[flang-commits] [flang] Redo [flang][OpenMP] Implement collapse for imperfectly nested loops (PR #208528)

[Sairudra More via flang-commits]

https://github.com/Saieiei commented:

I reproduced a remaining target-lowering failure at the current head (`1ffd30ed`):

```fortran
subroutine repro(n, m, x)
  implicit none
  integer, intent(in) :: n, m
  integer, intent(inout) :: x
  integer :: i, j

  !$omp target teams distribute parallel do collapse(2) map(tofrom:x)
  do i = 1, n
    do j = 1, m
      x = x + 1
    end do
    x = x + j
  end do
end subroutine
```

```text
%flang_fc1 -emit-hlfir -fopenmp repro.f90 -o -
'omp.target' op host_eval argument illegal use in 'arith.addi' operation
```

`genCollapsedLoopNestBody` uses host-evaluated loop bounds in the intervening-code guard and terminal-IV restoration (`arith.cmpi`/`arith.addi`), which the target verifier rejects. The equivalent non-target loop lowers successfully.

The `ContinueStmt` change fixes the labeled empty-loop case, but genuine intervening code under `omp.target` still fails. Could this path be handled or diagnosed as not yet supported and covered by a non-empty target regression before relanding?


https://github.com/llvm/llvm-project/pull/208528