if (IsNullValueAnalysisFeatures.TRACK_KNOWN_VALUES) {
this.trackValueNumbers = trackValueNumbers; if (trackValueNumbers) {
	public IsNullValueFrame(int numLocals) {		super(numLocals);		if (IsNullValueAnalysisFeatures.TRACK_KNOWN_VALUES) {			this.knownValueMap = new HashMap<ValueNumber, IsNullValue>();		}	}