[Bug middle-end/119036] New: [OpenMP] dispatch with interop(obj) clause and obj == omp_interop_none should not set default-device-var ICV

[burnus at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119036

            Bug ID: 119036
           Summary: [OpenMP] dispatch with interop(obj) clause and obj ==
                    omp_interop_none should not set default-device-var ICV
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: openmp
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org
                CC: sandra at gcc dot gnu.org
  Target Milestone: ---

OpenMP has:

"If the 'interop' clause is present and has only one interop-var, and the
'device' clause is not specified, the behavior is as if the 'device' clause is
present with a device-description equivalent to the device_num property of the
interop-var."

This does not (yet) specify what happens when interop-var has the value
omp_interop_none but IMHO, it makes most sense to not touch the
default-device-var ICV.
→ associated OpenMP issue is #4459

Currently, the GCC uses - in gcc/gimplify.cc's gimplify_omp_dispatch:

  dev_num = omp_get_interop_int(obj, omp_ipr_device_num, NULL);

Expected - either of

(a) Use omp_default_device, i.e.
    dev_num = obj == omp_interop_none ? omp_default_device
               : omp_get_interop_int(obj, omp_ipr_device_num, NULL);

    → This requires that omp_default_device support has been added to
      omp_set_default_device + omp_default_device added to
      include/gomp-constants.h

(b) Guard the code, i.e. 

     if (obj != omp_interop_none)
       {
         dev_num = omp_get_interop_int(obj, omp_ipr_device_num, NULL);
         saved_device = omp_get_default_device ();
         omp_set_default_device (dev_num);
       }
     ...
     if (obj != omp_interop_none)
       omp_set_default_device (saved_dev_num);

Regarding (a): To make that OpenMP 6.1/TR15 feature available to the users, it
additionally has to be added to libgomp/{omp.h.in,omp_lib.{f90,h}.in} and
libgomp/target.c.