This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH] Add vector cost model density heuristic
On Tue, 2012-06-19 at 16:20 +0200, Richard Guenther wrote:
> On Tue, 19 Jun 2012, William J. Schmidt wrote:
>
> > On Tue, 2012-06-19 at 14:48 +0200, Richard Guenther wrote:
> > > On Tue, 19 Jun 2012, William J. Schmidt wrote:
> > >
> > > > I remember having this discussion, and I was looking for it to check on
> > > > the details, but I can't seem to find it either in my inbox or in the
> > > > archives. Can you please point me to that again? Sorry for the bother.
> > >
> > > It was in the "Correct cost model for strided loads" thread.
> >
> > Ah, right, thanks. I think it will be best to make that a separate
> > patch in the series. Like so:
> >
> > (1) Add calls to the new interface without disturbing existing logic;
> > modify the profitability algorithms to query the new model for inside
> > costs. Default algorithm for the model is to just sum costs as is done
> > today.
Just FYI, this is not quite as straightforward as I thought. There is
some code in tree-vect-data-refs.c that computes costs for various
peeling options and picks one of them. In most other places we can just
pass the instructions to the back end at the same place that the costs
are currently calculated, but not here. This will require some more
major surgery to save the instructions needed from each peeling option
and only pass along the ones that end up being chosen.
The upside is the same sort of "delayed emit" is needed for the SLP
ordering problem, so the infrastructure for this will be reusable for
that problem.
Grumble.
Bill
> > (1a) Split up the cost hooks (one for loads/stores with misalign parm,
> > one for vector_stmt with tree_code, etc.).
> > (x) Add heuristics to target models as desired.
> > (2) Handle the SLP ordering problem.
> > (3) Handle outside costs in the target model.
> > (4) Remove the now unnecessary cost fields and the calls that set them.
> >
> > I'll start work on this series of patches as I have time between other
> > projects.
>
> Thanks!
> Richard.
>