diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -4554,6 +4554,7 @@
 public:
   enum UTTKind {
     EnumUnderlyingType,
+    AddCV,
     AddConst,
     AddVolatile,
   };
diff --git a/clang/include/clang/Basic/Specifiers.h b/clang/include/clang/Basic/Specifiers.h
--- a/clang/include/clang/Basic/Specifiers.h
+++ b/clang/include/clang/Basic/Specifiers.h
@@ -84,6 +84,7 @@
     TST_decltype,        // C++11 decltype
     TST_underlyingType,  // __underlying_type for C++11
     TST_add_const,       // __add_const extension
+    TST_add_cv,          // __add_cv extension
     TST_add_volatile,    // __add_volatile extension
     TST_auto,            // C++11 auto
     TST_decltype_auto,   // C++1y decltype(auto)
diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
--- a/clang/include/clang/Basic/TokenKinds.def
+++ b/clang/include/clang/Basic/TokenKinds.def
@@ -509,6 +509,7 @@
              HasUniqueObjectRepresentations, KEYCXX)
 KEYWORD(__underlying_type           , KEYCXX)
 KEYWORD(__add_const, KEYCXX)
+KEYWORD(__add_cv, KEYCXX)
 KEYWORD(__add_volatile, KEYCXX)
 
 // Clang-only C++ Type Traits
diff --git a/clang/include/clang/Sema/DeclSpec.h b/clang/include/clang/Sema/DeclSpec.h
--- a/clang/include/clang/Sema/DeclSpec.h
+++ b/clang/include/clang/Sema/DeclSpec.h
@@ -292,6 +292,7 @@
   static const TST TST_decltype_auto = clang::TST_decltype_auto;
   static const TST TST_underlyingType = clang::TST_underlyingType;
   static const TST TST_add_const = clang::TST_add_const;
+  static const TST TST_add_cv = clang::TST_add_cv;
   static const TST TST_add_volatile = clang::TST_add_volatile;
   static const TST TST_auto = clang::TST_auto;
   static const TST TST_auto_type = clang::TST_auto_type;
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -3928,6 +3928,9 @@
       case UnaryTransformType::AddConst:
         Out << "3ac";
         break;
+      case UnaryTransformType::AddCV:
+        Out << "3acv";
+        break;
       case UnaryTransformType::AddVolatile:
         Out << "3av";
         break;
diff --git a/clang/lib/AST/JSONNodeDumper.cpp b/clang/lib/AST/JSONNodeDumper.cpp
--- a/clang/lib/AST/JSONNodeDumper.cpp
+++ b/clang/lib/AST/JSONNodeDumper.cpp
@@ -668,6 +668,9 @@
   case UnaryTransformType::AddConst:
     JOS.attribute("transformedKind", "add_const");
     break;
+  case UnaryTransformType::AddCV:
+    JOS.attribute("transformedKind", "add_cv");
+    break;
   case UnaryTransformType::AddVolatile:
     JOS.attribute("transformedKind", "add_volatile");
     break;
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -1121,9 +1121,10 @@
   switch (T->getUTTKind()) {
     case UnaryTransformType::EnumUnderlyingType:
     case UnaryTransformType::AddConst:
+    case UnaryTransformType::AddCV:
     case UnaryTransformType::AddVolatile: {
-      constexpr std::array<const char *, 3> Transformation = {
-          "__underlying_type", "__add_const", "__add_volatile"};
+      constexpr std::array<const char *, 4> Transformation = {
+          "__underlying_type", "__add_const", "__add_cv", "__add_volatile"};
       OS << Transformation[T->getUTTKind()] << '(';
       print(T->getBaseType(), OS, StringRef());
       OS << ')';
@@ -1142,6 +1143,7 @@
   switch (T->getUTTKind()) {
     case UnaryTransformType::EnumUnderlyingType:
     case UnaryTransformType::AddConst:
+    case UnaryTransformType::AddCV:
     case UnaryTransformType::AddVolatile:
       return;
   }
diff --git a/clang/lib/Format/FormatToken.cpp b/clang/lib/Format/FormatToken.cpp
--- a/clang/lib/Format/FormatToken.cpp
+++ b/clang/lib/Format/FormatToken.cpp
@@ -58,6 +58,7 @@
   case tok::kw_bool:
   case tok::kw___underlying_type:
   case tok::kw___add_const:
+  case tok::kw___add_cv:
   case tok::kw___add_volatile:
