/*
* 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.refcount.cd;
import org.vmmagic.pragma.*;
import org.vmmagic.unboxed.*;
/**
* This class implements the global state of a null cycle detector.
*/
@Uninterruptible public final class NullCD extends CD {
/*****************************************************************************
*
* Collection
*/
/**
* Update the CD section of the RC word when an increment is performed
*
* @param rcWord The refcount word after the increment.
* @return The updated status after CD modification
*/
public int notifyIncRC(int rcWord) {
// Nothing to do;
return rcWord;
}
/**
* If the reported decrement succeeds, should we buffer the object?
*
* @param rcWord The refcount work post decrement.
* @return The updated status after CD modification
*/
public boolean shouldBufferOnDecRC(int rcWord) {
// Never
return false;
}
/**
* Allow a free of this object, or is it in a CD data structure
*
* @param object The object to check
* @return True if free is safe
*/
public boolean allowFree(ObjectReference object) {
// Always safe
return true;
}
/**
* Update the header on a buffered dec to non-zero RC
*
* @param rcWord The refcount work post decrement.
* @return The updated status after CD modification
*/
public int updateHeaderOnBufferedDec(int rcWord) {
return rcWord;
}
/**
* Update the header on a non-buffered dec to non-zero RC
*
* @param rcWord The refcount work post decrement.
* @return The updated status after CD modification
*/
public int updateHeaderOnUnbufferedDec(int rcWord) {
return rcWord;
}
/**
* Perform any cycle detector header initialization.
*
* @param typeRef Type information for the object.
* @param rcWord The refcount work post decrement.
* @return The updated status after CD modification
*/
public int initializeHeader(ObjectReference typeRef, int rcWord) {
return rcWord;
}
}