private void step4() {
for (int i = 2; i < n; i++) {
CFANode w = vertex.get(i);
NodeInfo infow = map.get(w);
CFANode d = dom.get(w);
if (!(d.equals(vertex.get(infow.semi)))) {
CFANode dd = dom.get(d);
dom.put(d, dd);
}
}
if (mode == 0) {
dom.put(entry, null);
} else {
dom.put(exit, null);
}
}
