteIndex CallFrame::unsafeCallSiteIndex() const
+{
+    return CallSiteIndex(unsafeCallSiteAsRawBits());
 }
 
+#ifndef NDEBUG
 JSStack* CallFrame::stack()
 {
     return &interpreter()->stack();
@@ -52,170 +103,175 @@ JSStack* CallFrame::stack()
 #endif
 
 #if USE(JSVALUE32_64)
-unsigned CallFrame::bytecodeOffsetForNonDFGCode() const
+Instruction* CallFrame::currentVPC() const
 {
-    ASSERT(codeBlock());
-    return currentVPC() - codeBlock()->instructions().begin();
+    return bitwise_cast<Instruction*>(callSiteIndex().bits());
 }
 
-void CallFrame::setBytecodeOffsetForNonDFGCode(unsigned offset)
+void CallFrame::setCurrentVPC(Instruction* vpc)
+{
+    CallSiteIndex callSite(vpc);
+    this[JSStack::ArgumentCount].tag() = callSite.bits();
+}
+
+unsigned CallFrame::callSiteBitsAsBytecodeOffset() const
 {
     ASSERT(codeBlock());
-    setCurrentVPC(codeBlock()->instructions().begin() + offset);
+    ASSERT(callSiteBitsAreBytecodeOffset());
+    return currentVPC() - codeBlock()->instructions().begin();     
 }
-#else
+
+#else // USE(JSVALUE32_64)
 Instruction* CallFrame::currentVPC() const
 {
-    return codeBlock()->instructions().begin() + bytecodeOffsetForNonDFGCode();
+    ASSERT(callSiteBitsAreBytecodeOffset());
+    return codeBlock()->instructions().begin() + callSiteBitsAsBytecodeOffset();
 }
+
 void CallFrame::setCurrentVPC(Instruction* vpc)
 {
-    setBytecodeOffsetForNonDFGCode(vpc - codeBlock()->instructions().begin());
+    CallSiteIndex callSite(vpc - codeBlock()->instructions().begin());
+    this[JSStack::ArgumentCount].tag() = static_cast<int32_t>(callSite.bits());
 }
-#endif
-    
-#if ENABLE(DFG_JIT)
-bool CallFrame::isInlineCallFrameSlow()
+
+unsigned CallFrame::callSiteBitsAsBytecodeOffset() const
 {
-    if (!callee())
-        return false;
-    JSCell* calleeAsFunctionCell = getJSFunction(callee());
-    if (!calleeAsFunctionCell)
-        return false;
-    JSFunction* calleeAsFunction = jsCast<JSFunction*>(calleeAsFunctionCell);
-    return calleeAsFunction->executable() != codeBlock()->ownerExecutable();
+    ASSERT(codeBlock());
+    ASSERT(callSiteBitsAreBytecodeOffset());
+    return callSiteIndex().bits();
 }
 
-CallFrame* CallFrame::trueCallFrame(AbstractPC pc)
-{
-    // Am I an inline call frame? If so, we're done.
-    if (isInlineCallFrame())
-        return this;
-    
-    // If I don't have a code block, then I'm not DFG code, so I'm the true call frame.
-    CodeBlock* machineCodeBlock = codeBlock();
-    if (!machineCodeBlock)
-        return this;
-    
-    // If the code block does not have any code origins, then there was no inlining, so
-    // I'm done.
-    if (!machineCodeBlock->hasCodeOrigins())
-        return this;
-    
-    // At this point the PC must be due either to the DFG, or it must be unset.
-    ASSERT(pc.hasJITReturnAddress() || !pc);
+#endif
     
-    // Try to determine the CodeOrigin. If we don't have a pc set then the only way
-    // that this makes sense is if the CodeOrigin index was set in the call frame.
-    // FIXME: Note that you will see "Not currently in inlined code" comments below.
-    // Currently, we do not record code origins for code that is not inlined, because
-    // the only thing that we use code origins for is determining the inline stack.
-    // But in the future, we'll want to use this same functionality (having a code
-    // origin mapping for any calls out of JIT code) to determine the PC at any point
-    // in the stack even if not in inlined code. When that happens, the code below
-    // will have to change the way it detects the presence of inlining: it will always
-    // get a code origin, but sometimes, that code origin will not have an inline call
-    // frame. In that case, this method should bail and return this.
-    CodeOrigin codeOrigin;
-    if (pc.isSet()) {
-        ReturnAddressPtr currentReturnPC = pc.jitReturnAddress();
-        
-        bool hasCodeOrigin = machineCodeBlock->codeOriginForReturn(currentReturnPC, codeOrigin);
-        ASSERT(hasCodeOrigin);
-        if (!hasCodeOrigin) {
-            // In release builds, if we find ourselves in a situation where the return PC doesn't
-            // correspond to a valid CodeOrigin, we return zero instead of continuing. Some of
-            // the callers of trueCallFrame() will be able to recover and do conservative things,
-            // while others will crash.
-            return 0;
-        }
-    } else {
-        unsigned index = codeOriginIndexForDFG();
-        ASSERT(machineCodeBlock->canGetCodeOrigin(index));
-        if (!machineCodeBlock->canGetCodeOrigin(index)) {
-            // See above. In release builds, we try to protect ourselves from crashing even
-            // though stack walking will be goofed up.
-            return 0;
+unsigned CallFrame::bytecodeOffset()
+{
+    if (!codeBlock())
+        return 0;
+#if ENABLE(DFG_JIT)
+    if (callSiteBitsAreCodeOriginIndex()) {
+        ASSERT(codeBlock());
+        CodeOrigin codeOrigin = this->codeOrigin();
+        for (InlineCallFrame* inlineCallFrame = codeOrigin.inlineCallFrame; inlineCallFrame;) {
+            codeOrigin = inlineCallFrame->directCaller;
+            inlineCallFrame = codeOrigin.inlineCallFrame;
         }
-        codeOrigin = machineCodeBlock->codeOrigin(index);
+        return codeOrigin.bytecodeIndex;
     }
+#endif
+    ASSERT(callSiteBitsAreBytecodeOffset());
+    return callSiteBitsAsBytecodeOffset();
+}
 
-    if (!codeOrigin.inlineCallFrame)
-        return this; // Not currently in inlined code.
-    
-    for (InlineCallFrame* inlineCallFrame = codeOrigin.inlineCallFrame; inlineCallFrame;) {
-        InlineCallFrame* nextInlineCallFrame = inlineCallFrame->caller.inlineCallFrame;
-        
-        CallFrame* inlinedCaller = this + inlineCallFrame->stackOffset;
-        
-        JSFunction* calleeAsFunction = inlineCallFrame->callee.get();
-        
-        // Fill in the inlinedCaller
-        inlinedCaller->setCodeBlock(machineCodeBlock);
-        if (calleeAsFunction)
-            inlinedCaller->setScope(calleeAsFunction->scope());
-        if (nextInlineCallFrame)
-            inlinedCaller->setCallerFrame(this + nextInlineCallFrame->stackOffset);
-        else
-            inlinedCaller->setCallerFrame(this);
-        
-        inlinedCaller->setInlineCallFrame(inlineCallFrame);
-        inlinedCaller->setArgumentCountIncludingThis(inlineCallFrame->arguments.size());
-        if (calleeAsFunction)
-            inlinedCaller->setCallee(calleeAsFunction);
-        
-        inlineCallFrame = nextInlineCallFrame;
+CodeOrigin CallFrame::codeOrigin()
+{
+    if (!codeBlock())
+        return CodeOrigin(0);
+#if ENABLE(DFG_JIT)
+    if (callSiteBitsAreCodeOriginIndex()) {
+        CallSiteIndex index = callSiteIndex();
+        ASSERT(codeBlock()->canGetCodeOrigin(index));
+        return codeBlock()->codeOrigin(index);
     }
-    
-    return this + codeOrigin.inlineCallFrame->stackOffset;
+#endif
+    return CodeOrigin(callSiteBitsAsBytecodeOffset());
 }
-        
-CallFrame* CallFrame::trueCallerFrame()
+
+Register* CallFrame::topOfFrameInternal()
 {
-    if (!codeBlock())
-        return callerFrame()->removeHostCallFrameFlag();
-
-    // this -> The callee; this is either an inlined callee in which case it already has
-    //    a pointer to the true caller. Otherwise it contains current PC in the machine
-    //    caller.
-    //
-    // machineCaller -> The caller according to the machine, which may be zero or
-    //    more frames above the true caller due to inlining.
-
-    // Am I an inline call frame? If so, we're done.
-    if (isInlineCallFrame())
-        return callerFrame()->removeHostCallFrameFlag();
-    
-    // I am a machine call frame, so the question is: is my caller a machine call frame
-    // that has inlines or a machine call frame that doesn't?
-    CallFrame* machineCaller = callerFrame()->removeHostCallFrameFlag();
-    if (!machineCaller)
-        return 0;
-    ASSERT(!machineCaller->isInlineCallFrame());
-    
-    // Figure out how we want to get the current code location.
-    if (!hasReturnPC() || returnAddressIsInCtiTrampoline(returnPC()))
-        return machineCaller->trueCallFrameFromVMCode()->removeHostCallFrameFlag();
-    
-    return machineCaller->trueCallFrame(returnPC())->removeHostCallFrameFlag();
+    CodeBlock* codeBlock = this->codeBlock();
+    ASSERT(codeBlock);
+    return registers() + codeBlock->stackPointerOffset();
 }
 
-CodeBlock* CallFrame::someCodeBlockForPossiblyInlinedCode()
+JSGlobalObject* CallFrame::vmEntryGlobalObject()
 {
-    if (!isInlineCallFrame())
-        return codeBlock();
-    
-    return jsCast<FunctionExecutable*>(inlineCallFrame()->executable.get())->baselineCodeBlockFor(
-        inlineCallFrame()->isCall ? CodeForCall : CodeForConstruct);
+    if (this == lexicalGlobalObject()->globalExec())
+        return lexicalGlobalObject();
+
+    // For any ExecState that's not a globalExec, the 
+    // dynamic global object must be set since code is running
+    ASSERT(vm().entryScope);
+    return vm().entryScope->globalObject();
 }
 
-#endif
+CallFrame* CallFrame::callerFrame(VMEntryFrame*& currVMEntryFrame)
+{
+    if (callerFrameOrVMEntryFrame() == currVMEntryFrame) {
+        VMEntryRecord* currVMEntryRecord = vmEntryRecord(currVMEntryFrame);
+        currVMEntryFrame = currVMEntryRecord->prevTopVMEntryFrame();
+        return currVMEntryRecord->prevTopCallFrame();
+    }
+    return static_cast<CallFrame*>(callerFrameOrVMEntryFrame());
+}
 
-Register* CallFrame::frameExtentInternal()
+SUPPRESS_ASAN CallFrame* CallFrame::unsafeCallerFrame(VMEntryFrame*& currVMEntryFrame)
+{
+    if (unsafeCallerFrameOrVMEntryFrame() == currVMEntryFrame) {
+        VMEntryRecord* currVMEntryRecord = vmEntryRecord(currVMEntryFrame);
+        currVMEntryFrame = currVMEntryRecord->unsafePrevTopVMEntryFrame();
+        return currVMEntryRecord->unsafePrevTopCallFrame();
+    }
+    return static_cast<CallFrame*>(unsafeCallerFrameOrVMEntryFrame());
+}
+
+String CallFrame::friendlyFunctionName()
 {
     CodeBlock* codeBlock = this->codeBlock();
-    ASSERT(codeBlock);
-    return registers() + codeBlock->m_numCalleeRegisters;
+    if (!codeBlock)
+        return emptyString();
+
+    switch (codeBlock->codeType()) {
+    case EvalCode:
+        return ASCIILiteral("eval code");
+    case ModuleCode:
+        return ASCIILiteral("module code");
+    case GlobalCode:
+        return ASCIILiteral("global code");
+    case FunctionCode:
+        if (callee())
+            return getCalculatedDisplayName(this, callee());
+        return emptyString();
+    }
+
+    ASSERT_NOT_REACHED();
+    return emptyString();
+}
+
+void CallFrame::dump(PrintStream& out)
+{
+    if (CodeBlock* codeBlock = this->codeBlock()) {
+        out.print(codeBlock->inferredName(), "#", codeBlock->hashAsStringIfPossible(), " [", codeBlock->jitType(), "]");
+
+        out.print("(");
+        thisValue().dumpForBacktrace(out);
+
+        for (size_t i = 0; i < argumentCount(); ++i) {
+            out.print(", ");
+            JSValue value = argument(i);
+            value.dumpForBacktrace(out);
+        }
+
+        out.print(")");
+
+        return;
+    }
+
+    out.print(returnPC());
 }
 
+const char* CallFrame::describeFrame()
+{
+    const size_t bufferSize = 200;
+    static char buffer[bufferSize + 1];
+    
+    WTF::StringPrintStream stringStream;
+
+    dump(stringStream);
+
+    strncpy(buffer, stringStream.toCString().data(), bufferSize);
+    buffer[bufferSize] = '\0';
+    
+    return buffer;
 }
+
+} // namespace JSC
diff --git a/Source/JavaScriptCore/interpreter/CallFrame.h b/Source/JavaScriptCore/interpreter/CallFrame.h
index c09132c57..980b92fb2 100644
--- a/Source/JavaScriptCore/interpreter/CallFrame.h
+++ b/Source/JavaScriptCore/interpreter/CallFrame.h
@@ -1,7 +1,7 @@
 /*
  *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
- *  Copyright (C) 2003, 2007, 2008, 2011 Apple Inc. All rights reserved.
+ *  Copyright (C) 2003, 2007, 2008, 2011, 2013-2015 Apple Inc. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
@@ -24,36 +24,62 @@
 #define CallFrame_h
 
 #include "AbstractPC.h"
-#include "VM.h"
 #include "JSStack.h"
 #include "MacroAssemblerCodeRef.h"
 #include "Register.h"
+#include "StackVisitor.h"
+#include "VM.h"
+#include "VMEntryRecord.h"
 
 namespace JSC  {
 
     class Arguments;
-    class JSActivation;
     class Interpreter;
     class JSScope;
 
+    struct CallSiteIndex {
+        CallSiteIndex()
+            : m_bits(UINT_MAX)
+        {
+        }
+        
+        explicit CallSiteIndex(uint32_t bits)
+            : m_bits(bits)
+        { }
+#if USE(JSVALUE32_64)
+        explicit CallSiteIndex(Instruction* instruction)
+            : m_bits(bitwise_cast<uint32_t>(instruction))
+        { }
+#endif
+
+        explicit operator bool() const { return m_bits != UINT_MAX; }
+        
+        inline uint32_t bits() const { return m_bits; }
+
+    private:
+        uint32_t m_bits;
+    };
+
     // Represents the current state of script execution.
     // Passed as the first argument to most functions.
     class ExecState : private Register {
     public:
         JSValue calleeAsValue() const { return this[JSStack::Callee].jsValue(); }
-        JSObject* callee() const { return this[JSStack::Callee].function(); }
+        JSObject* callee() const { return this[JSStack::Callee].object(); }
+        SUPPRESS_ASAN JSValue unsafeCallee() const { return this[JSStack::Callee].asanUnsafeJSValue(); }
         CodeBlock* codeBlock() const { return this[JSStack::CodeBlock].Register::codeBlock(); }
-        JSScope* scope() const
+        SUPPRESS_ASAN CodeBlock* unsafeCodeBlock() const { return this[JSStack::CodeBlock].Register::asanUnsafeCodeBlock(); }
+        JSScope* scope(int scopeRegisterOffset) const
         {
-            ASSERT(this[JSStack::ScopeChain].Register::scope());
-            return this[JSStack::ScopeChain].Register::scope();
+            ASSERT(this[scopeRegisterOffset].Register::scope());
+            return this[scopeRegisterOffset].Register::scope();
         }
 
         // Global object in which execution began.
-        JSGlobalObject* dynamicGlobalObject();
+        JS_EXPORT_PRIVATE JSGlobalObject* vmEntryGlobalObject();
 
         // Global object in which the currently executing code was defined.
-        // Differs from dynamicGlobalObject() during function calls across web browser frames.
+        // Differs from vmEntryGlobalObject() during function calls across web browser frames.
         JSGlobalObject* lexicalGlobalObject() const;
 
         // Differs from lexicalGlobalObject because this will have DOM window shell rather than
@@ -67,132 +93,101 @@ namespace JSC  {
         // pointer, so these are inefficient, and should be used sparingly in new code.
         // But they're used in many places in legacy code, so they're not going away any time soon.
 
-        void clearException() { vm().exception = JSValue(); }
-        void clearSupplementaryExceptionInfo()
-        {
-            vm().clearExceptionStack();
-        }
+        void clearException() { vm().clearException(); }
+
+        Exception* exception() const { return vm().exception(); }
+        bool hadException() const { return !!vm().exception(); }
 
-        JSValue exception() const { return vm().exception; }
-        bool hadException() const { return vm().exception; }
+        Exception* lastException() const { return vm().lastException(); }
+        void clearLastException() { vm().clearLastException(); }
 
+        AtomicStringTable* atomicStringTable() const { return vm().atomicStringTable(); }
         const CommonIdentifiers& propertyNames() const { return *vm().propertyNames; }
         const MarkedArgumentBuffer& emptyList() const { return *vm().emptyList; }
         Interpreter* interpreter() { return vm().interpreter; }
         Heap* heap() { return &vm().heap; }
-#ifndef NDEBUG
-        void dumpCaller();
-#endif
-        static const HashTable* arrayConstructorTable(CallFrame* callFrame) { return callFrame->vm().arrayConstructorTable; }
-        static const HashTable* arrayPrototypeTable(CallFrame* callFrame) { return callFrame->vm().arrayPrototypeTable; }
-        static const HashTable* booleanPrototypeTable(CallFrame* callFrame) { return callFrame->vm().booleanPrototypeTable; }
-        static const HashTable* dateTable(CallFrame* callFrame) { return callFrame->vm().dateTable; }
-        static const HashTable* dateConstructorTable(CallFrame* callFrame) { return callFrame->vm().dateConstructorTable; }
-        static const HashTable* errorPrototypeTable(CallFrame* callFrame) { return callFrame->vm().errorPrototypeTable; }
-        static const HashTable* globalObjectTable(CallFrame* callFrame) { return callFrame->vm().globalObjectTable; }
-        static const HashTable* jsonTable(CallFrame* callFrame) { return callFrame->vm().jsonTable; }
-        static const HashTable* mathTable(CallFrame* callFrame) { return callFrame->vm().mathTable; }
-        static const HashTable* numberConstructorTable(CallFrame* callFrame) { return callFrame->vm().numberConstructorTable; }
-        static const HashTable* numberPrototypeTable(CallFrame* callFrame) { return callFrame->vm().numberPrototypeTable; }
-        static const HashTable* objectConstructorTable(CallFrame* callFrame) { return callFrame->vm().objectConstructorTable; }
-        static const HashTable* privateNamePrototypeTable(CallFrame* callFrame) { return callFrame->vm().privateNamePrototypeTable; }
-        static const HashTable* regExpTable(CallFrame* callFrame) { return callFrame->vm().regExpTable; }
-        static const HashTable* regExpConstructorTable(CallFrame* callFrame) { return callFrame->vm().regExpConstructorTable; }
-        static const HashTable* regExpPrototypeTable(CallFrame* callFrame) { return callFrame->vm().regExpPrototypeTable; }
-        static const HashTable* stringConstructorTable(CallFrame* callFrame) { return callFrame->vm().stringConstructorTable; }
+
 
         static CallFrame* create(Register* callFrameBase) { return static_cast<CallFrame*>(callFrameBase); }
         Register* registers() { return this; }
+        const Register* registers() const { return this; }
 
         CallFrame& operator=(const Register& r) { *static_cast<Register*>(this) = r; return *this; }
 
-        CallFrame* callerFrame() const { return this[JSStack::CallerFrame].callFrame(); }
-#if ENABLE(JIT) || ENABLE(LLINT)
-        ReturnAddressPtr returnPC() const { return ReturnAddressPtr(this[JSStack::ReturnPC].vPC()); }
-        bool hasReturnPC() const { return !!this[JSStack::ReturnPC].vPC(); }
-        void clearReturnPC() { registers()[JSStack::ReturnPC] = static_cast<Instruction*>(0); }
-#endif
+        CallFrame* callerFrame() const { return static_cast<CallFrame*>(callerFrameOrVMEntryFrame()); }
+        void* callerFrameOrVMEntryFrame() const { return callerFrameAndPC().callerFrame; }
+        SUPPRESS_ASAN void* unsafeCallerFrameOrVMEntryFrame() const { return unsafeCallerFrameAndPC().callerFrame; }
+
+        CallFrame* unsafeCallerFrame(VMEntryFrame*&);
+        JS_EXPORT_PRIVATE CallFrame* callerFrame(VMEntryFrame*&);
+
+        static ptrdiff_t callerFrameOffset() { return OBJECT_OFFSETOF(CallerFrameAndPC, callerFrame); }
+
+        ReturnAddressPtr returnPC() const { return ReturnAddressPtr(callerFrameAndPC().pc); }
+        bool hasReturnPC() const { return !!callerFrameAndPC().pc; }
+        void clearReturnPC() { callerFrameAndPC().pc = 0; }
+        static ptrdiff_t returnPCOffset() { return OBJECT_OFFSETOF(CallerFrameAndPC, pc); }
         AbstractPC abstractReturnPC(VM& vm) { return AbstractPC(vm, this); }
-#if USE(JSVALUE32_64)
-        unsigned bytecodeOffsetForNonDFGCode() const;
-        void setBytecodeOffsetForNonDFGCode(unsigned offset);
-#else
-        unsigned bytecodeOffsetForNonDFGCode() const
-        {
-            ASSERT(codeBlock());
-            return this[JSStack::ArgumentCount].tag();
-        }
+
+        bool callSiteBitsAreBytecodeOffset() const;
+        bool callSiteBitsAreCodeOriginIndex() const;
+
+        unsigned callSiteAsRawBits() const;
+        unsigned unsafeCallSiteAsRawBits() const;
+        CallSiteIndex callSiteIndex() const;
+        CallSiteIndex unsafeCallSiteIndex() const;
+    private:
+        unsigned callSiteBitsAsBytecodeOffset() const;
+    public:
+
+        // This will try to get you the bytecode offset, but you should be aware that
+        // this bytecode offset may be bogus in the presence of inlining. This will
+        // also return 0 if the call frame has no notion of bytecode offsets (for
+        // example if it's native code).
+        // https://bugs.webkit.org/show_bug.cgi?id=121754
+        unsigned bytecodeOffset();
         
-        void setBytecodeOffsetForNonDFGCode(unsigned offset)
-        {
-            ASSERT(codeBlock());
-            this[JSStack::ArgumentCount].tag() = static_cast<int32_t>(offset);
-        }
-#endif
+        // This will get you a CodeOrigin. It will always succeed. May return
+        // CodeOrigin(0) if we're in native code.
+        CodeOrigin codeOrigin();
 
-        Register* frameExtent()
+        Register* topOfFrame()
         {
             if (!codeBlock())
                 return registers();
-            return frameExtentInternal();
+            return topOfFrameInternal();
         }
     
-        Register* frameExtentInternal();
-    
-#if ENABLE(DFG_JIT)
-        InlineCallFrame* inlineCallFrame() const { return this[JSStack::ReturnPC].asInlineCallFrame(); }
-        unsigned codeOriginIndexForDFG() const { return this[JSStack::ArgumentCount].tag(); }
-#else
-        // This will never be called if !ENABLE(DFG_JIT) since all calls should be guarded by
-        // isInlineCallFrame(). But to make it easier to write code without having a bunch of
-        // #if's, we make a dummy implementation available anyway.
-        InlineCallFrame* inlineCallFrame() const
-        {
-            RELEASE_ASSERT_NOT_REACHED();
-            return 0;
-        }
-#endif
-#if USE(JSVALUE32_64)
-        Instruction* currentVPC() const
-        {
-            return bitwise_cast<Instruction*>(this[JSStack::ArgumentCount].tag());
-        }
-        void setCurrentVPC(Instruction* vpc)
-        {
-            this[JSStack::ArgumentCount].tag() = bitwise_cast<int32_t>(vpc);
-        }
-#else
-        Instruction* currentVPC() const;
+        Instruction* currentVPC() const; // This only makes sense in the LLInt and baseline.
         void setCurrentVPC(Instruction* vpc);
-#endif
 
-        void setCallerFrame(CallFrame* callerFrame) { static_cast<Register*>(this)[JSStack::CallerFrame] = callerFrame; }
-        void setScope(JSScope* scope) { static_cast<Register*>(this)[JSStack::ScopeChain] = scope; }
+        void setCallerFrame(CallFrame* frame) { callerFrameAndPC().callerFrame = frame; }
+        void setScope(int scopeRegisterOffset, JSScope* scope) { static_cast<Register*>(this)[scopeRegisterOffset] = scope; }
 
-        ALWAYS_INLINE void init(CodeBlock* codeBlock, Instruction* vPC, JSScope* scope,
-            CallFrame* callerFrame, int argc, JSObject* callee)
-        {
-            ASSERT(callerFrame); // Use noCaller() rather than 0 for the outer host call frame caller.
-            ASSERT(callerFrame == noCaller() || callerFrame->removeHostCallFrameFlag()->stack()->end() >= this);
-
-            setCodeBlock(codeBlock);
-            setScope(scope);
-            setCallerFrame(callerFrame);
-            setReturnPC(vPC); // This is either an Instruction* or a pointer into JIT generated code stored as an Instruction*.
-            setArgumentCountIncludingThis(argc); // original argument count (for the sake of the "arguments" object)
-            setCallee(callee);
+        ALWAYS_INLINE void init(CodeBlock* codeBlock, Instruction* vPC,
+            CallFrame* callerFrame, int argc, JSObject* callee) 
+        { 
+            ASSERT(callerFrame == noCaller() || callerFrame->stack()->containsAddress(this)); 
+
+            setCodeBlock(codeBlock); 
+            setCallerFrame(callerFrame); 
+            setReturnPC(vPC); // This is either an Instruction* or a pointer into JIT generated code stored as an Instruction*. 
+            setArgumentCountIncludingThis(argc); // original argument count (for the sake of the "arguments" object) 
+            setCallee(callee); 
         }
 
         // Read a register from the codeframe (or constant from the CodeBlock).
         Register& r(int);
-        // Read a register for a non-constant 
+        Register& r(VirtualRegister);
+        // Read a register for a non-constant
         Register& uncheckedR(int);
+        Register& uncheckedR(VirtualRegister);
 
         // Access to arguments as passed. (After capture, arguments may move to a different location.)
         size_t argumentCount() const { return argumentCountIncludingThis() - 1; }
         size_t argumentCountIncludingThis() const { return this[JSStack::ArgumentCount].payload(); }
-        static int argumentOffset(int argument) { return s_firstArgumentOffset - argument; }
-        static int argumentOffsetIncludingThis(int argument) { return s_thisArgumentOffset - argument; }
+        static int argumentOffset(int argument) { return (JSStack::FirstArgument + argument); }
+        static int argumentOffsetIncludingThis(int argument) { return (JSStack::ThisArgument + argument); }
 
