001    /*
002     *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003     *
004     *  This file is licensed to You under the Eclipse Public License (EPL);
005     *  You may not use this file except in compliance with the License. You
006     *  may obtain a copy of the License at
007     *
008     *      http://www.opensource.org/licenses/eclipse-1.0.php
009     *
010     *  See the COPYRIGHT.txt file distributed with this work for information
011     *  regarding copyright ownership.
012     */
013    package org.mmtk.plan.refcount.generational;
014    
015    import org.mmtk.plan.TraceLocal;
016    import org.mmtk.plan.Trace;
017    import org.mmtk.plan.refcount.RCHeader;
018    import org.mmtk.policy.Space;
019    import org.mmtk.utility.deque.ObjectReferenceDeque;
020    import org.mmtk.vm.VM;
021    
022    import org.vmmagic.pragma.*;
023    import org.vmmagic.unboxed.*;
024    
025    /**
026     * This class implements the thread-local core functionality for a transitive
027     * closure over the heap graph.
028     */
029    @Uninterruptible
030    public final class GenRCFindRootSetTraceLocal extends TraceLocal {
031    
032      private final ObjectReferenceDeque rootBuffer;
033    
034      /**
035       * Constructor
036       */
037      public GenRCFindRootSetTraceLocal(Trace trace, ObjectReferenceDeque rootBuffer) {
038        super(trace);
039        this.rootBuffer = rootBuffer;
040      }
041    
042      /****************************************************************************
043       *
044       * Externally visible Object processing and tracing
045       */
046    
047      /**
048       * Is the specified object reachable?
049       *
050       * @return <code>true</code> if the object is reachable.
051       */
052      @Override
053      public boolean isLive(ObjectReference object) {
054        return GenRC.isRCObject(object) && RCHeader.isLiveRC(object) ||
055              (!Space.isInSpace(GenRC.NURSERY, object) && super.isLive(object));
056      }
057    
058      /**
059       * When we trace a non-root object we do nothing.
060       */
061      @Override
062      @Inline
063      public ObjectReference traceObject(ObjectReference object) {
064        return traceObject(object, false);
065      }
066    
067      /**
068       * When we trace a root object we remember it.
069       */
070      @Override
071      @Inline
072      public ObjectReference traceObject(ObjectReference object, boolean root) {
073        if (object.isNull()) return object;
074    
075        if (Space.isInSpace(GenRC.NURSERY, object)) {
076          object = GenRC.nurserySpace.traceObject(this, object, GenRC.ALLOC_RC);
077        } else if (!GenRC.isRCObject(object)) {
078          return object;
079        }
080    
081        if (root) {
082          rootBuffer.push(object);
083        } else {
084          RCHeader.incRC(object);
085        }
086    
087        return object;
088      }
089    
090      @Override
091      public boolean willNotMoveInCurrentCollection(ObjectReference object) {
092        if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!object.isNull());
093        return !(Space.isInSpace(GenRC.NURSERY, object));
094      }
095    }