source: webkit/trunk/JavaScriptCore/bytecode/CodeBlock.h@ 48389

/*
 * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
 * Copyright (C) 2008 Cameron Zwarich <[email protected]>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef CodeBlock_h
#define CodeBlock_h

#include "EvalCodeCache.h"
#include "Instruction.h"
#include "JITCode.h"
#include "JSGlobalObject.h"
#include "JumpTable.h"
#include "Nodes.h"
#include "PtrAndFlags.h"
#include "RegExp.h"
#include "UString.h"
#include <wtf/FastAllocBase.h>
#include <wtf/RefPtr.h>
#include <wtf/Vector.h>

#if ENABLE(JIT)
#include "StructureStubInfo.h"
#endif

// Register numbers used in bytecode operations have different meaning accoring to their ranges:
//      0x80000000-0xFFFFFFFF  Negative indicies from the CallFrame pointer are entries in the call frame, see RegisterFile.h.
//      0x00000000-0x3FFFFFFF  Forwards indices from the CallFrame pointer are local vars and temporaries with the function's callframe.
//      0x40000000-0x7FFFFFFF  Positive indices from 0x40000000 specify entries in the constant pool on the CodeBlock.
static const int FirstConstantRegisterIndex = 0x40000000;

namespace JSC {

    enum HasSeenShouldRepatch {
        hasSeenShouldRepatch
    };

    class ExecState;

    enum CodeType { GlobalCode, EvalCode, FunctionCode };

    static ALWAYS_INLINE int missingThisObjectMarker() { return std::numeric_limits<int>::max(); }

    struct HandlerInfo {
        uint32_t start;
        uint32_t end;
        uint32_t target;
        uint32_t scopeDepth;
#if ENABLE(JIT)
        CodeLocationLabel nativeCode;
#endif
    };

    struct ExpressionRangeInfo {
        enum {
            MaxOffset = (1 << 7) - 1, 
            MaxDivot = (1 << 25) - 1
        };
        uint32_t instructionOffset : 25;
        uint32_t divotPoint : 25;
        uint32_t startOffset : 7;
        uint32_t endOffset : 7;
    };

    struct LineInfo {
        uint32_t instructionOffset;
        int32_t lineNumber;
    };

    // Both op_construct and op_instanceof require a use of op_get_by_id to get
    // the prototype property from an object. The exception messages for exceptions
    // thrown by these instances op_get_by_id need to reflect this.
    struct GetByIdExceptionInfo {
        unsigned bytecodeOffset : 31;
        bool isOpConstruct : 1;
    };

#if ENABLE(JIT)
    struct CallLinkInfo {
        CallLinkInfo()
            : callee(0)
        {
        }
    
        unsigned bytecodeIndex;
        CodeLocationNearCall callReturnLocation;
        CodeLocationDataLabelPtr hotPathBegin;
        CodeLocationNearCall hotPathOther;
        PtrAndFlags<CodeBlock, HasSeenShouldRepatch> ownerCodeBlock;
        CodeBlock* callee;
        unsigned position;
        
        void setUnlinked() { callee = 0; }
        bool isLinked() { return callee; }

        bool seenOnce()
        {
            return ownerCodeBlock.isFlagSet(hasSeenShouldRepatch);
        }

        void setSeen()
        {
            ownerCodeBlock.setFlag(hasSeenShouldRepatch);
        }
    };

    struct MethodCallLinkInfo {
        MethodCallLinkInfo()
            : cachedStructure(0)
        {
        }

        bool seenOnce()
        {
            return cachedPrototypeStructure.isFlagSet(hasSeenShouldRepatch);
        }

        void setSeen()
        {
            cachedPrototypeStructure.setFlag(hasSeenShouldRepatch);
        }

        CodeLocationCall callReturnLocation;
        CodeLocationDataLabelPtr structureLabel;
        Structure* cachedStructure;
        PtrAndFlags<Structure, HasSeenShouldRepatch> cachedPrototypeStructure;
    };

    struct FunctionRegisterInfo {
        FunctionRegisterInfo(unsigned bytecodeOffset, int functionRegisterIndex)
            : bytecodeOffset(bytecodeOffset)
            , functionRegisterIndex(functionRegisterIndex)
        {
        }

        unsigned bytecodeOffset;
        int functionRegisterIndex;
    };

    struct GlobalResolveInfo {
        GlobalResolveInfo(unsigned bytecodeOffset)
            : structure(0)
            , offset(0)
            , bytecodeOffset(bytecodeOffset)
        {
        }

