diff --git a/lib/AST/SwiftNameTranslation.cpp b/lib/AST/SwiftNameTranslation.cpp
index ce5e512e035..0e0653dd059 100644
--- a/lib/AST/SwiftNameTranslation.cpp
+++ b/lib/AST/SwiftNameTranslation.cpp
@@ -163,6 +163,10 @@ swift::cxx_translation::getNameForCxx(const ValueDecl *VD,
   if (customNamesOnly)
     return StringRef();
 
+  if (auto *mod = dyn_cast<ModuleDecl>(VD)) {
+    if (mod->isStdlibModule())
+      return "swift";
+  }
   if (VD->getModuleContext()->isStdlibModule()) {
     // Incorporate argument labels into Stdlib API names.
     // FIXME: This should be done more broadly.
diff --git a/lib/PrintAsClang/ClangSyntaxPrinter.cpp b/lib/PrintAsClang/ClangSyntaxPrinter.cpp
index da532c802e4..b610e15d170 100644
--- a/lib/PrintAsClang/ClangSyntaxPrinter.cpp
+++ b/lib/PrintAsClang/ClangSyntaxPrinter.cpp
@@ -142,7 +142,7 @@ void ClangSyntaxPrinter::printModuleNamespaceStart(
     const ModuleDecl &moduleContext) const {
   os << "namespace ";
   printBaseName(&moduleContext);
-  os << " __attribute__((swift_private))";
+  os << " SWIFT_PRIVATE_ATTR";
   printSymbolUSRAttribute(&moduleContext);
   os << " {\n";
 }
@@ -155,7 +155,7 @@ void ClangSyntaxPrinter::printNamespace(
   os << "namespace ";
   namePrinter(os);
   if (trivia == NamespaceTrivia::AttributeSwiftPrivate)
-    os << " __attribute__((swift_private))";
+    os << " SWIFT_PRIVATE_ATTR";
   if (moduleContext)
     printSymbolUSRAttribute(moduleContext);
   os << " {\n\n";
diff --git a/lib/PrintAsClang/ModuleContentsWriter.cpp b/lib/PrintAsClang/ModuleContentsWriter.cpp
index 61ddc91e065..062d05b767d 100644
--- a/lib/PrintAsClang/ModuleContentsWriter.cpp
+++ b/lib/PrintAsClang/ModuleContentsWriter.cpp
@@ -835,8 +835,8 @@ EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
       os << "#endif\n";
     os << "#ifdef __cplusplus\n";
     os << "namespace ";
-    M.ValueDecl::getName().print(os);
-    os << " __attribute__((swift_private))";
+    ClangSyntaxPrinter(os).printBaseName(&M);
+    os << " SWIFT_PRIVATE_ATTR";
     ClangSyntaxPrinter(os).printSymbolUSRAttribute(&M);
     os << " {\n";
     os << "namespace " << cxx_synthesis::getCxxImplNamespaceName() << " {\n";
@@ -854,7 +854,7 @@ EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
 
   // Construct a C++ namespace for the module.
   ClangSyntaxPrinter(os).printNamespace(
-      [&](raw_ostream &os) { M.ValueDecl::getName().print(os); },
+      [&](raw_ostream &os) { ClangSyntaxPrinter(os).printBaseName(&M); },
       [&](raw_ostream &os) { os << moduleOS.str(); },
       ClangSyntaxPrinter::NamespaceTrivia::AttributeSwiftPrivate, &M);
 
diff --git a/lib/PrintAsClang/PrintClangFunction.cpp b/lib/PrintAsClang/PrintClangFunction.cpp
index 8884d70cfc4..d43acffbd9c 100644
--- a/lib/PrintAsClang/PrintClangFunction.cpp
+++ b/lib/PrintAsClang/PrintClangFunction.cpp
@@ -19,6 +19,7 @@
 #include "PrintClangValueType.h"
 #include "SwiftToClangInteropContext.h"
 #include "swift/ABI/MetadataValues.h"
+#include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/GenericParamList.h"
 #include "swift/AST/Module.h"
@@ -218,7 +219,8 @@ public:
                      llvm::function_ref<void()> body) {
     if (!optionalKind || optionalKind == OTK_None)
       return body();
-    os << "Swift::Optional<";
+    printBaseName(moduleContext->getASTContext().getStdlibModule());
+    os << "::Optional<";
     body();
     os << '>';
   }
@@ -718,7 +720,7 @@ ClangRepresentation DeclAndTypeClangFunctionPrinter::printFunctionSignature(
 
   // Print out the return type.
   if (FD->hasThrows() && outputLang == OutputLanguageMode::Cxx)
-    os << "Swift::ThrowingResult<";
+    os << "swift::ThrowingResult<";
   if (kind == FunctionSignatureKind::CFunctionProto) {
     // First, verify that the C++ return type is representable.
     {
@@ -1330,17 +1332,17 @@ void DeclAndTypeClangFunctionPrinter::printCxxThunkBody(
   if (hasThrows) {
     os << "  if (opaqueError != nullptr)\n";
     os << "#ifdef __cpp_exceptions\n";
-    os << "    throw (Swift::Error(opaqueError));\n";
+    os << "    throw (swift::Error(opaqueError));\n";
     os << "#else\n";
     if (resultTy->isVoid()) {
-      os << "    return Swift::Expected<void>(Swift::Error(opaqueError));\n";
+      os << "    return swift::Expected<void>(swift::Error(opaqueError));\n";
       os << "#endif\n";
     } else {
       auto directResultType = signature.getDirectResultType();
       printDirectReturnOrParamCType(
           *directResultType, resultTy, moduleContext, os, cPrologueOS,
           typeMapping, interopContext, [&]() {
-            os << "    return Swift::Expected<";
+            os << "    return swift::Expected<";
             OptionalTypeKind retKind;
             Type objTy;
             std::tie(objTy, retKind) =
@@ -1348,7 +1350,7 @@ void DeclAndTypeClangFunctionPrinter::printCxxThunkBody(
 
             auto s = printClangFunctionReturnType(objTy, retKind, const_cast<ModuleDecl *>(moduleContext),
                                                   OutputLanguageMode::Cxx);
-            os << ">(Swift::Error(opaqueError));\n";
+            os << ">(swift::Error(opaqueError));\n";
             os << "#endif\n";
 
