<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/192989>192989</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Clang][Flang][OpenMP] `omp_initial_device` / `omp_invalid_device` not accepted as valid device IDs
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang,
            flang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Thyre
      </td>
    </tr>
</table>

<pre>
    The OpenMP v5.2 and OpenMP v6.0 specification state (here from OpenMP v6.0):

> Additionally, the predefined identifier `omp_initial_device` can be used as an alias for the host device and the predefined identifier `omp_invalid_device` can be used to specify an invalid device number. 
A conforming device number is either a non-negative integer that is less than or equal to the value returned by `omp_get_num_devices` or equal to `omp_initial_device` or `omp_invalid_device`.

With the following handling for both values:

**`omp_initial_device`**:
> When an if clause is present and if-expression evaluates to false, the effect is as if a device clause that specifies `omp_initial_device` as the device number is present, regardless of any other device clause on the directive.

**`omp_invalid_device`**:
> If the device-description evaluates to `omp_invalid_device`, runtime error termination is performed.

While both Clang and Flang any positive integer value, both `omp_initial_device` and `omp_invalid_device` are rejected if the value is a constant in the directive:

**Clang:**
```c
#include <omp.h>

int main( void )
{
    #pragma omp target device( -1 /*omp_initial_device missing*/ )
        {}
    #pragma omp target device( omp_invalid_device )
 {}
}
```

```console
$ clang -fopenmp --offload-arch=gfx1101 test.2.c
test.c:5:32: error: argument to 'device' clause must be a non-negative integer value
    5 |     #pragma omp target device( -1 /*omp_initial_device missing*/ )
      | ^~
test.c:7:32: error: argument to 'device' clause must be a non-negative integer value
    7 |     #pragma omp target device( omp_invalid_device )
 | ^~~~~~~~~~~~~~~~~~
/opt/apps/software/Clang/trunk/lib/clang/23/include/omp.h:556:32: note: expanded from macro 'omp_invalid_device'
  556 |     #define omp_invalid_device -2
      |                                ^~
2 errors generated.
```

**Flang:**
```f90
program main
    use omp_lib
    ! OMP_INITIAL_DEVICE missing
    !$OMP TARGET DEVICE( -1 )
    !$OMP END TARGET

    !$OMP TARGET DEVICE( OMP_INVALID_DEVICE )
    !$OMP END TARGET
end program main
```

```console
$ flang -fopenmp --offload-arch=gfx1101 test.f90
error: Semantic errors in test.f90
test.f90:4:18: error: The device expression of the DEVICE clause must be a positive integer expression
      !$OMP TARGET DEVICE( -1 )
 ^^^^^^^^^^^^
test.f90:7:26: error: Must have INTEGER type, but is REAL(4)
      !$OMP TARGET DEVICE( OMP_INVALID_DEVICE )
 ^^^^^^^^^^^^^^^^^^
```

----

For Flang, this is checked during `OmpStructureChecker::Enter` with a `RequiresPositiveParameter` (see [here](https://github.com/llvm/llvm-project/blob/61f33bc546596d4c4a99a25c530942862d00a1d6/flang/lib/Semantics/check-omp-structure.cpp#L4507)).
This check would need to get replaced by a check also allowing `-1` (i.e. `omp_initial_device`) and `-2` (i.e. `omp_invalid_device`) to be passed. The second error (`Must have INTEGER type, but is REAL(4)`) is likely an additional bug that needs some attention...

For Clang, the check should happen in `SemaOpenMP::ActOnOpenMPDeviceNum` (see [here](https://github.com/llvm/llvm-project/blob/5d98f79f52dd56750e826eb6efcd8b5cf41de239/clang/lib/Sema/SemaOpenMP.cpp#L17365)).

Even if handling during code building is fixed, https://github.com/llvm/llvm-project/issues/192980 needs to get fixed as well, so that the device mapping works correctly.
</pre>
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