On Wed, Dec 1, 2021 at 2:36 PM Richard Biener <richard.guent...@gmail.com> wrote: > > On Tue, Nov 30, 2021 at 4:48 PM Aldy Hernandez via Gcc-patches > <gcc-patches@gcc.gnu.org> wrote: > > > > We are currently restricting loop crossing paths in the generic copier > > used by the back threader, but we should be able to handle them after > > loop_done has completed. > > But this isn't a cost thing but a correctness (as in, can we update > loops properly) > thing. We are passing 'loop' down to copy_bbs and very much rely on > seeing either BBs of that loop or copying complete subloops of it. > > You will likely see excess loop fixup caused by this or ICEs in case the > caller of this function will not always set LOOPS_NEED_FIXUP > (not that copy_bbs handling of loops is perfect).
Ughh, fair enough. In which case at least I've commented in the PR what the problem is here. Perhaps we could benefit from a BB copier that could handle loops, which is way above my circle of competence ;-). Aldy
