State of AutoFDO in GCC

[Andi Kleen]

On Mon, Apr 26, 2021 at 06:40:56PM +0000, Hongtao Yu wrote:
>    Andi, thanks for pointing out the perf script issues. Can you please
>    elaborate a bit on the exact issue you have seen? We’ve been using
>    specific output of perf script such as mmap, LBR and callstack events
>    filtered by process id. It works fine so far but may certainly hit issues
>    in the future with extended uses.

Okay I took a look at the latest autofdo now. It seems to be basically
a LLVM project now that depends on LLVM to even build with all kinds
of dependency hell on some old LLVM version and other packages.

I guess gcc will really need a replacement that doesn't pull in
all of LLVM if it wants to continue supporting autofdo.

I'm myself unable to build now.

I'm using the old version I had a git fork of and that 
was before all of this. I added a patch to make it work
with the latest perf by ignoring increased perf_attr
and unknown perf events.

Honza please use

https://github.com/andikleen/autofdo -b perf-future

for testing.

-Andi