tree-optimization/112653 - PTA and return

tree-optimization/112653 - PTA and return

The following separates the escape solution for return stmts not
only during points-to solving but also for later querying.  This
requires adjusting the points-to-global tests to include escapes
through returns.  Technically the patch replaces the existing
post-processing which computes the transitive closure of the
returned value solution by a proper artificial variable with
transitive closure constraints.  Instead of adding the solution
to escaped we track it separately.

	PR tree-optimization/112653
	* gimple-ssa.h (gimple_df): Add escaped_return solution.
	* tree-ssa.cc (init_tree_ssa): Reset it.
	(delete_tree_ssa): Likewise.
	* tree-ssa-structalias.cc (escaped_return_id): New.
	(find_func_aliases): Handle non-IPA return stmts by
	adding to ESCAPED_RETURN.
	(set_uids_in_ptset): Adjust HEAP escaping to also cover
	escapes through return.
	(init_base_vars): Initialize ESCAPED_RETURN.
	(compute_points_to_sets): Replace ESCAPED post-processing
	with recording the ESCAPED_RETURN solution.
	* tree-ssa-alias.cc (ref_may_alias_global_p_1): Check
	the ESCAPED_RETUNR solution.
	(dump_alias_info): Dump it.
	* cfgexpand.cc (update_alias_info_with_stack_vars): Update it.
	* ipa-icf.cc (sem_item_optimizer::fixup_points_to_sets):
	Likewise.
	* tree-inline.cc (expand_call_inline): Reset it.
	* tree-parloops.cc (parallelize_loops): Likewise.
	* tree-sra.cc (maybe_add_sra_candidate): Check it.

	* gcc.dg/tree-ssa/pta-return-1.c: New testcase.

(cherry picked from commit f7884f7673444b8a2c10ea0981d480f2e82dd16a)