diff --git a/clang/include/clang/AST/OpenMPClause.h b/clang/include/clang/AST/OpenMPClause.h
--- a/clang/include/clang/AST/OpenMPClause.h
+++ b/clang/include/clang/AST/OpenMPClause.h
@@ -2224,6 +2224,47 @@
   }
 };
 
+/// This represents 'compare' clause in the '#pragma omp atomic'
+/// directive.
+///
+/// \code
+/// #pragma omp atomic compare
+/// \endcode
+/// In this example directive '#pragma omp atomic' has 'compare' clause.
+class OMPCompareClause : public OMPClause {
+public:
+  /// Build 'compare' clause.
+  ///
+  /// \param StartLoc Starting location of the clause.
+  /// \param EndLoc Ending location of the clause.
+  OMPCompareClause(SourceLocation StartLoc, SourceLocation EndLoc)
+      : OMPClause(llvm::omp::OMPC_compare, StartLoc, EndLoc) {}
+
+  /// Build an empty clause.
+  OMPCompareClause()
+      : OMPClause(llvm::omp::OMPC_compare, SourceLocation(), SourceLocation()) {
+  }
+
+  child_range children() {
+    return child_range(child_iterator(), child_iterator());
+  }
+
+  const_child_range children() const {
+    return const_child_range(const_child_iterator(), const_child_iterator());
+  }
+
+  child_range used_children() {
+    return child_range(child_iterator(), child_iterator());
+  }
+  const_child_range used_children() const {
+    return const_child_range(const_child_iterator(), const_child_iterator());
+  }
+
+  static bool classof(const OMPClause *T) {
+    return T->getClauseKind() == llvm::omp::OMPC_compare;
+  }
+};
+
 /// This represents 'seq_cst' clause in the '#pragma omp atomic'
 /// directive.
 ///
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -3226,6 +3226,11 @@
   return true;
 }
 
+template <typename Derived>
+bool RecursiveASTVisitor<Derived>::VisitOMPCompareClause(OMPCompareClause *) {
+  return true;
+}
+
 template <typename Derived>
 bool RecursiveASTVisitor<Derived>::VisitOMPSeqCstClause(OMPSeqCstClause *) {
   return true;
diff --git a/clang/include/clang/AST/StmtOpenMP.h b/clang/include/clang/AST/StmtOpenMP.h
--- a/clang/include/clang/AST/StmtOpenMP.h
+++ b/clang/include/clang/AST/StmtOpenMP.h
@@ -2858,25 +2858,20 @@
       : OMPExecutableDirective(OMPAtomicDirectiveClass, llvm::omp::OMPD_atomic,
                                SourceLocation(), SourceLocation()) {}
 
-  enum DataPositionTy : size_t {
-    POS_X = 0,
-    POS_V,
-    POS_E,
-    POS_UpdateExpr,
-  };
+  enum DataPositionTy : size_t { POS_X = 0, POS_V, POS_E, POS_UpdateExpr };
 
   /// Set 'x' part of the associated expression/statement.
   void setX(Expr *X) { Data->getChildren()[DataPositionTy::POS_X] = X; }
+  /// Set 'v' part of the associated expression/statement.
+  void setV(Expr *V) { Data->getChildren()[DataPositionTy::POS_V] = V; }
+  /// Set 'e' or 'expr' part of the associated expression/statement.
+  void setE(Expr *E) { Data->getChildren()[DataPositionTy::POS_E] = E; }
   /// Set helper expression of the form
   /// 'OpaqueValueExpr(x) binop OpaqueValueExpr(expr)' or
   /// 'OpaqueValueExpr(expr) binop OpaqueValueExpr(x)'.
   void setUpdateExpr(Expr *UE) {
     Data->getChildren()[DataPositionTy::POS_UpdateExpr] = UE;
   }
-  /// Set 'v' part of the associated expression/statement.
-  void setV(Expr *V) { Data->getChildren()[DataPositionTy::POS_V] = V; }
-  /// Set 'expr' part of the associated expression/statement.
-  void setExpr(Expr *E) { Data->getChildren()[DataPositionTy::POS_E] = E; }
 
