[llvm-dev] Testing CFL alias analysis

Jia Chen via llvm-dev llvm-dev at lists.llvm.org
Thu May 19 12:22:52 PDT 2016

Hi Geoff,

Thank you so much for the effort!

It's good to hear that cfl-aa didn't break anything. However, the fact 
that it doesn't quite affect code generation is also concerning. I'll 
definitely look into the issue.

On 05/19/2016 02:03 PM, Geoff Berry wrote:
> Hi Jia,
> We did some testing with CFL-AA enabled on an aarch64 OoO target on the
> llvm test-suite and SPEC (with and without LTO).  We didn't observe any
> correctness issues.  We didn't really observe any positive or negative
> performance differences, other than a single llvm test
> llvm-test-suite/SingleSource/Benchmarks/Shootout/lists that improved
> ~3%.  I also looked over some of the generated code differences: only a
> handful of tests changed at all (9 in llvm test-suite, 5 in SPEC2006),
> and in most of these only a few functions changed, usually with a small
> amount of static instruction differences.  We didn't collect any compile
> time data.
> -Geoff
> On 5/16/2016 5:19 PM, Jia Chen via llvm-dev wrote:
>> Hello everyone,
>> If you've read through my previous introduction email
>> (http://lists.llvm.org/pipermail/llvm-dev/2016-May/099573.html), you
>> can safely ignore this message.
>> The short story is: CFL-AA does not seem to be broken anymore. Please
>> try it out and help us find more bugs / performance issues if
>> switching to it in the future sounds interesting to you.
>> Here are more backgrounds: I was working on a GSoC project, whose
>> first step is to fix cfl-aa. After a bug was patched up in r268269,
>> bootstrapping llvm+clang with standalone cfl-aa as well as
>> cfl-aa+basicaa breaks nothing in llvm test-suite. It shows that cfl-aa
>> is in a pretty good shape today and are almost ready to be turned out
>> by default. But before we can do this, we'd like to gather enough
>> evidences that it is a safe move. A more thorough description of the
>> current status can be found in the link provided at the beginning of
>> this message.
>> To compile your codes with cfl-aa turned on, simply add " -mllvm
>> -use-cfl-aa -mllvm -use-cfl-aa-in-codegen" option to the clang command
>> line arguments.
>> --
>> Best Regards,
>> --
>> Jia Chen
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> --
> Geoff Berry
> Employee of Qualcomm Innovation Center, Inc.
>   Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

Best Regards,

Jia Chen
Department of Computer Science
University of Texas at Austin
jchen at cs.utexas.edu

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