C++ StructureSet类代码示例

FiltrationResult AbstractValue::filter(Graph& graph, const StructureSet& other)
{
    if (isClear())
        return FiltrationOK;
    
    // FIXME: This could be optimized for the common case of m_type not
    // having structures, array modes, or a specific value.
    // https://bugs.webkit.org/show_bug.cgi?id=109663
    
    m_type &= other.speculationFromStructures();
    m_arrayModes &= other.arrayModesFromStructures();
    m_currentKnownStructure.filter(other);
    
    // It's possible that prior to the above two statements we had (Foo, TOP), where
    // Foo is a SpeculatedType that is disjoint with the passed StructureSet. In that
    // case, we will now have (None, [someStructure]). In general, we need to make
    // sure that new information gleaned from the SpeculatedType needs to be fed back
    // into the information gleaned from the StructureSet.
    m_currentKnownStructure.filter(m_type);
    
    if (m_currentKnownStructure.hasSingleton())
        setFuturePossibleStructure(graph, m_currentKnownStructure.singleton());
        
    filterArrayModesByType();
    filterValueByType();
    return normalizeClarity();
}

bool StructureSet::merge(const StructureSet& other)
{
    if (other.isThin()) {
        if (other.singleStructure())
            return add(other.singleStructure());
        return false;
    }

    OutOfLineList* list = other.structureList();
    if (list->m_length >= 2) {
        if (isThin()) {
            OutOfLineList* myNewList = OutOfLineList::create(
                                           list->m_length + !!singleStructure());
            if (singleStructure()) {
                myNewList->m_length = 1;
                myNewList->list()[0] = singleStructure();
            }
            set(myNewList);
        }
        bool changed = false;
        for (unsigned i = 0; i < list->m_length; ++i)
            changed |= addOutOfLine(list->list()[i]);
        return changed;
    }

    ASSERT(list->m_length);
    return add(list->list()[0]);
}

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;
}

bool StructureSet::isSubsetOf(const StructureSet& other) const
{
    if (isThin()) {
        if (!singleStructure())
            return true;
        return other.contains(singleStructure());
    }

    if (other.isThin()) {
        if (!other.singleStructure())
            return false;
        OutOfLineList* list = structureList();
        if (list->m_length >= 2)
            return false;
        if (list->list()[0] == other.singleStructure())
            return true;
        return false;
    }

    OutOfLineList* list = structureList();
    for (unsigned i = 0; i < list->m_length; ++i) {
        if (!other.containsOutOfLine(list->list()[i]))
            return false;
    }
    return true;
}

void StructureSet::exclude(const StructureSet& other)
{
    if (other.isThin()) {
        if (other.singleStructure())
            remove(other.singleStructure());
        return;
    }

    if (isThin()) {
        if (!singleStructure())
            return;
        if (other.contains(singleStructure()))
            clear();
        return;
    }

    OutOfLineList* list = structureList();
    for (unsigned i = 0; i < list->m_length; ++i) {
        if (!other.containsOutOfLine(list->list()[i]))
            continue;
        list->list()[i--] = list->list()[--list->m_length];
    }
    if (!list->m_length)
        clear();
}

 void noticeStructureCheck(VariableAccessData* variable, const StructureSet& set)
 {
     if (set.size() != 1) {
         noticeStructureCheck(variable, 0);
         return;
     }
     noticeStructureCheck(variable, set.singletonStructure());
 }

void AbstractValue::set(Graph& graph, const StructureSet& set)
{
    m_structure = set;
    m_arrayModes = set.arrayModesFromStructures();
    m_type = set.speculationFromStructures();
    m_value = JSValue();
    
    checkConsistency();
    assertIsRegistered(graph);
}

void StructureSet::copyFromOutOfLine(const StructureSet& other)
{
    ASSERT(!other.isThin() && other.m_pointer != reservedValue);
    OutOfLineList* otherList = other.structureList();
    OutOfLineList* myList = OutOfLineList::create(otherList->m_length);
    myList->m_length = otherList->m_length;
    for (unsigned i = otherList->m_length; i--;)
        myList->list()[i] = otherList->list()[i];
    set(myList);
}

FiltrationResult AbstractValue::changeStructure(Graph& graph, const StructureSet& other)
{
    m_type &= other.speculationFromStructures();
    m_arrayModes = other.arrayModesFromStructures();
    m_structure = other;
    
    filterValueByType();
    
    return normalizeClarity(graph);
}

void StructureSet::filter(const StructureSet& other)
{
    if (other.isThin()) {
        if (!other.singleStructure() || !contains(other.singleStructure()))
            clear();
        else {
            clear();
            set(other.singleStructure());
        }
        return;
    }

    ContainsOutOfLine containsOutOfLine(other);
    genericFilter(containsOutOfLine);
}

void StructureAbstractValue::observeTransitions(const TransitionVector& vector)
{
    SAMPLE("StructureAbstractValue observeTransitions");

    if (isTop())
        return;

