[all-commits] [llvm/llvm-project] 0a4798: [OMPT][OpenMP] Use omp_initial_device for host in ...

[Jan André Reuter via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0a4798ad4b9612f9499f4c13104603a4c94a6144
      https://github.com/llvm/llvm-project/commit/0a4798ad4b9612f9499f4c13104603a4c94a6144
  Author: Jan André Reuter <j.reuter at fz-juelich.de>
  Date:   2026-04-29 (Wed, 29 Apr 2026)

  Changed paths:
    M offload/libomptarget/OpenMP/OMPT/Callback.cpp
    M offload/libomptarget/device.cpp
    M offload/test/ompt/target_memcpy.c
    M offload/test/ompt/target_memcpy_emi.c
    M openmp/runtime/src/ompt-general.cpp

  Log Message:
  -----------
  [OMPT][OpenMP] Use omp_initial_device for host in callbacks (#192924)

The OpenMP specification offers different ways for identifying the host
device. While users of the OpenMP API can use `omp_get_initial_device()`
or the constant `omp_initial_device` (available since OpenMP v5.2), a
tool needs to rely on the `initial_device_num` passed by the OpenMP
runtime during the `initialize` callback.

In #134451, it was discovered that the `initial_device_num` passed is
always `0`, regardless of any device are available for offload
execution. For host-only OpenMP code, this matches the result of
`omp_get_num_devices()`, and is a valid result. In the case of devices
being available though, this passed identifier is incorrect. While
`libomp` calls `omp_get_num_devices()`, `libomptarget` has not fully
initialized its PluginManager at that point, hence returning no
available devices. Tools relying on `initial_device_num` might therefore
incorrectly assume host-side execution when some code runs on a device.
Since the `ompt_get_num_devices()` entry point is also not fully
implemented, tools currently need to do on-the-fly handling for the host
device.

To make handling easier, consistently use the `omp_initial_device`
identifier as the `initial_device_num` and for all device callbacks.
This does not rely on knowing the number of available devices during
OMPT initialization in the runtime and ensures a consistent value for
tools to handle.

Closes #134451

Signed-off-by: Jan André Reuter <j.reuter at fz-juelich.de>



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