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.semispace;
014    
015    import org.mmtk.plan.TraceLocal;
016    import org.mmtk.plan.Trace;
017    import org.mmtk.policy.Space;
018    
019    import org.vmmagic.pragma.*;
020    import org.vmmagic.unboxed.*;
021    
022    /**
023     * This class implements the core functionality for a transitive
024     * closure over the heap graph.
025     */
026    @Uninterruptible
027    public class SSTraceLocal extends TraceLocal {
028      /**
029       * Constructor
030       */
031      public SSTraceLocal(Trace trace, boolean specialized) {
032        super(specialized ? SS.SCAN_SS : -1, trace);
033      }
034    
035      /**
036       * Constructor
037       */
038      public SSTraceLocal(Trace trace) {
039        this(trace, true);
040      }
041    
042      /****************************************************************************
043       *
044       * Externally visible Object processing and tracing
045       */
046    
047      /**
048       * {@inheritDoc}
049       */
050      @Override
051      public boolean isLive(ObjectReference object) {
052        if (object.isNull()) return false;
053        if (Space.isInSpace(SS.SS0, object))
054          return SS.hi ? SS.copySpace0.isLive(object) : true;
055        if (Space.isInSpace(SS.SS1, object))
056          return SS.hi ? true : SS.copySpace1.isLive(object);
057        return super.isLive(object);
058      }
059    
060    
061      @Override
062      @Inline
063      public ObjectReference traceObject(ObjectReference object) {
064        if (object.isNull()) return object;
065        if (Space.isInSpace(SS.SS0, object))
066          return SS.copySpace0.traceObject(this, object, SS.ALLOC_SS);
067        if (Space.isInSpace(SS.SS1, object))
068          return SS.copySpace1.traceObject(this, object, SS.ALLOC_SS);
069        return super.traceObject(object);
070      }
071    
072      /**
073       * Will this object move from this point on, during the current trace ?
074       *
075       * @param object The object to query.
076       * @return True if the object will not move.
077       */
078      @Override
079      public boolean willNotMoveInCurrentCollection(ObjectReference object) {
080        return (SS.hi && !Space.isInSpace(SS.SS0, object)) ||
081               (!SS.hi && !Space.isInSpace(SS.SS1, object));
082      }
083    }