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GenImmixMatureTraceLocal.java
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GenImmixMatureTraceLocal.java
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/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Common Public License (CPL);
* You may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.opensource.org/licenses/cpl1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.mmtk.plan.generational.immix;
import static org.mmtk.policy.immix.ImmixConstants.MARK_LINE_AT_SCAN_TIME;
import org.mmtk.plan.generational.GenCollector;
import org.mmtk.plan.generational.GenMatureTraceLocal;
import org.mmtk.plan.Trace;
import org.mmtk.policy.Space;
import org.mmtk.policy.immix.ImmixSpace;
import org.vmmagic.unboxed.*;
import org.vmmagic.pragma.*;
/**
* This class implements the core functionality for a transitive
* closure over the heap graph, specifically in a generational immix
* collector.
*/
@Uninterruptible
public final class GenImmixMatureTraceLocal extends GenMatureTraceLocal{
/**
* Constructor
*/
public GenImmixMatureTraceLocal(Trace global, GenCollector plan) {
super(GenImmix.SCAN_IMMIX, global, plan);
}
/**
* This method is the core method during the trace of the object graph.
* The role of this method is to:
*
* 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 (object.isNull()) return object;
if (Space.isInSpace(GenImmix.IMMIX, object)) {
return GenImmix.immixSpace.fastTraceObject(this, object);
}
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 (object.isNull()) return false;
if (Space.isInSpace(GenImmix.IMMIX, object)) {
return GenImmix.immixSpace.isLive(object);
}
return super.isLive(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 (Space.isInSpace(GenImmix.IMMIX, object)) {
return true;
}
return super.willNotMoveInCurrentCollection(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) {
super.scanObject(object);
if (MARK_LINE_AT_SCAN_TIME && Space.isInSpace(GenImmix.IMMIX, object))
ImmixSpace.markLines(object);
}
}