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.fullheap;
014    
015    import org.mmtk.plan.TraceLocal;
016    import org.mmtk.plan.Trace;
017    import org.mmtk.plan.refcount.RCBase;
018    import org.mmtk.plan.refcount.RCHeader;
019    import org.mmtk.utility.deque.ObjectReferenceDeque;
020    
021    import org.vmmagic.pragma.*;
022    import org.vmmagic.unboxed.*;
023    
024    /**
025     * This class implements the thread-local core functionality for a transitive
026     * closure over the heap graph.
027     */
028    @Uninterruptible
029    public final class RCFindRootSetTraceLocal extends TraceLocal {
030    
031      private final ObjectReferenceDeque rootBuffer;
032    
033      /**
034       * Constructor
035       */
036      public RCFindRootSetTraceLocal(Trace trace, ObjectReferenceDeque rootBuffer) {
037        super(trace);
038        this.rootBuffer = rootBuffer;
039      }
040    
041      /****************************************************************************
042       *
043       * Externally visible Object processing and tracing
044       */
045    
046      /**
047       * Is the specified object reachable?
048       *
049       * @param object The object.
050       * @return <code>true</code> if the object is reachable.
051       */
052      @Override
053      public boolean isLive(ObjectReference object) {
054        return RCBase.isRCObject(object) && RCHeader.isLiveRC(object) || super.isLive(object);
055      }
056    
057      /**
058       * When we trace a non-root object we do nothing.
059       *
060       * @param object The object to be traced.
061       * @return The new reference to the same object instance.
062       */
063      @Override
064      @Inline
065      public ObjectReference traceObject(ObjectReference object) {
066        return object;
067      }
068    
069      /**
070       * When we trace a root object we remember it.
071       *
072       * @param object The object to be traced.
073       * @return The new reference to the same object instance.
074       */
075      @Override
076      @Inline
077      public ObjectReference traceObject(ObjectReference object, boolean root) {
078        if (root && RCBase.isRCObject(object)) {
079          rootBuffer.push(object);
080        }
081        return object;
082      }
083    }