         // In the following (argument() and setArgument()), the 'argument'
         // parameter is the index of the arguments of the target function of
@@ -207,85 +202,69 @@ namespace JSC  {
         {
             if (argument >= argumentCount())
                  return jsUndefined();
-            return this[argumentOffset(argument)].jsValue();
+            return getArgumentUnsafe(argument);
+        }
+        JSValue uncheckedArgument(size_t argument)
+        {
+            ASSERT(argument < argumentCount());
+            return getArgumentUnsafe(argument);
         }
         void setArgument(size_t argument, JSValue value)
         {
             this[argumentOffset(argument)] = value;
         }
 
+        JSValue getArgumentUnsafe(size_t argIndex)
+        {
+            // User beware! This method does not verify that there is a valid
+            // argument at the specified argIndex. This is used for debugging
+            // and verification code only. The caller is expected to know what
+            // he/she is doing when calling this method.
+            return this[argumentOffset(argIndex)].jsValue();
+        }
+
         static int thisArgumentOffset() { return argumentOffsetIncludingThis(0); }
         JSValue thisValue() { return this[thisArgumentOffset()].jsValue(); }
         void setThisValue(JSValue value) { this[thisArgumentOffset()] = value; }
 
-        JSValue argumentAfterCapture(size_t argument);
-
-        static int offsetFor(size_t argumentCountIncludingThis) { return argumentCountIncludingThis + JSStack::CallFrameHeaderSize; }
+        // Under the constructor implemented in C++, thisValue holds the newTarget instead of the automatically constructed value.
+        // The result of this function is only effective under the "construct" context.
+        JSValue newTarget() { return thisValue(); }
 
-        // FIXME: Remove these.
-        int hostThisRegister() { return thisArgumentOffset(); }
-        JSValue hostThisValue() { return thisValue(); }
+        JSValue argumentAfterCapture(size_t argument);
 
-        static CallFrame* noCaller() { return reinterpret_cast<CallFrame*>(HostCallFrameFlag); }
+        static int offsetFor(size_t argumentCountIncludingThis) { return argumentCountIncludingThis + JSStack::ThisArgument - 1; }
 
-        bool hasHostCallFrameFlag() const { return reinterpret_cast<intptr_t>(this) & HostCallFrameFlag; }
-        CallFrame* addHostCallFrameFlag() const { return reinterpret_cast<CallFrame*>(reinterpret_cast<intptr_t>(this) | HostCallFrameFlag); }
-        CallFrame* removeHostCallFrameFlag() { return reinterpret_cast<CallFrame*>(reinterpret_cast<intptr_t>(this) & ~HostCallFrameFlag); }
+        static CallFrame* noCaller() { return 0; }
 
         void setArgumentCountIncludingThis(int count) { static_cast<Register*>(this)[JSStack::ArgumentCount].payload() = count; }
-        void setCallee(JSObject* callee) { static_cast<Register*>(this)[JSStack::Callee] = Register::withCallee(callee); }
+        void setCallee(JSObject* callee) { static_cast<Register*>(this)[JSStack::Callee] = callee; }
         void setCodeBlock(CodeBlock* codeBlock) { static_cast<Register*>(this)[JSStack::CodeBlock] = codeBlock; }
-        void setReturnPC(void* value) { static_cast<Register*>(this)[JSStack::ReturnPC] = (Instruction*)value; }
-        
-#if ENABLE(DFG_JIT)
-        bool isInlineCallFrame();
-        
-        void setInlineCallFrame(InlineCallFrame* inlineCallFrame) { static_cast<Register*>(this)[JSStack::ReturnPC] = inlineCallFrame; }
-        
-        // Call this to get the semantically correct JS CallFrame* for the
-        // currently executing function.
-        CallFrame* trueCallFrame(AbstractPC);
-        
-        // Call this to get the semantically correct JS CallFrame* corresponding
-        // to the caller. This resolves issues surrounding inlining and the
-        // HostCallFrameFlag stuff.
-        CallFrame* trueCallerFrame();
-        
-        CodeBlock* someCodeBlockForPossiblyInlinedCode();
-#else
-        bool isInlineCallFrame() { return false; }
-        
-        CallFrame* trueCallFrame(AbstractPC) { return this; }
-        CallFrame* trueCallerFrame() { return callerFrame()->removeHostCallFrameFlag(); }
-        
-        CodeBlock* someCodeBlockForPossiblyInlinedCode() { return codeBlock(); }
-#endif
-        CallFrame* callerFrameNoFlags() { return callerFrame()->removeHostCallFrameFlag(); }
-        
-        // Call this to get the true call frame (accounted for inlining and any
-        // other optimizations), when you have entered into VM code through one
-        // of the "blessed" entrypoints (JITStubs or DFGOperations). This means
-        // that if you're pretty much anywhere in the VM you can safely call this;
-        // though if you were to magically get an ExecState* by, say, interrupting
-        // a thread that is running JS code and brutishly scraped the call frame
-        // register, calling this method would probably lead to horrible things
-        // happening.
-        CallFrame* trueCallFrameFromVMCode() { return trueCallFrame(AbstractPC()); }
+        void setReturnPC(void* value) { callerFrameAndPC().pc = reinterpret_cast<Instruction*>(value); }
+
+        String friendlyFunctionName();
+
+        // CallFrame::iterate() expects a Functor that implements the following method:
+        //     StackVisitor::Status operator()(StackVisitor&);
+
+        template <typename Functor> void iterate(Functor& functor)
+        {
+            StackVisitor::visit<Functor>(this, functor);
+        }
+
+        void dump(PrintStream&);
+        JS_EXPORT_PRIVATE const char* describeFrame();
 
     private:
-        static const intptr_t HostCallFrameFlag = 1;
-        static const int s_thisArgumentOffset = -1 - JSStack::CallFrameHeaderSize;
-        static const int s_firstArgumentOffset = s_thisArgumentOffset - 1;
 
 #ifndef NDEBUG
         JSStack* stack();
 #endif
-#if ENABLE(DFG_JIT)
-        bool isInlineCallFrameSlow();
-#endif
         ExecState();
         ~ExecState();
 
+        Register* topOfFrameInternal();
+
         // The following are for internal use in debugging and verification
         // code only and not meant as an API for general usage:
 
@@ -299,24 +278,18 @@ namespace JSC  {
             int offset = reg - this->registers();
 
             // The offset is defined (based on argumentOffset()) to be:
-            //       offset = s_firstArgumentOffset - argIndex;
+            //       offset = JSStack::FirstArgument - argIndex;
             // Hence:
-            //       argIndex = s_firstArgumentOffset - offset;
-            size_t argIndex = s_firstArgumentOffset - offset;
+            //       argIndex = JSStack::FirstArgument - offset;
+            size_t argIndex = offset - JSStack::FirstArgument;
             return argIndex;
         }
 
-        JSValue getArgumentUnsafe(size_t argIndex)
-        {
-            // User beware! This method does not verify that there is a valid
-            // argument at the specified argIndex. This is used for debugging
-            // and verification code only. The caller is expected to know what
-            // he/she is doing when calling this method.
-            return this[argumentOffset(argIndex)].jsValue();
-        }
+        CallerFrameAndPC& callerFrameAndPC() { return *reinterpret_cast<CallerFrameAndPC*>(this); }
+        const CallerFrameAndPC& callerFrameAndPC() const { return *reinterpret_cast<const CallerFrameAndPC*>(this); }
+        SUPPRESS_ASAN const CallerFrameAndPC& unsafeCallerFrameAndPC() const { return *reinterpret_cast<const CallerFrameAndPC*>(this); }
 
         friend class JSStack;
-        friend class VMInspector;
     };
 
 } // namespace JSC
diff --git a/Source/JavaScriptCore/interpreter/CallFrameClosure.h b/Source/JavaScriptCore/interpreter/CallFrameClosure.h
index 7ae1e6fdf..2c03b7452 100644
--- a/Source/JavaScriptCore/interpreter/CallFrameClosure.h
+++ b/Source/JavaScriptCore/interpreter/CallFrameClosure.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2009 Apple Inc. All rights reserved.
+ * Copyright (C) 2009, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -26,11 +26,13 @@
 #ifndef CallFrameClosure_h
 #define CallFrameClosure_h
 
+#include "ProtoCallFrame.h"
+
 namespace JSC {
 
 struct CallFrameClosure {
     CallFrame* oldCallFrame;
-    CallFrame* newCallFrame;
+    ProtoCallFrame* protoCallFrame;
     JSFunction* function;
     FunctionExecutable* functionExecutable;
     VM* vm;
@@ -40,23 +42,12 @@ struct CallFrameClosure {
     
     void setThis(JSValue value)
     {
-        newCallFrame->setThisValue(value);
+        protoCallFrame->setThisValue(value);
     }
 
     void setArgument(int argument, JSValue value)
     {
-        newCallFrame->setArgument(argument, value);
-    }
-
-    void resetCallFrame()
-    {
-        newCallFrame->setScope(scope);
-        // setArgument() takes an arg index that starts from 0 for the first
-        // argument after the 'this' value. Since both argumentCountIncludingThis
-        // and parameterCountIncludingThis includes the 'this' value, we need to
-        // subtract 1 from them to make i a valid argument index for setArgument().
-        for (int i = argumentCountIncludingThis-1; i < parameterCountIncludingThis-1; ++i)
-            newCallFrame->setArgument(i, jsUndefined());
+        protoCallFrame->setArgument(argument, value);
     }
 };
 
diff --git a/Source/JavaScriptCore/interpreter/Interpreter.cpp b/Source/JavaScriptCore/interpreter/Interpreter.cpp
index 844f5f252..18a90760d 100644
--- a/Source/JavaScriptCore/interpreter/Interpreter.cpp
+++ b/Source/JavaScriptCore/interpreter/Interpreter.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
+ * Copyright (C) 2008, 2009, 2010, 2012-2015 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Cameron Zwarich <cwzwarich@uwaterloo.ca>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -11,7 +11,7 @@
  * 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.
  *
@@ -30,44 +30,53 @@
 #include "config.h"
 #include "Interpreter.h"
 
-#include "Arguments.h"
 #include "BatchedTransitionOptimizer.h"
-#include "CallFrame.h"
 #include "CallFrameClosure.h"
+#include "ClonedArguments.h"
 #include "CodeBlock.h"
+#include "DirectArguments.h"
 #include "Heap.h"
 #include "Debugger.h"
 #include "DebuggerCallFrame.h"
 #include "ErrorInstance.h"
 #include "EvalCodeCache.h"
+#include "Exception.h"
 #include "ExceptionHelpers.h"
 #include "GetterSetter.h"
-#include "JSActivation.h"
 #include "JSArray.h"
 #include "JSBoundFunction.h"
-#include "JSNameScope.h"
+#include "JSCInlines.h"
+#include "JSLexicalEnvironment.h"
+#include "JSModuleEnvironment.h"
 #include "JSNotAnObject.h"
-#include "JSPropertyNameIterator.h"
 #include "JSStackInlines.h"
 #include "JSString.h"
 #include "JSWithScope.h"
 #include "LLIntCLoop.h"
+#include "LLIntThunks.h"
 #include "LegacyProfiler.h"
 #include "LiteralParser.h"
-#include "NameInstance.h"
 #include "ObjectPrototype.h"
-#include "Operations.h"
 #include "Parser.h"
+#include "ProtoCallFrame.h"
 #include "RegExpObject.h"
 #include "RegExpPrototype.h"
 #include "Register.h"
 #include "SamplingTool.h"
+#include "ScopedArguments.h"
+#include "StackAlignment.h"
+#include "StackVisitor.h"
 #include "StrictEvalActivation.h"
 #include "StrongInlines.h"
-#include "VMStackBounds.h"
+#include "Symbol.h"
+#include "VMEntryScope.h"
+#include "VMInlines.h"
+#include "VirtualRegister.h"
+
 #include <limits.h>
 #include <stdio.h>
 #include <wtf/StackStats.h>
+#include <wtf/StdLibExtras.h>
 #include <wtf/StringPrintStream.h>
 #include <wtf/Threading.h>
 #include <wtf/WTFThreadData.h>
@@ -77,36 +86,53 @@
 #include "JIT.h"
 #endif
 
-#define WTF_USE_GCC_COMPUTED_GOTO_WORKAROUND (ENABLE(LLINT) && !defined(__llvm__))
-
 using namespace std;
 
 namespace JSC {
 
-Interpreter::ErrorHandlingMode::ErrorHandlingMode(ExecState *exec)
-    : m_interpreter(*exec->interpreter())
+String StackFrame::friendlySourceURL() const
 {
-    if (!m_interpreter.m_errorHandlingModeReentry)
-        m_interpreter.stack().enableErrorStackReserve();
-    m_interpreter.m_errorHandlingModeReentry++;
+    String traceLine;
+    
+    switch (codeType) {
+    case StackFrameEvalCode:
+    case StackFrameModuleCode:
+    case StackFrameFunctionCode:
+    case StackFrameGlobalCode:
+        if (!sourceURL.isEmpty())
+            traceLine = sourceURL.impl();
+        break;
+    case StackFrameNativeCode:
+        traceLine = "[native code]";
+        break;
+    }
+    return traceLine.isNull() ? emptyString() : traceLine;
 }
 
-Interpreter::ErrorHandlingMode::~ErrorHandlingMode()
+String StackFrame::friendlyFunctionName(CallFrame* callFrame) const
 {
-    m_interpreter.m_errorHandlingModeReentry--;
-    ASSERT(m_interpreter.m_errorHandlingModeReentry >= 0);
-    if (!m_interpreter.m_errorHandlingModeReentry)
-        m_interpreter.stack().disableErrorStackReserve();
-}
-
-static CallFrame* getCallerInfo(VM*, CallFrame*, unsigned& bytecodeOffset, CodeBlock*& callerOut);
-
-// Returns the depth of the scope chain within a given call frame.
-static int depth(CodeBlock* codeBlock, JSScope* sc)
-{
-    if (!codeBlock->needsFullScopeChain())
-        return 0;
-    return sc->localDepth();
+    String traceLine;
+    JSObject* stackFrameCallee = callee.get();
+
+    switch (codeType) {
+    case StackFrameEvalCode:
+        traceLine = "eval code";
+        break;
+    case StackFrameModuleCode:
+        traceLine = "module code";
+        break;
+    case StackFrameNativeCode:
+        if (callee)
+            traceLine = getCalculatedDisplayName(callFrame, stackFrameCallee).impl();
+        break;
+    case StackFrameFunctionCode:
+        traceLine = getCalculatedDisplayName(callFrame, stackFrameCallee).impl();
+        break;
+    case StackFrameGlobalCode:
+        traceLine = "global code";
+        break;
+    }
+    return traceLine.isNull() ? emptyString() : traceLine;
 }
 
 JSValue eval(CallFrame* callFrame)
@@ -117,21 +143,27 @@ JSValue eval(CallFrame* callFrame)
     JSValue program = callFrame->argument(0);
     if (!program.isString())
         return program;
-    
+
     TopCallFrameSetter topCallFrame(callFrame->vm(), callFrame);
+    JSGlobalObject* globalObject = callFrame->lexicalGlobalObject();
+    if (!globalObject->evalEnabled()) {
+        callFrame->vm().throwException(callFrame, createEvalError(callFrame, globalObject->evalDisabledErrorMessage()));
+        return jsUndefined();
+    }
     String programSource = asString(program)->value(callFrame);
     if (callFrame->hadException())
         return JSValue();
     
     CallFrame* callerFrame = callFrame->callerFrame();
     CodeBlock* callerCodeBlock = callerFrame->codeBlock();
-    JSScope* callerScopeChain = callerFrame->scope();
-    EvalExecutable* eval = callerCodeBlock->evalCodeCache().tryGet(callerCodeBlock->isStrictMode(), programSource, callerScopeChain);
+    JSScope* callerScopeChain = callerFrame->uncheckedR(callerCodeBlock->scopeRegister().offset()).Register::scope();
+    UnlinkedCodeBlock* callerUnlinkedCodeBlock = callerCodeBlock->unlinkedCodeBlock();
+
+    bool isArrowFunctionContext = callerUnlinkedCodeBlock->isArrowFunction() || callerUnlinkedCodeBlock->isArrowFunctionContext();
+    EvalExecutable* eval = callerCodeBlock->evalCodeCache().tryGet(callerCodeBlock->isStrictMode(), programSource, isArrowFunctionContext, callerScopeChain);
 
     if (!eval) {
         if (!callerCodeBlock->isStrictMode()) {
-            // FIXME: We can use the preparser in strict mode, we just need additional logic
-            // to prevent duplicates.
             if (programSource.is8Bit()) {
                 LiteralParser<LChar> preparser(callFrame, programSource.characters8(), programSource.length(), NonStrictJSON);
                 if (JSValue parsedObject = preparser.tryLiteralParse())
@@ -144,102 +176,124 @@ JSValue eval(CallFrame* callFrame)
         }
         
         // If the literal parser bailed, it should not have thrown exceptions.
-        ASSERT(!callFrame->vm().exception);
+        ASSERT(!callFrame->vm().exception());
 
-        JSValue exceptionValue;
-        eval = callerCodeBlock->evalCodeCache().getSlow(callFrame, callerCodeBlock->unlinkedCodeBlock()->codeCacheForEval().get(), callerCodeBlock->ownerExecutable(), callerCodeBlock->isStrictMode(), programSource, callerScopeChain, exceptionValue);
-        
-        ASSERT(!eval == exceptionValue);
-        if (UNLIKELY(!eval))
-            return throwError(callFrame, exceptionValue);
+        ThisTDZMode thisTDZMode = ThisTDZMode::CheckIfNeeded;
+        if (callerUnlinkedCodeBlock->constructorKind() == ConstructorKind::Derived)
+            thisTDZMode = ThisTDZMode::AlwaysCheck;
+
+        eval = callerCodeBlock->evalCodeCache().getSlow(callFrame, callerCodeBlock, callerCodeBlock->isStrictMode(), thisTDZMode, callerCodeBlock->unlinkedCodeBlock()->derivedContextType(), callerCodeBlock->unlinkedCodeBlock()->isArrowFunction(), programSource, callerScopeChain);
+        if (!eval)
+            return jsUndefined();
     }
 
     JSValue thisValue = callerFrame->thisValue();
-    ASSERT(isValidThisObject(thisValue, callFrame));
     Interpreter* interpreter = callFrame->vm().interpreter;
     return interpreter->execute(eval, callFrame, thisValue, callerScopeChain);
 }
 
-CallFrame* loadVarargs(CallFrame* callFrame, JSStack* stack, JSValue thisValue, JSValue arguments, int firstFreeRegister)
+unsigned sizeOfVarargs(CallFrame* callFrame, JSValue arguments, uint32_t firstVarArgOffset)
 {
-    if (!arguments) { // f.apply(x, arguments), with arguments unmodified.
-        unsigned argumentCountIncludingThis = callFrame->argumentCountIncludingThis();
-        CallFrame* newCallFrame = CallFrame::create(callFrame->registers() + firstFreeRegister + argumentCountIncludingThis + JSStack::CallFrameHeaderSize);
-        if (argumentCountIncludingThis > Arguments::MaxArguments + 1 || !stack->grow(newCallFrame->registers())) {
-            callFrame->vm().exception = createStackOverflowError(callFrame);
+    if (UNLIKELY(!arguments.isCell())) {
+        if (arguments.isUndefinedOrNull())
             return 0;
-        }
-
-        newCallFrame->setArgumentCountIncludingThis(argumentCountIncludingThis);
-        newCallFrame->setThisValue(thisValue);
-        for (size_t i = 0; i < callFrame->argumentCount(); ++i)
-            newCallFrame->setArgument(i, callFrame->argumentAfterCapture(i));
-        return newCallFrame;
+        
+        callFrame->vm().throwException(callFrame, createInvalidFunctionApplyParameterError(callFrame, arguments));
+        return 0;
     }
-
-    if (arguments.isUndefinedOrNull()) {
-        CallFrame* newCallFrame = CallFrame::create(callFrame->registers() + firstFreeRegister + 1 + JSStack::CallFrameHeaderSize);
-        if (!stack->grow(newCallFrame->registers())) {
-            callFrame->vm().exception = createStackOverflowError(callFrame);
-            return 0;
-        }
-        newCallFrame->setArgumentCountIncludingThis(1);
-        newCallFrame->setThisValue(thisValue);
-        return newCallFrame;
+    
+    JSCell* cell = arguments.asCell();
+    unsigned length;
+    switch (cell->type()) {
+    case DirectArgumentsType:
+        length = jsCast<DirectArguments*>(cell)->length(callFrame);
+        break;
+    case ScopedArgumentsType:
+        length =jsCast<ScopedArguments*>(cell)->length(callFrame);
+        break;
+    case StringType:
+        callFrame->vm().throwException(callFrame, createInvalidFunctionApplyParameterError(callFrame,  arguments));
+        return 0;
+    default:
+        ASSERT(arguments.isObject());
+        if (isJSArray(cell))
+            length = jsCast<JSArray*>(cell)->length();
+        else
+            length = jsCast<JSObject*>(cell)->get(callFrame, callFrame->propertyNames().length).toUInt32(callFrame);
+        break;
     }
+    
+    if (length >= firstVarArgOffset)
+        length -= firstVarArgOffset;
+    else
+        length = 0;
+    
+    return length;
+}
 
-    if (!arguments.isObject()) {
-        callFrame->vm().exception = createInvalidParameterError(callFrame, "Function.prototype.apply", arguments);
+unsigned sizeFrameForVarargs(CallFrame* callFrame, JSStack* stack, JSValue arguments, unsigned numUsedStackSlots, uint32_t firstVarArgOffset)
+{
+    unsigned length = sizeOfVarargs(callFrame, arguments, firstVarArgOffset);
+    
+    CallFrame* calleeFrame = calleeFrameForVarargs(callFrame, numUsedStackSlots, length + 1);
+    if (length > maxArguments || !stack->ensureCapacityFor(calleeFrame->registers())) {
+        throwStackOverflowError(callFrame);
         return 0;
     }
+    
+    return length;
+}
 
-    if (asObject(arguments)->classInfo() == &Arguments::s_info) {
-        Arguments* argsObject = asArguments(arguments);
-        unsigned argCount = argsObject->length(callFrame);
-        CallFrame* newCallFrame = CallFrame::create(callFrame->registers() + firstFreeRegister + CallFrame::offsetFor(argCount + 1));
-        if (argCount > Arguments::MaxArguments || !stack->grow(newCallFrame->registers())) {
-            callFrame->vm().exception = createStackOverflowError(callFrame);
-            return 0;
+void loadVarargs(CallFrame* callFrame, VirtualRegister firstElementDest, JSValue arguments, uint32_t offset, uint32_t length)
+{
+    if (UNLIKELY(!arguments.isCell()) || !length)
+        return;
+    
+    JSCell* cell = arguments.asCell();
+    switch (cell->type()) {
+    case DirectArgumentsType:
+        jsCast<DirectArguments*>(cell)->copyToArguments(callFrame, firstElementDest, offset, length);
+        return;
+    case ScopedArgumentsType:
+        jsCast<ScopedArguments*>(cell)->copyToArguments(callFrame, firstElementDest, offset, length);
+        return;
+    default: {
+        ASSERT(arguments.isObject());
+        JSObject* object = jsCast<JSObject*>(cell);
+        if (isJSArray(object)) {
+            jsCast<JSArray*>(object)->copyToArguments(callFrame, firstElementDest, offset, length);
+            return;
         }
-        newCallFrame->setArgumentCountIncludingThis(argCount + 1);
-        newCallFrame->setThisValue(thisValue);
-        argsObject->copyToArguments(callFrame, newCallFrame, argCount);
-        return newCallFrame;
-    }
+        unsigned i;
+        for (i = 0; i < length && object->canGetIndexQuickly(i + offset); ++i)
+            callFrame->r(firstElementDest + i) = object->getIndexQuickly(i + offset);
+        for (; i < length; ++i)
+            callFrame->r(firstElementDest + i) = object->get(callFrame, i + offset);
+        return;
+    } }
+}
 
-    if (isJSArray(arguments)) {
-        JSArray* array = asArray(arguments);
-        unsigned argCount = array->length();
-        CallFrame* newCallFrame = CallFrame::create(callFrame->registers() + firstFreeRegister + CallFrame::offsetFor(argCount + 1));
-        if (argCount > Arguments::MaxArguments || !stack->grow(newCallFrame->registers())) {
-            callFrame->vm().exception = createStackOverflowError(callFrame);
-            return 0;
-        }
-        newCallFrame->setArgumentCountIncludingThis(argCount + 1);
-        newCallFrame->setThisValue(thisValue);
-        array->copyToArguments(callFrame, newCallFrame, argCount);
-        return newCallFrame;
-    }
+void setupVarargsFrame(CallFrame* callFrame, CallFrame* newCallFrame, JSValue arguments, uint32_t offset, uint32_t length)
+{
+    VirtualRegister calleeFrameOffset(newCallFrame - callFrame);
+    
+    loadVarargs(
+        callFrame,
+        calleeFrameOffset + CallFrame::argumentOffset(0),
+        arguments, offset, length);
+    
+    newCallFrame->setArgumentCountIncludingThis(length + 1);
+}
 
-    JSObject* argObject = asObject(arguments);
-    unsigned argCount = argObject->get(callFrame, callFrame->propertyNames().length).toUInt32(callFrame);
-    CallFrame* newCallFrame = CallFrame::create(callFrame->registers() + firstFreeRegister + CallFrame::offsetFor(argCount + 1));
-    if (argCount > Arguments::MaxArguments || !stack->grow(newCallFrame->registers())) {
-        callFrame->vm().exception = createStackOverflowError(callFrame);
-        return 0;
-    }
-    newCallFrame->setArgumentCountIncludingThis(argCount + 1);
+void setupVarargsFrameAndSetThis(CallFrame* callFrame, CallFrame* newCallFrame, JSValue thisValue, JSValue arguments, uint32_t firstVarArgOffset, uint32_t length)
+{
+    setupVarargsFrame(callFrame, newCallFrame, arguments, firstVarArgOffset, length);
     newCallFrame->setThisValue(thisValue);
-    for (size_t i = 0; i < argCount; ++i) {
-        newCallFrame->setArgument(i, asObject(arguments)->get(callFrame, i));
-        if (UNLIKELY(callFrame->vm().exception))
-            return 0;
-    }
-    return newCallFrame;
 }
 
 Interpreter::Interpreter(VM& vm)
     : m_sampleEntryDepth(0)
+    , m_vm(vm)
     , m_stack(vm)
     , m_errorHandlingModeReentry(0)
 #if !ASSERT_DISABLED
@@ -252,11 +306,9 @@ Interpreter::~Interpreter()
 {
 }
 
-void Interpreter::initialize(bool canUseJIT)
+void Interpreter::initialize()
 {
-    UNUSED_PARAM(canUseJIT);
-
-#if ENABLE(COMPUTED_GOTO_OPCODES) && ENABLE(LLINT)
+#if ENABLE(COMPUTED_GOTO_OPCODES)
     m_opcodeTable = LLInt::opcodeMap();
     for (int i = 0; i < numOpcodeIDs; ++i)
         m_opcodeIDTable.add(m_opcodeTable[i], static_cast<OpcodeID>(i));
@@ -285,6 +337,34 @@ void Interpreter::dumpCallFrame(CallFrame* callFrame)
     dumpRegisters(callFrame);
 }
 
