[llvm-dev] Testing CFL alias analysis

Geoff Berry via llvm-dev llvm-dev at lists.llvm.org
Thu May 19 12:03:06 PDT 2016

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.


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

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