weex_core/Source/include/JavaScriptCore/interpreter/CallFrame.h - incubator-weex - Git at Google

 /*
  *  Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
  *  Copyright (C) 2001 Peter Kelly (pmk@post.com)
  *  Copyright (C) 2003-2017 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
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  *  Library General Public License for more details.
  *
  *  You should have received a copy of the GNU Library General Public License
  *  along with this library; see the file COPYING.LIB.  If not, write to
  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  *  Boston, MA 02110-1301, USA.
  *
  */

 #pragma once

 #include "AbstractPC.h"
 #include "MacroAssemblerCodeRef.h"
 #include "Register.h"
 #include "StackVisitor.h"
 #include "VM.h"
 #include "VMEntryRecord.h"

 namespace JSC  {

     class Arguments;
     class ExecState;
     class Interpreter;
     class JSCallee;
     class JSScope;

     struct Instruction;

     typedef ExecState CallFrame;

     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; }
         bool operator==(const CallSiteIndex& other) const { return m_bits == other.m_bits; }

         inline uint32_t bits() const { return m_bits; }

     private:
         uint32_t m_bits;
     };

     struct CallerFrameAndPC {
         CallFrame* callerFrame;
         Instruction* pc;
         static const int sizeInRegisters = 2 * sizeof(void*) / sizeof(Register);
     };
     static_assert(CallerFrameAndPC::sizeInRegisters == sizeof(CallerFrameAndPC) / sizeof(Register), "CallerFrameAndPC::sizeInRegisters is incorrect.");

     struct CallFrameSlot {
         static const int codeBlock = CallerFrameAndPC::sizeInRegisters;
         static const int callee = codeBlock + 1;
         static const int argumentCount = callee + 1;
         static const int thisArgument = argumentCount + 1;
         static const int firstArgument = thisArgument + 1;
     };

     // Represents the current state of script execution.
     // Passed as the first argument to most functions.
     class ExecState : private Register {
     public:
         static const int headerSizeInRegisters = CallFrameSlot::argumentCount + 1;

         JSValue calleeAsValue() const { return this[CallFrameSlot::callee].jsValue(); }
         JSObject* jsCallee() const { return this[CallFrameSlot::callee].object(); }
         JSCell* callee() const { return this[CallFrameSlot::callee].unboxedCell(); }
         SUPPRESS_ASAN JSValue unsafeCallee() const { return this[CallFrameSlot::callee].asanUnsafeJSValue(); }
         CodeBlock* codeBlock() const { return this[CallFrameSlot::codeBlock].Register::codeBlock(); }
         CodeBlock** addressOfCodeBlock() const { return bitwise_cast<CodeBlock**>(this + CallFrameSlot::codeBlock); }
         SUPPRESS_ASAN CodeBlock* unsafeCodeBlock() const { return this[CallFrameSlot::codeBlock].Register::asanUnsafeCodeBlock(); }
         JSScope* scope(int scopeRegisterOffset) const
         {
             ASSERT(this[scopeRegisterOffset].Register::scope());
             return this[scopeRegisterOffset].Register::scope();
         }

         // Global object in which execution began.
         JS_EXPORT_PRIVATE JSGlobalObject* vmEntryGlobalObject();

         // Global object in which the currently executing code was defined.
         // 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
         // the actual DOM window, which can't be "this" for security reasons.
         JSObject* globalThisValue() const;

         VM& vm() const;

         // Convenience functions for access to global data.
         // It takes a few memory references to get from a call frame to the global data
         // 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.

         AtomicStringTable* atomicStringTable() const { return vm().atomicStringTable(); }
         const CommonIdentifiers& propertyNames() const { return *vm().propertyNames; }
         const ArgList& emptyList() const { return *vm().emptyList; }
         Interpreter* interpreter() { return vm().interpreter; }
         Heap* heap() { return &vm().heap; }


         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 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*&);

         JS_EXPORT_PRIVATE SourceOrigin callerSourceOrigin();

         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); }

         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();

         // This will get you a CodeOrigin. It will always succeed. May return
         // CodeOrigin(0) if we're in native code.
         JS_EXPORT_PRIVATE CodeOrigin codeOrigin();

         Register* topOfFrame()
         {
             if (!codeBlock())
                 return registers();
             return topOfFrameInternal();
         }

         Instruction* currentVPC() const; // This only makes sense in the LLInt and baseline.
         void setCurrentVPC(Instruction* vpc);

         void setCallerFrame(CallFrame* frame) { callerFrameAndPC().callerFrame = frame; }
         void setScope(int scopeRegisterOffset, JSScope* scope) { static_cast<Register*>(this)[scopeRegisterOffset] = scope; }

         static void initGlobalExec(ExecState* globalExec, JSCallee* globalCallee);

         // Read a register from the codeframe (or constant from the CodeBlock).
         Register& r(int);
         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[CallFrameSlot::argumentCount].payload(); }
         static int argumentOffset(int argument) { return (CallFrameSlot::firstArgument + argument); }
         static int argumentOffsetIncludingThis(int argument) { return (CallFrameSlot::thisArgument + argument); }

         // In the following (argument() and setArgument()), the 'argument'
         // parameter is the index of the arguments of the target function of
         // this frame. The index starts at 0 for the first arg, 1 for the
         // second, etc.
         //
         // The arguments (in this case) do not include the 'this' value.
         // arguments(0) will not fetch the 'this' value. To get/set 'this',
         // use thisValue() and setThisValue() below.

