https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108688
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Andrew Pinski from comment #5) > Oh I might have a fix for this already just didn't have a testcase for the > upstream compiler at the time. Note, it is just the first case from the above because @0 already ought to be guaranteed to have mode precision because BIT_INSERT_EXPR requires it too. On the other side, we should for the first case differentiate between @1 has mode precision, then we can do what we do right now, or when isize == rsize and rpos == ipos (then we can just simplify to possibly casted @1) and finally otherwise, IMHO we should just punt.
