diff --git a/clang/include/clang/AST/ASTNodeTraverser.h b/clang/include/clang/AST/ASTNodeTraverser.h
--- a/clang/include/clang/AST/ASTNodeTraverser.h
+++ b/clang/include/clang/AST/ASTNodeTraverser.h
@@ -476,6 +476,8 @@
     Visit(D->getAsmString());
   }
 
+  void VisitTopLevelStmtDecl(const TopLevelStmtDecl *D) { Visit(D->getStmt()); }
+
   void VisitCapturedDecl(const CapturedDecl *D) { Visit(D->getBody()); }
 
   void VisitOMPThreadPrivateDecl(const OMPThreadPrivateDecl *D) {
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -4277,6 +4277,34 @@
   static bool classofKind(Kind K) { return K == FileScopeAsm; }
 };
 
+/// A declaration that models statements at global scope. This declaration
+/// supports incremental and interactive C/C++.
+///
+/// \note This is used in libInterpreter, clang -cc1 -fincremental-extensions
+/// and in tools such as clang-repl.
+class TopLevelStmtDecl : public Decl {
+  friend class ASTDeclReader;
+  friend class ASTDeclWriter;
+
+  Stmt *Statement = nullptr;
+
+  TopLevelStmtDecl(DeclContext *DC, SourceLocation L, Stmt *S)
+      : Decl(TopLevelStmt, DC, L), Statement(S) {}
+
+  virtual void anchor();
+
+public:
+  static TopLevelStmtDecl *Create(ASTContext &C, Stmt *Statement);
+  static TopLevelStmtDecl *CreateDeserialized(ASTContext &C, unsigned ID);
+
+  SourceRange getSourceRange() const override LLVM_READONLY;
+  Stmt *getStmt() { return Statement; }
+  const Stmt *getStmt() const { return Statement; }
+
+  static bool classof(const Decl *D) { return classofKind(D->getKind()); }
+  static bool classofKind(Kind K) { return K == TopLevelStmt; }
+};
+
 /// Represents a block literal declaration, which is like an
 /// unnamed FunctionDecl.  For example:
 /// ^{ statement-body }   or   ^(int arg1, float arg2){ statement-body }
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -1543,6 +1543,8 @@
 DEF_TRAVERSE_DECL(FileScopeAsmDecl,
                   { TRY_TO(TraverseStmt(D->getAsmString())); })
 
+DEF_TRAVERSE_DECL(TopLevelStmtDecl, { TRY_TO(TraverseStmt(D->getStmt())); })
+
 DEF_TRAVERSE_DECL(ImportDecl, {})
 
 DEF_TRAVERSE_DECL(FriendDecl, {
diff --git a/clang/include/clang/Basic/DeclNodes.td b/clang/include/clang/Basic/DeclNodes.td
--- a/clang/include/clang/Basic/DeclNodes.td
+++ b/clang/include/clang/Basic/DeclNodes.td
@@ -95,6 +95,7 @@
 def Export : DeclNode<Decl>, DeclContext;
 def ObjCPropertyImpl : DeclNode<Decl>;
 def FileScopeAsm : DeclNode<Decl>;
+def TopLevelStmt : DeclNode<Decl>;
 def AccessSpec : DeclNode<Decl>;
 def Friend : DeclNode<Decl>;
 def FriendTemplate : DeclNode<Decl>;
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
@@ -459,6 +459,11 @@
 // on large _BitInts.
 BENIGN_VALUE_LANGOPT(MaxBitIntWidth, 32, 128, "Maximum width of a _BitInt")
 
+LANGOPT(IncrementalExtensions, 1, 0, " True if we want to process statements"
+        "on the global scope, ignore EOF token and continue later on (thus "
+        "avoid tearing the Lexer and etc. down). Controlled by "
+        "-fincremental-extensions.")
+
 #undef LANGOPT
 #undef COMPATIBLE_LANGOPT
 #undef BENIGN_LANGOPT
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
@@ -2320,6 +2320,13 @@
   HelpText<"Do not enforce -fmodules-decluse and private header restrictions for textual headers. "
            "This flag will be removed in a future Clang release.">;
 