+class DumpRegisterFunctor {
+public:
+    DumpRegisterFunctor(const Register*& it)
+        : m_hasSkippedFirstFrame(false)
+        , m_it(it)
+    {
+    }
+
+    StackVisitor::Status operator()(StackVisitor& visitor)
+    {
+        if (!m_hasSkippedFirstFrame) {
+            m_hasSkippedFirstFrame = true;
+            return StackVisitor::Continue;
+        }
+
+        unsigned line = 0;
+        unsigned unusedColumn = 0;
+        visitor->computeLineAndColumn(line, unusedColumn);
+        dataLogF("[ReturnVPC]                | %10p | %d (line %d)\n", m_it, visitor->bytecodeOffset(), line);
+        --m_it;
+        return StackVisitor::Done;
+    }
+
+private:
+    bool m_hasSkippedFirstFrame;
+    const Register*& m_it;
+};
+
 void Interpreter::dumpRegisters(CallFrame* callFrame)
 {
     dataLogF("Register frame: \n\n");
@@ -296,63 +376,57 @@ void Interpreter::dumpRegisters(CallFrame* callFrame)
     const Register* it;
     const Register* end;
 
-    it = callFrame->registers() - JSStack::CallFrameHeaderSize - callFrame->argumentCountIncludingThis();
-    end = callFrame->registers() - JSStack::CallFrameHeaderSize;
-    while (it < end) {
+    it = callFrame->registers() + JSStack::ThisArgument + callFrame->argumentCount();
+    end = callFrame->registers() + JSStack::ThisArgument - 1;
+    while (it > end) {
         JSValue v = it->jsValue();
         int registerNumber = it - callFrame->registers();
-        String name = codeBlock->nameForRegister(registerNumber);
+        String name = codeBlock->nameForRegister(VirtualRegister(registerNumber));
         dataLogF("[r% 3d %14s]      | %10p | %-16s 0x%lld \n", registerNumber, name.ascii().data(), it, toCString(v).data(), (long long)JSValue::encode(v));
-        it++;
+        --it;
     }
     
     dataLogF("-----------------------------------------------------------------------------\n");
     dataLogF("[ArgumentCount]            | %10p | %lu \n", it, (unsigned long) callFrame->argumentCount());
-    ++it;
+    --it;
     dataLogF("[CallerFrame]              | %10p | %p \n", it, callFrame->callerFrame());
-    ++it;
+    --it;
     dataLogF("[Callee]                   | %10p | %p \n", it, callFrame->callee());
-    ++it;
-    dataLogF("[ScopeChain]               | %10p | %p \n", it, callFrame->scope());
-    ++it;
+    --it;
+    // FIXME: Remove the next decrement when the ScopeChain slot is removed from the call header
+    --it;
 #if ENABLE(JIT)
     AbstractPC pc = callFrame->abstractReturnPC(callFrame->vm());
     if (pc.hasJITReturnAddress())
         dataLogF("[ReturnJITPC]              | %10p | %p \n", it, pc.jitReturnAddress().value());
 #endif
-    unsigned bytecodeOffset = 0;
-    int line = 0;
-    CodeBlock* callerCodeBlock = 0;
-    getCallerInfo(&callFrame->vm(), callFrame, bytecodeOffset, callerCodeBlock);
-    line = callerCodeBlock->lineNumberForBytecodeOffset(bytecodeOffset);
-    dataLogF("[ReturnVPC]                | %10p | %d (line %d)\n", it, bytecodeOffset, line);
-    ++it;
+
+    DumpRegisterFunctor functor(it);
+    callFrame->iterate(functor);
+
     dataLogF("[CodeBlock]                | %10p | %p \n", it, callFrame->codeBlock());
-    ++it;
+    --it;
     dataLogF("-----------------------------------------------------------------------------\n");
 
-    int registerCount = 0;
-
-    end = it + codeBlock->m_numVars;
+    end = it - codeBlock->m_numVars;
     if (it != end) {
         do {
             JSValue v = it->jsValue();
             int registerNumber = it - callFrame->registers();
-            String name = codeBlock->nameForRegister(registerNumber);
+            String name = codeBlock->nameForRegister(VirtualRegister(registerNumber));
             dataLogF("[r% 3d %14s]      | %10p | %-16s 0x%lld \n", registerNumber, name.ascii().data(), it, toCString(v).data(), (long long)JSValue::encode(v));
-            ++it;
-            ++registerCount;
+            --it;
         } while (it != end);
     }
     dataLogF("-----------------------------------------------------------------------------\n");
 
-    end = it + codeBlock->m_numCalleeRegisters - codeBlock->m_numVars;
+    end = it - codeBlock->m_numCalleeLocals + codeBlock->m_numVars;
     if (it != end) {
         do {
             JSValue v = (*it).jsValue();
-            dataLogF("[r% 3d]                     | %10p | %-16s 0x%lld \n", registerCount, it, toCString(v).data(), (long long)JSValue::encode(v));
-            ++it;
-            ++registerCount;
+            int registerNumber = it - callFrame->registers();
+            dataLogF("[r% 3d]                     | %10p | %-16s 0x%lld \n", registerNumber, it, toCString(v).data(), (long long)JSValue::encode(v));
+            --it;
         } while (it != end);
     }
     dataLogF("-----------------------------------------------------------------------------\n");
@@ -363,212 +437,28 @@ void Interpreter::dumpRegisters(CallFrame* callFrame)
 bool Interpreter::isOpcode(Opcode opcode)
 {
 #if ENABLE(COMPUTED_GOTO_OPCODES)
-#if !ENABLE(LLINT)
-    return static_cast<OpcodeID>(bitwise_cast<uintptr_t>(opcode)) <= op_end;
-#else
     return opcode != HashTraits<Opcode>::emptyValue()
         && !HashTraits<Opcode>::isDeletedValue(opcode)
         && m_opcodeIDTable.contains(opcode);
-#endif
 #else
     return opcode >= 0 && opcode <= op_end;
 #endif
 }
 
-NEVER_INLINE bool Interpreter::unwindCallFrame(CallFrame*& callFrame, JSValue exceptionValue, unsigned& bytecodeOffset, CodeBlock*& codeBlock)
-{
-    CodeBlock* oldCodeBlock = codeBlock;
-    JSScope* scope = callFrame->scope();
-
-    if (Debugger* debugger = callFrame->dynamicGlobalObject()->debugger()) {
-        DebuggerCallFrame debuggerCallFrame(callFrame, exceptionValue);
-        if (callFrame->callee())
-            debugger->returnEvent(debuggerCallFrame, codeBlock->ownerExecutable()->sourceID(), codeBlock->ownerExecutable()->lastLine(), 0);
-        else
-            debugger->didExecuteProgram(debuggerCallFrame, codeBlock->ownerExecutable()->sourceID(), codeBlock->ownerExecutable()->lastLine(), 0);
-    }
-
-    JSValue activation;
-    if (oldCodeBlock->codeType() == FunctionCode && oldCodeBlock->needsActivation()) {
-        activation = callFrame->uncheckedR(oldCodeBlock->activationRegister()).jsValue();
-        if (activation)
-            jsCast<JSActivation*>(activation)->tearOff(*scope->vm());
-    }
-
-    if (oldCodeBlock->codeType() == FunctionCode && oldCodeBlock->usesArguments()) {
-        if (JSValue arguments = callFrame->uncheckedR(unmodifiedArgumentsRegister(oldCodeBlock->argumentsRegister())).jsValue()) {
-            if (activation)
-                jsCast<Arguments*>(arguments)->didTearOffActivation(callFrame, jsCast<JSActivation*>(activation));
-            else
-                jsCast<Arguments*>(arguments)->tearOff(callFrame);
-        }
-    }
-
-    CallFrame* callerFrame = callFrame->callerFrame();
-    callFrame->vm().topCallFrame = callerFrame;
-    if (callerFrame->hasHostCallFrameFlag())
-        return false;
-    callFrame = getCallerInfo(&callFrame->vm(), callFrame, bytecodeOffset, codeBlock);
-    return true;
-}
-
-static void appendSourceToError(CallFrame* callFrame, ErrorInstance* exception, unsigned bytecodeOffset)
-{
-    exception->clearAppendSourceToMessage();
-
-    if (!callFrame->codeBlock()->hasExpressionInfo())
-        return;
-
-    int startOffset = 0;
-    int endOffset = 0;
-    int divotPoint = 0;
-    unsigned line = 0;
-    unsigned column = 0;
-
-    CodeBlock* codeBlock = callFrame->codeBlock();
-    codeBlock->expressionRangeForBytecodeOffset(bytecodeOffset, divotPoint, startOffset, endOffset, line, column);
-
-    int expressionStart = divotPoint - startOffset;
-    int expressionStop = divotPoint + endOffset;
-
-    const String& sourceString = codeBlock->source()->source();
-    if (!expressionStop || expressionStart > static_cast<int>(sourceString.length()))
-        return;
-
-    VM* vm = &callFrame->vm();
-    JSValue jsMessage = exception->getDirect(*vm, vm->propertyNames->message);
-    if (!jsMessage || !jsMessage.isString())
-        return;
-
-    String message = asString(jsMessage)->value(callFrame);
-
-    if (expressionStart < expressionStop)
-        message =  makeString(message, " (evaluating '", codeBlock->source()->getRange(expressionStart, expressionStop), "')");
-    else {
-        // No range information, so give a few characters of context
-        const StringImpl* data = sourceString.impl();
-        int dataLength = sourceString.length();
-        int start = expressionStart;
-        int stop = expressionStart;
-        // Get up to 20 characters of context to the left and right of the divot, clamping to the line.
-        // then strip whitespace.
-        while (start > 0 && (expressionStart - start < 20) && (*data)[start - 1] != '\n')
-            start--;
-        while (start < (expressionStart - 1) && isStrWhiteSpace((*data)[start]))
-            start++;
-        while (stop < dataLength && (stop - expressionStart < 20) && (*data)[stop] != '\n')
-            stop++;
-        while (stop > expressionStart && isStrWhiteSpace((*data)[stop - 1]))
-            stop--;
-        message = makeString(message, " (near '...", codeBlock->source()->getRange(start, stop), "...')");
-    }
-
-    exception->putDirect(*vm, vm->propertyNames->message, jsString(vm, message));
-}
-
-static unsigned getBytecodeOffsetForCallFrame(CallFrame* callFrame)
-{
-    callFrame = callFrame->removeHostCallFrameFlag();
-    CodeBlock* codeBlock = callFrame->codeBlock();
-    if (!codeBlock)
-        return 0;
-#if ENABLE(DFG_JIT)
-    if (codeBlock->getJITType() == JITCode::DFGJIT)
-        return codeBlock->codeOrigin(callFrame->codeOriginIndexForDFG()).bytecodeIndex;
-#endif
-    return callFrame->bytecodeOffsetForNonDFGCode();
-}
-
-static CallFrame* getCallerInfo(VM* vm, CallFrame* callFrame, unsigned& bytecodeOffset, CodeBlock*& caller)
+static StackFrameCodeType getStackFrameCodeType(StackVisitor& visitor)
 {
-    ASSERT_UNUSED(vm, vm);
-    bytecodeOffset = 0;
-    ASSERT(!callFrame->hasHostCallFrameFlag());
-    CallFrame* trueCallerFrame = callFrame->trueCallerFrame();
-    bool wasCalledByHost = callFrame->callerFrame()->hasHostCallFrameFlag();
-    ASSERT(!trueCallerFrame->hasHostCallFrameFlag());
-
-    if (trueCallerFrame == CallFrame::noCaller() || !trueCallerFrame || !trueCallerFrame->codeBlock()) {
-        caller = 0;
-        return trueCallerFrame;
-    }
-    
-    CodeBlock* callerCodeBlock = trueCallerFrame->codeBlock();
-    
-    if (!callFrame->hasReturnPC())
-        wasCalledByHost = true;
-
-    if (wasCalledByHost) {
-#if ENABLE(DFG_JIT)
-        if (callerCodeBlock && callerCodeBlock->getJITType() == JITCode::DFGJIT) {
-            unsigned codeOriginIndex = callFrame->callerFrame()->removeHostCallFrameFlag()->codeOriginIndexForDFG();
-            CodeOrigin origin = callerCodeBlock->codeOrigin(codeOriginIndex);
-            bytecodeOffset = origin.bytecodeIndex;
-            if (InlineCallFrame* inlineCallFrame = origin.inlineCallFrame)
-                callerCodeBlock = inlineCallFrame->baselineCodeBlock();
-        } else
-#endif
-            bytecodeOffset = trueCallerFrame->bytecodeOffsetForNonDFGCode();
-    } else {
-#if ENABLE(DFG_JIT)
-        if (callFrame->isInlineCallFrame()) {
-            InlineCallFrame* icf = callFrame->inlineCallFrame();
-            bytecodeOffset = icf->caller.bytecodeIndex;
-            if (InlineCallFrame* parentCallFrame = icf->caller.inlineCallFrame) {
-                FunctionExecutable* executable = static_cast<FunctionExecutable*>(parentCallFrame->executable.get());
-                CodeBlock* newCodeBlock = executable->baselineCodeBlockFor(parentCallFrame->isCall ? CodeForCall : CodeForConstruct);
-                ASSERT(newCodeBlock);
-                ASSERT(newCodeBlock->instructionCount() > bytecodeOffset);
-                callerCodeBlock = newCodeBlock;
-            }
-        } else if (callerCodeBlock && callerCodeBlock->getJITType() == JITCode::DFGJIT) {
-            CodeOrigin origin;
-            if (!callerCodeBlock->codeOriginForReturn(callFrame->returnPC(), origin)) {
-                // This should not be possible, but we're seeing cases where it does happen
-                // CallFrame already has robustness against bogus stack walks, so
-                // we'll extend that to here as well.
-                ASSERT_NOT_REACHED();
-                caller = 0;
-                return 0;
-            }
-            bytecodeOffset = origin.bytecodeIndex;
-            if (InlineCallFrame* icf = origin.inlineCallFrame) {
-                FunctionExecutable* executable = static_cast<FunctionExecutable*>(icf->executable.get());
-                CodeBlock* newCodeBlock = executable->baselineCodeBlockFor(icf->isCall ? CodeForCall : CodeForConstruct);
-                ASSERT(newCodeBlock);
-                ASSERT(newCodeBlock->instructionCount() > bytecodeOffset);
-                callerCodeBlock = newCodeBlock;
-            }
-        } else
-#endif
-        {
-            RELEASE_ASSERT(callerCodeBlock);
-            bytecodeOffset = callerCodeBlock->bytecodeOffset(trueCallerFrame, callFrame->returnPC());
-        }
-    }
-
-    RELEASE_ASSERT(callerCodeBlock);
-    caller = callerCodeBlock;
-    return trueCallerFrame;
-}
-
-static ALWAYS_INLINE const String getSourceURLFromCallFrame(CallFrame* callFrame)
-{
-    ASSERT(!callFrame->hasHostCallFrameFlag());
-    return callFrame->codeBlock()->ownerExecutable()->sourceURL();
-}
-
-static StackFrameCodeType getStackFrameCodeType(CallFrame* callFrame)
-{
-    ASSERT(!callFrame->hasHostCallFrameFlag());
-
-    switch (callFrame->codeBlock()->codeType()) {
-    case EvalCode:
+    switch (visitor->codeType()) {
+    case StackVisitor::Frame::Eval:
         return StackFrameEvalCode;
-    case FunctionCode:
+    case StackVisitor::Frame::Module:
+        return StackFrameModuleCode;
+    case StackVisitor::Frame::Function:
         return StackFrameFunctionCode;
-    case GlobalCode:
+    case StackVisitor::Frame::Global:
         return StackFrameGlobalCode;
+    case StackVisitor::Frame::Native:
+        ASSERT_NOT_REACHED();
+        return StackFrameNativeCode;
     }
     RELEASE_ASSERT_NOT_REACHED();
     return StackFrameGlobalCode;
@@ -591,6 +481,9 @@ void StackFrame::computeLineAndColumn(unsigned& line, unsigned& column)
 
     line = divotLine + lineOffset;
     column = divotColumn + (divotLine ? 1 : firstLineColumnOffset);
+
+    if (executable->hasOverrideLineNumber())
+        line = executable->overrideLineNumber();
 }
 
 void StackFrame::expressionInfo(int& divot, int& startOffset, int& endOffset, unsigned& line, unsigned& column)
@@ -623,147 +516,286 @@ String StackFrame::toString(CallFrame* callFrame)
     return traceBuild.toString().impl();
 }
 
-void Interpreter::getStackTrace(VM* vm, Vector<StackFrame>& results, size_t maxStackSize)
+static inline bool isWebAssemblyExecutable(ExecutableBase* executable)
 {
-    CallFrame* callFrame = vm->topCallFrame->removeHostCallFrameFlag();
-    if (!callFrame || callFrame == CallFrame::noCaller()) 
-        return;
-    unsigned bytecodeOffset = getBytecodeOffsetForCallFrame(callFrame);
-    callFrame = callFrame->trueCallFrameFromVMCode();
-    if (!callFrame)
-        return;
-    CodeBlock* callerCodeBlock = callFrame->codeBlock();
-
-    while (callFrame && callFrame != CallFrame::noCaller() && maxStackSize--) {
-        String sourceURL;
-        if (callerCodeBlock) {
-            sourceURL = getSourceURLFromCallFrame(callFrame);
-            StackFrame s = {
-                Strong<JSObject>(*vm, callFrame->callee()),
-                getStackFrameCodeType(callFrame),
-                Strong<ExecutableBase>(*vm, callerCodeBlock->ownerExecutable()),
-                Strong<UnlinkedCodeBlock>(*vm, callerCodeBlock->unlinkedCodeBlock()),
-                callerCodeBlock->source(),
-                callerCodeBlock->ownerExecutable()->lineNo(),
-                callerCodeBlock->firstLineColumnOffset(),
-                callerCodeBlock->sourceOffset(),
-                bytecodeOffset,
-                sourceURL
-            };
-
-            results.append(s);
-        } else {
-            StackFrame s = { Strong<JSObject>(*vm, callFrame->callee()), StackFrameNativeCode, Strong<ExecutableBase>(), Strong<UnlinkedCodeBlock>(), 0, 0, 0, 0, 0, String()};
-            results.append(s);
-        }
-        callFrame = getCallerInfo(vm, callFrame, bytecodeOffset, callerCodeBlock);
-    }
+#if !ENABLE(WEBASSEMBLY)
+    UNUSED_PARAM(executable);
+    return false;
+#else
+    return executable->isWebAssemblyExecutable();
+#endif
 }
 
-void Interpreter::addStackTraceIfNecessary(CallFrame* callFrame, JSValue error)
-{
-    VM* vm = &callFrame->vm();
-    ASSERT(callFrame == vm->topCallFrame || callFrame == callFrame->lexicalGlobalObject()->globalExec() || callFrame == callFrame->dynamicGlobalObject()->globalExec());
-
-    if (error.isObject()) {
-        if (asObject(error)->hasProperty(callFrame, vm->propertyNames->stack))
-            return;
+class GetStackTraceFunctor {
+public:
+    GetStackTraceFunctor(VM& vm, Vector<StackFrame>& results, size_t remainingCapacity)
+        : m_vm(vm)
+        , m_results(results)
+        , m_remainingCapacityForFrameCapture(remainingCapacity)
+    {
     }
+
+    StackVisitor::Status operator()(StackVisitor& visitor)
+    {
+        VM& vm = m_vm;
+        if (m_remainingCapacityForFrameCapture) {
+            if (visitor->isJSFrame()
+                && !isWebAssemblyExecutable(visitor->codeBlock()->ownerExecutable())
+                && !visitor->codeBlock()->unlinkedCodeBlock()->isBuiltinFunction()) {
+                CodeBlock* codeBlock = visitor->codeBlock();
+                StackFrame s = {
+                    Strong<JSObject>(vm, visitor->callee()),
+                    getStackFrameCodeType(visitor),
+                    Strong<ScriptExecutable>(vm, codeBlock->ownerScriptExecutable()),
+                    Strong<UnlinkedCodeBlock>(vm, codeBlock->unlinkedCodeBlock()),
+                    codeBlock->source(),
+                    codeBlock->ownerScriptExecutable()->firstLine(),
+                    codeBlock->firstLineColumnOffset(),
+                    codeBlock->sourceOffset(),
+                    visitor->bytecodeOffset(),
+                    visitor->sourceURL()
+                };
+                m_results.append(s);
+            } else {
+                StackFrame s = { Strong<JSObject>(vm, visitor->callee()), StackFrameNativeCode, Strong<ScriptExecutable>(), Strong<UnlinkedCodeBlock>(), 0, 0, 0, 0, 0, String()};
+                m_results.append(s);
+            }
     
-    Vector<StackFrame> stackTrace;
-    getStackTrace(&callFrame->vm(), stackTrace);
-    vm->exceptionStack() = RefCountedArray<StackFrame>(stackTrace);
-    if (stackTrace.isEmpty() || !error.isObject())
+            m_remainingCapacityForFrameCapture--;
+            return StackVisitor::Continue;
+        }
+        return StackVisitor::Done;
+    }
+
+private:
+    VM& m_vm;
+    Vector<StackFrame>& m_results;
+    size_t m_remainingCapacityForFrameCapture;
+};
+
+void Interpreter::getStackTrace(Vector<StackFrame>& results, size_t maxStackSize)
+{
+    VM& vm = m_vm;
+    CallFrame* callFrame = vm.topCallFrame;
+    if (!callFrame)
         return;
 
-    JSObject* errorObject = asObject(error);
-    JSGlobalObject* globalObject = 0;
-    if (isTerminatedExecutionException(error))
-        globalObject = vm->dynamicGlobalObject;
-    else
-        globalObject = errorObject->globalObject();
+    GetStackTraceFunctor functor(vm, results, maxStackSize);
+    callFrame->iterate(functor);
+}
 
+JSString* Interpreter::stackTraceAsString(ExecState* exec, Vector<StackFrame> stackTrace)
+{
     // FIXME: JSStringJoiner could be more efficient than StringBuilder here.
     StringBuilder builder;
     for (unsigned i = 0; i < stackTrace.size(); i++) {
-        builder.append(String(stackTrace[i].toString(globalObject->globalExec()).impl()));
+        builder.append(String(stackTrace[i].toString(exec)));
         if (i != stackTrace.size() - 1)
             builder.append('\n');
     }
-
-    errorObject->putDirect(*vm, vm->propertyNames->stack, jsString(vm, builder.toString()), ReadOnly | DontDelete);
+    return jsString(&exec->vm(), builder.toString());
 }
 
-NEVER_INLINE HandlerInfo* Interpreter::throwException(CallFrame*& callFrame, JSValue& exceptionValue, unsigned bytecodeOffset)
+ALWAYS_INLINE static HandlerInfo* findExceptionHandler(StackVisitor& visitor, CodeBlock* codeBlock, CodeBlock::RequiredHandler requiredHandler)
 {
-    CodeBlock* codeBlock = callFrame->codeBlock();
-    bool isTermination = false;
+    ASSERT(codeBlock);
+#if ENABLE(DFG_JIT)
+    ASSERT(!visitor->isInlinedFrame());
+#endif
 
-    ASSERT(!exceptionValue.isEmpty());
-    ASSERT(!exceptionValue.isCell() || exceptionValue.asCell());
-    // This shouldn't be possible (hence the assertions), but we're already in the slowest of
-    // slow cases, so let's harden against it anyway to be safe.
-    if (exceptionValue.isEmpty() || (exceptionValue.isCell() && !exceptionValue.asCell()))
-        exceptionValue = jsNull();
+    CallFrame* callFrame = visitor->callFrame();
+    unsigned exceptionHandlerIndex;
+    if (JITCode::isOptimizingJIT(codeBlock->jitType()))
+        exceptionHandlerIndex = callFrame->callSiteIndex().bits();
+    else
+        exceptionHandlerIndex = callFrame->bytecodeOffset();
+
+    return codeBlock->handlerForIndex(exceptionHandlerIndex, requiredHandler);
+}
+
+class GetCatchHandlerFunctor {
+public:
+    GetCatchHandlerFunctor()
+        : m_handler(0)
+    {
+    }
+
+    HandlerInfo* handler() { return m_handler; }
 
-    // Set up the exception object
-    if (exceptionValue.isObject()) {
-        JSObject* exception = asObject(exceptionValue);
+    StackVisitor::Status operator()(StackVisitor& visitor)
+    {
+        visitor.unwindToMachineCodeBlockFrame();
+
+        CodeBlock* codeBlock = visitor->codeBlock();
+        if (!codeBlock)
+            return StackVisitor::Continue;
+
+        m_handler = findExceptionHandler(visitor, codeBlock, CodeBlock::RequiredHandler::CatchHandler);
+        if (m_handler)
+            return StackVisitor::Done;
+
+        return StackVisitor::Continue;
+    }
+
+private:
+    HandlerInfo* m_handler;
+};
+
+ALWAYS_INLINE static void notifyDebuggerOfUnwinding(CallFrame* callFrame)
+{
+    if (Debugger* debugger = callFrame->vmEntryGlobalObject()->debugger()) {
+        SuspendExceptionScope scope(&callFrame->vm());
+        if (jsDynamicCast<JSFunction*>(callFrame->callee()))
+            debugger->returnEvent(callFrame);
+        else
+            debugger->didExecuteProgram(callFrame);
+        ASSERT(!callFrame->hadException());
+    }
+}
 
-        if (exception->isErrorInstance() && static_cast<ErrorInstance*>(exception)->appendSourceToMessage())
-            appendSourceToError(callFrame, static_cast<ErrorInstance*>(exception), bytecodeOffset);
+class UnwindFunctor {
+public:
+    UnwindFunctor(CallFrame*& callFrame, bool isTermination, CodeBlock*& codeBlock, HandlerInfo*& handler)
+        : m_callFrame(callFrame)
+        , m_isTermination(isTermination)
+        , m_codeBlock(codeBlock)
+        , m_handler(handler)
+    {
+    }
 
-        if (!hasErrorInfo(callFrame, exception)) {
-            // FIXME: should only really be adding these properties to VM generated exceptions,
-            // but the inspector currently requires these for all thrown objects.
-            addErrorInfo(callFrame, exception, codeBlock->lineNumberForBytecodeOffset(bytecodeOffset), codeBlock->ownerExecutable()->source());
+    StackVisitor::Status operator()(StackVisitor& visitor)
+    {
+        visitor.unwindToMachineCodeBlockFrame();
+        VM& vm = m_callFrame->vm();
+        m_callFrame = visitor->callFrame();
+        m_codeBlock = visitor->codeBlock();
+
+        m_handler = nullptr;
+        if (!m_isTermination) {
+            if (m_codeBlock && !isWebAssemblyExecutable(m_codeBlock->ownerExecutable()))
+                m_handler = findExceptionHandler(visitor, m_codeBlock, CodeBlock::RequiredHandler::AnyHandler);
         }
 
-        isTermination = isTerminatedExecutionException(exception);
-    } else {
-        if (!callFrame->vm().exceptionStack().size()) {
-            Vector<StackFrame> stack;
-            Interpreter::getStackTrace(&callFrame->vm(), stack);
-            callFrame->vm().exceptionStack() = RefCountedArray<StackFrame>(stack);
+        if (m_handler)
+            return StackVisitor::Done;
+
+        notifyDebuggerOfUnwinding(m_callFrame);
+
+        bool shouldStopUnwinding = visitor->callerIsVMEntryFrame();
+        if (shouldStopUnwinding) {
+            if (LegacyProfiler* profiler = vm.enabledProfiler())
+                profiler->exceptionUnwind(m_callFrame);
+
+            copyCalleeSavesToVMCalleeSavesBuffer(visitor);
+
+            return StackVisitor::Done;
         }
-    }
 
