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.backuptrace;
014    
015    import org.mmtk.plan.refcount.RCHeader;
016    import org.mmtk.policy.ExplicitLargeObjectSpace;
017    
018    import org.vmmagic.pragma.*;
019    import org.vmmagic.unboxed.*;
020    
021    /**
022     * This class implements the freeing of large objects during a backup trace.
023     */
024    @Uninterruptible
025    public final class BTFreeLargeObjectSweeper extends ExplicitLargeObjectSpace.Sweeper {
026    
027      @Override
028      public boolean sweepLargeObject(ObjectReference object) {
029        if (!RCHeader.isMarked(object)) {
030          // Free the object
031          return true;
032        }
033        // Clear the mark-bit and retain the object.
034        RCHeader.clearMarked(object);
035        return false;
036      }
037    }