[flang][OpenMP] Guard lastprivate scoping on DO

[KrxGu]

Add HLFIR FileCheck ensuring lastprivate(v) on an omp do is realized
as privatization on the inner wsloop and not on the enclosing omp parallel.
This matches OpenMP semantics and prevents regressions.

• No private(v) at omp.parallel
• omp.wsloop ... private(...) present

Unable to reproduce #157035 on current main; this test documents the
expected lowering.

p.s- do refer to delayed-privatization

[github-actions]

Thank you for submitting a Pull Request (PR) to the LLVM Project!

This PR will be automatically labeled and the relevant teams will be notified.

If you wish to, you can add reviewers by using the "Reviewers" section on this page.

If this is not working for you, it is probably because you do not have write permissions for the repository. In which case you can instead tag reviewers by name in a comment by using @ followed by their GitHub username.

If you have received no comments on your PR for a week, you can request a review by "ping"ing the PR by adding a comment “Ping”. The common courtesy "ping" rate is once a week. Please remember that you are asking for valuable time from other developers.

If you have further questions, they may be answered by the LLVM GitHub User Guide.

You can also ask questions in a comment on this PR, on the LLVM Discord or on the forums.

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

@llvm/pr-subscribers-flang-openmp

Author: Krish Gupta (KrxGu)

Changes

Add HLFIR FileCheck ensuring lastprivate(v) on an omp do is realized
as privatization on the inner wsloop and not on the enclosing omp parallel.
This matches OpenMP semantics and prevents regressions.

• No private(v) at omp.parallel
• omp.wsloop ... private(...) present

Unable to reproduce #157035 on current main; this test documents the
expected lowering.
Fixes #157035.

p.s- do refer to delayed-privatization

<img width="2940" height="1912" alt="image" src="https://github.com/user-attachments/assets/5c3a0656-fe0a-4bd5-be98-b626a7a719c1" />

---

Full diff: https://github.com/llvm/llvm-project/pull/157760.diff

1 Files Affected:

• (added) flang/test/Lower/OpenMP/lastprivate-alloc-scope.f90 (+22)

diff --git a/flang/test/Lower/OpenMP/lastprivate-alloc-scope.f90 b/flang/test/Lower/OpenMP/lastprivate-alloc-scope.f90
new file mode 100644
index 0000000000000..67d885ed5fb7a
--- /dev/null
+++ b/flang/test/Lower/OpenMP/lastprivate-alloc-scope.f90
@@ -0,0 +1,22 @@
+! RUN: %flang_fc1 -fopenmp -emit-hlfir %s -o - | FileCheck %s
+
+program p
+  type y3; integer, allocatable :: x; end type
+  type(y3) :: v
+  integer :: s, n, i
+  s = 1; n = 10
+  allocate(v%x); v%x = 0
+!$omp parallel
+  if (.not. allocated(v%x)) print *, '101', allocated(v%x)
+!$omp do schedule(dynamic) lastprivate(v)
+  do i = s, n
+    v%x = i
+  end do
+!$omp end do
+!$omp end parallel
+end program
+
+! CHECK:      omp.parallel {
+! CHECK-NOT:  private(
+! CHECK:      omp.wsloop
+! CHECK-SAME: private(

[tblah]

Thank you for contributing this test. Please could you remove the fixes tag for the issue, as I don't think this will resolve it.

Are you sure this case isn't covered in an existing test?

[KrxGu]

Thank you for contributing this test. Please could you remove the fixes tag for the issue, as I don't think this will resolve it.

Are you sure this case isn't covered in an existing test?

Removed Fixes tag from the PR description, to the best of my knowledge i don't think this test was covered .
P.s- I am new to the org so might have missed something

[tblah]

I can't see something equivalent in the lowering tests either, and the test does not look like it would be burdensome to maintain. Thanks for your contribution.

Let me know if you need help merging it.

[KrxGu]

I can't see something equivalent in the lowering tests either, and the test does not look like it would be burdensome to maintain. Thanks for your contribution.

Let me know if you need help merging it.

CI all green , good to merge (i don't have merge rights)

[github-actions]

@KrxGu Congratulations on having your first Pull Request (PR) merged into the LLVM Project!

Your changes will be combined with recent changes from other authors, then tested by our build bots. If there is a problem with a build, you may receive a report in an email or a comment on this PR.

Please check whether problems have been caused by your change specifically, as the builds can include changes from many authors. It is not uncommon for your change to be included in a build that fails due to someone else's changes, or infrastructure issues.

How to do this, and the rest of the post-merge process, is covered in detail here.

If your change does cause a problem, it may be reverted, or you can revert it yourself. This is a normal part of LLVM development. You can fix your changes and open a new PR to merge them again.

If you don't get any reports, no action is required from you. Your changes are working as expected, well done!