        Structure* structure;
        unsigned offset;
        unsigned bytecodeOffset;
    };

    // This structure is used to map from a call return location
    // (given as an offset in bytes into the JIT code) back to
    // the bytecode index of the corresponding bytecode operation.
    // This is then used to look up the corresponding handler.
    struct CallReturnOffsetToBytecodeIndex {
        CallReturnOffsetToBytecodeIndex(unsigned callReturnOffset, unsigned bytecodeIndex)
            : callReturnOffset(callReturnOffset)
            , bytecodeIndex(bytecodeIndex)
        {
        }

        unsigned callReturnOffset;
        unsigned bytecodeIndex;
    };

    // valueAtPosition helpers for the binaryChop algorithm below.

    inline void* getStructureStubInfoReturnLocation(StructureStubInfo* structureStubInfo)
    {
        return structureStubInfo->callReturnLocation.executableAddress();
    }

    inline void* getCallLinkInfoReturnLocation(CallLinkInfo* callLinkInfo)
    {
        return callLinkInfo->callReturnLocation.executableAddress();
    }

    inline void* getMethodCallLinkInfoReturnLocation(MethodCallLinkInfo* methodCallLinkInfo)
    {
        return methodCallLinkInfo->callReturnLocation.executableAddress();
    }

    inline unsigned getCallReturnOffset(CallReturnOffsetToBytecodeIndex* pc)
    {
        return pc->callReturnOffset;
    }

    // Binary chop algorithm, calls valueAtPosition on pre-sorted elements in array,
    // compares result with key (KeyTypes should be comparable with '--', '<', '>').
    // Optimized for cases where the array contains the key, checked by assertions.
    template<typename ArrayType, typename KeyType, KeyType(*valueAtPosition)(ArrayType*)>
    inline ArrayType* binaryChop(ArrayType* array, size_t size, KeyType key)
    {
        // The array must contain at least one element (pre-condition, array does conatin key).
        // If the array only contains one element, no need to do the comparison.
        while (size > 1) {
            // Pick an element to check, half way through the array, and read the value.
            int pos = (size - 1) >> 1;
            KeyType val = valueAtPosition(&array[pos]);
            
            // If the key matches, success!
            if (val == key)
                return &array[pos];
            // The item we are looking for is smaller than the item being check; reduce the value of 'size',
            // chopping off the right hand half of the array.
            else if (key < val)
                size = pos;
            // Discard all values in the left hand half of the array, up to and including the item at pos.
            else {
                size -= (pos + 1);
                array += (pos + 1);
            }

            // 'size' should never reach zero.
            ASSERT(size);
        }
        
        // If we reach this point we've chopped down to one element, no need to check it matches
        ASSERT(size == 1);
        ASSERT(key == valueAtPosition(&array[0]));
        return &array[0];
    }
#endif

    struct ExceptionInfo : FastAllocBase {
        Vector<ExpressionRangeInfo> m_expressionInfo;
        Vector<LineInfo> m_lineInfo;
        Vector<GetByIdExceptionInfo> m_getByIdExceptionInfo;

#if ENABLE(JIT)
        Vector<CallReturnOffsetToBytecodeIndex> m_callReturnIndexVector;
#endif
    };

    class CodeBlock : public FastAllocBase {
        friend class JIT;
    protected:
        CodeBlock(ScriptExecutable* ownerExecutable, CodeType, PassRefPtr<SourceProvider>, unsigned sourceOffset, SymbolTable* symbolTable);
    public:
        virtual ~CodeBlock();

        void markAggregate(MarkStack&);
        void refStructures(Instruction* vPC) const;
        void derefStructures(Instruction* vPC) const;
#if ENABLE(JIT_OPTIMIZE_CALL)
        void unlinkCallers();
#endif

        static void dumpStatistics();

#if !defined(NDEBUG) || ENABLE_OPCODE_SAMPLING
        void dump(ExecState*) const;
        void printStructures(const Instruction*) const;
        void printStructure(const char* name, const Instruction*, int operand) const;
#endif

        inline bool isKnownNotImmediate(int index)
        {
            if (index == m_thisRegister)
                return true;

            if (isConstantRegisterIndex(index))
                return getConstant(index).isCell();

            return false;
        }

        ALWAYS_INLINE bool isTemporaryRegisterIndex(int index)
        {
            return index >= m_numVars;
        }

