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
@@ -24,6 +24,7 @@
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Basic/OpenMPKinds.h"
 #include "clang/Basic/PrettyStackTrace.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/Frontend/OpenMP/OMPConstants.h"
 #include "llvm/Frontend/OpenMP/OMPIRBuilder.h"
@@ -6015,7 +6016,7 @@
                               llvm::AtomicOrdering AO, bool IsPostfixUpdate,
                               const Expr *X, const Expr *V, const Expr *E,
                               const Expr *UE, bool IsXLHSInRHSPart,
-                              SourceLocation Loc) {
+                              bool IsCompareCapture, SourceLocation Loc) {
   switch (Kind) {
   case OMPC_read:
     emitOMPAtomicReadExpr(CGF, AO, X, V, Loc);
@@ -6032,10 +6033,13 @@
                              IsXLHSInRHSPart, Loc);
     break;
   case OMPC_compare: {
-    // Emit an error here.
-    unsigned DiagID = CGF.CGM.getDiags().getCustomDiagID(
-        DiagnosticsEngine::Error, "'atomic compare' is not supported for now");
-    CGF.CGM.getDiags().Report(DiagID);
+    if (!IsCompareCapture) {
+      // Emit an error here.
+      unsigned DiagID = CGF.CGM.getDiags().getCustomDiagID(
+          DiagnosticsEngine::Error,
+          "'atomic compare' is not supported for now");
+      CGF.CGM.getDiags().Report(DiagID);
+    }
     break;
   }
   case OMPC_if:
@@ -6148,19 +6152,20 @@
     AO = llvm::AtomicOrdering::Monotonic;
     MemOrderingSpecified = true;
   }
+  llvm::SmallSet<OpenMPClauseKind, 2> KindsEncountered;
   OpenMPClauseKind Kind = OMPC_unknown;
   for (const OMPClause *C : S.clauses()) {
     // Find first clause (skip seq_cst|acq_rel|aqcuire|release|relaxed clause,
     // if it is first).
-    if (C->getClauseKind() != OMPC_seq_cst &&
-        C->getClauseKind() != OMPC_acq_rel &&
-        C->getClauseKind() != OMPC_acquire &&
-        C->getClauseKind() != OMPC_release &&
-        C->getClauseKind() != OMPC_relaxed && C->getClauseKind() != OMPC_hint) {
-      Kind = C->getClauseKind();
-      break;
-    }
+    OpenMPClauseKind K = C->getClauseKind();
+    if (K == OMPC_seq_cst || K == OMPC_acq_rel || K == OMPC_acquire ||
+        K == OMPC_release || K == OMPC_relaxed || K == OMPC_hint)
+      continue;
+    Kind = K;
+    KindsEncountered.insert(K);
   }
+  bool IsCompareCapture = KindsEncountered.contains(OMPC_compare) &&
+                          KindsEncountered.contains(OMPC_capture);
   if (!MemOrderingSpecified) {
     llvm::AtomicOrdering DefaultOrder =
         CGM.getOpenMPRuntime().getDefaultMemoryOrdering();
@@ -6183,7 +6188,7 @@
   EmitStopPoint(S.getAssociatedStmt());
   emitOMPAtomicExpr(*this, Kind, AO, S.isPostfixUpdate(), S.getX(), S.getV(),
                     S.getExpr(), S.getUpdateExpr(), S.isXLHSInRHSPart(),
-                    S.getBeginLoc());
+                    IsCompareCapture, S.getBeginLoc());
 }
 
 static void emitCommonOMPTargetDirective(CodeGenFunction &CGF,
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
@@ -35,6 +35,7 @@
 #include "llvm/ADT/IndexedMap.h"
 #include "llvm/ADT/PointerEmbeddedInt.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Frontend/OpenMP/OMPAssume.h"
 #include "llvm/Frontend/OpenMP/OMPConstants.h"
@@ -11315,14 +11316,18 @@
   SourceLocation AtomicKindLoc;
   OpenMPClauseKind MemOrderKind = OMPC_unknown;
   SourceLocation MemOrderLoc;
