https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108601
--- Comment #12 from Hongtao.liu <crazylht at gmail dot com> ---
> When the VF is not known we usually do not require an epilogue? If
> we don't require one we should avoid creating one.
I may not be very clear in my description， here gdb shows.
(gdb) p vf
$1 = {<poly_int_pod<2, unsigned long>> = {coeffs = {4, 4}}, <No data fields>}
(gdb) p vf.is_constant ()
$2 = false
(gdb)