             // Return the function result value if it doesn't throw.
diff --git a/lib/PrintAsClang/PrintSwiftToClangCoreScaffold.cpp b/lib/PrintAsClang/PrintSwiftToClangCoreScaffold.cpp
index 2dc3d29690d..098d3697498 100644
--- a/lib/PrintAsClang/PrintSwiftToClangCoreScaffold.cpp
+++ b/lib/PrintAsClang/PrintSwiftToClangCoreScaffold.cpp
@@ -200,24 +200,27 @@ void swift::printSwiftToClangCoreScaffold(SwiftToClangInteropContext &ctx,
                                           PrimitiveTypeMapping &typeMapping,
                                           raw_ostream &os) {
   ClangSyntaxPrinter printer(os);
-  printer.printNamespace("swift", [&](raw_ostream &) {
-    printer.printNamespace(
-        cxx_synthesis::getCxxImplNamespaceName(), [&](raw_ostream &) {
-          printer.printExternC([&](raw_ostream &os) {
-            printTypeMetadataResponseType(ctx, typeMapping, os);
-            os << "\n";
-            printValueWitnessTable(os);
-            os << "\n";
-            printPrimitiveGenericTypeTraits(os, astContext, typeMapping,
-                                            /*isCForwardDefinition=*/true);
-          });
-          os << "\n";
+  printer.printNamespace(
+      cxx_synthesis::getCxxSwiftNamespaceName(),
+      [&](raw_ostream &) {
+        printer.printNamespace(
+            cxx_synthesis::getCxxImplNamespaceName(), [&](raw_ostream &) {
+              printer.printExternC([&](raw_ostream &os) {
+                printTypeMetadataResponseType(ctx, typeMapping, os);
+                os << "\n";
+                printValueWitnessTable(os);
+                os << "\n";
+                printPrimitiveGenericTypeTraits(os, astContext, typeMapping,
+                                                /*isCForwardDefinition=*/true);
+              });
+              os << "\n";
+            });
+        os << "\n";
+        // C++ only supports inline variables from C++17.
+        ClangSyntaxPrinter(os).printIgnoredCxx17ExtensionDiagnosticBlock([&]() {
+          printPrimitiveGenericTypeTraits(os, astContext, typeMapping,
+                                          /*isCForwardDefinition=*/false);
         });
-    os << "\n";
-    // C++ only supports inline variables from C++17.
-    ClangSyntaxPrinter(os).printIgnoredCxx17ExtensionDiagnosticBlock([&]() {
-      printPrimitiveGenericTypeTraits(os, astContext, typeMapping,
-                                      /*isCForwardDefinition=*/false);
-    });
-  });
+      },
+      ClangSyntaxPrinter::NamespaceTrivia::AttributeSwiftPrivate);
 }
diff --git a/lib/PrintAsClang/_SwiftCxxInteroperability.h b/lib/PrintAsClang/_SwiftCxxInteroperability.h
index 4b255bfc7d3..3a8efced961 100644
--- a/lib/PrintAsClang/_SwiftCxxInteroperability.h
+++ b/lib/PrintAsClang/_SwiftCxxInteroperability.h
@@ -71,7 +71,13 @@
 #define SWIFT_SYMBOL_MODULE(moduleValue)
 #endif
 
-namespace swift {
+#if __has_attribute(swift_private)
+#define SWIFT_PRIVATE_ATTR __attribute__((swift_private))
+#else
+#define SWIFT_PRIVATE_ATTR
+#endif
+
+namespace swift SWIFT_PRIVATE_ATTR {
 namespace _impl {
 
 extern "C" void *_Nonnull swift_retain(void *_Nonnull) noexcept;
@@ -243,7 +249,7 @@ SWIFT_INLINE_THUNK void *_Nonnull getOpaquePointer(T &value) {
 
 #pragma clang diagnostic pop
 
-} // namespace swift
+} // namespace swift SWIFT_PRIVATE_ATTR
 #endif
 
 #endif // SWIFT_CXX_INTEROPERABILITY_H
diff --git a/lib/PrintAsClang/_SwiftStdlibCxxOverlay.h b/lib/PrintAsClang/_SwiftStdlibCxxOverlay.h
index 13a654ddb2c..c49fe896665 100644
--- a/lib/PrintAsClang/_SwiftStdlibCxxOverlay.h
+++ b/lib/PrintAsClang/_SwiftStdlibCxxOverlay.h
@@ -189,7 +189,7 @@ public:
     opaqueValue = other.opaqueValue;
   }
 
-  template <class T> SWIFT_INLINE_THUNK Swift::Optional<T> as() {
+  template <class T> SWIFT_INLINE_THUNK swift::Optional<T> as() {
     alignas(alignof(T)) char buffer[sizeof(T)];
     const void *em = getErrorMetadata();
     void *ep = getPointerToOpaquePointer();
@@ -207,10 +207,10 @@ public:
             swift::_impl::implClassFor<T>::type::initializeWithTake(dest,
                                                                     buffer);
           });
-      return Swift::Optional<T>::init(result);
+      return swift::Optional<T>::init(result);
     }
 
-    return  Swift::Optional<T>::none();
+    return swift::Optional<T>::none();
   }
 
 private:
@@ -236,7 +236,7 @@ public:
     has_val = false;
   }
 
-  constexpr Expected(const Swift::Error& error_val) noexcept {
+  constexpr Expected(const swift::Error &error_val) noexcept {
     new (&buffer) Error(error_val);
     has_val = false;
   }
@@ -264,7 +264,7 @@ public:
     if (has_value())
       reinterpret_cast<const T *>(buffer)->~T();
     else
-      reinterpret_cast<Swift::Error *>(buffer)->~Error();
+      reinterpret_cast<swift::Error *>(buffer)->~Error();
   }
 
   /// assignment
@@ -313,22 +313,23 @@ public:
   }
 
   // Get error
-  constexpr Swift::Error const& error() const& {
+  constexpr swift::Error const &error() const & {
     if (has_value())
       abort();
-    return reinterpret_cast<const Swift::Error&>(buffer);
+    return reinterpret_cast<const swift::Error &>(buffer);
   }
 
-  constexpr Swift::Error& error() & {
+  constexpr swift::Error &error() & {
     if (has_value())
       abort();
-    return reinterpret_cast<Swift::Error&>(buffer);
+    return reinterpret_cast<swift::Error &>(buffer);
   }
 
   constexpr bool has_value() const noexcept { return has_val; }
 
 private:
-  alignas(_impl::max(alignof(T), alignof(Swift::Error))) char buffer[_impl::max(sizeof(T), sizeof(Swift::Error))];
+  alignas(_impl::max(alignof(T), alignof(swift::Error))) char buffer[_impl::max(
+      sizeof(T), sizeof(swift::Error))];
   bool has_val;
 };
 
@@ -341,12 +342,11 @@ public:
     has_val = false;
   }
 
-  Expected(const Swift::Error& error_val) noexcept {
+  Expected(const swift::Error &error_val) noexcept {
     new (&buffer) Error(error_val);
     has_val = false;
   }
 
-
   /// Copy
   Expected(Expected const& other) noexcept {
     if (other.has_value())
@@ -361,9 +361,7 @@ public:
   // FIXME: Implement move semantics when move swift values is possible
   [[noreturn]] Expected(Expected&&) noexcept { abort(); }
 
-  ~Expected() noexcept {
-    reinterpret_cast<Swift::Error *>(buffer)->~Error();
-  }
+  ~Expected() noexcept { reinterpret_cast<swift::Error *>(buffer)->~Error(); }
 
   /// assignment
   constexpr auto operator=(Expected&& other) noexcept = delete;
@@ -373,21 +371,21 @@ public:
   constexpr explicit operator bool() const noexcept { return has_value(); }
 
   // Get error
-  constexpr Swift::Error const& error() const& {
+  constexpr swift::Error const &error() const & {
     if (has_value())
       abort();
-    return reinterpret_cast<const Swift::Error&>(buffer);
+    return reinterpret_cast<const swift::Error &>(buffer);
   }
 
-  constexpr Swift::Error& error() & {
+  constexpr swift::Error &error() & {
     if (has_value())
       abort();
-    return reinterpret_cast<Swift::Error&>(buffer);
+    return reinterpret_cast<swift::Error &>(buffer);
   }
 
   constexpr bool has_value() const noexcept { return has_val; }
 private:
-  alignas(alignof(Swift::Error)) char buffer[sizeof(Swift::Error)];
+  alignas(alignof(swift::Error)) char buffer[sizeof(swift::Error)];
   bool has_val;
 };
 
@@ -400,10 +398,9 @@ using ThrowingResult = T;
 
 #else
 
-template<class T>
-using ThrowingResult = Swift::Expected<T>;
+template <class T> using ThrowingResult = swift::Expected<T>;
 
-#define SWIFT_RETURN_THUNK(T, v) Swift::Expected<T>(v)
+#define SWIFT_RETURN_THUNK(T, v) swift::Expected<T>(v)
 
