diff --git a/clang/include/clang/Lex/ExternalPreprocessorSource.h b/clang/include/clang/Lex/ExternalPreprocessorSource.h
@@ -31,7 +31,7 @@ class ExternalPreprocessorSource {
   virtual void ReadDefinedMacros() = 0;
 
   /// Update an out-of-date identifier.
-  virtual void updateOutOfDateIdentifier(IdentifierInfo &II) = 0;
+  virtual void updateOutOfDateIdentifier(const IdentifierInfo &II) = 0;
 
   /// Return the identifier associated with the given ID number.
   ///

diff --git a/clang/include/clang/Lex/HeaderSearch.h b/clang/include/clang/Lex/HeaderSearch.h
@@ -547,14 +547,15 @@ class HeaderSearch {
   /// Return whether the specified file is a normal header,
   /// a system header, or a C++ friendly system header.
   SrcMgr::CharacteristicKind getFileDirFlavor(FileEntryRef File) {
-    return (SrcMgr::CharacteristicKind)getFileInfo(File).DirInfo;
+    if (const HeaderFileInfo *HFI = getExistingFileInfo(File))
+      return (SrcMgr::CharacteristicKind)HFI->DirInfo;
+    return (SrcMgr::CharacteristicKind)HeaderFileInfo().DirInfo;
   }
 
   /// Mark the specified file as a "once only" file due to
   /// \#pragma once.
   void MarkFileIncludeOnce(FileEntryRef File) {
-    HeaderFileInfo &FI = getFileInfo(File);
-    FI.isPragmaOnce = true;
+    getFileInfo(File).isPragmaOnce = true;
   }
 
   /// Mark the specified file as a system header, e.g. due to
@@ -834,16 +835,17 @@ class HeaderSearch {
 
   unsigned header_file_size() const { return FileInfo.size(); }
 
-  /// Return the HeaderFileInfo structure for the specified FileEntry,
-  /// in preparation for updating it in some way.
+  /// Return the HeaderFileInfo structure for the specified FileEntry, in
+  /// preparation for updating it in some way.
   HeaderFileInfo &getFileInfo(FileEntryRef FE);
 
-  /// Return the HeaderFileInfo structure for the specified FileEntry,
-  /// if it has ever been filled in.
-  /// \param WantExternal Whether the caller wants purely-external header file
-  ///        info (where \p External is true).
-  const HeaderFileInfo *getExistingFileInfo(FileEntryRef FE,
-                                            bool WantExternal = true) const;
+  /// Return the HeaderFileInfo structure for the specified FileEntry, if it has
+  /// ever been filled in (either locally or externally).
+  const HeaderFileInfo *getExistingFileInfo(FileEntryRef FE) const;
+
+  /// Return the headerFileInfo structure for the specified FileEntry, if it has
+  /// ever been filled in locally.
+  const HeaderFileInfo *getExistingLocalFileInfo(FileEntryRef FE) const;
 
   SearchDirIterator search_dir_begin() { return {*this, 0}; }
   SearchDirIterator search_dir_end() { return {*this, SearchDirs.size()}; }

diff --git a/clang/include/clang/Lex/MacroInfo.h b/clang/include/clang/Lex/MacroInfo.h
@@ -515,7 +515,7 @@ class ModuleMacro : public llvm::FoldingSetNode {
   friend class Preprocessor;
 
   /// The name defined by the macro.
-  IdentifierInfo *II;
+  const IdentifierInfo *II;
 
   /// The body of the #define, or nullptr if this is a #undef.
   MacroInfo *Macro;
@@ -529,7 +529,7 @@ class ModuleMacro : public llvm::FoldingSetNode {
   /// The number of modules whose macros are directly overridden by this one.
   unsigned NumOverrides;
 
-  ModuleMacro(Module *OwningModule, IdentifierInfo *II, MacroInfo *Macro,
+  ModuleMacro(Module *OwningModule, const IdentifierInfo *II, MacroInfo *Macro,
               ArrayRef<ModuleMacro *> Overrides)
       : II(II), Macro(Macro), OwningModule(OwningModule),
         NumOverrides(Overrides.size()) {
@@ -539,7 +539,7 @@ class ModuleMacro : public llvm::FoldingSetNode {
 
 public:
   static ModuleMacro *create(Preprocessor &PP, Module *OwningModule,
-                             IdentifierInfo *II, MacroInfo *Macro,
+                             const IdentifierInfo *II, MacroInfo *Macro,
                              ArrayRef<ModuleMacro *> Overrides);
 
   void Profile(llvm::FoldingSetNodeID &ID) const {
@@ -553,7 +553,7 @@ class ModuleMacro : public llvm::FoldingSetNode {
   }
 
   /// Get the name of the macro.
-  IdentifierInfo *getName() const { return II; }
+  const IdentifierInfo *getName() const { return II; }
 
   /// Get the ID of the module that exports this macro.
   Module *getOwningModule() const { return OwningModule; }

diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
@@ -836,7 +836,7 @@ class Preprocessor {
     ModuleMacroInfo *getModuleInfo(Preprocessor &PP,
                                    const IdentifierInfo *II) const {
       if (II->isOutOfDate())
-        PP.updateOutOfDateIdentifier(const_cast<IdentifierInfo&>(*II));
+        PP.updateOutOfDateIdentifier(*II);
       // FIXME: Find a spare bit on IdentifierInfo and store a
       //        HasModuleMacros flag.
       if (!II->hasMacroDefinition() ||
@@ -1162,7 +1162,7 @@ class Preprocessor {
   /// skipped.
   llvm::DenseMap<const char *, unsigned> RecordedSkippedRanges;
 
-  void updateOutOfDateIdentifier(IdentifierInfo &II) const;
+  void updateOutOfDateIdentifier(const IdentifierInfo &II) const;
 
 public:
   Preprocessor(std::shared_ptr<PreprocessorOptions> PPOpts,
@@ -1432,14 +1432,15 @@ class Preprocessor {
                                MacroDirective *MD);
 
   /// Register an exported macro for a module and identifier.
-  ModuleMacro *addModuleMacro(Module *Mod, IdentifierInfo *II, MacroInfo *Macro,
+  ModuleMacro *addModuleMacro(Module *Mod, const IdentifierInfo *II,
+                              MacroInfo *Macro,
                               ArrayRef<ModuleMacro *> Overrides, bool &IsNew);
   ModuleMacro *getModuleMacro(Module *Mod, const IdentifierInfo *II);
 
   /// Get the list of leaf (non-overridden) module macros for a name.
   ArrayRef<ModuleMacro*> getLeafModuleMacros(const IdentifierInfo *II) const {
     if (II->isOutOfDate())
-      updateOutOfDateIdentifier(const_cast<IdentifierInfo&>(*II));
+      updateOutOfDateIdentifier(*II);
     auto I = LeafModuleMacros.find(II);
     if (I != LeafModuleMacros.end())
       return I->second;

diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
@@ -329,7 +329,7 @@ class Parser : public CodeCompletionHandler {
   };
 
   /// Identifiers which have been declared within a tentative parse.
-  SmallVector<IdentifierInfo *, 8> TentativelyDeclaredIdentifiers;
+  SmallVector<const IdentifierInfo *, 8> TentativelyDeclaredIdentifiers;
 
   /// Tracker for '<' tokens that might have been intended to be treated as an
   /// angle bracket instead of a less-than comparison.
@@ -1927,15 +1927,11 @@ class Parser : public CodeCompletionHandler {
                                   bool EnteringContext, IdentifierInfo &II,
                                   CXXScopeSpec &SS);
 
-  bool ParseOptionalCXXScopeSpecifier(CXXScopeSpec &SS,
-                                      ParsedType ObjectType,
-                                      bool ObjectHasErrors,
-                                      bool EnteringContext,
-                                      bool *MayBePseudoDestructor = nullptr,
-                                      bool IsTypename = false,
-                                      IdentifierInfo **LastII = nullptr,
-                                      bool OnlyNamespace = false,
-                                      bool InUsingDeclaration = false);
+  bool ParseOptionalCXXScopeSpecifier(
+      CXXScopeSpec &SS, ParsedType ObjectType, bool ObjectHasErrors,
+      bool EnteringContext, bool *MayBePseudoDestructor = nullptr,
+      bool IsTypename = false, const IdentifierInfo **LastII = nullptr,
+      bool OnlyNamespace = false, bool InUsingDeclaration = false);
 
   //===--------------------------------------------------------------------===//
   // C++11 5.1.2: Lambda expressions
@@ -3615,6 +3611,9 @@ class Parser : public CodeCompletionHandler {
   OpenACCClauseParseResult OpenACCCannotContinue();
   OpenACCClauseParseResult OpenACCSuccess(OpenACCClause *Clause);
 
+  using OpenACCConditionExprParseResult =
+      std::pair<ExprResult, OpenACCParseCanContinue>;
+
   /// Parses the OpenACC directive (the entire pragma) including the clause
   /// list, but does not produce the main AST node.
   OpenACCDirectiveParseInfo ParseOpenACCDirective();
@@ -3661,6 +3660,8 @@ class Parser : public CodeCompletionHandler {
   bool ParseOpenACCGangArgList();
   /// Parses a 'gang-arg', used for the 'gang' clause.
   bool ParseOpenACCGangArg();
+  /// Parses a 'condition' expr, ensuring it results in a
+  ExprResult ParseOpenACCConditionExpr();
 
 private:
   //===--------------------------------------------------------------------===//

diff --git a/clang/include/clang/Sema/CodeCompleteConsumer.h b/clang/include/clang/Sema/CodeCompleteConsumer.h
@@ -362,7 +362,7 @@ class CodeCompletionContext {
   QualType BaseType;
 
   /// The identifiers for Objective-C selector parts.
-  ArrayRef<IdentifierInfo *> SelIdents;
+  ArrayRef<const IdentifierInfo *> SelIdents;
 
   /// The scope specifier that comes before the completion token e.g.
   /// "a::b::"
@@ -378,8 +378,9 @@ class CodeCompletionContext {
       : CCKind(CCKind), IsUsingDeclaration(false), SelIdents(std::nullopt) {}
 
   /// Construct a new code-completion context of the given kind.
-  CodeCompletionContext(Kind CCKind, QualType T,
-                        ArrayRef<IdentifierInfo *> SelIdents = std::nullopt)
+  CodeCompletionContext(
+      Kind CCKind, QualType T,
+      ArrayRef<const IdentifierInfo *> SelIdents = std::nullopt)
       : CCKind(CCKind), IsUsingDeclaration(false), SelIdents(SelIdents) {
     if (CCKind == CCC_DotMemberAccess || CCKind == CCC_ArrowMemberAccess ||
         CCKind == CCC_ObjCPropertyAccess || CCKind == CCC_ObjCClassMessage ||
@@ -406,7 +407,7 @@ class CodeCompletionContext {
   QualType getBaseType() const { return BaseType; }
 
   /// Retrieve the Objective-C selector identifiers.
-  ArrayRef<IdentifierInfo *> getSelIdents() const { return SelIdents; }
+  ArrayRef<const IdentifierInfo *> getSelIdents() const { return SelIdents; }
 
   /// Determines whether we want C++ constructors as results within this
   /// context.

diff --git a/clang/include/clang/Sema/DeclSpec.h b/clang/include/clang/Sema/DeclSpec.h
@@ -1049,7 +1049,7 @@ class UnqualifiedId {
   union {
     /// When Kind == IK_Identifier, the parsed identifier, or when
     /// Kind == IK_UserLiteralId, the identifier suffix.
-    IdentifierInfo *Identifier;
+    const IdentifierInfo *Identifier;
 
     /// When Kind == IK_OperatorFunctionId, the overloaded operator
     /// that we parsed.
@@ -1111,7 +1111,7 @@ class UnqualifiedId {
   /// \param IdLoc the location of the parsed identifier.
   void setIdentifier(const IdentifierInfo *Id, SourceLocation IdLoc) {
     Kind = UnqualifiedIdKind::IK_Identifier;
-    Identifier = const_cast<IdentifierInfo *>(Id);
+    Identifier = Id;
     StartLocation = EndLocation = IdLoc;
   }
 
@@ -1154,9 +1154,9 @@ class UnqualifiedId {
   ///
   /// \param IdLoc the location of the identifier.
   void setLiteralOperatorId(const IdentifierInfo *Id, SourceLocation OpLoc,
-                              SourceLocation IdLoc) {
+                            SourceLocation IdLoc) {
     Kind = UnqualifiedIdKind::IK_LiteralOperatorId;
-    Identifier = const_cast<IdentifierInfo *>(Id);
+    Identifier = Id;
     StartLocation = OpLoc;
     EndLocation = IdLoc;
   }
@@ -1225,7 +1225,7 @@ class UnqualifiedId {
   /// \param Id the identifier.
   void setImplicitSelfParam(const IdentifierInfo *Id) {
     Kind = UnqualifiedIdKind::IK_ImplicitSelfParam;
-    Identifier = const_cast<IdentifierInfo *>(Id);
+    Identifier = Id;
     StartLocation = EndLocation = SourceLocation();
   }
 
