match.pd: Fold (~X | C) ^ D into (X | C) ^ (~D ^ C) if (~D ^ C) can be simplified...

match.pd: Fold (~X | C) ^ D into (X | C) ^ (~D ^ C) if (~D ^ C) can be simplified [PR96691]

These simplifications are only simplifications if the (~D ^ C) or (D ^ C)
expressions fold into gimple vals, but in that case they decrease number of
operations by 1.

2021-01-13  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/96691
	* match.pd ((~X | C) ^ D -> (X | C) ^ (~D ^ C),
	(~X & C) ^ D -> (X & C) ^ (D ^ C)): New simplifications if
	(~D ^ C) or (D ^ C) can be simplified.

	* gcc.dg/tree-ssa/pr96691.c: New test.