+def fincremental_extensions :
+  Flag<["-"], "fincremental-extensions">,
+  Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Enable incremental processing extensions such as processing"
+           "statements on the global scope.">,
+  MarshallingInfoFlag<LangOpts<"IncrementalExtensions">>;
+
 def fvalidate_ast_input_files_content:
   Flag <["-"], "fvalidate-ast-input-files-content">,
   Group<f_Group>, Flags<[CC1Option]>,
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
@@ -283,10 +283,6 @@
   /// Empty line handler.
   EmptylineHandler *Emptyline = nullptr;
 
-  /// True if we want to ignore EOF token and continue later on (thus
-  /// avoid tearing the Lexer and etc. down).
-  bool IncrementalProcessing = false;
-
 public:
   /// The kind of translation unit we are processing.
   const TranslationUnitKind TUKind;
@@ -1778,11 +1774,14 @@
   void recomputeCurLexerKind();
 
   /// Returns true if incremental processing is enabled
-  bool isIncrementalProcessingEnabled() const { return IncrementalProcessing; }
+  bool isIncrementalProcessingEnabled() const {
+    return getLangOpts().IncrementalExtensions;
+  }
 
   /// Enables the incremental processing
   void enableIncrementalProcessing(bool value = true) {
-    IncrementalProcessing = value;
+    // FIXME: Drop this interface.
+    const_cast<LangOptions &>(getLangOpts()).IncrementalExtensions = value;
   }
 
   /// Specify the point at which code-completion will be performed.
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -464,6 +464,9 @@
 
   typedef Sema::FullExprArg FullExprArg;
 
+  /// A SmallVector of statements.
+  typedef SmallVector<Stmt *, 32> StmtVector;
+
   // Parsing methods.
 
   /// Initialize - Warm up the parser.
@@ -2071,10 +2074,7 @@
   //===--------------------------------------------------------------------===//
   // C99 6.8: Statements and Blocks.
 
-  /// A SmallVector of statements, with stack size 32 (as that is the only one
-  /// used.)
-  typedef SmallVector<Stmt*, 32> StmtVector;
-  /// A SmallVector of expressions, with stack size 12 (the maximum used.)
+  /// A SmallVector of expressions.
   typedef SmallVector<Expr*, 12> ExprVector;
 
   StmtResult
@@ -2451,6 +2451,8 @@
       ParsingDeclSpec &DS,
       llvm::function_ref<void(ParsingFieldDeclarator &)> FieldsCallback);
 
+  DeclGroupPtrTy ParseTopLevelStmtDecl();
+
   bool isDeclarationSpecifier(ImplicitTypenameContext AllowImplicitTypename,
                               bool DisambiguatingWithExpression = false);
   bool isTypeSpecifierQualifier();
@@ -2472,10 +2474,13 @@
 
   /// isDeclarationStatement - Disambiguates between a declaration or an
   /// expression statement, when parsing function bodies.
+  ///
+  /// \param DisambiguatingWithExpression - True to indicate that the purpose of
+  /// this check is to disambiguate between an expression and a declaration.
   /// Returns true for declaration, false for expression.
-  bool isDeclarationStatement() {
+  bool isDeclarationStatement(bool DisambiguatingWithExpression = false) {
     if (getLangOpts().CPlusPlus)
-      return isCXXDeclarationStatement();
+      return isCXXDeclarationStatement(DisambiguatingWithExpression);
     return isDeclarationSpecifier(ImplicitTypenameContext::No, true);
   }
 
@@ -2542,7 +2547,7 @@
   /// isCXXDeclarationStatement - C++-specialized function that disambiguates
   /// between a declaration or an expression statement, when parsing function
   /// bodies. Returns true for declaration, false for expression.
-  bool isCXXDeclarationStatement();
+  bool isCXXDeclarationStatement(bool DisambiguatingWithExpression = false);
 
   /// isCXXSimpleDeclaration - C++-specialized function that disambiguates
   /// between a simple-declaration or an expression-statement.
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -3106,6 +3106,8 @@
                               SourceLocation AsmLoc,
                               SourceLocation RParenLoc);
 
