[LLVMdev] Google Summer of Code Idea

Richard Warburton richard.warburton at gmail.com
Mon Mar 3 02:55:12 PST 2008

>  No
>  I've got a BDD based version of andersen's around already (uncommitted).
>  It's slower in time (by a factor of 8 or so), but very slightly (1-2
>  megabytes of memory) more memory efficient on some cases. Nowadays,
>  the bitmap version is actually more memory efficient than the BDD
>  version, even if you turn off BDD caching, etc.
>  The thing you have to understand is that these context sensitive BDD
>  algorithms work okay on java, but fall down pretty badly on C/C++,
>  because it is a much bigger problem.   Whaley's is just brute force,
>  and Zhu's is pretty darn complex.

I was interested to see whether Whaley's algorithm really works
particularly, given its simplicity and the claims made in the papers.

>  Both are amenable to the same style of offline variable optimizations
>  that Hardekopf, et al (Ben and a friend have been helping out with
>  implementation of andersen's in LLVM), and that may actually make them
>  usable for real world programs.

Are you referring to both the PLDI and the SAS papers?

>  >  4. Is anyone willing to mentor this project?
>  I would.

Thanks ;)

>  I think you will be surprised how badly these algorithms work on even
>  moderate sized C++ programs :(

I'm slightly confused here as to whether you mean in terms of
precision of analysis, or compute time taken by running the algorithm.


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