 #endif
 
diff --git a/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift b/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift
index a7b98b0e5dc..1d8e0112391 100644
--- a/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift
+++ b/test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift
@@ -192,7 +192,7 @@ public func takeTrivialInout(_ x: inout Trivial) {
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 // CHECK-EMPTY:
-// CHECK-NEXT: namespace UseCxxTy __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("UseCxxTy") {
+// CHECK-NEXT: namespace UseCxxTy SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("UseCxxTy") {
 
 // CHECK: SWIFT_INLINE_THUNK ns::NonTrivialTemplate<int> retNonTrivial() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: alignas(alignof(ns::NonTrivialTemplate<int>)) char storage[sizeof(ns::NonTrivialTemplate<int>)];
@@ -231,7 +231,7 @@ public func takeTrivialInout(_ x: inout Trivial) {
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 // CHECK-EMPTY:
-// CHECK-NEXT: namespace UseCxxTy __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("UseCxxTy") {
+// CHECK-NEXT: namespace UseCxxTy SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("UseCxxTy") {
 // CHECK-EMPTY:
 // CHECK-NEXT: SWIFT_INLINE_THUNK ns::NonTrivialTemplate<ns::TrivialinNS> retNonTrivial2() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: alignas(alignof(ns::NonTrivialTemplate<ns::TrivialinNS>)) char storage[sizeof(ns::NonTrivialTemplate<ns::TrivialinNS>)];
diff --git a/test/Interop/SwiftToCxx/class/swift-actor-in-cxx.swift b/test/Interop/SwiftToCxx/class/swift-actor-in-cxx.swift
index e3f04d847f8..d002764373c 100644
--- a/test/Interop/SwiftToCxx/class/swift-actor-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/class/swift-actor-in-cxx.swift
@@ -30,7 +30,7 @@ public final actor ActorWithField {
   }
 }
 
-// CHECK: namespace Actor __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Actor") {
+// CHECK: namespace Actor SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Actor") {
 // CHECK: SWIFT_EXTERN void * _Nonnull $s5Actor0A9WithFieldCACycfC(SWIFT_CONTEXT void * _Nonnull _self) SWIFT_NOEXCEPT SWIFT_CALL; // init()
 // CHECK: SWIFT_EXTERN void $s5Actor0A9WithFieldC6methodyyF(SWIFT_CONTEXT void * _Nonnull _self) SWIFT_NOEXCEPT SWIFT_CALL; // method()
 
diff --git a/test/Interop/SwiftToCxx/class/swift-class-in-cxx.swift b/test/Interop/SwiftToCxx/class/swift-class-in-cxx.swift
index 2b369100e8b..587cf241fe5 100644
--- a/test/Interop/SwiftToCxx/class/swift-class-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/class/swift-class-in-cxx.swift
@@ -21,14 +21,14 @@ public final class ClassWithIntField {
   }
 }
 
-// CHECK: namespace Class __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Class") {
+// CHECK: namespace Class SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Class") {
 
 // CHECK: SWIFT_EXTERN void * _Nonnull $s5Class011passThroughA12WithIntFieldyAA0adeF0CADF(void * _Nonnull x) SWIFT_NOEXCEPT SWIFT_CALL; // passThroughClassWithIntField(_:)
 // CHECK-NEXT: SWIFT_EXTERN void * _Nonnull $s5Class06returnA12WithIntFieldAA0acdE0CyF(void) SWIFT_NOEXCEPT SWIFT_CALL; // returnClassWithIntField()
 // CHECK-NEXT: SWIFT_EXTERN void $s5Class04takeA12WithIntFieldyyAA0acdE0CF(void * _Nonnull x) SWIFT_NOEXCEPT SWIFT_CALL; // takeClassWithIntField(_:)
 // CHECK-NEXT: SWIFT_EXTERN void $s5Class04takeA17WithIntFieldInoutyyAA0acdE0CzF(void * _Nonnull * _Nonnull x) SWIFT_NOEXCEPT SWIFT_CALL; // takeClassWithIntFieldInout(_:)
 
-// CHECK: namespace Class __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Class") {
+// CHECK: namespace Class SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Class") {
 
 // CHECK: class SWIFT_SYMBOL("s:5Class0A12WithIntFieldC") ClassWithIntField;
 // CHECK-NEXT: } // end namespace
@@ -43,7 +43,7 @@ public final class ClassWithIntField {
 // CHECK-NEXT: } // namespace swift
 
 // CHECK: namespace
-// CHECK-SAME: Class __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Class") {
+// CHECK-SAME: Class SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Class") {
 
 // CHECK: namespace
 // CHECK-SAME: _impl {
@@ -100,7 +100,7 @@ public final class ClassWithIntField {
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 // CHECK-EMPTY:
-// CHECK-NEXT: namespace Class __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Class") {
+// CHECK-NEXT: namespace Class SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Class") {
 
 // CHECK: SWIFT_INLINE_THUNK ClassWithIntField passThroughClassWithIntField(const ClassWithIntField& x) noexcept SWIFT_SYMBOL("s:5Class011passThroughA12WithIntFieldyAA0adeF0CADF") SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT:  return _impl::_impl_ClassWithIntField::makeRetained(_impl::$s5Class011passThroughA12WithIntFieldyAA0adeF0CADF(::swift::_impl::_impl_RefCountedClass::getOpaquePointer(x)));
diff --git a/test/Interop/SwiftToCxx/core/gen-header-for-module.swift b/test/Interop/SwiftToCxx/core/gen-header-for-module.swift
index 24e4c1ff20b..fe17c0f52be 100644
--- a/test/Interop/SwiftToCxx/core/gen-header-for-module.swift
+++ b/test/Interop/SwiftToCxx/core/gen-header-for-module.swift
@@ -22,5 +22,5 @@ public func reprintedInImportedModule() -> Int {
     return 42
 }
 
-// CHECK: namespace Core __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Core") {
+// CHECK: namespace Core SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Core") {
 // CHECK: swift::Int reprintedInImportedModule() noexcept SWIFT_SYMBOL("s:4Core25reprintedInImportedModuleSiyF") SWIFT_WARN_UNUSED_RESULT {
diff --git a/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx-64-bit.swift b/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx-64-bit.swift
index 39d47ee040d..2f4ba8fb73b 100644
--- a/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx-64-bit.swift
+++ b/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx-64-bit.swift
@@ -6,7 +6,7 @@
 
 // REQUIRES: PTRSIZE=64
 
-// CHECK: namespace swift {
+// CHECK: namespace swift SWIFT_PRIVATE_ATTR {
 
 // CHECK: namespace _impl {
 
diff --git a/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx.swift b/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx.swift
index aec1bbef04e..d4e6c963754 100644
--- a/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/core/swift-impl-defs-in-cxx.swift
@@ -7,7 +7,7 @@
 
