[LLVMdev] Instrumentation based Profiling

[Justin Bogner]

Jeremy Salwen <jeremysalwen at gmail.com> writes:
> I'm wondering as to the status of control flow profiling in llvm.  From what I
> can gather there was an old system (using opt -insert-edge-profiling and the
> like)  which was removed in this commit llvm.org/viewvc/llvm-project?view=
> revision&revision=191835 . The commit message mentions "modern PGO efforts",
> but I can't find anything in the source tree or documentation. Who is working
> on the newer efforts and what is their status? If there's work that still
> needs to be done, I'd be happy to help out in a serious way.

The mention of "modern PGO efforts" is about two things:

- Sampling profilers, as documented in
  http://clang.llvm.org/docs/UsersManual.html#using-sampling-profilers-for-optimization

- Frontend instrumentation profiling. This really isn't documented at
  all yet, but it consists of the -fprofile-instr-generate and
  -fprofile-instr-use flags, and the llvm-profdata tool. I'll add some
  notes to the user guide this week - sorry that I haven't gotten to it
  sooner.