https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102906
--- Comment #17 from rguenther at suse dot de <rguenther at suse dot de> --- On Wed, 10 Nov 2021, aldyh at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102906 > > --- Comment #16 from Aldy Hernandez <aldyh at gcc dot gnu.org> --- > (In reply to rguent...@suse.de from comment #15) > > On Wed, 10 Nov 2021, aldyh at gcc dot gnu.org wrote: > > > > @@ -60,6 +63,24 @@ should_duplicate_loop_header_p (basic_block header, > > > class > > > loop *loop, > > > if (optimize_loop_for_size_p (loop) > > > && !loop->force_vectorize) > > > { > > > + if (gcond *last = safe_dyn_cast <gcond *> (last_stmt (header))) > > > + { > > > + gimple_ranger ranger; > > > + int_range<2> r; > > > + path_range_query path (ranger, /*resolve=*/true); > > > + auto_vec<basic_block> bbs (2); > > > + edge e = loop_preheader_edge (loop); > > > + > > > + gcc_checking_assert (e->dest == header); > > > + bbs.quick_push (header); > > > + bbs.quick_push (e->src); > > > + bitmap imports = ranger.gori ().imports (header); > > > + path.compute_ranges (bbs, imports); > > > + path.range_of_stmt (r, last); > > > + r.dump (); > > > + fputc ('\n', stderr); > > > > Nice. Does composing the path from the exact two BBs mean that > > it won't pick up a case like > > > > if (n > 0) > > if (k > 0) > > for (; n > 0;) > > ... > > > > where the n > 0 outer condition is on the predecessor from > > e->src? Or is the path merely built to denote the fact > > that we're interested on the entry edge of the loop only > > (on the backedge the condition wouldn't be known)? > > If the predecessor for e->src dominates it, it will also pick that up. The > path merely denotes the blocks we care about for intra-block ranges / > relationals, etc. With resolve=true (above), any range or relation not known > within the path we will just pick up the range on entry to the path by asking > ranger. > > Does that answer your question? Yes. I guess it would be nice to have a CTOR or so for the case where the path is really a single edge like in this case. > For the record, I also agree that we should pull out these loop rotations, > peels, etc from the threaders into the loop optimizers, as they have a better > model to make decisions about loops. Indeed.
