#define SEEN (1u<<0)
#define UNINTERESTING (1u<<1)
#define TREECHANGE (1u<<2)
+#define SHOWN (1u<<3)
+#define TMP_MARK (1u<<4) /* for isolated cases; clean after use */
struct rev_info {
/* Starting list */
/* Traversal flags */
unsigned int dense:1,
+ no_merges:1,
remove_empty_trees:1,
lifo:1,
topo_order:1,