flang/test/Lower/OpenMP/private-array-boxing.f90

! Test the array boxing decision made when privatizing a symbol for an OpenMP
! data-sharing clause (privatizeSymbol in flang/lib/Lower/Support/Utils.cpp).
!
! A constant-shape array of trivial intrinsic elements is privatized *unboxed*
! (as a plain fir.array), so the OpenMP-to-LLVMIR translation can allocate it
! directly on the stack and no per-thread heap allocation / descriptor is
! needed. Arrays that cannot be handled that way -- character arrays,
! dynamic-extent arrays, firstprivate arrays (which need a copy region), and
! arrays with non-default lower bounds (whose HLFIR variable is a box that
! carries the lower bounds) -- keep being boxed.

! RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - | FileCheck %s

subroutine test_private_array_boxing(n)
  integer :: n, i
  real(8) :: trivial_const(3)
  character(4) :: char_arr(2)
  real(8) :: dyn_arr(n)
  real(8) :: first_const(3)
  real(8) :: nondef_lb(0:2)
  first_const = 1.0d0
!$omp parallel do private(trivial_const, char_arr, dyn_arr, nondef_lb) firstprivate(first_const)
  do i = 1, n
     trivial_const = 1.0d0
     char_arr = "abcd"
     dyn_arr = 1.0d0
     nondef_lb = 1.0d0
  end do
end subroutine

! A constant-shape array of trivial elements is privatized unboxed. The trailing
! end-of-line anchor checks there is no `init {` region on this privatizer, i.e.
! no per-thread initialization / heap allocation is generated for it:
! CHECK-DAG: omp.private {type = private} @{{.*}}Etrivial_const_private_3xf64 : !fir.array<3xf64>{{$}}

! A character array is boxed (character is not a trivial element type):
! CHECK-DAG: omp.private {type = private} @{{.*}}Echar_arr_private_box{{.*}} : !fir.box<!fir.array<2x!fir.char<1,4>>>

! A dynamic-extent array is boxed:
! CHECK-DAG: omp.private {type = private} @{{.*}}Edyn_arr_private_box{{.*}} : !fir.box<!fir.array<?xf64>>

! A firstprivate array is boxed (it needs the copy region):
! CHECK-DAG: omp.private {type = firstprivate} @{{.*}}Efirst_const_firstprivate_box_3xf64 : !fir.box<!fir.array<3xf64>>

! A constant-shape array with non-default lower bounds is boxed: its HLFIR
! variable is a fir.box (which carries the lower bounds), so the constant-array
! unboxing carve-out does not apply:
! CHECK-DAG: omp.private {type = private} @{{.*}}Enondef_lb_private_box_3xf64 : !fir.box<!fir.array<3xf64>>