[flang-commits] [flang] [flang][hlfir] Fixed some finalization/deallocation issues. (PR #67047)

[Slava Zakharin via flang-commits]

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@@ -439,8 +440,20 @@ static bool allOtherUsesAreSafeForAssociate(mlir::Value value,
        value.getParentRegion() != endAssociate->getParentRegion()))
     return false;
 
-  for (mlir::Operation *useOp : value.getUsers())
-    if (!mlir::isa<hlfir::DestroyOp>(useOp) && useOp != currentUse) {
+  for (mlir::Operation *useOp : value.getUsers()) {
+    // Ignore DestroyOp's that do not imply finalization.
+    // If finalization is implied, then we must delegate
+    // the finalization to the correspoding EndAssociateOp,
+    // but we currently do not; so we disable the buffer
+    // reuse in this case.
+    if (auto destroy = mlir::dyn_cast<hlfir::DestroyOp>(useOp)) {
+      if (destroy.mustFinalizeExpr())
+        return false;
----------------
vzakhari wrote:

I agree!  I think we will need `finalize` attribute for `hlfir.end_associate` to communicate the "theft" of the buffer that needs finalization.

I also agree that we have to be careful about stealing the buffer from the elemental op, when the buffer might be modified inside the association scope, e.g.:
```
module types
  type t
     integer :: i
   contains
     final :: finalize
  end type t
contains
  subroutine finalize(x)
    type(t), intent(inout) :: x
    print *, x%i
  end subroutine finalize
end module types
subroutine test(x)
  use types
  type(t) :: x(10)
  call callee(elem(x))
contains
  subroutine callee(x)
    type(t), value :: x(10)
    x%i = 10
  end subroutine callee
  impure elemental function elem(x)
    type(t), intent(in) :: x
    type(t) :: elem
    elem = x
  end function elem
end subroutine test
```

Since the `callee` might modify the buffer, the modification can be made visible via an impure finalization routine.  I guess it may only be the case for impure elemental calls, so we can probably rely on the `unordered` attribute to decide if it is safe to steal the buffer.

https://github.com/llvm/llvm-project/pull/67047