fn should_use_fp_conv_helper<'a, Ty, C>(
    cx: &C,
    arg_layout: &TyAndLayout<'a, Ty>,
    xlen: u64,
    flen: u64,
    field1_kind: &mut RegPassKind,
    field2_kind: &mut RegPassKind
) -> Result<(), CannotUseFpConv>
where Ty: TyAbiInterface<'a, C> + Copy,