BitSet derefLocationSet = derefLocationSetMap.get(vn); derefLocationSet.or(fact.derefLocationSetMap.get(vn));
Set<Location> derefLocationSet = derefLocationSetMap.get(vn); derefLocationSet.addAll(fact.derefLocationSetMap.get(vn));
	public void mergeWith(UnconditionalValueDerefSet fact, ValueNumberFactory valueNumberFactory) {		// Compute the intersection of the unconditionally dereferenced value sets		valueNumberSet.and(fact.valueNumberSet);		// For each unconditionally dereferenced value...		for (int i = 0; i < numValueNumbersInMethod; i++) {			ValueNumber vn = valueNumberFactory.forNumber(i);			if (valueNumberSet.get(i)) {				// Compute the union of the dereference locations for				// this value number.				BitSet derefLocationSet = derefLocationSetMap.get(vn);				derefLocationSet.or(fact.derefLocationSetMap.get(vn));			} else {				// The value number is not in the fact:				// remove its location set				derefLocationSetMap.remove(vn);			}		}	}