| /* |
| * This file is part of the Jikes RVM project (http://jikesrvm.org). |
| * |
| * This file is licensed to You under the Eclipse Public License (EPL); |
| * 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/eclipse-1.0.php |
| * |
| * See the COPYRIGHT.txt file distributed with this work for information |
| * regarding copyright ownership. |
| */ |
| package org.mmtk.plan.markcompact; |
| |
| import org.mmtk.plan.TraceLocal; |
| import org.mmtk.plan.Trace; |
| import org.mmtk.policy.Space; |
| import org.mmtk.vm.VM; |
| |
| import org.vmmagic.pragma.*; |
| import org.vmmagic.unboxed.*; |
| |
| /** |
| * This class implments the thread-local functionality for a transitive |
| * closure over a mark-compact space during the forwarding phase. |
| */ |
| @Uninterruptible |
| public final class MCForwardTraceLocal extends TraceLocal { |
| /** |
| * Constructor |
| */ |
| public MCForwardTraceLocal(Trace trace) { |
| super(MC.SCAN_FORWARD, trace); |
| } |
| |
| /**************************************************************************** |
| * |
| * Externally visible Object processing and tracing |
| */ |
| |
| /** |
| * Is the specified object live? |
| * |
| * @param object The object. |
| * @return True if the object is live. |
| */ |
| public boolean isLive(ObjectReference object) { |
| if (object.isNull()) return false; |
| if (Space.isInSpace(MC.MARK_COMPACT, object)) { |
| return MC.mcSpace.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 |
| public ObjectReference traceObject(ObjectReference object) { |
| if (object.isNull()) return object; |
| if (Space.isInSpace(MC.MARK_COMPACT, object)) |
| return MC.mcSpace.traceForwardObject(this, object); |
| return super.traceObject(object); |
| } |
| |
| /** |
| * Will this object move from this point on, during the current trace ? |
| * |
| * @param object The object to query. |
| * @return True if the object will not move. |
| */ |
| public boolean willNotMoveInCurrentCollection(ObjectReference object) { |
| return !Space.isInSpace(MC.MARK_COMPACT, object); |
| } |
| |
| /** |
| * Ensure that this object will not move for the rest of the GC. |
| * |
| * @param object The object that must not move |
| * @return The new object, guaranteed stable for the rest of the GC. |
| */ |
| @Inline |
| public ObjectReference precopyObject(ObjectReference object) { |
| if (VM.VERIFY_ASSERTIONS) { |
| // All precopying must occur during the initial trace. |
| VM.assertions._assert(!Space.isInSpace(MC.MARK_COMPACT, object)); |
| } |
| return super.precopyObject(object); |
| } |
| |
| } |