middle-end/115641 - invalid address construction

middle-end/115641 - invalid address construction

fold_truth_andor_1 via make_bit_field_ref builds an address of
a CALL_EXPR which isn't valid GENERIC and later causes an ICE.
The following simply avoids the folding for f ().a != 1 || f ().b != 2
as it is a premature optimization anyway.  The alternative would
have been to build a TARGET_EXPR around the call.  To get this far
f () has to be const as otherwise the two calls are not semantically
equivalent for the optimization.

	PR middle-end/115641
	* fold-const.cc (decode_field_reference): If the inner
	reference isn't something we can take the address of, fail.

	* gcc.dg/torture/pr115641.c: New testcase.