 // CHECK:      #ifndef SWIFT_PRINTED_CORE
 // CHECK-NEXT: #define SWIFT_PRINTED_CORE
-// CHECK-NEXT: namespace swift {
+// CHECK-NEXT: namespace swift SWIFT_PRIVATE_ATTR {
 // CHECK-EMPTY:
 // CHECK-NEXT: namespace _impl {
 // CHECK-EMPTY:
diff --git a/test/Interop/SwiftToCxx/enums/swift-enum-implementation.swift b/test/Interop/SwiftToCxx/enums/swift-enum-implementation.swift
index 2654995033a..fef353a7c7d 100644
--- a/test/Interop/SwiftToCxx/enums/swift-enum-implementation.swift
+++ b/test/Interop/SwiftToCxx/enums/swift-enum-implementation.swift
@@ -166,7 +166,7 @@ public struct S {
 // CHECK-NEXT: #endif
 // CHECK-NEXT:     vwTable->initializeWithTake(destStorage, srcStorage, metadata._0);
 // CHECK-NEXT:   }
-// CHECK:      namespace Enums __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Enums") {
+// CHECK:      namespace Enums SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Enums") {
 // CHECK:        SWIFT_INLINE_THUNK E E::_impl_x::operator()(double val) const {
 // CHECK-NEXT:     auto result = E::_make();
 // CHECK-NEXT:     memcpy(result._getOpaquePointer(), &val, sizeof(val));
diff --git a/test/Interop/SwiftToCxx/enums/zero-sized-enum-in-cxx.swift b/test/Interop/SwiftToCxx/enums/zero-sized-enum-in-cxx.swift
index a296082e0f0..b657234b8fb 100644
--- a/test/Interop/SwiftToCxx/enums/zero-sized-enum-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/enums/zero-sized-enum-in-cxx.swift
@@ -5,7 +5,7 @@
 public enum EmptyEnum {}
 public enum SingleCaseEnum { case first }
 
-// CHECK: namespace Enums __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Enums") {
+// CHECK: namespace Enums SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Enums") {
 // CHECK-NOT: EmptyEnum final {
 // CHECK-NOT: SingleCaseEnum final {
 // CHECK: } // namespace Enums
diff --git a/test/Interop/SwiftToCxx/functions/PrintAsCxx/function_with_array.swift b/test/Interop/SwiftToCxx/functions/PrintAsCxx/function_with_array.swift
index 3a891e411e7..41454fffad6 100644
--- a/test/Interop/SwiftToCxx/functions/PrintAsCxx/function_with_array.swift
+++ b/test/Interop/SwiftToCxx/functions/PrintAsCxx/function_with_array.swift
@@ -5,5 +5,5 @@
 // CHECK: namespace function_with_array
 // FIXME: we don't actually emit a declaration for this, but for now at least
 // check that we don't crash.
-// CHECK: void f(const Swift::Array<swift::Int>&
+// CHECK: void f(const swift::Array<swift::Int>&
 public func f(_: [Int]) { }
diff --git a/test/Interop/SwiftToCxx/functions/cdecl.swift b/test/Interop/SwiftToCxx/functions/cdecl.swift
index 71f41cd3cdd..87739ffbe7d 100644
--- a/test/Interop/SwiftToCxx/functions/cdecl.swift
+++ b/test/Interop/SwiftToCxx/functions/cdecl.swift
@@ -4,7 +4,7 @@
 
 // RUN: %check-interop-cxx-header-in-clang(%t/cdecl.h)
 
-// CHECK-LABEL: namespace CdeclFunctions __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("CdeclFunctions") {
+// CHECK-LABEL: namespace CdeclFunctions SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("CdeclFunctions") {
 
 // CHECK: namespace _impl {
 // CHECK: SWIFT_EXTERN int cfuncPassTwo(int x, int y) SWIFT_NOEXCEPT;
diff --git a/test/Interop/SwiftToCxx/functions/function-availability.swift b/test/Interop/SwiftToCxx/functions/function-availability.swift
index 5477757a32c..5527c2aca6e 100644
--- a/test/Interop/SwiftToCxx/functions/function-availability.swift
+++ b/test/Interop/SwiftToCxx/functions/function-availability.swift
@@ -4,7 +4,7 @@
 
 // RUN: %check-interop-cxx-header-in-clang(%t/functions.h)
 
-// CHECK-LABEL: namespace Functions __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Functions") {
+// CHECK-LABEL: namespace Functions SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Functions") {
 
 // CHECK-LABEL: namespace _impl {
 
diff --git a/test/Interop/SwiftToCxx/functions/swift-expected-execution.cpp b/test/Interop/SwiftToCxx/functions/swift-expected-execution.cpp
index c8c65d91212..b301c277fd0 100644
--- a/test/Interop/SwiftToCxx/functions/swift-expected-execution.cpp
+++ b/test/Interop/SwiftToCxx/functions/swift-expected-execution.cpp
@@ -22,14 +22,14 @@
 int main() {
 
   // Test Empty Constructor
-  auto testIntEmpty = Swift::Expected<int>();
+  auto testIntEmpty = swift::Expected<int>();
 
   // Test Error Constructor
-  Swift::Error e;
-  auto testIntError = Swift::Expected<int>(e);
+  swift::Error e;
+  auto testIntError = swift::Expected<int>(e);
 
   // Test Value Constructor
-  auto testIntValue = Swift::Expected<int>(42);
+  auto testIntValue = swift::Expected<int>(42);
 
   // Test Copy Constructor
   auto testCopy = testIntEmpty;
@@ -37,9 +37,9 @@ int main() {
   // TODO: Test Move Constructor
 
   // Test Destructor
-  auto testDestEmpty = Swift::Expected<int>();
-  auto testDestInt = Swift::Expected<int>(42);
-  auto testDestError = Swift::Expected<int>(e);
+  auto testDestEmpty = swift::Expected<int>();
+  auto testDestInt = swift::Expected<int>(42);
+  auto testDestError = swift::Expected<int>(e);
   testDestEmpty.~Expected();
   testDestInt.~Expected();
   testDestError.~Expected();
diff --git a/test/Interop/SwiftToCxx/functions/swift-functions-errors-execution.cpp b/test/Interop/SwiftToCxx/functions/swift-functions-errors-execution.cpp
index 8a9a4483653..24d233db148 100644
--- a/test/Interop/SwiftToCxx/functions/swift-functions-errors-execution.cpp
+++ b/test/Interop/SwiftToCxx/functions/swift-functions-errors-execution.cpp
@@ -28,12 +28,12 @@ int main() {
 
   try {
     Functions::emptyThrowFunction();
-  } catch (Swift::Error& e) {
+  } catch (swift::Error& e) {
     printf("Exception\n");
   }
   try {
     Functions::throwFunction();
-  } catch (Swift::Error& e) {
+  } catch (swift::Error& e) {
       auto errorOpt = e.as<Functions::NaiveErrors>();
       assert(errorOpt.isSome());
 
@@ -43,12 +43,12 @@ int main() {
   }
   try {
     Functions::throwFunctionWithReturn();
-  } catch (Swift::Error& e) {
+  } catch (swift::Error& e) {
      printf("Exception\n");
   }
   try {
     Functions::testDestroyedError();
-  } catch(const Swift::Error &e) { }
+  } catch(const swift::Error &e) { }
 
   return 0;
 }
diff --git a/test/Interop/SwiftToCxx/functions/swift-functions-errors.swift b/test/Interop/SwiftToCxx/functions/swift-functions-errors.swift
index b2fcba488df..903ba15ef7e 100644
--- a/test/Interop/SwiftToCxx/functions/swift-functions-errors.swift
+++ b/test/Interop/SwiftToCxx/functions/swift-functions-errors.swift
@@ -7,7 +7,7 @@
 // for experimental feature GenerateBindingsForThrowingFunctionsInCXX:
 // REQUIRES: asserts
 
-// CHECK-LABEL: namespace Functions __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Functions") {
+// CHECK-LABEL: namespace Functions SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Functions") {
 
 // CHECK-LABEL: namespace _impl {
 
@@ -33,15 +33,15 @@ public enum NaiveErrors : Error {
 @_expose(Cxx)
 public func emptyThrowFunction() throws { print("passEmptyThrowFunction") }
 
