https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88593
--- Comment #4 from Alexander Monakov <amonakov at gcc dot gnu.org> --- It seems to avoid this sort of gotchas cleanup_cfg should gcc_checking_assert (!dom_info_available_p (CDI_DOMINATORS)); gcc_checking_assert (!dom_info_available_p (CDI_POST_DOMINATORS)); but maybe there's a deeper reason it's not done already — I cannot be sure.