[llvm-dev] [GSoC 2016] Introduction & Feedback - Better Alias Analysis

[George Burgess IV via llvm-dev]

> After applying the patch on r267335 and bootstrap LLVM/clang with cfl-aa
enabled on its own as well as behind basic-aa on an x86 machine, I ran
test-suite with lit and saw no failed test cases

Woohoo! This is great news. :D

I'm not sure how closely everyone is reading the intro emails, so we may
get more help if we also send a slightly more targeted "Hey, CFLAA isn't
obviously broken anymore. Please help us find any other problems/please
report performance numbers to us," email. Whether we do that this very
second, or when GSoC actually starts, is up to you.

On Wed, May 11, 2016 at 3:02 PM, Jia Chen via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Dear LLVM community,
>
> I am a GSoC student this year working on the project of improving alias
> analysis in LLVM.
>
> The proposal initially came from a discussion I had with various devs on
> the mailing list some time ago [1]. The general goal of this project is to
> make alias analysis (in particular, cfl-aa) "better", and to be more
> concrete here is a list of objectives I had in mind:
>
> - Evaluating the current state of cfl-aa, and fix all known bugs.
> - Improving the precision of cfl-aa. Although flow sensitivity may not be
> very helpful for LLVM in its current form, field sensitivity should be
> something important and I'll definitely try to add it to cfl-aa. Given the
> complexity LLVM's memory model has, my guess is that I may need to spend
> most of my summer on this task.
> - Improving the performance of cfl-aa. (It is fairly efficient in its
> current form, IMO. Further performance tuning may be needed if more
> features such as field sensitivity were added.)
> - Understanding how various clients interacts with cfl-aa, and exploring
> various ways to minimize precision/performance losses caused by the
> interaction.
> - If time permits, maybe I can look at scev-aa and try to bring it back to
> the compilation pipeline.
>
> I know these objectives are not as clear cut as other GSoC projects people
> used to have, and it is hard to come up with a clear schedule as well as a
> success metric. Nevertheless even if my contributions may seem fragmented
> and incremental, I felt that as long as the work is useful to the
> community, it is going to be the most valuable summer I've ever had as a
> student.
>
> ** Current Status **
>
> I've submitted a simple patch last week (D19776) to fix a subtle bug in
> cfl-aa. After applying the patch on r267335 and bootstrap LLVM/clang with
> cfl-aa enabled on its own as well as behind basic-aa on an x86 machine, I
> ran test-suite with lit and saw no failed test cases. I didn't time the
> tests in any rigorous way, but it didn't look like cfl-aa add very
> noticable performance overhead. It may be a good time, I think, to call for
> people's help to test cfl-aa on their internal codebase. If everything goes
> well, we should be able to safely turn on cfl-aa by default soon.
>
> Let me conclude this introduction by saying thank you for accepting my
> proposal, and in particular I want to thank my mentors George and Hal for
> the providing me with so much support and guidance. Please let me know if
> you have any comments or suggestions.
>
> [1] http://lists.llvm.org/pipermail/llvm-dev/2016-March/096851.html
>
> --
> Best Regards,
>
> --
> Jia Chen
> Department of Computer Science
> University of Texas at Austinjchen at cs.utexas.edu
>
>
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>
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