[flang] Runtime error of `Invalid descriptor` when deallocate an allocated pointer.

[DanielCChen]

Consider the following code:

module m
    type base
        integer :: id
    end type

    type container
        !class (base), pointer :: data => null()
        type(base), pointer :: data => null()
    end type

    contains

    pure function makeData (i)
        type (base), pointer :: makeData
        integer*4, intent(in) :: i

        allocate (makeData)

        makeData = base(i)
    end function


end module

program fpAssgn016
use m
    type (container) :: co1(10)

   forall (i=1:10)
!   do i = 1,10                           !! work around
        co1(i)%data => makeData (i)
!   end do
    end forall

    do i =1, 10
        deallocate (co1(i)%data)
    end do

end

Flang failed at the runtime as

> a.out

fatal Fortran runtime error(t.f:36): Invalid descriptor
Abort(coredump)

This failure seems a regression after the merge of PR #164279. However, if I changed the LHS to be NOT polymorphic, it still fails the same.

It seems the "allocatable" property got lost through the pointer assignment in FORALL.

[DanielCChen]

A further reduced test case to show the non-polymorphic failure

module m
    type base
        real, pointer :: data => null()
    end type

    contains

     pure function makeData (i)
        real, pointer :: makeData
        integer*4, intent(in) :: i

        allocate (makeData)

        makeData = i
    end function


end module

program fpAssgn016
use m
    type (base) :: co1(10)

   forall (i=1:10)
        co1(i)%data => makeData (i)
    end forall

    do i =1, 10
        print*, co1(i)%data
        deallocate (co1(i)%data)
    end do

end

[DanielCChen]

With the further reduced test case, the culprit fir seems at the place when the result of calling function makeData is pushed into the descriptor stack. It looks like

    fir.do_loop %arg0 = %11 to %12 step %c1 {
      %20 = fir.convert %arg0 : (index) -> i32
      fir.store %20 to %3 : !fir.ref<i32>
      %21 = fir.call @_QMmPmakedata(%3) proc_attrs<pure> fastmath<contract> : (!fir.ref<i32>) -> !fir.box<!fir.ptr<f32>>
      fir.save_result %21 to %4 : !fir.box<!fir.ptr<f32>>, !fir.ref<!fir.box<!fir.ptr<f32>>>
      %22 = fir.declare %4 {uniq_name = ".tmp.func_result"} : (!fir.ref<!fir.box<!fir.ptr<f32>>>) -> !fir.ref<!fir.box<!fir.ptr<f32>>>
      %23 = fir.load %22 : !fir.ref<!fir.box<!fir.ptr<f32>>>
      %24 = fir.box_addr %23 : (!fir.box<!fir.ptr<f32>>) -> !fir.ptr<f32>
      %25 = fir.embox %24 : (!fir.ptr<f32>) -> !fir.box<f32>                         !!! Seems the error
      %26 = fir.convert %25 : (!fir.box<f32>) -> !fir.box<none>
      fir.call @_FortranAPushDescriptor(%15, %26) : (!fir.llvm_ptr<i8>, !fir.box<none>) -> ()
    }

The embox seems "lost" the POINTER attribute, which caused IR to be

  %20 = insertvalue { ptr, i64, i32, i8, i8, i8, i8 } { ptr undef, i64 4, i32 20240719, i8 0, i8 27, i8 0, i8 0 }, ptr %19, 0

where the isAllocatable flag set by the function result is lost.

The desired code should be %25 = fir.embox %24 : (!fir.ptr<f32>) -> !fir.box<!fir.ptr<f32>>, then the IR will look like:

%21 = insertvalue { ptr, i64, i32, i8, i8, i8, i8 } { ptr undef, i64 4, i32 20240719, i8 0, i8 27, i8 1, i8 0 }, ptr %20, 0

[DanielCChen]

Actually, the RHS of the function call to makeData is already a box. There is no need to converToBox again.
I will post a PR with this fix.