/** {@inheritDoc} */
@Override
public boolean isLive(ObjectReference object) {
if (object.isNull()) return false;
if (Space.isInSpace(SS.SS0, object)) return SS.hi ? SS.copySpace0.isLive(object) : true;
if (Space.isInSpace(SS.SS1, object)) return SS.hi ? true : SS.copySpace1.isLive(object);
return super.isLive(object);
}
@Override
@Inline
public ObjectReference traceObject(ObjectReference object) {
if (object.isNull()) return object;
if (Space.isInSpace(SS.SS0, object))
return SS.copySpace0.traceObject(this, object, SS.ALLOC_SS);
if (Space.isInSpace(SS.SS1, object))
return SS.copySpace1.traceObject(this, object, SS.ALLOC_SS);
return super.traceObject(object);
}
/**
* Ensure that the referenced object will not move from this point through to the end of the
* collection. This can involve forwarding the object if necessary.
*
* <p><i>Non-copying collectors do nothing, copying collectors must override this method in each
* of their trace classes.</i>
*
* @param object The object that must not move during the collection.
* @return True If the object will not move during collection
*/
public boolean willNotMoveInCurrentCollection(ObjectReference object) {
if (!VM.activePlan.constraints().movesObjects()) return true;
if (Space.isInSpace(Plan.LOS, object)) return true;
if (Space.isInSpace(Plan.IMMORTAL, object)) return true;
if (Space.isInSpace(Plan.VM_SPACE, object)) return true;
if (Plan.USE_CODE_SPACE && Space.isInSpace(Plan.SMALL_CODE, object)) return true;
if (Plan.USE_CODE_SPACE && Space.isInSpace(Plan.LARGE_CODE, object)) return true;
if (VM.VERIFY_ASSERTIONS)
VM.assertions._assert(false, "willNotMove not defined properly in subclass");
return false;
}
/**
* 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.
*
* <p>In this instance, we refer objects in the mark-sweep space to the immixSpace for tracing,
* and defer to the superclass for all others.
*
* @param object The object to be traced.
* @return The new reference to the same object instance.
*/
@Inline
public ObjectReference traceObject(ObjectReference object) {
if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
if (object.isNull()) return object;
if (Space.isInSpace(Immix.IMMIX, object))
return Immix.immixSpace.traceObject(this, object, Plan.ALLOC_DEFAULT);
return super.traceObject(object);
}
/**
* Is the specified object live?
*
* @param object The object.
* @return True if the object is live.
*/
public boolean isLive(ObjectReference object) {
if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
if (object.isNull()) return false;
if (Space.isInSpace(Immix.IMMIX, object)) {
return Immix.immixSpace.isLive(object);
}
return super.isLive(object);
}
/**
* Collectors that move objects <b>must</b> override this method. It performs the deferred
* scanning of objects which are forwarded during bootstrap of each copying collection. Because of
* the complexities of the collection bootstrap (such objects are generally themselves
* gc-critical), the forwarding and scanning of the objects must be dislocated. It is an error for
* a non-moving collector to call this method.
*
* @param object The forwarded object to be scanned
*/
@Inline
@Override
protected void scanObject(ObjectReference object) {
if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
super.scanObject(object);
if (MARK_LINE_AT_SCAN_TIME && Space.isInSpace(Immix.IMMIX, object))
Immix.immixSpace.markLines(object);
}
/**
* Can this object ever move. Used by the VM to make decisions about whether it needs to copy IO
* buffers etc.
*
* @param object The object in question
* @return True if it is not possible that the object will ever move.
*/
public boolean willNeverMove(ObjectReference object) {
if (!VM.activePlan.constraints().movesObjects()) return true;
if (Space.isInSpace(LOS, object)) return true;
if (Space.isInSpace(IMMORTAL, object)) return true;
if (Space.isInSpace(VM_SPACE, object)) return true;
if (Space.isInSpace(NON_MOVING, object)) return true;
if (USE_CODE_SPACE && Space.isInSpace(SMALL_CODE, object)) return true;
if (USE_CODE_SPACE && Space.isInSpace(LARGE_CODE, object)) return true;
/*
* Default to false- this preserves correctness over efficiency.
* Individual plans should override for non-moving spaces they define.
*/
return false;
}
/**
* 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();
}
/**
* Will this object move from this point on, during the current trace ?
*
* @param object The object to query.
* @return True if the object will not move.
*/
@Override
public boolean willNotMoveInCurrentCollection(ObjectReference object) {
return (SS.hi && !Space.isInSpace(SS.SS0, object))
|| (!SS.hi && !Space.isInSpace(SS.SS1, object));
}
/**
* @see org.mmtk.plan.Plan#willNeverMove
* @param object Object in question
* @return True if the object will never move
*/
@Override
public boolean willNeverMove(ObjectReference object) {
if (Space.isInSpace(NURSERY, object)) return false;
return super.willNeverMove(object);
}
/**
* Return true if this object is guaranteed not to move during this collection (i.e. this object
* is defintely not an unforwarded object).
*
* @param object
* @return True if this object is guaranteed not to move during this collection.
*/
@Override
public boolean willNotMoveInCurrentCollection(ObjectReference object) {
if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
if (Space.isInSpace(Immix.IMMIX, object)) return Immix.immixSpace.willNotMoveThisGC(object);
return true;
}