+  Decl *ActOnTopLevelStmtDecl(Stmt *Statement);
+
   /// Handle a C++11 empty-declaration and attribute-declaration.
   Decl *ActOnEmptyDeclaration(Scope *S, const ParsedAttributesView &AttrList,
                               SourceLocation SemiLoc);
diff --git a/clang/include/clang/Sema/Template.h b/clang/include/clang/Sema/Template.h
--- a/clang/include/clang/Sema/Template.h
+++ b/clang/include/clang/Sema/Template.h
@@ -571,6 +571,7 @@
 // Decls which never appear inside a class or function.
 #define OBJCCONTAINER(DERIVED, BASE)
 #define FILESCOPEASM(DERIVED, BASE)
+#define TOPLEVELSTMT(DERIVED, BASE)
 #define IMPORT(DERIVED, BASE)
 #define EXPORT(DERIVED, BASE)
 #define LINKAGESPEC(DERIVED, BASE)
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -1318,6 +1318,9 @@
   /// A FileScopeAsmDecl record.
   DECL_FILE_SCOPE_ASM,
 
+  /// A TopLevelStmtDecl record.
+  DECL_TOP_LEVEL_STMT_DECL,
+
   /// A BlockDecl record.
   DECL_BLOCK,
 
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
@@ -5236,6 +5236,29 @@
                                       SourceLocation());
 }
 
+void TopLevelStmtDecl::anchor() {}
+
+TopLevelStmtDecl *TopLevelStmtDecl::Create(ASTContext &C, Stmt *Statement) {
+  assert(Statement);
+  assert(C.getLangOpts().IncrementalExtensions &&
+         "Must be used only in incremental mode");
+
+  SourceLocation BeginLoc = Statement->getBeginLoc();
+  DeclContext *DC = C.getTranslationUnitDecl();
+
+  return new (C, DC) TopLevelStmtDecl(DC, BeginLoc, Statement);
+}
+
+TopLevelStmtDecl *TopLevelStmtDecl::CreateDeserialized(ASTContext &C,
+                                                       unsigned ID) {
+  return new (C, ID)
+      TopLevelStmtDecl(/*DC=*/nullptr, SourceLocation(), /*S=*/nullptr);
+}
+
+SourceRange TopLevelStmtDecl::getSourceRange() const {
+  return SourceRange(getLocation(), Statement->getEndLoc());
+}
+
 void EmptyDecl::anchor() {}
 
 EmptyDecl *EmptyDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L) {
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -843,6 +843,7 @@
     case LinkageSpec:
     case Export:
     case FileScopeAsm:
+    case TopLevelStmt:
     case StaticAssert:
     case ObjCPropertyImpl:
     case PragmaComment:
diff --git a/clang/lib/AST/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
--- a/clang/lib/AST/DeclPrinter.cpp
+++ b/clang/lib/AST/DeclPrinter.cpp
@@ -72,6 +72,7 @@
     void VisitLabelDecl(LabelDecl *D);
     void VisitParmVarDecl(ParmVarDecl *D);
     void VisitFileScopeAsmDecl(FileScopeAsmDecl *D);
+    void VisitTopLevelStmtDecl(TopLevelStmtDecl *D);
     void VisitImportDecl(ImportDecl *D);
     void VisitStaticAssertDecl(StaticAssertDecl *D);
     void VisitNamespaceDecl(NamespaceDecl *D);
@@ -932,6 +933,11 @@
   Out << ")";
 }
 
+void DeclPrinter::VisitTopLevelStmtDecl(TopLevelStmtDecl *D) {
+  assert(D->getStmt());
+  D->getStmt()->printPretty(Out, nullptr, Policy, Indentation, "\n", &Context);
+}
+
 void DeclPrinter::VisitImportDecl(ImportDecl *D) {
   Out << "@import " << D->getImportedModule()->getFullModuleName()
       << ";\n";
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -90,6 +90,7 @@
   case Decl::Export:
   case Decl::ObjCPropertyImpl:
   case Decl::FileScopeAsm:
+  case Decl::TopLevelStmt:
   case Decl::Friend:
   case Decl::FriendTemplate:
   case Decl::Block:
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -591,6 +591,11 @@
 
   llvm::DenseMap<const llvm::Constant *, llvm::GlobalVariable *> RTTIProxyMap;
 
