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.markcompact;
014
015import org.mmtk.plan.StopTheWorldConstraints;
016
017import org.mmtk.policy.MarkCompactSpace;
018import org.mmtk.policy.MarkCompactLocal;
019
020import org.vmmagic.pragma.*;
021
022/**
023 * This class and its subclasses communicate to the host VM/Runtime
024 * any features of the selected plan that it needs to know.  This is
025 * separate from the main Plan/PlanLocal class in order to bypass any
026 * issues with ordering of static initialization.
027 */
028@Uninterruptible
029public class MCConstraints extends StopTheWorldConstraints {
030  @Override
031  public boolean movesObjects() {
032    return true;
033  }
034  @Override
035  public boolean needsForwardAfterLiveness() {
036    return true;
037  }
038  @Override
039  public boolean needsLinearScan() {
040    return true;
041  }
042  @Override
043  public int maxNonLOSDefaultAllocBytes() {
044    return MarkCompactLocal.MINIMUM_DATA_SIZE;
045  }
046  @Override
047  public int gcHeaderBits() {
048    return MarkCompactSpace.LOCAL_GC_BITS_REQUIRED;
049  }
050  @Override
051  public int gcHeaderWords() {
052    return MarkCompactSpace.GC_HEADER_WORDS_REQUIRED;
053  }
054  @Override
055  public int numSpecializedScans() {
056    return 2;
057  }
058}