https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99104
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- Well, at least if split() does not maintain DF then split patterns may not use DF. It's as simple as that ;) Note you need DF analyze anyway since even if present, the DF problem might be out-of-date. Note when you add DF_LIVE you have to remove it manually again if optimize == 1 because there we do not maintain it (but the problem is still not optional). I guess if the x86 backend wants to use DF but other backends do not and do not want to pay the compile-time cost of a df_analyze we could put DF setup into a target hooks hand ... (or a target hook returning the DF problems it likes to have computed for split).
