0a4798ad4b
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@fz-juelich.de>
17 KiB
17 KiB