Fix PR66178, ICE due to misexpansion of constant expressions involving labels.

Fix PR66178, ICE due to misexpansion of constant expressions involving labels.

	PR middle-end/66178
	* expr.c (expand_expr_real_2) [PLUS_EXPR, MINUS_EXPR]: Don't
	drop EXPAND_INITIALIZER.
	* rtl.h (contains_symbolic_reference_p): Declare.
	* rtlanal.c (contains_symbolic_reference_p): New function.
	* simplify-rtx.c (simplify_binary_operation_1): Don't turn
	a subtraction into a NOT if symbolic constants are involved.

testsuite/
	PR middle-end/66178
	gcc.dg/torture/pr66178.c: New test.

From-SVN: r232689