        HandlerInfo* handlerForBytecodeOffset(unsigned bytecodeOffset);
        int lineNumberForBytecodeOffset(CallFrame*, unsigned bytecodeOffset);
        int expressionRangeForBytecodeOffset(CallFrame*, unsigned bytecodeOffset, int& divot, int& startOffset, int& endOffset);
        bool getByIdExceptionInfoForBytecodeOffset(CallFrame*, unsigned bytecodeOffset, OpcodeID&);

#if ENABLE(JIT)
        void addCaller(CallLinkInfo* caller)
        {
            caller->callee = this;
            caller->position = m_linkedCallerList.size();
            m_linkedCallerList.append(caller);
        }

        void removeCaller(CallLinkInfo* caller)
        {
            unsigned pos = caller->position;
            unsigned lastPos = m_linkedCallerList.size() - 1;

            if (pos != lastPos) {
                m_linkedCallerList[pos] = m_linkedCallerList[lastPos];
                m_linkedCallerList[pos]->position = pos;
            }
            m_linkedCallerList.shrink(lastPos);
        }

        StructureStubInfo& getStubInfo(ReturnAddressPtr returnAddress)
        {
            return *(binaryChop<StructureStubInfo, void*, getStructureStubInfoReturnLocation>(m_structureStubInfos.begin(), m_structureStubInfos.size(), returnAddress.value()));
        }

        CallLinkInfo& getCallLinkInfo(ReturnAddressPtr returnAddress)
        {
            return *(binaryChop<CallLinkInfo, void*, getCallLinkInfoReturnLocation>(m_callLinkInfos.begin(), m_callLinkInfos.size(), returnAddress.value()));
        }

        MethodCallLinkInfo& getMethodCallLinkInfo(ReturnAddressPtr returnAddress)
        {
            return *(binaryChop<MethodCallLinkInfo, void*, getMethodCallLinkInfoReturnLocation>(m_methodCallLinkInfos.begin(), m_methodCallLinkInfos.size(), returnAddress.value()));
        }

        unsigned getBytecodeIndex(CallFrame* callFrame, ReturnAddressPtr returnAddress)
        {
            reparseForExceptionInfoIfNecessary(callFrame);
            return binaryChop<CallReturnOffsetToBytecodeIndex, unsigned, getCallReturnOffset>(callReturnIndexVector().begin(), callReturnIndexVector().size(), ownerExecutable()->generatedJITCode().offsetOf(returnAddress.value()))->bytecodeIndex;
        }
        
        bool functionRegisterForBytecodeOffset(unsigned bytecodeOffset, int& functionRegisterIndex);
#endif

        void setIsNumericCompareFunction(bool isNumericCompareFunction) { m_isNumericCompareFunction = isNumericCompareFunction; }
        bool isNumericCompareFunction() { return m_isNumericCompareFunction; }

        Vector<Instruction>& instructions() { return m_instructions; }
        void discardBytecode() { m_instructions.clear(); }

#ifndef NDEBUG
        unsigned instructionCount() { return m_instructionCount; }
        void setInstructionCount(unsigned instructionCount) { m_instructionCount = instructionCount; }
#endif

#if ENABLE(JIT)
        JITCode& getJITCode() { return ownerExecutable()->generatedJITCode(); }
        ExecutablePool* executablePool() { return ownerExecutable()->getExecutablePool(); }
#endif

        ScriptExecutable* ownerExecutable() const { return m_ownerExecutable; }

        void setGlobalData(JSGlobalData* globalData) { m_globalData = globalData; }

        void setThisRegister(int thisRegister) { m_thisRegister = thisRegister; }
        int thisRegister() const { return m_thisRegister; }

        void setNeedsFullScopeChain(bool needsFullScopeChain) { m_needsFullScopeChain = needsFullScopeChain; }
        bool needsFullScopeChain() const { return m_needsFullScopeChain; }
        void setUsesEval(bool usesEval) { m_usesEval = usesEval; }
        bool usesEval() const { return m_usesEval; }
        void setUsesArguments(bool usesArguments) { m_usesArguments = usesArguments; }
        bool usesArguments() const { return m_usesArguments; }

        CodeType codeType() const { return m_codeType; }

        SourceProvider* source() const { return m_source.get(); }
        unsigned sourceOffset() const { return m_sourceOffset; }

        size_t numberOfJumpTargets() const { return m_jumpTargets.size(); }
        void addJumpTarget(unsigned jumpTarget) { m_jumpTargets.append(jumpTarget); }
        unsigned jumpTarget(int index) const { return m_jumpTargets[index]; }
        unsigned lastJumpTarget() const { return m_jumpTargets.last(); }

