re PR middle-end/28071 (A file that can not be compiled in reasonable time/space)

re PR middle-end/28071 (A file that can not be compiled in reasonable time/space)

	PR rtl-optimization/28071
	* basic-block.h (bb_dom_dfs_in, bb_dom_dfs_out): Declare.
	* dominance.c (bb_dom_dfs_in, bb_dom_dfs_out): New functions.
	* tree-into-ssa.c (struct dom_dfsnum): New.
	(cmp_dfsnum, find_dfsnum_interval, prune_unused_phi_nodes): New
	functions.
	(insert_phi_nodes_for): Use prune_unused_phi_nodes instead of
	compute_global_livein.
	(prepare_block_for_update, prepare_use_sites_for): Mark the uses
	in phi nodes in the correct blocks.

From-SVN: r116190