 public:
   /// Creates directive with a list of \a Clauses and 'x', 'v' and 'expr'
@@ -2919,6 +2914,20 @@
   const Expr *getX() const {
     return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_X]);
   }
+  /// Get 'e' part of the associated expression/statement.
+  Expr *getE() {
+    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_E]);
+  }
+  const Expr *getE() const {
+    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_E]);
+  }
+  /// Get 'v' part of the associated expression/statement.
+  Expr *getV() {
+    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_V]);
+  }
+  const Expr *getV() const {
+    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_V]);
+  }
   /// Get helper expression of the form
   /// 'OpaqueValueExpr(x) binop OpaqueValueExpr(expr)' or
   /// 'OpaqueValueExpr(expr) binop OpaqueValueExpr(x)'.
@@ -2937,20 +2946,6 @@
   /// Return true if 'v' expression must be updated to original value of
   /// 'x', false if 'v' must be updated to the new value of 'x'.
   bool isPostfixUpdate() const { return IsPostfixUpdate; }
-  /// Get 'v' part of the associated expression/statement.
-  Expr *getV() {
-    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_V]);
-  }
-  const Expr *getV() const {
-    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_V]);
-  }
-  /// Get 'expr' part of the associated expression/statement.
-  Expr *getExpr() {
-    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_E]);
-  }
-  const Expr *getExpr() const {
-    return cast_or_null<Expr>(Data->getChildren()[DataPositionTy::POS_E]);
-  }
 
   static bool classof(const Stmt *T) {
     return T->getStmtClass() == OMPAtomicDirectiveClass;
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -10485,10 +10485,11 @@
   " '{v = x; x = x binop expr;}', '{v = x; x = expr binop x;}', '{x = x binop expr; v = x;}', '{x = expr binop x; v = x;}' or '{v = x; x = expr;}',"
   " '{v = x; x++;}', '{v = x; ++x;}', '{++x; v = x;}', '{x++; v = x;}', '{v = x; x--;}', '{v = x; --x;}', '{--x; v = x;}', '{x--; v = x;}'"
   " where x is an lvalue expression with scalar type">;
+def err_omp_atomic_compare : Error<"atomic compare is not supported for now">;
 def note_omp_atomic_capture: Note<
   "%select{expected assignment expression|expected compound statement|expected exactly two expression statements|expected in right hand side of the first expression}0">;
 def err_omp_atomic_several_clauses : Error<
-  "directive '#pragma omp atomic' cannot contain more than one 'read', 'write', 'update' or 'capture' clause">;
+  "directive '#pragma omp atomic' cannot contain more than one 'read', 'write', 'update', 'capture', or 'compare' clause">;
 def err_omp_several_mem_order_clauses : Error<
   "directive '#pragma omp %0' cannot contain more than one %select{'seq_cst', 'relaxed', |}1'acq_rel', 'acquire' or 'release' clause">;
 def err_omp_atomic_incompatible_mem_order_clause : Error<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -11190,6 +11190,9 @@
   /// Called on well-formed 'capture' clause.
   OMPClause *ActOnOpenMPCaptureClause(SourceLocation StartLoc,
                                       SourceLocation EndLoc);
+  /// Called on well-formed 'compare' clause.
+  OMPClause *ActOnOpenMPCompareClause(SourceLocation StartLoc,
+                                      SourceLocation EndLoc);
   /// Called on well-formed 'seq_cst' clause.
   OMPClause *ActOnOpenMPSeqCstClause(SourceLocation StartLoc,
                                      SourceLocation EndLoc);
diff --git a/clang/lib/AST/OpenMPClause.cpp b/clang/lib/AST/OpenMPClause.cpp
--- a/clang/lib/AST/OpenMPClause.cpp
+++ b/clang/lib/AST/OpenMPClause.cpp
@@ -126,6 +126,7 @@
   case OMPC_write:
   case OMPC_update:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
@@ -217,6 +218,7 @@
   case OMPC_write:
   case OMPC_update:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
@@ -1792,6 +1794,10 @@
   OS << "capture";
 }
 
