[flang-commits] [flang] [flang][OpenMP] Implement collapse for imperfectly nested loops (PR #202435)

[Krzysztof Parzyszek via flang-commits]

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@@ -326,6 +369,13 @@ void OmpStructureChecker::CheckNestedConstruct(
     // Check requirements on nest depth.
     auto [needDepth, needPerfect]{
         GetAffectedNestDepthWithReason(beginSpec, version)};
+
+    // In OpenMP 5.2+, perfect nesting is only required for doacross loop
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kparzysz wrote:

I believe the restrictions are as follows:
- 5.0: loop nest with an **ordered** clause must be a perfect nest
- 5.1: loop nest with an **ordered** clause must be a perfect nest if the **ordered** clause has an explicit argument
- 5.2: same as 5.1
- 6.0: loop nest with an **ordered** clause must be a perfect nest if the body contains an **ordered** directive with a **doacross** clause.

https://github.com/llvm/llvm-project/pull/202435