[llvm-dev] soundness and precision of LazyValueInfo and ValueTracking

[Hal Finkel via llvm-dev]

----- Original Message -----
> From: "John Regehr via llvm-dev" <llvm-dev at lists.llvm.org>
> To: llvm-dev at lists.llvm.org
> Sent: Wednesday, April 20, 2016 7:21:56 AM
> Subject: [llvm-dev] soundness and precision of LazyValueInfo and	ValueTracking
> 
> I've been testing LVI and getKnownBits() using this little custom
> pass:
> 
>    https://github.com/regehr/llvm-test-lvi
> 
> It rewrites the code to dynamically check that compile-time dataflow
> facts are sound. So far it hasn't turned up any errors, for example
> in
> SPEC CPU 2006.
> 
> On the other hand, its debugging output has found some pretty obvious
> room for improvement in the precision of LVI:
> 
>    https://llvm.org/bugs/show_bug.cgi?id=27433
>    https://llvm.org/bugs/show_bug.cgi?id=27434
> 
> See also this earlier one:
> 
>    https://llvm.org/bugs/show_bug.cgi?id=27296
> 
> Would it make sense to make to add some code for printing the results
> of
> LVI and ValueTracking so that we can test for precision regressions?

I think it makes sense for these to be independently testable.

 -Hal
 
> John
> 
> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory