derefOffsetMap.remove(vn);
derefLocationSetMap.remove(vn);
	public void mergeWith(UnconditionalValueDerefSet fact, ValueNumberFactory valueNumberFactory) {		valueNumberSet.and(fact.valueNumberSet);				for (int i = 0; i < numValueNumbersInMethod; i++) {			ValueNumber vn = valueNumberFactory.forNumber(i);			if (valueNumberSet.get(i)) {				BitSet derefLocationSet = derefOffsetMap.get(vn);				derefLocationSet.or(fact.derefOffsetMap.get(vn));			} else {				// The value number is not in the fact:				// remove its location set				derefOffsetMap.remove(vn);			}		}	}