         JSValue* addressOfArgumentsStart() const { return bitwise_cast<JSValue*>(this + argumentOffset(0)); }
         JSValue argument(size_t argument)
         {
             if (argument >= argumentCount())
                  return jsUndefined();
             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; }

         // 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(); }

         JSValue argumentAfterCapture(size_t argument);

         static int offsetFor(size_t argumentCountIncludingThis) { return argumentCountIncludingThis + CallFrameSlot::thisArgument - 1; }

         static CallFrame* noCaller() { return 0; }

         void setArgumentCountIncludingThis(int count) { static_cast<Register*>(this)[CallFrameSlot::argumentCount].payload() = count; }
         void setCallee(JSObject* callee) { static_cast<Register*>(this)[CallFrameSlot::callee] = callee; }
         void setCodeBlock(CodeBlock* codeBlock) { static_cast<Register*>(this)[CallFrameSlot::codeBlock] = codeBlock; }
         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&) const;
         // FIXME: This method is improper. We rely on the fact that we can call it with a null
         // receiver. We should always be using StackVisitor directly.
         template <typename Functor> void iterate(const Functor& functor)
         {
             StackVisitor::visit<Functor>(this, functor);
         }

         void dump(PrintStream&);
         JS_EXPORT_PRIVATE const char* describeFrame();

     private:

         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:

         size_t argIndexForRegister(Register* reg)
         {
             // The register at 'offset' number of slots from the frame pointer
             // i.e.
             //       reg = frame[offset];
             //   ==> reg = frame + offset;
             //   ==> offset = reg - frame;
             int offset = reg - this->registers();

             // The offset is defined (based on argumentOffset()) to be:
             //       offset = CallFrameSlot::firstArgument - argIndex;
             // Hence:
             //       argIndex = CallFrameSlot::firstArgument - offset;
             size_t argIndex = offset - CallFrameSlot::firstArgument;
             return argIndex;
         }

         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); }
     };

 } // namespace JSC
	/*
	* Copyright (C) 1999-2001 Harri Porten (porten@kde.org)
	* Copyright (C) 2001 Peter Kelly (pmk@post.com)
	* Copyright (C) 2003-2017 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
	* License as published by the Free Software Foundation; either
	* version 2 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Library General Public License for more details.
	*
	* You should have received a copy of the GNU Library General Public License
	* along with this library; see the file COPYING.LIB. If not, write to
	* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
	* Boston, MA 02110-1301, USA.
	*
	*/

	#pragma once

	#include "AbstractPC.h"
	#include "MacroAssemblerCodeRef.h"
	#include "Register.h"
	#include "StackVisitor.h"
	#include "VM.h"
	#include "VMEntryRecord.h"

	namespace JSC {

	class Arguments;
	class ExecState;
	class Interpreter;
	class JSCallee;
	class JSScope;

	struct Instruction;

	typedef ExecState CallFrame;

	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; }
	bool operator==(const CallSiteIndex& other) const { return m_bits == other.m_bits; }

	inline uint32_t bits() const { return m_bits; }

	private:
	uint32_t m_bits;
	};

	struct CallerFrameAndPC {
	CallFrame* callerFrame;
	Instruction* pc;
	static const int sizeInRegisters = 2 * sizeof(void*) / sizeof(Register);
	};
	static_assert(CallerFrameAndPC::sizeInRegisters == sizeof(CallerFrameAndPC) / sizeof(Register), "CallerFrameAndPC::sizeInRegisters is incorrect.");

	struct CallFrameSlot {
	static const int codeBlock = CallerFrameAndPC::sizeInRegisters;
	static const int callee = codeBlock + 1;
	static const int argumentCount = callee + 1;
	static const int thisArgument = argumentCount + 1;
	static const int firstArgument = thisArgument + 1;
	};

	// Represents the current state of script execution.
	// Passed as the first argument to most functions.
	class ExecState : private Register {
	public:
	static const int headerSizeInRegisters = CallFrameSlot::argumentCount + 1;

