[LLVMdev] Instrumentation based Profiling

[Jeremy Salwen]

Hi Justin,

I've been searching the mailing list and the web for discussion of the
frontend instrumentation profiling.  Is there some sort of a design
document or thread where it was discussed?  I'm curious why it was
implemented in the frontend instead of a pass on the IR.

Thanks,
Jeremy


On Mon, Jun 9, 2014 at 2:20 PM, Justin Bogner <mail at justinbogner.com> wrote:

> Jeremy Salwen <jeremysalwen at gmail.com> writes:
> > I'm wondering as to the status of control flow profiling in llvm.  From
> what I
> > can gather there was an old system (using opt -insert-edge-profiling and
> the
> > like)  which was removed in this commit
> llvm.org/viewvc/llvm-project?view=
> > revision&revision=191835 . The commit message mentions "modern PGO
> efforts",
> > but I can't find anything in the source tree or documentation. Who is
> working
> > on the newer efforts and what is their status? If there's work that still
> > needs to be done, I'd be happy to help out in a serious way.
>
> The mention of "modern PGO efforts" is about two things:
>
> - Sampling profilers, as documented in
>
> http://clang.llvm.org/docs/UsersManual.html#using-sampling-profilers-for-optimization
>
> - Frontend instrumentation profiling. This really isn't documented at
>   all yet, but it consists of the -fprofile-instr-generate and
>   -fprofile-instr-use flags, and the llvm-profdata tool. I'll add some
>   notes to the user guide this week - sorry that I haven't gotten to it
>   sooner.
>
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