+void OMPClausePrinter::VisitOMPCompareClause(OMPCompareClause *) {
+  OS << "compare";
+}
+
 void OMPClausePrinter::VisitOMPSeqCstClause(OMPSeqCstClause *) {
   OS << "seq_cst";
 }
diff --git a/clang/lib/AST/StmtOpenMP.cpp b/clang/lib/AST/StmtOpenMP.cpp
--- a/clang/lib/AST/StmtOpenMP.cpp
+++ b/clang/lib/AST/StmtOpenMP.cpp
@@ -868,10 +868,10 @@
     ArrayRef<OMPClause *> Clauses, Stmt *AssociatedStmt, Expr *X, Expr *V,
     Expr *E, Expr *UE, bool IsXLHSInRHSPart, bool IsPostfixUpdate) {
   auto *Dir = createDirective<OMPAtomicDirective>(
-      C, Clauses, AssociatedStmt, /*NumChildren=*/4, StartLoc, EndLoc);
+      C, Clauses, AssociatedStmt, /*NumChildren=*/6, StartLoc, EndLoc);
   Dir->setX(X);
   Dir->setV(V);
-  Dir->setExpr(E);
+  Dir->setE(E);
   Dir->setUpdateExpr(UE);
   Dir->IsXLHSInRHSPart = IsXLHSInRHSPart;
   Dir->IsPostfixUpdate = IsPostfixUpdate;
diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -551,6 +551,8 @@
 
 void OMPClauseProfiler::VisitOMPCaptureClause(const OMPCaptureClause *) {}
 
+void OMPClauseProfiler::VisitOMPCompareClause(const OMPCompareClause *) {}
+
 void OMPClauseProfiler::VisitOMPSeqCstClause(const OMPSeqCstClause *) {}
 
 void OMPClauseProfiler::VisitOMPAcqRelClause(const OMPAcqRelClause *) {}
diff --git a/clang/lib/Basic/OpenMPKinds.cpp b/clang/lib/Basic/OpenMPKinds.cpp
--- a/clang/lib/Basic/OpenMPKinds.cpp
+++ b/clang/lib/Basic/OpenMPKinds.cpp
@@ -163,6 +163,7 @@
   case OMPC_read:
   case OMPC_write:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
@@ -428,6 +429,7 @@
   case OMPC_read:
   case OMPC_write:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -5918,6 +5918,10 @@
     emitOMPAtomicCaptureExpr(CGF, AO, IsPostfixUpdate, V, X, E, UE,
                              IsXLHSInRHSPart, Loc);
     break;
+  case OMPC_compare:
+    llvm_unreachable("atomic compare is not supported yet, and this should "
+                     "never be reached.");
+    break;
   case OMPC_if:
   case OMPC_final:
   case OMPC_num_threads:
@@ -6061,7 +6065,7 @@
   LexicalScope Scope(*this, S.getSourceRange());
   EmitStopPoint(S.getAssociatedStmt());
   emitOMPAtomicExpr(*this, Kind, AO, S.isPostfixUpdate(), S.getX(), S.getV(),
-                    S.getExpr(), S.getUpdateExpr(), S.isXLHSInRHSPart(),
+                    S.getE(), S.getUpdateExpr(), S.isXLHSInRHSPart(),
                     S.getBeginLoc());
 }
 
diff --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
--- a/clang/lib/Parse/ParseOpenMP.cpp
+++ b/clang/lib/Parse/ParseOpenMP.cpp
@@ -3192,6 +3192,7 @@
   case OMPC_read:
   case OMPC_write:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -6371,6 +6371,7 @@
       case OMPC_write:
       case OMPC_update:
       case OMPC_capture:
+      case OMPC_compare:
       case OMPC_seq_cst:
       case OMPC_acq_rel:
       case OMPC_acquire:
@@ -10952,7 +10953,8 @@
   for (const OMPClause *C : Clauses) {
     if (C->getClauseKind() == OMPC_read || C->getClauseKind() == OMPC_write ||
         C->getClauseKind() == OMPC_update ||
-        C->getClauseKind() == OMPC_capture) {
+        C->getClauseKind() == OMPC_capture ||
+        C->getClauseKind() == OMPC_compare) {
       if (AtomicKind != OMPC_unknown) {
         Diag(C->getBeginLoc(), diag::err_omp_atomic_several_clauses)
             << SourceRange(C->getBeginLoc(), C->getEndLoc());
@@ -11007,9 +11009,13 @@
   if (auto *EWC = dyn_cast<ExprWithCleanups>(Body))
     Body = EWC->getSubExpr();
 
