modulo-sched: speed up DDG analysis (PR90001)

modulo-sched: speed up DDG analysis (PR90001)

	PR rtl-optimization/90001
	* ddg.c (create_ddg): Init max_dist array for each node.
	(free_ddg): Free max_dist array.
	(create_ddg_edge): Use bool field instead of aux union.
	(set_recurrence_length): Use prepared max_dist information instead
	of calling longest_simple_path.
	(create_scc): Remove graph argument, fill node's aux.count with
	SCC id, and move set_recurrence_length call to...
	(create_ddg_all_sccs): ...here, after filling all max_dist arrays
	using Floyd–Warshall-like algorithm.
	(update_dist_to_successors): Remove the whole function.
	(longest_simple_path): Likewise.
	* ddg.h (struct ddg_node): Add max_dist pointer.
	(struct ddg_edge): Use bool field instead of unused aux union.

From-SVN: r279375