[llvm-dev] CFLAA

[David Callahan via llvm-dev]

Hi Jia, nice to meet you,


On 8/25/16, 6:22 PM, "Jia Chen" <jchen at cs.utexas.edu> wrote:

>Hi David,
>
>I am the one who's responsible for CFLAA's refactoring in the summer.
>I've sent out another email on llvm-dev, and you can find more about my
>work in my GSoC final report.

Is this report available?

>I think it is fantastic that you have done such an interesting work.
>I'll definitely try to help getting the code reviewed and merged in the
>current. After a quick glance at your patch, it seems that what you are
>trying to do there is an optimized version of CFL-Steens, with a custom
>way of handling context-sensitivity. I'll be happy if we can end up
>integrating it into the existing CFL-Steens pass

The work was more about improving the accuracy of the equivalencing step
then it 
is about context sensitivity. In fact, it is only context-sensitive to the
extent there is simulated inlining. There is now downward propagation of
facts into called functions.

I wanted to share it incase there were lessons of value. It is not in a
very
clean state at the moment but I can clean it up. Let me know how I can
help.


>Regarding the benchmark numbers, I'm very interested in what kind of
>tests files were you running the experiments on? Is it possible to share
>it?
>
>> On Wed, Aug 24, 2016 at 2:56 PM, David Callahan <dcallahan at fb.com>
>>wrote:
>> Hi Greg,
>>
>>
>>
>> I see there is on going work with alias analysis and it appears the
>>prior CFLAA has been abandoned.
>>
>>
>>
>> I have a variant of it where I reworked how compression was done to be
>>less conservative, reworked the interprocedural to do simulated but
>>bounded inlining, and added code to do on-demand testing of CFL paths on
>>both compressed and full graphs.
>>
>>
>>
>> I reached a point where the ahead-of-time compression was linear but
>>still very accurate compared to on-demand path search and there were
>>noticeable improvements in the alias analysis results and impacted
>>transformations.  Happy to share the patch with you if you are
>>interested as well as some data collected.
>>
>>
>>
>> However I was not able to see any performance improvements in the code.
>>In fact on a various benchmarks there were noticeable regressions in
>>measured performance of the generated code. Have you noticed any similar
>>problems?
>>
>>
>>
>> --david
>
>
>
>-- 
>Best Regards,
>
>--
>Jia Chen