[llvm-dev] LLVM AutoFDO status

Eric Christopher via llvm-dev llvm-dev at lists.llvm.org
Sat Oct 10 00:10:50 PDT 2015

That said, this is great news! I'm ecstatic to see that the sample based
FDO is doing well on llvm. :)


On Sat, Oct 10, 2015 at 12:09 AM Eric Christopher <echristo at gmail.com>

> Hi Dehao,
> Do you have any specific bugs for "inaccurate/lost debug info"? I haven't
> seen anything and I'm curious what you might be running into.
> Thanks.
> -eric
> On Fri, Oct 9, 2015 at 3:08 PM Dehao Chen via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>> With recent bug fixes and performance tunings, AutoFDO at llvm has reached
>> a usable state. To evaluate performance, we used
>> O3/-fprofile-use/-fprofile-sample-use respectively to optimize clang
>> itself, and measure its speed.
>> clang built with -fprofile-use is ~20% faster than clang built with O3
>> clang built with -fprofile-sample-use is ~10% faster than clang built
>> with O3
>> AutoFDO can deliver 50% of the FDO speedup to clang. The gap is mainly
>> due to inaccurate/lost debug info, which is used to represent the profile.
>> I am still tuning the performance to fill in the gap.
>> During the meantime, we encourage you to try it out. Bug reports/fixes
>> are always welcome. For more information about how to generate AutoFDO
>> profile, please refer to https://github.com/google/autofdo
>> Cheers,
>> Dehao
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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