[Bug debug/90231] ivopts causes <optimized away> iterator in the loop

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90231

--- Comment #17 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Note, for the ignoring of not useful candidates we could during the cand_pref
computation not just check for step being equal, but also if one step is
multiple of the other one or vice versa, of course prefer same step first, then
perhaps the * case where info->iv->step is a constant multiple of
cand->iv->step and finally the division case, perhaps that one with the
requirement that the type of cand->iv->base has then at least ceil_log2
(cand->iv->step) bits larger TYPE_PRECISION.