-    if (Debugger* debugger = callFrame->dynamicGlobalObject()->debugger()) {
-        DebuggerCallFrame debuggerCallFrame(callFrame, exceptionValue);
-        bool hasHandler = codeBlock->handlerForBytecodeOffset(bytecodeOffset);
-        debugger->exception(debuggerCallFrame, codeBlock->ownerExecutable()->sourceID(), codeBlock->lineNumberForBytecodeOffset(bytecodeOffset), 0, hasHandler);
+        copyCalleeSavesToVMCalleeSavesBuffer(visitor);
+
+        return StackVisitor::Continue;
     }
 
-    // Calculate an exception handler vPC, unwinding call frames as necessary.
-    HandlerInfo* handler = 0;
-    while (isTermination || !(handler = codeBlock->handlerForBytecodeOffset(bytecodeOffset))) {
-        if (!unwindCallFrame(callFrame, exceptionValue, bytecodeOffset, codeBlock)) {
-            if (LegacyProfiler* profiler = callFrame->vm().enabledProfiler())
-                profiler->exceptionUnwind(callFrame);
-            return 0;
+private:
+    void copyCalleeSavesToVMCalleeSavesBuffer(StackVisitor& visitor)
+    {
+#if ENABLE(JIT) && NUMBER_OF_CALLEE_SAVES_REGISTERS > 0
+
+        if (!visitor->isJSFrame())
+            return;
+
+#if ENABLE(DFG_JIT)
+        if (visitor->inlineCallFrame())
+            return;
+#endif
+        RegisterAtOffsetList* currentCalleeSaves = m_codeBlock ? m_codeBlock->calleeSaveRegisters() : nullptr;
+
+        if (!currentCalleeSaves)
+            return;
+
+        VM& vm = m_callFrame->vm();
+        RegisterAtOffsetList* allCalleeSaves = vm.getAllCalleeSaveRegisterOffsets();
+        RegisterSet dontCopyRegisters = RegisterSet::stackRegisters();
+        intptr_t* frame = reinterpret_cast<intptr_t*>(m_callFrame->registers());
+
+        unsigned registerCount = currentCalleeSaves->size();
+        for (unsigned i = 0; i < registerCount; i++) {
+            RegisterAtOffset currentEntry = currentCalleeSaves->at(i);
+            if (dontCopyRegisters.get(currentEntry.reg()))
+                continue;
+            RegisterAtOffset* vmCalleeSavesEntry = allCalleeSaves->find(currentEntry.reg());
+            
+            vm.calleeSaveRegistersBuffer[vmCalleeSavesEntry->offsetAsIndex()] = *(frame + currentEntry.offsetAsIndex());
         }
+#else
+        UNUSED_PARAM(visitor);
+#endif
     }
 
-    if (LegacyProfiler* profiler = callFrame->vm().enabledProfiler())
-        profiler->exceptionUnwind(callFrame);
-
-    // Unwind the scope chain within the exception handler's call frame.
-    JSScope* scope = callFrame->scope();
-    int scopeDelta = 0;
-    if (!codeBlock->needsFullScopeChain() || codeBlock->codeType() != FunctionCode 
-        || callFrame->uncheckedR(codeBlock->activationRegister()).jsValue()) {
-        int currentDepth = depth(codeBlock, scope);
-        int targetDepth = handler->scopeDepth;
-        scopeDelta = currentDepth - targetDepth;
-        RELEASE_ASSERT(scopeDelta >= 0);
+    CallFrame*& m_callFrame;
+    bool m_isTermination;
+    CodeBlock*& m_codeBlock;
+    HandlerInfo*& m_handler;
+};
+
+NEVER_INLINE HandlerInfo* Interpreter::unwind(VM& vm, CallFrame*& callFrame, Exception* exception, UnwindStart unwindStart)
+{
+    if (unwindStart == UnwindFromCallerFrame) {
+        if (callFrame->callerFrameOrVMEntryFrame() == vm.topVMEntryFrame)
+            return nullptr;
+
+        callFrame = callFrame->callerFrame();
+        vm.topCallFrame = callFrame;
     }
-    while (scopeDelta--)
-        scope = scope->next();
-    callFrame->setScope(scope);
+
+    CodeBlock* codeBlock = callFrame->codeBlock();
+
+    JSValue exceptionValue = exception->value();
+    ASSERT(!exceptionValue.isEmpty());
+    ASSERT(!exceptionValue.isCell() || exceptionValue.asCell());
+    // This shouldn't be possible (hence the assertions), but we're already in the slowest of
+    // slow cases, so let's harden against it anyway to be safe.
+    if (exceptionValue.isEmpty() || (exceptionValue.isCell() && !exceptionValue.asCell()))
+        exceptionValue = jsNull();
+
+    ASSERT(vm.exception() && vm.exception()->stack().size());
+
+    // Calculate an exception handler vPC, unwinding call frames as necessary.
+    HandlerInfo* handler = nullptr;
+    UnwindFunctor functor(callFrame, isTerminatedExecutionException(exception), codeBlock, handler);
+    callFrame->iterate(functor);
+    if (!handler)
+        return nullptr;
 
     return handler;
 }
 
+void Interpreter::notifyDebuggerOfExceptionToBeThrown(CallFrame* callFrame, Exception* exception)
+{
+    Debugger* debugger = callFrame->vmEntryGlobalObject()->debugger();
+    if (debugger && debugger->needsExceptionCallbacks() && !exception->didNotifyInspectorOfThrow()) {
+        // This code assumes that if the debugger is enabled then there is no inlining.
+        // If that assumption turns out to be false then we'll ignore the inlined call
+        // frames.
+        // https://bugs.webkit.org/show_bug.cgi?id=121754
+
+        bool hasCatchHandler;
+        bool isTermination = isTerminatedExecutionException(exception);
+        if (isTermination)
+            hasCatchHandler = false;
+        else {
+            GetCatchHandlerFunctor functor;
+            callFrame->iterate(functor);
+            HandlerInfo* handler = functor.handler();
+            ASSERT(!handler || handler->isCatchHandler());
+            hasCatchHandler = !!handler;
+        }
+
+        debugger->exception(callFrame, exception->value(), hasCatchHandler);
+    }
+    exception->setDidNotifyInspectorOfThrow();
+}
+
 static inline JSValue checkedReturn(JSValue returnValue)
 {
     ASSERT(returnValue);
@@ -794,28 +826,26 @@ private:
 JSValue Interpreter::execute(ProgramExecutable* program, CallFrame* callFrame, JSObject* thisObj)
 {
     SamplingScope samplingScope(this);
-    
-    JSScope* scope = callFrame->scope();
+
+    JSScope* scope = thisObj->globalObject()->globalScope();
     VM& vm = *scope->vm();
 
-    ASSERT(isValidThisObject(thisObj, callFrame));
-    ASSERT(!vm.exception);
+    ASSERT(!vm.exception());
     ASSERT(!vm.isCollectorBusy());
+    RELEASE_ASSERT(vm.currentThreadIsHoldingAPILock());
     if (vm.isCollectorBusy())
         return jsNull();
 
-    StackStats::CheckPoint stackCheckPoint;
-    const VMStackBounds vmStackBounds(vm, wtfThreadData().stack());
-    if (!vmStackBounds.isSafeToRecurse())
+    if (!vm.isSafeToRecurse())
         return checkedReturn(throwStackOverflowError(callFrame));
 
     // First check if the "program" is actually just a JSON object. If so,
     // we'll handle the JSON object here. Else, we'll handle real JS code
     // below at failedJSONP.
-    DynamicGlobalObjectScope globalObjectScope(vm, scope->globalObject());
+
     Vector<JSONPData> JSONPData;
     bool parseResult;
-    const String programSource = program->source().toString();
+    StringView programSource = program->source().view();
     if (programSource.isNull())
         return jsUndefined();
     if (programSource.is8Bit()) {
@@ -834,12 +864,9 @@ JSValue Interpreter::execute(ProgramExecutable* program, CallFrame* callFrame, J
             JSONPPath.swap(JSONPData[entry].m_path);
             JSValue JSONPValue = JSONPData[entry].m_value.get();
             if (JSONPPath.size() == 1 && JSONPPath[0].m_type == JSONPPathEntryTypeDeclare) {
-                if (globalObject->hasProperty(callFrame, JSONPPath[0].m_pathEntryName)) {
-                    PutPropertySlot slot;
-                    globalObject->methodTable()->put(globalObject, callFrame, JSONPPath[0].m_pathEntryName, JSONPValue, slot);
-                } else
-                    globalObject->methodTable()->putDirectVirtual(globalObject, callFrame, JSONPPath[0].m_pathEntryName, JSONPValue, DontEnum | DontDelete);
-                // var declarations return undefined
+                globalObject->addVar(callFrame, JSONPPath[0].m_pathEntryName);
+                PutPropertySlot slot(globalObject);
+                globalObject->methodTable()->put(globalObject, callFrame, JSONPPath[0].m_pathEntryName, JSONPValue, slot);
                 result = jsUndefined();
                 continue;
             }
@@ -849,10 +876,10 @@ JSValue Interpreter::execute(ProgramExecutable* program, CallFrame* callFrame, J
                 switch (JSONPPath[i].m_type) {
                 case JSONPPathEntryTypeDot: {
                     if (i == 0) {
-                        PropertySlot slot(globalObject);
+                        PropertySlot slot(globalObject, PropertySlot::InternalMethodType::Get);
                         if (!globalObject->getPropertySlot(callFrame, JSONPPath[i].m_pathEntryName, slot)) {
                             if (entry)
-                                return throwError(callFrame, createUndefinedVariableError(globalObject->globalExec(), JSONPPath[i].m_pathEntryName));
+                                return callFrame->vm().throwException(callFrame, createUndefinedVariableError(callFrame, JSONPPath[i].m_pathEntryName));
                             goto failedJSONP;
                         }
                         baseObject = slot.getValue(callFrame, JSONPPath[i].m_pathEntryName);
@@ -873,7 +900,7 @@ JSValue Interpreter::execute(ProgramExecutable* program, CallFrame* callFrame, J
                     return jsUndefined();
                 }
             }
-            PutPropertySlot slot;
+            PutPropertySlot slot(baseObject);
             switch (JSONPPath.last().m_type) {
             case JSONPPathEntryTypeCall: {
                 JSValue function = baseObject.get(callFrame, JSONPPath.last().m_pathEntryName);
@@ -882,7 +909,7 @@ JSValue Interpreter::execute(ProgramExecutable* program, CallFrame* callFrame, J
                 CallData callData;
                 CallType callType = getCallData(function, callData);
                 if (callType == CallTypeNone)
-                    return throwError(callFrame, createNotAFunctionError(callFrame, function));
+                    return callFrame->vm().throwException(callFrame, createNotAFunctionError(callFrame, function));
                 MarkedArgumentBuffer jsonArg;
                 jsonArg.append(JSONPValue);
                 JSValue thisValue = JSONPPath.size() == 1 ? jsUndefined(): baseObject;
@@ -915,47 +942,37 @@ failedJSONP:
     // If we get here, then we have already proven that the script is not a JSON
     // object.
 
+    VMEntryScope entryScope(vm, scope->globalObject());
+
     // Compile source to bytecode if necessary:
     if (JSObject* error = program->initializeGlobalProperties(vm, callFrame, scope))
-        return checkedReturn(throwError(callFrame, error));
+        return checkedReturn(callFrame->vm().throwException(callFrame, error));
 
-    if (JSObject* error = program->compile(callFrame, scope))
-        return checkedReturn(throwError(callFrame, error));
+    if (JSObject* error = program->prepareForExecution(callFrame, nullptr, scope, CodeForCall))
+        return checkedReturn(callFrame->vm().throwException(callFrame, error));
 
-    ProgramCodeBlock* codeBlock = &program->generatedBytecode();
+    ProgramCodeBlock* codeBlock = program->codeBlock();
 
-    if (UNLIKELY(vm.watchdog.didFire(callFrame)))
+    if (UNLIKELY(vm.shouldTriggerTermination(callFrame)))
         return throwTerminatedExecutionException(callFrame);
 
-    // Push the call frame for this invocation:
     ASSERT(codeBlock->numParameters() == 1); // 1 parameter for 'this'.
-    CallFrame* newCallFrame = m_stack.pushFrame(callFrame, codeBlock, scope, 1, 0);
-    if (UNLIKELY(!newCallFrame))
-        return checkedReturn(throwStackOverflowError(callFrame));
 
-    // Set the arguments for the callee:
-    newCallFrame->setThisValue(thisObj);
+    ProtoCallFrame protoCallFrame;
+    protoCallFrame.init(codeBlock, JSCallee::create(vm, scope->globalObject(), scope), thisObj, 1);
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
-        profiler->willExecute(callFrame, program->sourceURL(), program->lineNo());
+        profiler->willExecute(callFrame, program->sourceURL(), program->firstLine(), program->startColumn());
 
     // Execute the code:
     JSValue result;
     {
         SamplingTool::CallRecord callRecord(m_sampler.get());
-        Watchdog::Scope watchdogScope(vm.watchdog);
-
-#if ENABLE(LLINT_C_LOOP)
-        result = LLInt::CLoop::execute(newCallFrame, llint_program_prologue);
-#elif ENABLE(JIT)
-        result = program->generatedJITCode().execute(&m_stack, newCallFrame, &vm);
-#endif // ENABLE(JIT)
+        result = program->generatedJITCode()->execute(&vm, &protoCallFrame);
     }
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
-        profiler->didExecute(callFrame, program->sourceURL(), program->lineNo());
-
-    m_stack.popFrame(newCallFrame);
+        profiler->didExecute(callFrame, program->sourceURL(), program->firstLine(), program->startColumn());
 
     return checkedReturn(result);
 }
@@ -963,52 +980,47 @@ failedJSONP:
 JSValue Interpreter::executeCall(CallFrame* callFrame, JSObject* function, CallType callType, const CallData& callData, JSValue thisValue, const ArgList& args)
 {
     VM& vm = callFrame->vm();
-    ASSERT(isValidThisObject(thisValue, callFrame));
     ASSERT(!callFrame->hadException());
     ASSERT(!vm.isCollectorBusy());
     if (vm.isCollectorBusy())
         return jsNull();
 
-    StackStats::CheckPoint stackCheckPoint;
-    const VMStackBounds vmStackBounds(vm, wtfThreadData().stack());
-    if (!vmStackBounds.isSafeToRecurse())
-        return checkedReturn(throwStackOverflowError(callFrame));
-
     bool isJSCall = (callType == CallTypeJS);
-    JSScope* scope;
+    JSScope* scope = nullptr;
     CodeBlock* newCodeBlock;
     size_t argsCount = 1 + args.size(); // implicit "this" parameter
 
-    if (isJSCall)
+    JSGlobalObject* globalObject;
+
+    if (isJSCall) {
         scope = callData.js.scope;
-    else {
+        globalObject = scope->globalObject();
+    } else {
         ASSERT(callType == CallTypeHost);
-        scope = callFrame->scope();
+        globalObject = function->globalObject();
     }
-    DynamicGlobalObjectScope globalObjectScope(vm, scope->globalObject());
+
+    VMEntryScope entryScope(vm, globalObject);
+    if (!vm.isSafeToRecurse())
+        return checkedReturn(throwStackOverflowError(callFrame));
 
     if (isJSCall) {
         // Compile the callee:
-        JSObject* compileError = callData.js.functionExecutable->compileForCall(callFrame, scope);
+        JSObject* compileError = callData.js.functionExecutable->prepareForExecution(callFrame, jsCast<JSFunction*>(function), scope, CodeForCall);
         if (UNLIKELY(!!compileError)) {
-            return checkedReturn(throwError(callFrame, compileError));
+            return checkedReturn(callFrame->vm().throwException(callFrame, compileError));
         }
-        newCodeBlock = &callData.js.functionExecutable->generatedBytecodeForCall();
+        newCodeBlock = callData.js.functionExecutable->codeBlockForCall();
         ASSERT(!!newCodeBlock);
+        newCodeBlock->m_shouldAlwaysBeInlined = false;
     } else
         newCodeBlock = 0;
 
-    if (UNLIKELY(vm.watchdog.didFire(callFrame)))
+    if (UNLIKELY(vm.shouldTriggerTermination(callFrame)))
         return throwTerminatedExecutionException(callFrame);
 
-    CallFrame* newCallFrame = m_stack.pushFrame(callFrame, newCodeBlock, scope, argsCount, function);
-    if (UNLIKELY(!newCallFrame))
-        return checkedReturn(throwStackOverflowError(callFrame));
-
-    // Set the arguments for the callee:
-    newCallFrame->setThisValue(thisValue);
-    for (size_t i = 0; i < args.size(); ++i)
-        newCallFrame->setArgument(i, args.at(i));
+    ProtoCallFrame protoCallFrame;
+    protoCallFrame.init(newCodeBlock, function, thisValue, argsCount, args.data());
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
         profiler->willExecute(callFrame, function);
@@ -1016,27 +1028,24 @@ JSValue Interpreter::executeCall(CallFrame* callFrame, JSObject* function, CallT
     JSValue result;
     {
         SamplingTool::CallRecord callRecord(m_sampler.get(), !isJSCall);
-        Watchdog::Scope watchdogScope(vm.watchdog);
 
         // Execute the code:
-        if (isJSCall) {
-#if ENABLE(LLINT_C_LOOP)
-            result = LLInt::CLoop::execute(newCallFrame, llint_function_for_call_prologue);
-#elif ENABLE(JIT)
-            result = callData.js.functionExecutable->generatedJITCodeForCall().execute(&m_stack, newCallFrame, &vm);
-#endif // ENABLE(JIT)
-        } else
-            result = JSValue::decode(callData.native.function(newCallFrame));
+        if (isJSCall)
+            result = callData.js.functionExecutable->generatedJITCodeForCall()->execute(&vm, &protoCallFrame);
+        else {
+            result = JSValue::decode(vmEntryToNative(reinterpret_cast<void*>(callData.native.function), &vm, &protoCallFrame));
+            if (callFrame->hadException())
+                result = jsNull();
+        }
     }
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
         profiler->didExecute(callFrame, function);
 
-    m_stack.popFrame(newCallFrame);
     return checkedReturn(result);
 }
 
-JSObject* Interpreter::executeConstruct(CallFrame* callFrame, JSObject* constructor, ConstructType constructType, const ConstructData& constructData, const ArgList& args)
+JSObject* Interpreter::executeConstruct(CallFrame* callFrame, JSObject* constructor, ConstructType constructType, const ConstructData& constructData, const ArgList& args, JSValue newTarget)
 {
     VM& vm = callFrame->vm();
     ASSERT(!callFrame->hadException());
@@ -1046,47 +1055,42 @@ JSObject* Interpreter::executeConstruct(CallFrame* callFrame, JSObject* construc
     if (vm.isCollectorBusy())
         return checkedReturn(throwStackOverflowError(callFrame));
 
-    StackStats::CheckPoint stackCheckPoint;
-    const VMStackBounds vmStackBounds(vm, wtfThreadData().stack());
-    if (!vmStackBounds.isSafeToRecurse())
-        return checkedReturn(throwStackOverflowError(callFrame));
-
     bool isJSConstruct = (constructType == ConstructTypeJS);
-    JSScope* scope;
+    JSScope* scope = nullptr;
     CodeBlock* newCodeBlock;
     size_t argsCount = 1 + args.size(); // implicit "this" parameter
 
-    if (isJSConstruct)
+    JSGlobalObject* globalObject;
+
+    if (isJSConstruct) {
         scope = constructData.js.scope;
-    else {
+        globalObject = scope->globalObject();
+    } else {
         ASSERT(constructType == ConstructTypeHost);
-        scope = callFrame->scope();
+        globalObject = constructor->globalObject();
     }
 
-    DynamicGlobalObjectScope globalObjectScope(vm, scope->globalObject());
+    VMEntryScope entryScope(vm, globalObject);
+    if (!vm.isSafeToRecurse())
+        return checkedReturn(throwStackOverflowError(callFrame));
 
     if (isJSConstruct) {
         // Compile the callee:
-        JSObject* compileError = constructData.js.functionExecutable->compileForConstruct(callFrame, scope);
+        JSObject* compileError = constructData.js.functionExecutable->prepareForExecution(callFrame, jsCast<JSFunction*>(constructor), scope, CodeForConstruct);
         if (UNLIKELY(!!compileError)) {
-            return checkedReturn(throwError(callFrame, compileError));
+            return checkedReturn(callFrame->vm().throwException(callFrame, compileError));
         }
-        newCodeBlock = &constructData.js.functionExecutable->generatedBytecodeForConstruct();
+        newCodeBlock = constructData.js.functionExecutable->codeBlockForConstruct();
         ASSERT(!!newCodeBlock);
+        newCodeBlock->m_shouldAlwaysBeInlined = false;
     } else
         newCodeBlock = 0;
 
-    if (UNLIKELY(vm.watchdog.didFire(callFrame)))
+    if (UNLIKELY(vm.shouldTriggerTermination(callFrame)))
         return throwTerminatedExecutionException(callFrame);
 
-    CallFrame* newCallFrame = m_stack.pushFrame(callFrame, newCodeBlock, scope, argsCount, constructor);
-    if (UNLIKELY(!newCallFrame))
-        return checkedReturn(throwStackOverflowError(callFrame));
-
-    // Set the arguments for the callee:
-    newCallFrame->setThisValue(jsUndefined());
-    for (size_t i = 0; i < args.size(); ++i)
-        newCallFrame->setArgument(i, args.at(i));
+    ProtoCallFrame protoCallFrame;
+    protoCallFrame.init(newCodeBlock, constructor, newTarget, argsCount, args.data());
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
         profiler->willExecute(callFrame, constructor);
@@ -1094,68 +1098,49 @@ JSObject* Interpreter::executeConstruct(CallFrame* callFrame, JSObject* construc
     JSValue result;
     {
         SamplingTool::CallRecord callRecord(m_sampler.get(), !isJSConstruct);
-        Watchdog::Scope watchdogScope(vm.watchdog);
 
         // Execute the code.
-        if (isJSConstruct) {
-#if ENABLE(LLINT_C_LOOP)
-            result = LLInt::CLoop::execute(newCallFrame, llint_function_for_construct_prologue);
-#elif ENABLE(JIT)
-            result = constructData.js.functionExecutable->generatedJITCodeForConstruct().execute(&m_stack, newCallFrame, &vm);
-#endif // ENABLE(JIT)
-        } else
-            result = JSValue::decode(constructData.native.function(newCallFrame));
+        if (isJSConstruct)
+            result = constructData.js.functionExecutable->generatedJITCodeForConstruct()->execute(&vm, &protoCallFrame);
+        else {
+            result = JSValue::decode(vmEntryToNative(reinterpret_cast<void*>(constructData.native.function), &vm, &protoCallFrame));
+
+            if (!callFrame->hadException())
+                RELEASE_ASSERT(result.isObject());
+        }
     }
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
         profiler->didExecute(callFrame, constructor);
 
-    m_stack.popFrame(newCallFrame);
-
     if (callFrame->hadException())
         return 0;
     ASSERT(result.isObject());
     return checkedReturn(asObject(result));
 }
 
-CallFrameClosure Interpreter::prepareForRepeatCall(FunctionExecutable* functionExecutable, CallFrame* callFrame, JSFunction* function, int argumentCountIncludingThis, JSScope* scope)
+CallFrameClosure Interpreter::prepareForRepeatCall(FunctionExecutable* functionExecutable, CallFrame* callFrame, ProtoCallFrame* protoCallFrame, JSFunction* function, int argumentCountIncludingThis, JSScope* scope, JSValue* args)
 {
     VM& vm = *scope->vm();
-    ASSERT(!vm.exception);
+    ASSERT(!vm.exception());
     
     if (vm.isCollectorBusy())
         return CallFrameClosure();
 
-    StackStats::CheckPoint stackCheckPoint;
-    const VMStackBounds vmStackBounds(vm, wtfThreadData().stack());
-    if (!vmStackBounds.isSafeToRecurse()) {
-        throwStackOverflowError(callFrame);
-        return CallFrameClosure();
-    }
-
     // Compile the callee:
-    JSObject* error = functionExecutable->compileForCall(callFrame, scope);
+    JSObject* error = functionExecutable->prepareForExecution(callFrame, function, scope, CodeForCall);
     if (error) {
-        throwError(callFrame, error);
+        callFrame->vm().throwException(callFrame, error);
         return CallFrameClosure();
     }
-    CodeBlock* newCodeBlock = &functionExecutable->generatedBytecodeForCall();
+    CodeBlock* newCodeBlock = functionExecutable->codeBlockForCall();
+    newCodeBlock->m_shouldAlwaysBeInlined = false;
 
     size_t argsCount = argumentCountIncludingThis;
 
-    CallFrame* newCallFrame = m_stack.pushFrame(callFrame, newCodeBlock, scope, argsCount, function);  
-    if (UNLIKELY(!newCallFrame)) {
-        throwStackOverflowError(callFrame);
-        return CallFrameClosure();
-    }
-
-    if (UNLIKELY(!newCallFrame)) {
-        throwStackOverflowError(callFrame);
-        return CallFrameClosure();
-    }
-
+    protoCallFrame->init(newCodeBlock, function, jsUndefined(), argsCount, args);
     // Return the successful closure:
-    CallFrameClosure result = { callFrame, newCallFrame, function, functionExecutable, &vm, scope, newCodeBlock->numParameters(), argumentCountIncludingThis };
+    CallFrameClosure result = { callFrame, protoCallFrame, function, functionExecutable, &vm, scope, newCodeBlock->numParameters(), argumentCountIncludingThis };
     return result;
 }
 
@@ -1165,253 +1150,226 @@ JSValue Interpreter::execute(CallFrameClosure& closure)
     SamplingScope samplingScope(this);
     
     ASSERT(!vm.isCollectorBusy());
+    RELEASE_ASSERT(vm.currentThreadIsHoldingAPILock());
     if (vm.isCollectorBusy())
         return jsNull();
 
     StackStats::CheckPoint stackCheckPoint;
-    m_stack.validateFence(closure.newCallFrame, "BEFORE");
-    closure.resetCallFrame();
-    m_stack.validateFence(closure.newCallFrame, "STEP 1");
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
         profiler->willExecute(closure.oldCallFrame, closure.function);
 
-    if (UNLIKELY(vm.watchdog.didFire(closure.oldCallFrame)))
+    if (UNLIKELY(vm.shouldTriggerTermination(closure.oldCallFrame)))
         return throwTerminatedExecutionException(closure.oldCallFrame);
 
-    // The code execution below may push more frames and point the topCallFrame
-    // to those newer frames, or it may pop to the top frame to the caller of
-    // the current repeat frame, or it may leave the top frame pointing to the
-    // current repeat frame.
-    //
-    // Hence, we need to preserve the topCallFrame here ourselves before
-    // repeating this call on a second callback function.
-
-    TopCallFrameSetter topCallFrame(vm, closure.newCallFrame);
-
     // Execute the code:
     JSValue result;
     {
         SamplingTool::CallRecord callRecord(m_sampler.get());
-        Watchdog::Scope watchdogScope(vm.watchdog);
-
-#if ENABLE(LLINT_C_LOOP)
-        result = LLInt::CLoop::execute(closure.newCallFrame, llint_function_for_call_prologue);
-#elif ENABLE(JIT)
-        result = closure.functionExecutable->generatedJITCodeForCall().execute(&m_stack, closure.newCallFrame, &vm);
-#endif // ENABLE(JIT)
+        result = closure.functionExecutable->generatedJITCodeForCall()->execute(&vm, closure.protoCallFrame);
     }
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
         profiler->didExecute(closure.oldCallFrame, closure.function);
 
