[clang] [OpenMP 6.0] Parse/Sema support for reduction over private variable with reduction clause. (PR #129938)

[Alexey Bataev via cfe-commits]

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@@ -18933,12 +18945,35 @@ static bool actOnOMPReductionKindClause(
         reportOriginalDsa(S, Stack, D, DVar);
         continue;
       }
+      // OpenMP 6.0 [ 7.6.10 ]
+      // Support Reduction over private variables with reduction clause.
+      // A list item in a reduction clause can now be private in the enclosing
+      // context. For orphaned constructs it is assumed to be shared unless the
+      // original(private) modifier appears in the clause.
+      DVar = Stack->getImplicitDSA(D, true);
+      bool IsOrphaned = false;
+      OpenMPDirectiveKind CurrDir = Stack->getCurrentDirective();
+      OpenMPDirectiveKind ParentDir = Stack->getParentDirective();
+      // Check if the construct is orphaned (has no enclosing OpenMP context)
+      IsOrphaned = (ParentDir == OMPD_unknown);
+      IsPrivate =
+          ((isOpenMPPrivate(DVar.CKind) && DVar.CKind != OMPC_reduction &&
+            isOpenMPWorksharingDirective(CurrDir) &&
+            !isOpenMPParallelDirective(CurrDir) &&
+            !isOpenMPTeamsDirective(CurrDir) &&
+            !isOpenMPSimdDirective(ParentDir)) ||
+           (IsOrphaned && DVar.CKind == OMPC_unknown) ||
+           RD.OrigSharingModifier != OMPC_ORIGINAL_SHARING_shared);
+      // Disable private handling for OpenMP versions <= 5.2
+      if (S.getLangOpts().OpenMP <= 52)
+        IsPrivate = false;
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alexey-bataev wrote:

Shall it report an error, if DSA is private for version <= 52? If so, it should not change the value of IsPrivate here, instead it shall return IsPrivate or, if it cannot be private at all, add an assertion.

https://github.com/llvm/llvm-project/pull/129938