ipa: Multiple predicates for loop properties, with frequencies

This patch enhances the ability of IPA to reason under what conditions
loops in a function have known iteration counts or strides because it
replaces single predicates which currently hold conjunction of
predicates for all loops with vectors capable of holding multiple
predicates, each with a cumulative frequency of loops with the
property.

This second property is then used by IPA-CP to much more aggressively
boost its heuristic score for cloning opportunities which make
iteration counts or strides of frequent loops compile time constant.

gcc/ChangeLog:

2020-09-03  Martin Jambor  <mjambor@suse.cz>

	* ipa-fnsummary.h (ipa_freqcounting_predicate): New type.
	(ipa_fn_summary): Change the type of loop_iterations and loop_strides
	to vectors of ipa_freqcounting_predicate.
	(ipa_fn_summary::ipa_fn_summary): Construct the new vectors.
	(ipa_call_estimates): New fields loops_with_known_iterations and
	loops_with_known_strides.
	* ipa-cp.c (hint_time_bonus): Multiply param_ipa_cp_loop_hint_bonus
	with the expected frequencies of loops with known iteration count or
	stride.
	* ipa-fnsummary.c (add_freqcounting_predicate): New function.
	(ipa_fn_summary::~ipa_fn_summary): Release the new vectors instead of
	just two predicates.
	(remap_hint_predicate_after_duplication): Replace with function
	remap_freqcounting_preds_after_dup.
	(ipa_fn_summary_t::duplicate): Use it or duplicate new vectors.
	(ipa_dump_fn_summary): Dump the new vectors.
	(analyze_function_body): Compute the loop property vectors.
	(ipa_call_context::estimate_size_and_time): Calculate also
	loops_with_known_iterations and loops_with_known_strides.  Adjusted
	dumping accordinly.
	(remap_hint_predicate): Replace with function
	remap_freqcounting_predicate.
	(ipa_merge_fn_summary_after_inlining): Use it.
	(inline_read_section): Stream loopcounting vectors instead of two
	simple predicates.
	(ipa_fn_summary_write): Likewise.
	* params.opt (ipa-max-loop-predicates): New parameter.
	* doc/invoke.texi (ipa-max-loop-predicates): Document new param.

gcc/testsuite/ChangeLog:

2020-09-03  Martin Jambor  <mjambor@suse.cz>

	* gcc.dg/ipa/ipcp-loophint-1.c: New test.

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