   case tok::annot_typename:
   case tok::kw_char8_t:
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1659,6 +1659,7 @@
               .Case("__reference_binds_to_temporary", true)
               .Case("__underlying_type", true)
               .Case("__add_const", true)
+              .Case("__add_cv", true)
               .Case("__add_volatile", true)
               .Default(false);
         } else {
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -4116,6 +4116,7 @@
       continue;
 
     case tok::kw___add_const:
+    case tok::kw___add_cv:
     case tok::kw___add_volatile:
       ParseTypeTransformTypeSpecifier(DS);
       continue;
@@ -4224,6 +4225,8 @@
   switch (Tok.getKind()) {
   case tok::kw___add_const:
     return DeclSpec::TST_add_const;
+  case tok::kw___add_cv:
+    return DeclSpec::TST_add_cv;
   case tok::kw___add_volatile:
     return DeclSpec::TST_add_volatile;
   }
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1511,14 +1511,15 @@
   if (TagType == DeclSpec::TST_struct && Tok.isNot(tok::identifier) &&
       !Tok.isAnnotation() && Tok.getIdentifierInfo() &&
       Tok.isOneOf(
-          tok::kw___add_const, tok::kw___add_volatile, tok::kw___is_abstract,
-          tok::kw___is_aggregate, tok::kw___is_arithmetic, tok::kw___is_array,
-          tok::kw___is_assignable, tok::kw___is_base_of, tok::kw___is_class,
-          tok::kw___is_complete_type, tok::kw___is_compound, tok::kw___is_const,
-          tok::kw___is_constructible, tok::kw___is_convertible,
-          tok::kw___is_convertible_to, tok::kw___is_destructible,
-          tok::kw___is_empty, tok::kw___is_enum, tok::kw___is_floating_point,
-          tok::kw___is_final, tok::kw___is_function, tok::kw___is_fundamental,
+          tok::kw___add_const, tok::kw___add_cv, tok::kw___add_volatile,
+          tok::kw___is_abstract, tok::kw___is_aggregate,
+          tok::kw___is_arithmetic, tok::kw___is_array, tok::kw___is_assignable,
+          tok::kw___is_base_of, tok::kw___is_class, tok::kw___is_complete_type,
+          tok::kw___is_compound, tok::kw___is_const, tok::kw___is_constructible,
+          tok::kw___is_convertible, tok::kw___is_convertible_to,
+          tok::kw___is_destructible, tok::kw___is_empty, tok::kw___is_enum,
+          tok::kw___is_floating_point, tok::kw___is_final,
+          tok::kw___is_function, tok::kw___is_fundamental,
           tok::kw___is_integral, tok::kw___is_interface_class,
           tok::kw___is_literal, tok::kw___is_lvalue_expr,
           tok::kw___is_lvalue_reference, tok::kw___is_member_function_pointer,
diff --git a/clang/lib/Sema/DeclSpec.cpp b/clang/lib/Sema/DeclSpec.cpp
--- a/clang/lib/Sema/DeclSpec.cpp
+++ b/clang/lib/Sema/DeclSpec.cpp
@@ -391,6 +391,7 @@
 
     case TST_underlyingType:
     case TST_add_const:
+    case TST_add_cv:
     case TST_add_volatile:
     case TST_typename:
     case TST_typeofType: {
@@ -581,6 +582,8 @@
   case DeclSpec::TST_underlyingType: return "__underlying_type";
   case DeclSpec::TST_add_const:
     return "__add_const";
+  case DeclSpec::TST_add_cv:
+    return "__add_cv";
   case DeclSpec::TST_add_volatile:
     return "__add_volatile";
   case DeclSpec::TST_unknown_anytype: return "__unknown_anytype";
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -146,6 +146,7 @@
   case tok::kw_bool:
   case tok::kw___underlying_type:
   case tok::kw___add_const:
+  case tok::kw___add_cv:
   case tok::kw___add_volatile:
   case tok::kw___auto_type:
     return true;
@@ -5602,6 +5603,7 @@
   case DeclSpec::TST_typeofType:
   case DeclSpec::TST_underlyingType:
   case DeclSpec::TST_add_const:
+  case DeclSpec::TST_add_cv:
   case DeclSpec::TST_add_volatile:
   case DeclSpec::TST_atomic: {
     // Grab the type from the parser.
diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -862,6 +862,7 @@
   case TST_typeofType:
   case TST_underlyingType:
   case TST_add_const:
+  case TST_add_cv:
   case TST_add_volatile:
   case TST_atomic: {
     QualType T = DS.getRepAsType().get();
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1262,6 +1262,8 @@
   switch (SwitchTST) {
   case TST_add_const:
     return UnaryTransformType::AddConst;
+  case TST_add_cv:
+    return UnaryTransformType::AddCV;
   case TST_add_volatile:
     return UnaryTransformType::AddVolatile;
   case TST_underlyingType:
@@ -1655,6 +1657,7 @@
   }
   case DeclSpec::TST_underlyingType:
   case DeclSpec::TST_add_const:
+  case DeclSpec::TST_add_cv:
   case DeclSpec::TST_add_volatile:
     Result = S.GetTypeFromParser(DS.getRepAsType());
     assert(!Result.isNull() && "Didn't get a type for the transformation?");
@@ -9083,25 +9086,25 @@
       return Context.getUnaryTransformType(BaseType, Underlying,
                                         UnaryTransformType::EnumUnderlyingType);
     }
-  case UnaryTransformType::AddConst: {
-    SplitQualType Split = BaseType.getSplitUnqualifiedType();
-    Qualifiers Quals = BaseType.getQualifiers();
-    if (BaseType->isReferenceType() || BaseType->isFunctionType())
-      return BaseType;
-    Quals.addConst();
-    QualType Underlying(Split.Ty, Quals.getAsOpaqueValue());
-    return Context.getUnaryTransformType(BaseType, Underlying,
-                                         UnaryTransformType::AddConst);
-  }
+  case UnaryTransformType::AddConst:
+  case UnaryTransformType::AddCV:
   case UnaryTransformType::AddVolatile: {
     SplitQualType Split = BaseType.getSplitUnqualifiedType();
     Qualifiers Quals = BaseType.getQualifiers();
     if (BaseType->isReferenceType() || BaseType->isFunctionType())
       return BaseType;
-    Quals.addVolatile();
+    switch (UKind) {
+    case UnaryTransformType::AddConst:
+      Quals.addConst();
+      break;
+    case UnaryTransformType::AddCV:
+      Quals.addConst();
+      [[fallthrough]];
+    case UnaryTransformType::AddVolatile:
+      Quals.addVolatile();
+    }
     QualType Underlying(Split.Ty, Quals.getAsOpaqueValue());
-    return Context.getUnaryTransformType(BaseType, Underlying,
-                                         UnaryTransformType::AddVolatile);
+    return Context.getUnaryTransformType(BaseType, Underlying, UKind);
   }
   }
   llvm_unreachable("unknown unary transform type");
diff --git a/clang/test/SemaCXX/add_cv.cpp b/clang/test/SemaCXX/add_cv.cpp
--- a/clang/test/SemaCXX/add_cv.cpp
+++ b/clang/test/SemaCXX/add_cv.cpp
@@ -7,6 +7,7 @@
 constexpr bool check_add_cv() {
   static_assert(__is_same(__add_const(T), const T), "");
   static_assert(__is_same(__add_volatile(T), volatile T), "");
+  static_assert(__is_same(__add_cv(T), const volatile T), "");
   return true;
 }