irg_walk_blkwise_graph(irg, NULL, topo_walker, &a_env);
/* clean the exp_gen set. Doing this here saves the cleanup in the iteration. */
+ inc_irg_visited(irg);
for (bl_info = a_env.list; bl_info != NULL; bl_info = bl_info->next) {
ir_valueset_iterator_t iter;