[flang] Failure with do_concurrent: redefinition of symbol named 'add_reduction_f64.omp'

[vzakhari]

The issue appears in some benchmark code with -fdo-concurrent-to-openmp=host:

flang -c -o test.fppized.o -O1 -fopenmp -fdo-concurrent-to-openmp=host test.fppized.f90
warning: Mapping `do concurrent` to OpenMP is still experimental.
error: loc("test.fppized.f90":6723:7): redefinition of symbol named 'add_reduction_f64.omp'
error: verification of lowering to FIR failed

Simple reprorucer:

subroutine test1(x,s,N)
  real :: x(N), s
  integer :: N
  do concurrent(i=1:N) reduce(+:s)
     s=s+x(i)
  end do
end subroutine test1
subroutine test2(x,s,N)
  real :: x(N), s
  integer :: N
  do concurrent(i=1:N) reduce(+:s)
     s=s+x(i)
  end do
end subroutine test2

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: Slava Zakharin (vzakhari)

The issue appears in 800.pot3d_s with `-fdo-concurrent-to-openmp=host`: ``` flang -c -o pot3d.fppized.o -O1 -fopenmp -fdo-concurrent-to-openmp=host pot3d.fppized.f90 warning: Mapping `do concurrent` to OpenMP is still experimental. error: loc("pot3d.fppized.f90":6723:7): redefinition of symbol named 'add_reduction_f64.omp' error: verification of lowering to FIR failed ```

Simple reprorucer:

subroutine test1(x,s,N)
  real :: x(N), s
  integer :: N
  do concurrent(i=1:N) reduce(+:s)
     s=s+x(i)
  end do
end subroutine test1
subroutine test2(x,s,N)
  real :: x(N), s
  integer :: N
  do concurrent(i=1:N) reduce(+:s)
     s=s+x(i)
  end do
end subroutine test2