@@ -1327,7 +1327,7 @@ struct DeclaratorChunk {
   /// Parameter type lists will have type info (if the actions module provides
   /// it), but may have null identifier info: e.g. for 'void foo(int X, int)'.
   struct ParamInfo {
-    IdentifierInfo *Ident;
+    const IdentifierInfo *Ident;
     SourceLocation IdentLoc;
     Decl *Param;
 
@@ -1339,11 +1339,10 @@ struct DeclaratorChunk {
     std::unique_ptr<CachedTokens> DefaultArgTokens;
 
     ParamInfo() = default;
-    ParamInfo(IdentifierInfo *ident, SourceLocation iloc,
-              Decl *param,
+    ParamInfo(const IdentifierInfo *ident, SourceLocation iloc, Decl *param,
               std::unique_ptr<CachedTokens> DefArgTokens = nullptr)
-      : Ident(ident), IdentLoc(iloc), Param(param),
-        DefaultArgTokens(std::move(DefArgTokens)) {}
+        : Ident(ident), IdentLoc(iloc), Param(param),
+          DefaultArgTokens(std::move(DefArgTokens)) {}
   };
 
   struct TypeAndRange {
@@ -2326,7 +2325,7 @@ class Declarator {
     return BindingGroup.isSet();
   }
 
-  IdentifierInfo *getIdentifier() const {
+  const IdentifierInfo *getIdentifier() const {
     if (Name.getKind() == UnqualifiedIdKind::IK_Identifier)
       return Name.Identifier;
 
@@ -2335,7 +2334,7 @@ class Declarator {
   SourceLocation getIdentifierLoc() const { return Name.StartLocation; }
 
   /// Set the name of this declarator to be the given identifier.
-  void SetIdentifier(IdentifierInfo *Id, SourceLocation IdLoc) {
+  void SetIdentifier(const IdentifierInfo *Id, SourceLocation IdLoc) {
     Name.setIdentifier(Id, IdLoc);
   }
 

diff --git a/clang/include/clang/Sema/ParsedTemplate.h b/clang/include/clang/Sema/ParsedTemplate.h
@@ -159,7 +159,7 @@ namespace clang {
     SourceLocation TemplateNameLoc;
 
     /// FIXME: Temporarily stores the name of a specialization
-    IdentifierInfo *Name;
+    const IdentifierInfo *Name;
 
     /// FIXME: Temporarily stores the overloaded operator kind.
     OverloadedOperatorKind Operator;
@@ -197,7 +197,7 @@ namespace clang {
     /// appends it to List.
     static TemplateIdAnnotation *
     Create(SourceLocation TemplateKWLoc, SourceLocation TemplateNameLoc,
-           IdentifierInfo *Name, OverloadedOperatorKind OperatorKind,
+           const IdentifierInfo *Name, OverloadedOperatorKind OperatorKind,
            ParsedTemplateTy OpaqueTemplateName, TemplateNameKind TemplateKind,
            SourceLocation LAngleLoc, SourceLocation RAngleLoc,
            ArrayRef<ParsedTemplateArgument> TemplateArgs, bool ArgsInvalid,
@@ -236,7 +236,8 @@ namespace clang {
     TemplateIdAnnotation(const TemplateIdAnnotation &) = delete;
 
     TemplateIdAnnotation(SourceLocation TemplateKWLoc,
-                         SourceLocation TemplateNameLoc, IdentifierInfo *Name,
+                         SourceLocation TemplateNameLoc,
+                         const IdentifierInfo *Name,
                          OverloadedOperatorKind OperatorKind,
                          ParsedTemplateTy OpaqueTemplateName,
                          TemplateNameKind TemplateKind,

diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
diff --git a/clang/include/clang/Sema/SemaHLSL.h b/clang/include/clang/Sema/SemaHLSL.h
@@ -13,23 +13,42 @@
 #ifndef LLVM_CLANG_SEMA_SEMAHLSL_H
 #define LLVM_CLANG_SEMA_SEMAHLSL_H
 
+#include "clang/AST/Attr.h"
+#include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/Expr.h"
+#include "clang/Basic/AttributeCommonInfo.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/SemaBase.h"
+#include <initializer_list>
 
 namespace clang {
 
 class SemaHLSL : public SemaBase {
 public:
   SemaHLSL(Sema &S);
 
-  Decl *ActOnStartHLSLBuffer(Scope *BufferScope, bool CBuffer,
-                             SourceLocation KwLoc, IdentifierInfo *Ident,
-                             SourceLocation IdentLoc, SourceLocation LBrace);
-  void ActOnFinishHLSLBuffer(Decl *Dcl, SourceLocation RBrace);
+  Decl *ActOnStartBuffer(Scope *BufferScope, bool CBuffer, SourceLocation KwLoc,
+                         IdentifierInfo *Ident, SourceLocation IdentLoc,
+                         SourceLocation LBrace);
+  void ActOnFinishBuffer(Decl *Dcl, SourceLocation RBrace);
+  HLSLNumThreadsAttr *mergeNumThreadsAttr(Decl *D,
+                                          const AttributeCommonInfo &AL, int X,
+                                          int Y, int Z);
+  HLSLShaderAttr *mergeShaderAttr(Decl *D, const AttributeCommonInfo &AL,
+                                  HLSLShaderAttr::ShaderType ShaderType);
+  HLSLParamModifierAttr *
+  mergeParamModifierAttr(Decl *D, const AttributeCommonInfo &AL,
+                         HLSLParamModifierAttr::Spelling Spelling);
+  void ActOnTopLevelFunction(FunctionDecl *FD);
+  void CheckEntryPoint(FunctionDecl *FD);
+  void CheckSemanticAnnotation(FunctionDecl *EntryPoint, const Decl *Param,
+                               const HLSLAnnotationAttr *AnnotationAttr);
+  void DiagnoseAttrStageMismatch(
+      const Attr *A, HLSLShaderAttr::ShaderType Stage,
+      std::initializer_list<HLSLShaderAttr::ShaderType> AllowedStages);
 };
 
 } // namespace clang

diff --git a/clang/include/clang/Sema/SemaOpenACC.h b/clang/include/clang/Sema/SemaOpenACC.h
@@ -40,7 +40,11 @@ class SemaOpenACC : public SemaBase {
       OpenACCDefaultClauseKind DefaultClauseKind;
     };
 