	JSValue calleeAsValue() const { return this[CallFrameSlot::callee].jsValue(); }
	JSObject* jsCallee() const { return this[CallFrameSlot::callee].object(); }
	JSCell* callee() const { return this[CallFrameSlot::callee].unboxedCell(); }
	SUPPRESS_ASAN JSValue unsafeCallee() const { return this[CallFrameSlot::callee].asanUnsafeJSValue(); }
	CodeBlock* codeBlock() const { return this[CallFrameSlot::codeBlock].Register::codeBlock(); }
	CodeBlock addressOfCodeBlock() const { return bitwise_cast<CodeBlock>(this + CallFrameSlot::codeBlock); }
	SUPPRESS_ASAN CodeBlock* unsafeCodeBlock() const { return this[CallFrameSlot::codeBlock].Register::asanUnsafeCodeBlock(); }
	JSScope* scope(int scopeRegisterOffset) const
	{
	ASSERT(this[scopeRegisterOffset].Register::scope());
	return this[scopeRegisterOffset].Register::scope();
	}

	// Global object in which execution began.
	JS_EXPORT_PRIVATE JSGlobalObject* vmEntryGlobalObject();

	// Global object in which the currently executing code was defined.
	// 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
	// the actual DOM window, which can't be "this" for security reasons.
	JSObject* globalThisValue() const;

	VM& vm() const;

	// Convenience functions for access to global data.
	// It takes a few memory references to get from a call frame to the global data
	// 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.

	AtomicStringTable* atomicStringTable() const { return vm().atomicStringTable(); }
	const CommonIdentifiers& propertyNames() const { return *vm().propertyNames; }
	const ArgList& emptyList() const { return *vm().emptyList; }
	Interpreter* interpreter() { return vm().interpreter; }
	Heap* heap() { return &vm().heap; }


	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 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*&);

	JS_EXPORT_PRIVATE SourceOrigin callerSourceOrigin();

	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); }

	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();

	// This will get you a CodeOrigin. It will always succeed. May return
	// CodeOrigin(0) if we're in native code.
	JS_EXPORT_PRIVATE CodeOrigin codeOrigin();

	Register* topOfFrame()
	{
	if (!codeBlock())
	return registers();
	return topOfFrameInternal();
	}

	Instruction* currentVPC() const; // This only makes sense in the LLInt and baseline.
	void setCurrentVPC(Instruction* vpc);

	void setCallerFrame(CallFrame* frame) { callerFrameAndPC().callerFrame = frame; }
	void setScope(int scopeRegisterOffset, JSScope* scope) { static_cast<Register*>(this)[scopeRegisterOffset] = scope; }

	static void initGlobalExec(ExecState* globalExec, JSCallee* globalCallee);

	// Read a register from the codeframe (or constant from the CodeBlock).
	Register& r(int);
	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[CallFrameSlot::argumentCount].payload(); }
	static int argumentOffset(int argument) { return (CallFrameSlot::firstArgument + argument); }
	static int argumentOffsetIncludingThis(int argument) { return (CallFrameSlot::thisArgument + argument); }

	// In the following (argument() and setArgument()), the 'argument'
	// parameter is the index of the arguments of the target function of
	// this frame. The index starts at 0 for the first arg, 1 for the
	// second, etc.
	//
	// The arguments (in this case) do not include the 'this' value.
	// arguments(0) will not fetch the 'this' value. To get/set 'this',
	// use thisValue() and setThisValue() below.

	JSValue* addressOfArgumentsStart() const { return bitwise_cast<JSValue*>(this + argumentOffset(0)); }
	JSValue argument(size_t argument)
	{
	if (argument >= argumentCount())
	return jsUndefined();
	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; }

	// 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(); }

	JSValue argumentAfterCapture(size_t argument);

	static int offsetFor(size_t argumentCountIncludingThis) { return argumentCountIncludingThis + CallFrameSlot::thisArgument - 1; }

	static CallFrame* noCaller() { return 0; }

	void setArgumentCountIncludingThis(int count) { static_cast<Register*>(this)[CallFrameSlot::argumentCount].payload() = count; }
	void setCallee(JSObject* callee) { static_cast<Register*>(this)[CallFrameSlot::callee] = callee; }
	void setCodeBlock(CodeBlock* codeBlock) { static_cast<Register*>(this)[CallFrameSlot::codeBlock] = codeBlock; }
	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&) const;
	// FIXME: This method is improper. We rely on the fact that we can call it with a null
	// receiver. We should always be using StackVisitor directly.
	template <typename Functor> void iterate(const Functor& functor)
	{
	StackVisitor::visit<Functor>(this, functor);
	}

	void dump(PrintStream&);
	JS_EXPORT_PRIVATE const char* describeFrame();

	private:

	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:

	size_t argIndexForRegister(Register* reg)
	{
	// The register at 'offset' number of slots from the frame pointer
	// i.e.
	// reg = frame[offset];
	// ==> reg = frame + offset;
	// ==> offset = reg - frame;
	int offset = reg - this->registers();

	// The offset is defined (based on argumentOffset()) to be:
	// offset = CallFrameSlot::firstArgument - argIndex;
	// Hence:
	// argIndex = CallFrameSlot::firstArgument - offset;
	size_t argIndex = offset - CallFrameSlot::firstArgument;
	return argIndex;
	}

	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); }
	};

	} // namespace JSC