re PR c++/78655 (gcc doesn't exploit the fact that the result of pointer addition can not be nullptr)

2018-08-20  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/78655
	* tree-vrp.c (extract_range_from_binary_expr_1): Make
	pointer + offset nonnull if either operand is nonnull work.

	* gcc.dg/tree-ssa/evrp11.c: New testcase.

From-SVN: r263662