[llvm] [clang-tools-extra] [clang] [OpenMP] atomic compare weak : Parser & AST support (PR #79475)

[Alexey Bataev via cfe-commits]

================
@@ -13202,6 +13204,29 @@ StmtResult Sema::ActOnOpenMPAtomicDirective(ArrayRef<OMPClause *> Clauses,
       E = Checker.getE();
       D = Checker.getD();
       CE = Checker.getCond();
+      /* The weak clause may only appear if the resulting atomic operation is
+       * an atomic conditional update for which the comparison tests for
+       * equality.
+       * It was not possible to do this check in
+       * OpenMPAtomicCompareChecker::checkStmt() as the check for OMPC_weak
+       * could not be performed (Clauses are not available).
+       */
+      for (OMPClause *C : Clauses) {
+        if (C->getClauseKind() == llvm::omp::Clause::OMPC_weak) {
+          auto *Cond = dyn_cast<BinaryOperator>(CE);
+          if (Cond->getOpcode() != BO_EQ) {
+
+            ErrorInfo.Error = Checker.ErrorTy::NotAnAssignment;
+            ErrorInfo.ErrorLoc = Cond->getExprLoc();
+            ErrorInfo.NoteLoc = Cond->getOperatorLoc();
+            ErrorInfo.ErrorRange = ErrorInfo.NoteRange = Cond->getSourceRange();
+
+            Diag(ErrorInfo.ErrorLoc, diag::err_omp_atomic_weak_no_equality)
+                << ErrorInfo.ErrorRange;
+            return StmtError();
+          }
+        }
+      }
----------------
alexey-bataev wrote:

```suggestion
      auto *It = find_if(Clauses, [](OMPClause *C) { return C->getClauseKind() == llvm::omp::Clause::OMPC_weak; });
      if (It != Clauses.end()) {
        auto *Cond = dyn_cast<BinaryOperator>(CE);
        if (Cond->getOpcode() != BO_EQ) {
          ErrorInfo.Error = Checker.ErrorTy::NotAnAssignment;
          ErrorInfo.ErrorLoc = Cond->getExprLoc();
          ErrorInfo.NoteLoc = Cond->getOperatorLoc();
          ErrorInfo.ErrorRange = ErrorInfo.NoteRange = Cond->getSourceRange();

          Diag(ErrorInfo.ErrorLoc, diag::err_omp_atomic_weak_no_equality)
              << ErrorInfo.ErrorRange;
          return StmtError();
        }
      }
```


https://github.com/llvm/llvm-project/pull/79475