-    m_stack.validateFence(closure.newCallFrame, "AFTER");
     return checkedReturn(result);
 }
 
-void Interpreter::endRepeatCall(CallFrameClosure& closure)
-{
-    m_stack.popFrame(closure.newCallFrame);
-}
-
 JSValue Interpreter::execute(EvalExecutable* eval, CallFrame* callFrame, JSValue thisValue, JSScope* scope)
 {
     VM& vm = *scope->vm();
     SamplingScope samplingScope(this);
     
     ASSERT(scope->vm() == &callFrame->vm());
-    ASSERT(isValidThisObject(thisValue, callFrame));
-    ASSERT(!vm.exception);
+    ASSERT(!vm.exception());
     ASSERT(!vm.isCollectorBusy());
+    RELEASE_ASSERT(vm.currentThreadIsHoldingAPILock());
     if (vm.isCollectorBusy())
         return jsNull();
 
-    DynamicGlobalObjectScope globalObjectScope(vm, scope->globalObject());
+    VMEntryScope entryScope(vm, scope->globalObject());
+    if (!vm.isSafeToRecurse())
+        return checkedReturn(throwStackOverflowError(callFrame));        
 
-    StackStats::CheckPoint stackCheckPoint;
-    const VMStackBounds vmStackBounds(vm, wtfThreadData().stack());
-    if (!vmStackBounds.isSafeToRecurse())
-        return checkedReturn(throwStackOverflowError(callFrame));
+    unsigned numVariables = eval->numVariables();
+    int numFunctions = eval->numberOfFunctionDecls();
 
-    // Compile the callee:
-    JSObject* compileError = eval->compile(callFrame, scope);
+    JSScope* variableObject;
+    if ((numVariables || numFunctions) && eval->isStrictMode()) {
+        scope = StrictEvalActivation::create(callFrame, scope);
+        variableObject = scope;
+    } else {
+        for (JSScope* node = scope; ; node = node->next()) {
+            RELEASE_ASSERT(node);
+            if (node->isGlobalObject()) {
+                variableObject = node;
+                break;
+            } 
+            if (JSLexicalEnvironment* lexicalEnvironment = jsDynamicCast<JSLexicalEnvironment*>(node)) {
+                if (lexicalEnvironment->symbolTable()->scopeType() == SymbolTable::ScopeType::VarScope) {
+                    variableObject = node;
+                    break;
+                }
+            }
+        }
+    }
+
+    JSObject* compileError = eval->prepareForExecution(callFrame, nullptr, scope, CodeForCall);
     if (UNLIKELY(!!compileError))
-        return checkedReturn(throwError(callFrame, compileError));
-    EvalCodeBlock* codeBlock = &eval->generatedBytecode();
-
-    JSObject* variableObject;
-    for (JSScope* node = scope; ; node = node->next()) {
-        RELEASE_ASSERT(node);
-        if (node->isVariableObject() && !node->isNameScopeObject()) {
-            variableObject = node;
-            break;
+        return checkedReturn(callFrame->vm().throwException(callFrame, compileError));
+    EvalCodeBlock* codeBlock = eval->codeBlock();
+
+    // We can't declare a "var"/"function" that overwrites a global "let"/"const"/"class" in a sloppy-mode eval.
+    if (variableObject->isGlobalObject() && !eval->isStrictMode() && (numVariables || numFunctions)) {
+        JSGlobalLexicalEnvironment* globalLexicalEnvironment = jsCast<JSGlobalObject*>(variableObject)->globalLexicalEnvironment();
+        for (unsigned i = 0; i < numVariables; ++i) {
+            const Identifier& ident = codeBlock->variable(i);
+            PropertySlot slot(globalLexicalEnvironment, PropertySlot::InternalMethodType::VMInquiry);
+            if (JSGlobalLexicalEnvironment::getOwnPropertySlot(globalLexicalEnvironment, callFrame, ident, slot)) {
+                return checkedReturn(callFrame->vm().throwException(callFrame,
+                    createTypeError(callFrame, makeString("Can't create duplicate global variable in eval: '", String(ident.impl()), "'"))));
+            }
+        }
+
+        for (int i = 0; i < numFunctions; ++i) {
+            FunctionExecutable* function = codeBlock->functionDecl(i);
+            PropertySlot slot(globalLexicalEnvironment, PropertySlot::InternalMethodType::VMInquiry);
+            if (JSGlobalLexicalEnvironment::getOwnPropertySlot(globalLexicalEnvironment, callFrame, function->name(), slot)) {
+                return checkedReturn(callFrame->vm().throwException(callFrame,
+                    createTypeError(callFrame, makeString("Can't create duplicate global variable in eval: '", String(function->name().impl()), "'"))));
+            }
         }
     }
 
-    unsigned numVariables = codeBlock->numVariables();
-    int numFunctions = codeBlock->numberOfFunctionDecls();
     if (numVariables || numFunctions) {
-        if (codeBlock->isStrictMode()) {
-            scope = StrictEvalActivation::create(callFrame);
-            variableObject = scope;
-        }
-        // Scope for BatchedTransitionOptimizer
         BatchedTransitionOptimizer optimizer(vm, variableObject);
+        if (variableObject->next())
+            variableObject->globalObject()->varInjectionWatchpoint()->fireAll("Executed eval, fired VarInjection watchpoint");
 
         for (unsigned i = 0; i < numVariables; ++i) {
             const Identifier& ident = codeBlock->variable(i);
             if (!variableObject->hasProperty(callFrame, ident)) {
-                PutPropertySlot slot;
+                PutPropertySlot slot(variableObject);
                 variableObject->methodTable()->put(variableObject, callFrame, ident, jsUndefined(), slot);
             }
         }
 
         for (int i = 0; i < numFunctions; ++i) {
             FunctionExecutable* function = codeBlock->functionDecl(i);
-            PutPropertySlot slot;
-            variableObject->methodTable()->put(variableObject, callFrame, function->name(), JSFunction::create(callFrame, function, scope), slot);
+            PutPropertySlot slot(variableObject);
+            variableObject->methodTable()->put(variableObject, callFrame, function->name(), JSFunction::create(vm, function, scope), slot);
         }
     }
 
-    if (UNLIKELY(vm.watchdog.didFire(callFrame)))
+    if (UNLIKELY(vm.shouldTriggerTermination(callFrame)))
         return throwTerminatedExecutionException(callFrame);
 
-    // Push the frame:
     ASSERT(codeBlock->numParameters() == 1); // 1 parameter for 'this'.
-    CallFrame* newCallFrame = m_stack.pushFrame(callFrame, codeBlock, scope, 1, 0);
-    if (UNLIKELY(!newCallFrame))
-        return checkedReturn(throwStackOverflowError(callFrame));
 
-    // Set the arguments for the callee:
-    newCallFrame->setThisValue(thisValue);
+    ProtoCallFrame protoCallFrame;
+    protoCallFrame.init(codeBlock, JSCallee::create(vm, scope->globalObject(), scope), thisValue, 1);
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
-        profiler->willExecute(callFrame, eval->sourceURL(), eval->lineNo());
+        profiler->willExecute(callFrame, eval->sourceURL(), eval->firstLine(), eval->startColumn());
 
     // Execute the code:
     JSValue result;
     {
         SamplingTool::CallRecord callRecord(m_sampler.get());
-        Watchdog::Scope watchdogScope(vm.watchdog);
-
-#if ENABLE(LLINT_C_LOOP)
-        result = LLInt::CLoop::execute(newCallFrame, llint_eval_prologue);
-#elif ENABLE(JIT)
-        result = eval->generatedJITCode().execute(&m_stack, newCallFrame, &vm);
-#endif // ENABLE(JIT)
+        result = eval->generatedJITCode()->execute(&vm, &protoCallFrame);
     }
 
     if (LegacyProfiler* profiler = vm.enabledProfiler())
-        profiler->didExecute(callFrame, eval->sourceURL(), eval->lineNo());
+        profiler->didExecute(callFrame, eval->sourceURL(), eval->firstLine(), eval->startColumn());
 
-    m_stack.popFrame(newCallFrame);
     return checkedReturn(result);
 }
 
-NEVER_INLINE void Interpreter::debug(CallFrame* callFrame, DebugHookID debugHookID, int firstLine, int lastLine, int column)
+JSValue Interpreter::execute(ModuleProgramExecutable* executable, CallFrame* callFrame, JSModuleEnvironment* scope)
 {
-    Debugger* debugger = callFrame->dynamicGlobalObject()->debugger();
-    if (!debugger)
-        return;
+    VM& vm = *scope->vm();
+    SamplingScope samplingScope(this);
 
-    switch (debugHookID) {
-        case DidEnterCallFrame:
-            debugger->callEvent(callFrame, callFrame->codeBlock()->ownerExecutable()->sourceID(), firstLine, column);
-            return;
-        case WillLeaveCallFrame:
-            debugger->returnEvent(callFrame, callFrame->codeBlock()->ownerExecutable()->sourceID(), lastLine, column);
-            return;
-        case WillExecuteStatement:
-            debugger->atStatement(callFrame, callFrame->codeBlock()->ownerExecutable()->sourceID(), firstLine, column);
-            return;
-        case WillExecuteProgram:
-            debugger->willExecuteProgram(callFrame, callFrame->codeBlock()->ownerExecutable()->sourceID(), firstLine, column);
-            return;
-        case DidExecuteProgram:
-            debugger->didExecuteProgram(callFrame, callFrame->codeBlock()->ownerExecutable()->sourceID(), lastLine, column);
-            return;
-        case DidReachBreakpoint:
-            debugger->didReachBreakpoint(callFrame, callFrame->codeBlock()->ownerExecutable()->sourceID(), lastLine, column);
-            return;
-    }
-}
-    
-JSValue Interpreter::retrieveArgumentsFromVMCode(CallFrame* callFrame, JSFunction* function) const
-{
-    CallFrame* functionCallFrame = findFunctionCallFrameFromVMCode(callFrame, function);
-    if (!functionCallFrame)
+    ASSERT(scope->vm() == &callFrame->vm());
+    ASSERT(!vm.exception());
+    ASSERT(!vm.isCollectorBusy());
+    RELEASE_ASSERT(vm.currentThreadIsHoldingAPILock());
+    if (vm.isCollectorBusy())
         return jsNull();
 
-    Arguments* arguments = Arguments::create(functionCallFrame->vm(), functionCallFrame);
-    arguments->tearOff(functionCallFrame);
-    return JSValue(arguments);
-}
+    VMEntryScope entryScope(vm, scope->globalObject());
+    if (!vm.isSafeToRecurse())
+        return checkedReturn(throwStackOverflowError(callFrame));
 
-JSValue Interpreter::retrieveCallerFromVMCode(CallFrame* callFrame, JSFunction* function) const
-{
-    CallFrame* functionCallFrame = findFunctionCallFrameFromVMCode(callFrame, function);
+    JSObject* compileError = executable->prepareForExecution(callFrame, nullptr, scope, CodeForCall);
+    if (UNLIKELY(!!compileError))
+        return checkedReturn(callFrame->vm().throwException(callFrame, compileError));
+    ModuleProgramCodeBlock* codeBlock = executable->codeBlock();
 
-    if (!functionCallFrame)
-        return jsNull();
-    
-    unsigned bytecodeOffset;
-    CodeBlock* unusedCallerCodeBlock = 0;
-    CallFrame* callerFrame = getCallerInfo(&callFrame->vm(), functionCallFrame, bytecodeOffset, unusedCallerCodeBlock);
-    if (!callerFrame)
-        return jsNull();
-    JSValue caller = callerFrame->callee();
-    if (!caller)
-        return jsNull();
+    if (UNLIKELY(vm.shouldTriggerTermination(callFrame)))
+        return throwTerminatedExecutionException(callFrame);
+
+    ASSERT(codeBlock->numParameters() == 1); // 1 parameter for 'this'.
+
+    // The |this| of the module is always `undefined`.
+    // http://www.ecma-international.org/ecma-262/6.0/#sec-module-environment-records-hasthisbinding
+    // http://www.ecma-international.org/ecma-262/6.0/#sec-module-environment-records-getthisbinding
+    ProtoCallFrame protoCallFrame;
+    protoCallFrame.init(codeBlock, JSCallee::create(vm, scope->globalObject(), scope), jsUndefined(), 1);
+
+    if (LegacyProfiler* profiler = vm.enabledProfiler())
+        profiler->willExecute(callFrame, executable->sourceURL(), executable->firstLine(), executable->startColumn());
 
-    // Skip over function bindings.
-    ASSERT(caller.isObject());
-    while (asObject(caller)->inherits(&JSBoundFunction::s_info)) {
-        callerFrame = getCallerInfo(&callFrame->vm(), callerFrame, bytecodeOffset, unusedCallerCodeBlock);
-        if (!callerFrame)
-            return jsNull();
-        caller = callerFrame->callee();
-        if (!caller)
-            return jsNull();
+    // Execute the code:
+    JSValue result;
+    {
+        SamplingTool::CallRecord callRecord(m_sampler.get());
+        result = executable->generatedJITCode()->execute(&vm, &protoCallFrame);
     }
 
-    return caller;
+    if (LegacyProfiler* profiler = vm.enabledProfiler())
+        profiler->didExecute(callFrame, executable->sourceURL(), executable->firstLine(), executable->startColumn());
+
+    return checkedReturn(result);
 }
 
-void Interpreter::retrieveLastCaller(CallFrame* callFrame, int& lineNumber, intptr_t& sourceID, String& sourceURL, JSValue& function) const
+NEVER_INLINE void Interpreter::debug(CallFrame* callFrame, DebugHookID debugHookID)
 {
-    function = JSValue();
-    lineNumber = -1;
-    sourceURL = String();
-
-    CallFrame* callerFrame = callFrame->callerFrame();
-    if (callerFrame->hasHostCallFrameFlag())
+    Debugger* debugger = callFrame->vmEntryGlobalObject()->debugger();
+    if (!debugger)
         return;
 
-    CodeBlock* callerCodeBlock = callerFrame->codeBlock();
-    if (!callerCodeBlock)
-        return;
-    unsigned bytecodeOffset = 0;
-    bytecodeOffset = callerCodeBlock->bytecodeOffset(callerFrame, callFrame->returnPC());
-    lineNumber = callerCodeBlock->lineNumberForBytecodeOffset(bytecodeOffset - 1);
-    sourceID = callerCodeBlock->ownerExecutable()->sourceID();
-    sourceURL = callerCodeBlock->ownerExecutable()->sourceURL();
-    function = callerFrame->callee();
-}
+    ASSERT(callFrame->codeBlock()->hasDebuggerRequests());
+    ASSERT(!callFrame->hadException());
 
-CallFrame* Interpreter::findFunctionCallFrameFromVMCode(CallFrame* callFrame, JSFunction* function)
-{
-    for (CallFrame* candidate = callFrame->trueCallFrameFromVMCode(); candidate; candidate = candidate->trueCallerFrame()) {
-        if (candidate->callee() == function)
-            return candidate;
+    switch (debugHookID) {
+        case DidEnterCallFrame:
+            debugger->callEvent(callFrame);
+            break;
+        case WillLeaveCallFrame:
+            debugger->returnEvent(callFrame);
+            break;
+        case WillExecuteStatement:
+            debugger->atStatement(callFrame);
+            break;
+        case WillExecuteProgram:
+            debugger->willExecuteProgram(callFrame);
+            break;
+        case DidExecuteProgram:
+            debugger->didExecuteProgram(callFrame);
+            break;
+        case DidReachBreakpoint:
+            debugger->didReachBreakpoint(callFrame);
+            break;
     }
-    return 0;
-}
+    ASSERT(!callFrame->hadException());
+}    
 
 void Interpreter::enableSampler()
 {
 #if ENABLE(OPCODE_SAMPLING)
     if (!m_sampler) {
-        m_sampler = adoptPtr(new SamplingTool(this));
+        m_sampler = std::make_unique<SamplingTool>(this);
         m_sampler->setup();
     }
 #endif
diff --git a/Source/JavaScriptCore/interpreter/Interpreter.h b/Source/JavaScriptCore/interpreter/Interpreter.h
index e5eca0e1c..aba745f17 100644
--- a/Source/JavaScriptCore/interpreter/Interpreter.h
+++ b/Source/JavaScriptCore/interpreter/Interpreter.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008, 2013 Apple Inc. All rights reserved.
+ * Copyright (C) 2008, 2013, 2015 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Research In Motion Limited. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -11,7 +11,7 @@
  * 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.
  *
@@ -33,11 +33,12 @@
 #include "ArgList.h"
 #include "JSCJSValue.h"
 #include "JSCell.h"
-#include "JSFunction.h"
 #include "JSObject.h"
 #include "JSStack.h"
 #include "LLIntData.h"
 #include "Opcode.h"
+#include "SourceProvider.h"
+#include "StackAlignment.h"
 
 #include <wtf/HashMap.h>
 #include <wtf/text/StringBuilder.h>
@@ -49,16 +50,23 @@ namespace JSC {
     class ExecutableBase;
     class FunctionExecutable;
     class VM;
+    class JSFunction;
     class JSGlobalObject;
+    class JSModuleEnvironment;
+    class JSModuleRecord;
     class LLIntOffsetsExtractor;
     class ProgramExecutable;
+    class ModuleProgramExecutable;
     class Register;
     class JSScope;
     class SamplingTool;
     struct CallFrameClosure;
     struct HandlerInfo;
     struct Instruction;
-    
+    struct ProtoCallFrame;
+
+    enum UnwindStart { UnwindFromCurrentFrame, UnwindFromCallerFrame };
+
     enum DebugHookID {
         WillExecuteProgram,
         DidExecuteProgram,
@@ -71,6 +79,7 @@ namespace JSC {
     enum StackFrameCodeType {
         StackFrameGlobalCode,
         StackFrameEvalCode,
+        StackFrameModuleCode,
         StackFrameFunctionCode,
         StackFrameNativeCode
     };
@@ -78,7 +87,7 @@ namespace JSC {
     struct StackFrame {
         Strong<JSObject> callee;
         StackFrameCodeType codeType;
-        Strong<ExecutableBase> executable;
+        Strong<ScriptExecutable> executable;
         Strong<UnlinkedCodeBlock> codeBlock;
         RefPtr<SourceProvider> code;
         int lineOffset;
@@ -87,58 +96,38 @@ namespace JSC {
         unsigned bytecodeOffset;
         String sourceURL;
         JS_EXPORT_PRIVATE String toString(CallFrame*);
-        String friendlySourceURL() const
-        {
-            String traceLine;
-
-            switch (codeType) {
-            case StackFrameEvalCode:
-            case StackFrameFunctionCode:
-            case StackFrameGlobalCode:
-                if (!sourceURL.isEmpty())
-                    traceLine = sourceURL.impl();
-                break;
-            case StackFrameNativeCode:
-                traceLine = "[native code]";
-                break;
-            }
-            return traceLine.isNull() ? emptyString() : traceLine;
-        }
-        String friendlyFunctionName(CallFrame* callFrame) const
-        {
-            String traceLine;
-            JSObject* stackFrameCallee = callee.get();
-
-            switch (codeType) {
-            case StackFrameEvalCode:
-                traceLine = "eval code";
-                break;
-            case StackFrameNativeCode:
-                if (callee)
-                    traceLine = getCalculatedDisplayName(callFrame, stackFrameCallee).impl();
-                break;
-            case StackFrameFunctionCode:
-                traceLine = getCalculatedDisplayName(callFrame, stackFrameCallee).impl();
-                break;
-            case StackFrameGlobalCode:
-                traceLine = "global code";
-                break;
-            }
-            return traceLine.isNull() ? emptyString() : traceLine;
-        }
+        String friendlySourceURL() const;
+        String friendlyFunctionName(CallFrame*) const;
         JS_EXPORT_PRIVATE void computeLineAndColumn(unsigned& line, unsigned& column);
 
     private:
         void expressionInfo(int& divot, int& startOffset, int& endOffset, unsigned& line, unsigned& column);
     };
 
+    class SuspendExceptionScope {
+    public:
+        SuspendExceptionScope(VM* vm)
+            : m_vm(vm)
+        {
+            oldException = vm->exception();
+            vm->clearException();
+        }
+        ~SuspendExceptionScope()
+        {
+            m_vm->restorePreviousException(oldException);
+        }
+    private:
+        Exception* oldException;
+        VM* m_vm;
+    };
+    
     class TopCallFrameSetter {
     public:
-        TopCallFrameSetter(VM& global, CallFrame* callFrame)
-            : vm(global)
-            , oldCallFrame(global.topCallFrame) 
+        TopCallFrameSetter(VM& currentVM, CallFrame* callFrame)
+            : vm(currentVM)
+            , oldCallFrame(currentVM.topCallFrame) 
         {
-            global.topCallFrame = callFrame;
+            currentVM.topCallFrame = callFrame;
         }
         
         ~TopCallFrameSetter() 
@@ -152,33 +141,52 @@ namespace JSC {
     
     class NativeCallFrameTracer {
     public:
-        ALWAYS_INLINE NativeCallFrameTracer(VM* global, CallFrame* callFrame)
+        ALWAYS_INLINE NativeCallFrameTracer(VM* vm, CallFrame* callFrame)
         {
-            ASSERT(global);
+            ASSERT(vm);
             ASSERT(callFrame);
-            global->topCallFrame = callFrame;
+            ASSERT(callFrame < vm->topVMEntryFrame);
+            vm->topCallFrame = callFrame;
         }
     };
 
+    class NativeCallFrameTracerWithRestore {
+    public:
+        ALWAYS_INLINE NativeCallFrameTracerWithRestore(VM* vm, VMEntryFrame* vmEntryFrame, CallFrame* callFrame)
+            : m_vm(vm)
+        {
+            ASSERT(vm);
+            ASSERT(callFrame);
+            m_savedTopVMEntryFrame = vm->topVMEntryFrame;
+            m_savedTopCallFrame = vm->topCallFrame;
+            vm->topVMEntryFrame = vmEntryFrame;
+            vm->topCallFrame = callFrame;
+        }
+
+        ALWAYS_INLINE ~NativeCallFrameTracerWithRestore()
+        {
+            m_vm->topVMEntryFrame = m_savedTopVMEntryFrame;
+            m_vm->topCallFrame = m_savedTopCallFrame;
+        }
+
+    private:
+        VM* m_vm;
+        VMEntryFrame* m_savedTopVMEntryFrame;
+        CallFrame* m_savedTopCallFrame;
+    };
+
     class Interpreter {
         WTF_MAKE_FAST_ALLOCATED;
         friend class CachedCall;
         friend class LLIntOffsetsExtractor;
         friend class JIT;
+        friend class VM;
 
     public:
-        class ErrorHandlingMode {
-        public:
-            JS_EXPORT_PRIVATE ErrorHandlingMode(ExecState*);
-            JS_EXPORT_PRIVATE ~ErrorHandlingMode();
-        private:
-            Interpreter& m_interpreter;
-        };
-
         Interpreter(VM &);
         ~Interpreter();
         
-        void initialize(bool canUseJIT);
+        void initialize();
 
         JSStack& stack() { return m_stack; }
         
@@ -195,7 +203,7 @@ namespace JSC {
         OpcodeID getOpcodeID(Opcode opcode)
         {
             ASSERT(m_initialized);
-#if ENABLE(COMPUTED_GOTO_OPCODES) && ENABLE(LLINT)
+#if ENABLE(COMPUTED_GOTO_OPCODES)
             ASSERT(isOpcode(opcode));
             return m_opcodeIDTable.get(opcode);
 #else
@@ -207,24 +215,23 @@ namespace JSC {
 
         JSValue execute(ProgramExecutable*, CallFrame*, JSObject* thisObj);
         JSValue executeCall(CallFrame*, JSObject* function, CallType, const CallData&, JSValue thisValue, const ArgList&);
-        JSObject* executeConstruct(CallFrame*, JSObject* function, ConstructType, const ConstructData&, const ArgList&);
+        JSObject* executeConstruct(CallFrame*, JSObject* function, ConstructType, const ConstructData&, const ArgList&, JSValue newTarget);
         JSValue execute(EvalExecutable*, CallFrame*, JSValue thisValue, JSScope*);
+        JSValue execute(ModuleProgramExecutable*, CallFrame*, JSModuleEnvironment*);
 
-        JSValue retrieveArgumentsFromVMCode(CallFrame*, JSFunction*) const;
-        JSValue retrieveCallerFromVMCode(CallFrame*, JSFunction*) const;
-        JS_EXPORT_PRIVATE void retrieveLastCaller(CallFrame*, int& lineNumber, intptr_t& sourceID, String& sourceURL, JSValue& function) const;
-        
         void getArgumentsData(CallFrame*, JSFunction*&, ptrdiff_t& firstParameterIndex, Register*& argv, int& argc);
         
         SamplingTool* sampler() { return m_sampler.get(); }
 
-        bool isInErrorHandlingMode() { return m_errorHandlingModeReentry; }
+        NEVER_INLINE HandlerInfo* unwind(VM&, CallFrame*&, Exception*, UnwindStart);
+        void notifyDebuggerOfExceptionToBeThrown(CallFrame*, Exception*);
+        NEVER_INLINE void debug(CallFrame*, DebugHookID);
+        JSString* stackTraceAsString(ExecState*, Vector<StackFrame>);
 
-        NEVER_INLINE HandlerInfo* throwException(CallFrame*&, JSValue&, unsigned bytecodeOffset);
-        NEVER_INLINE void debug(CallFrame*, DebugHookID, int firstLine, int lastLine, int column);
-        static const String getTraceLine(CallFrame*, StackFrameCodeType, const String&, int);
-        JS_EXPORT_PRIVATE static void getStackTrace(VM*, Vector<StackFrame>& results, size_t maxStackSize = std::numeric_limits<size_t>::max());
-        static void addStackTraceIfNecessary(CallFrame*, JSValue error);
+        static EncodedJSValue JSC_HOST_CALL constructWithErrorConstructor(ExecState*);
+        static EncodedJSValue JSC_HOST_CALL callErrorConstructor(ExecState*);
+        static EncodedJSValue JSC_HOST_CALL constructWithNativeErrorConstructor(ExecState*);
+        static EncodedJSValue JSC_HOST_CALL callNativeErrorConstructor(ExecState*);
 
         void dumpSampleData(ExecState* exec);
         void startSampling();
@@ -232,29 +239,30 @@ namespace JSC {
 
         JS_EXPORT_PRIVATE void dumpCallFrame(CallFrame*);
 
+        void getStackTrace(Vector<StackFrame>& results, size_t maxStackSize = std::numeric_limits<size_t>::max());
+
     private:
         enum ExecutionFlag { Normal, InitializeAndReturn };
 
-        CallFrameClosure prepareForRepeatCall(FunctionExecutable*, CallFrame*, JSFunction*, int argumentCountIncludingThis, JSScope*);
-        void endRepeatCall(CallFrameClosure&);
+        CallFrameClosure prepareForRepeatCall(FunctionExecutable*, CallFrame*, ProtoCallFrame*, JSFunction*, int argumentCountIncludingThis, JSScope*, JSValue*);
+
         JSValue execute(CallFrameClosure&);
 