-    std::variant<DefaultDetails> Details;
+    struct ConditionDetails {
+      Expr *ConditionExpr;
+    };
+
+    std::variant<DefaultDetails, ConditionDetails> Details;
 
   public:
     OpenACCParsedClause(OpenACCDirectiveKind DirKind,
@@ -63,6 +67,16 @@ class SemaOpenACC : public SemaBase {
       return std::get<DefaultDetails>(Details).DefaultClauseKind;
     }
 
+    const Expr *getConditionExpr() const {
+      return const_cast<OpenACCParsedClause *>(this)->getConditionExpr();
+    }
+
+    Expr *getConditionExpr() {
+      assert(ClauseKind == OpenACCClauseKind::If &&
+             "Parsed clause kind does not have a condition expr");
+      return std::get<ConditionDetails>(Details).ConditionExpr;
+    }
+
     void setLParenLoc(SourceLocation EndLoc) { LParenLoc = EndLoc; }
     void setEndLoc(SourceLocation EndLoc) { ClauseRange.setEnd(EndLoc); }
 
@@ -71,6 +85,18 @@ class SemaOpenACC : public SemaBase {
              "Parsed clause is not a default clause");
       Details = DefaultDetails{DefKind};
     }
+
+    void setConditionDetails(Expr *ConditionExpr) {
+      assert(ClauseKind == OpenACCClauseKind::If &&
+             "Parsed clause kind does not have a condition expr");
+      // In C++ we can count on this being a 'bool', but in C this gets left as
+      // some sort of scalar that codegen will have to take care of converting.
+      assert((!ConditionExpr || ConditionExpr->isInstantiationDependent() ||
+              ConditionExpr->getType()->isScalarType()) &&
+             "Condition expression type not scalar/dependent");
+
+      Details = ConditionDetails{ConditionExpr};
+    }
   };
 
   SemaOpenACC(Sema &S);

diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -698,6 +698,10 @@ enum ASTRecordTypes {
   /// Record code for an unterminated \#pragma clang assume_nonnull begin
   /// recorded in a preamble.
   PP_ASSUME_NONNULL_LOC = 67,
+
+  /// Record code for lexical and visible block for delayed namespace in
+  /// reduced BMI.
+  DELAYED_NAMESPACE_LEXICAL_VISIBLE_RECORD = 68,
 };
 
 /// Record types used within a source manager block.

diff --git a/clang/include/clang/Serialization/ASTReader.h b/clang/include/clang/Serialization/ASTReader.h
@@ -517,6 +517,20 @@ class ASTReader
   /// in the chain.
   DeclUpdateOffsetsMap DeclUpdateOffsets;
 
+  using DelayedNamespaceOffsetMapTy = llvm::DenseMap<
+      serialization::DeclID,
+      std::pair</*LexicalOffset*/ uint64_t, /*VisibleOffset*/ uint64_t>>;
+
+  /// Mapping from global declaration IDs to the lexical and visible block
+  /// offset for delayed namespace in reduced BMI.
+  ///
+  /// We can't use the existing DeclUpdate mechanism since the DeclUpdate
+  /// may only be applied in an outer most read. However, we need to know
+  /// whether or not a DeclContext has external storage during the recursive
+  /// reading. So we need to apply the offset immediately after we read the
+  /// namespace as if it is not delayed.
+  DelayedNamespaceOffsetMapTy DelayedNamespaceOffsetMap;
+
   struct PendingUpdateRecord {
     Decl *D;
     serialization::GlobalDeclID ID;
@@ -1082,12 +1096,12 @@ class ASTReader
 
   /// The set of lookup results that we have faked in order to support
   /// merging of partially deserialized decls but that we have not yet removed.
-  llvm::SmallMapVector<IdentifierInfo *, SmallVector<NamedDecl*, 2>, 16>
-    PendingFakeLookupResults;
+  llvm::SmallMapVector<const IdentifierInfo *, SmallVector<NamedDecl *, 2>, 16>
+      PendingFakeLookupResults;
 
   /// The generation number of each identifier, which keeps track of
   /// the last time we loaded information about this identifier.
-  llvm::DenseMap<IdentifierInfo *, unsigned> IdentifierGeneration;
+  llvm::DenseMap<const IdentifierInfo *, unsigned> IdentifierGeneration;
 
   /// Contains declarations and definitions that could be
   /// "interesting" to the ASTConsumer, when we get that AST consumer.
@@ -1492,6 +1506,7 @@ class ASTReader
   getModuleFileLevelDecls(ModuleFile &Mod);
 
 private:
+  bool isConsumerInterestedIn(Decl *D);
   void PassInterestingDeclsToConsumer();
   void PassInterestingDeclToConsumer(Decl *D);
 
@@ -2330,10 +2345,10 @@ class ASTReader
   void ReadDefinedMacros() override;
 
   /// Update an out-of-date identifier.
-  void updateOutOfDateIdentifier(IdentifierInfo &II) override;
+  void updateOutOfDateIdentifier(const IdentifierInfo &II) override;
 
   /// Note that this identifier is up-to-date.
-  void markIdentifierUpToDate(IdentifierInfo *II);
+  void markIdentifierUpToDate(const IdentifierInfo *II);
 
   /// Load all external visible decls in the given DeclContext.
   void completeVisibleDeclsMap(const DeclContext *DC) override;

diff --git a/clang/include/clang/Serialization/ASTWriter.h b/clang/include/clang/Serialization/ASTWriter.h
@@ -201,6 +201,16 @@ class ASTWriter : public ASTDeserializationListener,
   /// The declarations and types to emit.
   std::queue<DeclOrType> DeclTypesToEmit;
 
+  /// The delayed namespace to emit. Only meaningful for reduced BMI.
+  ///
+  /// In reduced BMI, we want to elide the unreachable declarations in
+  /// the global module fragment. However, in ASTWriterDecl, when we see
+  /// a namespace, all the declarations in the namespace would be emitted.
+  /// So the optimization become meaningless. To solve the issue, we
+  /// delay recording all the declarations until we emit all the declarations.
+  /// Then we can safely record the reached declarations only.
+  llvm::SmallVector<NamespaceDecl *, 16> DelayedNamespace;
+
   /// The first ID number we can use for our own declarations.
   serialization::DeclID FirstDeclID = serialization::NUM_PREDEF_DECL_IDS;
 
