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.immix;
014
015import static org.mmtk.policy.immix.ImmixConstants.MARK_LINE_AT_SCAN_TIME;
016
017import org.mmtk.plan.TraceLocal;
018import org.mmtk.plan.Trace;
019import org.mmtk.policy.Space;
020import org.mmtk.utility.HeaderByte;
021import org.mmtk.utility.deque.ObjectReferenceDeque;
022import org.mmtk.vm.VM;
023
024import org.vmmagic.pragma.*;
025import org.vmmagic.unboxed.*;
026
027/**
028 * This class implements the thread-local functionality for a transitive
029 * closure over an immix space.
030 */
031@Uninterruptible
032public final class ImmixTraceLocal extends TraceLocal {
033
034  /****************************************************************************
035  *
036  * Instance fields
037  */
038 private final ObjectReferenceDeque modBuffer;
039
040  /**
041   * Constructor
042   *
043   * @param trace The trace associated with this trace local.
044   * @param modBuffer The modified objects buffer associated with this trace local.  Possibly null.
045   */
046  public ImmixTraceLocal(Trace trace, ObjectReferenceDeque modBuffer) {
047    super(Immix.SCAN_IMMIX, trace);
048    this.modBuffer = modBuffer;
049  }
050
051  /****************************************************************************
052   *
053   * Externally visible Object processing and tracing
054   */
055
056  /**
057   * {@inheritDoc}
058   */
059  @Override
060  public boolean isLive(ObjectReference object) {
061    if (object.isNull()) return false;
062    if (Space.isInSpace(Immix.IMMIX, object)) {
063      return Immix.immixSpace.fastIsLive(object);
064    }
065    return super.isLive(object);
066  }
067
068  /**
069   * {@inheritDoc}<p>
070   *
071   * In this instance, we refer objects in the mark-sweep space to the
072   * immixSpace for tracing, and defer to the superclass for all others.
073   *
074   * @param object The object to be traced.
075   * @return The new reference to the same object instance.
076   */
077  @Override
078  @Inline
079  public ObjectReference traceObject(ObjectReference object) {
080    if (object.isNull()) return object;
081    if (Space.isInSpace(Immix.IMMIX, object))
082      return Immix.immixSpace.fastTraceObject(this, object);
083    return super.traceObject(object);
084  }
085
086  /**
087   * Ensure that the referenced object will not move from this point through
088   * to the end of the collection. This can involve forwarding the object
089   * if necessary.
090   */
091  @Inline
092  @Override
093  public boolean willNotMoveInCurrentCollection(ObjectReference object) {
094    if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!Immix.immixSpace.inImmixDefragCollection());
095    return true;
096  }
097
098  @Inline
099  @Override
100  protected void scanObject(ObjectReference object) {
101    super.scanObject(object);
102    if (MARK_LINE_AT_SCAN_TIME && Space.isInSpace(Immix.IMMIX, object))
103      Immix.immixSpace.markLines(object);
104  }
105
106  /**
107   * Process any remembered set entries.  This means enumerating the
108   * mod buffer and for each entry, marking the object as unlogged
109   * (we don't enqueue for scanning since we're doing a full heap GC).
110   */
111  @Override
112  protected void processRememberedSets() {
113    if (modBuffer != null) {
114      logMessage(5, "clearing modBuffer");
115      while (!modBuffer.isEmpty()) {
116        ObjectReference src = modBuffer.pop();
117        HeaderByte.markAsUnlogged(src);
118      }
119    }
120  }
121}