[llvm] [OpenMP][offload] Add LIBOMPTARGET_KERNEL_EXE_TIME (PR #222105)

[Michael Klemm via llvm-commits]

mjklemm wrote:

> > For my learning, if this feature is out of scope for runtime, where would you suggest to have it or such features? Thanks!
> 
> It is profiler's job.

I do not disagree with that profiler can be used for that.  I disagree with the premise that this facility should not exist.  Having a quick performance snapshot via a direct runtime facility makes absolute sense to have and reduces the amount of effort to invest at the user to get some first insight.  With LIBOMPTARGET_KERNEL_TRACE or LIBOMPTARGET_PLUGIN_PROFILE, I can get quick statistics w/o having to start rocproc, VTune or any big profiling tool.

https://github.com/llvm/llvm-project/pull/222105