-// CHECK: SWIFT_INLINE_THUNK Swift::ThrowingResult<void> emptyThrowFunction() SWIFT_SYMBOL("s:9Functions18emptyThrowFunctionyyKF") {
+// CHECK: SWIFT_INLINE_THUNK swift::ThrowingResult<void> emptyThrowFunction() SWIFT_SYMBOL("s:9Functions18emptyThrowFunctionyyKF") {
 // CHECK: void* opaqueError = nullptr;
 // CHECK: void* _ctx = nullptr;
 // CHECK: _impl::$s9Functions18emptyThrowFunctionyyKF(_ctx, &opaqueError);
 // CHECK: if (opaqueError != nullptr)
 // CHECK: #ifdef __cpp_exceptions
-// CHECK: throw (Swift::Error(opaqueError));
+// CHECK: throw (swift::Error(opaqueError));
 // CHECK: #else
-// CHECK: return Swift::Expected<void>(Swift::Error(opaqueError));
+// CHECK: return swift::Expected<void>(swift::Error(opaqueError));
 // CHECK: #endif
 // CHECK: }
 
@@ -59,15 +59,15 @@ public struct DestroyedError : Error {
 @_expose(Cxx)
 public func testDestroyedError() throws { throw DestroyedError() }
 
-// CHECK: SWIFT_INLINE_THUNK Swift::ThrowingResult<void> testDestroyedError() SWIFT_SYMBOL("s:9Functions18testDestroyedErroryyKF") {
+// CHECK: SWIFT_INLINE_THUNK swift::ThrowingResult<void> testDestroyedError() SWIFT_SYMBOL("s:9Functions18testDestroyedErroryyKF") {
 // CHECK: void* opaqueError = nullptr;
 // CHECK: void* _ctx = nullptr;
 // CHECK: _impl::$s9Functions18testDestroyedErroryyKF(_ctx, &opaqueError);
 // CHECK: if (opaqueError != nullptr)
 // CHECK: #ifdef __cpp_exceptions
-// CHECK: throw (Swift::Error(opaqueError));
+// CHECK: throw (swift::Error(opaqueError));
 // CHECK: #else
-// CHECK: return Swift::Expected<void>(Swift::Error(opaqueError));
+// CHECK: return swift::Expected<void>(swift::Error(opaqueError));
 // CHECK: #endif
 // CHECK: }
 
@@ -77,15 +77,15 @@ public func throwFunction() throws {
     throw NaiveErrors.throwError
 }
 
-// CHECK: SWIFT_INLINE_THUNK Swift::ThrowingResult<void> throwFunction() SWIFT_SYMBOL("s:9Functions13throwFunctionyyKF") {
+// CHECK: SWIFT_INLINE_THUNK swift::ThrowingResult<void> throwFunction() SWIFT_SYMBOL("s:9Functions13throwFunctionyyKF") {
 // CHECK: void* opaqueError = nullptr;
 // CHECK: void* _ctx = nullptr;
 // CHECK: _impl::$s9Functions13throwFunctionyyKF(_ctx, &opaqueError);
 // CHECK: if (opaqueError != nullptr)
 // CHECK: #ifdef __cpp_exceptions
-// CHECK: throw (Swift::Error(opaqueError));
+// CHECK: throw (swift::Error(opaqueError));
 // CHECK: #else
-// CHECK: return Swift::Expected<void>(Swift::Error(opaqueError));
+// CHECK: return swift::Expected<void>(swift::Error(opaqueError));
 // CHECK: #endif
 // CHECK: }
 
@@ -98,15 +98,15 @@ public func throwFunctionWithPossibleReturn(_ a: Int) throws -> Int {
     return 0
 }
 
-// CHECK: SWIFT_INLINE_THUNK Swift::ThrowingResult<swift::Int> throwFunctionWithPossibleReturn(swift::Int a) SWIFT_SYMBOL("s:9Functions31throwFunctionWithPossibleReturnyS2iKF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK: SWIFT_INLINE_THUNK swift::ThrowingResult<swift::Int> throwFunctionWithPossibleReturn(swift::Int a) SWIFT_SYMBOL("s:9Functions31throwFunctionWithPossibleReturnyS2iKF") SWIFT_WARN_UNUSED_RESULT {
 // CHECK: void* opaqueError = nullptr;
 // CHECK: void* _ctx = nullptr;
 // CHECK: auto returnValue = _impl::$s9Functions31throwFunctionWithPossibleReturnyS2iKF(a, _ctx, &opaqueError);
 // CHECK: if (opaqueError != nullptr)
 // CHECK: #ifdef __cpp_exceptions
-// CHECK: throw (Swift::Error(opaqueError));
+// CHECK: throw (swift::Error(opaqueError));
 // CHECK: #else
-// CHECK: return Swift::Expected<swift::Int>(Swift::Error(opaqueError));
+// CHECK: return swift::Expected<swift::Int>(swift::Error(opaqueError));
 // CHECK: #endif
 // CHECK: return SWIFT_RETURN_THUNK(swift::Int, returnValue);
 // CHECK: }
@@ -118,14 +118,14 @@ public func throwFunctionWithReturn() throws -> Int {
     return 0
 }
 
-// CHECK: SWIFT_INLINE_THUNK Swift::ThrowingResult<swift::Int> throwFunctionWithReturn() SWIFT_SYMBOL("s:9Functions23throwFunctionWithReturnSiyKF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK: SWIFT_INLINE_THUNK swift::ThrowingResult<swift::Int> throwFunctionWithReturn() SWIFT_SYMBOL("s:9Functions23throwFunctionWithReturnSiyKF") SWIFT_WARN_UNUSED_RESULT {
 // CHECK: void* opaqueError = nullptr;
 // CHECK: void* _ctx = nullptr;
 // CHECK: auto returnValue = _impl::$s9Functions23throwFunctionWithReturnSiyKF(_ctx, &opaqueError);
 // CHECK: #ifdef __cpp_exceptions
-// CHECK: throw (Swift::Error(opaqueError));
+// CHECK: throw (swift::Error(opaqueError));
 // CHECK: #else
-// CHECK: return Swift::Expected<swift::Int>(Swift::Error(opaqueError));
+// CHECK: return swift::Expected<swift::Int>(swift::Error(opaqueError));
 // CHECK: #endif
 // CHECK: return SWIFT_RETURN_THUNK(swift::Int, returnValue);
 // CHECK: }
diff --git a/test/Interop/SwiftToCxx/functions/swift-functions.swift b/test/Interop/SwiftToCxx/functions/swift-functions.swift
index fadccdf25e3..ee35dd57a2c 100644
--- a/test/Interop/SwiftToCxx/functions/swift-functions.swift
+++ b/test/Interop/SwiftToCxx/functions/swift-functions.swift
@@ -4,7 +4,7 @@
 
 // RUN: %check-interop-cxx-header-in-clang(%t/functions.h)
 
-// CHECK-LABEL: namespace Functions __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Functions") {
+// CHECK-LABEL: namespace Functions SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Functions") {
 
 // CHECK-LABEL: namespace _impl {
 
diff --git a/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-alwaysEmitInClient-func.swift b/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-alwaysEmitInClient-func.swift
index a999b4a715d..8764091f5c7 100644
--- a/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-alwaysEmitInClient-func.swift
+++ b/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-alwaysEmitInClient-func.swift
@@ -6,7 +6,7 @@
 
 // CHECK-NOT: SWIFT_EXTERN bool $s9Functions24alwaysEmitIntoClientFuncyS2bF(bool x) SWIFT_NOEXCEPT SWIFT_CALL; // alwaysEmitIntoClientFunc(_:)
 
-// CHECK:       namespace Functions __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Functions") {
+// CHECK:       namespace Functions SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Functions") {
 // CHECK-EMPTY:
 // CHECK-EMPTY:
 // CHECK-NEXT:  } // namespace Functions
diff --git a/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-async-func.swift b/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-async-func.swift
index 43edacf9c5a..3125d8c2be5 100644
--- a/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-async-func.swift
+++ b/test/Interop/SwiftToCxx/functions/swift-no-expose-unsupported-async-func.swift
@@ -6,7 +6,7 @@
 
