[llvm-dev] Profile-based inlining status

[Xinliang David Li via llvm-dev]

On Mon, Mar 7, 2016 at 11:42 PM, Mehdi Amini via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>
> On Mar 7, 2016, at 8:58 AM, Toshio Suganuma via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hello,
>
> I'm learning how LLVM performs PGO (profile-guided optimizations) by using
> the instrumentation-based profile build (-fprofile-instr-generate and
> -fprofile-instr-use).
> However, I found there is no difference in inlining behaviors between with
> and without PGO for a few spec benchmarks by checking the emit optimization
> reports (-Rpass=inline -Rpass-missed=inline -Rpass-analysis=inline). Also,
> the profile information collected contains only block counters, not call
> counters.
>
> Since a call is necessarily in a block, I'm not sure what extra
> information you would get with a call counter?
>
> This seems to indicate that the profile-based inlining is not supported
> yet (my LLVM/Clang is 3.9.0, mid Feb trunk). Is this the case?
>
> The talk in the LLVM conference 2013 (
> http://llvm.org/devmtg/2013-11/slides/Carruth-PGO.pdf) actually describes
> that "the inliner doesn't even know profile information exists today" (page
> 89), but it's been more than two years since that statement. Can you let me
> know the latest status or any ongoing work for the profile-based inlining
> (both same-module and cross-module inlining)?
>
> I believe it was added recently (last December, see
> http://reviews.llvm.org/D15245 ), so a trunk version should definitely
> have it.
>

There is a more recent patch that does the whole thing (including
incremental update) that is under review.

David


>
> --
> Mehdi
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160308/c6cd6bee/attachment.html>