+  // Stands for 'x' in the spec
   Expr *X = nullptr;
+  // Stands for 'v' in the spec
   Expr *V = nullptr;
+  // Stands for 'e' or 'expr' in the spec
   Expr *E = nullptr;
+  // Stands for update-stmt in the spec
   Expr *UE = nullptr;
   bool IsXLHSInRHSPart = false;
   bool IsPostfixUpdate = false;
@@ -11092,8 +11098,8 @@
     if (ErrorFound != NoError) {
       Diag(ErrorLoc, diag::err_omp_atomic_read_not_expression_statement)
           << ErrorRange;
-      Diag(NoteLoc, diag::note_omp_atomic_read_write) << ErrorFound
-                                                      << NoteRange;
+      Diag(NoteLoc, diag::note_omp_atomic_read_write)
+          << ErrorFound << NoteRange;
       return StmtError();
     }
     if (CurContext->isDependentContext())
@@ -11154,8 +11160,8 @@
     if (ErrorFound != NoError) {
       Diag(ErrorLoc, diag::err_omp_atomic_write_not_expression_statement)
           << ErrorRange;
-      Diag(NoteLoc, diag::note_omp_atomic_read_write) << ErrorFound
-                                                      << NoteRange;
+      Diag(NoteLoc, diag::note_omp_atomic_read_write)
+          << ErrorFound << NoteRange;
       return StmtError();
     }
     if (CurContext->isDependentContext())
@@ -11171,9 +11177,10 @@
     //  x = expr binop x;
     OpenMPAtomicUpdateChecker Checker(*this);
     if (Checker.checkStatement(
-            Body, (AtomicKind == OMPC_update)
-                      ? diag::err_omp_atomic_update_not_expression_statement
-                      : diag::err_omp_atomic_not_expression_statement,
+            Body,
+            (AtomicKind == OMPC_update)
+                ? diag::err_omp_atomic_update_not_expression_statement
+                : diag::err_omp_atomic_not_expression_statement,
             diag::note_omp_atomic_update))
       return StmtError();
     if (!CurContext->isDependentContext()) {
@@ -11387,15 +11394,19 @@
             SourceRange(Body->getBeginLoc(), Body->getBeginLoc());
         ErrorFound = NotACompoundStatement;
       }
-      if (ErrorFound != NoError) {
-        Diag(ErrorLoc, diag::err_omp_atomic_capture_not_compound_statement)
-            << ErrorRange;
-        Diag(NoteLoc, diag::note_omp_atomic_capture) << ErrorFound << NoteRange;
-        return StmtError();
-      }
-      if (CurContext->isDependentContext())
-        UE = V = E = X = nullptr;
     }
+    if (ErrorFound != NoError) {
+      Diag(ErrorLoc, diag::err_omp_atomic_capture_not_compound_statement)
+          << ErrorRange;
+      Diag(NoteLoc, diag::note_omp_atomic_capture) << ErrorFound << NoteRange;
+      return StmtError();
+    }
+    if (CurContext->isDependentContext())
+      UE = V = E = X = nullptr;
+  } else if (AtomicKind == OMPC_compare) {
+    // TODO: For now we just return error
+    Diag(Body->getBeginLoc(), diag::err_omp_atomic_compare);
+      return StmtError();
   }
 
   setFunctionHasBranchProtectedScope();
@@ -13476,6 +13487,7 @@
   case OMPC_write:
   case OMPC_update:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
@@ -14307,6 +14319,7 @@
   case OMPC_write:
   case OMPC_update:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
@@ -14768,6 +14781,7 @@
   case OMPC_read:
   case OMPC_write:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
@@ -15073,6 +15087,7 @@
   case OMPC_write:
   case OMPC_update:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
@@ -15261,6 +15276,9 @@
   case OMPC_capture:
     Res = ActOnOpenMPCaptureClause(StartLoc, EndLoc);
     break;
+  case OMPC_compare:
+    Res = ActOnOpenMPCompareClause(StartLoc, EndLoc);
+    break;
   case OMPC_seq_cst:
     Res = ActOnOpenMPSeqCstClause(StartLoc, EndLoc);
     break;
@@ -15407,6 +15425,11 @@
   return new (Context) OMPCaptureClause(StartLoc, EndLoc);
 }
 
