C++ Zone::isGCSweeping方法代码示例

Shape *
PropertyTree::lookupChild(ThreadSafeContext *cx, Shape *parent, const StackShape &child)
{
    /* Keep this in sync with the logic of getChild above. */
    Shape *shape = nullptr;

    JS_ASSERT(parent);

    KidsPointer *kidp = &parent->kids;
    if (kidp->isShape()) {
        Shape *kid = kidp->toShape();
        if (kid->matches(child))
            shape = kid;
    } else if (kidp->isHash()) {
        if (KidsHash::Ptr p = kidp->toHash()->readonlyThreadsafeLookup(child))
            shape = *p;
    } else {
        return nullptr;
    }

#if defined(JSGC_INCREMENTAL) && defined(DEBUG)
    if (shape) {
        JS::Zone *zone = shape->arenaHeader()->zone;
        JS_ASSERT(!zone->needsIncrementalBarrier());
        JS_ASSERT(!(zone->isGCSweeping() && !shape->isMarked() &&
                    !shape->arenaHeader()->allocatedDuringIncremental));
    }
#endif

    return shape;
}

bool
GCUntilCacheSweep(JSContext *cx, const Cache& cache)
{
    CHECK(!IsIncrementalGCInProgress(cx));

    JS::Zone* zone = JS::GetObjectZone(global);
    JS::PrepareZoneForGC(zone);
    SliceBudget budget(WorkBudget(1));
    cx->runtime()->gc.startDebugGC(GC_NORMAL, budget);

    CHECK(IsIncrementalGCInProgress(cx));
    CHECK(zone->isGCSweeping());
    CHECK(cache.needsIncrementalBarrier());

    return true;
}

Shape *
PropertyTree::getChild(ExclusiveContext *cx, Shape *parentArg, StackShape &unrootedChild)
{
    RootedShape parent(cx, parentArg);
    JS_ASSERT(parent);

    Shape *existingShape = nullptr;

    /*
     * The property tree has extremely low fan-out below its root in
     * popular embeddings with real-world workloads. Patterns such as
     * defining closures that capture a constructor's environment as
     * getters or setters on the new object that is passed in as
     * |this| can significantly increase fan-out below the property
     * tree root -- see bug 335700 for details.
     */
    KidsPointer *kidp = &parent->kids;
    if (kidp->isShape()) {
        Shape *kid = kidp->toShape();
        if (kid->matches(unrootedChild))
        existingShape = kid;
    } else if (kidp->isHash()) {
        if (KidsHash::Ptr p = kidp->toHash()->lookup(unrootedChild))
        existingShape = *p;
    } else {
        /* If kidp->isNull(), we always insert. */
    }

#ifdef JSGC_INCREMENTAL
    if (existingShape) {
        JS::Zone *zone = existingShape->zone();
        if (zone->needsIncrementalBarrier()) {
            /*
             * We need a read barrier for the shape tree, since these are weak
             * pointers.
             */
            Shape *tmp = existingShape;
            MarkShapeUnbarriered(zone->barrierTracer(), &tmp, "read barrier");
            JS_ASSERT(tmp == existingShape);
        } else if (zone->isGCSweeping() && !existingShape->isMarked() &&
                   !existingShape->arenaHeader()->allocatedDuringIncremental)
        {
            /*
             * The shape we've found is unreachable and due to be finalized, so
             * remove our weak reference to it and don't use it.
             */
            JS_ASSERT(parent->isMarked());
            parent->removeChild(existingShape);
            existingShape = nullptr;
        }
    }
#endif

    if (existingShape)
        return existingShape;

    RootedGeneric<StackShape*> child(cx, &unrootedChild);

    Shape *shape = newShape(cx);
    if (!shape)
        return nullptr;

    new (shape) Shape(*child, parent->numFixedSlots());

    if (!insertChild(cx, parent, shape))
        return nullptr;

    return shape;
}

UnrootedShape
PropertyTree::getChild(JSContext *cx, Shape *parent_, uint32_t nfixed, const StackShape &child)
{
    AssertCanGC();

    {
        UnrootedShape shape = NULL;

        JS_ASSERT(parent_);

        /*
         * The property tree has extremely low fan-out below its root in
         * popular embeddings with real-world workloads. Patterns such as
         * defining closures that capture a constructor's environment as
         * getters or setters on the new object that is passed in as
         * |this| can significantly increase fan-out below the property
         * tree root -- see bug 335700 for details.
         */
        KidsPointer *kidp = &parent_->kids;
        if (kidp->isShape()) {
            UnrootedShape kid = kidp->toShape();
            if (kid->matches(child))
                shape = kid;
        } else if (kidp->isHash()) {
            if (KidsHash::Ptr p = kidp->toHash()->lookup(child))
                shape = *p;
        } else {
            /* If kidp->isNull(), we always insert. */
        }

#ifdef JSGC_INCREMENTAL
        if (shape) {
            JS::Zone *zone = shape->zone();
            if (zone->needsBarrier()) {
                /*
                 * We need a read barrier for the shape tree, since these are weak
                 * pointers.
                 */
                Shape *tmp = shape;
                MarkShapeUnbarriered(zone->barrierTracer(), &tmp, "read barrier");
                JS_ASSERT(tmp == shape);
            } else if (zone->isGCSweeping() && !shape->isMarked() &&
                       !shape->arenaHeader()->allocatedDuringIncremental)
            {
                /*
                 * The shape we've found is unreachable and due to be finalized, so
                 * remove our weak reference to it and don't use it.
                 */
                JS_ASSERT(parent_->isMarked());
                parent_->removeChild(shape);
                shape = NULL;
            }
        }
#endif

        if (shape)
            return shape;
    }

    StackShape::AutoRooter childRoot(cx, &child);
    RootedShape parent(cx, parent_);

    UnrootedShape shape = newShape(cx);
    if (!shape)
        return UnrootedShape(NULL);

    new (shape) Shape(child, nfixed);

    if (!insertChild(cx, parent, shape))
        return UnrootedShape(NULL);

    return shape;
}