Example #1
0
// In future we may want to cache this transition.
Structure* Structure::preventExtensionsTransition(VM& vm, Structure* structure)
{
    Structure* transition = create(vm, structure);

    // Don't set m_offset, as one can not transition to this.

    DeferGC deferGC(vm.heap);
    structure->materializePropertyMapIfNecessary(vm, deferGC);
    transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
    transition->m_offset = structure->m_offset;
    transition->setDidPreventExtensions(true);
    transition->pin();

    transition->checkOffsetConsistency();
    return transition;
}
Example #2
0
Structure* Structure::nonPropertyTransition(VM& vm, Structure* structure, NonPropertyTransition transitionKind)
{
    unsigned attributes = toAttributes(transitionKind);
    IndexingType indexingType = newIndexingType(structure->indexingTypeIncludingHistory(), transitionKind);

    if (changesIndexingType(transitionKind)) {
        if (JSGlobalObject* globalObject = structure->m_globalObject.get()) {
            if (globalObject->isOriginalArrayStructure(structure)) {
                Structure* result = globalObject->originalArrayStructureForIndexingType(indexingType);
                if (result->indexingTypeIncludingHistory() == indexingType) {
                    structure->didTransitionFromThisStructure();
                    return result;
                }
            }
        }
    }

    Structure* existingTransition;
    if (!structure->isDictionary() && (existingTransition = structure->m_transitionTable.get(0, attributes))) {
        ASSERT(existingTransition->attributesInPrevious() == attributes);
        ASSERT(existingTransition->indexingTypeIncludingHistory() == indexingType);
        return existingTransition;
    }

    DeferGC deferGC(vm.heap);

    Structure* transition = create(vm, structure);
    transition->setAttributesInPrevious(attributes);
    transition->m_blob.setIndexingType(indexingType);

    if (preventsExtensions(transitionKind))
        transition->setDidPreventExtensions(true);

    if (setsDontDeleteOnAllProperties(transitionKind)
            || setsReadOnlyOnNonAccessorProperties(transitionKind)) {
        // We pin the property table on transitions that do wholesale editing of the property
        // table, since our logic for walking the property transition chain to rematerialize the
        // table doesn't know how to take into account such wholesale edits.

        structure->materializePropertyMapIfNecessary(vm, deferGC);
        transition->propertyTable().set(vm, transition, structure->copyPropertyTableForPinning(vm));
        transition->m_offset = structure->m_offset;
        transition->pinForCaching();

        if (transition->propertyTable()) {
            for (auto& entry : *transition->propertyTable().get()) {
                if (setsDontDeleteOnAllProperties(transitionKind))
                    entry.attributes |= DontDelete;
                if (setsReadOnlyOnNonAccessorProperties(transitionKind) && !(entry.attributes & Accessor))
                    entry.attributes |= ReadOnly;
            }
        }
    } else {
        transition->propertyTable().set(vm, transition, structure->takePropertyTableOrCloneIfPinned(vm));
        transition->m_offset = structure->m_offset;
        checkOffset(transition->m_offset, transition->inlineCapacity());
    }

    if (setsReadOnlyOnNonAccessorProperties(transitionKind)
            && transition->propertyTable()
            && !transition->propertyTable()->isEmpty())
        transition->setHasReadOnlyOrGetterSetterPropertiesExcludingProto(true);

    if (structure->isDictionary())
        transition->pin();
    else {
        ConcurrentJITLocker locker(structure->m_lock);
        structure->m_transitionTable.add(vm, transition);
    }

    transition->checkOffsetConsistency();
    return transition;
}