[llvm-dev] LLVM AutoFDO status

[Eric Christopher via llvm-dev]

On Sat, Oct 10, 2015 at 9:53 AM Xinliang David Li <davidxl at google.com>
wrote:

> On Sat, Oct 10, 2015 at 12:09 AM, Eric Christopher <echristo at gmail.com>
> wrote:
> > 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.
>
> Those lost info are mostly due to optimizations (examples include code
> introduced by the optimizer, such as those from strength reduction,
> runtime condition check etc) -- not that the base debug info
> generation has anything wrong..
>
>
Aha! Excellent. Both good to hear and I look forward (and don't look
forward) to those bugs :)

-eric


> David
>
> >
> > 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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