Set nonnull attribute to ptr_info_def based on VRP

Set nonnull attribute to ptr_info_def based on VRP
gcc/ChangeLog:

2016-10-18  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* tree-ssa-alias.h (pt_solution_singleton_or_null_p): Renamed from
	pt_solution_singleton_p.
	* tree-ssa-ccp.c (fold_builtin_alloca_with_align): Use renamed
	pt_solution_singleton_or_null_p from pt_solution_singleton_p.
	* tree-ssa-structalias.c (find_what_p_points_to): Preserve
	pointer nonnull computed by VRP.
	Also Conservatively set pt.null to 1.
	(pt_solution_reset): Conservatively set pt.null to 1.
	(pt_solution_singleton_or_null_p): Renamed from
	pt_solution_singleton_p.
	* tree-ssanames.h (set_ptr_nonnull): Declare.
	(get_ptr_nonnull): Likewise.
	* tree-ssanames.c (set_ptr_nonnull): New.
	(get_ptr_nonnull): Likewise.
	* tree-vrp.c (vrp_finalize): Set ptr that are nonnull.
	(evrp_dom_walker::before_dom_children): Likewise.

gcc/testsuite/ChangeLog:

2016-10-18  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* gcc.dg/torture/pr39074-2.c: Adjust testcase.
	* gcc.dg/torture/pr39074.c: Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@241287 138bc75d-0d04-0410-961f-82ee72b054a4