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.utility.alloc.LinearScan;
017    
018    import org.vmmagic.pragma.*;
019    import org.vmmagic.unboxed.*;
020    
021    /**
022     * This class is used in backup tracing to sweep and zero any dead 'immortal' objects.
023     */
024    @Uninterruptible
025    public final class BTSweepImmortalScanner extends LinearScan {
026    
027      /**
028       * Scan an object during sweep.
029       *
030       * @param object The source of the reference.
031       */
032      @Override
033      @Inline
034      public void scan(ObjectReference object) {
035        if (!RCHeader.isMarked(object)) {
036          // do nothing
037        } else {
038          RCHeader.clearMarked(object);
039        }
040      }
041    }