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MSTraceLocal.java
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MSTraceLocal.java
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/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Common Public License (CPL);
* You may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.opensource.org/licenses/cpl1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.mmtk.plan.marksweep;
import org.mmtk.plan.Plan;
import org.mmtk.plan.TraceLocal;
import org.mmtk.plan.Trace;
import org.mmtk.policy.Space;
import org.mmtk.utility.deque.ObjectReferenceDeque;
import org.vmmagic.pragma.*;
import org.vmmagic.unboxed.*;
/**
* This class implements the thread-local functionality for a transitive
* closure over a mark-sweep space.
*/
@Uninterruptible
public final class MSTraceLocal extends TraceLocal {
/****************************************************************************
* Instance fields
*/
private final ObjectReferenceDeque modBuffer;
/**
* Constructor
*/
public MSTraceLocal(Trace trace, ObjectReferenceDeque modBuffer) {
super(MS.SCAN_MARK, trace);
this.modBuffer = modBuffer;
}
/****************************************************************************
* Externally visible Object processing and tracing
*/
/**
* Is the specified object live?
*
* @param object The object.
* @return <code>true</code> if the object is live.
*/
@Override
public boolean isLive(ObjectReference object) {
if (object.isNull()) return false;
if (Space.isInSpace(MS.MARK_SWEEP, object)) {
return MS.msSpace.isLive(object);
}
return super.isLive(object);
}
/**
* This method is the core method during the trace of the object graph.
* The role of this method is to:
*
* 1. Ensure the traced object is not collected.
* 2. If this is the first visit to the object enqueue it to be scanned.
* 3. Return the forwarded reference to the object.
*
* In this instance, we refer objects in the mark-sweep space to the
* msSpace for tracing, and defer to the superclass for all others.
*
* @param object The object to be traced.
* @return The new reference to the same object instance.
*/
@Inline
@Override
public ObjectReference traceObject(ObjectReference object) {
if (object.isNull()) return object;
if (Space.isInSpace(MS.MARK_SWEEP, object))
return MS.msSpace.traceObject(this, object);
return super.traceObject(object);
}
/**
* Process any remembered set entries. This means enumerating the
* mod buffer and for each entry, marking the object as unlogged
* (we don't enqueue for scanning since we're doing a full heap GC).
*/
protected void processRememberedSets() {
if (modBuffer != null) {
logMessage(5, "clearing modBuffer");
while (!modBuffer.isEmpty()) {
ObjectReference src = modBuffer.pop();
Plan.markAsUnlogged(src);
}
}
}
}