Re: [PING] [PATCH] Optional alternative base_expr in finding basis for CAND_REFs

[Jeff Law <law at redhat dot com>]

On 12/02/13 08:47, Yufeng Zhang wrote:
> Ping~
>
> http://gcc.gnu.org/ml/gcc-patches/2013-11/msg03360.html

> Thanks,
> Yufeng
>
> On 11/26/13 15:02, Yufeng Zhang wrote:
> > On 11/26/13 12:45, Richard Biener wrote:
> > > On Thu, Nov 14, 2013 at 12:25 AM, Yufeng
> > > Zhang<Yufeng.Zhang@arm.com>   wrote:
> > > > On 11/13/13 20:54, Bill Schmidt wrote:
> > > > > The second version of your original patch is ok with me with the
> > > > > following changes.  Sorry for the little side adventure into the
> > > > > next-interp logic; in the end that's going to hurt more than it
> > > > > helps in
> > > > > this case.  Thanks for having a look at it, anyway.  Thanks also for
> > > > > cleaning up this version to be less intrusive to common interfaces; I
> > > > > appreciate it.
> > > >
> > > >
> > > > Thanks a lot for the review.  I've attached an updated patch with the
> > > > suggested changes incorporated.
> > > >
> > > > For the next-interp adventure, I was quite happy to do the
> > > > experiment; it's
> > > > a good chance of gaining insight into the pass.  Many thanks for
> > > > your prompt
> > > > replies and patience in guiding!
> > > >
> > > >
> > > > > Everything else looks OK to me.  Please ask Richard for final
> > > > > approval,
> > > > > as I'm not a maintainer.
First a note, I need to check on voting for Bill as the slsr maintainer 
from the steering committee.   Voting was in progress just before the 
close of stage1 development so I haven't tallied the results :-)

> > Yes, you are right about the non-trivial 'base' tree are rarely shared.
> >    The cached is introduced mainly because get_alternative_base () may be
> > called twice on the same 'base' tree, once in the
> > find_basis_for_candidate () for look-up and the other time in
> > alloc_cand_and_find_basis () for record_potential_basis ().  I'm happy
> > to leave out the cache if you think the benefit is trivial.
Without some sense of how expensive the lookups are vs how often the 
cache hits it's awful hard to know if the cache is worth it.

I'd say take it out unless you have some sense it's really saving time. 
 It's a pretty minor implementation detail either way.


> > > +/* { dg-do compile } */
> > > +/* { dg-options "-O2 -fdump-tree-slsr" } */
> > > +
> > > +typedef int arr_2[50][50];
> > > +
> > > +void foo (arr_2 a2, int v1)
> > > +{
> > > +  int i, j;
> > > +
> > > +  i = v1 + 5;
> > > +  j = i;
> > > +  a2 [i-10] [j] = 2;
> > > +  a2 [i] [j++] = i;
> > > +  a2 [i+20] [j++] = i;
> > > +  a2 [i-3] [i-1] += 1;
> > > +  return;
> > > +}
> > > +
> > > +/* { dg-final { scan-tree-dump-times "MEM" 5 "slsr" } } */
> > > +/* { dg-final { cleanup-tree-dump "slsr" } } */
> > >
> > > scanning for 5 MEMs looks non-sensical.  What transform do
> > > you expect?  I see other slsr testcases do similar non-sensical
> > > checking which is bad, too.
> >
> > As the slsr optimizes CAND_REF candidates by simply lowering them to
> > MEM_REF from e.g. ARRAY_REF, I think scanning for the number of MEM_REFs
> > is an effective check.  Alternatively, I can add a follow-up patch to
> > add some dumping facility in replace_ref () to print out the replacing
> > actions when -fdump-tree-slsr-details is on.
I think adding some details to the dump and scanning for them would be 
better.  That's the only change that is required for this to move forward.

I suggest doing it quickly.  We're well past stage1 close at this point.

jeff