C++ GetByIdStatus::appendVariant方法代码示例

GetByIdStatus GetByIdStatus::computeFor(const StructureSet& set, StringImpl* uid)
{
    // For now we only handle the super simple self access case. We could handle the
    // prototype case in the future.
    
    if (set.isEmpty())
        return GetByIdStatus();

    if (toUInt32FromStringImpl(uid) != PropertyName::NotAnIndex)
        return GetByIdStatus(TakesSlowPath);
    
    GetByIdStatus result;
    result.m_state = Simple;
    result.m_wasSeenInJIT = false;
    for (unsigned i = 0; i < set.size(); ++i) {
        Structure* structure = set[i];
        if (structure->typeInfo().overridesGetOwnPropertySlot() && structure->typeInfo().type() != GlobalObjectType)
            return GetByIdStatus(TakesSlowPath);
        
        if (!structure->propertyAccessesAreCacheable())
            return GetByIdStatus(TakesSlowPath);
        
        unsigned attributes;
        PropertyOffset offset = structure->getConcurrently(uid, attributes);
        if (!isValidOffset(offset))
            return GetByIdStatus(TakesSlowPath); // It's probably a prototype lookup. Give up on life for now, even though we could totally be way smarter about it.
        if (attributes & Accessor)
            return GetByIdStatus(MakesCalls); // We could be smarter here, like strenght-reducing this to a Call.
        
        if (!result.appendVariant(GetByIdVariant(structure, offset)))
            return GetByIdStatus(TakesSlowPath);
    }
    
    return result;
}

GetByIdStatus GetByIdStatus::computeForStubInfoWithoutExitSiteFeedback(
    const ConcurrentJITLocker& locker, CodeBlock* profiledBlock, StructureStubInfo* stubInfo, UniquedStringImpl* uid,
    CallLinkStatus::ExitSiteData callExitSiteData)
{
    if (!stubInfo || !stubInfo->everConsidered)
        return GetByIdStatus(NoInformation);

    PolymorphicAccess* list = 0;
    State slowPathState = TakesSlowPath;
    if (stubInfo->cacheType == CacheType::Stub) {
        list = stubInfo->u.stub;
        for (unsigned i = 0; i < list->size(); ++i) {
            const AccessCase& access = list->at(i);
            if (access.doesCalls())
                slowPathState = MakesCalls;
        }
    }
    
    if (stubInfo->tookSlowPath)
        return GetByIdStatus(slowPathState);
    
    // Finally figure out if we can derive an access strategy.
    GetByIdStatus result;
    result.m_state = Simple;
    result.m_wasSeenInJIT = true; // This is interesting for bytecode dumping only.
    switch (stubInfo->cacheType) {
    case CacheType::Unset:
        return GetByIdStatus(NoInformation);
        
    case CacheType::GetByIdSelf: {
        Structure* structure = stubInfo->u.byIdSelf.baseObjectStructure.get();
        if (structure->takesSlowPathInDFGForImpureProperty())
            return GetByIdStatus(slowPathState, true);
        unsigned attributesIgnored;
        GetByIdVariant variant;
        variant.m_offset = structure->getConcurrently(uid, attributesIgnored);
        if (!isValidOffset(variant.m_offset))
            return GetByIdStatus(slowPathState, true);
        
        variant.m_structureSet.add(structure);
        bool didAppend = result.appendVariant(variant);
        ASSERT_UNUSED(didAppend, didAppend);
        return result;
    }
        
    case CacheType::Stub: {
        for (unsigned listIndex = 0; listIndex < list->size(); ++listIndex) {
            const AccessCase& access = list->at(listIndex);
            if (access.viaProxy())
                return GetByIdStatus(slowPathState, true);
            
            Structure* structure = access.structure();
            if (!structure) {
                // The null structure cases arise due to array.length and string.length. We have no way
                // of creating a GetByIdVariant for those, and we don't really have to since the DFG
                // handles those cases in FixupPhase using value profiling. That's a bit awkward - we
                // shouldn't have to use value profiling to discover something that the AccessCase
                // could have told us. But, it works well enough. So, our only concern here is to not
                // crash on null structure.
                return GetByIdStatus(slowPathState, true);
            }
            
