[llvm-dev] Profile-based inlining status

[Xinliang David Li via llvm-dev]

You are right that inliner does not yet know profile information at
callsite level (only knows about if callee is hot -- later is also not
correct as it is not updated at all).

We are working on this. A patch was committed to enable profile/profile
update in inliner recently, but got temporarily reverted for further
discussion. We will announce it once the feature is in trunk.

thanks,

David

On Mon, 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. 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)?
>
> Thank you,
> --Toshio
>
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