[LLVMdev] Contribute a new precise pointer analysis to LLVM

[lian li]

Hi Hal,

Thanks for your interest.

We tested with the following existing compiler optimizations in LLVM
with SPECINT2006 benchmarks:
-dse (dead store elimination),
-gvn (global value numbering),
-licm (loop invariant code motion),
-bb-vectorize (basic block vectorization),
-memcpyopt (memcpy optimization),
-sink (code sinking),
-loop-idom (recognize loop idioms),
-argpromotion (argument promotion).

As far as I know, this list includes all optmizations in LLVM that
requires alias information. With our pointer analysis, for the three
optimizations "-dse, -gvn, -licm", we have observed significant
improvements in terms of the number of optimizations being conducted.
Take licm as an example, with our analysis, the number of instructions
being hoisted out of loops more than doubled for some benchmarks. We
have not seen big changes in terms of runtime performance though.

We measure compile time by first linking all modules of the same
benchmark together, then running the analysis against the linked
module. It finishes in less than 1 minute over applications such as
httpd and sendmail, both with more than 100,000 LOC. For some
benchmarks, it is time-consuming: the analysis time for GCC is close
to 45 minutes.  But if you run the analysis over individual files (as
in your normal compilation process), there is no observable overhead
in terms of compile time.

Regards,
Lian



On Fri, Oct 18, 2013 at 12:15 PM, Hal Finkel <hfinkel at anl.gov> wrote:
> Hi Lian,
>
> I am certainly interested in seeing this; do you have performance numbers (compile time)? Also, can you share more information about the promising optimization results you mentioned?
>
> Thanks,
> Hal
>
> ----- Original Message -----
>> Hi All,
>>
>> This is Lian Li  from Oracle Labs in Brisbane Australia.
>>
>> We have developed a precise and highly efficient pointer analysis
>> framework on top of LLVM,  The approach is flow, context, and field
>> sensitive, details are described in the two papers below:
>>
>> "Boosting the performance of flow-sensitive points-to analysis using
>> value flow" (in ESEC-FSE 2011), and
>> "Precise and scalable context-sensitive pointer analysis via value
>> flow graph" (in ISMM 2013).
>>
>> The analysis was initially developed for the purpose of bug checking,
>> and is now extended to support compiler optimizations. We have tested
>> it with existing compiler optimizations in LLVM, and have seen
>> promising results.
>>
>> We are now considering to make this analysis available to the LLVM
>> community, and contribute resources for future maintenance needs,
>> provided that there is enough interest. We think that a new precise
>> pointer analysis in LLVM can enable more new optimization and
>> analysis
>> techniques to be developed in LLVM.
>>
>> Any people interested in seeing a new precise pointer analysis in
>> LLVM?
>>
>> Regards,
>> Lian Li
>>
>>
>>
>>
>>
>>
>>
>> --
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory



-- 
// Copyright @ 2011 Authorized by ** LIAN LI **