            ComplexGetStatus complexGetStatus = ComplexGetStatus::computeFor(
                structure, access.conditionSet(), uid);
             
            switch (complexGetStatus.kind()) {
            case ComplexGetStatus::ShouldSkip:
                continue;
                 
            case ComplexGetStatus::TakesSlowPath:
                return GetByIdStatus(slowPathState, true);
                 
            case ComplexGetStatus::Inlineable: {
                std::unique_ptr<CallLinkStatus> callLinkStatus;
                JSFunction* intrinsicFunction = nullptr;

                switch (access.type()) {
                case AccessCase::Load: {
                    break;
                }
                case AccessCase::IntrinsicGetter: {
                    intrinsicFunction = access.intrinsicFunction();
                    break;
                }
                case AccessCase::Getter: {
                    CallLinkInfo* callLinkInfo = access.callLinkInfo();
                    ASSERT(callLinkInfo);
                    callLinkStatus = std::make_unique<CallLinkStatus>(
                        CallLinkStatus::computeFor(
                            locker, profiledBlock, *callLinkInfo, callExitSiteData));
                    break;
                }
                default: {
                    // FIXME: It would be totally sweet to support more of these at some point in the
                    // future. https://bugs.webkit.org/show_bug.cgi?id=133052
                    return GetByIdStatus(slowPathState, true);
                } }
                 
                GetByIdVariant variant(
                    StructureSet(structure), complexGetStatus.offset(),
//.........这里部分代码省略.........

GetByIdStatus GetByIdStatus::computeForStubInfo(
    const ConcurrentJITLocker& locker, CodeBlock* profiledBlock, StructureStubInfo* stubInfo, StringImpl* uid,
    CallLinkStatus::ExitSiteData callExitSiteData)
{
    if (!stubInfo || !stubInfo->seen)
        return GetByIdStatus(NoInformation);
    
    PolymorphicGetByIdList* list = 0;
    State slowPathState = TakesSlowPath;
    if (stubInfo->accessType == access_get_by_id_list) {
        list = stubInfo->u.getByIdList.list;
        for (unsigned i = 0; i < list->size(); ++i) {
            const GetByIdAccess& access = list->at(i);
            if (access.doesCalls())
                slowPathState = MakesCalls;
        }
    }
    
    // Finally figure out if we can derive an access strategy.
    GetByIdStatus result;
    result.m_state = Simple;
    result.m_wasSeenInJIT = true; // This is interesting for bytecode dumping only.
    switch (stubInfo->accessType) {
    case access_unset:
        return GetByIdStatus(NoInformation);
        
    case access_get_by_id_self: {
        Structure* structure = stubInfo->u.getByIdSelf.baseObjectStructure.get();
        if (structure->takesSlowPathInDFGForImpureProperty())
            return GetByIdStatus(slowPathState, true);
        unsigned attributesIgnored;
        GetByIdVariant variant;
        variant.m_offset = structure->getConcurrently(uid, attributesIgnored);
        if (!isValidOffset(variant.m_offset))
            return GetByIdStatus(slowPathState, true);
        
        variant.m_structureSet.add(structure);
        bool didAppend = result.appendVariant(variant);
        ASSERT_UNUSED(didAppend, didAppend);
        return result;
    }
        
    case access_get_by_id_list: {
        for (unsigned listIndex = 0; listIndex < list->size(); ++listIndex) {
            Structure* structure = list->at(listIndex).structure();
            
            ComplexGetStatus complexGetStatus = ComplexGetStatus::computeFor(
                profiledBlock, structure, list->at(listIndex).chain(),
                list->at(listIndex).chainCount(), uid);
             
            switch (complexGetStatus.kind()) {
            case ComplexGetStatus::ShouldSkip:
                continue;
                 
            case ComplexGetStatus::TakesSlowPath:
                return GetByIdStatus(slowPathState, true);
                 
            case ComplexGetStatus::Inlineable: {
                std::unique_ptr<CallLinkStatus> callLinkStatus;
                switch (list->at(listIndex).type()) {
                case GetByIdAccess::SimpleInline:
                case GetByIdAccess::SimpleStub: {
                    break;
                }
                case GetByIdAccess::Getter: {
                    AccessorCallJITStubRoutine* stub = static_cast<AccessorCallJITStubRoutine*>(
                        list->at(listIndex).stubRoutine());
                    callLinkStatus = std::make_unique<CallLinkStatus>(
                        CallLinkStatus::computeFor(
                            locker, profiledBlock, *stub->m_callLinkInfo, callExitSiteData));
                    break;
                }
                case GetByIdAccess::CustomGetter:
                case GetByIdAccess::WatchedStub:{
                    // FIXME: It would be totally sweet to support this at some point in the future.
                    // https://bugs.webkit.org/show_bug.cgi?id=133052
                    return GetByIdStatus(slowPathState, true);
                }
                default:
                    RELEASE_ASSERT_NOT_REACHED();
                }
                 
                GetByIdVariant variant(
                    StructureSet(structure), complexGetStatus.offset(), complexGetStatus.chain(),
                    std::move(callLinkStatus));
                 
                if (!result.appendVariant(variant))
                    return GetByIdStatus(slowPathState, true);
                break;
            } }
        }
        
        return result;
    }
        
    default:
        return GetByIdStatus(slowPathState, true);
    }
    
    RELEASE_ASSERT_NOT_REACHED();
//.........这里部分代码省略.........

GetByIdStatus GetByIdStatus::computeForStubInfo(
    const ConcurrentJITLocker&, CodeBlock* profiledBlock, StructureStubInfo* stubInfo,
    StringImpl* uid)
{
    if (!stubInfo || !stubInfo->seen)
        return GetByIdStatus(NoInformation);
    
    if (stubInfo->resetByGC)
        return GetByIdStatus(TakesSlowPath, true);

    PolymorphicGetByIdList* list = 0;
    if (stubInfo->accessType == access_get_by_id_list) {
        list = stubInfo->u.getByIdList.list;
        for (unsigned i = 0; i < list->size(); ++i) {
            if (list->at(i).doesCalls())
                return GetByIdStatus(MakesCalls, true);
        }
    }
    
    // Finally figure out if we can derive an access strategy.
    GetByIdStatus result;
    result.m_state = Simple;
    result.m_wasSeenInJIT = true; // This is interesting for bytecode dumping only.
    switch (stubInfo->accessType) {
    case access_unset:
        return GetByIdStatus(NoInformation);
        
    case access_get_by_id_self: {
        Structure* structure = stubInfo->u.getByIdSelf.baseObjectStructure.get();
        if (structure->takesSlowPathInDFGForImpureProperty())
            return GetByIdStatus(TakesSlowPath, true);
        unsigned attributesIgnored;
        JSCell* specificValue;
        GetByIdVariant variant;
        variant.m_offset = structure->getConcurrently(
            *profiledBlock->vm(), uid, attributesIgnored, specificValue);
        if (!isValidOffset(variant.m_offset))
            return GetByIdStatus(TakesSlowPath, true);
        
        if (structure->isDictionary())
            specificValue = 0;
        
        variant.m_structureSet.add(structure);
        variant.m_specificValue = JSValue(specificValue);
        result.appendVariant(variant);
        return result;
    }
        
    case access_get_by_id_list: {
        for (unsigned listIndex = 0; listIndex < list->size(); ++listIndex) {
            ASSERT(!list->at(listIndex).doesCalls());
            
            Structure* structure = list->at(listIndex).structure();
            if (structure->takesSlowPathInDFGForImpureProperty())
                return GetByIdStatus(TakesSlowPath, true);
            
            if (list->at(listIndex).chain()) {
                RefPtr<IntendedStructureChain> chain = adoptRef(new IntendedStructureChain(
                    profiledBlock, structure, list->at(listIndex).chain(),
                    list->at(listIndex).chainCount()));
                if (!result.computeForChain(profiledBlock, uid, chain))
                    return GetByIdStatus(TakesSlowPath, true);
                continue;
            }
            
            unsigned attributesIgnored;
            JSCell* specificValue;
            PropertyOffset myOffset = structure->getConcurrently(
                *profiledBlock->vm(), uid, attributesIgnored, specificValue);
            if (structure->isDictionary())
                specificValue = 0;
            
            if (!isValidOffset(myOffset))
                return GetByIdStatus(TakesSlowPath, true);

            bool found = false;
            for (unsigned variantIndex = 0; variantIndex < result.m_variants.size(); ++variantIndex) {
                GetByIdVariant& variant = result.m_variants[variantIndex];
                if (variant.m_chain)
                    continue;
                
                if (variant.m_offset != myOffset)
                    continue;

                found = true;
                if (variant.m_structureSet.contains(structure))
                    break;
                
                if (variant.m_specificValue != JSValue(specificValue))
                    variant.m_specificValue = JSValue();
                
                variant.m_structureSet.add(structure);
                break;
            }
            
            if (found)
                continue;
            
            if (!result.appendVariant(GetByIdVariant(StructureSet(structure), myOffset, specificValue)))
                return GetByIdStatus(TakesSlowPath, true);
//.........这里部分代码省略.........