    StructureSet newStructures;
    for (unsigned i = vector.size(); i--;) {
        ASSERT(!vector[i].previous->dfgShouldWatch());

        if (!m_set.contains(vector[i].previous))
            continue;

        newStructures.add(vector[i].next);
    }

    if (!m_set.merge(newStructures))
        return;

    if (m_set.size() > polymorphismLimit)
        makeTop();
}

GetByIdVariant::GetByIdVariant(
    const StructureSet& structureSet, PropertyOffset offset,
    const ObjectPropertyConditionSet& conditionSet,
    std::unique_ptr<CallLinkStatus> callLinkStatus,
    JSFunction* intrinsicFunction)
    : m_structureSet(structureSet)
    , m_conditionSet(conditionSet)
    , m_offset(offset)
    , m_callLinkStatus(WTFMove(callLinkStatus))
    , m_intrinsicFunction(intrinsicFunction)
{
    if (!structureSet.size()) {
        ASSERT(offset == invalidOffset);
        ASSERT(conditionSet.isEmpty());
    }
    if (intrinsicFunction)
        ASSERT(intrinsic() != NoIntrinsic);
}

GetByIdVariant::GetByIdVariant(
    const StructureSet& structureSet, PropertyOffset offset,
    const IntendedStructureChain* chain, std::unique_ptr<CallLinkStatus> callLinkStatus)
    : m_structureSet(structureSet)
    , m_alternateBase(nullptr)
    , m_offset(offset)
    , m_callLinkStatus(WTF::move(callLinkStatus))
{
    if (!structureSet.size()) {
        ASSERT(offset == invalidOffset);
        ASSERT(!chain);
    }
    
    if (chain && chain->size()) {
        m_alternateBase = chain->terminalPrototype();
        chain->gatherChecks(m_constantChecks);
    }
}

 void registerStructures(const StructureSet& set)
 {
     for (unsigned i = set.size(); i--;)
         registerStructure(set[i]);
 }

PutByIdStatus PutByIdStatus::computeFor(JSGlobalObject* globalObject, const StructureSet& set, UniquedStringImpl* uid, bool isDirect)
{
    if (parseIndex(*uid))
        return PutByIdStatus(TakesSlowPath);

    if (set.isEmpty())
        return PutByIdStatus();
    
    PutByIdStatus result;
    result.m_state = Simple;
    for (unsigned i = 0; i < set.size(); ++i) {
        Structure* structure = set[i];
        
        if (structure->typeInfo().overridesGetOwnPropertySlot() && structure->typeInfo().type() != GlobalObjectType)
            return PutByIdStatus(TakesSlowPath);

        if (!structure->propertyAccessesAreCacheable())
            return PutByIdStatus(TakesSlowPath);
    
        unsigned attributes;
        PropertyOffset offset = structure->getConcurrently(uid, attributes);
        if (isValidOffset(offset)) {
            if (attributes & CustomAccessor)
                return PutByIdStatus(MakesCalls);

            if (attributes & (Accessor | ReadOnly))
                return PutByIdStatus(TakesSlowPath);
            
            WatchpointSet* replaceSet = structure->propertyReplacementWatchpointSet(offset);
            if (!replaceSet || replaceSet->isStillValid()) {
                // When this executes, it'll create, and fire, this replacement watchpoint set.
                // That means that  this has probably never executed or that something fishy is
                // going on. Also, we cannot create or fire the watchpoint set from the concurrent
                // JIT thread, so even if we wanted to do this, we'd need to have a lazy thingy.
                // So, better leave this alone and take slow path.
                return PutByIdStatus(TakesSlowPath);
            }

            PutByIdVariant variant =
                PutByIdVariant::replace(structure, offset, structure->inferredTypeDescriptorFor(uid));
            if (!result.appendVariant(variant))
                return PutByIdStatus(TakesSlowPath);
            continue;
        }
    
        // Our hypothesis is that we're doing a transition. Before we prove that this is really
        // true, we want to do some sanity checks.
    
        // Don't cache put transitions on dictionaries.
        if (structure->isDictionary())
            return PutByIdStatus(TakesSlowPath);

        // If the structure corresponds to something that isn't an object, then give up, since
        // we don't want to be adding properties to strings.
        if (!structure->typeInfo().isObject())
            return PutByIdStatus(TakesSlowPath);
    
        ObjectPropertyConditionSet conditionSet;
        if (!isDirect) {
            conditionSet = generateConditionsForPropertySetterMissConcurrently(
                globalObject->vm(), globalObject, structure, uid);
            if (!conditionSet.isValid())
                return PutByIdStatus(TakesSlowPath);
        }
    
        // We only optimize if there is already a structure that the transition is cached to.
        Structure* transition =
            Structure::addPropertyTransitionToExistingStructureConcurrently(structure, uid, 0, offset);
        if (!transition)
            return PutByIdStatus(TakesSlowPath);
        ASSERT(isValidOffset(offset));
    
        bool didAppend = result.appendVariant(
            PutByIdVariant::transition(
                structure, transition, conditionSet, offset,
                transition->inferredTypeDescriptorFor(uid)));
        if (!didAppend)
            return PutByIdStatus(TakesSlowPath);
    }
    
    return result;
}