https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87663
--- Comment #1 from Lukas Mosimann <lumosimann at gmail dot com> ---
By the way: I could drop parameter `Z` from `C` and `D`. I forgot to remove
that when I was experimenting with extensions like `f_n = f_{n-1} + f_{n-2} +
f_{n-3}`.
