Re: complete_unrolli / complete_unroll

[Richard Guenther <richard.guenther@gmail.com>]

On Tue, Sep 29, 2009 at 8:23 PM, David Edelsohn <dje.gcc@gmail.com> wrote:
> On Thu, Aug 20, 2009 at 4:48 AM, Richard Guenther
> <richard.guenther@gmail.com> wrote:
>
>> Can't we use graphite to re-roll loops?  That is, compress the
>> polyhedron by introducing a new parameter?  But maybe I am
>> not good at guessing what your initial bloat issue looks like.
>>
>> The reason I'm asking is that there is enough code out in the
>> wild that has loops with manually unrolled bodies - I have seen
>> up to 16 times here.
>
> Do we want to try to address this partially in GCC 4.5?  Providing
> some way to disable early unrolling either explicitly or implicitly
> when Graphite is enabled?
>
> Early unrolling can cause two problems:
>
> 1) Increase the size of SCoPs, which increases memory consumption and
> analysis time.
>
> 2) Confusing SCoP analysis.
>
> Separate from re-rolling and other long-term solutions, it would be
> helpful for Graphite if there was some explicit control over early
> unrolling to help with experimentation.

I can definitely look into that - can someone open a bugreport
and assign it to me please?

Thanks,
RIchard.

> Thanks, David
>