IPA ICF: rewrite references into a hash_map.

IPA ICF: rewrite references into a hash_map.

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

	* ipa-icf.h (struct sem_usage_pair_hash): New.
	(sem_usage_pair_hash::hash): Likewise.
	(sem_usage_pair_hash::equal): Likewise.
	(struct sem_usage_hash): Likewise.
	* ipa-icf.c (sem_item::sem_item): Initialize
	referenced_by_count.
	(sem_item::add_reference): Register a reference
	in ref_map and not in target->usages.
	(sem_item::setup): Remove initialization of
	dead vectors.
	(sem_item::~sem_item): Remove usage of dead vectors.
	(sem_item::dump): Remove dump of references.
	(sem_item_optimizer::sem_item_optimizer): Initialize
	m_references.
	(sem_item_optimizer::read_section): Remove useless
	dump.
	(sem_item_optimizer::parse_funcs_and_vars): Likewise here.
	(sem_item_optimizer::build_graph): Pass m_references
	to ::add_reference.
	(sem_item_optimizer::verify_classes): Remove usage of dead
	vectors.
	(sem_item_optimizer::traverse_congruence_split): Return true
	when a class is split.
	(sem_item_optimizer::do_congruence_step_for_index): Use
	hash_map for look up of (sem_item *, index). That brings
	significant speed up.
	(sem_item_optimizer::do_congruence_step): Return true
	when a split is done.
	(congruence_class::is_class_used): Use referenced_by_count.
2019-06-04  Martin Liska  <mliska@suse.cz>

	* c-c++-common/goacc/acc-icf.c: Change scanned pattern.
	* gfortran.dg/goacc/pr78027.f90: Likewise.

From-SVN: r271900