+OMPClause *Sema::ActOnOpenMPCompareClause(SourceLocation StartLoc,
+                                          SourceLocation EndLoc) {
+  return new (Context) OMPCompareClause(StartLoc, EndLoc);
+}
+
 OMPClause *Sema::ActOnOpenMPSeqCstClause(SourceLocation StartLoc,
                                          SourceLocation EndLoc) {
   return new (Context) OMPSeqCstClause(StartLoc, EndLoc);
@@ -15875,6 +15898,7 @@
   case OMPC_write:
   case OMPC_update:
   case OMPC_capture:
+  case OMPC_compare:
   case OMPC_seq_cst:
   case OMPC_acq_rel:
   case OMPC_acquire:
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -9429,6 +9429,13 @@
   return C;
 }
 
+template <typename Derived>
+OMPClause *
+TreeTransform<Derived>::TransformOMPCompareClause(OMPCompareClause *C) {
+  // No need to rebuild this clause, no template-dependent parameters.
+  return C;
+}
+
 template <typename Derived>
 OMPClause *
 TreeTransform<Derived>::TransformOMPSeqCstClause(OMPSeqCstClause *C) {
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -11761,6 +11761,9 @@
   case llvm::omp::OMPC_capture:
     C = new (Context) OMPCaptureClause();
     break;
+  case llvm::omp::OMPC_compare:
+    C = new (Context) OMPCompareClause();
+    break;
   case llvm::omp::OMPC_seq_cst:
     C = new (Context) OMPSeqCstClause();
     break;
@@ -12119,6 +12122,8 @@
 
 void OMPClauseReader::VisitOMPCaptureClause(OMPCaptureClause *) {}
 
+void OMPClauseReader::VisitOMPCompareClause(OMPCompareClause *) {}
+
 void OMPClauseReader::VisitOMPSeqCstClause(OMPSeqCstClause *) {}
 
 void OMPClauseReader::VisitOMPAcqRelClause(OMPAcqRelClause *) {}
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6248,6 +6248,8 @@
 
 void OMPClauseWriter::VisitOMPCaptureClause(OMPCaptureClause *) {}
 
+void OMPClauseWriter::VisitOMPCompareClause(OMPCompareClause *) {}
+
 void OMPClauseWriter::VisitOMPSeqCstClause(OMPSeqCstClause *) {}
 
 void OMPClauseWriter::VisitOMPAcqRelClause(OMPAcqRelClause *) {}
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -2273,6 +2273,8 @@
 
 void OMPClauseEnqueue::VisitOMPCaptureClause(const OMPCaptureClause *) {}
 
+void OMPClauseEnqueue::VisitOMPCompareClause(const OMPCompareClause *) {}
+
 void OMPClauseEnqueue::VisitOMPSeqCstClause(const OMPSeqCstClause *) {}
 
 void OMPClauseEnqueue::VisitOMPAcqRelClause(const OMPAcqRelClause *) {}
diff --git a/llvm/include/llvm/Frontend/OpenMP/OMP.td b/llvm/include/llvm/Frontend/OpenMP/OMP.td
--- a/llvm/include/llvm/Frontend/OpenMP/OMP.td
+++ b/llvm/include/llvm/Frontend/OpenMP/OMP.td
@@ -180,6 +180,7 @@
 def OMPC_Write : Clause<"write"> { let clangClass = "OMPWriteClause"; }
 def OMPC_Update : Clause<"update"> { let clangClass = "OMPUpdateClause"; }
 def OMPC_Capture : Clause<"capture"> { let clangClass = "OMPCaptureClause"; }
+def OMPC_Compare : Clause<"compare"> { let clangClass = "OMPCompareClause"; }
 def OMPC_SeqCst : Clause<"seq_cst"> { let clangClass = "OMPSeqCstClause"; }
 def OMPC_AcqRel : Clause<"acq_rel"> { let clangClass = "OMPAcqRelClause"; }
 def OMPC_Acquire : Clause<"acquire"> { let clangClass = "OMPAcquireClause"; }
@@ -536,6 +537,7 @@
     VersionedClause<OMPC_Write>,
     VersionedClause<OMPC_Update>,
     VersionedClause<OMPC_Capture>,
+    VersionedClause<OMPC_Compare, 51>
   ];
   let allowedOnceClauses = [
     VersionedClause<OMPC_SeqCst>,