diff --git a/clang-tools-extra/clang-tidy/ClangTidy.cpp b/clang-tools-extra/clang-tidy/ClangTidy.cpp
--- a/clang-tools-extra/clang-tidy/ClangTidy.cpp
+++ b/clang-tools-extra/clang-tidy/ClangTidy.cpp
@@ -423,7 +423,7 @@
   Preprocessor *PP = &Compiler.getPreprocessor();
   Preprocessor *ModuleExpanderPP = PP;
 
-  if (Context.getLangOpts().Modules && OverlayFS != nullptr) {
+  if (Context.getLangOpts().hasModules() && OverlayFS != nullptr) {
     auto ModuleExpander = std::make_unique<ExpandModularHeadersPPCallbacks>(
         &Compiler, OverlayFS);
     ModuleExpanderPP = ModuleExpander->getPreprocessor();
diff --git a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
--- a/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
+++ b/clang-tools-extra/clang-tidy/ExpandModularHeadersPPCallbacks.cpp
@@ -80,7 +80,7 @@
 
   Diags.setSourceManager(&Sources);
 
-  LangOpts.Modules = false;
+  LangOpts.ClangModules = false;
 
   auto HSO = std::make_shared<HeaderSearchOptions>();
   *HSO = Compiler.getHeaderSearchOpts();
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone-suspicious-include.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone-suspicious-include.cpp
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone-suspicious-include.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone-suspicious-include.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s bugprone-suspicious-include %t -- -- -isystem %S/Inputs/Headers -fmodules
+// RUN: %check_clang_tidy %s bugprone-suspicious-include %t -- -- -isystem %S/Inputs/Headers
 
 // clang-format off
 
diff --git a/clang-tools-extra/test/pp-trace/pp-trace-modules.cpp b/clang-tools-extra/test/pp-trace/pp-trace-modules.cpp
--- a/clang-tools-extra/test/pp-trace/pp-trace-modules.cpp
+++ b/clang-tools-extra/test/pp-trace/pp-trace-modules.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: pp-trace -callbacks '*,-FileChanged,-MacroDefined' %s -- -x objective-c++ -undef -target x86_64 -std=c++11 -fmodules -fcxx-modules -fmodules-cache-path=%t -I%S -I%S/Input | FileCheck --strict-whitespace %s
+// RUN: pp-trace -callbacks '*,-FileChanged,-MacroDefined' %s -- -x objective-c++ -undef -target x86_64 -std=c++11 -fmodules -fmodules-cache-path=%t -I%S -I%S/Input | FileCheck --strict-whitespace %s
 
 // CHECK: ---
 
diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -159,6 +159,8 @@
   "'%0': unable to use AST files with this tool">;
 def err_drv_no_module_support : Error<
   "'%0': unable to use module files with this tool">;
+def err_drv_clang_module_cxx_module_conflicts : Error <
+  "Unable to use clang module and c++20 module at the same time.">;
 def err_drv_clang_unsupported : Error<
   "the clang compiler does not support '%0'">;
 def err_drv_clang_unsupported_opt_cxx_darwin_i386 : Error<
diff --git a/clang/include/clang/Basic/DiagnosticFrontendKinds.td b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
--- a/clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -241,6 +241,8 @@
 def err_modules_embed_file_not_found :
   Error<"file '%0' specified by '-fmodules-embed-file=' not found">,
   DefaultFatal;
+def err_conflicts_clang_module_and_cxx20_module :
+  Error<"Unable to use clang module and c++20 module at the same time.">;
 def err_module_header_file_not_found :
   Error<"module header file '%0' not found">, DefaultFatal;
 
diff --git a/clang/include/clang/Basic/Features.def b/clang/include/clang/Basic/Features.def
--- a/clang/include/clang/Basic/Features.def
+++ b/clang/include/clang/Basic/Features.def
@@ -105,7 +105,7 @@
 FEATURE(objc_fixed_enum, LangOpts.ObjC)
 FEATURE(objc_instancetype, LangOpts.ObjC)
 FEATURE(objc_kindof, LangOpts.ObjC)
-FEATURE(objc_modules, LangOpts.ObjC && LangOpts.Modules)
+FEATURE(objc_modules, LangOpts.ObjC && LangOpts.ClangModules)
 FEATURE(objc_nonfragile_abi, LangOpts.ObjCRuntime.isNonFragile())
 FEATURE(objc_property_explicit_atomic, true)
 FEATURE(objc_protocol_qualifier_mangling, true)
@@ -222,7 +222,7 @@
 FEATURE(is_trivially_constructible, LangOpts.CPlusPlus)
 FEATURE(is_trivially_copyable, LangOpts.CPlusPlus)
 FEATURE(is_union, LangOpts.CPlusPlus)
-FEATURE(modules, LangOpts.Modules)
+FEATURE(modules, LangOpts.hasModules())
 FEATURE(safe_stack, LangOpts.Sanitize.has(SanitizerKind::SafeStack))
 FEATURE(shadow_call_stack,
         LangOpts.Sanitize.has(SanitizerKind::ShadowCallStack))
diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -398,6 +398,11 @@
     return isCompilingModule() || ModulesLocalVisibility;
   }
 