#if !ENABLE(JIT)
        void addPropertyAccessInstruction(unsigned propertyAccessInstruction) { m_propertyAccessInstructions.append(propertyAccessInstruction); }
        void addGlobalResolveInstruction(unsigned globalResolveInstruction) { m_globalResolveInstructions.append(globalResolveInstruction); }
        bool hasGlobalResolveInstructionAtBytecodeOffset(unsigned bytecodeOffset);
#else
        size_t numberOfStructureStubInfos() const { return m_structureStubInfos.size(); }
        void addStructureStubInfo(const StructureStubInfo& stubInfo) { m_structureStubInfos.append(stubInfo); }
        StructureStubInfo& structureStubInfo(int index) { return m_structureStubInfos[index]; }

        void addGlobalResolveInfo(unsigned globalResolveInstruction) { m_globalResolveInfos.append(GlobalResolveInfo(globalResolveInstruction)); }
        GlobalResolveInfo& globalResolveInfo(int index) { return m_globalResolveInfos[index]; }
        bool hasGlobalResolveInfoAtBytecodeOffset(unsigned bytecodeOffset);

        size_t numberOfCallLinkInfos() const { return m_callLinkInfos.size(); }
        void addCallLinkInfo() { m_callLinkInfos.append(CallLinkInfo()); }
        CallLinkInfo& callLinkInfo(int index) { return m_callLinkInfos[index]; }

        void addMethodCallLinkInfos(unsigned n) { m_methodCallLinkInfos.grow(n); }
        MethodCallLinkInfo& methodCallLinkInfo(int index) { return m_methodCallLinkInfos[index]; }

        void addFunctionRegisterInfo(unsigned bytecodeOffset, int functionIndex) { createRareDataIfNecessary(); m_rareData->m_functionRegisterInfos.append(FunctionRegisterInfo(bytecodeOffset, functionIndex)); }
#endif

        // Exception handling support

        size_t numberOfExceptionHandlers() const { return m_rareData ? m_rareData->m_exceptionHandlers.size() : 0; }
        void addExceptionHandler(const HandlerInfo& hanler) { createRareDataIfNecessary(); return m_rareData->m_exceptionHandlers.append(hanler); }
        HandlerInfo& exceptionHandler(int index) { ASSERT(m_rareData); return m_rareData->m_exceptionHandlers[index]; }

        bool hasExceptionInfo() const { return m_exceptionInfo; }
        void clearExceptionInfo() { m_exceptionInfo.clear(); }
        ExceptionInfo* extractExceptionInfo() { ASSERT(m_exceptionInfo); return m_exceptionInfo.release(); }

        void addExpressionInfo(const ExpressionRangeInfo& expressionInfo) { ASSERT(m_exceptionInfo); m_exceptionInfo->m_expressionInfo.append(expressionInfo); }
        void addGetByIdExceptionInfo(const GetByIdExceptionInfo& info) { ASSERT(m_exceptionInfo); m_exceptionInfo->m_getByIdExceptionInfo.append(info); }

        size_t numberOfLineInfos() const { ASSERT(m_exceptionInfo); return m_exceptionInfo->m_lineInfo.size(); }
        void addLineInfo(const LineInfo& lineInfo) { ASSERT(m_exceptionInfo); m_exceptionInfo->m_lineInfo.append(lineInfo); }
        LineInfo& lastLineInfo() { ASSERT(m_exceptionInfo); return m_exceptionInfo->m_lineInfo.last(); }

#if ENABLE(JIT)
        Vector<CallReturnOffsetToBytecodeIndex>& callReturnIndexVector() { ASSERT(m_exceptionInfo); return m_exceptionInfo->m_callReturnIndexVector; }
#endif

        // Constant Pool

        size_t numberOfIdentifiers() const { return m_identifiers.size(); }
        void addIdentifier(const Identifier& i) { return m_identifiers.append(i); }
        Identifier& identifier(int index) { return m_identifiers[index]; }

        size_t numberOfConstantRegisters() const { return m_constantRegisters.size(); }
        void addConstantRegister(const Register& r) { return m_constantRegisters.append(r); }
        Register& constantRegister(int index) { return m_constantRegisters[index - FirstConstantRegisterIndex]; }
        ALWAYS_INLINE bool isConstantRegisterIndex(int index) { return index >= FirstConstantRegisterIndex; }
        ALWAYS_INLINE JSValue getConstant(int index) const { return m_constantRegisters[index - FirstConstantRegisterIndex].jsValue(); }