-        NEVER_INLINE bool unwindCallFrame(CallFrame*&, JSValue, unsigned& bytecodeOffset, CodeBlock*&);
 
-        static CallFrame* findFunctionCallFrameFromVMCode(CallFrame*, JSFunction*);
 
         void dumpRegisters(CallFrame*);
         
-        bool isCallBytecode(Opcode opcode) { return opcode == getOpcode(op_call) || opcode == getOpcode(op_construct) || opcode == getOpcode(op_call_eval); }
+        bool isCallBytecode(Opcode opcode) { return opcode == getOpcode(op_call) || opcode == getOpcode(op_construct) || opcode == getOpcode(op_call_eval) || opcode == getOpcode(op_tail_call); }
 
         void enableSampler();
         int m_sampleEntryDepth;
-        OwnPtr<SamplingTool> m_sampler;
+        std::unique_ptr<SamplingTool> m_sampler;
 
+        VM& m_vm;
         JSStack m_stack;
         int m_errorHandlingModeReentry;
         
-#if ENABLE(COMPUTED_GOTO_OPCODES) && ENABLE(LLINT)
+#if ENABLE(COMPUTED_GOTO_OPCODES)
         Opcode* m_opcodeTable; // Maps OpcodeID => Opcode for compiling
         HashMap<Opcode, OpcodeID> m_opcodeIDTable; // Maps Opcode => OpcodeID for decompiling
 #endif
@@ -264,15 +272,30 @@ namespace JSC {
 #endif
     };
 
-    // This value must not be an object that would require this conversion (WebCore's global object).
-    inline bool isValidThisObject(JSValue thisValue, ExecState* exec)
+    JSValue eval(CallFrame*);
+
+    inline CallFrame* calleeFrameForVarargs(CallFrame* callFrame, unsigned numUsedStackSlots, unsigned argumentCountIncludingThis)
     {
-        return !thisValue.isObject() || thisValue.toThisObject(exec) == thisValue;
+        // We want the new frame to be allocated on a stack aligned offset with a stack
+        // aligned size. Align the size here.
+        argumentCountIncludingThis = WTF::roundUpToMultipleOf(
+            stackAlignmentRegisters(),
+            argumentCountIncludingThis + JSStack::CallFrameHeaderSize) - JSStack::CallFrameHeaderSize;
+
+        // Align the frame offset here.
+        unsigned paddedCalleeFrameOffset = WTF::roundUpToMultipleOf(
+            stackAlignmentRegisters(),
+            numUsedStackSlots + argumentCountIncludingThis + JSStack::CallFrameHeaderSize);
+        return CallFrame::create(callFrame->registers() - paddedCalleeFrameOffset);
     }
 
-    JSValue eval(CallFrame*);
-    CallFrame* loadVarargs(CallFrame*, JSStack*, JSValue thisValue, JSValue arguments, int firstFreeRegister);
-
+    unsigned sizeOfVarargs(CallFrame* exec, JSValue arguments, uint32_t firstVarArgOffset);
+    static const unsigned maxArguments = 0x10000;
+    unsigned sizeFrameForVarargs(CallFrame* exec, JSStack*, JSValue arguments, unsigned numUsedStackSlots, uint32_t firstVarArgOffset);
+    void loadVarargs(CallFrame* execCaller, VirtualRegister firstElementDest, JSValue source, uint32_t offset, uint32_t length);
+    void setupVarargsFrame(CallFrame* execCaller, CallFrame* execCallee, JSValue arguments, uint32_t firstVarArgOffset, uint32_t length);
+    void setupVarargsFrameAndSetThis(CallFrame* execCaller, CallFrame* execCallee, JSValue thisValue, JSValue arguments, uint32_t firstVarArgOffset, uint32_t length);
+    
 } // namespace JSC
 
 #endif // Interpreter_h
diff --git a/Source/JavaScriptCore/interpreter/JSStack.cpp b/Source/JavaScriptCore/interpreter/JSStack.cpp
index ec2962a92..6e441dfd5 100644
--- a/Source/JavaScriptCore/interpreter/JSStack.cpp
+++ b/Source/JavaScriptCore/interpreter/JSStack.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008 Apple Inc. All rights reserved.
+ * Copyright (C) 2008, 2013, 2014, 2015 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -10,7 +10,7 @@
  * 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.
  *
@@ -27,125 +27,158 @@
  */
 
 #include "config.h"
-#include "JSStack.h"
 #include "JSStackInlines.h"
 
 #include "ConservativeRoots.h"
 #include "Interpreter.h"
+#include "JSCInlines.h"
+#include "Options.h"
+#include <wtf/Lock.h>
 
 namespace JSC {
 
+#if !ENABLE(JIT)
 static size_t committedBytesCount = 0;
 
-static Mutex& stackStatisticsMutex()
+static size_t commitSize()
 {
-    DEFINE_STATIC_LOCAL(Mutex, staticMutex, ());
-    return staticMutex;
-}    
+    static size_t size = std::max<size_t>(16 * 1024, pageSize());
+    return size;
+}
+
+static StaticLock stackStatisticsMutex;
+#endif // !ENABLE(JIT)
 
-JSStack::JSStack(VM& vm, size_t capacity)
-    : m_end(0)
+JSStack::JSStack(VM& vm)
+    : m_vm(vm)
     , m_topCallFrame(vm.topCallFrame)
+#if !ENABLE(JIT)
+    , m_end(0)
+    , m_reservedZoneSizeInRegisters(0)
+#endif
 {
+#if !ENABLE(JIT)
+    size_t capacity = Options::maxPerThreadStackUsage();
     ASSERT(capacity && isPageAligned(capacity));
 
-    m_reservation = PageReservation::reserve(roundUpAllocationSize(capacity * sizeof(Register), commitSize), OSAllocator::JSVMStackPages);
-    m_end = static_cast<Register*>(m_reservation.base());
-    m_commitEnd = static_cast<Register*>(m_reservation.base());
-
-    disableErrorStackReserve();
+    m_reservation = PageReservation::reserve(WTF::roundUpToMultipleOf(commitSize(), capacity), OSAllocator::JSVMStackPages);
+    setStackLimit(highAddress());
+    m_commitTop = highAddress();
+    
+    m_lastStackTop = baseOfStack();
+#endif // !ENABLE(JIT)
 
     m_topCallFrame = 0;
 }
 
+#if !ENABLE(JIT)
 JSStack::~JSStack()
 {
-    void* base = m_reservation.base();
-    m_reservation.decommit(base, reinterpret_cast<intptr_t>(m_commitEnd) - reinterpret_cast<intptr_t>(base));
-    addToCommittedByteCount(-(reinterpret_cast<intptr_t>(m_commitEnd) - reinterpret_cast<intptr_t>(base)));
+    ptrdiff_t sizeToDecommit = reinterpret_cast<char*>(highAddress()) - reinterpret_cast<char*>(m_commitTop);
+    m_reservation.decommit(reinterpret_cast<void*>(m_commitTop), sizeToDecommit);
+    addToCommittedByteCount(-sizeToDecommit);
     m_reservation.deallocate();
 }
 
-bool JSStack::growSlowCase(Register* newEnd)
+bool JSStack::growSlowCase(Register* newTopOfStack)
 {
+    Register* newTopOfStackWithReservedZone = newTopOfStack - m_reservedZoneSizeInRegisters;
+
     // If we have already committed enough memory to satisfy this request,
     // just update the end pointer and return.
-    if (newEnd <= m_commitEnd) {
-        m_end = newEnd;
+    if (newTopOfStackWithReservedZone >= m_commitTop) {
+        setStackLimit(newTopOfStack);
         return true;
     }
 
     // Compute the chunk size of additional memory to commit, and see if we
     // have it is still within our budget. If not, we'll fail to grow and
     // return false.
-    long delta = roundUpAllocationSize(reinterpret_cast<char*>(newEnd) - reinterpret_cast<char*>(m_commitEnd), commitSize);
-    if (reinterpret_cast<char*>(m_commitEnd) + delta > reinterpret_cast<char*>(m_useableEnd))
+    ptrdiff_t delta = reinterpret_cast<char*>(m_commitTop) - reinterpret_cast<char*>(newTopOfStackWithReservedZone);
+    delta = WTF::roundUpToMultipleOf(commitSize(), delta);
+    Register* newCommitTop = m_commitTop - (delta / sizeof(Register));
+    if (newCommitTop < reservationTop())
         return false;
 
-    // Otherwise, the growth is still within our budget. Go ahead and commit
-    // it and return true.
-    m_reservation.commit(m_commitEnd, delta);
+    // Otherwise, the growth is still within our budget. Commit it and return true.
+    m_reservation.commit(newCommitTop, delta);
     addToCommittedByteCount(delta);
-    m_commitEnd = reinterpret_cast_ptr<Register*>(reinterpret_cast<char*>(m_commitEnd) + delta);
-    m_end = newEnd;
+    m_commitTop = newCommitTop;
+    setStackLimit(newTopOfStack);
     return true;
 }
 
-void JSStack::gatherConservativeRoots(ConservativeRoots& conservativeRoots)
+void JSStack::gatherConservativeRoots(ConservativeRoots& conservativeRoots, JITStubRoutineSet& jitStubRoutines, CodeBlockSet& codeBlocks)
 {
-    conservativeRoots.add(begin(), getTopOfStack());
+    conservativeRoots.add(topOfStack() + 1, highAddress(), jitStubRoutines, codeBlocks);
 }
 
-void JSStack::gatherConservativeRoots(ConservativeRoots& conservativeRoots, JITStubRoutineSet& jitStubRoutines, DFGCodeBlocks& dfgCodeBlocks)
+void JSStack::sanitizeStack()
 {
-    conservativeRoots.add(begin(), getTopOfStack(), jitStubRoutines, dfgCodeBlocks);
+#if !ASAN_ENABLED
+    ASSERT(topOfStack() <= baseOfStack());
+    
+    if (m_lastStackTop < topOfStack()) {
+        char* begin = reinterpret_cast<char*>(m_lastStackTop + 1);
+        char* end = reinterpret_cast<char*>(topOfStack() + 1);
+        memset(begin, 0, end - begin);
+    }
+    
+    m_lastStackTop = topOfStack();
+#endif
 }
 
 void JSStack::releaseExcessCapacity()
 {
-    ptrdiff_t delta = reinterpret_cast<uintptr_t>(m_commitEnd) - reinterpret_cast<uintptr_t>(m_reservation.base());
-    m_reservation.decommit(m_reservation.base(), delta);
+    Register* highAddressWithReservedZone = highAddress() - m_reservedZoneSizeInRegisters;
+    ptrdiff_t delta = reinterpret_cast<char*>(highAddressWithReservedZone) - reinterpret_cast<char*>(m_commitTop);
+    m_reservation.decommit(m_commitTop, delta);
     addToCommittedByteCount(-delta);
-    m_commitEnd = static_cast<Register*>(m_reservation.base());
+    m_commitTop = highAddressWithReservedZone;
 }
 
-void JSStack::initializeThreading()
+void JSStack::addToCommittedByteCount(long byteCount)
 {
-    stackStatisticsMutex();
+    LockHolder locker(stackStatisticsMutex);
+    ASSERT(static_cast<long>(committedBytesCount) + byteCount > -1);
+    committedBytesCount += byteCount;
 }
 
-size_t JSStack::committedByteCount()
+void JSStack::setReservedZoneSize(size_t reservedZoneSize)
 {
-    MutexLocker locker(stackStatisticsMutex());
-    return committedBytesCount;
+    m_reservedZoneSizeInRegisters = reservedZoneSize / sizeof(Register);
+    if (m_commitTop >= (m_end + 1) - m_reservedZoneSizeInRegisters)
+        growSlowCase(m_end + 1);
 }
+#endif // !ENABLE(JIT)
 
-void JSStack::addToCommittedByteCount(long byteCount)
+#if ENABLE(JIT)
+Register* JSStack::lowAddress() const
 {
-    MutexLocker locker(stackStatisticsMutex());
-    ASSERT(static_cast<long>(committedBytesCount) + byteCount > -1);
-    committedBytesCount += byteCount;
+    ASSERT(wtfThreadData().stack().isGrowingDownward());
+    return reinterpret_cast<Register*>(m_vm.stackLimit());
 }
 
-void JSStack::enableErrorStackReserve()
+Register* JSStack::highAddress() const
 {
-    m_useableEnd = reservationEnd();
+    ASSERT(wtfThreadData().stack().isGrowingDownward());
+    return reinterpret_cast<Register*>(wtfThreadData().stack().origin());
 }
+#endif // ENABLE(JIT)
 
-void JSStack::disableErrorStackReserve()
+size_t JSStack::committedByteCount()
 {
-    char* useableEnd = reinterpret_cast<char*>(reservationEnd()) - commitSize;
-    m_useableEnd = reinterpret_cast_ptr<Register*>(useableEnd);
-
-    // By the time we get here, we are guaranteed to be destructing the last
-    // Interpreter::ErrorHandlingMode that enabled this reserve in the first
-    // place. That means the stack space beyond m_useableEnd before we
-    // enabled the reserve was not previously in use. Hence, it is safe to
-    // shrink back to that m_useableEnd.
-    if (m_end > m_useableEnd) {
-        ASSERT(m_topCallFrame->frameExtent() <= m_useableEnd);
-        shrink(m_useableEnd);
-    }
+#if !ENABLE(JIT)
+    LockHolder locker(stackStatisticsMutex);
+    return committedBytesCount;
+#else
+    // When using the C stack, we don't know how many stack pages are actually
+    // committed. So, we use the current stack usage as an estimate.
+    ASSERT(wtfThreadData().stack().isGrowingDownward());
+    int8_t* current = reinterpret_cast<int8_t*>(&current);
+    int8_t* high = reinterpret_cast<int8_t*>(wtfThreadData().stack().origin());
+    return high - current;
+#endif
 }
 
 } // namespace JSC
diff --git a/Source/JavaScriptCore/interpreter/JSStack.h b/Source/JavaScriptCore/interpreter/JSStack.h
index fe4012d83..770db0920 100644
--- a/Source/JavaScriptCore/interpreter/JSStack.h
+++ b/Source/JavaScriptCore/interpreter/JSStack.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
+ * Copyright (C) 2008, 2009, 2013, 2014 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -10,7 +10,7 @@
  * 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.
  *
@@ -35,124 +35,117 @@
 #include <wtf/PageReservation.h>
 #include <wtf/VMTags.h>
 
-#if !defined(NDEBUG) && !defined(ENABLE_DEBUG_JSSTACK)
-#define ENABLE_DEBUG_JSSTACK 1
-#endif
-
 namespace JSC {
 
+    class CodeBlockSet;
     class ConservativeRoots;
-    class DFGCodeBlocks;
     class ExecState;
     class JITStubRoutineSet;
     class VM;
     class LLIntOffsetsExtractor;
 
+    struct Instruction;
+    typedef ExecState CallFrame;
+
+    struct CallerFrameAndPC {
+        CallFrame* callerFrame;
+        Instruction* pc;
+    };
+
     class JSStack {
         WTF_MAKE_NONCOPYABLE(JSStack);
     public:
         enum CallFrameHeaderEntry {
-            CallFrameHeaderSize = 6,
-
-            ArgumentCount = -6,
-            CallerFrame = -5,
-            Callee = -4,
-            ScopeChain = -3,
-            ReturnPC = -2, // This is either an Instruction* or a pointer into JIT generated code stored as an Instruction*.
-            CodeBlock = -1,
+            CallerFrameAndPCSize = sizeof(CallerFrameAndPC) / sizeof(Register),
+            CodeBlock = CallerFrameAndPCSize,
+            Callee,
+            ArgumentCount,
+            CallFrameHeaderSize,
+
+            // The following entries are not part of the CallFrameHeader but are provided here as a convenience:
+            ThisArgument = CallFrameHeaderSize,
+            FirstArgument,
         };
 
-        static const size_t defaultCapacity = 512 * 1024;
-        static const size_t commitSize = 16 * 1024;
         // Allow 8k of excess registers before we start trying to reap the stack
         static const ptrdiff_t maxExcessCapacity = 8 * 1024;
 
-        JSStack(VM&, size_t capacity = defaultCapacity);
-        ~JSStack();
+        JSStack(VM&);
         
-        void gatherConservativeRoots(ConservativeRoots&);
-        void gatherConservativeRoots(ConservativeRoots&, JITStubRoutineSet&, DFGCodeBlocks&);
-
-        Register* begin() const { return static_cast<Register*>(m_reservation.base()); }
-        Register* end() const { return m_end; }
-        size_t size() const { return end() - begin(); }
+        bool ensureCapacityFor(Register* newTopOfStack);
 
-        bool grow(Register*);
-        
+        bool containsAddress(Register* address) { return (lowAddress() <= address && address < highAddress()); }
         static size_t committedByteCount();
-        static void initializeThreading();
 
-        Register* const * addressOfEnd() const
-        {
-            return &m_end;
-        }
+#if ENABLE(JIT)
+        void gatherConservativeRoots(ConservativeRoots&, JITStubRoutineSet&, CodeBlockSet&) { }
+        void sanitizeStack() { }
+#else
+        ~JSStack();
 
-        Register* getTopOfFrame(CallFrame*);
-        Register* getStartOfFrame(CallFrame*);
-        Register* getTopOfStack();
+        void gatherConservativeRoots(ConservativeRoots&, JITStubRoutineSet&, CodeBlockSet&);
+        void sanitizeStack();
 
-        CallFrame* pushFrame(CallFrame* callerFrame, class CodeBlock*,
-            JSScope*, int argsCount, JSObject* callee);
+        Register* baseOfStack() const
+        {
+            return highAddress() - 1;
+        }
 
-        void popFrame(CallFrame*);
+        size_t size() const { return highAddress() - lowAddress(); }
 
-        void enableErrorStackReserve();
-        void disableErrorStackReserve();
+        void setReservedZoneSize(size_t);
 
-#if ENABLE(DEBUG_JSSTACK)
-        void installFence(CallFrame*, const char *function = "", int lineNo = 0);
-        void validateFence(CallFrame*, const char *function = "", int lineNo = 0);
-        static const int FenceSize = 4;
-#else // !ENABLE(DEBUG_JSSTACK)
-        void installFence(CallFrame*, const char* = "", int = 0) { }
-        void validateFence(CallFrame*, const char* = "", int = 0) { }
-#endif // !ENABLE(DEBUG_JSSTACK)
+        inline Register* topOfStack();
+#endif // ENABLE(JIT)
 
     private:
-        Register* reservationEnd() const
+
+#if !ENABLE(JIT)
+        Register* lowAddress() const
         {
-            char* base = static_cast<char*>(m_reservation.base());
-            char* reservationEnd = base + m_reservation.size();
-            return reinterpret_cast_ptr<Register*>(reservationEnd);
+            return m_end + 1;
         }
 
-#if ENABLE(DEBUG_JSSTACK)
-        static JSValue generateFenceValue(size_t argIndex);
-        void installTrapsAfterFrame(CallFrame*);
+        Register* highAddress() const
+        {
+            return reinterpret_cast_ptr<Register*>(static_cast<char*>(m_reservation.base()) + m_reservation.size());
+        }
 #else
-        void installTrapsAfterFrame(CallFrame*) { }
-#endif
+        Register* lowAddress() const;
+        Register* highAddress() const;
+#endif // !ENABLE(JIT)
+
+#if !ENABLE(JIT)
+        inline Register* topOfFrameFor(CallFrame*);
+
+        Register* reservationTop() const
+        {
+            char* reservationTop = static_cast<char*>(m_reservation.base());
+            return reinterpret_cast_ptr<Register*>(reservationTop);
+        }
 
-        bool growSlowCase(Register*);
-        void shrink(Register*);
+        bool grow(Register* newTopOfStack);
+        bool growSlowCase(Register* newTopOfStack);
+        void shrink(Register* newTopOfStack);
         void releaseExcessCapacity();
         void addToCommittedByteCount(long);
 
+        void setStackLimit(Register* newTopOfStack);
+#endif // !ENABLE(JIT)
+
+        VM& m_vm;
+        CallFrame*& m_topCallFrame;
+#if !ENABLE(JIT)
         Register* m_end;
-        Register* m_commitEnd;
-        Register* m_useableEnd;
+        Register* m_commitTop;
         PageReservation m_reservation;
-        CallFrame*& m_topCallFrame;
+        Register* m_lastStackTop;
+        ptrdiff_t m_reservedZoneSizeInRegisters;
+#endif // !ENABLE(JIT)
 
         friend class LLIntOffsetsExtractor;
     };
 
-    inline void JSStack::shrink(Register* newEnd)
-    {
-        if (newEnd >= m_end)
-            return;
-        m_end = newEnd;
-        if (m_end == m_reservation.base() && (m_commitEnd - begin()) >= maxExcessCapacity)
-            releaseExcessCapacity();
-    }
-
-    inline bool JSStack::grow(Register* newEnd)
-    {
-        if (newEnd <= m_end)
-            return true;
-        return growSlowCase(newEnd);
-    }
-
 } // namespace JSC
 
 #endif // JSStack_h
diff --git a/Source/JavaScriptCore/interpreter/JSStackInlines.h b/Source/JavaScriptCore/interpreter/JSStackInlines.h
index d316b5992..69508ab5d 100644
--- a/Source/JavaScriptCore/interpreter/JSStackInlines.h
+++ b/Source/JavaScriptCore/interpreter/JSStackInlines.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012 Apple Inc. All rights reserved.
+ * Copyright (C) 2012, 2013, 2014 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -29,202 +29,65 @@
 #include "CallFrame.h"
 #include "CodeBlock.h"
 #include "JSStack.h"
+#include "VM.h"
 
 namespace JSC {
 
-inline Register* JSStack::getTopOfFrame(CallFrame* frame)
+inline bool JSStack::ensureCapacityFor(Register* newTopOfStack)
 {
-    if (UNLIKELY(!frame))
-        return begin();
-    return frame->frameExtent();
-}
-
-inline Register* JSStack::getTopOfStack()
-{
-    return getTopOfFrame(m_topCallFrame);
+#if !ENABLE(JIT)
+    return grow(newTopOfStack);
+#else
+    ASSERT(wtfThreadData().stack().isGrowingDownward());
+    return newTopOfStack >= m_vm.stackLimit();
+#endif
 }
 
-inline Register* JSStack::getStartOfFrame(CallFrame* frame)
-{
-    CallFrame* callerFrame = frame->callerFrameNoFlags();
-    return getTopOfFrame(callerFrame);
-}
+#if !ENABLE(JIT)
 
-inline CallFrame* JSStack::pushFrame(CallFrame* callerFrame,
-    class CodeBlock* codeBlock, JSScope* scope, int argsCount, JSObject* callee)
+inline Register* JSStack::topOfFrameFor(CallFrame* frame)
 {
-    ASSERT(!!scope);
-    Register* oldEnd = getTopOfStack();
-
-    // Ensure that we have enough space for the parameters:
-    size_t paddedArgsCount = argsCount;
-    if (codeBlock) {
-        size_t numParameters = codeBlock->numParameters();
-        if (paddedArgsCount < numParameters)
-            paddedArgsCount = numParameters;
-    }
-
-    Register* newCallFrameSlot = oldEnd + paddedArgsCount + JSStack::CallFrameHeaderSize;
-#if ENABLE(DEBUG_JSSTACK)
-    newCallFrameSlot += JSStack::FenceSize;
-#endif
-    Register* newEnd = newCallFrameSlot;
-    if (!!codeBlock)
-        newEnd += codeBlock->m_numCalleeRegisters;
-
-    // Ensure that we have the needed stack capacity to push the new frame:
-    if (!grow(newEnd))
-        return 0;
-
-    // Compute the address of the new frame for this invocation:
-    CallFrame* newCallFrame = CallFrame::create(newCallFrameSlot);
-    ASSERT(!!newCallFrame);
-
-    // The caller frame should always be the real previous frame on the stack,
-    // and not a potential GlobalExec that was passed in. Point callerFrame to
-    // the top frame on the stack.
-    callerFrame = m_topCallFrame;
-
-    // Initialize the frame header:
-    newCallFrame->init(codeBlock, 0, scope,
-        callerFrame->addHostCallFrameFlag(), argsCount, callee);
-
-    ASSERT(!!newCallFrame->scope());
-
-    // Pad additional args if needed:
-    // Note: we need to subtract 1 from argsCount and paddedArgsCount to
-    // exclude the this pointer.
-    for (size_t i = argsCount-1; i < paddedArgsCount-1; ++i)
-        newCallFrame->setArgument(i, jsUndefined());
-
-    installFence(newCallFrame, __FUNCTION__, __LINE__);
-    validateFence(newCallFrame, __FUNCTION__, __LINE__);
-    installTrapsAfterFrame(newCallFrame);
-
-    // Push the new frame:
-    m_topCallFrame = newCallFrame;
-
-    return newCallFrame;
+    if (UNLIKELY(!frame))
+        return baseOfStack();
+    return frame->topOfFrame() - 1;
 }
 
-inline void JSStack::popFrame(CallFrame* frame)
+inline Register* JSStack::topOfStack()
 {
-    validateFence(frame, __FUNCTION__, __LINE__);
-    CallFrame* callerFrame = frame->callerFrameNoFlags();
-
-    // Pop to the caller:
-    m_topCallFrame = callerFrame;
-
-    // If we are popping the very first frame from the stack i.e. no more
-    // frames before this, then we can now safely shrink the stack. In
-    // this case, we're shrinking all the way to the beginning since there
-    // are no more frames on the stack.
-    if (!callerFrame)
-        shrink(begin());
-
-    installTrapsAfterFrame(callerFrame);
+    return topOfFrameFor(m_topCallFrame);
 }
 
-
-#if ENABLE(DEBUG_JSSTACK)
-inline JSValue JSStack::generateFenceValue(size_t argIndex)
+inline void JSStack::shrink(Register* newTopOfStack)
 {
-    unsigned fenceBits = 0xfacebad0 | ((argIndex+1) & 0xf);
-    JSValue fenceValue = JSValue(fenceBits);
-    return fenceValue;
+    Register* newEnd = newTopOfStack - 1;
+    if (newEnd >= m_end)
+        return;
+    setStackLimit(newTopOfStack);
+    // Note: Clang complains of an unresolved linkage to maxExcessCapacity if
+    // invoke std::max() with it as an argument. To work around this, we first
+    // assign the constant to a local variable, and use the local instead.
+    ptrdiff_t maxExcessCapacity = JSStack::maxExcessCapacity;
+    ptrdiff_t maxExcessInRegisters = std::max(maxExcessCapacity, m_reservedZoneSizeInRegisters);
+    if (m_end == baseOfStack() && (highAddress() - m_commitTop) >= maxExcessInRegisters)
+        releaseExcessCapacity();
 }
 
