[Flang] Incorrect execution result of using polymorphic variable in select type construct

[ohno-fj]

Version of flang : 21.0.0(ebba554a3211b0b98d3ae33ba70f9d6ceaab6ad4)/AArch64

In the attached program, variable (p) is the return value of function (ufun).
It is a polymorphic variable that can be of either derived type (obj3) or integer type (obj), but it looks like the wrong behavior in select type construct.
type is (integer) in select type construct is not executed.
The above program is sngg457k_22.f90.

The result is correct if the return value of function (ufun) is specified directly:

• Before modification

     p=ufun(n)
     select type(b=>p)

• After modification

     select type(b=>ufun(n))

The above program is sngg457k_23.f90.

The following are the test program, Flang, Gfortran and ifx compilation/execution result.

sngg457k_22.f90:

program main
  type  ty
     integer :: ii
  end type ty
  type ,extends(ty) :: ty1
     integer :: jj
  end type ty1

  type(ty1),target:: obj3
  integer,target:: obj
  class(*),allocatable::p

  do n=0,1
     print*,"n=",n
     p=ufun(n)
     select type(b=>p)
     type  is (ty1)
        write(6,*) "b%ii = ", b%ii, " b%jj = ", b%jj
     type  is (integer)
        write(6,*) "obj = ", obj
     end select
  end do
  print*,"pass"
contains
  function ufun(n)
    class(*),pointer :: ufun
    obj3%ii=1
    obj3%jj=10
    obj=100
    select case(n)
    case(0)
       ufun=>obj3
    case(1)
       ufun=>obj
    end select
  end function ufun
end program main

$ flang sngg457k_22.f90; ./a.out
 n= 0
 b%ii =  1  b%jj =  10
 n= 1
 b%ii =  100  b%jj =  0
 pass
$

$ gfortran sngg457k_22.f90; ./a.out
 n=           0
 b%ii =            1  b%jj =           10
 n=           1
 obj =          100
 pass
$

$ ifx sngg457k_22.f90; ./a.out
 n=           0
 b%ii =            1  b%jj =           10
 n=           1
 obj =          100
 pass
$

sngg457k_23.f90:

program main
  type  ty
     integer :: ii
  end type ty
  type ,extends(ty) :: ty1
     integer :: jj
  end type ty1

  type(ty1),target:: obj3
  integer,target:: obj
  class(*),allocatable::p

  do n=0,1
     print*,"n=",n
!     p=ufun(n)
!     select type(b=>p)
     select type(b=>ufun(n))
     type  is (ty1)
        write(6,*) "b%ii = ", b%ii, " b%jj = ", b%jj
     type  is (integer)
        write(6,*) "obj = ", obj
     end select
  end do
  print*,"pass"
contains
  function ufun(n)
    class(*),pointer :: ufun
    obj3%ii=1
    obj3%jj=10
    obj=100
    select case(n)
    case(0)
       ufun=>obj3
    case(1)
       ufun=>obj
    end select
  end function ufun
end program main

$ flang sngg457k_23.f90; ./a.out
 n= 0
 b%ii =  1  b%jj =  10
 n= 1
 obj =  100
 pass
$

[llvmbot]

@llvm/issue-subscribers-flang-runtime

Author: None (ohno-fj)

``` Version of flang : 21.0.0(ebba554)/AArch64 ```

In the attached program, variable (p) is the return value of function (ufun).
It is a polymorphic variable that can be of either derived type (obj3) or integer type (obj), but it looks like the wrong behavior in select type construct.
type is (integer) in select type construct is not executed.
The above program is sngg457k_22.f90.

The result is correct if the return value of function (ufun) is specified directly:

• Before modification

     p=ufun(n)
     select type(b=>p)

• After modification

     select type(b=>ufun(n))

The above program is sngg457k_23.f90.

The following are the test program, Flang, Gfortran and ifx compilation/execution result.

sngg457k_22.f90:

program main
  type  ty
     integer :: ii
  end type ty
  type ,extends(ty) :: ty1
     integer :: jj
  end type ty1

  type(ty1),target:: obj3
  integer,target:: obj
  class(*),allocatable::p

  do n=0,1
     print*,"n=",n
     p=ufun(n)
     select type(b=>p)
     type  is (ty1)
        write(6,*) "b%ii = ", b%ii, " b%jj = ", b%jj
     type  is (integer)
        write(6,*) "obj = ", obj
     end select
  end do
  print*,"pass"
contains
  function ufun(n)
    class(*),pointer :: ufun
    obj3%ii=1
    obj3%jj=10
    obj=100
    select case(n)
    case(0)
       ufun=>obj3
    case(1)
       ufun=>obj
    end select
  end function ufun
end program main

$ flang sngg457k_22.f90; ./a.out
 n= 0
 b%ii =  1  b%jj =  10
 n= 1
 b%ii =  100  b%jj =  0
 pass
$

$ gfortran sngg457k_22.f90; ./a.out
 n=           0
 b%ii =            1  b%jj =           10
 n=           1
 obj =          100
 pass
$

$ ifx sngg457k_22.f90; ./a.out
 n=           0
 b%ii =            1  b%jj =           10
 n=           1
 obj =          100
 pass
$

sngg457k_23.f90:

program main
  type  ty
     integer :: ii
  end type ty
  type ,extends(ty) :: ty1
     integer :: jj
  end type ty1

  type(ty1),target:: obj3
  integer,target:: obj
  class(*),allocatable::p

  do n=0,1
     print*,"n=",n
!     p=ufun(n)
!     select type(b=>p)
     select type(b=>ufun(n))
     type  is (ty1)
        write(6,*) "b%ii = ", b%ii, " b%jj = ", b%jj
     type  is (integer)
        write(6,*) "obj = ", obj
     end select
  end do
  print*,"pass"
contains
  function ufun(n)
    class(*),pointer :: ufun
    obj3%ii=1
    obj3%jj=10
    obj=100
    select case(n)
    case(0)
       ufun=>obj3
    case(1)
       ufun=>obj
    end select
  end function ufun
end program main

$ flang sngg457k_23.f90; ./a.out
 n= 0
 b%ii =  1  b%jj =  10
 n= 1
 obj =  100
 pass
$