http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53316
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-05-11 08:52:51 UTC --- A big question for -Odebug is e.g. if we should enable var-tracking for it or not. While it is time consuming, it should improve the debug experience, there are various cases where -O -g is actually better debuggable than -O0 -g which doesn't do var-tracking, e.g. with register vars, or VLAs, or during prologues/epilogues.