@@ -529,7 +539,8 @@ class ASTWriter : public ASTDeserializationListener,
   void WriteType(QualType T);
 
   bool isLookupResultExternal(StoredDeclsList &Result, DeclContext *DC);
-  bool isLookupResultEntirelyExternal(StoredDeclsList &Result, DeclContext *DC);
+  bool isLookupResultEntirelyExternalOrUnreachable(StoredDeclsList &Result,
+                                                   DeclContext *DC);
 
   void GenerateNameLookupTable(const DeclContext *DC,
                                llvm::SmallVectorImpl<char> &LookupTable);
@@ -704,6 +715,15 @@ class ASTWriter : public ASTDeserializationListener,
   /// declaration.
   serialization::DeclID getDeclID(const Decl *D);
 
+  /// Whether or not the declaration got emitted. If not, it wouldn't be
+  /// emitted.
+  ///
+  /// This may only be called after we've done the job to write the
+  /// declarations (marked by DoneWritingDeclsAndTypes).
+  ///
+  /// A declaration may only be omitted in reduced BMI.
+  bool wasDeclEmitted(const Decl *D) const;
+
   unsigned getAnonymousDeclarationNumber(const NamedDecl *D);
 
   /// Add a string to the given record.
@@ -798,6 +818,10 @@ class ASTWriter : public ASTDeserializationListener,
     return WritingModule && WritingModule->isNamedModule();
   }
 
+  bool isGeneratingReducedBMI() const { return GeneratingReducedBMI; }
+
+  bool getDoneWritingDeclsAndTypes() const { return DoneWritingDeclsAndTypes; }
+
 private:
   // ASTDeserializationListener implementation
   void ReaderInitialized(ASTReader *Reader) override;

diff --git a/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h b/clang/include/clang/Tooling/DependencyScanning/DependencyScanningFilesystem.h
@@ -142,6 +142,8 @@ class CachedFileSystemEntry {
   CachedFileContents *Contents;
 };
 
+using CachedRealPath = llvm::ErrorOr<std::string>;
+
 /// This class is a shared cache, that caches the 'stat' and 'open' calls to the
 /// underlying real file system, and the scanned preprocessor directives of
 /// files.
@@ -154,9 +156,11 @@ class DependencyScanningFilesystemSharedCache {
     /// The mutex that needs to be locked before mutation of any member.
     mutable std::mutex CacheLock;
 
-    /// Map from filenames to cached entries.
-    llvm::StringMap<const CachedFileSystemEntry *, llvm::BumpPtrAllocator>
-        EntriesByFilename;
+    /// Map from filenames to cached entries and real paths.
+    llvm::StringMap<
+        std::pair<const CachedFileSystemEntry *, const CachedRealPath *>,
+        llvm::BumpPtrAllocator>
+        CacheByFilename;
 
     /// Map from unique IDs to cached entries.
     llvm::DenseMap<llvm::sys::fs::UniqueID, const CachedFileSystemEntry *>
@@ -168,6 +172,9 @@ class DependencyScanningFilesystemSharedCache {
     /// The backing storage for cached contents.
     llvm::SpecificBumpPtrAllocator<CachedFileContents> ContentsStorage;
 
+    /// The backing storage for cached real paths.
+    llvm::SpecificBumpPtrAllocator<CachedRealPath> RealPathStorage;
+
     /// Returns entry associated with the filename or nullptr if none is found.
     const CachedFileSystemEntry *findEntryByFilename(StringRef Filename) const;
 
@@ -194,6 +201,17 @@ class DependencyScanningFilesystemSharedCache {
     const CachedFileSystemEntry &
     getOrInsertEntryForFilename(StringRef Filename,
                                 const CachedFileSystemEntry &Entry);
+
+    /// Returns the real path associated with the filename or nullptr if none is
+    /// found.
+    const CachedRealPath *findRealPathByFilename(StringRef Filename) const;
+
+    /// Returns the real path associated with the filename if there is some.
+    /// Otherwise, constructs new one with the given one, associates it with the
+    /// filename and returns the result.
+    const CachedRealPath &
+    getOrEmplaceRealPathForFilename(StringRef Filename,
+                                    llvm::ErrorOr<StringRef> RealPath);
   };
 
   DependencyScanningFilesystemSharedCache();
@@ -210,14 +228,17 @@ class DependencyScanningFilesystemSharedCache {
 /// This class is a local cache, that caches the 'stat' and 'open' calls to the
 /// underlying real file system.
 class DependencyScanningFilesystemLocalCache {
-  llvm::StringMap<const CachedFileSystemEntry *, llvm::BumpPtrAllocator> Cache;
+  llvm::StringMap<
+      std::pair<const CachedFileSystemEntry *, const CachedRealPath *>,
+      llvm::BumpPtrAllocator>
+      Cache;
 
 public:
   /// Returns entry associated with the filename or nullptr if none is found.
   const CachedFileSystemEntry *findEntryByFilename(StringRef Filename) const {
     assert(llvm::sys::path::is_absolute_gnu(Filename));
     auto It = Cache.find(Filename);
-    return It == Cache.end() ? nullptr : It->getValue();
+    return It == Cache.end() ? nullptr : It->getValue().first;
   }
 
   /// Associates the given entry with the filename and returns the given entry
@@ -226,9 +247,40 @@ class DependencyScanningFilesystemLocalCache {
   insertEntryForFilename(StringRef Filename,
                          const CachedFileSystemEntry &Entry) {
     assert(llvm::sys::path::is_absolute_gnu(Filename));
-    const auto *InsertedEntry = Cache.insert({Filename, &Entry}).first->second;
-    assert(InsertedEntry == &Entry && "entry already present");
-    return *InsertedEntry;
+    auto [It, Inserted] = Cache.insert({Filename, {&Entry, nullptr}});
+    auto &[CachedEntry, CachedRealPath] = It->getValue();
+    if (!Inserted) {
+      // The file is already present in the local cache. If we got here, it only
+      // contains the real path. Let's make sure the entry is populated too.
+      assert((!CachedEntry && CachedRealPath) && "entry already present");
+      CachedEntry = &Entry;
+    }
+    return *CachedEntry;
+  }
+
+  /// Returns real path associated with the filename or nullptr if none is
+  /// found.
+  const CachedRealPath *findRealPathByFilename(StringRef Filename) const {
+    assert(llvm::sys::path::is_absolute_gnu(Filename));
+    auto It = Cache.find(Filename);
+    return It == Cache.end() ? nullptr : It->getValue().second;
+  }
+
+  /// Associates the given real path with the filename and returns the given
+  /// entry pointer (for convenience).
+  const CachedRealPath &
+  insertRealPathForFilename(StringRef Filename,
+                            const CachedRealPath &RealPath) {
+    assert(llvm::sys::path::is_absolute_gnu(Filename));
+    auto [It, Inserted] = Cache.insert({Filename, {nullptr, &RealPath}});
+    auto &[CachedEntry, CachedRealPath] = It->getValue();
+    if (!Inserted) {
+      // The file is already present in the local cache. If we got here, it only
+      // contains the entry. Let's make sure the real path is populated too.
+      assert((!CachedRealPath && CachedEntry) && "real path already present");
+      CachedRealPath = &RealPath;
+    }
+    return *CachedRealPath;
   }
 };
 