+  /// are clang module or c++20 module (or c++ module ts) enabled?
+  bool hasModules() const {
+    return ClangModules || CPlusPlusModules || ModulesTS;
+  }
+
   bool isSignedOverflowDefined() const {
     return getSignedOverflowBehavior() == SOB_Defined;
   }
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -162,7 +162,7 @@
 BENIGN_LANGOPT(EmitAllDecls      , 1, 0, "emitting all declarations")
 LANGOPT(MathErrno         , 1, 1, "errno in math functions")
 BENIGN_LANGOPT(HeinousExtensions , 1, 0, "extensions that we really don't like and may be ripped out at any time")
-LANGOPT(Modules           , 1, 0, "modules semantics")
+LANGOPT(ClangModules           , 1, 0, "clang modules semantics")
 COMPATIBLE_LANGOPT(ModulesTS  , 1, 0, "C++ Modules TS syntax")
 COMPATIBLE_LANGOPT(CPlusPlusModules, 1, 0, "C++ modules syntax")
 BENIGN_ENUM_LANGOPT(CompilingModule, CompilingModuleKind, 2, CMK_None,
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2189,7 +2189,7 @@
   Flags<[CC1Option]>, HelpText<"Enable support for the C++ Modules TS">,
   MarshallingInfoFlag<LangOpts<"ModulesTS">>;
 defm modules : BoolFOption<"modules",
-  LangOpts<"Modules">, Default<!strconcat(fmodules_ts.KeyPath, "||", fcxx_modules.KeyPath)>,
+  LangOpts<"ClangModules">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "Enable the 'modules' language feature">,
   NegFlag<SetFalse>, BothFlags<[NoXarchOption, CoreOption]>>;
 def fmodule_maps : Flag <["-"], "fmodule-maps">, Flags<[CoreOption]>, Alias<fimplicit_module_maps>;
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -606,7 +606,7 @@
       // FIXME: Find a spare bit on IdentifierInfo and store a
       //        HasModuleMacros flag.
       if (!II->hasMacroDefinition() ||
-          (!PP.getLangOpts().Modules &&
+          (!PP.getLangOpts().hasModules() &&
            !PP.getLangOpts().ModulesLocalVisibility) ||
           !PP.CurSubmoduleState->VisibleModules.getGeneration())
         return nullptr;
@@ -1090,7 +1090,7 @@
   }
   bool isMacroDefined(const IdentifierInfo *II) {
     return II->hasMacroDefinition() &&
-           (!getLangOpts().Modules || (bool)getMacroDefinition(II));
+           (!getLangOpts().hasModules() || (bool)getMacroDefinition(II));
   }
 
   /// Determine whether II is defined as a macro within the module M,
diff --git a/clang/lib/ARCMigrate/ObjCMT.cpp b/clang/lib/ARCMigrate/ObjCMT.cpp
--- a/clang/lib/ARCMigrate/ObjCMT.cpp
+++ b/clang/lib/ARCMigrate/ObjCMT.cpp
@@ -1734,7 +1734,7 @@
     return true;
   }
   edit::Commit commit(*Editor);
-  if (Ctx.getLangOpts().Modules)
+  if (Ctx.getLangOpts().ClangModules)
     commit.insert(Loc, "#ifndef NS_ENUM\n@import Foundation;\n#endif\n");
   else
     commit.insert(Loc, "#ifndef NS_ENUM\n#import <Foundation/Foundation.h>\n#endif\n");
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -4420,7 +4420,7 @@
                            bool IsScopedUsingClassTag, bool IsFixed) {
   auto *Enum = new (C, DC) EnumDecl(C, DC, StartLoc, IdLoc, Id, PrevDecl,
                                     IsScoped, IsScopedUsingClassTag, IsFixed);
-  Enum->setMayHaveOutOfDateDef(C.getLangOpts().Modules);
+  Enum->setMayHaveOutOfDateDef(C.getLangOpts().hasModules());
   C.getTypeDeclType(Enum, PrevDecl);
   return Enum;
 }
@@ -4429,7 +4429,7 @@
   EnumDecl *Enum =
       new (C, ID) EnumDecl(C, nullptr, SourceLocation(), SourceLocation(),
                            nullptr, nullptr, false, false, false);
-  Enum->setMayHaveOutOfDateDef(C.getLangOpts().Modules);
+  Enum->setMayHaveOutOfDateDef(C.getLangOpts().hasModules());
   return Enum;
 }
 
@@ -4564,7 +4564,7 @@
                                IdentifierInfo *Id, RecordDecl* PrevDecl) {
   RecordDecl *R = new (C, DC) RecordDecl(Record, TK, C, DC,
                                          StartLoc, IdLoc, Id, PrevDecl);
-  R->setMayHaveOutOfDateDef(C.getLangOpts().Modules);
+  R->setMayHaveOutOfDateDef(C.getLangOpts().hasModules());
 
   C.getTypeDeclType(R, PrevDecl);
   return R;
@@ -4574,7 +4574,7 @@
   RecordDecl *R =
       new (C, ID) RecordDecl(Record, TTK_Struct, C, nullptr, SourceLocation(),
                              SourceLocation(), nullptr, nullptr);
-  R->setMayHaveOutOfDateDef(C.getLangOpts().Modules);
+  R->setMayHaveOutOfDateDef(C.getLangOpts().hasModules());
   return R;
 }
 
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -136,7 +136,7 @@
                                      bool DelayTypeCreation) {
   auto *R = new (C, DC) CXXRecordDecl(CXXRecord, TK, C, DC, StartLoc, IdLoc, Id,
                                       PrevDecl);
-  R->setMayHaveOutOfDateDef(C.getLangOpts().Modules);
+  R->setMayHaveOutOfDateDef(C.getLangOpts().hasModules());
 
   // FIXME: DelayTypeCreation seems like such a hack
   if (!DelayTypeCreation)
diff --git a/clang/lib/AST/DeclObjC.cpp b/clang/lib/AST/DeclObjC.cpp
--- a/clang/lib/AST/DeclObjC.cpp
+++ b/clang/lib/AST/DeclObjC.cpp
@@ -1503,7 +1503,7 @@
   auto *Result = new (C, DC)
       ObjCInterfaceDecl(C, DC, atLoc, Id, typeParamList, ClassLoc, PrevDecl,
                         isInternal);
-  Result->Data.setInt(!C.getLangOpts().Modules);
+  Result->Data.setInt(!C.getLangOpts().ClangModules);
   C.getObjCInterfaceType(Result, PrevDecl);
   return Result;
 }
@@ -1513,7 +1513,7 @@
   auto *Result = new (C, ID)
       ObjCInterfaceDecl(C, nullptr, SourceLocation(), nullptr, nullptr,
                         SourceLocation(), nullptr, false);
-  Result->Data.setInt(!C.getLangOpts().Modules);
+  Result->Data.setInt(!C.getLangOpts().ClangModules);
   return Result;
 }
 
