[flang][OpenMP][debug] Invalid debug info for variable size string in target region.

[abidh]

For variable size arrays, flang generates an artificial variable in the debug info that holds the length. I noticed that variable inside the target region are using the artificial variable in the host for the length which is not working. As a result, the evaluation fails. The problem could be reproduced with the following program.

subroutine fn(b, c)
  integer c
  integer b(c, 20)
  b = 2

  !$omp target map(tofrom:b)
    b(1, 1) = 3
  !$omp end target
end subroutine fn


program main
  integer a(10, 20)
  call fn(a, 10)
  print *, a
end program

Run to line inside the target region and check the type of the b and you will see that it is not correct. I guess similar issue will exist with variable strings.

[llvmbot]

@llvm/issue-subscribers-flang-ir

Author: Abid Qadeer (abidh)

For variable size strings, flang generates an artificial variable in the debug info that holds the length. While reviewing https://github.com//pull/134967, I noticed that variable inside the target region are using the artificial variable in the host for the length which is not working. As a result, the evaluation fails. The problem could be reproduced with the following program but it will need the changes in #134967 to compile.

module test
  implicit none

  contains

  subroutine TestOfCharacter(a0, a1, l)
    character(len=*), intent(in) :: a0
    character(len=*), intent(inout):: a1
    integer, intent(in) :: l

    !$omp target map(to:a0) map(from: a1)
      a1 = a0
    !$omp end target

  end subroutine TestOfCharacter
end module test

program main
  use test
  character(len=15) :: first
  character(len=:), allocatable :: second
  first = 'Short string'
  second='This is a large string.'
  call TestOfCharacter(first, second, 23)
  print *, first
  print *, second
end program

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Abid Qadeer (abidh)

For variable size strings, flang generates an artificial variable in the debug info that holds the length. While reviewing https://github.com//pull/134967, I noticed that variable inside the target region are using the artificial variable in the host for the length which is not working. As a result, the evaluation fails. The problem could be reproduced with the following program but it will need the changes in #134967 to compile.

module test
  implicit none

  contains

  subroutine TestOfCharacter(a0, a1, l)
    character(len=*), intent(in) :: a0
    character(len=*), intent(inout):: a1
    integer, intent(in) :: l

    !$omp target map(to:a0) map(from: a1)
      a1 = a0
    !$omp end target

  end subroutine TestOfCharacter
end module test

program main
  use test
  character(len=15) :: first
  character(len=:), allocatable :: second
  first = 'Short string'
  second='This is a large string.'
  call TestOfCharacter(first, second, 23)
  print *, first
  print *, second
end program

[abidh]

This was fixed by #146532.