+  // Helps squashing blocks of TopLevelStmtDecl into a single llvm::Function
+  // when used with -fincremental-extensions.
+  std::pair<std::unique_ptr<CodeGenFunction>, const TopLevelStmtDecl *>
+      GlobalTopLevelStmtBlockInFlight;
+
 public:
   CodeGenModule(ASTContext &C, IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
                 const HeaderSearchOptions &headersearchopts,
@@ -1590,6 +1595,7 @@
 
   void EmitDeclContext(const DeclContext *DC);
   void EmitLinkageSpec(const LinkageSpecDecl *D);
+  void EmitTopLevelStmt(const TopLevelStmtDecl *D);
 
   /// Emit the function that initializes C++ thread_local variables.
   void EmitCXXThreadLocalInitFunc();
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
@@ -516,6 +516,14 @@
   applyGlobalValReplacements();
   applyReplacements();
   emitMultiVersionFunctions();
+
+  if (Context.getLangOpts().IncrementalExtensions &&
+      GlobalTopLevelStmtBlockInFlight.first) {
+    const TopLevelStmtDecl *TLSD = GlobalTopLevelStmtBlockInFlight.second;
+    GlobalTopLevelStmtBlockInFlight.first->FinishFunction(TLSD->getEndLoc());
+    GlobalTopLevelStmtBlockInFlight = {};
+  }
+
   if (CXX20ModuleInits && Primary && Primary->isInterfaceOrPartition())
     EmitCXXModuleInitFunc(Primary);
   else
@@ -6150,6 +6158,39 @@
   EmitDeclContext(LSD);
 }
 
+void CodeGenModule::EmitTopLevelStmt(const TopLevelStmtDecl *D) {
+  std::unique_ptr<CodeGenFunction> &CurCGF =
+      GlobalTopLevelStmtBlockInFlight.first;
+
+  // We emitted a top-level stmt but after it there is initialization.
+  // Stop squashing the top-level stmts into a single function.
+  if (CurCGF && CXXGlobalInits.back() != CurCGF->CurFn) {
+    CurCGF->FinishFunction(D->getEndLoc());
+    CurCGF = nullptr;
+  }
+
+  if (!CurCGF) {
+    // void __stmts__N(void)
+    // FIXME: Ask the ABI name mangler to pick a name.
+    std::string Name = "__stmts__" + llvm::utostr(CXXGlobalInits.size());
+    FunctionArgList Args;
+    QualType RetTy = getContext().VoidTy;
+    const CGFunctionInfo &FnInfo =
+        getTypes().arrangeBuiltinFunctionDeclaration(RetTy, Args);
+    llvm::FunctionType *FnTy = getTypes().GetFunctionType(FnInfo);
+    llvm::Function *Fn = llvm::Function::Create(
+        FnTy, llvm::GlobalValue::InternalLinkage, Name, &getModule());
+
+    CurCGF.reset(new CodeGenFunction(*this));
+    GlobalTopLevelStmtBlockInFlight.second = D;
+    CurCGF->StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
+                          D->getBeginLoc(), D->getBeginLoc());
+    CXXGlobalInits.push_back(Fn);
+  }
+
+  CurCGF->EmitStmt(D->getStmt());
+}
+
 void CodeGenModule::EmitDeclContext(const DeclContext *DC) {
   for (auto *I : DC->decls()) {
     // Unlike other DeclContexts, the contents of an ObjCImplDecl at TU scope
@@ -6359,6 +6400,10 @@
     break;
   }
 
+  case Decl::TopLevelStmt:
+    EmitTopLevelStmt(cast<TopLevelStmtDecl>(D));
+    break;
+
   case Decl::Import: {
     auto *Import = cast<ImportDecl>(D);
 
diff --git a/clang/lib/CodeGen/ModuleBuilder.cpp b/clang/lib/CodeGen/ModuleBuilder.cpp
--- a/clang/lib/CodeGen/ModuleBuilder.cpp
+++ b/clang/lib/CodeGen/ModuleBuilder.cpp
@@ -179,6 +179,7 @@
     }
 
     bool HandleTopLevelDecl(DeclGroupRef DG) override {
+      // FIXME: Why not return false and abort parsing?
       if (Diags.hasErrorOccurred())
         return true;
 
diff --git a/clang/lib/Interpreter/IncrementalParser.cpp b/clang/lib/Interpreter/IncrementalParser.cpp
--- a/clang/lib/Interpreter/IncrementalParser.cpp
+++ b/clang/lib/Interpreter/IncrementalParser.cpp
@@ -101,7 +101,6 @@
       CompletionConsumer = &CI.getCodeCompletionConsumer();
 
