[PATCH] D44519: Add llvm-exegesis tool.

[Andrea Di Biagio via Phabricator via llvm-commits]

andreadb added a comment.

Hi Clement,

Thanks for the tool. Could you please rebase the patch?

I finally managed to test the tool on my linux machine. However, I was unable to get some numbers on AMD cpus.

The major problem I see is that the tool expects perf event "UNHALTED_CORE_CYCLES" to be always available. However, that event is Intel specific.

I tried to manually change it to something meaningful for my system. However, it would be really nice if we find a way to abstract "generic perf events".
For example, we could have the "generic cpu clock" event, which targets/subtargers can define as a alias for a specific hw event type. So, on Intel chips, that "generic cpu clock" event would be wired to UNHALTED_CORE_CYCLES. Is there a plan for doing it?

The other problem is the dependency with libpfm. At the moment, this is not a big deal for people that work on linux. I don't know if there is an equivalent library for windows. However, if I remember correctly, libpfm builds on top of the linux perf events.  Is there a plan to get rid of that dependency?

Overally, I really like the tool and the goals that it plans to achieve.
At the moment, my concern is that the tool is limited to a very specific system and CPU family.

So, I am okay with this patch as long as there is a plan to remove the dependency with cpu vendor specific hardware perf events (at least in the medium term).

About the patch:
I noticed that you added your name in most TODO comments. Example "// TODO(courbet): Handle memory.". Please remove your name, and possibly make some of those comments more descriptive.


Repository:
  rL LLVM

https://reviews.llvm.org/D44519