ipa-cp: Work with time benefits and frequencies in sreals

ipa-cp: Work with time benefits and frequencies in sreals

This patch converts the variables that hold time benefits and
frequencies in IPA-CP from plain integers to sreals, avoiding the need
to cap them to avoid overflows and also fixing a potential underflows.

Size costs corresponding to individual constants are left as ints so
that they do not take up too much space.  Care must be taken that
adding it up does not overflow, especially in the case of
prop_size_cost, because in cases of extremely long chains of lattice
dependencies it can overflow (e.g. in testsuite/gcc.dg/ipa/pr50744.c).
The overall size is already tracked in long ints.

gcc/ChangeLog:

2020-11-11  Martin Jambor  <mjambor@suse.cz>

	* ipa-cp.c (class ipcp_value_base): Change the type of
	local_time_benefit and prop_time_benefit to sreal.  Adjust the
	constructor initializer.
	(ipcp_lattice::print): Dump sreals.
	(struct caller_statistics): Change the type of freq_sum to sreal.
	(gather_caller_stats): Work with sreal freq_sum.
	(incorporate_penalties): Work with sreal evaluation.
	(good_cloning_opportunity_p): Adjusted for sreal sreal time_benefit
	and freq_sum.  Bail out if size_cost is INT_MAX.
	(perform_estimation_of_a_value): Work with sreal time_benefit.  Avoid
	unnecessary capping.
	(estimate_local_effects): Pass sreal time benefit to
	good_cloning_opportunity_p without capping it.  Adjust dumping.
	(safe_add): If there can be overflow, return INT_MAX.
	(propagate_effects): Work with sreal times.
	(get_info_about_necessary_edges): Work with sreal frequencies.
	(decide_about_value): Likewise and with sreal time benefits.