     Preprocessor &PP = CI.getPreprocessor();
-    PP.enableIncrementalProcessing();
     PP.EnterMainSourceFile();
 
     if (!CI.hasSema())
@@ -174,9 +173,6 @@
   Sema::ModuleImportState ImportState;
   for (bool AtEOF = P->ParseFirstTopLevelDecl(ADecl, ImportState); !AtEOF;
        AtEOF = P->ParseTopLevelDecl(ADecl, ImportState)) {
-    // If we got a null return and something *was* parsed, ignore it.  This
-    // is due to a top-level semicolon, an action override, or a parse error
-    // skipping something.
     if (ADecl && !Consumer->HandleTopLevelDecl(ADecl.get()))
       return llvm::make_error<llvm::StringError>("Parsing failed. "
                                                  "The consumer rejected a decl",
diff --git a/clang/lib/Interpreter/Interpreter.cpp b/clang/lib/Interpreter/Interpreter.cpp
--- a/clang/lib/Interpreter/Interpreter.cpp
+++ b/clang/lib/Interpreter/Interpreter.cpp
@@ -138,13 +138,11 @@
   // specified. By prepending we allow users to override the default
   // action and use other actions in incremental mode.
   // FIXME: Print proper driver diagnostics if the driver flags are wrong.
-  ClangArgv.insert(ClangArgv.begin() + 1, "-c");
-
-  if (!llvm::is_contained(ClangArgv, " -x")) {
-    // We do C++ by default; append right after argv[0] if no "-x" given
-    ClangArgv.push_back("-x");
-    ClangArgv.push_back("c++");
-  }
+  // We do C++ by default; append right after argv[0] if no "-x" given
+  ClangArgv.insert(ClangArgv.end(), "-xc++");
+  ClangArgv.insert(ClangArgv.end(), "-Xclang");
+  ClangArgv.insert(ClangArgv.end(), "-fincremental-extensions");
+  ClangArgv.insert(ClangArgv.end(), "-c");
 
   // Put a dummy C++ file on to ensure there's at least one compile job for the
   // driver to construct.
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -5381,6 +5381,25 @@
   }
 }
 
+Parser::DeclGroupPtrTy Parser::ParseTopLevelStmtDecl() {
+  assert(PP.isIncrementalProcessingEnabled() && "Not in incremental mode");
+
+  // Parse a top-level-stmt.
+  Parser::StmtVector Stmts;
+  ParsedStmtContext SubStmtCtx = ParsedStmtContext();
+  StmtResult R = ParseStatementOrDeclaration(Stmts, SubStmtCtx);
+  if (!R.isUsable())
+    return nullptr;
+
+  SmallVector<Decl *, 2> DeclsInGroup;
+  DeclsInGroup.push_back(Actions.ActOnTopLevelStmtDecl(R.get()));
+  // Currently happens for things like  -fms-extensions and use `__if_exists`.
+  for (Stmt *S : Stmts)
+    DeclsInGroup.push_back(Actions.ActOnTopLevelStmtDecl(S));
+
+  return Actions.BuildDeclaratorGroup(DeclsInGroup);
+}
+
 /// isDeclarationSpecifier() - Return true if the current token is part of a
 /// declaration specifier.
 ///
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -46,7 +46,10 @@
 ///           'using' 'namespace' '::'[opt] nested-name-specifier[opt]
 ///                 namespace-name ';'
 ///
-bool Parser::isCXXDeclarationStatement() {
+bool Parser::isCXXDeclarationStatement(
+    bool DisambiguatingWithExpression /*=false*/) {
+  assert(getLangOpts().CPlusPlus && "Must be called for C++ only.");
+
   switch (Tok.getKind()) {
     // asm-definition
   case tok::kw_asm:
@@ -59,6 +62,42 @@
   case tok::kw_static_assert:
   case tok::kw__Static_assert:
     return true;
+  case tok::identifier: {
+    if (DisambiguatingWithExpression) {
+      RevertingTentativeParsingAction TPA(*this);
+      // Parse the C++ scope specifier.
+      CXXScopeSpec SS;
+      ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
+                                     /*ObjectHasErrors=*/false,
+                                     /*EnteringContext=*/true);
+
+      switch (Tok.getKind()) {
+      case tok::identifier: {
+        IdentifierInfo *II = Tok.getIdentifierInfo();
+        bool isDeductionGuide =
+            Actions.isDeductionGuideName(getCurScope(), *II, Tok.getLocation(),
+                                         /*Template=*/nullptr);
+        if (Actions.isCurrentClassName(*II, getCurScope(), &SS) ||
+            isDeductionGuide) {
+          if (isConstructorDeclarator(/*Unqualified=*/SS.isEmpty(),
+                                      isDeductionGuide,
+                                      DeclSpec::FriendSpecified::No))
+            return true;
+        }
+        break;
+      }
+      case tok::kw_operator:
+        return true;
+      case tok::annot_cxxscope: // Check if this is a dtor.
+        if (NextToken().is(tok::tilde))
+          return true;
+        break;
+      default:
+        break;
+      }
+    }
+  }
+    [[fallthrough]];
     // simple-declaration
   default:
     return isCXXSimpleDeclaration(/*AllowForRangeDecl=*/false);
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -707,8 +707,7 @@
 
