codeblock.h

linux下开源浏览器WebKit的源码,市面上的很多商用浏览器都是移植自WebKit

/*
 * Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
 * Copyright (C) 2008 Cameron Zwarich <[e-mail]>
 *
 * 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 "RegExp.h"
#include "UString.h"
#include <wtf/RefPtr.h>
#include <wtf/Vector.h>

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

namespace JSC {

    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)
        MacroAssembler::CodeLocationLabel nativeCode;
#endif
    };

#if ENABLE(JIT)
    // The code, and the associated pool from which it was allocated.
    struct JITCodeRef {
        JITCode code;
#ifndef NDEBUG
        unsigned codeSize;
#endif
        RefPtr<ExecutablePool> executablePool;

        JITCodeRef()
            : code(0)
#ifndef NDEBUG
            , codeSize(0)
#endif
        {
        }
        
        JITCodeRef(void* code, PassRefPtr<ExecutablePool> executablePool)
            : code(code)
#ifndef NDEBUG
            , codeSize(0)
#endif
            , executablePool(executablePool)
        {
        }
    };
#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;
        MacroAssembler::CodeLocationNearCall callReturnLocation;
        MacroAssembler::CodeLocationDataLabelPtr hotPathBegin;
        MacroAssembler::CodeLocationNearCall hotPathOther;
        MacroAssembler::CodeLocationLabel coldPathOther;
        CodeBlock* callee;
        unsigned position;
        
        void setUnlinked() { callee = 0; }
        bool isLinked() { return callee; }
    };

    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.calleeReturnAddressValue();
    }

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

    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

    class CodeBlock {
        friend class JIT;
    public:
        CodeBlock(ScopeNode* ownerNode, CodeType, PassRefPtr<SourceProvider>, unsigned sourceOffset);
        ~CodeBlock();

        void mark();
        void refStructures(Instruction* vPC) const;
        void derefStructures(Instruction* vPC) const;
#if ENABLE(JIT)
        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 isConstantRegisterIndex(int index)
        {
            return index >= m_numVars && index < m_numVars + m_numConstants;
        }

        ALWAYS_INLINE JSValuePtr getConstant(int index)
        {
            return m_constantRegisters[index - m_numVars].getJSValue();
        }

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

        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;