Changing cost propagation and ordering colorable bucket heuristics for PR93564.

Changing cost propagation and ordering colorable bucket heuristics for PR93564.

2020-02-23  Vladimir Makarov  <vmakarov@redhat.com>

	PR rtl-optimization/93564
	* ira-color.c (struct update_cost_queue_elem): New member start.
	(queue_update_cost, get_next_update_cost): Add new arg start.
	(allocnos_conflict_p): New function.
	(update_costs_from_allocno): Add new arg conflict_cost_update_p.
	Add checking conflicts with allocnos_conflict_p.
	(update_costs_from_prefs, restore_costs_from_copies): Adjust
	update_costs_from_allocno calls.
	(update_conflict_hard_regno_costs): Add checking conflicts with
	allocnos_conflict_p.  Adjust calls of queue_update_cost and
	get_next_update_cost.
	(assign_hard_reg): Adjust calls of queue_update_cost.  Add
	debugging print.
	(bucket_allocno_compare_func): Restore previous version.