     // Late template parsing can begin.
     Actions.SetLateTemplateParser(LateTemplateParserCallback, nullptr, this);
-    if (!PP.isIncrementalProcessingEnabled())
-      Actions.ActOnEndOfTranslationUnit();
+    Actions.ActOnEndOfTranslationUnit();
     //else don't tell Sema that we ended parsing: more input might come.
     return true;
 
@@ -1029,8 +1028,13 @@
       ConsumeToken();
       return nullptr;
     }
+    if (PP.isIncrementalProcessingEnabled() &&
+        !isDeclarationStatement(/*DisambiguatingWithExpression=*/true))
+      return ParseTopLevelStmtDecl();
+
     // We can't tell whether this is a function-definition or declaration yet.
-    return ParseDeclarationOrFunctionDefinition(Attrs, DeclSpecAttrs, DS);
+    if (!SingleDecl)
+      return ParseDeclarationOrFunctionDefinition(Attrs, DeclSpecAttrs, DS);
   }
 
   // This routine returns a DeclGroup, if the thing we parsed only contains a
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
@@ -19550,6 +19550,12 @@
   return New;
 }
 
+Decl *Sema::ActOnTopLevelStmtDecl(Stmt *Statement) {
+  auto *New = TopLevelStmtDecl::Create(Context, Statement);
+  Context.getTranslationUnitDecl()->addDecl(New);
+  return New;
+}
+
 void Sema::ActOnPragmaRedefineExtname(IdentifierInfo* Name,
                                       IdentifierInfo* AliasName,
                                       SourceLocation PragmaLoc,
diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
--- a/clang/lib/Serialization/ASTCommon.cpp
+++ b/clang/lib/Serialization/ASTCommon.cpp
@@ -412,6 +412,7 @@
   case Decl::PragmaComment:
   case Decl::PragmaDetectMismatch:
   case Decl::FileScopeAsm:
+  case Decl::TopLevelStmt:
   case Decl::AccessSpec:
   case Decl::Friend:
   case Decl::FriendTemplate:
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
@@ -402,6 +402,7 @@
     void VisitLinkageSpecDecl(LinkageSpecDecl *D);
     void VisitExportDecl(ExportDecl *D);
     void VisitFileScopeAsmDecl(FileScopeAsmDecl *AD);
+    void VisitTopLevelStmtDecl(TopLevelStmtDecl *D);
     void VisitImportDecl(ImportDecl *D);
     void VisitAccessSpecDecl(AccessSpecDecl *D);
     void VisitFriendDecl(FriendDecl *D);
@@ -1678,6 +1679,11 @@
   AD->setRParenLoc(readSourceLocation());
 }
 