-// The JSStack fences mechanism works as follows:
-// 1. A fence is a number (JSStack::FenceSize) of JSValues that are initialized
-//    with values generated by JSStack::generateFenceValue().
-// 2. When pushFrame() is called, the fence is installed after the max extent
-//    of the previous topCallFrame and the last arg of the new frame:
-//
-//                     | ...                                  |
-//                     |--------------------------------------|
-//                     | Frame Header of previous frame       |
-//                     |--------------------------------------|
-//    topCallFrame --> |                                      |
-//                     | Locals of previous frame             |
-//                     |--------------------------------------|
-//                     | *** the Fence ***                    |
-//                     |--------------------------------------|
-//                     | Args of new frame                    |
-//                     |--------------------------------------|
-//                     | Frame Header of new frame            |
-//                     |--------------------------------------|
-//           frame --> | Locals of new frame                  |
-//                     |                                      |
-//
-// 3. In popFrame() and elsewhere, we can call JSStack::validateFence() to
-//    assert that the fence contains the values we expect.
-
-inline void JSStack::installFence(CallFrame* frame, const char *function, int lineNo)
+inline bool JSStack::grow(Register* newTopOfStack)
 {
-    UNUSED_PARAM(function);
-    UNUSED_PARAM(lineNo);
-    Register* startOfFrame = getStartOfFrame(frame);
-
-    // The last argIndex is at:
-    size_t maxIndex = frame->argIndexForRegister(startOfFrame) + 1;
-    size_t startIndex = maxIndex - FenceSize;
-    for (size_t i = startIndex; i < maxIndex; ++i) {
-        JSValue fenceValue = generateFenceValue(i);
-        frame->setArgument(i, fenceValue);
-    }
+    Register* newEnd = newTopOfStack - 1;
+    if (newEnd >= m_end)
+        return true;
+    return growSlowCase(newTopOfStack);
 }
 
-inline void JSStack::validateFence(CallFrame* frame, const char *function, int lineNo)
+inline void JSStack::setStackLimit(Register* newTopOfStack)
 {
-    UNUSED_PARAM(function);
-    UNUSED_PARAM(lineNo);
-    ASSERT(!!frame->scope());
-    Register* startOfFrame = getStartOfFrame(frame);
-    size_t maxIndex = frame->argIndexForRegister(startOfFrame) + 1;
-    size_t startIndex = maxIndex - FenceSize;
-    for (size_t i = startIndex; i < maxIndex; ++i) {
-        JSValue fenceValue = generateFenceValue(i);
-        JSValue actualValue = frame->getArgumentUnsafe(i);
-        ASSERT(fenceValue == actualValue);
-    }
+    Register* newEnd = newTopOfStack - 1;
+    m_end = newEnd;
+    m_vm.setJSStackLimit(newTopOfStack);
 }
 
-// When debugging the JSStack, we install bad values after the extent of the
-// topCallFrame at the end of pushFrame() and popFrame(). The intention is
-// to trigger crashes in the event that memory in this supposedly unused
-// region is read and consumed without proper initialization. After the trap
-// words are installed, the stack looks like this:
-//
-//                     | ...                         |
-//                     |-----------------------------|
-//                     | Frame Header of frame       |
-//                     |-----------------------------|
-//    topCallFrame --> |                             |
-//                     | Locals of frame             |
-//                     |-----------------------------|
-//                     | *** Trap words ***          |
-//                     |-----------------------------|
-//                     | Unused space ...            |
-//                     | ...                         |
-
-inline void JSStack::installTrapsAfterFrame(CallFrame* frame)
-{
-    Register* topOfFrame = getTopOfFrame(frame);
-    const int sizeOfTrap = 64;
-    int32_t* startOfTrap = reinterpret_cast<int32_t*>(topOfFrame);
-    int32_t* endOfTrap = startOfTrap + sizeOfTrap;
-    int32_t* endOfCommitedMemory = reinterpret_cast<int32_t*>(m_commitEnd);
-
-    // Make sure we're not exceeding the amount of available memory to write to:
-    if (endOfTrap > endOfCommitedMemory)
-        endOfTrap = endOfCommitedMemory;
-
-    // Lay the traps:
-    int32_t* p = startOfTrap;
-    while (p < endOfTrap)
-        *p++ = 0xabadcafe; // A bad word to trigger a crash if deref'ed.
-}
-#endif // ENABLE(DEBUG_JSSTACK)
+#endif // !ENABLE(JIT)
 
 } // namespace JSC
 
diff --git a/Source/JavaScriptCore/interpreter/ProtoCallFrame.cpp b/Source/JavaScriptCore/interpreter/ProtoCallFrame.cpp
new file mode 100644
index 000000000..eb80b2c23
--- /dev/null
+++ b/Source/JavaScriptCore/interpreter/ProtoCallFrame.cpp
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2013 Apple Inc. All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "ProtoCallFrame.h"
+
+#include "CodeBlock.h"
+#include "JSCInlines.h"
+#include "StackAlignment.h"
+
+namespace JSC {
+
+void ProtoCallFrame::init(CodeBlock* codeBlock, JSObject* callee, JSValue thisValue, int argCountIncludingThis, JSValue* otherArgs)
+{
+    this->args = otherArgs;
+    this->setCodeBlock(codeBlock);
+    this->setCallee(callee);
+    this->setArgumentCountIncludingThis(argCountIncludingThis);
+    if (codeBlock && argCountIncludingThis < codeBlock->numParameters())
+        this->arityMissMatch = true;
+    else
+        this->arityMissMatch = false;
+
+    // Round up argCountIncludingThis to keep the stack frame size aligned.
+    size_t paddedArgsCount = roundArgumentCountToAlignFrame(argCountIncludingThis);
+    this->setPaddedArgCount(paddedArgsCount);
+    this->clearCurrentVPC();
+    this->setThisValue(thisValue);
+}
+
+} // namespace JSC
diff --git a/Source/JavaScriptCore/interpreter/ProtoCallFrame.h b/Source/JavaScriptCore/interpreter/ProtoCallFrame.h
new file mode 100644
index 000000000..af33a3072
--- /dev/null
+++ b/Source/JavaScriptCore/interpreter/ProtoCallFrame.h
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2013 Apple Inc. All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ProtoCallFrame_h
+#define ProtoCallFrame_h
+
+#include "Register.h"
+
+namespace JSC {
+
+struct ProtoCallFrame {
+    Register codeBlockValue;
+    Register calleeValue;
+    Register argCountAndCodeOriginValue;
+    Register thisArg;
+    uint32_t paddedArgCount;
+    bool arityMissMatch;
+    JSValue *args;
+
+    void init(CodeBlock*, JSObject*, JSValue, int, JSValue* otherArgs = 0);
+
+    CodeBlock* codeBlock() const { return codeBlockValue.Register::codeBlock(); }
+    void setCodeBlock(CodeBlock* codeBlock) { codeBlockValue = codeBlock; }
+
+    JSObject* callee() const { return calleeValue.Register::object(); }
+    void setCallee(JSObject* callee) { calleeValue = callee; }
+
+    int argumentCountIncludingThis() const { return argCountAndCodeOriginValue.payload(); }
+    int argumentCount() const { return argumentCountIncludingThis() - 1; }
+    void setArgumentCountIncludingThis(int count) { argCountAndCodeOriginValue.payload() = count; }
+    void setPaddedArgCount(uint32_t argCount) { paddedArgCount = argCount; }
+
+    void clearCurrentVPC() { argCountAndCodeOriginValue.tag() = 0; }
+    
+    JSValue thisValue() const { return thisArg.Register::jsValue(); }
+    void setThisValue(JSValue value) { thisArg = value; }
+
+    bool needArityCheck() { return arityMissMatch; }
+
+    JSValue argument(size_t argumentIndex)
+    {
+        ASSERT(static_cast<int>(argumentIndex) < argumentCount());
+        return args[argumentIndex];
+    }
+    void setArgument(size_t argumentIndex, JSValue value)
+    {
+        ASSERT(static_cast<int>(argumentIndex) < argumentCount());
+        args[argumentIndex] = value;
+    }
+};
+
+} // namespace JSC
+
+#endif // ProtoCallFrame_h
diff --git a/Source/JavaScriptCore/interpreter/Register.h b/Source/JavaScriptCore/interpreter/Register.h
index bc2335689..c0396c966 100644
--- a/Source/JavaScriptCore/interpreter/Register.h
+++ b/Source/JavaScriptCore/interpreter/Register.h
@@ -10,7 +10,7 @@
  * 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.
  *
@@ -37,14 +37,10 @@ namespace JSC {
 
     class CodeBlock;
     class ExecState;
-    class JSActivation;
+    class JSLexicalEnvironment;
     class JSObject;
-    class JSPropertyNameIterator;
     class JSScope;
 
-    struct InlineCallFrame;
-    struct Instruction;
-
     typedef ExecState CallFrame;
 
     class Register {
@@ -55,28 +51,29 @@ namespace JSC {
         Register(const JSValue&);
         Register& operator=(const JSValue&);
         JSValue jsValue() const;
+        JSValue asanUnsafeJSValue() const;
         EncodedJSValue encodedJSValue() const;
         
         Register& operator=(CallFrame*);
         Register& operator=(CodeBlock*);
         Register& operator=(JSScope*);
-        Register& operator=(Instruction*);
-        Register& operator=(InlineCallFrame*);
+        Register& operator=(JSObject*);
 
         int32_t i() const;
-        JSActivation* activation() const;
         CallFrame* callFrame() const;
         CodeBlock* codeBlock() const;
-        JSObject* function() const;
-        JSPropertyNameIterator* propertyNameIterator() const;
+        CodeBlock* asanUnsafeCodeBlock() const;
+        JSObject* object() const;
         JSScope* scope() const;
-        Instruction* vPC() const;
-        InlineCallFrame* asInlineCallFrame() const;
         int32_t unboxedInt32() const;
+        int64_t unboxedInt52() const;
+        int64_t unboxedStrictInt52() const;
         bool unboxedBoolean() const;
+        double unboxedDouble() const;
         JSCell* unboxedCell() const;
         int32_t payload() const;
         int32_t tag() const;
+        int32_t unsafeTag() const;
         int32_t& payload();
         int32_t& tag();
 
@@ -86,16 +83,14 @@ namespace JSC {
             return r;
         }
 
-        static Register withCallee(JSObject* callee);
-
     private:
         union {
             EncodedJSValue value;
             CallFrame* callFrame;
             CodeBlock* codeBlock;
-            Instruction* vPC;
-            InlineCallFrame* inlineCallFrame;
             EncodedValueDescriptor encodedValue;
+            double number;
+            int64_t integer;
         } u;
     };
 
@@ -117,6 +112,12 @@ namespace JSC {
         return *this;
     }
 
+    // FIXME (rdar://problem/19379214): ASan only needs to be suppressed for Register::jsValue() when called from prepareOSREntry(), but there is currently no way to express this short of adding a separate copy of the function.
+    SUPPRESS_ASAN ALWAYS_INLINE JSValue Register::asanUnsafeJSValue() const
+    {
+        return JSValue::decode(u.value);
+    }
+
     ALWAYS_INLINE JSValue Register::jsValue() const
     {
         return JSValue::decode(u.value);
@@ -141,18 +142,6 @@ namespace JSC {
         return *this;
     }
 
-    ALWAYS_INLINE Register& Register::operator=(Instruction* vPC)
-    {
-        u.vPC = vPC;
-        return *this;
-    }
-
-    ALWAYS_INLINE Register& Register::operator=(InlineCallFrame* inlineCallFrame)
-    {
-        u.inlineCallFrame = inlineCallFrame;
-        return *this;
-    }
-
     ALWAYS_INLINE int32_t Register::i() const
     {
         return jsValue().asInt32();
@@ -168,26 +157,36 @@ namespace JSC {
         return u.codeBlock;
     }
 
-    ALWAYS_INLINE Instruction* Register::vPC() const
+    SUPPRESS_ASAN ALWAYS_INLINE CodeBlock* Register::asanUnsafeCodeBlock() const
     {
-        return u.vPC;
+        return u.codeBlock;
     }
 
-    ALWAYS_INLINE InlineCallFrame* Register::asInlineCallFrame() const
-    {
-        return u.inlineCallFrame;
-    }
-        
     ALWAYS_INLINE int32_t Register::unboxedInt32() const
     {
         return payload();
     }
 
+    ALWAYS_INLINE int64_t Register::unboxedInt52() const
+    {
+        return u.integer >> JSValue::int52ShiftAmount;
+    }
+
+    ALWAYS_INLINE int64_t Register::unboxedStrictInt52() const
+    {
+        return u.integer;
+    }
+
     ALWAYS_INLINE bool Register::unboxedBoolean() const
     {
         return !!payload();
     }
 
+    ALWAYS_INLINE double Register::unboxedDouble() const
+    {
+        return u.number;
+    }
+
     ALWAYS_INLINE JSCell* Register::unboxedCell() const
     {
 #if USE(JSVALUE64)
@@ -207,6 +206,11 @@ namespace JSC {
         return u.encodedValue.asBits.tag;
     }
 
