Hi all,

This year's FOSDEM is taking place Saturday–Sunday in Brussels (registration-less open source software event).

Any D heads in the area? Kai Nacke is going to give a talk on PGO in LDC in the LLVM dev room [1], and I'll also be around.

 — David


[1] https://fosdem.org/2017/schedule/event/ldc_d_optimization/

On Friday, 3 February 2017 at 06:59:32 UTC, David Nadlinger wrote:
> Hi all,
>
> This year's FOSDEM is taking place Saturday–Sunday in Brussels (registration-less open source software event).
>
> Any D heads in the area? Kai Nacke is going to give a talk on PGO in LDC in the LLVM dev room [1], and I'll also be around.

I am not there :/

Have fun!

On Friday, 3 February 2017 at 06:59:32 UTC, David Nadlinger wrote:
> Hi all,
>
> This year's FOSDEM is taking place Saturday–Sunday in Brussels (registration-less open source software event).
>
> Any D heads in the area? Kai Nacke is going to give a talk on PGO in LDC in the LLVM dev room [1], and I'll also be around.

Too bad that I am not there this year :( (first FOSDEM to miss in a while).
Would have been nice to meet!

Enjoy the conference and the Belgian beer!

On Friday, 3 February 2017 at 06:59:32 UTC, David Nadlinger wrote:
> 
> Kai Nacke is going to give a talk on PGO in LDC in the LLVM dev room [1], and I'll also be around.

How did it go?

- Johan

On Tuesday, 7 February 2017 at 16:57:26 UTC, Johan Engelen wrote:
> On Friday, 3 February 2017 at 06:59:32 UTC, David Nadlinger wrote:
>> 
>> Kai Nacke is going to give a talk on PGO in LDC in the LLVM dev room [1], and I'll also be around.
>
> How did it go?

A recording of Kai's talk is online here: https://fosdem.org/2017/schedule/event/ldc_d_optimization/

On Tuesday, 7 February 2017 at 17:05:48 UTC, Johan Engelen wrote:
>
> A recording of Kai's talk is online here: https://fosdem.org/2017/schedule/event/ldc_d_optimization/

Thanks for a nice talk Kai :-)

(please excuse the thread steal)
Some additional answers to the questions raised:

- Using LLVM IR PGO, instead of front-end PGO
Yep... I think frontend PGO is doomed... sad :/ calculating statement execution counts from a minimal set of counters was nice to work on and interesting code. VCP can be done by the backend too (and IIRC _is_ already done) if it has access to vtables, etc. To enable backend VCP, I believe clang emits a little bit extra (e.g. vtables) to IR where it is not needed otherwise. With LTO, the backend already has all the info it needs.
Performance-wise, the IR PGO should result in a better profile as it can profile optimized code which can be hugely different from non-optimized code (inlining!!!).
At the very least, we now have the PGO infrastructure ready and can easily provide an IR PGO flag (and should soon!).  When Clang/LLVM/LDC versions are in-sync, this should give us cross-language LTO+PGO. (^_^)

- Memory alloc call profiling
Something related in progress in LLVM: https://reviews.llvm.org/D28965

-Johan