re PR middle-end/30322 (((-i-1) + i) +1) is turned into ~i + (i+1) and never into 0 on the tree level)


	PR middle-end/30322
	* fold-const.c (fold_binary): Fold X + ~X and ~X + X into -1 when
	we don't care about trapping overflow.  Only convert -A - 1 into ~A
	when we don't care about trapping overflow.

	* gcc.dg/fold-plusnot-1.c: New test case.

From-SVN: r120300