public LoopFinder(DirectedGraph <T> graph, T entry, DominatorGraph <T> doms)
{
this.graph = graph;
this.entry = entry;
this.loopNodes = new HashSet <T>();
this.nodeColor = new Dictionary <T, NodeColor>();
Debug.Assert(entry != null);
// Find all nodes that can be reached from the back-edge
// predecessors by reversed edges and paint them gray.
foreach (var p in graph.Predecessors(entry))
{
if (doms.DominatesStrictly(entry, p))
{
// Back edge!
if (!nodeColor.ContainsKey(p))
{
// Unvisited back edge!
BackwardVisit(p);
}
}
else if (p == entry)
{
// Self-loop.
loopNodes.Add(p);
}
}
// Find all gray nodes that can be visited from the suspected
// loop entry and color them black. Black nodes belong
// to the loop.
NodeColor color;
if (nodeColor.TryGetValue(entry, out color) &&
color == NodeColor.Gray)
{
ForwardVisit(entry);
}
}
private bool IsBackEdge(Region a, Region b)
{
return doms.DominatesStrictly(b, a);
}
