[llvm-dev] [GSoC 2016] Polly as an Analysis pass - Midterm report

[Tobias Grosser via llvm-dev]

On 06/20/2016 02:00 PM, Utpal Bora wrote:
> Dear Community,
> 
> 
> I would like to summarize my work till date for GSoC 2016.

Hi Utpal,

thank you for this update.

> Till the current phase of my project, I have mostly focused on
> developing the necessary infrastructure to use analysis results from
> Polly in LLVM.
> 
> 
> Initial plan as mentioned in the proposal:
> 
> For the first month:-
> 
>  1.
> 
>     Decouple ScopInfo pass from Polly’s pass chain and provide
>     capability to create SCoP(Static Control Parts) objects from
>     arbitrary SESE regions.
> 
>  2.
> 
>     Implement new passes ScopInfoWrapperPass and
>     DependenceInfoWrapperPass as Function Passes.
> 
>  3.
> 
>     Provide an interface to Polly’s dependence analysis which can be
>     directly queried from LLVM transformation passes such as Loop
>     Vectorizer.

This seems to have been gone very nicely. I see that some of the patches
are still in the review process. Could you elaborate on their status and
what is still needed to get them committed.


> For the next phase:-
> 
>  4.
> 
>     Cache the dependences computed by Polly for a given SCoP and provide
>     methods to invalidate the analysis results when the SCoP changes.
> 
>  5.
> 
>     Demonstrate the power and usefulness of the interface by integrating
>     it with Loop Vectorizer or other clients, for example, client that
>     requires loop trip count, etc.
> 
> 
> Current Status:
> 
>  1.
> 
>     Decoupling SCoP object creation from pass logic is complete and has
>     been addressed under D20770 <http://reviews.llvm.org/D20770>, D20831
>     <http://reviews.llvm.org/D20831>and D20912
>     <http://reviews.llvm.org/D20912>review items. Patches have been
>     accepted and committed.
> 
>  2.
> 
>     Implemented two new function passes in Polly namely
>     ScopInfoWrapperPass (D20962 <http://reviews.llvm.org/D20962>) and
>     DependenceInfoWrapperPass (D21105 <http://reviews.llvm.org/D21105>).
>     These are required to bypass the RegionPassManager.
> 
>      1.
> 
>         ScopInfoWrapperPass addresses creating SCoP objects for the
>         whole function.
> 
>      2.
> 
>         DependenceInfoWrapperPass addresses constructing polyhedral
>         dependences for all the SCoP objects of a function.
> 
>  3.
> 
>     These patches are currently under review and I am incorporating
>     changes as suggested by the Polly community.
> 
>  4.
> 
>     Implemented first version of an interface to Polly's analysis
>     passes- PolyhedralInfo pass (D21486
>     <http://reviews.llvm.org/D21486>). Implemented isParallel(Loop *)
>     interface to check parallelism of a loop.
> 
> 
> Pending Work:
> 
>  1.
> 
>     Complete the interface - PolyhederalInfo pass. Currently I am
>     working on providing more interfaces to check whether a loop is
>     vectorizable or not and to get loop trip count.
> 
>       *
> 
>         isVectorizable(Loop *L, *MinDepDistance)
> 
>       *
> 
>         getLoopTripCount(Loop *)
> 
>  2.
> 
>     Work on caching Polly's analysis results properly and provide
>     methods to invalidate the analysis results when the SCoP changes.
> 
>  3.
> 
>     Demonstrate the power and usefulness of the interface by integrating
>     it with Loop Vectorizer.
> 
> 
> Below are the list of patches I sent  during this period:-
> 
> D20770 <http://reviews.llvm.org/D20770>, D20831
> <http://reviews.llvm.org/D20831>, D20912
> <http://reviews.llvm.org/D20912>, D20962
> <http://reviews.llvm.org/D20962>, D21105
> <http://reviews.llvm.org/D21105>, D21486 <http://reviews.llvm.org/D21486>
> 
> 
> I thank Johannes, Tobias, Michael, Ether and others for all the
> support/feedback/advises. Especially, Johannes for the time spent in
> hangouts, which we have been having two times a week.

Very nice, indeed and thanks Johannes for taking the time for such close
mentoring. To make sure we are all up-to-date it would be great if you
could send brief meeting notes that summarize your hangout discussions.

Best,
Tobias