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 */
013package org.mmtk.plan.refcount.fullheap;
014
015import org.mmtk.plan.TraceLocal;
016import org.mmtk.plan.Trace;
017import org.mmtk.plan.refcount.RCBase;
018import org.mmtk.plan.refcount.RCHeader;
019import org.mmtk.utility.deque.ObjectReferenceDeque;
020
021import org.vmmagic.pragma.*;
022import 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
029public final class RCFindRootSetTraceLocal extends TraceLocal {
030
031  private final ObjectReferenceDeque rootBuffer;
032
033  public RCFindRootSetTraceLocal(Trace trace, ObjectReferenceDeque rootBuffer) {
034    super(trace);
035    this.rootBuffer = rootBuffer;
036  }
037
038  /****************************************************************************
039   *
040   * Externally visible Object processing and tracing
041   */
042
043  /**
044   * Is the specified object reachable?
045   *
046   * @param object The object.
047   * @return <code>true</code> if the object is reachable.
048   */
049  @Override
050  public boolean isLive(ObjectReference object) {
051    return RCBase.isRCObject(object) && RCHeader.isLiveRC(object) || super.isLive(object);
052  }
053
054  /**
055   * When we trace a non-root object we do nothing.
056   *
057   * @param object The object to be traced.
058   * @return The new reference to the same object instance.
059   */
060  @Override
061  @Inline
062  public ObjectReference traceObject(ObjectReference object) {
063    return object;
064  }
065
066  /**
067   * When we trace a root object we remember it.
068   *
069   * @param object The object to be traced.
070   * @return The new reference to the same object instance.
071   */
072  @Override
073  @Inline
074  public ObjectReference traceObject(ObjectReference object, boolean root) {
075    if (root && RCBase.isRCObject(object)) {
076      rootBuffer.push(object);
077    }
078    return object;
079  }
080}