@@ -1899,7 +1899,7 @@
                                            ObjCProtocolDecl *PrevDecl) {
   auto *Result =
       new (C, DC) ObjCProtocolDecl(C, DC, Id, nameLoc, atStartLoc, PrevDecl);
-  Result->Data.setInt(!C.getLangOpts().Modules);
+  Result->Data.setInt(!C.getLangOpts().ClangModules);
   return Result;
 }
 
@@ -1908,7 +1908,7 @@
   ObjCProtocolDecl *Result =
       new (C, ID) ObjCProtocolDecl(C, nullptr, nullptr, SourceLocation(),
                                    SourceLocation(), nullptr);
-  Result->Data.setInt(!C.getLangOpts().Modules);
+  Result->Data.setInt(!C.getLangOpts().ClangModules);
   return Result;
 }
 
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -551,7 +551,7 @@
     SanStats->finish();
 
   if (CodeGenOpts.Autolink &&
-      (Context.getLangOpts().Modules || !LinkerOptionsMetadata.empty())) {
+      (Context.getLangOpts().hasModules() || !LinkerOptionsMetadata.empty())) {
     EmitModuleLinkOptions();
   }
 
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3438,24 +3438,22 @@
   return false;
 }
 
-static void RenderModulesOptions(Compilation &C, const Driver &D,
+static bool RenderModulesOptions(Compilation &C, const Driver &D,
                                  const ArgList &Args, const InputInfo &Input,
                                  const InputInfo &Output,
-                                 ArgStringList &CmdArgs, bool &HaveModules) {
-  // -fmodules enables the use of precompiled modules (off by default).
-  // Users can pass -fno-cxx-modules to turn off modules support for
-  // C++/Objective-C++ programs.
+                                 ArgStringList &CmdArgs, bool HaveCXXModules) {
+  if (Args.hasFlag(options::OPT_fmodules, options::OPT_fno_modules, false) &&
+      HaveCXXModules)
+    D.Diag(clang::diag::err_drv_clang_module_cxx_module_conflicts);
+
+  // -fmodules enables the use of clang modules (off by default).
   bool HaveClangModules = false;
   if (Args.hasFlag(options::OPT_fmodules, options::OPT_fno_modules, false)) {
-    bool AllowedInCXX = Args.hasFlag(options::OPT_fcxx_modules,
-                                     options::OPT_fno_cxx_modules, true);
-    if (AllowedInCXX || !types::isCXX(Input.getType())) {
-      CmdArgs.push_back("-fmodules");
-      HaveClangModules = true;
-    }
+    CmdArgs.push_back("-fmodules");
+    HaveClangModules = true;
   }
 
-  HaveModules |= HaveClangModules;
+  bool HaveModules = HaveCXXModules || HaveClangModules;
   if (Args.hasArg(options::OPT_fmodules_ts)) {
     CmdArgs.push_back("-fmodules-ts");
     HaveModules = true;
@@ -3610,6 +3608,8 @@
     CmdArgs.push_back("-fmodules-validate-system-headers");
 
   Args.AddLastArg(CmdArgs, options::OPT_fmodules_disable_diagnostic_validation);
+
+  return HaveModules;
 }
 
 static void RenderCharacterOptions(const ArgList &Args, const llvm::Triple &T,
@@ -6315,12 +6315,15 @@
                   options::OPT_finline_hint_functions,
                   options::OPT_fno_inline_functions);
 
+  bool HaveCXXModules = Args.hasFlag(
+      options::OPT_fcxx_modules, options::OPT_fno_cxx_modules,
+      Std && (Std->containsValue("c++2a") || Std->containsValue("c++20") ||
+              Std->containsValue("c++latest")));
+
   // FIXME: Find a better way to determine whether the language has modules
   // support by default, or just assume that all languages do.
   bool HaveModules =
-      Std && (Std->containsValue("c++2a") || Std->containsValue("c++20") ||
-              Std->containsValue("c++latest"));
-  RenderModulesOptions(C, D, Args, Input, Output, CmdArgs, HaveModules);
+      RenderModulesOptions(C, D, Args, Input, Output, CmdArgs, HaveCXXModules);
 
   if (Args.hasFlag(options::OPT_fpch_validate_input_files_content,
                    options::OPT_fno_pch_validate_input_files_content, false))
diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -2257,7 +2257,7 @@
   }
 
   // Disable the preprocessing record if modules are not enabled.
-  if (!Clang->getLangOpts().Modules)
+  if (!Clang->getLangOpts().hasModules())
     PreprocessorOpts.DetailedRecord = false;
 
   std::unique_ptr<SyntaxOnlyAction> Act;
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -485,7 +485,7 @@
 
   PP->setPreprocessedOutput(getPreprocessorOutputOpts().ShowCPP);
 
-  if (PP->getLangOpts().Modules && PP->getLangOpts().ImplicitModules) {
+  if (PP->getLangOpts().hasModules() && PP->getLangOpts().ImplicitModules) {
     std::string ModuleHash = getInvocation().getModuleHash();
     PP->getHeaderSearchInfo().setModuleHash(ModuleHash);
     PP->getHeaderSearchInfo().setModuleCachePath(
diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -584,6 +584,10 @@
   if (!BeginInvocation(CI))
     return false;
 
+  if (CI.getLangOpts().ClangModules && CI.getLangOpts().CPlusPlusModules)
+    CI.getDiagnostics().Report(
+        diag::err_conflicts_clang_module_and_cxx20_module);
+
   // If we're replaying the build of an AST file, import it and set up
   // the initial state from its build.
   if (ReplayASTFile) {
@@ -879,7 +883,7 @@
         return false;
       CI.setASTReader(static_cast<ASTReader *>(FinalReader.get()));
       CI.getASTContext().setExternalSource(source);
-    } else if (CI.getLangOpts().Modules ||
+    } else if (CI.getLangOpts().hasModules() ||
                !CI.getPreprocessorOpts().ImplicitPCHInclude.empty()) {
       // Use PCM or PCH.
       assert(hasPCHSupport() && "This action does not have PCH support!");
@@ -910,7 +914,7 @@
       // If modules are enabled, create the AST reader before creating
       // any builtins, so that all declarations know that they might be
       // extended by an external source.
-      if (CI.getLangOpts().Modules || !CI.hasASTContext() ||
+      if (CI.getLangOpts().hasModules() || !CI.hasASTContext() ||
           !CI.getASTContext().getExternalSource()) {
         CI.createASTReader();
         CI.getASTReader()->setDeserializationListener(DeserialListener,
@@ -925,7 +929,7 @@
 