+  bool MutexClauseEncountered = false;
+  llvm::SmallSet<OpenMPClauseKind, 2> EncounteredAtomicKinds;
   for (const OMPClause *C : Clauses) {
     switch (C->getClauseKind()) {
     case OMPC_read:
     case OMPC_write:
     case OMPC_update:
+      MutexClauseEncountered = true;
+      LLVM_FALLTHROUGH;
     case OMPC_capture:
     case OMPC_compare: {
-      if (AtomicKind != OMPC_unknown) {
+      if (AtomicKind != OMPC_unknown && MutexClauseEncountered) {
         Diag(C->getBeginLoc(), diag::err_omp_atomic_several_clauses)
             << SourceRange(C->getBeginLoc(), C->getEndLoc());
         Diag(AtomicKindLoc, diag::note_omp_previous_mem_order_clause)
@@ -11330,6 +11335,7 @@
       } else {
         AtomicKind = C->getClauseKind();
         AtomicKindLoc = C->getBeginLoc();
+        EncounteredAtomicKinds.insert(C->getClauseKind());
       }
       break;
     }
@@ -11357,6 +11363,8 @@
       llvm_unreachable("unknown clause is encountered");
     }
   }
+  bool IsCompareCapture = EncounteredAtomicKinds.contains(OMPC_compare) &&
+                          EncounteredAtomicKinds.contains(OMPC_capture);
   // OpenMP 5.0, 2.17.7 atomic Construct, Restrictions
   // If atomic-clause is read then memory-order-clause must not be acq_rel or
   // release.
@@ -11775,17 +11783,26 @@
     if (CurContext->isDependentContext())
       UE = V = E = X = nullptr;
   } else if (AtomicKind == OMPC_compare) {
-    OpenMPAtomicCompareChecker::ErrorInfoTy ErrorInfo;
-    OpenMPAtomicCompareChecker Checker(*this);
-    if (!Checker.checkStmt(Body, ErrorInfo)) {
-      Diag(ErrorInfo.ErrorLoc, diag::err_omp_atomic_compare)
-          << ErrorInfo.ErrorRange;
-      Diag(ErrorInfo.NoteLoc, diag::note_omp_atomic_compare)
-          << ErrorInfo.Error << ErrorInfo.NoteRange;
-      return StmtError();
+    if (IsCompareCapture) {
+      // TODO: For now we emit an error here and in emitOMPAtomicExpr we ignore
+      // code gen.
+      unsigned DiagID = Diags.getCustomDiagID(
+          DiagnosticsEngine::Error,
+          "atomic compare capture is not supported for now");
+      Diag(AtomicKindLoc, DiagID);
+    } else {
+      OpenMPAtomicCompareChecker::ErrorInfoTy ErrorInfo;
+      OpenMPAtomicCompareChecker Checker(*this);
+      if (!Checker.checkStmt(Body, ErrorInfo)) {
+        Diag(ErrorInfo.ErrorLoc, diag::err_omp_atomic_compare)
+            << ErrorInfo.ErrorRange;
+        Diag(ErrorInfo.NoteLoc, diag::note_omp_atomic_compare)
+            << ErrorInfo.Error << ErrorInfo.NoteRange;
+        return StmtError();
+      }
+      // TODO: We don't set X, D, E, etc. here because in code gen we will emit
+      // error directly.
     }
-    // TODO: We don't set X, D, E, etc. here because in code gen we will emit
-    // error directly.
   }
 
   setFunctionHasBranchProtectedScope();
diff --git a/clang/test/OpenMP/atomic_messages.cpp b/clang/test/OpenMP/atomic_messages.cpp
--- a/clang/test/OpenMP/atomic_messages.cpp
+++ b/clang/test/OpenMP/atomic_messages.cpp
@@ -958,3 +958,16 @@
   // expected-note@+1 {{in instantiation of function template specialization 'mixed<int>' requested here}}
   return mixed<int>();
 }
+
+#ifdef OMP51
+int compare_capture() {
+  int a, b, c, x;
+// omp51-error@+1 {{atomic compare capture is not supported for now}}
+#pragma omp atomic compare capture
+  {
+    x = a;
+    if (a == b)
+      a = c;
+  }
+}
+#endif