@@ -296,6 +348,9 @@ class DependencyScanningWorkerFilesystem
   llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>
   openFileForRead(const Twine &Path) override;
 
+  std::error_code getRealPath(const Twine &Path,
+                              SmallVectorImpl<char> &Output) override;
+
   std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
 
   /// Returns entry for the given filename.
@@ -402,6 +457,10 @@ class DependencyScanningWorkerFilesystem
   llvm::ErrorOr<std::string> WorkingDirForCacheLookup;
 
   void updateWorkingDirForCacheLookup();
+
+  llvm::ErrorOr<StringRef>
+  tryGetFilenameForLookup(StringRef OriginalFilename,
+                          llvm::SmallVectorImpl<char> &PathBuf) const;
 };
 
 } // end namespace dependencies

diff --git a/clang/lib/ARCMigrate/ObjCMT.cpp b/clang/lib/ARCMigrate/ObjCMT.cpp
@@ -1144,7 +1144,7 @@ static bool IsValidIdentifier(ASTContext &Ctx,
     return false;
   std::string NameString = Name;
   NameString[0] = toLowercase(NameString[0]);
-  IdentifierInfo *II = &Ctx.Idents.get(NameString);
+  const IdentifierInfo *II = &Ctx.Idents.get(NameString);
   return II->getTokenID() ==  tok::identifier;
 }
 
@@ -1166,7 +1166,7 @@ bool ObjCMigrateASTConsumer::migrateProperty(ASTContext &Ctx,
   if (OIT_Family != OIT_None)
     return false;
 
-  IdentifierInfo *getterName = GetterSelector.getIdentifierInfoForSlot(0);
+  const IdentifierInfo *getterName = GetterSelector.getIdentifierInfoForSlot(0);
   Selector SetterSelector =
   SelectorTable::constructSetterSelector(PP.getIdentifierTable(),
                                          PP.getSelectorTable(),
@@ -1311,7 +1311,8 @@ void ObjCMigrateASTConsumer::migrateFactoryMethod(ASTContext &Ctx,
   std::string StringLoweredClassName = LoweredClassName.lower();
   LoweredClassName = StringLoweredClassName;
 
-  IdentifierInfo *MethodIdName = OM->getSelector().getIdentifierInfoForSlot(0);
+  const IdentifierInfo *MethodIdName =
+      OM->getSelector().getIdentifierInfoForSlot(0);
   // Handle method with no name at its first selector slot; e.g. + (id):(int)x.
   if (!MethodIdName)
     return;

diff --git a/clang/lib/ARCMigrate/TransAPIUses.cpp b/clang/lib/ARCMigrate/TransAPIUses.cpp
@@ -41,7 +41,7 @@ class APIChecker : public RecursiveASTVisitor<APIChecker> {
     getReturnValueSel = sels.getUnarySelector(&ids.get("getReturnValue"));
     setReturnValueSel = sels.getUnarySelector(&ids.get("setReturnValue"));
 
-    IdentifierInfo *selIds[2];
+    const IdentifierInfo *selIds[2];
     selIds[0] = &ids.get("getArgument");
     selIds[1] = &ids.get("atIndex");
     getArgumentSel = sels.getSelector(2, selIds);

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
@@ -799,7 +799,7 @@ ASTContext::getCanonicalTemplateTemplateParmDecl(
 
   TemplateTemplateParmDecl *CanonTTP = TemplateTemplateParmDecl::Create(
       *this, getTranslationUnitDecl(), SourceLocation(), TTP->getDepth(),
-      TTP->getPosition(), TTP->isParameterPack(), nullptr,
+      TTP->getPosition(), TTP->isParameterPack(), nullptr, /*Typename=*/false,
       TemplateParameterList::Create(*this, SourceLocation(), SourceLocation(),
                                     CanonParams, SourceLocation(),
                                     /*RequiresClause=*/nullptr));
@@ -6929,16 +6929,13 @@ ASTContext::getCanonicalNestedNameSpecifier(NestedNameSpecifier *NNS) const {
     //   typedef typename T::type T1;
     //   typedef typename T1::type T2;
     if (const auto *DNT = T->getAs<DependentNameType>())
-      return NestedNameSpecifier::Create(
-          *this, DNT->getQualifier(),
-          const_cast<IdentifierInfo *>(DNT->getIdentifier()));
+      return NestedNameSpecifier::Create(*this, DNT->getQualifier(),
+                                         DNT->getIdentifier());
     if (const auto *DTST = T->getAs<DependentTemplateSpecializationType>())
-      return NestedNameSpecifier::Create(*this, DTST->getQualifier(), true,
-                                         const_cast<Type *>(T));
+      return NestedNameSpecifier::Create(*this, DTST->getQualifier(), true, T);
 
     // TODO: Set 'Template' parameter to true for other template types.
-    return NestedNameSpecifier::Create(*this, nullptr, false,
-                                       const_cast<Type *>(T));
+    return NestedNameSpecifier::Create(*this, nullptr, false, T);
   }
 
   case NestedNameSpecifier::Global:

diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
@@ -5952,7 +5952,8 @@ ASTNodeImporter::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
           ToD, D, Importer.getToContext(),
           Importer.getToContext().getTranslationUnitDecl(), *LocationOrErr,
           D->getDepth(), D->getPosition(), D->isParameterPack(),
-          (*NameOrErr).getAsIdentifierInfo(), *TemplateParamsOrErr))
+          (*NameOrErr).getAsIdentifierInfo(), D->wasDeclaredWithTypename(),
+          *TemplateParamsOrErr))
     return ToD;
 
   if (D->hasDefaultArgument()) {
@@ -8383,8 +8384,8 @@ ASTNodeImporter::VisitCXXPseudoDestructorExpr(CXXPseudoDestructorExpr *E) {
     return std::move(Err);
 
