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.markcompact;
014    
015    import org.mmtk.plan.StopTheWorldConstraints;
016    
017    import org.mmtk.policy.MarkCompactSpace;
018    import org.mmtk.policy.MarkCompactLocal;
019    
020    import 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
029    public class MCConstraints extends StopTheWorldConstraints {
030      @Override
031      public boolean movesObjects() { return true; }
032      @Override
033      public boolean needsForwardAfterLiveness() { return true; }
034      @Override
035      public boolean needsLinearScan() { return true; }
036      @Override
037      public int maxNonLOSDefaultAllocBytes() { return MarkCompactLocal.MINIMUM_DATA_SIZE; }
038      @Override
039      public int gcHeaderBits() { return MarkCompactSpace.LOCAL_GC_BITS_REQUIRED; }
040      @Override
041      public int gcHeaderWords() { return MarkCompactSpace.GC_HEADER_WORDS_REQUIRED; }
042      @Override
043      public int numSpecializedScans() { return 2; }
044    }