[Openmp-commits] [openmp] [OpenMP][OMPT] Add OMPT callback for device data exchange 'Device-to-Device' (PR #81991)

[Michael Halkenhäuser via Openmp-commits]

mhalk wrote:

> x86_64 still reports two transfers even though `LIBOMPTARGET_DEBUG` shows `omptarget --> copy from device to device`.

Just reproduced this behavior within the testcase and I'll discuss this shortly but my guess is that the `x86_64` plugin is simply handling the 'data exhange' differently (chopping it into a pair of retrieve+submit via the initial device).
My take is: changing that particular behavior is beyond the scope of this PR and should be discussed beforehand.

Observing `x86_64` callbacks seems like a very peculiar use-case to me TBH, especially since there is no accurate representation of the actually present / 'real' devices AFAIK. My _assumption_ is, that the latter is also the reason why we take the route 'retrieve+submit' via the 'real' (initial) device.

https://github.com/llvm/llvm-project/pull/81991