[Flang][OpenMP][Task] Loop iteration variable treated as firstprivate instead of private in task construct

[kaviya2510]

According to the OpenMP specification, Loop iteration variables inside parallel, teams, or task generating constructs are private in the innermost such construct that encloses the loop.

In the following example:

subroutine test()
  integer :: x
  !$omp task
  do i = 1, 10
    x = 1
  end do
  !$omp end task
end subroutine

The loop iteration variable i must be treated as private to task. However, the current behavior treats i as firstprivate, which is incorrect.

Here is the generated FIR which treats the variable i as firstprivate : Godbolt link

  omp.private {type = firstprivate} @_QFtestEx_firstprivate_i32 : i32 copy {
  ^bb0(%arg0: !fir.ref<i32>, %arg1: !fir.ref<i32>):
    %0 = fir.load %arg0 : !fir.ref<i32>
    hlfir.assign %0 to %arg1 : i32, !fir.ref<i32>
    omp.yield(%arg1 : !fir.ref<i32>)
  }

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Kaviya Rajendiran (kaviya2510)

According to the OpenMP specification, ***Loop iteration variables inside parallel, teams, or task generating constructs are **private** in the innermost such construct that encloses the loop.***

In the following example:

subroutine test()
  integer :: x
  !$omp task
  do i = 1, 10
    x = 1
  end do
  !$omp end task
end subroutine

The loop iteration variable i must be treated as private to task. However, the current behavior treats i as firstprivate, which is incorrect.

Here is the generated FIR which treats the variable i as firstprivate : Godbolt link

  omp.private {type = firstprivate} @<!-- -->_QFtestEx_firstprivate_i32 : i32 copy {
  ^bb0(%arg0: !fir.ref&lt;i32&gt;, %arg1: !fir.ref&lt;i32&gt;):
    %0 = fir.load %arg0 : !fir.ref&lt;i32&gt;
    hlfir.assign %0 to %arg1 : i32, !fir.ref&lt;i32&gt;
    omp.yield(%arg1 : !fir.ref&lt;i32&gt;)
  }

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: Kaviya Rajendiran (kaviya2510)

According to the OpenMP specification, ***Loop iteration variables inside parallel, teams, or task generating constructs are **private** in the innermost such construct that encloses the loop.***

In the following example:

subroutine test()
  integer :: x
  !$omp task
  do i = 1, 10
    x = 1
  end do
  !$omp end task
end subroutine

The loop iteration variable i must be treated as private to task. However, the current behavior treats i as firstprivate, which is incorrect.

Here is the generated FIR which treats the variable i as firstprivate : Godbolt link

  omp.private {type = firstprivate} @<!-- -->_QFtestEx_firstprivate_i32 : i32 copy {
  ^bb0(%arg0: !fir.ref&lt;i32&gt;, %arg1: !fir.ref&lt;i32&gt;):
    %0 = fir.load %arg0 : !fir.ref&lt;i32&gt;
    hlfir.assign %0 to %arg1 : i32, !fir.ref&lt;i32&gt;
    omp.yield(%arg1 : !fir.ref&lt;i32&gt;)
  }