Re: [PATCH, vec-tails] Support loop epilogue vectorization

[Richard Biener <rguenther@suse.de>]

On Thu, 10 Nov 2016, Richard Biener wrote:

> On Tue, 8 Nov 2016, Yuri Rumyantsev wrote:
> 
> > Richard,
> > 
> > Here is updated 3 patch.
> > 
> > I checked that all new tests related to epilogue vectorization passed with it.
> > 
> > Your comments will be appreciated.
> 
> A lot better now.  Instead of the ->aux dance I now prefer to
> pass the original loops loop_vinfo to vect_analyze_loop as
> optional argument (if non-NULL we analyze the epilogue of that 
> loop_vinfo).  OTOH I remember we mainly use it to get at the
> original vectorization factor?  So we can pass down an (optional)
> forced vectorization factor as well?

Btw, I wonder if you can produce a single patch containing just
epilogue vectorization, that is combine patches 1-3 but rip out
changes only needed by later patches?

Thanks,
Richard.

> Richard.
> 
> > 2016-11-08 15:38 GMT+03:00 Richard Biener <rguenther@suse.de>:
> > > On Thu, 3 Nov 2016, Yuri Rumyantsev wrote:
> > >
> > >> Hi Richard,
> > >>
> > >> I did not understand your last remark:
> > >>
> > >> > That is, here (and avoid the FOR_EACH_LOOP change):
> > >> >
> > >> > @@ -580,12 +586,21 @@ vectorize_loops (void)
> > >> >           && dump_enabled_p ())
> > >> >           dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, vect_location,
> > >> >                            "loop vectorized\n");
> > >> > -       vect_transform_loop (loop_vinfo);
> > >> > +       new_loop = vect_transform_loop (loop_vinfo);
> > >> >         num_vectorized_loops++;
> > >> >        /* Now that the loop has been vectorized, allow it to be unrolled
> > >> >           etc.  */
> > >> >      loop->force_vectorize = false;
> > >> >
> > >> > +       /* Add new loop to a processing queue.  To make it easier
> > >> > +          to match loop and its epilogue vectorization in dumps
> > >> > +          put new loop as the next loop to process.  */
> > >> > +       if (new_loop)
> > >> > +         {
> > >> > +           loops.safe_insert (i + 1, new_loop->num);
> > >> > +           vect_loops_num = number_of_loops (cfun);
> > >> > +         }
> > >> >
> > >> > simply dispatch to a vectorize_epilogue (loop_vinfo, new_loop)
> > >> f> unction which will set up stuff properly (and also perform
> > >> > the if-conversion of the epilogue there).
> > >> >
> > >> > That said, if we can get in non-masked epilogue vectorization
> > >> > separately that would be great.
> > >>
> > >> Could you please clarify your proposal.
> > >
> > > When a loop was vectorized set things up to immediately vectorize
> > > its epilogue, avoiding changing the loop iteration and avoiding
> > > the re-use of ->aux.
> > >
> > > Richard.
> > >
> > >> Thanks.
> > >> Yuri.
> > >>
> > >> 2016-11-02 15:27 GMT+03:00 Richard Biener <rguenther@suse.de>:
> > >> > On Tue, 1 Nov 2016, Yuri Rumyantsev wrote:
> > >> >
> > >> >> Hi All,
> > >> >>
> > >> >> I re-send all patches sent by Ilya earlier for review which support
> > >> >> vectorization of loop epilogues and loops with low trip count. We
> > >> >> assume that the only patch - vec-tails-07-combine-tail.patch - was not
> > >> >> approved by Jeff.
> > >> >>
> > >> >> I did re-base of all patches and performed bootstrapping and
> > >> >> regression testing that did not show any new failures. Also all
> > >> >> changes related to new vect_do_peeling algorithm have been changed
> > >> >> accordingly.
> > >> >>
> > >> >> Is it OK for trunk?
> > >> >
> > >> > I would have prefered that the series up to -03-nomask-tails would
> > >> > _only_ contain epilogue loop vectorization changes but unfortunately
> > >> > the patchset is oddly separated.
> > >> >
> > >> > I have a comment on that part nevertheless:
> > >> >
> > >> > @@ -1608,7 +1614,10 @@ vect_enhance_data_refs_alignment (loop_vec_info
> > >> > loop_vinfo)
> > >> >    /* Check if we can possibly peel the loop.  */
> > >> >    if (!vect_can_advance_ivs_p (loop_vinfo)
> > >> >        || !slpeel_can_duplicate_loop_p (loop, single_exit (loop))
> > >> > -      || loop->inner)
> > >> > +      || loop->inner
> > >> > +      /* Required peeling was performed in prologue and
> > >> > +        is not required for epilogue.  */
> > >> > +      || LOOP_VINFO_EPILOGUE_P (loop_vinfo))
> > >> >      do_peeling = false;
> > >> >
> > >> >    if (do_peeling
> > >> > @@ -1888,7 +1897,10 @@ vect_enhance_data_refs_alignment (loop_vec_info
> > >> > loop_vinfo)
> > >> >
> > >> >    do_versioning =
> > >> >         optimize_loop_nest_for_speed_p (loop)
> > >> > -       && (!loop->inner); /* FORNOW */
> > >> > +       && (!loop->inner) /* FORNOW */
> > >> > +        /* Required versioning was performed for the
> > >> > +          original loop and is not required for epilogue.  */
> > >> > +       && !LOOP_VINFO_EPILOGUE_P (loop_vinfo);
> > >> >
> > >> >    if (do_versioning)
> > >> >      {
> > >> >
> > >> > please do that check in the single caller of this function.
> > >> >
> > >> > Otherwise I still dislike the new ->aux use and I believe that simply
> > >> > passing down info from the processed parent would be _much_ cleaner.
> > >> > That is, here (and avoid the FOR_EACH_LOOP change):
> > >> >
> > >> > @@ -580,12 +586,21 @@ vectorize_loops (void)
> > >> >             && dump_enabled_p ())
> > >> >            dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, vect_location,
> > >> >                             "loop vectorized\n");
> > >> > -       vect_transform_loop (loop_vinfo);
> > >> > +       new_loop = vect_transform_loop (loop_vinfo);
> > >> >         num_vectorized_loops++;
> > >> >         /* Now that the loop has been vectorized, allow it to be unrolled
> > >> >            etc.  */
> > >> >         loop->force_vectorize = false;
> > >> >
> > >> > +       /* Add new loop to a processing queue.  To make it easier
> > >> > +          to match loop and its epilogue vectorization in dumps
> > >> > +          put new loop as the next loop to process.  */
> > >> > +       if (new_loop)
> > >> > +         {
> > >> > +           loops.safe_insert (i + 1, new_loop->num);
> > >> > +           vect_loops_num = number_of_loops (cfun);
> > >> > +         }
> > >> >
> > >> > simply dispatch to a vectorize_epilogue (loop_vinfo, new_loop)
> > >> > function which will set up stuff properly (and also perform
> > >> > the if-conversion of the epilogue there).
> > >> >
> > >> > That said, if we can get in non-masked epilogue vectorization
> > >> > separately that would be great.
> > >> >
> > >> > I'm still torn about all the rest of the stuff and question its
> > >> > usability (esp. merging the epilogue with the main vector loop).
> > >> > But it has already been approved ... oh well.
> > >> >
> > >> > Thanks,
> > >> > Richard.
> > >>
> > >>
> > >
> > > --
> > > Richard Biener <rguenther@suse.de>
> > > SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)
> > 
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)