re PR debug/42977 ("-fcompare-debug failure" with "-O2 -finline-functions -fomit-frame-pointer -ftracer -fsched2-use-superblocks -fPIC")

	PR debug/42977
	* cselib.c (n_useless_values): Document handling of debug locs.
	(n_useless_debug_values, n_debug_values): New variables.
	(new_elt_loc_list): Don't add to debug values, keep count.
	(promote_debug_loc): New.
	(cselib_reset_table): Zero new variables.
	(entry_and_rtx_equal_p): Promote debug locs.
	(discard_useless_locs): Increment n_useless_debug_values for
	debug values.
	(remove_useless_values): Adjust n_useless_values and n_debug_values
	with n_useless_debug_values.
	(add_mem_for_addr): Promote debug locs.
	(cselib_lookup_mem): Likewise.
	(cselib_lookup_addr): Renamed to...
	(cselib_lookup_addr_1): ... this.  Promote debug locs.
	Don't call...
	(cselib_log_lookup): ... this.  Turn into...
	(cselib_lookup_addr): ... new wrapper.
	(cselib_lookup_from_insn): New.
	(cselib_invalidate_regno): Increment n_useless_debug_values for
	debug values.
	(cselib_invalidate_mem): Likewise.
	(cselib_process_insn): Take n_deleted and n_debug_values into
	account to guard remove_useless_value call.
	(cselib_finish): Zero n_useless_debug_values.
	* cselib.h (cselib_lookup_from_insn): Declare.
	* sched-deps.c (sched_analyze_1): Use cselib_lookup_from_insn.
	(sched_analyze_2): Likewise.

From-SVN: r157837