 // CHECK-NOT: SWIFT_EXTERN double $s9Functions9asyncFuncyS2dYaF(double x) SWIFT_NOEXCEPT SWIFT_CALL; // asyncFunc(_:)
 
-// CHECK:       namespace Functions __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Functions") {
+// CHECK:       namespace Functions SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Functions") {
 // CHECK-EMPTY:
 // CHECK-EMPTY:
 // CHECK-NEXT:  } // namespace Functions
diff --git a/test/Interop/SwiftToCxx/generics/generic-type-traits-fwd.swift b/test/Interop/SwiftToCxx/generics/generic-type-traits-fwd.swift
index 6a44e573130..664d9f9cbc5 100644
--- a/test/Interop/SwiftToCxx/generics/generic-type-traits-fwd.swift
+++ b/test/Interop/SwiftToCxx/generics/generic-type-traits-fwd.swift
@@ -39,7 +39,7 @@ public struct LaterGeneric<T> {
 // CHECK: class SWIFT_SYMBOL("s:8Generics14ComesFirstEnumO") ComesFirstEnum final {
 // CHECK: LaterGeneric<ComesFirstEnum> returnsLaterOpt() const SWIFT_SYMBOL("s:8Generics14ComesFirstEnumO15returnsLaterOptAA0F7GenericVyACGyF");
 
-// CHECK: namespace Generics __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Generics") {
+// CHECK: namespace Generics SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Generics") {
 // CHECK-EMPTY:
 // CHECK-NEXT:  namespace _impl {
 // CHECK-EMPTY:
diff --git a/test/Interop/SwiftToCxx/module/module-to-namespace.swift b/test/Interop/SwiftToCxx/module/module-to-namespace.swift
index b910d62b709..3b6a97a1bc4 100644
--- a/test/Interop/SwiftToCxx/module/module-to-namespace.swift
+++ b/test/Interop/SwiftToCxx/module/module-to-namespace.swift
@@ -9,7 +9,7 @@
 // CHECK-NEXT: #endif
 // CHECK-NEXT: #define SWIFT_SYMBOL(usrValue) SWIFT_SYMBOL_MODULE_USR("Test", usrValue)
 
-// CHECK-LABEL: namespace Test __attribute__((swift_private)) SWIFT_SYMBOL_MODULE({{.*}}) {
+// CHECK-LABEL: namespace Test SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE({{.*}}) {
 // CHECK:       } // namespace Test
 // CHECK-EMPTY:
 // CHECK-NEXT: #undef SWIFT_SYMBOL
diff --git a/test/Interop/SwiftToCxx/stdlib/array/array-execution.cpp b/test/Interop/SwiftToCxx/stdlib/array/array-execution.cpp
index 795c8a3f523..67ed7e35d96 100644
--- a/test/Interop/SwiftToCxx/stdlib/array/array-execution.cpp
+++ b/test/Interop/SwiftToCxx/stdlib/array/array-execution.cpp
@@ -32,7 +32,7 @@ public func printArray(_ val: Array<CInt>) {
 #include "UseArray.h"
 
 int main() {
-  using namespace Swift;
+  using namespace swift;
 
   {
     Array<int> val = UseArray::createArray(2);
diff --git a/test/Interop/SwiftToCxx/stdlib/optional/optional-execution.cpp b/test/Interop/SwiftToCxx/stdlib/optional/optional-execution.cpp
index ba11203f004..4ad21ef8113 100644
--- a/test/Interop/SwiftToCxx/stdlib/optional/optional-execution.cpp
+++ b/test/Interop/SwiftToCxx/stdlib/optional/optional-execution.cpp
@@ -78,7 +78,7 @@ public func resetOpt<T>(_ val: inout Optional<T>) {
 #include "UseOptional.h"
 
 int main() {
-  using namespace Swift;
+  using namespace swift;
   using namespace UseOptional;
 
   {
diff --git a/test/Interop/SwiftToCxx/stdlib/optional/optional-in-cxx.swift b/test/Interop/SwiftToCxx/stdlib/optional/optional-in-cxx.swift
index 296801266f3..0b6c32f8450 100644
--- a/test/Interop/SwiftToCxx/stdlib/optional/optional-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/stdlib/optional/optional-in-cxx.swift
@@ -54,21 +54,21 @@ public func resetOpt<T>(_ val: inout Optional<T>) {
 }
 
 
-// CHECK: SWIFT_INLINE_THUNK Swift::Optional<int> createCIntOpt(int val) noexcept SWIFT_SYMBOL("s:11UseOptional13createCIntOptys5Int32VSgADF") SWIFT_WARN_UNUSED_RESULT {
- // CHECK-NEXT: return Swift::_impl::_impl_Optional<int>::returnNewValue([&](char * _Nonnull result) SWIFT_INLINE_THUNK_ATTRIBUTES {
+// CHECK: SWIFT_INLINE_THUNK swift::Optional<int> createCIntOpt(int val) noexcept SWIFT_SYMBOL("s:11UseOptional13createCIntOptys5Int32VSgADF") SWIFT_WARN_UNUSED_RESULT {
+ // CHECK-NEXT: return swift::_impl::_impl_Optional<int>::returnNewValue([&](char * _Nonnull result) SWIFT_INLINE_THUNK_ATTRIBUTES {
 // CHECK-NEXT:   _impl::swift_interop_returnDirect_UseOptional_[[CINTENC:[a-z0-9_]+]](result, _impl::$s11UseOptional13createCIntOptys5Int32VSgADF(val));
 // CHECK-NEXT: });
 // CHECK-NEXT: }
 
 
-// CHECK: SWIFT_INLINE_THUNK Swift::Optional<Klass> createKlassOpt(int16_t val) noexcept SWIFT_SYMBOL("s:11UseOptional14createKlassOptyAA0D0CSgs5Int16VF") SWIFT_WARN_UNUSED_RESULT {
-// CHECK-NEXT:   return Swift::_impl::_impl_Optional<Klass>::returnNewValue([&](char * _Nonnull result) SWIFT_INLINE_THUNK_ATTRIBUTES {
+// CHECK: SWIFT_INLINE_THUNK swift::Optional<Klass> createKlassOpt(int16_t val) noexcept SWIFT_SYMBOL("s:11UseOptional14createKlassOptyAA0D0CSgs5Int16VF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-NEXT:   return swift::_impl::_impl_Optional<Klass>::returnNewValue([&](char * _Nonnull result) SWIFT_INLINE_THUNK_ATTRIBUTES {
 // CHECK-NEXT: _impl::swift_interop_returnDirect_UseOptional_[[CLASSENC:[a-z0-9_]+]](result, _impl::$s11UseOptional14createKlassOptyAA0D0CSgs5Int16VF(val));
 // CHECK-NEXT:   });
 // CHECK-NEXT: }
 
