+
+ /* In case of a follower -> leader transition of a Phi node
+ * we have to ensure that the current partition will be split
+ * by lambda n.(n[i].partition).
+ *
+ * This split may already happened before when some predecessors
+ * of the Phi's Block are unreachable. Thus, we have to put the
+ * current partition in the worklist to repeat the check.
+ */
+ if (is_Phi(x->node) && ! x->part->on_worklist)
+ add_to_worklist(x->part, env);