2017-04-04  Richard Biener  <rguenther@suse.de>

	PR middle-end/80281
	* match.pd (A + (-B) -> A - B): Make sure to preserve unsigned
	arithmetic done for the negate or the plus.  Simplify.
	(A - (-B) -> A + B): Likewise.
	* fold-const.c (split_tree): Make sure to not negate pointers.

	* gcc.dg/torture/pr80281.c: New testcase.

From-SVN: r246674