protected IsNullValue mergeValues(IsNullValueFrame frame, int slot, IsNullValue a, IsNullValue b) throws DataflowAnalysisException { return IsNullValue.merge(a, b);
protected void mergeValues(IsNullValueFrame otherFrame, IsNullValueFrame resultFrame, int slot) throws DataflowAnalysisException { IsNullValue value = IsNullValue.merge(resultFrame.getValue(slot), otherFrame.getValue(slot)); resultFrame.setValue(slot, value);
	protected IsNullValue mergeValues(IsNullValueFrame frame, int slot, IsNullValue a, IsNullValue b)	        throws DataflowAnalysisException {		return IsNullValue.merge(a, b);	}