+    SUPPRESS_ASAN ALWAYS_INLINE int32_t Register::unsafeTag() const
+    {
+        return u.encodedValue.asBits.tag;
+    }
+
     ALWAYS_INLINE int32_t& Register::payload()
     {
         return u.encodedValue.asBits.payload;
diff --git a/Source/JavaScriptCore/interpreter/StackVisitor.cpp b/Source/JavaScriptCore/interpreter/StackVisitor.cpp
new file mode 100644
index 000000000..c0c03d280
--- /dev/null
+++ b/Source/JavaScriptCore/interpreter/StackVisitor.cpp
@@ -0,0 +1,440 @@
+/*
+ * Copyright (C) 2013, 2015 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#include "config.h"
+#include "StackVisitor.h"
+
+#include "ClonedArguments.h"
+#include "Executable.h"
+#include "InlineCallFrame.h"
+#include "Interpreter.h"
+#include "JSCInlines.h"
+#include <wtf/DataLog.h>
+
+namespace JSC {
+
+StackVisitor::StackVisitor(CallFrame* startFrame)
+{
+    m_frame.m_index = 0;
+    CallFrame* topFrame;
+    if (startFrame) {
+        m_frame.m_VMEntryFrame = startFrame->vm().topVMEntryFrame;
+        topFrame = startFrame->vm().topCallFrame;
+    } else {
+        m_frame.m_VMEntryFrame = 0;
+        topFrame = 0;
+    }
+    m_frame.m_callerIsVMEntryFrame = false;
+    readFrame(topFrame);
+
+    // Find the frame the caller wants to start unwinding from.
+    while (m_frame.callFrame() && m_frame.callFrame() != startFrame)
+        gotoNextFrame();
+}
+
+void StackVisitor::gotoNextFrame()
+{
+#if ENABLE(DFG_JIT)
+    if (m_frame.isInlinedFrame()) {
+        InlineCallFrame* inlineCallFrame = m_frame.inlineCallFrame();
+        CodeOrigin* callerCodeOrigin = inlineCallFrame->getCallerSkippingTailCalls();
+        if (!callerCodeOrigin) {
+            while (inlineCallFrame) {
+                readInlinedFrame(m_frame.callFrame(), &inlineCallFrame->directCaller);
+                inlineCallFrame = m_frame.inlineCallFrame();
+            }
+            m_frame.m_VMEntryFrame = m_frame.m_CallerVMEntryFrame;
+            readFrame(m_frame.callerFrame());
+        } else
+            readInlinedFrame(m_frame.callFrame(), callerCodeOrigin);
+        return;
+    }
+#endif // ENABLE(DFG_JIT)
+    m_frame.m_VMEntryFrame = m_frame.m_CallerVMEntryFrame;
+    readFrame(m_frame.callerFrame());
+}
+
+void StackVisitor::unwindToMachineCodeBlockFrame()
+{
+#if ENABLE(DFG_JIT)
+    while (m_frame.isInlinedFrame())
+        gotoNextFrame();
+#endif
+}
+
+void StackVisitor::readFrame(CallFrame* callFrame)
+{
+    if (!callFrame) {
+        m_frame.setToEnd();
+        return;
+    }
+
+#if !ENABLE(DFG_JIT)
+    readNonInlinedFrame(callFrame);
+
+#else // !ENABLE(DFG_JIT)
+    // If the frame doesn't have a code block, then it's not a DFG frame.
+    // Hence, we're not at an inlined frame.
+    CodeBlock* codeBlock = callFrame->codeBlock();
+    if (!codeBlock) {
+        readNonInlinedFrame(callFrame);
+        return;
+    }
+
+    // If the code block does not have any code origins, then there's no
+    // inlining. Hence, we're not at an inlined frame.
+    if (!codeBlock->hasCodeOrigins()) {
+        readNonInlinedFrame(callFrame);
+        return;
+    }
+
+    CallSiteIndex index = callFrame->callSiteIndex();
+    ASSERT(codeBlock->canGetCodeOrigin(index));
+    if (!codeBlock->canGetCodeOrigin(index)) {
+        // See assertion above. In release builds, we try to protect ourselves
+        // from crashing even though stack walking will be goofed up.
+        m_frame.setToEnd();
+        return;
+    }
+
+    CodeOrigin codeOrigin = codeBlock->codeOrigin(index);
+    if (!codeOrigin.inlineCallFrame) {
+        readNonInlinedFrame(callFrame, &codeOrigin);
+        return;
+    }
+
+    readInlinedFrame(callFrame, &codeOrigin);
+#endif // !ENABLE(DFG_JIT)
+}
+
+void StackVisitor::readNonInlinedFrame(CallFrame* callFrame, CodeOrigin* codeOrigin)
+{
+    m_frame.m_callFrame = callFrame;
+    m_frame.m_argumentCountIncludingThis = callFrame->argumentCountIncludingThis();
+    m_frame.m_CallerVMEntryFrame = m_frame.m_VMEntryFrame;
+    m_frame.m_callerFrame = callFrame->callerFrame(m_frame.m_CallerVMEntryFrame);
+    m_frame.m_callerIsVMEntryFrame = m_frame.m_CallerVMEntryFrame != m_frame.m_VMEntryFrame;
+    m_frame.m_callee = callFrame->callee();
+    m_frame.m_codeBlock = callFrame->codeBlock();
+    m_frame.m_bytecodeOffset = !m_frame.codeBlock() ? 0
+        : codeOrigin ? codeOrigin->bytecodeIndex
+        : callFrame->bytecodeOffset();
+#if ENABLE(DFG_JIT)
+    m_frame.m_inlineCallFrame = 0;
+#endif
+}
+
+#if ENABLE(DFG_JIT)
+static int inlinedFrameOffset(CodeOrigin* codeOrigin)
+{
+    InlineCallFrame* inlineCallFrame = codeOrigin->inlineCallFrame;
+    int frameOffset = inlineCallFrame ? inlineCallFrame->stackOffset : 0;
+    return frameOffset;
+}
+
+void StackVisitor::readInlinedFrame(CallFrame* callFrame, CodeOrigin* codeOrigin)
+{
+    ASSERT(codeOrigin);
+
+    int frameOffset = inlinedFrameOffset(codeOrigin);
+    bool isInlined = !!frameOffset;
+    if (isInlined) {
+        InlineCallFrame* inlineCallFrame = codeOrigin->inlineCallFrame;
+
+        m_frame.m_callFrame = callFrame;
+        m_frame.m_inlineCallFrame = inlineCallFrame;
+        if (inlineCallFrame->argumentCountRegister.isValid())
+            m_frame.m_argumentCountIncludingThis = callFrame->r(inlineCallFrame->argumentCountRegister.offset()).unboxedInt32();
+        else
+            m_frame.m_argumentCountIncludingThis = inlineCallFrame->arguments.size();
+        m_frame.m_codeBlock = inlineCallFrame->baselineCodeBlock.get();
+        m_frame.m_bytecodeOffset = codeOrigin->bytecodeIndex;
+
+        JSFunction* callee = inlineCallFrame->calleeForCallFrame(callFrame);
+        m_frame.m_callee = callee;
+        ASSERT(m_frame.callee());
+
+        // The callerFrame just needs to be non-null to indicate that we
+        // haven't reached the last frame yet. Setting it to the root
+        // frame (i.e. the callFrame that this inlined frame is called from)
+        // would work just fine.
+        m_frame.m_callerFrame = callFrame;
+        return;
+    }
+
+    readNonInlinedFrame(callFrame, codeOrigin);
+}
+#endif // ENABLE(DFG_JIT)
+
+StackVisitor::Frame::CodeType StackVisitor::Frame::codeType() const
+{
+    if (!isJSFrame())
+        return CodeType::Native;
+
+    switch (codeBlock()->codeType()) {
+    case EvalCode:
+        return CodeType::Eval;
+    case ModuleCode:
+        return CodeType::Module;
+    case FunctionCode:
+        return CodeType::Function;
+    case GlobalCode:
+        return CodeType::Global;
+    }
+    RELEASE_ASSERT_NOT_REACHED();
+    return CodeType::Global;
+}
+
+String StackVisitor::Frame::functionName()
+{
+    String traceLine;
+    JSObject* callee = this->callee();
+
+    switch (codeType()) {
+    case CodeType::Eval:
+        traceLine = ASCIILiteral("eval code");
+        break;
+    case CodeType::Module:
+        traceLine = ASCIILiteral("module code");
+        break;
+    case CodeType::Native:
+        if (callee)
+            traceLine = getCalculatedDisplayName(callFrame(), callee).impl();
+        break;
+    case CodeType::Function:
+        traceLine = getCalculatedDisplayName(callFrame(), callee).impl();
+        break;
+    case CodeType::Global:
+        traceLine = ASCIILiteral("global code");
+        break;
+    }
+    return traceLine.isNull() ? emptyString() : traceLine;
+}
+
+String StackVisitor::Frame::sourceURL()
+{
+    String traceLine;
+
+    switch (codeType()) {
+    case CodeType::Eval:
+    case CodeType::Module:
+    case CodeType::Function:
+    case CodeType::Global: {
+        String sourceURL = codeBlock()->ownerScriptExecutable()->sourceURL();
+        if (!sourceURL.isEmpty())
+            traceLine = sourceURL.impl();
+        break;
+    }
+    case CodeType::Native:
+        traceLine = ASCIILiteral("[native code]");
+        break;
+    }
+    return traceLine.isNull() ? emptyString() : traceLine;
+}
+
+String StackVisitor::Frame::toString()
+{
+    StringBuilder traceBuild;
+    String functionName = this->functionName();
+    String sourceURL = this->sourceURL();
+    traceBuild.append(functionName);
+    if (!sourceURL.isEmpty()) {
+        if (!functionName.isEmpty())
+            traceBuild.append('@');
+        traceBuild.append(sourceURL);
+        if (isJSFrame()) {
+            unsigned line = 0;
+            unsigned column = 0;
+            computeLineAndColumn(line, column);
+            traceBuild.append(':');
+            traceBuild.appendNumber(line);
+            traceBuild.append(':');
+            traceBuild.appendNumber(column);
+        }
+    }
+    return traceBuild.toString().impl();
+}
+
+ClonedArguments* StackVisitor::Frame::createArguments()
+{
+    ASSERT(m_callFrame);
+    CallFrame* physicalFrame = m_callFrame;
+    ClonedArguments* arguments;
+    ArgumentsMode mode;
+    if (Options::useFunctionDotArguments())
+        mode = ArgumentsMode::Cloned;
+    else
+        mode = ArgumentsMode::FakeValues;
+#if ENABLE(DFG_JIT)
+    if (isInlinedFrame()) {
+        ASSERT(m_inlineCallFrame);
+        arguments = ClonedArguments::createWithInlineFrame(physicalFrame, physicalFrame, m_inlineCallFrame, mode);
+    } else 
+#endif
+        arguments = ClonedArguments::createWithMachineFrame(physicalFrame, physicalFrame, mode);
+    return arguments;
+}
+
+void StackVisitor::Frame::computeLineAndColumn(unsigned& line, unsigned& column)
+{
+    CodeBlock* codeBlock = this->codeBlock();
+    if (!codeBlock) {
+        line = 0;
+        column = 0;
+        return;
+    }
+
+    int divot = 0;
+    int unusedStartOffset = 0;
+    int unusedEndOffset = 0;
+    unsigned divotLine = 0;
+    unsigned divotColumn = 0;
+    retrieveExpressionInfo(divot, unusedStartOffset, unusedEndOffset, divotLine, divotColumn);
+
+    line = divotLine + codeBlock->ownerScriptExecutable()->firstLine();
+    column = divotColumn + (divotLine ? 1 : codeBlock->firstLineColumnOffset());
+
+    if (codeBlock->ownerScriptExecutable()->hasOverrideLineNumber())
+        line = codeBlock->ownerScriptExecutable()->overrideLineNumber();
+}
+
+void StackVisitor::Frame::retrieveExpressionInfo(int& divot, int& startOffset, int& endOffset, unsigned& line, unsigned& column)
+{
+    CodeBlock* codeBlock = this->codeBlock();
+    codeBlock->unlinkedCodeBlock()->expressionRangeForBytecodeOffset(bytecodeOffset(), divot, startOffset, endOffset, line, column);
+    divot += codeBlock->sourceOffset();
+}
+
+void StackVisitor::Frame::setToEnd()
+{
+    m_callFrame = 0;
+#if ENABLE(DFG_JIT)
+    m_inlineCallFrame = 0;
+#endif
+}
+
+static void printIndents(int levels)
+{
+    while (levels--)
+        dataLogFString("   ");
+}
+
+template<typename... Types>
+void log(unsigned indent, const Types&... values)
+{
+    printIndents(indent);
+    dataLog(values...);
+}
+
+template<typename... Types>
+void logF(unsigned indent, const char* format, const Types&... values)
+{
+    printIndents(indent);
+
+#if COMPILER(GCC_OR_CLANG)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+#pragma GCC diagnostic ignored "-Wmissing-format-attribute"
+#endif
+
+    dataLogF(format, values...);
+
+#if COMPILER(GCC_OR_CLANG)
+#pragma GCC diagnostic pop
+#endif
+}
+
+void StackVisitor::Frame::print(int indent)
+{
+    if (!this->callFrame()) {
+        log(indent, "frame 0x0\n");
+        return;
+    }
+
+    CodeBlock* codeBlock = this->codeBlock();
+    logF(indent, "frame %p {\n", this->callFrame());
+
+    {
+        indent++;
+
+        CallFrame* callFrame = m_callFrame;
+        CallFrame* callerFrame = this->callerFrame();
+        void* returnPC = callFrame->hasReturnPC() ? callFrame->returnPC().value() : nullptr;
+
+        log(indent, "name: ", functionName(), "\n");
+        log(indent, "sourceURL: ", sourceURL(), "\n");
+
+        bool isInlined = false;
+#if ENABLE(DFG_JIT)
+        isInlined = isInlinedFrame();
+        log(indent, "isInlinedFrame: ", isInlinedFrame(), "\n");
+        if (isInlinedFrame())
+            logF(indent, "InlineCallFrame: %p\n", m_inlineCallFrame);
+#endif
+
+        logF(indent, "callee: %p\n", callee());
+        logF(indent, "returnPC: %p\n", returnPC);
+        logF(indent, "callerFrame: %p\n", callerFrame);
+        unsigned locationRawBits = callFrame->callSiteAsRawBits();
+        logF(indent, "rawLocationBits: %u 0x%x\n", locationRawBits, locationRawBits);
+        logF(indent, "codeBlock: %p ", codeBlock);
+        if (codeBlock)
+            dataLog(*codeBlock);
+        dataLog("\n");
+        if (codeBlock && !isInlined) {
+            indent++;
+
+            if (callFrame->callSiteBitsAreBytecodeOffset()) {
+                unsigned bytecodeOffset = callFrame->bytecodeOffset();
+                log(indent, "bytecodeOffset: ", bytecodeOffset, " of ", codeBlock->instructions().size(), "\n");
+#if ENABLE(DFG_JIT)
+            } else {
+                log(indent, "hasCodeOrigins: ", codeBlock->hasCodeOrigins(), "\n");
+                if (codeBlock->hasCodeOrigins()) {
+                    CallSiteIndex callSiteIndex = callFrame->callSiteIndex();
+                    log(indent, "callSiteIndex: ", callSiteIndex.bits(), " of ", codeBlock->codeOrigins().size(), "\n");
+
+                    JITCode::JITType jitType = codeBlock->jitType();
+                    if (jitType != JITCode::FTLJIT) {
+                        JITCode* jitCode = codeBlock->jitCode().get();
+                        logF(indent, "jitCode: %p start %p end %p\n", jitCode, jitCode->start(), jitCode->end());
+                    }
+                }
+#endif
+            }
+            unsigned line = 0;
+            unsigned column = 0;
+            computeLineAndColumn(line, column);
+            log(indent, "line: ", line, "\n");
+            log(indent, "column: ", column, "\n");
+
+            indent--;
+        }
+        indent--;
+    }
+    log(indent, "}\n");
+}
+
+} // namespace JSC
diff --git a/Source/JavaScriptCore/interpreter/StackVisitor.h b/Source/JavaScriptCore/interpreter/StackVisitor.h
new file mode 100644
index 000000000..bbf37fe9c
--- /dev/null
+++ b/Source/JavaScriptCore/interpreter/StackVisitor.h
@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 2013, 2015 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
+ */
+
+#ifndef StackVisitor_h
+#define StackVisitor_h
+
+#include "VMEntryRecord.h"
+#include <wtf/text/WTFString.h>
+
+namespace JSC {
+
+struct CodeOrigin;
+struct InlineCallFrame;
+
+class CodeBlock;
+class ExecState;
+class JSFunction;
+class JSObject;
+class JSScope;
+class ClonedArguments;
+class Register;
+
+typedef ExecState CallFrame;
+
+class StackVisitor {
+public:
+    class Frame {
+    public:
+        enum CodeType {
+            Global,
+            Eval,
+            Function,
+            Module,
+            Native
+        };
+
+        size_t index() const { return m_index; }
+        size_t argumentCountIncludingThis() const { return m_argumentCountIncludingThis; }
+        bool callerIsVMEntryFrame() const { return m_callerIsVMEntryFrame; }
+        CallFrame* callerFrame() const { return m_callerFrame; }
+        JSObject* callee() const { return m_callee; }
+        CodeBlock* codeBlock() const { return m_codeBlock; }
+        unsigned bytecodeOffset() const { return m_bytecodeOffset; }
+#if ENABLE(DFG_JIT)
+        InlineCallFrame* inlineCallFrame() const { return m_inlineCallFrame; }
+#endif
+
+        bool isJSFrame() const { return !!codeBlock(); }
+#if ENABLE(DFG_JIT)
+        bool isInlinedFrame() const { return !!m_inlineCallFrame; }
+#endif
+
+        JS_EXPORT_PRIVATE String functionName();
+        JS_EXPORT_PRIVATE String sourceURL();
+        JS_EXPORT_PRIVATE String toString();
+
+        CodeType codeType() const;
+        JS_EXPORT_PRIVATE void computeLineAndColumn(unsigned& line, unsigned& column);
+
+        ClonedArguments* createArguments();
+        VMEntryFrame* vmEntryFrame() const { return m_VMEntryFrame; }
+        CallFrame* callFrame() const { return m_callFrame; }
+        
+        JS_EXPORT_PRIVATE void print(int indentLevel);
+
+    private:
+        Frame() { }
+        ~Frame() { }
+
+        void retrieveExpressionInfo(int& divot, int& startOffset, int& endOffset, unsigned& line, unsigned& column);
+        void setToEnd();
+
+        size_t m_index;
+        size_t m_argumentCountIncludingThis;
+        VMEntryFrame* m_VMEntryFrame;
+        VMEntryFrame* m_CallerVMEntryFrame;
+        CallFrame* m_callerFrame;
+        JSObject* m_callee;
+        CodeBlock* m_codeBlock;
+        unsigned m_bytecodeOffset;
+        bool m_callerIsVMEntryFrame;
+#if ENABLE(DFG_JIT)
+        InlineCallFrame* m_inlineCallFrame;
+#endif
+        CallFrame* m_callFrame;
+
+        friend class StackVisitor;
+    };
+
+    enum Status {
+        Continue = 0,
+        Done = 1
+    };
+
+    // StackVisitor::visit() expects a Functor that implements the following method:
+    //     Status operator()(StackVisitor&);
+
+    template <typename Functor>
+    static void visit(CallFrame* startFrame, Functor& functor)
+    {
+        StackVisitor visitor(startFrame);
+        while (visitor->callFrame()) {
+            Status status = functor(visitor);
+            if (status != Continue)
+                break;
+            visitor.gotoNextFrame();
+        }
+    }
+
+    Frame& operator*() { return m_frame; }
+    ALWAYS_INLINE Frame* operator->() { return &m_frame; }
+    void unwindToMachineCodeBlockFrame();
+
+private:
+    JS_EXPORT_PRIVATE StackVisitor(CallFrame* startFrame);
+
+    JS_EXPORT_PRIVATE void gotoNextFrame();
+
+    void readFrame(CallFrame*);
+    void readNonInlinedFrame(CallFrame*, CodeOrigin* = 0);
+#if ENABLE(DFG_JIT)
+    void readInlinedFrame(CallFrame*, CodeOrigin*);
+#endif
+
+    Frame m_frame;
+};
+
+class CallerFunctor {
+public:
+    CallerFunctor()
+        : m_hasSkippedFirstFrame(false)
+        , m_callerFrame(0)
+    {
+    }
+
+    CallFrame* callerFrame() const { return m_callerFrame; }
+
+    StackVisitor::Status operator()(StackVisitor& visitor)
+    {
+        if (!m_hasSkippedFirstFrame) {
+            m_hasSkippedFirstFrame = true;
+            return StackVisitor::Continue;
+        }
+
+        m_callerFrame = visitor->callFrame();
+        return StackVisitor::Done;
+    }
+    
+private:
+    bool m_hasSkippedFirstFrame;
+    CallFrame* m_callerFrame;
+};
+
+} // namespace JSC
+
+#endif // StackVisitor_h
+
diff --git a/Source/JavaScriptCore/interpreter/VMEntryRecord.h b/Source/JavaScriptCore/interpreter/VMEntryRecord.h
new file mode 100644
index 000000000..9726538fb
--- /dev/null
+++ b/Source/JavaScriptCore/interpreter/VMEntryRecord.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2014 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef VMEntryRecord_h
+#define VMEntryRecord_h
+
+namespace JSC {
+
+typedef void VMEntryFrame;
+
+class ExecState;
+class VM;
+
+struct VMEntryRecord {
+    /*
+     * This record stored in a vmEntryTo{JavaScript,Host} allocated frame. It is allocated on the stack
+     * after callee save registers where local variables would go.
+     */
+    VM* m_vm;
+    ExecState* m_prevTopCallFrame;
+    VMEntryFrame* m_prevTopVMEntryFrame;
+
+    ExecState* prevTopCallFrame() { return m_prevTopCallFrame; }
+    SUPPRESS_ASAN ExecState* unsafePrevTopCallFrame() { return m_prevTopCallFrame; }
+
+    VMEntryFrame* prevTopVMEntryFrame() { return m_prevTopVMEntryFrame; }
+    SUPPRESS_ASAN VMEntryFrame* unsafePrevTopVMEntryFrame() { return m_prevTopVMEntryFrame; }
+};
+
+extern "C" VMEntryRecord* vmEntryRecord(VMEntryFrame*);
+
+} // namespace JSC
+
+#endif // VMEntryRecord_h
diff --git a/Source/JavaScriptCore/interpreter/VMInspector.cpp b/Source/JavaScriptCore/interpreter/VMInspector.cpp
deleted file mode 100644
index 58bc15075..000000000
--- a/Source/JavaScriptCore/interpreter/VMInspector.cpp
+++ /dev/null
@@ -1,573 +0,0 @@
-/*
- * Copyright (C) 2012 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
- */
-
-#include "config.h"
-#include "VMInspector.h"
-
-#if ENABLE(VMINSPECTOR)
-
-#include <stdio.h>
-#include <wtf/ASCIICType.h>
-#include <wtf/text/WTFString.h>
-
-namespace JSC {
-
-const char* VMInspector::getTypeName(JSValue value)
-{
-    if (value.isInt32())
-        return "<Int32>";
-    if (value.isBoolean())
-        return "<Boolean>";
-    if (value.isNull())
-        return "<Empty>";
-    if (value.isUndefined())
-        return "<Undefined>";
-    if (value.isCell())
-        return "<Cell>";
-    if (value.isEmpty())
-        return "<Empty>";
-    return "";
-}
-
-void VMInspector::dumpFrame0(CallFrame* frame)
-{
-    dumpFrame(frame, 0, 0, 0, 0);
-}
-
-void VMInspector::dumpFrame(CallFrame* frame, const char* prefix,
-                            const char* funcName, const char* file, int line)
-{
-    int frameCount = VMInspector::countFrames(frame);
-    if (frameCount < 0)
-        return;
-
-    Instruction* vPC = 0;
-    if (frame->codeBlock())
-        vPC = frame->currentVPC();
-
-    #define CAST reinterpret_cast
-
-    if (prefix)
-        printf("%s ", prefix);
-
-    printf("frame [%d] %p { cb %p:%s, retPC %p:%s, scope %p:%s, callee %p:%s, callerFrame %p:%s, argc %d, vPC %p }",
-        frameCount, frame,
-        CAST<void*>(frame[JSStack::CodeBlock].payload()),
-        getTypeName(frame[JSStack::CodeBlock].jsValue()),
-        CAST<void*>(frame[JSStack::ReturnPC].payload()),
-        getTypeName(frame[JSStack::ReturnPC].jsValue()),
-        CAST<void*>(frame[JSStack::ScopeChain].payload()),
-        getTypeName(frame[JSStack::ScopeChain].jsValue()),
-        CAST<void*>(frame[JSStack::Callee].payload()),
-        getTypeName(frame[JSStack::Callee].jsValue()),
-        CAST<void*>(frame[JSStack::CallerFrame].callFrame()),
-        getTypeName(frame[JSStack::CallerFrame].jsValue()),
-        frame[JSStack::ArgumentCount].payload(),
-        vPC);
-
-    if (funcName || file || (line >= 0)) {
-        printf(" @");
-        if (funcName)
-            printf(" %s", funcName);
-        if (file)
-            printf(" %s", file);
-        if (line >= 0)
-            printf(":%d", line);
-    }
-    printf("\n");
-}
-
-int VMInspector::countFrames(CallFrame* frame)
-{
-    int count = -1;
-    while (frame && !frame->hasHostCallFrameFlag()) {
-        count++;
-        frame = frame->callerFrame();
-    }
-    return count;
-}
-
-
-//============================================================================
-//  class FormatPrinter
-//    - implements functionality to support fprintf.
-//
-//    The FormatPrinter classes do the real formatting and printing.
-//    By default, the superclass FormatPrinter will print to stdout (printf).
-//    Each of the subclass will implement the other ...printf() options.
-//    The subclasses are:
-//
-//        FileFormatPrinter     - fprintf
-//        StringFormatPrinter   - sprintf
-//        StringNFormatPrinter  - snprintf
-
-class FormatPrinter {
-public:
-    virtual ~FormatPrinter() { }
-
-    void print(const char* format, va_list args);
-
-protected:
-    // Low level printers:
-    bool printArg(const char* format, ...);
-    virtual bool printArg(const char* format, va_list args);
-
-    // JS type specific printers:
-    void printWTFString(va_list args, bool verbose);
-};
-
-
-// The public print() function is the real workhorse behind the printf
-// family of functions. print() deciphers the % formatting, translate them
-// to primitive formats, and dispatches to underlying printArg() functions
-// to do the printing.
-// 
-// The non-public internal printArg() function is virtual and is responsible
-// for handling the variations between printf, fprintf, sprintf, and snprintf.
-
-void FormatPrinter::print(const char* format, va_list args)
-{
-    const char* p = format;
-    const char* errorStr;
-
-    // buffer is only used for 2 purposes:
-    // 1. To temporarily hold a copy of normal chars (not needing formatting)
-    //    to be passed to printArg() and printed.
-    //
-    //    The incoming format string may contain a string of normal chars much
-    //    longer than 128, but we handle this by breaking them out to 128 chars
-    //    fragments and printing each fragment before re-using the buffer to
-    //    load up the next fragment.
-    //
-    // 2. To hold a single "%..." format to be passed to printArg() to process
-    //    a single va_arg.
-
-    char buffer[129]; // 128 chars + null terminator.
-    char* end = &buffer[sizeof(buffer) - 1];
-    const char* startOfFormatSpecifier = 0;
-
-    while (true) {
-        char c = *p++;
-        char* curr = buffer;
-
-        // Print leading normal chars:
-        while (c != '\0' && c != '%') {
-            *curr++ = c;
-            if (curr == end) {
-                // Out of buffer space. Flush the fragment, and start over.
-                *curr = '\0';
-                bool success = printArg("%s", buffer);
-                if (!success) {
-                    errorStr = buffer;
-                    goto handleError;
-                }
-                curr = buffer;
-            }
-            c = *p++;
-        }
-        // If we have stuff in the buffer, flush the fragment:
-        if (curr != buffer) {
-            ASSERT(curr < end + 1);
-            *curr = '\0';
-            bool success = printArg("%s", buffer);
-            if (!success) {
-                errorStr = buffer;
-                goto handleError;
-            }
-        }
-
-        // End if there are not more chars to print:
-        if (c == '\0')
-            break;
-
-        // If we get here, we've must have seen a '%':
-        startOfFormatSpecifier = p - 1;
-        ASSERT(*startOfFormatSpecifier == '%');
-        c = *p++;
-
-        // Check for "%%" case:
-        if (c == '%') {
-            bool success = printArg("%c", '%');
-            if (!success) {
-                errorStr = p - 2;
-                goto handleError;
-            }
-            continue;
-        }
-
-        // Check for JS (%J<x>) formatting extensions:
-        if (c == 'J') {
-            bool verbose = false;
-
-            c = *p++;
-            if (UNLIKELY(c == '\0')) {
-                errorStr = p - 2; // Rewind to % in "%J\0"
-                goto handleError;
-            }
-
-            if (c == '+') {
-                verbose = true;
-                c= *p++;
-                if (UNLIKELY(c == '\0')) {
-                    errorStr = p - 3; // Rewind to % in "%J+\0"
-                    goto handleError;
-                }
-            }
-
-            switch (c) {
-            // %Js - WTF::String*
-            case 's': {
-                printWTFString(args, verbose);
-                continue;
-            }
-            } // END switch.
-
-        // Check for non-JS extensions:
-        } else if (c == 'b') {
-            int value = va_arg(args, int);
-            printArg("%s", value ? "TRUE" : "FALSE");
-            continue;
-        }
-
-        // If we didn't handle the format in one of the above cases,
-        // rewind p and let the standard formatting check handle it
-        // if possible:
-        p = startOfFormatSpecifier;
-        ASSERT(*p == '%');
-
-        // Check for standard formatting:
-        // A format specifier always starts with a % and ends with some
-        // alphabet. We'll do the simple thing and scan until the next
-        // alphabet, or the end of string.
-
-        // In the following, we're going to use buffer as storage for a copy
-        // of a single format specifier. Hence, conceptually, we can think of
-        // 'buffer' as synonymous with 'argFormat' here:
-
-#define ABORT_IF_FORMAT_TOO_LONG(curr) \
-        do {                           \
-            if (UNLIKELY(curr >= end)) \
-                goto formatTooLong;    \
-        } while (false)
-        
-        curr = buffer;
-        *curr++ = *p++; // Output the first % in the format specifier.
-        c = *p++; // Grab the next char in the format specifier.
-
-        // Checks for leading modifiers e.g. "%-d":
-        //     0, -, ' ', +, '\''
-        if (c == '0' || c == '-' || c == ' ' || c == '+' || c == '\'' || c == '#') {
-            ABORT_IF_FORMAT_TOO_LONG(curr);
-            *curr++ = c;
-            c = *p++;
-        }
-
-        // Checks for decimal digit field width modifiers e.g. "%2f":
-        while (c >= '0' && c <= '9') {
-            ABORT_IF_FORMAT_TOO_LONG(curr);
-            *curr++ = c;
-            c = *p++;
-        }
-
-        // Checks for '.' e.g. "%2.f":
-        if (c == '.') {
-            ABORT_IF_FORMAT_TOO_LONG(curr);
-            *curr++ = c;
-            c = *p++;
-
-            // Checks for decimal digit precision modifiers  e.g. "%.2f":
-            while (c >= '0' && c <= '9') {
-                ABORT_IF_FORMAT_TOO_LONG(curr);
-                *curr++ = c;
-                c = *p++;
-            }
-        }
-
-        // Checks for the modifier <m> where <m> can be:
-        //     l, h, j, t, z
-        // e.g. "%ld"
-        if (c == 'l' || c == 'h' || c == 'j' || c == 't' || c == 'z' || c == 'L') {
-            ABORT_IF_FORMAT_TOO_LONG(curr);
-            *curr++ = c;
-            char prevChar = c;
-            c = *p++;
-
-            // Checks for the modifier ll or hh in %<x><m>:
-            if ((prevChar == 'l' || prevChar == 'h') && c == prevChar) {
-                ABORT_IF_FORMAT_TOO_LONG(curr);
-                *curr++ = c;
-                c = *p++;
-            }
-        }
-
-        // Checks for %<x> where <x> can be:
-        //     d, i, n, o, u, x, X
-        // But hey, we're just going to do the simple thing and allow any
-        // alphabet. The user is expected to pass correct format specifiers.
-        // We won't do any format checking here. We'll just pass it on, and the
-        // underlying ...printf() implementation may do the needed checking
-        // at its discretion.
-        while (c != '\0' && !isASCIIAlpha(c)) {
-            ABORT_IF_FORMAT_TOO_LONG(curr);
-            *curr++ = c;
-            c = *p++;
-        }
-
-        ABORT_IF_FORMAT_TOO_LONG(curr);
-        *curr++ = c;
-        if (c == '\0') {
-            // Uh oh. Bad format. We should have gotten an alphabet instead.
-            // Print the supposed format as a string instead:
-            errorStr = buffer;
-            goto handleError;
-        }
-
-        // Otherwise, we have the alpha that terminates the format.
-        // Terminate the buffer (i.e. argFormat) string:
-        ASSERT(isASCIIAlpha(c));
-        ABORT_IF_FORMAT_TOO_LONG(curr);
-        *curr = '\0';
-
-        bool success = printArg(buffer, args);
-        if (!success) {
-            errorStr = buffer;
-            goto handleError;
-        }
-    }
-#undef ABORT_IF_FORMAT_TOO_LONG
-
-    return;
-
-formatTooLong:
-    // Print the error string:
-    ASSERT(!!startOfFormatSpecifier);
-    p = startOfFormatSpecifier;
-    ASSERT(p >= format);
-    printArg("ERROR @ Format too long at \"%s\"\n", p);
-    return;
-
-handleError:
-    // We've got an error. Can't do any more work. Print an error message if
-    // possible and then just return.
-
-    // The errorStr may be pointing into the middle of buffer, or the original
-    // format string. Move the string to buffer for consistency, and also so
-    // that we can strip it of newlines below.
-    if (errorStr != buffer) {
-        size_t length = strlen(errorStr);
-        if (length > sizeof(buffer) - 1)
-            length = sizeof(buffer) - 1;
-        memmove(buffer, errorStr, length);
-        buffer[length] = '\0'; // Terminate the moved error string.
-    }
-    // Strip the newlines:
-    char* cp = buffer;
-    while (*cp) {
-        if (*cp == '\n' || *cp == '\r')
-            *cp = ' ';
-        cp++;
-    }
-    // Print the error string:
-    printArg("ERROR @ \"%s\"\n", buffer);
-}
-
-
-bool FormatPrinter::printArg(const char* format, ...)
-{
-    va_list args;
-    va_start(args, format);
-    bool success = printArg(format, args);
-    va_end(args);
-    return success;
-}
-
-bool FormatPrinter::printArg(const char* format, va_list args)
-{
-    int count = ::vprintf(format, args);
-    return (count >= 0); // Fail if less than 0 chars printed.
-}
-
-
-// %Js - WTF::String*
-// verbose mode prints: WTF::String "<your string>"
-void FormatPrinter::printWTFString(va_list args, bool verbose)
-{
-    const String* str = va_arg(args, const String*);
-
-    // Print verbose header if appropriate:
-    if (verbose)
-        printArg("WTF::String \"");
-
-    // Print the string itself:
-    if (!str->isEmpty()) {
-        if (str->is8Bit()) {
-            const LChar* chars = str->characters8();
-            printArg("%s", reinterpret_cast<const char*>(chars));
-        } else {
-            const UChar* chars = str->characters16();
-            printArg("%S", reinterpret_cast<const wchar_t*>(chars));
-        }
-    }
-
-    // Print verbose footer if appropriate:
-    if (verbose)
-        printArg("\"");
-}
-
-
-//============================================================================
-//  class FileFormatPrinter
-//    - implements functionality to support fprintf.
-
-class FileFormatPrinter: public FormatPrinter {
-public:
-    FileFormatPrinter(FILE*);
-private:
-    virtual bool printArg(const char* format, va_list args);
-
-    FILE* m_file;
-};
-
-FileFormatPrinter::FileFormatPrinter(FILE* file)
-    : m_file(file)
-{ 
-}
-
-bool FileFormatPrinter::printArg(const char* format, va_list args)
-{
-    int count = ::vfprintf(m_file, format, args);
-    return (count >= 0); // Fail if less than 0 chars printed.
-}
-
-
-//============================================================================
-//  class StringFormatPrinter
-//    - implements functionality to support sprintf.
-
-class StringFormatPrinter: public FormatPrinter {
-public:
-    StringFormatPrinter(char* buffer);
-private:
-    virtual bool printArg(const char* format, va_list args);
-
-    char* m_buffer;
-};
-
-StringFormatPrinter::StringFormatPrinter(char* buffer)
-    : m_buffer(buffer)
-{ 
-}
-
-bool StringFormatPrinter::printArg(const char* format, va_list args)
-{
-    int count = ::vsprintf(m_buffer, format, args);
-    m_buffer += count;
-    return (count >= 0); // Fail if less than 0 chars printed.
-}
-
-
-//============================================================================
-//  class StringNFormatPrinter
-//    - implements functionality to support snprintf.
-
-class StringNFormatPrinter: public FormatPrinter {
-public:
-    StringNFormatPrinter(char* buffer, size_t);
-private:
-    virtual bool printArg(const char* format, va_list args);
-
-    char* m_buffer;
-    size_t m_size;
-};
-
-
-StringNFormatPrinter::StringNFormatPrinter(char* buffer, size_t size)
-    : m_buffer(buffer)
-    , m_size(size)
-{
-}
-
-bool StringNFormatPrinter::printArg(const char* format, va_list args)
-{
-    if (m_size > 0) {
-        int count = ::vsnprintf(m_buffer, m_size, format, args);
-
-        // According to vsnprintf specs, ...
-        bool success = (count >= 0);
-        if (static_cast<size_t>(count) >= m_size) {
-            // If count > size, then we didn't have enough buffer space.
-            count = m_size;
-        }
-
-        // Adjust the buffer to what's left if appropriate:
-        if (success) {
-            m_buffer += count;
-            m_size -= count;
-        }
-        return success;
-    }
-    // No more room to print. Declare it a fail:
-    return false;
-}
-
-
-//============================================================================
-//  VMInspector printf family of methods:
-
-void VMInspector::fprintf(FILE* file, const char* format, ...)
-{
-    va_list args;
-    va_start(args, format);
-    FileFormatPrinter(file).print(format, args);
-    va_end(args);
-}
-
-void VMInspector::printf(const char* format, ...)
-{
-    va_list args;
-    va_start(args, format);
-    FormatPrinter().print(format, args);
-    va_end(args);
-}
-
-void VMInspector::sprintf(char* buffer, const char* format, ...)
-{
-    va_list args;
-    va_start(args, format);
-    StringFormatPrinter(buffer).print(format, args);
-    va_end(args);
-}
-
-void VMInspector::snprintf(char* buffer, size_t size, const char* format, ...)
-{
-    va_list args;
-    va_start(args, format);
-    StringNFormatPrinter(buffer, size).print(format, args);
-    va_end(args);
-}
-
-} // namespace JSC
-
-#endif // ENABLE(VMINSPECTOR)
diff --git a/Source/JavaScriptCore/interpreter/VMInspector.h b/Source/JavaScriptCore/interpreter/VMInspector.h
deleted file mode 100644
index 6623068dc..000000000
--- a/Source/JavaScriptCore/interpreter/VMInspector.h
+++ /dev/null
@@ -1,89 +0,0 @@
-/*
- * Copyright (C) 2012 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
- */
-
-#ifndef VMInspector_h
-#define VMInspector_h
-
-#define ENABLE_VMINSPECTOR 0
-
-#include "CallFrame.h"
-#include "JSCJSValue.h"
-#include <stdarg.h>
-#include <stdio.h>
-#include <wtf/text/WTFString.h>
-
-namespace JSC {
-
-#if ENABLE(VMINSPECTOR)
-
-class VMInspector {
-public:    
-    static JS_EXPORT_PRIVATE const char* getTypeName(JSValue);
-    static JS_EXPORT_PRIVATE void dumpFrame0(CallFrame*);
-    static JS_EXPORT_PRIVATE void dumpFrame(CallFrame*, const char* prefix = 0, const char* funcName = 0, const char* file = 0, int line = -1);
-    static JS_EXPORT_PRIVATE int countFrames(CallFrame*);
-
-    // Special family of ...printf() functions that support, in addition to the
-    // standard % formats (e.g. %d, %s, etc), the following extra JSC formatting
-    // options, %J<x>, where <x> consists of:
-    //
-    //   +    - verbose mode modifier.
-    //          Used in combination with other options. Must come after the %J.
-    //   s    - WTF::String*
-    //
-    // Examples of usage:
-    //
-    //    WTF::String str("My WTF String");
-    //
-    //    // Printing the string. Will print:
-    //    // The wtf string says: "My WTF String" and is NOT EMPTY.
-    //
-    //    VMInspector::printf("The wtf string says: \"%Js\" and is %s\n",
-    //        &str, str.isEmpty()?"EMPTY":"NOT EMPTY");
-    //
-    //    // Printing the string with verbose mode. Will print:
-    //    // <WTF::String "My WTF String">
-    //
-    //    VMInspector::printf("<%J+s>\n", &str);
-    //
-    // Also added some convenience non-JS formats:
-    //
-    //   %b    - boolean (va_args will look for an int).
-    //           Prints TRUE if non-zero, else prints FALSE.
-    //
-    // Caution: the user is expected to pass the correctly matched arguments
-    // to pair with the corresponding % fomatting.
-
-    static JS_EXPORT_PRIVATE void fprintf(FILE*, const char* format, ...);
-    static JS_EXPORT_PRIVATE void printf(const char* format, ...);
-    static JS_EXPORT_PRIVATE void sprintf(char*, const char* format, ...);
-    static JS_EXPORT_PRIVATE void snprintf(char*, size_t, const char* format, ...);
-};
-
-#endif // ENABLE(VMINSPECTOR)
-
-} // namespace JSC
-
-#endif // VMInspector.h