On Mon, 17 Jun 2019, Kewen.Lin wrote: > on 2019/6/17 下午8:08, Richard Biener wrote: > > On June 17, 2019 11:59:30 AM GMT+02:00, Segher Boessenkool > > <seg...@kernel.crashing.org> wrote: > >> On Mon, Jun 17, 2019 at 10:51:49AM +0200, Richard Biener wrote: > >>> On Mon, 17 Jun 2019, Kewen.Lin wrote: > >>> > >>>> Hi Segher and Bill, > >>>> > >>>> Thanks a lot for your review comments! I've updated the patch > >> accordingly. > >>>> > >>>> The updated one attached. > >>> > >>> OK. I suppose all low-overhead loop instructions use a decrement to > >> zero > >>> style iterator? > >> > >> The documentation says decrement to 0, decrement to -1, and decrement > >> to > >> any negative are all supported. But all are decrement, yes. > > > > Hmm, so I wonder if we should tell IVOPTS the kind because the IV generated > > has to match RTL doloops expectations? Thus return an enum value from the > > hook? > > > > I guess we don't need to make it in IVOPTs, since doloop_optimize can > transform the loop closing to > its expected pattern once it gets the iteration count, with target hook > doloop_end. > It's to modify the original closing into: > niter -> 0 > niter-1 -> -1 > niter-n -> -n
True, but this IV may affect other IVs choice (well, at least if it is "cheap" to use the doloop IV in derived IVs which it is not for power). Richard.
