result.and(fact);
if (isTop(fact)) return; else if (isTop(result)) copy(fact, result); else  result.and(fact);
	public void meetInto(BitSet fact, Edge edge, BitSet result) throws DataflowAnalysisException {		if (ignoreExceptionEdges && edge.isExceptionEdge())			return;		// Meet is intersection		result.and(fact);	}