+void ASTDeclReader::VisitTopLevelStmtDecl(TopLevelStmtDecl *D) {
+  VisitDecl(D);
+  D->Statement = Record.readStmt();
+}
+
 void ASTDeclReader::VisitBlockDecl(BlockDecl *BD) {
   VisitDecl(BD);
   BD->setBody(cast_or_null<CompoundStmt>(Record.readStmt()));
@@ -3022,8 +3028,8 @@
       return false;
   }
 
-  if (isa<FileScopeAsmDecl, ObjCProtocolDecl, ObjCImplDecl, ImportDecl,
-          PragmaCommentDecl, PragmaDetectMismatchDecl>(D))
+  if (isa<FileScopeAsmDecl, TopLevelStmtDecl, ObjCProtocolDecl, ObjCImplDecl,
+          ImportDecl, PragmaCommentDecl, PragmaDetectMismatchDecl>(D))
     return true;
   if (isa<OMPThreadPrivateDecl, OMPDeclareReductionDecl, OMPDeclareMapperDecl,
           OMPAllocateDecl, OMPRequiresDecl>(D))
@@ -3829,6 +3835,9 @@
   case DECL_FILE_SCOPE_ASM:
     D = FileScopeAsmDecl::CreateDeserialized(Context, ID);
     break;
+  case DECL_TOP_LEVEL_STMT_DECL:
+    D = TopLevelStmtDecl::CreateDeserialized(Context, ID);
+    break;
   case DECL_BLOCK:
     D = BlockDecl::CreateDeserialized(Context, ID);
     break;
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -124,6 +124,7 @@
     void VisitLinkageSpecDecl(LinkageSpecDecl *D);
     void VisitExportDecl(ExportDecl *D);
     void VisitFileScopeAsmDecl(FileScopeAsmDecl *D);
+    void VisitTopLevelStmtDecl(TopLevelStmtDecl *D);
     void VisitImportDecl(ImportDecl *D);
     void VisitAccessSpecDecl(AccessSpecDecl *D);
     void VisitFriendDecl(FriendDecl *D);
@@ -1171,6 +1172,12 @@
   Code = serialization::DECL_FILE_SCOPE_ASM;
 }
 
+void ASTDeclWriter::VisitTopLevelStmtDecl(TopLevelStmtDecl *D) {
+  VisitDecl(D);
+  Record.AddStmt(D->getStmt());
+  Code = serialization::DECL_TOP_LEVEL_STMT_DECL;
+}
+
 void ASTDeclWriter::VisitEmptyDecl(EmptyDecl *D) {
   VisitDecl(D);
   Code = serialization::DECL_EMPTY;
@@ -2418,7 +2425,7 @@
 
   // File scoped assembly or obj-c or OMP declare target implementation must be
   // seen.
-  if (isa<FileScopeAsmDecl, ObjCImplDecl>(D))
+  if (isa<FileScopeAsmDecl, TopLevelStmtDecl, ObjCImplDecl>(D))
     return true;
 