   // Initialize built-in info as long as we aren't using an external AST
   // source.
-  if (CI.getLangOpts().Modules || !CI.hasASTContext() ||
+  if (CI.getLangOpts().hasModules() || !CI.hasASTContext() ||
       !CI.getASTContext().getExternalSource()) {
     Preprocessor &PP = CI.getPreprocessor();
     PP.getBuiltinInfo().initializeBuiltins(PP.getIdentifierTable(),
@@ -933,7 +937,7 @@
   } else {
     // FIXME: If this is a problem, recover from it by creating a multiplex
     // source.
-    assert((!CI.getLangOpts().Modules || CI.getASTReader()) &&
+    assert((!CI.getLangOpts().hasModules() || CI.getASTReader()) &&
            "modules enabled but created an external source that "
            "doesn't support modules");
   }
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -212,7 +212,7 @@
 
 bool GenerateModuleFromModuleMapAction::BeginSourceFileAction(
     CompilerInstance &CI) {
-  if (!CI.getLangOpts().Modules) {
+  if (!CI.getLangOpts().ClangModules) {
     CI.getDiagnostics().Report(diag::err_module_build_requires_fmodules);
     return false;
   }
@@ -263,7 +263,7 @@
 
 bool GenerateHeaderModuleAction::PrepareToExecuteAction(
     CompilerInstance &CI) {
-  if (!CI.getLangOpts().Modules) {
+  if (!CI.getLangOpts().hasModules()) {
     CI.getDiagnostics().Report(diag::err_header_module_requires_modules);
     return false;
   }
diff --git a/clang/lib/Lex/PPDirectives.cpp b/clang/lib/Lex/PPDirectives.cpp
--- a/clang/lib/Lex/PPDirectives.cpp
+++ b/clang/lib/Lex/PPDirectives.cpp
@@ -1144,12 +1144,12 @@
       break;
 
     case tok::pp___public_macro:
-      if (getLangOpts().Modules || getLangOpts().ModulesLocalVisibility)
+      if (getLangOpts().hasModules() || getLangOpts().ModulesLocalVisibility)
         return HandleMacroPublicDirective(Result);
       break;
 
     case tok::pp___private_macro:
-      if (getLangOpts().Modules || getLangOpts().ModulesLocalVisibility)
+      if (getLangOpts().hasModules() || getLangOpts().ModulesLocalVisibility)
         return HandleMacroPrivateDirective();
       break;
     }
@@ -2057,7 +2057,8 @@
   // Determine whether we should try to import the module for this #include, if
   // there is one. Don't do so if precompiled module support is disabled or we
   // are processing this module textually (because we're building the module).
-  if (Action == Enter && File && SuggestedModule && getLangOpts().Modules &&
+  if (Action == Enter && File && SuggestedModule &&
+      getLangOpts().hasModules() &&
       !isForModuleBuilding(SuggestedModule.getModule(),
                            getLangOpts().CurrentModule,
                            getLangOpts().ModuleName)) {
@@ -2143,7 +2144,7 @@
   // this file will have no effect.
   if (Action == Enter && File &&
       !HeaderInfo.ShouldEnterIncludeFile(*this, &File->getFileEntry(),
-                                         EnterOnce, getLangOpts().Modules,
+                                         EnterOnce, getLangOpts().hasModules(),
                                          SuggestedModule.getModule())) {
     // Even if we've already preprocessed this header once and know that we
     // don't need to see its contents again, we still need to import it if it's
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -875,7 +875,7 @@
   if (((LastTokenWasAt && II.isModulesImport()) ||
        Identifier.is(tok::kw_import)) &&
       !InMacroArgs && !DisableMacroExpansion &&
-      (getLangOpts().Modules || getLangOpts().DebuggerSupport) &&
+      (getLangOpts().hasModules() || getLangOpts().DebuggerSupport) &&
       CurLexerKind != CLK_CachingLexer) {
     ModuleImportLoc = Identifier.getLocation();
     ModuleImportPath.clear();
@@ -1285,7 +1285,7 @@
   }
 
   Module *Imported = nullptr;
-  if (getLangOpts().Modules) {
+  if (getLangOpts().hasModules()) {
     Imported = TheModuleLoader.loadModule(ModuleImportLoc,
                                           ModuleImportPath,
                                           Module::Hidden,
diff --git a/clang/lib/Parse/ParseObjc.cpp b/clang/lib/Parse/ParseObjc.cpp
--- a/clang/lib/Parse/ParseObjc.cpp
+++ b/clang/lib/Parse/ParseObjc.cpp
@@ -78,7 +78,7 @@
     SingleDecl = ParseObjCPropertyDynamic(AtLoc);
     break;
   case tok::objc_import:
-    if (getLangOpts().Modules || getLangOpts().DebuggerSupport) {
+    if (getLangOpts().hasModules() || getLangOpts().DebuggerSupport) {
       SingleDecl = ParseModuleImport(AtLoc);
       break;
     }
diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -4148,7 +4148,7 @@
           Modules[I]->isAvailable() ? CXAvailability_Available
                                     : CXAvailability_NotAvailable));
     }
-  } else if (getLangOpts().Modules) {
+  } else if (getLangOpts().hasModules()) {
     // Load the named module.
     Module *Mod =
         PP.getModuleLoader().loadModule(ImportLoc, Path, Module::AllVisible,
@@ -6741,7 +6741,7 @@
   Builder.AddPlaceholderChunk("class");
   Results.AddResult(Result(Builder.TakeString()));
 
