[LLVMdev] loop fusion in LLVM

[Qi Liao]

Thanks a lot for your input. We will look more into the legality and
profitability checks you've mentioned.

-Qi


On Tue, Nov 12, 2013 at 7:32 PM, Nadav Rotem <nrotem at apple.com> wrote:

> Hi Qi,
>
> No, we don’t have loop fusion.  The loop fusion transformation itself is
> easy, but the profitability and legality checks are challenging.  For
> legality, you would need to analyze the memory that you access and figure
> out that it is legal to fuse the loops. For profitability you would need to
> predict the effect on performance. You would need to predict register
> pressure and resource utilization, which is difficult to do.
>
> Thanks,
> Nadav
>
> On Nov 12, 2013, at 8:39 AM, Qi Liao <qiliao at umich.edu> wrote:
>
> > Hi,
> >
> > I am a student and my team is trying to identify a suitable topic for
> our compiler class final project. The requirement is to implement some
> optimization in LLVM that is not already existed, at least not in the list
> of standard opt that LLVM already has. We are looking at loop fusion as a
> potential candidate topic. Since we are all new to LLVM we would like to
> ask for experts' opinions here if there already is a well known
> implementation of loop fusion pass existed, and if not, is there a
> particular reason that it is not done given such optimization is fairly
> standard?
> >
> > Thank you.
> >
> > -Qi
> > _______________________________________________
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>
>
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