IPA ICF: use fibonacci heap instead of list as a worklist.

IPA ICF: use fibonacci heap instead of list as a worklist.

2019-06-04  Martin Liska  <mliska@suse.cz>

	* ipa-icf.c (sem_item_optimizer::add_item_to_class): Count
	number of references.
	(sem_item_optimizer::do_congruence_step):
	(sem_item_optimizer::worklist_push): Dump how references
	a class has.
	(sem_item_optimizer::worklist_pop): Use heap.
	(sem_item_optimizer::process_cong_reduction): Likewise.
	* ipa-icf.h: Use fibonacci_heap insteam of std::list.

From-SVN: r271901