/**
* Given a slot (ie the address of an ObjectReference), ensure that the referent will not move for
* the rest of the GC. This is achieved by calling the precopyObject method.
*
* @param slot The slot to check
*/
@Inline
public final void processPrecopyEdge(Address slot) {
ObjectReference child = slot.loadObjectReference();
if (!child.isNull()) {
child = precopyObject(child);
slot.store(child);
}
}
/**
* Trace a reference during GC. This involves determining which collection policy applies and
* calling the appropriate <code>trace</code> method.
*
* @param target The object the interior edge points within.
* @param slot The location of the interior edge.
* @param root True if this is a root edge.
*/
public final void processInteriorEdge(ObjectReference target, Address slot, boolean root) {
Address interiorRef = slot.loadAddress();
Offset offset = interiorRef.diff(target.toAddress());
ObjectReference newTarget = traceObject(target, root);
if (VM.VERIFY_ASSERTIONS) {
if (offset.sLT(Offset.zero()) || offset.sGT(Offset.fromIntSignExtend(1 << 24))) {
// There is probably no object this large
Log.writeln("ERROR: Suspiciously large delta to interior pointer");
Log.write(" object base = ");
Log.writeln(target);
Log.write(" interior reference = ");
Log.writeln(interiorRef);
Log.write(" delta = ");
Log.writeln(offset);
VM.assertions._assert(false);
}
}
slot.store(newTarget.toAddress().plus(offset));
}
/**
* This method is the core method during the trace of the object graph. The role of this method is
* to:
*
* <p>1. Ensure the traced object is not collected. 2. If this is the first visit to the object
* enqueue it to be scanned. 3. Return the forwarded reference to the object.
*
* @param object The object to be traced.
* @return The new reference to the same object instance.
*/
@Inline
public ObjectReference traceObject(ObjectReference object) {
if (Space.isInSpace(Plan.VM_SPACE, object))
return (Plan.SCAN_BOOT_IMAGE) ? object : Plan.vmSpace.traceObject(this, object);
if (Space.isInSpace(Plan.IMMORTAL, object)) return Plan.immortalSpace.traceObject(this, object);
if (Space.isInSpace(Plan.LOS, object)) return Plan.loSpace.traceObject(this, object);
if (Space.isInSpace(Plan.PLOS, object)) return Plan.ploSpace.traceObject(this, object);
if (Plan.USE_CODE_SPACE && Space.isInSpace(Plan.SMALL_CODE, object))
return Plan.smallCodeSpace.traceObject(this, object);
if (Plan.USE_CODE_SPACE && Space.isInSpace(Plan.LARGE_CODE, object))
return Plan.largeCodeSpace.traceObject(this, object);
if (VM.VERIFY_ASSERTIONS)
VM.assertions._assert(false, "No special case for space in traceObject");
return ObjectReference.nullReference();
}
/**
* Return true if the object resides within the nursery
*
* @param obj The object to be tested
* @return true if the object resides within the nursery
*/
@Inline
static boolean inNursery(ObjectReference obj) {
return inNursery(obj.toAddress());
}
