* fold-const.c (fold) <BIT_IOR_EXPR>: Optimize ~X|X and X|~X as -1.
	<BIT_XOR_EXPR>: Optimize ~X|X and X|~X as -1.
	<BIT_AND_EXPR>: Optimize ~X&X and X&~X as 0.
	<TRUTH_AND_EXPR, TRUTH_ANDIF_EXPR>: Optimize !X&&X and X&&!X as false.
        <TRUTH_OR_EXPR, TRUTH_ORIF_EXPR>: Optimize !X||X and !X||X as true.
	<TRUTH_XOR_EXPR>: Optimize !X^X and X^X! as true.  Now that
	TRUTH_XOR_EXPR is a commutative tree code, don't test whether arg0
	is a constant.

	* gcc.dg/20040527-1.c: New test case.

From-SVN: r83733