-  if (Results.getSema().getLangOpts().Modules) {
+  if (Results.getSema().getLangOpts().hasModules()) {
     // @import name
     Builder.AddTypedTextChunk(OBJC_AT_KEYWORD_NAME(NeedAt, "import"));
     Builder.AddChunk(CodeCompletionString::CK_HorizontalSpace);
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
@@ -2218,7 +2218,7 @@
                                                      TypedefNameDecl *Decl,
                                                      LookupResult &Previous) {
   // This is only interesting when modules are enabled.
-  if (!S.getLangOpts().Modules && !S.getLangOpts().ModulesLocalVisibility)
+  if (!S.getLangOpts().hasModules() && !S.getLangOpts().ModulesLocalVisibility)
     return;
 
   // Empty sets are uninteresting.
@@ -2444,7 +2444,7 @@
   }
 
   // Modules always permit redefinition of typedefs, as does C11.
-  if (getLangOpts().Modules || getLangOpts().C11)
+  if (getLangOpts().hasModules() || getLangOpts().C11)
     return;
 
   // If we have a redefinition of a typedef in C, emit a warning.  This warning
@@ -17986,7 +17986,7 @@
 
 Sema::SkipBodyInfo Sema::shouldSkipAnonEnumBody(Scope *S, IdentifierInfo *II,
                                                 SourceLocation IILoc) {
-  if (!(getLangOpts().Modules || getLangOpts().ModulesLocalVisibility) ||
+  if (!(getLangOpts().hasModules() || getLangOpts().ModulesLocalVisibility) ||
       !getLangOpts().CPlusPlus)
     return SkipBodyInfo();
 
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -1234,7 +1234,7 @@
 
     // If we are using modules, add the decl to the context in order to
     // serialize something meaningful.
-    if (getLangOpts().Modules)
+    if (getLangOpts().ClangModules)
       PushOnScopeChains(PDecl, TUScope);
     PDecl->startDefinition();
   } else {
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -4892,7 +4892,7 @@
 
   // If we're handling a missing symbol error, using modules, and the
   // special search all modules option is used, look for a missing import.
-  if (ErrorRecovery && getLangOpts().Modules &&
+  if (ErrorRecovery && getLangOpts().hasModules() &&
       getLangOpts().ModulesSearchAll) {
     // The following has the side effect of loading the missing module.
     getModuleLoader().lookupMissingImports(Typo->getName(),
@@ -5463,7 +5463,6 @@
   if (Correction.requiresImport()) {
     NamedDecl *Decl = Correction.getFoundDecl();
     assert(Decl && "import required but no declaration to import");
-
     diagnoseMissingImport(Correction.getCorrectionRange().getBegin(), Decl,
                           MissingImportKind::Declaration, ErrorRecovery);
     return;
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -11095,7 +11095,7 @@
 } // end anonymous namespace
 
 void Sema::checkSpecializationVisibility(SourceLocation Loc, NamedDecl *Spec) {
-  if (!getLangOpts().Modules)
+  if (!getLangOpts().hasModules())
     return;
 
   ExplicitSpecializationVisibilityChecker(*this, Loc).check(Spec);
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
@@ -8492,7 +8492,7 @@
 bool Sema::hasVisibleDefinition(NamedDecl *D, NamedDecl **Suggested,
                                 bool OnlyNeedComplete) {
   // Easy case: if we don't have modules, all declarations are visible.
-  if (!getLangOpts().Modules && !getLangOpts().ModulesLocalVisibility)
+  if (!getLangOpts().hasModules() && !getLangOpts().ModulesLocalVisibility)
     return true;
 
   // If this definition was instantiated from a template, map back to the
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
@@ -703,7 +703,7 @@
   }
 
   // Detailed record is important since it is used for the module cache hash.
-  if (LangOpts.Modules &&
+  if (LangOpts.hasModules() &&
       PPOpts.DetailedRecord != ExistingPPOpts.DetailedRecord && Validate) {
     if (Diags) {
       Diags->Report(diag::err_pch_pp_detailed_record) << PPOpts.DetailedRecord;
@@ -784,7 +784,7 @@
                                      DiagnosticsEngine *Diags,
                                      const LangOptions &LangOpts,
                                      const PreprocessorOptions &PPOpts) {
-  if (LangOpts.Modules) {
+  if (LangOpts.hasModules()) {
     if (SpecificModuleCachePath != ExistingModuleCachePath &&
         !PPOpts.AllowPCHWithDifferentModulesCachePath) {
       if (Diags)
@@ -1246,7 +1246,7 @@
 
 void ASTReader::Error(StringRef Msg) const {
   Error(diag::err_fe_pch_malformed, Msg);
-  if (PP.getLangOpts().Modules && !Diags.isDiagnosticInFlight() &&
+  if (PP.getLangOpts().hasModules() && !Diags.isDiagnosticInFlight() &&
       !PP.getHeaderSearchInfo().getModuleCachePath().empty()) {
     Diag(diag::note_module_cache_path)
       << PP.getHeaderSearchInfo().getModuleCachePath();
@@ -2062,7 +2062,7 @@
   Deserializing AnIdentifier(this);
 
   unsigned PriorGeneration = 0;
-  if (getContext().getLangOpts().Modules)
+  if (getContext().getLangOpts().hasModules())
     PriorGeneration = IdentifierGeneration[&II];
 
   // If there is a global index, look there first to determine which modules
@@ -2089,7 +2089,7 @@
   II->setOutOfDate(false);
 
   // Update the generation for this identifier.
-  if (getContext().getLangOpts().Modules)
+  if (getContext().getLangOpts().hasModules())
     IdentifierGeneration[II] = getGeneration();
 }
 
@@ -4108,7 +4108,7 @@
     return false;
 
   if (TriedLoadingGlobalIndex || !UseGlobalIndex ||
-      !PP.getLangOpts().Modules)
+      !PP.getLangOpts().hasModules())
     return true;
 
