https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59967
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> --- In the size estimation we have BB: 46, after_exit: 0 size: 1 _319 = MEM[(double *)c0_188(D) + 16B]; size: 1 _321 = i_171 >> 2; Constant expression will be folded away. size: 2 if (_321 != 0) so somehow we fail to see that the conditional is constant after peeling. Reworking things so we can use a lattice (also avoid calling simple_iv too many times) will improve that (but also the code doesn't then only consider MAX (taken-paths-lengths) in case there is an else block). It looks like reworking this to do a domwalk may be profitable. The simplistic approach gets us from an estimated size after unrolling of to 238 (still that won't unroll the loop). I think we should also consider size->eliminated_by_peeling in the call heuristic - the call itself might be a minor distraction and especially eliminated branches might result in a good speed benefit. That said, the core algorithm for likely-eliminated should be improved, but it won't help by itself.
