obstack_init(&obst);
irg_block_walk_graph(irg, init_block_link, NULL, &obst);
irg_walk_graph(irg, collect_phis, NULL, NULL);
irg_block_walk_graph(irg, NULL, if_conv_walker, &p);
obstack_init(&obst);
irg_block_walk_graph(irg, init_block_link, NULL, &obst);
irg_walk_graph(irg, collect_phis, NULL, NULL);
irg_block_walk_graph(irg, NULL, if_conv_walker, &p);