   // Try to load the global index.
@@ -4129,8 +4129,8 @@
 }
 
 bool ASTReader::isGlobalIndexUnavailable() const {
-  return PP.getLangOpts().Modules && UseGlobalIndex &&
-         !hasGlobalIndex() && TriedLoadingGlobalIndex;
+  return PP.getLangOpts().hasModules() && UseGlobalIndex && !hasGlobalIndex() &&
+         TriedLoadingGlobalIndex;
 }
 
 static void updateModuleTimestamp(ModuleFile &MF) {
@@ -4219,7 +4219,7 @@
                       /*ImportedBy=*/nullptr, Loaded, 0, 0, ASTFileSignature(),
                       ClientLoadCapabilities)) {
     ModuleMgr.removeModules(ModuleMgr.begin() + NumModules,
-                            PP.getLangOpts().Modules
+                            PP.getLangOpts().hasModules()
                                 ? &PP.getHeaderSearchInfo().getModuleMap()
                                 : nullptr);
 
@@ -9325,7 +9325,7 @@
       // FIXME: Check for =delete/=default?
       // FIXME: Complain about ODR violations here?
       const FunctionDecl *Defn = nullptr;
-      if (!getContext().getLangOpts().Modules || !FD->hasBody(Defn)) {
+      if (!getContext().getLangOpts().hasModules() || !FD->hasBody(Defn)) {
         FD->setLazyBody(PB->second);
       } else {
         auto *NonConstDefn = const_cast<FunctionDecl*>(Defn);
@@ -9349,7 +9349,7 @@
     }
 
     ObjCMethodDecl *MD = cast<ObjCMethodDecl>(PB->first);
-    if (!getContext().getLangOpts().Modules || !MD->hasBody())
+    if (!getContext().getLangOpts().hasModules() || !MD->hasBody())
       MD->setLazyBody(PB->second);
   }
   PendingBodies.clear();
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -758,7 +758,7 @@
   // If this is a definition subject to the ODR, and we already have a
   // definition, merge this one into it.
   if (ED->isCompleteDefinition() &&
-      Reader.getContext().getLangOpts().Modules &&
+      Reader.getContext().getLangOpts().hasModules() &&
       Reader.getContext().getLangOpts().CPlusPlus) {
     EnumDecl *&OldDef = Reader.EnumDefinitions[ED->getCanonicalDecl()];
     if (!OldDef) {
@@ -1018,7 +1018,7 @@
       if (InsertPos)
         CommonPtr->Specializations.InsertNode(FTInfo, InsertPos);
       else {
-        assert(Reader.getContext().getLangOpts().Modules &&
+        assert(Reader.getContext().getLangOpts().hasModules() &&
                "already deserialized this template specialization");
         mergeRedeclarable(FD, ExistingInfo->getFunction(), Redecl);
       }
@@ -2564,7 +2564,7 @@
                                       RedeclarableResult &Redecl,
                                       DeclID TemplatePatternID) {
   // If modules are not available, there is no reason to perform this merge.
-  if (!Reader.getContext().getLangOpts().Modules)
+  if (!Reader.getContext().getLangOpts().hasModules())
     return;
 
   // If we're not the canonical declaration, we don't need to merge.
@@ -2689,7 +2689,7 @@
 /// identical class definitions from two different modules.
 void ASTDeclReader::mergeMergeable(LifetimeExtendedTemporaryDecl *D) {
   // If modules are not available, there is no reason to perform this merge.
-  if (!Reader.getContext().getLangOpts().Modules)
+  if (!Reader.getContext().getLangOpts().hasModules())
     return;
 
   LifetimeExtendedTemporaryDecl *LETDecl = D;
@@ -2711,7 +2711,7 @@
 template<typename T>
 void ASTDeclReader::mergeMergeable(Mergeable<T> *D) {
   // If modules are not available, there is no reason to perform this merge.
-  if (!Reader.getContext().getLangOpts().Modules)
+  if (!Reader.getContext().getLangOpts().hasModules())
     return;
 
   // ODR-based merging is performed in C++ and in some cases (tag types) in C.
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
@@ -1426,7 +1426,7 @@
 
   WriteInputFiles(Context.SourceMgr,
                   PP.getHeaderSearchInfo().getHeaderSearchOpts(),
-                  PP.getLangOpts().Modules);
+                  PP.getLangOpts().hasModules());
   Stream.ExitBlock();
 }
 
@@ -3268,7 +3268,7 @@
 /// recent declaration in any module that imports this one.
 static NamedDecl *getDeclForLocalLookup(const LangOptions &LangOpts,
                                         NamedDecl *D) {
-  if (!LangOpts.Modules || !D->isFromASTFile())
+  if (!LangOpts.hasModules() || !D->isFromASTFile())
     return D;
 
