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    import org.mmtk.vm.VM;
018    
019    import org.vmmagic.pragma.*;
020    import org.vmmagic.unboxed.*;
021    
022    /**
023     * This class is used in backup tracing to sweep and zero any dead 'immortal' objects.
024     */
025    @Uninterruptible
026    public final class BTSweepImmortalScanner extends LinearScan {
027    
028      private final BTDecMarkedAndZero sdmAZ = new BTDecMarkedAndZero();
029    
030      /**
031       * Scan an object during sweep.
032       *
033       * @param object The source of the reference.
034       */
035      @Inline
036      public void scan(ObjectReference object) {
037        if (!RCHeader.isMarked(object)) {
038          VM.scanning.scanObject(sdmAZ, object);
039        } else {
040          RCHeader.clearMarked(object);
041        }
042      }
043    }