[PATCH] D15828: [PGO] Passmanagerbuilder change that enable IR level PGO instrumentation

[Mehdi Amini via llvm-commits]

> On Jan 3, 2016, at 5:23 PM, David Li <davidxl at google.com> wrote:
> 
> davidxl added inline comments.
> 
> ================
> Comment at: lib/Transforms/IPO/PassManagerBuilder.cpp:281
> @@ -239,1 +280,3 @@
> 
> +  addPGOInstrPasses(MPM);
> +
> ----------------
> chandlerc wrote:
>> davidxl wrote:
>>> joker.eph wrote:
>>>> There will be an inliner SCC pass manager created in the PGO InstrPasses. It is not clear to me why you don't integrate this with the regular inliner a few line below.
>>> This is the pre-inline pass that needs to happen before instrumentation. See the original RFC: http://lists.llvm.org/pipermail/llvm-dev/2015-August/089425.html for details.
>> Yes, and there was not consensus in the RFC for the pre-inlining. Instead, the approach suggested was to work on independent components which seem non-controversial and have a separate focused discussion about pre-inlining and other interactions.
>> 
>> I think there are still a lot of unanswered questions around the pre-inlining phase (based on my reading of the RFC thread you pointed at). If there is some other thread that I've not seen, feel free to direct there...
> The original RFC discussion is here: https://groups.google.com/forum/#!topic/llvm-dev/ncONLhVJ3L0

Do you prefer the discussion to continue on the RFC thread or here?

I missed the fact that PGOInstrumentationGen/PGOInstrumentationUse are Module pass, I thought they were function passes and thus would be ran during the SCC Pass Manager with all the passes that follow the Inliner.
I guess they can’t be FunctionPass because they create global variables for the counters...

Thanks,

Mehdi