PR tree-optimization/19633
	* tree-flow.h (struct ptr_info_def): Add field 'pt_null'.
	* tree-ssa-alias.c (init_alias_info): Initialize.
	(merge_pointed_to_info): Set.
	(add_pointed_to_expr): Set pt_null if EXPR is a NULL pointer.
	(dump_points_to_info_for): Show value of pt_null.
	(struct count_ptr_d): Declare.
	(find_ptr_dereference): Remove.
	(ptr_is_dereferenced_by): Remove.
	(count_ptr_derefs): New local function.
	(count_uses_and_derefs): New local function.
	(compute_points_to_and_addr_escape): Call it.  If the number
	of dereferences is greater than zero, mark the pointer as
	dereferenced.  If there are fewer dereferences than uses of
	the pointer, the pointer's value escapes.

testsuite/ChangeLog

	PR tree-optimization/19633
	* testsuite/gcc.dg/pr19633-1.c: New test.
	* testsuite/gcc.dg/pr19633.c: Tweak to make pointer point
	to NULL or a symbol.

From-SVN: r94558