   PseudoDestructorTypeStorage Storage;
-  if (IdentifierInfo *FromII = E->getDestroyedTypeIdentifier()) {
-    IdentifierInfo *ToII = Importer.Import(FromII);
+  if (const IdentifierInfo *FromII = E->getDestroyedTypeIdentifier()) {
+    const IdentifierInfo *ToII = Importer.Import(FromII);
     ExpectedSLoc ToDestroyedTypeLocOrErr = import(E->getDestroyedTypeLoc());
     if (!ToDestroyedTypeLocOrErr)
       return ToDestroyedTypeLocOrErr.takeError();
@@ -10194,7 +10195,7 @@ Expected<Selector> ASTImporter::Import(Selector FromSel) {
   if (FromSel.isNull())
     return Selector{};
 
-  SmallVector<IdentifierInfo *, 4> Idents;
+  SmallVector<const IdentifierInfo *, 4> Idents;
   Idents.push_back(Import(FromSel.getIdentifierInfoForSlot(0)));
   for (unsigned I = 1, N = FromSel.getNumArgs(); I < N; ++I)
     Idents.push_back(Import(FromSel.getIdentifierInfoForSlot(I)));

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
@@ -2913,10 +2913,10 @@ VarDecl::setInstantiationOfStaticDataMember(VarDecl *VD,
 //===----------------------------------------------------------------------===//
 
 ParmVarDecl *ParmVarDecl::Create(ASTContext &C, DeclContext *DC,
-                                 SourceLocation StartLoc,
-                                 SourceLocation IdLoc, IdentifierInfo *Id,
-                                 QualType T, TypeSourceInfo *TInfo,
-                                 StorageClass S, Expr *DefArg) {
+                                 SourceLocation StartLoc, SourceLocation IdLoc,
+                                 const IdentifierInfo *Id, QualType T,
+                                 TypeSourceInfo *TInfo, StorageClass S,
+                                 Expr *DefArg) {
   return new (C, DC) ParmVarDecl(ParmVar, C, DC, StartLoc, IdLoc, Id, T, TInfo,
                                  S, DefArg);
 }
@@ -4511,7 +4511,7 @@ unsigned FunctionDecl::getODRHash() {
 
 FieldDecl *FieldDecl::Create(const ASTContext &C, DeclContext *DC,
                              SourceLocation StartLoc, SourceLocation IdLoc,
-                             IdentifierInfo *Id, QualType T,
+                             const IdentifierInfo *Id, QualType T,
                              TypeSourceInfo *TInfo, Expr *BW, bool Mutable,
                              InClassInitStyle InitStyle) {
   return new (C, DC) FieldDecl(Decl::Field, DC, StartLoc, IdLoc, Id, T, TInfo,
@@ -5438,7 +5438,7 @@ IndirectFieldDecl::IndirectFieldDecl(ASTContext &C, DeclContext *DC,
 
 IndirectFieldDecl *
 IndirectFieldDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
-                          IdentifierInfo *Id, QualType T,
+                          const IdentifierInfo *Id, QualType T,
                           llvm::MutableArrayRef<NamedDecl *> CH) {
   return new (C, DC) IndirectFieldDecl(C, DC, L, Id, T, CH);
 }
@@ -5461,7 +5461,8 @@ void TypeDecl::anchor() {}
 
 TypedefDecl *TypedefDecl::Create(ASTContext &C, DeclContext *DC,
                                  SourceLocation StartLoc, SourceLocation IdLoc,
-                                 IdentifierInfo *Id, TypeSourceInfo *TInfo) {
+                                 const IdentifierInfo *Id,
+                                 TypeSourceInfo *TInfo) {
   return new (C, DC) TypedefDecl(C, DC, StartLoc, IdLoc, Id, TInfo);
 }
 
@@ -5511,7 +5512,8 @@ TypedefDecl *TypedefDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
 
 TypeAliasDecl *TypeAliasDecl::Create(ASTContext &C, DeclContext *DC,
                                      SourceLocation StartLoc,
-                                     SourceLocation IdLoc, IdentifierInfo *Id,
+                                     SourceLocation IdLoc,
+                                     const IdentifierInfo *Id,
                                      TypeSourceInfo *TInfo) {
   return new (C, DC) TypeAliasDecl(C, DC, StartLoc, IdLoc, Id, TInfo);
 }

diff --git a/clang/lib/AST/DeclObjC.cpp b/clang/lib/AST/DeclObjC.cpp
@@ -66,7 +66,8 @@ void ObjCProtocolList::set(ObjCProtocolDecl* const* InList, unsigned Elts,
 //===----------------------------------------------------------------------===//
 
 ObjCContainerDecl::ObjCContainerDecl(Kind DK, DeclContext *DC,
-                                     IdentifierInfo *Id, SourceLocation nameLoc,
+                                     const IdentifierInfo *Id,
+                                     SourceLocation nameLoc,
                                      SourceLocation atStartLoc)
     : NamedDecl(DK, DC, nameLoc, Id), DeclContext(DK) {
   setAtStartLoc(atStartLoc);
@@ -378,10 +379,8 @@ SourceLocation ObjCInterfaceDecl::getSuperClassLoc() const {
 /// FindPropertyVisibleInPrimaryClass - Finds declaration of the property
 /// with name 'PropertyId' in the primary class; including those in protocols
 /// (direct or indirect) used by the primary class.
-ObjCPropertyDecl *
-ObjCInterfaceDecl::FindPropertyVisibleInPrimaryClass(
-                       IdentifierInfo *PropertyId,
-                       ObjCPropertyQueryKind QueryKind) const {
+ObjCPropertyDecl *ObjCInterfaceDecl::FindPropertyVisibleInPrimaryClass(
+    const IdentifierInfo *PropertyId, ObjCPropertyQueryKind QueryKind) const {
   // FIXME: Should make sure no callers ever do this.
   if (!hasDefinition())
     return nullptr;
@@ -1539,14 +1538,10 @@ void ObjCTypeParamList::gatherDefaultTypeArgs(
 // ObjCInterfaceDecl
 //===----------------------------------------------------------------------===//
 
