[Flang][OpenMP]Incorrect execution result when reduction-identifier(+) is used in REDUCTION clause during the reduction(-) operation

[ohno-fj]

Version of flang-new : 17.0.0(359f170f5f712ee714193b46bad45a45656b2c59)

Using the reduction-identifier(+) in the REDUCTION clause during a reduction(-) operation results in incorrect execution.

The result is correct when the test program is modified as follows:

• Before the change

         ia = ia-i

• After the change

         ia = ia+(-i)

z012.f90:

      program main
      integer*4 ia
      integer*4 :: loop=10
      ia = 0
!$omp parallel do reduction(+:ia)
      do i=1, loop
         ia = ia-i
      end do
!$omp end parallel do
      write(*,*) "     ia=",ia,"  It must be -55"
      end

$ export OMP_NUM_THREADS=2; flang-new -fopenmp z012.f90; ./a.out
      ia= 55   It must be -55
$

$ export OMP_NUM_THREADS=2; gfortran -fopenmp z012.f90; ./a.out
      ia=         -55   It must be -55
$

$ export OMP_NUM_THREADS=2; ifort -qopenmp z012.f90; ./a.out
      ia=         -55   It must be -55
$

[llvmbot]

@llvm/issue-subscribers-openmp

[llvmbot]

@llvm/issue-subscribers-flang-frontend

[kiranchandramohan]

We are reviewing reduction handling and will come to this soon.

[kiranchandramohan]

This is fixed by #80019

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: None (ohno-fj)

``` Version of flang-new : 17.0.0(359f170) ```

Using the reduction-identifier(+) in the REDUCTION clause during a reduction(-) operation results in incorrect execution.

The result is correct when the test program is modified as follows:

• Before the change

         ia = ia-i

• After the change

         ia = ia+(-i)

z012.f90:

      program main
      integer*4 ia
      integer*4 :: loop=10
      ia = 0
!$omp parallel do reduction(+:ia)
      do i=1, loop
         ia = ia-i
      end do
!$omp end parallel do
      write(*,*) "     ia=",ia,"  It must be -55"
      end

$ export OMP_NUM_THREADS=2; flang-new -fopenmp z012.f90; ./a.out
      ia= 55   It must be -55
$

$ export OMP_NUM_THREADS=2; gfortran -fopenmp z012.f90; ./a.out
      ia=         -55   It must be -55
$

$ export OMP_NUM_THREADS=2; ifort -qopenmp z012.f90; ./a.out
      ia=         -55   It must be -55
$