        unsigned addFunctionDecl(PassRefPtr<FunctionExecutable> n) { unsigned size = m_functionDecls.size(); m_functionDecls.append(n); return size; }
        FunctionExecutable* functionDecl(int index) { return m_functionDecls[index].get(); }
        int numberOfFunctionDecls() { return m_functionDecls.size(); }
        unsigned addFunctionExpr(PassRefPtr<FunctionExecutable> n) { unsigned size = m_functionExprs.size(); m_functionExprs.append(n); return size; }
        FunctionExecutable* functionExpr(int index) { return m_functionExprs[index].get(); }

        unsigned addRegExp(RegExp* r) { createRareDataIfNecessary(); unsigned size = m_rareData->m_regexps.size(); m_rareData->m_regexps.append(r); return size; }
        RegExp* regexp(int index) const { ASSERT(m_rareData); return m_rareData->m_regexps[index].get(); }


        // Jump Tables

        size_t numberOfImmediateSwitchJumpTables() const { return m_rareData ? m_rareData->m_immediateSwitchJumpTables.size() : 0; }
        SimpleJumpTable& addImmediateSwitchJumpTable() { createRareDataIfNecessary(); m_rareData->m_immediateSwitchJumpTables.append(SimpleJumpTable()); return m_rareData->m_immediateSwitchJumpTables.last(); }
        SimpleJumpTable& immediateSwitchJumpTable(int tableIndex) { ASSERT(m_rareData); return m_rareData->m_immediateSwitchJumpTables[tableIndex]; }

        size_t numberOfCharacterSwitchJumpTables() const { return m_rareData ? m_rareData->m_characterSwitchJumpTables.size() : 0; }
        SimpleJumpTable& addCharacterSwitchJumpTable() { createRareDataIfNecessary(); m_rareData->m_characterSwitchJumpTables.append(SimpleJumpTable()); return m_rareData->m_characterSwitchJumpTables.last(); }
        SimpleJumpTable& characterSwitchJumpTable(int tableIndex) { ASSERT(m_rareData); return m_rareData->m_characterSwitchJumpTables[tableIndex]; }

        size_t numberOfStringSwitchJumpTables() const { return m_rareData ? m_rareData->m_stringSwitchJumpTables.size() : 0; }
        StringJumpTable& addStringSwitchJumpTable() { createRareDataIfNecessary(); m_rareData->m_stringSwitchJumpTables.append(StringJumpTable()); return m_rareData->m_stringSwitchJumpTables.last(); }
        StringJumpTable& stringSwitchJumpTable(int tableIndex) { ASSERT(m_rareData); return m_rareData->m_stringSwitchJumpTables[tableIndex]; }


        SymbolTable* symbolTable() { return m_symbolTable; }
        SharedSymbolTable* sharedSymbolTable() { ASSERT(m_codeType == FunctionCode); return static_cast<SharedSymbolTable*>(m_symbolTable); }

        EvalCodeCache& evalCodeCache() { createRareDataIfNecessary(); return m_rareData->m_evalCodeCache; }

        void shrinkToFit();

        // FIXME: Make these remaining members private.

        int m_numCalleeRegisters;
        int m_numVars;
        int m_numParameters;

    private:
#if !defined(NDEBUG) || ENABLE(OPCODE_SAMPLING)
        void dump(ExecState*, const Vector<Instruction>::const_iterator& begin, Vector<Instruction>::const_iterator&) const;
#endif

        void reparseForExceptionInfoIfNecessary(CallFrame*);

        void createRareDataIfNecessary()
        {
            if (!m_rareData)
                m_rareData.set(new RareData);
        }

        ScriptExecutable* m_ownerExecutable;
        JSGlobalData* m_globalData;

        Vector<Instruction> m_instructions;
#ifndef NDEBUG
        unsigned m_instructionCount;
#endif

        int m_thisRegister;

        bool m_needsFullScopeChain;
        bool m_usesEval;
        bool m_usesArguments;
        bool m_isNumericCompareFunction;

        CodeType m_codeType;

        RefPtr<SourceProvider> m_source;
        unsigned m_sourceOffset;

#if !ENABLE(JIT)
        Vector<unsigned> m_propertyAccessInstructions;
        Vector<unsigned> m_globalResolveInstructions;
#else
        Vector<StructureStubInfo> m_structureStubInfos;
        Vector<GlobalResolveInfo> m_globalResolveInfos;
        Vector<CallLinkInfo> m_callLinkInfos;
        Vector<MethodCallLinkInfo> m_methodCallLinkInfos;
        Vector<CallLinkInfo*> m_linkedCallerList;
#endif

