[flang][OpenMP] Regression with character allocatables and FIRSTPRIVATE

[eugeneepshteyn]

The following sample started regressing recently:

  implicit none
  character(10), allocatable :: src
  integer :: i
  src = "hello"
  !$OMP PARALLEL DO FIRSTPRIVATE(src)
    Do i=1,1
    End Do
  !$OMP END PARALLEL DO
  end

Failure:

$ flang -c -fopenmp test.f90 
flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
error: loc(".../test.f90":2:33): 'fir.embox' op CHARACTER already has static LEN
error: verification of lowering to FIR failed
$ flang --version
flang version 21.0.0git (https://github.com/llvm/llvm-project c32cd5746b1335ed172d1bf58fb6498b479bd8e0)
Target: x86_64-unknown-linux-gnu
Thread model: posix
...

[eugeneepshteyn]

The following flang revision compiles the sample correctly:

$ flang --version
flang version 21.0.0git (https://github.com/llvm/llvm-project cc0d4a5188f9e41dd8e00048d17b87529e28b694)
Target: x86_64-unknown-linux-gnu
Thread model: posix
...

I haven't yet bisected to the exact commit that failed.

Note: the following commit happened in that time and seems to be relevant: #125732

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: Eugene Epshteyn (eugeneepshteyn)

The following sample started regressing recently: ``` implicit none character(10), allocatable :: src integer :: i src = "hello" !$OMP PARALLEL DO FIRSTPRIVATE(src) Do i=1,1 End Do !$OMP END PARALLEL DO ``` Failure: ``` $ flang -c -fopenmp test.f90 flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option] error: loc(".../test.f90":2:33): 'fir.embox' op CHARACTER already has static LEN error: verification of lowering to FIR failed $ flang --version flang version 21.0.0git (https://github.com/llvm/llvm-project c32cd57) Target: x86_64-unknown-linux-gnu Thread model: posix ... ```

[eugeneepshteyn]

The issue was fixed.