Add TODO for unstructured in kernels

Author: Razvan Lupusoru

flang/lib/Lower/OpenACC.cpp

@@ -5018,9 +5018,18 @@ mlir::Operation *Fortran::lower::genOpenACCLoopFromDoConstruct(
   // TODO: There may be other strategies that can be employed such
   // as generating acc.private for the loop variables without attaching
   // them to acc.loop.
-  if (eval.lowerAsUnstructured())
-    TODO(converter.getCurrentLocation(),
-         "unstructured do loops in acc regions");
+  // For now - generate a not-yet-implemented message because without
+  // privatizing the induction variable, the loop may not execute correctly.
+  // Only do this for `acc kernels` because in `acc parallel`, scalars end
+  // up as implicitly firstprivate.
+  if (eval.lowerAsUnstructured()) {
+    if (mlir::isa_and_present<mlir::acc::KernelsOp>(
+            mlir::acc::getEnclosingComputeOp(
+                converter.getFirOpBuilder().getRegion())))
+      TODO(converter.getCurrentLocation(),
+           "unstructured do loop in acc kernels");
+    return nullptr;
+  }
 
   // Open up a new scope for the loop variables.
   localSymbols.pushScope();

flang/test/Lower/OpenACC/Todo/do-loops-to-acc-loops-todo.f90

@@ -0,0 +1,91 @@
+! RUN: split-file %s %t
+! RUN: %not_todo_cmd bbc -fopenacc -emit-hlfir %t/do_loop_with_stop.f90 -o - 2>&1 | FileCheck %s --check-prefix=CHECK1
+! RUN: %not_todo_cmd bbc -fopenacc -emit-hlfir %t/do_loop_with_cycle_goto.f90 -o - 2>&1 | FileCheck %s --check-prefix=CHECK2
+! RUN: %not_todo_cmd bbc -fopenacc -emit-hlfir %t/nested_goto_loop.f90 -o - 2>&1 | FileCheck %s --check-prefix=CHECK3
+! RUN: %not_todo_cmd bbc -fopenacc -emit-hlfir %t/nested_loop_with_inner_goto.f90 -o - 2>&1 | FileCheck %s --check-prefix=CHECK4
+
+//--- do_loop_with_stop.f90
+
+subroutine do_loop_with_stop()
+  integer :: i
+  integer, parameter :: n = 10
+  real, dimension(n) :: a, b
+
+  !$acc kernels
+  do i = 1, n
+    a(i) = b(i) + 1.0
+    if (i == 5) stop
+  end do
+  !$acc end kernels
+
+! CHECK1: not yet implemented: unstructured do loop in acc kernels
+
+end subroutine
+
+//--- do_loop_with_cycle_goto.f90
+
+subroutine do_loop_with_cycle_goto()
+  integer :: i
+  integer, parameter :: n = 10
+  real, dimension(n) :: a, b
+
+  ! Do loop with cycle and goto - unstructured control flow is not converted.
+  !$acc kernels
+  do i = 1, n
+    if (i == 3) cycle
+    a(i) = b(i) + 1.0
+    if (i == 7) goto 200
+    a(i) = a(i) * 2.0
+  end do
+200 continue
+  !$acc end kernels
+
+! CHECK2: not yet implemented: unstructured do loop in acc kernels
+
+end subroutine
+
+//--- nested_goto_loop.f90
+
+subroutine nested_goto_loop()
+  integer :: i, j
+  integer, parameter :: n = 10, m = 5
+  real, dimension(n,m) :: a, b
+
+  ! Nested loop with goto from inner to outer - should NOT convert to acc.loop
+  !$acc kernels
+  do i = 1, n
+    do j = 1, m
+      a(i,j) = b(i,j) + 1.0
+      if (i * j > 20) goto 300  ! Exit both loops
+    end do
+  end do
+300 continue
+  !$acc end kernels
+
+! CHECK3: not yet implemented: unstructured do loop in acc kernels
+
+end subroutine
+
+//--- nested_loop_with_inner_goto.f90
+
+subroutine nested_loop_with_inner_goto()
+  integer :: ii = 0, jj = 0
+  integer, parameter :: nn = 3
+  real, dimension(nn, nn) :: aa
+  
+  aa = -1
+  
+  ! Nested loop with goto from inner loop - unstructured control flow is not converted.
+  !$acc kernels
+  do ii = 1, nn
+    do jj = 1, nn
+      if (jj > 1) goto 300
+      aa(jj, ii) = 1337
+    end do
+    300 continue
+  end do
+  !$acc end kernels
+
+! CHECK4: not yet implemented: unstructured do loop in acc kernels
+
+end subroutine

flang/test/Lower/OpenACC/do-loops-to-acc-loops.f90

@@ -245,71 +245,6 @@ subroutine infinite_loop_no_iv()
 
 end subroutine
 
-! CHECK-LABEL: func.func @_QPdo_loop_with_goto
-subroutine do_loop_with_goto()
-  integer :: i
-  integer, parameter :: n = 10
-  real, dimension(n) :: a, b
-
-  ! Do loop with goto - unstructured control flow is not converted.
-  !$acc kernels
-  do i = 1, n
-    a(i) = b(i) + 1.0
-    if (i == 5) goto 100
-    100 continue
-  end do
-  !$acc end kernels
-
-! CHECK: acc.kernels {
-! CHECK-NOT: acc.loop
-
-end subroutine
-
-
-! CHECK-LABEL: func.func @_QPdo_loop_with_cycle_goto
-subroutine do_loop_with_cycle_goto()
-  integer :: i
-  integer, parameter :: n = 10
-  real, dimension(n) :: a, b
-
-  ! Do loop with cycle and goto - unstructured control flow is not converted.
-  !$acc kernels
-  do i = 1, n
-    if (i == 3) cycle
-    a(i) = b(i) + 1.0
-    if (i == 7) goto 200
-    a(i) = a(i) * 2.0
-  end do
-200 continue
-  !$acc end kernels
-
-! CHECK: acc.kernels {
-! CHECK-NOT: acc.loop
-
-end subroutine
-
-! CHECK-LABEL: func.func @_QPnested_goto_loop
-subroutine nested_goto_loop()
-  integer :: i, j
-  integer, parameter :: n = 10, m = 5
-  real, dimension(n,m) :: a, b
-
-  ! Nested loop with goto from inner to outer - should NOT convert to acc.loop
-  !$acc kernels
-  do i = 1, n
-    do j = 1, m
-      a(i,j) = b(i,j) + 1.0
-      if (i * j > 20) goto 300  ! Exit both loops
-    end do
-  end do
-300 continue
-  !$acc end kernels
-
-! CHECK: acc.kernels {
-! CHECK-NOT: acc.loop
-
-end subroutine
-
 ! CHECK-LABEL: func.func @_QPwhile_like_loop
 subroutine while_like_loop()
   integer :: i