[flang-commits] [flang] [Flang][OpenMP] Add OpenMP standards support doc (PR #132707)

[Michael Klemm via flang-commits]

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+<!--===- docs/FortranStandardsSupport.md
+
+   Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+   See https://llvm.org/LICENSE.txt for license information.
+   SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+-->
+
+# Flang OpenMP Standards Support
+
+```{contents}
+---
+local:
+---
+```
+
+This document summarizes OpenMP standards support in Flang. The information is only provided as a guideline. The
+TODOs/Not Yet Implemented messages emitted by the compiler for unimplemented features should be treated as authoritative.
+As of March 2025, standards support is provided upto OpenMP 4.0. We are actively working towards supporting OpenMP 4.5, OpenMP 5.* and OpenMP 6.0.
+
+The standards support information is provided as a table with three columns that are self explanatory. The Status column uses
+the letters **P**, **Y**, **N** for the implementation status:
+- **P** : When the implementation is incomplete for a few cases
+- **Y** : When the implementation is complete
+- **N** : When the implementation is absent
+
+Note : No distinction is made between the support in Parser/Semantics, MLIR, Lowering or the OpenMPIRBuilder.
+
+## OpenMP 4.0
+
+| Feature                                                    | Status | Comments                                                |
+|------------------------------------------------------------|--------|---------------------------------------------------------|
+| proc_bind clause                                           | Y      | |
+| simd construct                                             | P      | Some clauses are not supported |
+| declare simd construct                                     | N      | |
+| do simd construct                                          | Y      | |
+| target data construct                                      | P      | |
+| target construct                                           | P      | |
+| target update construct                                    | P      | |
+| declare target directive                                   | P      | |
+| teams construct                                            | P      | |
+| distribute construct                                       | P      | |
+| distribute simd construct                                  | P      | |
+| distribute parallel loop construct                         | P      | |
+| distribute parallel loop simd construct                    | P      | |
+| depend clause                                              | P      | Depend clause with array sections are not supported |
+| declare reduction construct                                | N      | |
+| atomic construct extensions                                | Y      | |
+| cancel construct                                           | N      | |
+| cancellation point construct                               | N      | |
+| parallel do simd construct                                 | Y      | |
+| target teams construct                                     | P      | |
+| teams distribute construct                                 | P      | |
+| teams distribute simd construct                            | P      | |
+| target teams distribute construct                          | P      | |
+| teams distribute parallel loop construct                   | P      | |
+| target teams distribute parallel loop construct            | P      | |
+| teams distribute parallel loop simd construct              | P      | |
+| target teams distribute parallel loop simd construct       | P      | |
+
+## OpenMP 3.1, OpenMP 2.5, OpenMP 1.1
+All features except a few corner cases in atomic, copyin constructs/clauses are supported 
----------------
mjklemm wrote:

Should these corner cases be made explicit?

https://github.com/llvm/llvm-project/pull/132707