[llvm-dev] LLVM AutoFDO status

[Eric Christopher via llvm-dev]

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
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