        Vector<unsigned> m_jumpTargets;

        // Constant Pool
        Vector<Identifier> m_identifiers;
        Vector<Register> m_constantRegisters;
        Vector<RefPtr<FunctionExecutable> > m_functionDecls;
        Vector<RefPtr<FunctionExecutable> > m_functionExprs;

        SymbolTable* m_symbolTable;

        OwnPtr<ExceptionInfo> m_exceptionInfo;

        struct RareData : FastAllocBase {
            Vector<HandlerInfo> m_exceptionHandlers;

            // Rare Constants
            Vector<RefPtr<RegExp> > m_regexps;

            // Jump Tables
            Vector<SimpleJumpTable> m_immediateSwitchJumpTables;
            Vector<SimpleJumpTable> m_characterSwitchJumpTables;
            Vector<StringJumpTable> m_stringSwitchJumpTables;

            EvalCodeCache m_evalCodeCache;

#if ENABLE(JIT)
            Vector<FunctionRegisterInfo> m_functionRegisterInfos;
#endif
        };
        OwnPtr<RareData> m_rareData;
    };

    // Program code is not marked by any function, so we make the global object
    // responsible for marking it.

    class GlobalCodeBlock : public CodeBlock {
    public:
        GlobalCodeBlock(ScriptExecutable* ownerExecutable, CodeType codeType, PassRefPtr<SourceProvider> sourceProvider, unsigned sourceOffset, JSGlobalObject* globalObject)
            : CodeBlock(ownerExecutable, codeType, sourceProvider, sourceOffset, &m_unsharedSymbolTable)
            , m_globalObject(globalObject)
        {
            m_globalObject->codeBlocks().add(this);
        }

        ~GlobalCodeBlock()
        {
            if (m_globalObject)
                m_globalObject->codeBlocks().remove(this);
        }

        void clearGlobalObject() { m_globalObject = 0; }

    private:
        JSGlobalObject* m_globalObject; // For program and eval nodes, the global object that marks the constant pool.
        SymbolTable m_unsharedSymbolTable;
    };

    class ProgramCodeBlock : public GlobalCodeBlock {
    public:
        ProgramCodeBlock(ProgramExecutable* ownerExecutable, CodeType codeType, JSGlobalObject* globalObject, PassRefPtr<SourceProvider> sourceProvider)
            : GlobalCodeBlock(ownerExecutable, codeType, sourceProvider, 0, globalObject)
        {
        }
    };

    class EvalCodeBlock : public GlobalCodeBlock {
    public:
        EvalCodeBlock(EvalExecutable* ownerExecutable, JSGlobalObject* globalObject, PassRefPtr<SourceProvider> sourceProvider, int baseScopeDepth)
            : GlobalCodeBlock(ownerExecutable, EvalCode, sourceProvider, 0, globalObject)
            , m_baseScopeDepth(baseScopeDepth)
        {
        }

        int baseScopeDepth() const { return m_baseScopeDepth; }

        const Identifier& variable(unsigned index) { return m_variables[index]; }
        unsigned numVariables() { return m_variables.size(); }
        void adoptVariables(Vector<Identifier>& variables)
        {
            ASSERT(m_variables.isEmpty());
            m_variables.swap(variables);
        }

    private:
        int m_baseScopeDepth;
        Vector<Identifier> m_variables;
    };

    class FunctionCodeBlock : public CodeBlock {
    public:
        // Rather than using the usual RefCounted::create idiom for SharedSymbolTable we just use new
        // as we need to initialise the CodeBlock before we could initialise any RefPtr to hold the shared
        // symbol table, so we just pass as a raw pointer with a ref count of 1.  We then manually deref
        // in the destructor.
        FunctionCodeBlock(FunctionExecutable* ownerExecutable, CodeType codeType, PassRefPtr<SourceProvider> sourceProvider, unsigned sourceOffset)
            : CodeBlock(ownerExecutable, codeType, sourceProvider, sourceOffset, new SharedSymbolTable)
        {
        }
        ~FunctionCodeBlock()
        {
            sharedSymbolTable()->deref();
        }
    };

    inline Register& ExecState::r(int index)
    {
        CodeBlock* codeBlock = this->codeBlock();
        if (codeBlock->isConstantRegisterIndex(index))
            return codeBlock->constantRegister(index);
        return this[index];
    }

} // namespace JSC

#endif // CodeBlock_h