-// CHECK: SWIFT_INLINE_THUNK Swift::Optional<SmallStruct> createSmallStructOpt(int16_t val) noexcept SWIFT_SYMBOL("s:11UseOptional20createSmallStructOptyAA0dE0VSgs5Int16VF") SWIFT_WARN_UNUSED_RESULT {
-// CHECK-NEXT:   return Swift::_impl::_impl_Optional<SmallStruct>::returnNewValue([&](char * _Nonnull result) SWIFT_INLINE_THUNK_ATTRIBUTES {
+// CHECK: SWIFT_INLINE_THUNK swift::Optional<SmallStruct> createSmallStructOpt(int16_t val) noexcept SWIFT_SYMBOL("s:11UseOptional20createSmallStructOptyAA0dE0VSgs5Int16VF") SWIFT_WARN_UNUSED_RESULT {
+// CHECK-NEXT:   return swift::_impl::_impl_Optional<SmallStruct>::returnNewValue([&](char * _Nonnull result) SWIFT_INLINE_THUNK_ATTRIBUTES {
 // CHECK-NEXT:     _impl::swift_interop_returnDirect_UseOptional_uint32_t_0_4(result, _impl::$s11UseOptional20createSmallStructOptyAA0dE0VSgs5Int16VF(val));
 // CHECK-NEXT:   });
 // CHECK-NEXT: }
@@ -78,24 +78,24 @@ public func resetOpt<T>(_ val: inout Optional<T>) {
 // CHECK-NEXT: #ifdef __cpp_concepts
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T_0_0>
 // CHECK-NEXT: #endif
-// CHECK-NEXT: SWIFT_INLINE_THUNK void resetOpt(Swift::Optional<T_0_0>& val) noexcept SWIFT_SYMBOL("s:11UseOptional8resetOptyyxSgzlF") {
+// CHECK-NEXT: SWIFT_INLINE_THUNK void resetOpt(swift::Optional<T_0_0>& val) noexcept SWIFT_SYMBOL("s:11UseOptional8resetOptyyxSgzlF") {
 // CHECK-NEXT: #ifndef __cpp_concepts
 // CHECK-NEXT: static_assert(swift::isUsableInGenericContext<T_0_0>, "type cannot be used in a Swift generic context");
 // CHECK-NEXT: #endif
-// CHECK-NEXT:   return _impl::$s11UseOptional8resetOptyyxSgzlF(Swift::_impl::_impl_Optional<T_0_0>::getOpaquePointer(val), swift::TypeMetadataTrait<T_0_0>::getTypeMetadata());
+// CHECK-NEXT:   return _impl::$s11UseOptional8resetOptyyxSgzlF(swift::_impl::_impl_Optional<T_0_0>::getOpaquePointer(val), swift::TypeMetadataTrait<T_0_0>::getTypeMetadata());
 // CHECK-NEXT: }
 
 
-// CHECK: SWIFT_INLINE_THUNK void takeCIntOpt(const Swift::Optional<int>& val) noexcept SWIFT_SYMBOL("s:11UseOptional11takeCIntOptyys5Int32VSgF") {
-// CHECK-NEXT:  return _impl::$s11UseOptional11takeCIntOptyys5Int32VSgF(_impl::swift_interop_passDirect_UseOptional_[[CINTENC]](Swift::_impl::_impl_Optional<int>::getOpaquePointer(val)));
+// CHECK: SWIFT_INLINE_THUNK void takeCIntOpt(const swift::Optional<int>& val) noexcept SWIFT_SYMBOL("s:11UseOptional11takeCIntOptyys5Int32VSgF") {
+// CHECK-NEXT:  return _impl::$s11UseOptional11takeCIntOptyys5Int32VSgF(_impl::swift_interop_passDirect_UseOptional_[[CINTENC]](swift::_impl::_impl_Optional<int>::getOpaquePointer(val)));
 // CHECK-NEXT: }
 
 
-// CHECK: SWIFT_INLINE_THUNK void takeKlassOpt(const Swift::Optional<Klass>& val) noexcept SWIFT_SYMBOL("s:11UseOptional12takeKlassOptyyAA0D0CSgF") {
-// CHECK-NEXT:   return _impl::$s11UseOptional12takeKlassOptyyAA0D0CSgF(_impl::swift_interop_passDirect_UseOptional_[[CLASSENC]](Swift::_impl::_impl_Optional<Klass>::getOpaquePointer(val)));
+// CHECK: SWIFT_INLINE_THUNK void takeKlassOpt(const swift::Optional<Klass>& val) noexcept SWIFT_SYMBOL("s:11UseOptional12takeKlassOptyyAA0D0CSgF") {
+// CHECK-NEXT:   return _impl::$s11UseOptional12takeKlassOptyyAA0D0CSgF(_impl::swift_interop_passDirect_UseOptional_[[CLASSENC]](swift::_impl::_impl_Optional<Klass>::getOpaquePointer(val)));
 // CHECK-NEXT: }
 
 
-// CHECK: SWIFT_INLINE_THUNK void takeSmallStructOpt(const Swift::Optional<SmallStruct>& val) noexcept SWIFT_SYMBOL("s:11UseOptional18takeSmallStructOptyyAA0dE0VSgF") {
-// CHECK-NEXT:  return _impl::$s11UseOptional18takeSmallStructOptyyAA0dE0VSgF(_impl::swift_interop_passDirect_UseOptional_uint32_t_0_4(Swift::_impl::_impl_Optional<SmallStruct>::getOpaquePointer(val)));
+// CHECK: SWIFT_INLINE_THUNK void takeSmallStructOpt(const swift::Optional<SmallStruct>& val) noexcept SWIFT_SYMBOL("s:11UseOptional18takeSmallStructOptyyAA0dE0VSgF") {
+// CHECK-NEXT:  return _impl::$s11UseOptional18takeSmallStructOptyyAA0dE0VSgF(_impl::swift_interop_passDirect_UseOptional_uint32_t_0_4(swift::_impl::_impl_Optional<SmallStruct>::getOpaquePointer(val)));
 // CHECK-NEXT: }
diff --git a/test/Interop/SwiftToCxx/stdlib/stdlib-dep-inline-in-cxx.swift b/test/Interop/SwiftToCxx/stdlib/stdlib-dep-inline-in-cxx.swift
index bb0a90a2f97..78c99508106 100644
--- a/test/Interop/SwiftToCxx/stdlib/stdlib-dep-inline-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/stdlib/stdlib-dep-inline-in-cxx.swift
@@ -17,5 +17,5 @@ public func test() -> String {
     return ""
 }
 
-// CHECK: namespace Swift __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Swift") {
+// CHECK: namespace swift SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("swift") {
 // CHECK: class SWIFT_SYMBOL("{{.*}}") String final {
diff --git a/test/Interop/SwiftToCxx/stdlib/string/string-conversions.cpp b/test/Interop/SwiftToCxx/stdlib/string/string-conversions.cpp
index 6378144ac11..ca455aca557 100644
--- a/test/Interop/SwiftToCxx/stdlib/string/string-conversions.cpp
+++ b/test/Interop/SwiftToCxx/stdlib/string/string-conversions.cpp
@@ -28,7 +28,7 @@ public func makeString(_ s: String, _ y: String) -> String {
 #include "Stringer.h"
 
 int main() {
-  using namespace Swift;
+  using namespace swift;
   using namespace Stringer;
 
   {
diff --git a/test/Interop/SwiftToCxx/stdlib/string/string-in-cxx-execution.cpp b/test/Interop/SwiftToCxx/stdlib/string/string-in-cxx-execution.cpp
index c0bde3300a8..8064c4d8cae 100644
--- a/test/Interop/SwiftToCxx/stdlib/string/string-in-cxx-execution.cpp
+++ b/test/Interop/SwiftToCxx/stdlib/string/string-in-cxx-execution.cpp
@@ -23,7 +23,7 @@ public func printString(_ s: String) {
 #include "Stringer.h"
 
 int main() {
-  using namespace Swift;
+  using namespace swift;
   using namespace Stringer;
 