   if (WritingModule && isPartOfPerModuleInitializer(D)) {
diff --git a/clang/test/Interpreter/disambiguate-decl-stmt.cpp b/clang/test/Interpreter/disambiguate-decl-stmt.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Interpreter/disambiguate-decl-stmt.cpp
@@ -0,0 +1,56 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fincremental-extensions -std=c++20 %s
+// RUN: %clang_cc1 -fsyntax-only -DMS -fms-extensions -verify -fincremental-extensions -std=c++20 %s
+
+// expected-no-diagnostics
+
+extern "C" int printf(const char*,...);
+
+// Decls which are hard to disambiguate
+
+// ParseStatementOrDeclaration returns multiple statements.
+#ifdef MS
+int g_bFlag = 1;
+__if_exists(::g_bFlag) {
+  printf("Entering __if_exists\n");
+  printf("g_bFlag = %d\n", g_bFlag);
+}
+#endif // MS
+
+// Operators.
+struct S1 { operator int(); };
+S1::operator int() { return 0; }
+
+// Dtors
+using I = int;
+I x = 10;
+x.I::~I();
+x = 20;
+
+// Ctors
+
+// Deduction guide
+template<typename T> struct A { A(); A(T); };
+A() -> A<int>;
+
+struct S2 { S2(); };
+S2::S2() = default;
+
+namespace N { struct S { S(); }; }
+N::S::S() { printf("N::S::S()\n"); }
+N::S s;
+
+namespace Ns {namespace Ns { void Ns(); void Fs();}}
+void Ns::Ns::Ns() { printf("void Ns::Ns::Ns()\n"); }
+void Ns::Ns::Fs() {}
+
+Ns::Ns::Fs();
+Ns::Ns::Ns();
+
+struct Attrs1 { Attrs1(); };
+Attrs1::Attrs1() __attribute((pure)) = default;
+
+struct Attrs2 { Attrs2(); };
+__attribute((pure)) Attrs2::Attrs2() = default;
+
+// Extra semicolon
+namespace N {};
diff --git a/clang/test/Interpreter/execute-stmts.cpp b/clang/test/Interpreter/execute-stmts.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Interpreter/execute-stmts.cpp
@@ -0,0 +1,38 @@
+// REQUIRES: host-supports-jit
+// UNSUPPORTED: system-aix
+// RUN: cat %s | clang-repl -Xcc -Xclang -Xcc  -verify | FileCheck %s
+// RUN: %clang_cc1 -verify -fincremental-extensions -emit-llvm -o -  %s \
+// RUN:           | FileCheck --check-prefix=CODEGEN-CHECK %s
+
+// expected-no-diagnostics
+
+//CODEGEN-CHECK-COUNT-2: define internal void @__stmts__
+//CODEGEN-CHECK-NOT: define internal void @__stmts__
+
+
+extern "C" int printf(const char*,...);
+
+template <typename T> T call() { printf("called\n"); return T(); }
+call<int>();
+// CHECK: called
+
+int i = 1;
+++i;
+printf("i = %d\n", i);
+// CHECK: i = 2
+
+namespace Ns { void f(){ i++; } }
+Ns::f();
+
+void g() { ++i; }
+g();
+::g();
+
+printf("i = %d\n", i);
+// CHECK-NEXT: i = 5
+
+for (; i > 4; --i) printf("i = %d\n", i);
+// CHECK-NEXT: i = 5
+
+int j = i; printf("j = %d\n", j);
+// CHECK-NEXT: j = 4
diff --git a/clang/test/Interpreter/stmt-serialization.cpp b/clang/test/Interpreter/stmt-serialization.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Interpreter/stmt-serialization.cpp
@@ -0,0 +1,19 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -std=c++20 -fincremental-extensions -fmodules-cache-path=%t \
+// RUN:            -x c++ %s -verify
+// expected-no-diagnostics
+
+#pragma clang module build TopLevelStmt
+module TopLevelStmt { module Statements {} }
+#pragma clang module contents
+
+#pragma clang module begin TopLevelStmt.Statements
+extern "C" int printf(const char*,...);
+int i = 0;
+i++;
+#pragma clang module end /*TopLevelStmt.Statements*/
+#pragma clang module endbuild /*TopLevelStmt*/
+
+#pragma clang module import TopLevelStmt.Statements
+
+printf("Value of i is '%d'", i);
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -6696,6 +6696,7 @@
   case Decl::Export:
   case Decl::ObjCPropertyImpl:
   case Decl::FileScopeAsm:
+  case Decl::TopLevelStmt:
   case Decl::StaticAssert:
   case Decl::Block:
   case Decl::Captured:
diff --git a/clang/unittests/Interpreter/InterpreterTest.cpp b/clang/unittests/Interpreter/InterpreterTest.cpp
--- a/clang/unittests/Interpreter/InterpreterTest.cpp
+++ b/clang/unittests/Interpreter/InterpreterTest.cpp
@@ -124,14 +124,8 @@
   auto *PTU1 = R1->TUPart;
   EXPECT_EQ(2U, DeclsSize(PTU1));
 
-  // FIXME: Add support for wrapping and running statements.
   auto R2 = Interp->Parse("var1++; printf(\"var1 value %d\\n\", var1);");
-  EXPECT_FALSE(!!R2);
-  using ::testing::HasSubstr;
-  EXPECT_THAT(DiagnosticsOS.str(),
-              HasSubstr("error: unknown type name 'var1'"));
-  auto Err = R2.takeError();
-  EXPECT_EQ("Parsing failed.", llvm::toString(std::move(Err)));
+  EXPECT_TRUE(!!R2);
 }
 
 TEST(InterpreterTest, UndoCommand) {