+/**
+ * Visitor: initializes the list-heads and set the out-count
+ * of all nodes to 0 of nodes that are not seen so far.
+ */
+static void visitor(ir_node *irn, void *data) {
+ if (irn_not_visited(irn)) {
+ mark_irn_visited(irn);
+ init_lh_walker(irn, data);
+ }
+}
+
+/*
+ * Build the initial edge set.
+ * Beware, this is not a simple task because it suffers from two
+ * difficulties:
+ * - the anchor set allows access to Nodes that may not be reachable from
+ * the End node
+ * - the identities add nodes to the "root set" that are not yet reachable
+ * from End. However, after some transformations, the CSE may revival these
+ * nodes
+ *
+ * These problems can be fixed using different strategies:
+ * - Add an age flag to every node. Whenever the edge of a node is older
+ * then the current edge, invalidate the edges of this node.
+ * While this would help for revivaled nodes, it increases memory and runtime.
+ * - Delete the identities set.
+ * Solves the revival problem, but may increase the memory consumption, as
+ * nodes cannot be revivaled at all.
+ * - Manually iterate over the identities root set. This did not consume more memory
+ * but increase the computation time because the |identies| >= |V|
+ *
+ * Currently, we use the last option.
+ */