   if (Decl *Redecl = D->getPreviousDecl()) {
diff --git a/clang/test/ClangScanDeps/Inputs/header-search-pruning/cdb.json b/clang/test/ClangScanDeps/Inputs/header-search-pruning/cdb.json
--- a/clang/test/ClangScanDeps/Inputs/header-search-pruning/cdb.json
+++ b/clang/test/ClangScanDeps/Inputs/header-search-pruning/cdb.json
@@ -1,7 +1,7 @@
 [
   {
     "directory": "DIR",
-    "command": "clang -E DIR/header-search-pruning.cpp -Ibegin -I1 -Ia -I3 -I4 -I5 -I6 -Ib -I8 -Iend DEFINES -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fmodule-map-file=DIR/module.modulemap",
+    "command": "clang -E DIR/header-search-pruning.cpp -Ibegin -I1 -Ia -I3 -I4 -I5 -I6 -Ib -I8 -Iend DEFINES -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fmodule-map-file=DIR/module.modulemap",
     "file": "DIR/header-search-pruning.cpp"
   }
 ]
diff --git a/clang/test/ClangScanDeps/Inputs/module_fmodule_name_cdb.json b/clang/test/ClangScanDeps/Inputs/module_fmodule_name_cdb.json
--- a/clang/test/ClangScanDeps/Inputs/module_fmodule_name_cdb.json
+++ b/clang/test/ClangScanDeps/Inputs/module_fmodule_name_cdb.json
@@ -1,7 +1,7 @@
 [
 {
   "directory": "DIR",
-  "command": "clang -E DIR/modules-fmodule-name-no-module-built.m -IInputs -D INCLUDE_HEADER2 -MD -MF DIR/modules_cdb.d -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fmodule-name=header3 -fimplicit-module-maps",
+  "command": "clang -E DIR/modules-fmodule-name-no-module-built.m -IInputs -D INCLUDE_HEADER2 -MD -MF DIR/modules_cdb.d -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fmodule-name=header3 -fimplicit-module-maps",
   "file": "DIR/modules-fmodule-name-no-module-built.m"
 }
 ]
diff --git a/clang/test/ClangScanDeps/Inputs/modules_cdb.json b/clang/test/ClangScanDeps/Inputs/modules_cdb.json
--- a/clang/test/ClangScanDeps/Inputs/modules_cdb.json
+++ b/clang/test/ClangScanDeps/Inputs/modules_cdb.json
@@ -1,22 +1,22 @@
 [
 {
   "directory": "DIR",
-  "command": "clang -E DIR/modules_cdb_input2.cpp -IInputs -D INCLUDE_HEADER2 -MD -MF DIR/modules_cdb2.d -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps",
+  "command": "clang -E DIR/modules_cdb_input2.cpp -IInputs -D INCLUDE_HEADER2 -MD -MF DIR/modules_cdb2.d -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps",
   "file": "DIR/modules_cdb_input2.cpp"
 },
 {
   "directory": "DIR",
-  "command": "clang -E DIR/modules_cdb_input.cpp -IInputs -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps",
+  "command": "clang -E DIR/modules_cdb_input.cpp -IInputs -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps",
   "file": "DIR/modules_cdb_input.cpp"
 },
 {
   "directory": "DIR",
-  "command": "clang -E DIR/modules_cdb_input.cpp -IInputs -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -o a.o",
+  "command": "clang -E DIR/modules_cdb_input.cpp -IInputs -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -o a.o",
   "file": "DIR/modules_cdb_input.cpp"
 },
 {
   "directory": "DIR",
-  "command": "clang -E DIR/modules_cdb_input.cpp -IInputs -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -o b.o",
+  "command": "clang -E DIR/modules_cdb_input.cpp -IInputs -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -o b.o",
   "file": "DIR/modules_cdb_input.cpp"
 }
 ]
diff --git a/clang/test/ClangScanDeps/Inputs/modules_cdb_by_mod_name.json b/clang/test/ClangScanDeps/Inputs/modules_cdb_by_mod_name.json
--- a/clang/test/ClangScanDeps/Inputs/modules_cdb_by_mod_name.json
+++ b/clang/test/ClangScanDeps/Inputs/modules_cdb_by_mod_name.json
@@ -1,12 +1,12 @@
 [
 {
   "directory": "DIR",
-  "command": "clang -E -IInputs -D INCLUDE_HEADER2 -MD -MF DIR/modules_cdb2.d -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -gmodules -x c++",
+  "command": "clang -E -IInputs -D INCLUDE_HEADER2 -MD -MF DIR/modules_cdb2.d -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -gmodules -x c++",
   "file": ""
 },
 {
   "directory": "DIR",
-  "command": "clang -E -IInputs -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -x c++",
+  "command": "clang -E -IInputs -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -x c++",
   "file": ""
 },
 ]
diff --git a/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl.json b/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl.json
--- a/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl.json
+++ b/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl.json
@@ -1,22 +1,22 @@
 [
 {
   "directory": "DIR",
-  "command": "clang-cl /E /IInputs /D INCLUDE_HEADER2 /clang:-MD /clang:-MF /clang:DIR/modules_cdb2_clangcl.d /clang:-fmodules /clang:-fcxx-modules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -- DIR/modules_cdb_input2.cpp",
+  "command": "clang-cl /E /IInputs /D INCLUDE_HEADER2 /clang:-MD /clang:-MF /clang:DIR/modules_cdb2_clangcl.d /clang:-fmodules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -- DIR/modules_cdb_input2.cpp",
   "file": "DIR/modules_cdb_input2.cpp"
 },
 {
   "directory": "DIR",
-  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fcxx-modules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -- DIR/modules_cdb_input.cpp",
+  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -- DIR/modules_cdb_input.cpp",
   "file": "DIR/modules_cdb_input.cpp"
 },
 {
   "directory": "DIR",
-  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fcxx-modules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -o a.o -- DIR/modules_cdb_input.cpp",
+  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -o a.o -- DIR/modules_cdb_input.cpp",
   "file": "DIR/modules_cdb_input.cpp"
 },
 {
   "directory": "DIR",
-  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fcxx-modules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -o b.o -- DIR/modules_cdb_input.cpp",
+  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps -o b.o -- DIR/modules_cdb_input.cpp",
   "file": "DIR/modules_cdb_input.cpp"
 }
 ]
diff --git a/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl_by_mod_name.json b/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl_by_mod_name.json
--- a/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl_by_mod_name.json
+++ b/clang/test/ClangScanDeps/Inputs/modules_cdb_clangcl_by_mod_name.json
@@ -1,12 +1,12 @@
 [
 {
   "directory": "DIR",
-  "command": "clang-cl /E /IInputs /D INCLUDE_HEADER2 /clang:-MD /clang:-MF /clang:DIR/modules_cdb2_clangcl.d /clang:-fmodules /clang:-fcxx-modules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps /clang:-x /clang:c++ --",
+  "command": "clang-cl /E /IInputs /D INCLUDE_HEADER2 /clang:-MD /clang:-MF /clang:DIR/modules_cdb2_clangcl.d /clang:-fmodules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps /clang:-x /clang:c++ --",
   "file": ""
 },
 {
   "directory": "DIR",
-  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fcxx-modules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps /clang:-x /clang:c++ --",
+  "command": "clang-cl /E /IInputs /clang:-fmodules /clang:-fmodules-cache-path=DIR/module-cache_clangcl /clang:-fimplicit-modules /clang:-fimplicit-module-maps /clang:-x /clang:c++ --",
   "file": ""
 },
 ]
diff --git a/clang/test/ClangScanDeps/Inputs/modules_inferred_cdb.json b/clang/test/ClangScanDeps/Inputs/modules_inferred_cdb.json
--- a/clang/test/ClangScanDeps/Inputs/modules_inferred_cdb.json
+++ b/clang/test/ClangScanDeps/Inputs/modules_inferred_cdb.json
@@ -1,7 +1,7 @@
 [
 {
   "directory": "DIR",
-  "command": "clang -E DIR/modules_cdb_input.cpp -FFRAMEWORKS -fmodules -fcxx-modules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -pedantic -Werror",
+  "command": "clang -E DIR/modules_cdb_input.cpp -FFRAMEWORKS -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -pedantic -Werror",
   "file": "DIR/modules_cdb_input.cpp"
 }
 ]
diff --git a/clang/test/Driver/conflict-clang-module-and-cxx20-module.cpp b/clang/test/Driver/conflict-clang-module-and-cxx20-module.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/conflict-clang-module-and-cxx20-module.cpp
@@ -0,0 +1,7 @@
+// RUN: %clangxx -### -c %s -std=c++20 -fmodules 2>&1 | FileCheck %s
+// RUN: %clangxx -### -c %s -std=c++2a -fmodules 2>&1 | FileCheck %s
+// RUN: %clangxx -### -c %s -std=c++20 -fmodules -fno-cxx-modules 2>&1 | FileCheck %s --check-prefix=FINE
+// RUN: %clangxx -### -c %s -fcxx-modules -fmodules -fcxx-modules 2>&1 | FileCheck %s
+
+// CHECK: error: Unable to use clang module and c++20 module at the same time.
+// FINE-NOT: error: Unable to use clang module and c++20 module at the same time.
diff --git a/clang/test/Driver/modules.mm b/clang/test/Driver/modules.mm
--- a/clang/test/Driver/modules.mm
+++ b/clang/test/Driver/modules.mm
@@ -1,11 +1,11 @@
 // RUN: %clang -### %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MODULES %s
-// RUN: %clang -fcxx-modules -### %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MODULES %s
-// RUN: %clang -fmodules -fno-cxx-modules -### %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MODULES %s
+// RUN: %clang -fmodules -### %s 2>&1 | FileCheck -check-prefix=CHECK-HAS-CLANG-MODULES %s
+// RUN: %clang -fmodules -fno-cxx-modules -### %s 2>&1 | FileCheck -check-prefix=CHECK-HAS-CLANG-MODULES %s
 // CHECK-NO-MODULES-NOT: -fmodules
+// CHECK-HAS-CLANG-MODULES: -fmodules
 
