2017-06-28  Richard Biener  <rguenther@suse.de>

	PR middle-end/81227
	* fold-const.c (negate_expr_p): Use TYPE_UNSIGNED, not
	TYPE_OVERFLOW_WRAPS.
	* match.pd (negate_expr_p): Likewise.
	* tree-ssa-reassoc.c (optimize_range_tests_diff): Use
	fold_build2, not fold_binary.

	* gcc.dg/pr81227.c: New testcase.

From-SVN: r249742