[flang][OpenMP] Add a semantic check to prevent atomic operations on character variables

[tblah]

program o30_301
  character(2) hi
  !$omp atomic write
    hi = 'hi'
  !$omp end atomic
end program

Fails with not yet implemented: Unsupported atomic type. The wording of the standard is that atomic operations should operate on "scalar variables of intrinsic type" (OpenMP 5.2 section 4.3.1.3).

In Fortran 2023, a scalar variable is defined (3.119) as "data entity that can be represented by a single value of the type and that is not an array". I think that means that a the character variable in the above example is scalar and of intrinsic type.

gfortran and classic flang do not allow character variables in atomic types.

[kkwli]

A scalar variable in the OpenMP spec is defined as: "For Fortran, a scalar variable with intrinsic type, as defined by the base language, excluding character type." (OpenMP 5.2 14:7-8)

I think flang should issue an error but not "not yet implement: ...".

[tblah]

Thanks. I agree. This should be a semantic error then

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Tom Eccles (tblah)

``` program o30_301 character(2) hi !$omp atomic write hi = 'hi' !$omp end atomic end program ```

Fails with not yet implemented: Unsupported atomic type. The wording of the standard is that atomic operations should operate on "scalar variables of intrinsic type" (OpenMP 5.2 section 4.3.1.3).

In Fortran 2023, a scalar variable is defined (3.119) as "data entity that can be represented by a single value of the type and that is not an array". I think that means that a the character variable in the above example is scalar and of intrinsic type.

gfortran and classic flang do not allow character variables in atomic types.