   {
diff --git a/test/Interop/SwiftToCxx/stdlib/string/string-to-nsstring.mm b/test/Interop/SwiftToCxx/stdlib/string/string-to-nsstring.mm
index ef03e8d534e..d947a970c6e 100644
--- a/test/Interop/SwiftToCxx/stdlib/string/string-to-nsstring.mm
+++ b/test/Interop/SwiftToCxx/stdlib/string/string-to-nsstring.mm
@@ -27,7 +27,7 @@ public func createString(_ ptr: UnsafePointer<CChar>) -> String {
 #include "StringCreator.h"
 
 int main() {
-  using namespace Swift;
+  using namespace swift;
   auto emptyString = String::init();
   NSString *nsStr = emptyString;
 }
@@ -45,7 +45,7 @@ int main() {
 #include "StringCreator.h"
 
 int main() {
-  using namespace Swift;
+  using namespace swift;
 
   auto emptyString = String::init();
 
diff --git a/test/Interop/SwiftToCxx/stdlib/swift-stdlib-in-cxx.swift b/test/Interop/SwiftToCxx/stdlib/swift-stdlib-in-cxx.swift
index fd6429ec7e4..1038d50cb8e 100644
--- a/test/Interop/SwiftToCxx/stdlib/swift-stdlib-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/stdlib/swift-stdlib-in-cxx.swift
@@ -4,7 +4,7 @@
 
 // RUN: %check-interop-cxx-header-in-clang(%t/Swift.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY -Wno-unused-private-field -Wno-unused-function -Wc++98-compat-extra-semi)
 
-// CHECK: namespace Swift __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Swift") {
+// CHECK: namespace swift SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("swift") {
 
 // CHECK: template<class T_0_0>
 // CHECK-NEXT: #ifdef __cpp_concepts
@@ -107,7 +107,7 @@
 // CHECK:  SWIFT_INLINE_THUNK UTF8View(UTF8View &&) { abort(); }
 // CHECK-NEXT: SWIFT_INLINE_THUNK String_Index getStartIndex() const SWIFT_SYMBOL({{.*}});
 // CHECK-NEXT:   SWIFT_INLINE_THUNK String_Index getEndIndex() const SWIFT_SYMBOL({{.*}});
-// CHECK:   SWIFT_INLINE_THUNK Swift::Optional<String_Index> indexOffsetByLimitedBy(const String_Index& i, swift::Int n, const String_Index& limit) const SWIFT_SYMBOL({{.*}});
+// CHECK:   SWIFT_INLINE_THUNK swift::Optional<String_Index> indexOffsetByLimitedBy(const String_Index& i, swift::Int n, const String_Index& limit) const SWIFT_SYMBOL({{.*}});
 // CHECK:   SWIFT_INLINE_THUNK swift::Int distanceFromTo(const String_Index& i, const String_Index& j) const SWIFT_SYMBOL({{.*}});
 // CHECK: SWIFT_INLINE_THUNK uint8_t operator [](const String_Index& i) const SWIFT_SYMBOL({{.*}});
 // CHECK:   SWIFT_INLINE_THUNK String getDescription() const SWIFT_SYMBOL({{.*}});
@@ -124,4 +124,4 @@
 // CHECK-NEXT: #include <swiftToCxx/_SwiftStdlibCxxOverlay.h>
 // CHECK-NEXT: #endif
 
-// CHECK: } // namespace Swift
+// CHECK: } // namespace swift
diff --git a/test/Interop/SwiftToCxx/structs/resilient-struct-in-cxx.swift b/test/Interop/SwiftToCxx/structs/resilient-struct-in-cxx.swift
index 801fb4dcbd4..bafdeac7813 100644
--- a/test/Interop/SwiftToCxx/structs/resilient-struct-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/structs/resilient-struct-in-cxx.swift
@@ -100,7 +100,7 @@ public struct FirstSmallStruct {
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 // CHECK-EMPTY:
-// CHECK-NEXT: namespace Structs __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Structs") {
+// CHECK-NEXT: namespace Structs SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Structs") {
 
 @frozen public struct FrozenStruct {
     private let storedInt: Int32
diff --git a/test/Interop/SwiftToCxx/structs/swift-struct-in-cxx.swift b/test/Interop/SwiftToCxx/structs/swift-struct-in-cxx.swift
index 4bdbbe5625f..beb631a42e3 100644
--- a/test/Interop/SwiftToCxx/structs/swift-struct-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/structs/swift-struct-in-cxx.swift
@@ -4,10 +4,10 @@
 
 // RUN: %check-interop-cxx-header-in-clang(%t/structs.h -Wno-unused-private-field -Wno-unused-function)
 
-// CHECK: namespace Structs __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Structs") {
+// CHECK: namespace Structs SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Structs") {
 // CHECK: namespace _impl {
 
-// CHECK: namespace Structs __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Structs") {
+// CHECK: namespace Structs SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Structs") {
 
 // CHECK: class SWIFT_SYMBOL("s:7Structs18StructWithIntFieldV") StructWithIntField;
 // CHECK-NEXT: } // end namespace
@@ -20,7 +20,7 @@
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 
-// CHECK: namespace Structs __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Structs") {
+// CHECK: namespace Structs SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Structs") {
 
 // CHECK:      namespace _impl {
 // CHECK-EMPTY:
@@ -103,7 +103,7 @@
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 // CHECK-EMPTY:
-// CHECK-NEXT: namespace Structs __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Structs") {
+// CHECK-NEXT: namespace Structs SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Structs") {
 
 public struct StructWithIntField {
   let field: Int64
diff --git a/test/Interop/SwiftToCxx/structs/zero-sized-struct-in-cxx.swift b/test/Interop/SwiftToCxx/structs/zero-sized-struct-in-cxx.swift
index 6b47d5bdf28..a49f84f5fca 100644
--- a/test/Interop/SwiftToCxx/structs/zero-sized-struct-in-cxx.swift
+++ b/test/Interop/SwiftToCxx/structs/zero-sized-struct-in-cxx.swift
@@ -2,7 +2,7 @@
 // RUN: %target-swift-frontend %s -typecheck -module-name Structs -clang-header-expose-decls=all-public -emit-clang-header-path %t/structs.h
 // RUN: %FileCheck %s < %t/structs.h
 
-// CHECK: namespace Structs __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Structs") {
+// CHECK: namespace Structs SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("Structs") {
 
 // CHECK-NOT: class SWIFT_SYMBOL({{.*}}) ZeroSizedStruct final {
 
diff --git a/test/Interop/SwiftToCxxToSwift/hide-swift-module-namespace-in-swift.swift b/test/Interop/SwiftToCxxToSwift/hide-swift-module-namespace-in-swift.swift
index 713d439cb25..10df82ea847 100644
--- a/test/Interop/SwiftToCxxToSwift/hide-swift-module-namespace-in-swift.swift
+++ b/test/Interop/SwiftToCxxToSwift/hide-swift-module-namespace-in-swift.swift
@@ -32,6 +32,6 @@ public func testFunction() -> String {
     return ""
 }
 
-// CHECK: namespace Swift __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Swift") {
-// CHECK: namespace SwiftMod __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("SwiftMod") {
-// CHECK-NOT: namespace Swift {
+// CHECK: namespace swift SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("swift") {
+// CHECK: namespace SwiftMod SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("SwiftMod") {
+// CHECK-NOT: namespace swift {
diff --git a/test/PrintAsCxx/empty.swift b/test/PrintAsCxx/empty.swift
index 2b765bceaac..32281bbf65b 100644
--- a/test/PrintAsCxx/empty.swift
+++ b/test/PrintAsCxx/empty.swift
@@ -103,7 +103,7 @@
 // CHECK:       } // namespace swift
 // CHECK-EMPTY:
 // CHECK-NEXT:  #endif
-// CHECK:       namespace empty __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("empty") {
+// CHECK:       namespace empty SWIFT_PRIVATE_ATTR SWIFT_SYMBOL_MODULE("empty") {
 // CHECK:       } // namespace empty
 // CHECK:       #endif