[Flang][OpenMP] Execution error (Segmentation fault) when an allocatable array is used in task construct with a firstprivate clause in a parallel construct with a private clause

[ohno-fj]

Version of flang-new : 19.0.0(cbcdf126ccc774c063b5d5140c1393ff5305dded)/AArch64

When an allocatable array is used in task construct with a firstprivate clause in a parallel construct with a private clause, the execution terminates abnormally (Segmentation fault).

Execution terminates normally in the following cases:

• Array (a) is not an allocatable array, or
• Do not write task construct

The following are the test program, Flang-new, Gfortran and ifort compilation/execution result.

omp3_task_firstprivate_013_232.f90:

program main
  integer(4),allocatable::a(:)
  allocate(a(10))
  a(9)=100
!$omp parallel private(a)
!$omp task firstprivate(a)
  a(9)=10
!$omp end task
!$omp end parallel
  write(6,*) "a(9) = ", a(9)
end program main

$ export OMP_NUM_THREADS=2; flang-new -fopenmp omp3_task_firstprivate_013_232.f90; ./a.out
Segmentation fault (core dumped)
$

$ export OMP_NUM_THREADS=2; gfortran -fopenmp omp3_task_firstprivate_013_232.f90; ./a.out
 a(9) =          100
$

$ export OMP_NUM_THREADS=2; ifort -qopenmp -diag-disable=10448 omp3_task_firstprivate_013_232.f90; ./a.out
 a(9) =          100
$

[llvmbot]

@llvm/issue-subscribers-openmp

Author: None (ohno-fj)

``` Version of flang-new : 19.0.0(cbcdf12)/AArch64 ```

When an allocatable array is used in task construct with a firstprivate clause in a parallel construct with a private clause, the execution terminates abnormally (Segmentation fault).

Execution terminates normally in the following cases:

• Array (a) is not an allocatable array, or
• Do not write task construct

The following are the test program, Flang-new, Gfortran and ifort compilation/execution result.

omp3_task_firstprivate_013_232.f90:

program main
  integer(4),allocatable::a(:)
  allocate(a(10))
  a(9)=100
!$omp parallel private(a)
!$omp task firstprivate(a)
  a(9)=10
!$omp end task
!$omp end parallel
  write(6,*) "a(9) = ", a(9)
end program main

$ export OMP_NUM_THREADS=2; flang-new -fopenmp omp3_task_firstprivate_013_232.f90; ./a.out
Segmentation fault (core dumped)
$

$ export OMP_NUM_THREADS=2; gfortran -fopenmp omp3_task_firstprivate_013_232.f90; ./a.out
 a(9) =          100
$

$ export OMP_NUM_THREADS=2; ifort -qopenmp -diag-disable=10448 omp3_task_firstprivate_013_232.f90; ./a.out
 a(9) =          100
$

[luporl]

This issue probably has the same root cause as #71369.
It doesn't occur if !$omp taskwait is inserted before !$omp end parallel.

[tblah]

Thanks for reporting this. It should be fixed after #125307

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: None (ohno-fj)

``` Version of flang-new : 19.0.0(cbcdf12)/AArch64 ```

When an allocatable array is used in task construct with a firstprivate clause in a parallel construct with a private clause, the execution terminates abnormally (Segmentation fault).

Execution terminates normally in the following cases:

• Array (a) is not an allocatable array, or
• Do not write task construct

The following are the test program, Flang-new, Gfortran and ifort compilation/execution result.

omp3_task_firstprivate_013_232.f90:

program main
  integer(4),allocatable::a(:)
  allocate(a(10))
  a(9)=100
!$omp parallel private(a)
!$omp task firstprivate(a)
  a(9)=10
!$omp end task
!$omp end parallel
  write(6,*) "a(9) = ", a(9)
end program main

$ export OMP_NUM_THREADS=2; flang-new -fopenmp omp3_task_firstprivate_013_232.f90; ./a.out
Segmentation fault (core dumped)
$

$ export OMP_NUM_THREADS=2; gfortran -fopenmp omp3_task_firstprivate_013_232.f90; ./a.out
 a(9) =          100
$

$ export OMP_NUM_THREADS=2; ifort -qopenmp -diag-disable=10448 omp3_task_firstprivate_013_232.f90; ./a.out
 a(9) =          100
$