alias: Change return type of predicate functions from int to bool
Also remove a bunch of unneeded forward declarations.
gcc/ChangeLog:
* rtl.h (true_dependence): Change return type from int to bool.
(canon_true_dependence): Ditto.
(read_dependence): Ditto.
(anti_dependence): Ditto.
(canon_anti_dependence): Ditto.
(output_dependence): Ditto.
(canon_output_dependence): Ditto.
(may_alias_p): Ditto.
* alias.h (alias_sets_conflict_p): Ditto.
(alias_sets_must_conflict_p): Ditto.
(objects_must_conflict_p): Ditto.
(nonoverlapping_memrefs_p): Ditto.
* alias.cc (rtx_equal_for_memref_p): Remove forward declaration.
(record_set): Ditto.
(base_alias_check): Ditto.
(find_base_value): Ditto.
(mems_in_disjoint_alias_sets_p): Ditto.
(get_alias_set_entry): Ditto.
(decl_for_component_ref): Ditto.
(write_dependence_p): Ditto.
(memory_modified_1): Ditto.
(mems_in_disjoint_alias_set_p): Change return type from int to bool
and adjust function body accordingly.
(alias_sets_conflict_p): Ditto.
(alias_sets_must_conflict_p): Ditto.
(objects_must_conflict_p): Ditto.
(rtx_equal_for_memref_p): Ditto.
(base_alias_check): Ditto.
(read_dependence): Ditto.
(nonoverlapping_memrefs_p): Ditto.
(true_dependence_1): Ditto.
(true_dependence): Ditto.
(canon_true_dependence): Ditto.
(write_dependence_p): Ditto.
(anti_dependence): Ditto.
(canon_anti_dependence): Ditto.
(output_dependence): Ditto.
(canon_output_dependence): Ditto.
(may_alias_p): Ditto.
(init_alias_analysis): Change "changed" variable to bool.