https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95663
--- Comment #18 from Jeffrey A. Law <law at redhat dot com> --- Jon, there's no way for the optimizers to improve the to_derived_bad case as there's nothing in the IL after we leave the front-end that's useful. In the .original dump we have: ;; Function derived& to_derived_bad(base2*) (null) ;; enabled by -tree-original return <retval> = b != 0B ? (struct derived &) b + 18446744073709551612 : 0; There's just nothing the optimizers can do with that. The front-end would have to provide more information or remove the check itself (as is done for the to_derived_good case which has this .original dump): ;; Function derived& to_derived_good(base2*) (null) ;; enabled by -tree-original return <retval> = (struct derived &) NON_LVALUE_EXPR <b> + 18446744073709551612;
