PR optimization/12260
	* simplify-rtx.c (simplify_unary_operation): Simplify all unary
	operations through CONST nodes.  Optimize (neg (plus X C)) as
	(minus -C X) for constant values C.
	(simplify_binary_operation): Optimize (minus (neg X) C) as
	(minus -C X) for constant values C.
	(simplify_plus_minus): Avoid creating (neg (const (plus X C)),
	instead create (minus -C X).

	* gcc.c-torture/compile/20031011-2.c: New test case.

From-SVN: r72379