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.concurrent.marksweep;
014    
015    import org.mmtk.plan.TraceLocal;
016    import org.mmtk.plan.Trace;
017    import org.mmtk.policy.Space;
018    
019    import org.vmmagic.pragma.*;
020    import org.vmmagic.unboxed.*;
021    
022    /**
023     * This class implements the thread-local functionality for a transitive
024     * closure over a mark-sweep space.
025     */
026    @Uninterruptible
027    public final class CMSTraceLocal extends TraceLocal {
028      /**
029       * Constructor
030       */
031      public CMSTraceLocal(Trace trace) {
032        super(trace);
033      }
034    
035      /****************************************************************************
036       *
037       * Externally visible Object processing and tracing
038       */
039    
040      /**
041       * {@inheritDoc}
042       */
043      @Override
044      protected boolean overwriteReferenceDuringTrace() {
045        return false;
046      }
047    
048      @Override
049      public boolean isLive(ObjectReference object) {
050        if (object.isNull()) return false;
051        if (Space.isInSpace(CMS.MARK_SWEEP, object)) {
052          return CMS.msSpace.isLive(object);
053        }
054        return super.isLive(object);
055      }
056    
057      /**
058       * {@inheritDoc}<p>
059       *
060       * In this instance, we refer objects in the mark-sweep space to the
061       * msSpace for tracing, and defer to the superclass for all others.
062       */
063      @Override
064      @Inline
065      public ObjectReference traceObject(ObjectReference object) {
066        if (object.isNull()) return object;
067        if (Space.isInSpace(CMS.MARK_SWEEP, object))
068          return CMS.msSpace.traceObject(this, object);
069        return super.traceObject(object);
070      }
071    }