2015-10-28  Richard Biener  <rguenther@suse.de>

	PR middle-end/68067
	* fold-const.c (negate_expr_p): We cannot negate plus or minus
	if overflow is not wrapping.  Likewise multiplication unless
	one operand is constant and not power of two.
	(fold_negate_expr): Adjust accordingly.

	* gcc.dg/torture/pr68067-1.c: New testcase.
	* gcc.dg/torture/pr68067-2.c: Likewise.

From-SVN: r229479