[cfe-dev] [GSoC 2017] Improve loop execution model of the Clang Static Analyzer

[Péter Szécsi via cfe-dev]

Hello,

I would love to work on a Clang Static Analyzer project during the summer
by joining GSoC.
Let me introduce myself:
I'm Peter Szecsi, a third-year BSc student at Eötvös Loránd University,
Budapest. It would be my first Summer of Code project but I have already
contributed to clang:
During the last summer I have uploaded 2 patches:
- An accepted and merged clang-tidy checker [1]
- An accepted Clang SA checker [2]
Since then I am working on cross translational unit analysis as a
university project (and because of that I`ve send some patches about the
ASTImporter [3]). Furthermore I participated in the preparations of a talk
that was accepted at the EuroLLVM conference. [4]
I found SA interesting since I like to work on algorithmic challenges and
enjoy participating in programming competitions and there is a lot of
algorithms in the Static Analyzer which could be optimized/made more
precise by heuristics.

That is the reason why I would be most interested in project "Implement
generalized loop execution modeling" from the Clang SA Open Projects page
[5]. Hopefully it is a suitable project for GSoC and it is possible to
achieve useful improvements during this time frame.
I have read the discussion at the "loop widening" patch [6] and the most
important enhancements (and milestones in the project) would be
invalidating only the possible modified values. In addition to that I was
thinking to have some heuristics which would approximate if a loop is too
complex to even use this kind of strategy because it would still lead to
invalidate most of the values and result in a lot of false positives.
Another small heuristic could be: when we already reached the maximum loop
unroll number then in case we are sure that there is only a few loopsteps
ahead we could unroll it to the end since probably this algorithm will not
consume too much time/memory and the result state will not be much more
complex.

What do you think about these ideas?

(I have CC'd everyone from the "loop widening" patch discussion.)

Best regards,
Peter

[1] https://reviews.llvm.org/D22507
[2] https://reviews.llvm.org/D24246
[3] https://reviews.llvm.org/D29612, https://reviews.llvm.org/D30876,
https://reviews.llvm.org/D30877
[4] http://llvm.org/devmtg/2017-03//2017/02/20/accepted-sessions.html#7
[5] http://clang-analyzer.llvm.org/open_projects.html
[6] https://reviews.llvm.org/D12358
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