re PR middle-end/44813 (ipa-split causes ice in ptr_deref_may_alias_decl_p, at tree-ssa-alias.c:173)

	PR middle-end/44813
	* tree-ssa-uninit.c (ssa_undefined_value_p): Result decl is defined
	for functions passed by reference.
	* tree.c (needs_to_live_in_memory): RESULT_DECL don't need to live
	in memory when passed by reference.
	* tree-ssa-ccp.c (get_default_value): Only VAR_DECL is undefined at
	beggining.
	* ipa-split.c (split_function): Cleanup way return value is passed;
	handle SSA DECL_BY_REFERENCE retvals.
	* tree-ssa.c (verify_def): Verify that RESULT_DECL is read only when
	DECL_BY_REFERENCE is set.
	* tree-ssa-structalias.c (get_constraint_for_ssa_var, get_fi_for_callee,
	find_what_p_points_to): Handle RESULT_DECL.
	* tree-inline.c (declare_return_variable): Get new entry_block argument;
	when passing by reference ensure that RESULT_DECL is gimple_val.
	(remap_gimple_op_r): Remap RESULT_DECL ssa name.
	(remap_gimple_stmt): Handle SSA DECL_BY_REFERENCE returns.
	* g++.dg/torture/pr44813.C: New testcase.
	* g++.dg/torture/pr44826.C: New testcase.

From-SVN: r161898