-// RUN: %clang -fmodules -### %s 2>&1 | FileCheck -check-prefix=CHECK-HAS-MODULES %s
-// RUN: %clang -fmodules -fno-cxx-modules -fcxx-modules -### %s 2>&1 | FileCheck -check-prefix=CHECK-HAS-MODULES %s
-// CHECK-HAS-MODULES: -fmodules
+// RUN: %clang -fmodules -fcxx-modules -fcxx-modules -### %s 2>&1 | FileCheck -check-prefix=CHECK-CONFLICT %s
+// CHECK-CONFLICT: error
 
 // RUN: %clang -### %s 2>&1 | FileCheck -check-prefix=CHECK-NO-MAPS %s
 // RUN: %clang -fimplicit-module-maps -### %s 2>&1 | FileCheck -check-prefix=CHECK-HAS-MAPS %s
diff --git a/clang/test/Modules/cxx20.cpp b/clang/test/Modules/cxx20.cpp
--- a/clang/test/Modules/cxx20.cpp
+++ b/clang/test/Modules/cxx20.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -x c++ -std=c++20 -fmodules-cache-path=%t -fmodules -fimplicit-module-maps -I %S/Inputs/cxx20 %s -verify -fno-modules-error-recovery
+// RUN: %clang_cc1 -x c++ -std=c++20 -fmodules-cache-path=%t -fmodules -fno-cxx-modules -fimplicit-module-maps -I %S/Inputs/cxx20 %s -verify -fno-modules-error-recovery
 
 // expected-no-diagnostics
 
diff --git a/clang/test/Modules/ms-enums.cpp b/clang/test/Modules/ms-enums.cpp
--- a/clang/test/Modules/ms-enums.cpp
+++ b/clang/test/Modules/ms-enums.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -triple x86_64-windows-msvc -fms-extensions -fms-compatibility -x c++ -std=c++20 -fmodules-cache-path=%t -fmodules -fimplicit-module-maps -I %S/Inputs/ms-enums %s -verify -fno-modules-error-recovery
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -fms-extensions -fms-compatibility -x c++ -fmodules-cache-path=%t -fmodules -fimplicit-module-maps -I %S/Inputs/ms-enums %s -verify -fno-modules-error-recovery
 
 #include "B.h"
 // expected-note@A.h:1 {{declaration here is not visible}}
diff --git a/clang/test/SemaCXX/compare-modules-cxx2a.cpp b/clang/test/SemaCXX/compare-modules-cxx2a.cpp
--- a/clang/test/SemaCXX/compare-modules-cxx2a.cpp
+++ b/clang/test/SemaCXX/compare-modules-cxx2a.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin -fcxx-exceptions -verify -std=c++2a -fmodules -I%S/Inputs %s -fno-modules-error-recovery
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -fcxx-exceptions -verify -std=c++2a -fmodules -fno-cxx-modules -I%S/Inputs %s -fno-modules-error-recovery
 
 #pragma clang module build compare
 module compare {
diff --git a/clang/tools/libclang/Indexing.cpp b/clang/tools/libclang/Indexing.cpp
--- a/clang/tools/libclang/Indexing.cpp
+++ b/clang/tools/libclang/Indexing.cpp
@@ -604,7 +604,7 @@
     PPOpts.DetailedRecord = true;
   }
 
-  if (!requestedToGetTU && !CInvok->getLangOpts()->Modules)
+  if (!requestedToGetTU && !CInvok->getLangOpts()->hasModules())
     PPOpts.DetailedRecord = false;
 
   // Unless the user specified that they want the preamble on the first parse