-ObjCInterfaceDecl *ObjCInterfaceDecl::Create(const ASTContext &C,
-                                             DeclContext *DC,
-                                             SourceLocation atLoc,
-                                             IdentifierInfo *Id,
-                                             ObjCTypeParamList *typeParamList,
-                                             ObjCInterfaceDecl *PrevDecl,
-                                             SourceLocation ClassLoc,
-                                             bool isInternal){
+ObjCInterfaceDecl *ObjCInterfaceDecl::Create(
+    const ASTContext &C, DeclContext *DC, SourceLocation atLoc,
+    const IdentifierInfo *Id, ObjCTypeParamList *typeParamList,
+    ObjCInterfaceDecl *PrevDecl, SourceLocation ClassLoc, bool isInternal) {
   auto *Result = new (C, DC)
       ObjCInterfaceDecl(C, DC, atLoc, Id, typeParamList, ClassLoc, PrevDecl,
                         isInternal);
@@ -1564,12 +1559,10 @@ ObjCInterfaceDecl *ObjCInterfaceDecl::CreateDeserialized(const ASTContext &C,
   return Result;
 }
 
-ObjCInterfaceDecl::ObjCInterfaceDecl(const ASTContext &C, DeclContext *DC,
-                                     SourceLocation AtLoc, IdentifierInfo *Id,
-                                     ObjCTypeParamList *typeParamList,
-                                     SourceLocation CLoc,
-                                     ObjCInterfaceDecl *PrevDecl,
-                                     bool IsInternal)
+ObjCInterfaceDecl::ObjCInterfaceDecl(
+    const ASTContext &C, DeclContext *DC, SourceLocation AtLoc,
+    const IdentifierInfo *Id, ObjCTypeParamList *typeParamList,
+    SourceLocation CLoc, ObjCInterfaceDecl *PrevDecl, bool IsInternal)
     : ObjCContainerDecl(ObjCInterface, DC, Id, CLoc, AtLoc),
       redeclarable_base(C) {
   setPreviousDecl(PrevDecl);
@@ -1751,8 +1744,8 @@ ObjCIvarDecl *ObjCInterfaceDecl::all_declared_ivar_begin() {
 /// categories for this class and returns it. Name of the category is passed
 /// in 'CategoryId'. If category not found, return 0;
 ///
-ObjCCategoryDecl *
-ObjCInterfaceDecl::FindCategoryDeclaration(IdentifierInfo *CategoryId) const {
+ObjCCategoryDecl *ObjCInterfaceDecl::FindCategoryDeclaration(
+    const IdentifierInfo *CategoryId) const {
   // FIXME: Should make sure no callers ever do this.
   if (!hasDefinition())
     return nullptr;
@@ -1838,10 +1831,10 @@ void ObjCIvarDecl::anchor() {}
 
 ObjCIvarDecl *ObjCIvarDecl::Create(ASTContext &C, ObjCContainerDecl *DC,
                                    SourceLocation StartLoc,
-                                   SourceLocation IdLoc, IdentifierInfo *Id,
-                                   QualType T, TypeSourceInfo *TInfo,
-                                   AccessControl ac, Expr *BW,
-                                   bool synthesized) {
+                                   SourceLocation IdLoc,
+                                   const IdentifierInfo *Id, QualType T,
+                                   TypeSourceInfo *TInfo, AccessControl ac,
+                                   Expr *BW, bool synthesized) {
   if (DC) {
     // Ivar's can only appear in interfaces, implementations (via synthesized
     // properties), and class extensions (via direct declaration, or synthesized
@@ -2120,28 +2113,23 @@ void ObjCProtocolDecl::setHasODRHash(bool HasHash) {
 
 void ObjCCategoryDecl::anchor() {}
 
-ObjCCategoryDecl::ObjCCategoryDecl(DeclContext *DC, SourceLocation AtLoc,
-                                   SourceLocation ClassNameLoc,
-                                   SourceLocation CategoryNameLoc,
-                                   IdentifierInfo *Id, ObjCInterfaceDecl *IDecl,
-                                   ObjCTypeParamList *typeParamList,
-                                   SourceLocation IvarLBraceLoc,
-                                   SourceLocation IvarRBraceLoc)
+ObjCCategoryDecl::ObjCCategoryDecl(
+    DeclContext *DC, SourceLocation AtLoc, SourceLocation ClassNameLoc,
+    SourceLocation CategoryNameLoc, const IdentifierInfo *Id,
+    ObjCInterfaceDecl *IDecl, ObjCTypeParamList *typeParamList,
+    SourceLocation IvarLBraceLoc, SourceLocation IvarRBraceLoc)
     : ObjCContainerDecl(ObjCCategory, DC, Id, ClassNameLoc, AtLoc),
       ClassInterface(IDecl), CategoryNameLoc(CategoryNameLoc),
       IvarLBraceLoc(IvarLBraceLoc), IvarRBraceLoc(IvarRBraceLoc) {
   setTypeParamList(typeParamList);
 }
 
-ObjCCategoryDecl *ObjCCategoryDecl::Create(ASTContext &C, DeclContext *DC,
-                                           SourceLocation AtLoc,
-                                           SourceLocation ClassNameLoc,
-                                           SourceLocation CategoryNameLoc,
-                                           IdentifierInfo *Id,
-                                           ObjCInterfaceDecl *IDecl,
-                                           ObjCTypeParamList *typeParamList,
-                                           SourceLocation IvarLBraceLoc,
-                                           SourceLocation IvarRBraceLoc) {
+ObjCCategoryDecl *ObjCCategoryDecl::Create(
+    ASTContext &C, DeclContext *DC, SourceLocation AtLoc,
+    SourceLocation ClassNameLoc, SourceLocation CategoryNameLoc,
+    const IdentifierInfo *Id, ObjCInterfaceDecl *IDecl,
+    ObjCTypeParamList *typeParamList, SourceLocation IvarLBraceLoc,
+    SourceLocation IvarRBraceLoc) {
   auto *CatDecl =
       new (C, DC) ObjCCategoryDecl(DC, AtLoc, ClassNameLoc, CategoryNameLoc, Id,
                                    IDecl, typeParamList, IvarLBraceLoc,
@@ -2190,13 +2178,10 @@ void ObjCCategoryDecl::setTypeParamList(ObjCTypeParamList *TPL) {
 
 void ObjCCategoryImplDecl::anchor() {}
 
-ObjCCategoryImplDecl *
-ObjCCategoryImplDecl::Create(ASTContext &C, DeclContext *DC,
-                             IdentifierInfo *Id,
-                             ObjCInterfaceDecl *ClassInterface,
-                             SourceLocation nameLoc,
-                             SourceLocation atStartLoc,
-                             SourceLocation CategoryNameLoc) {
+ObjCCategoryImplDecl *ObjCCategoryImplDecl::Create(
+    ASTContext &C, DeclContext *DC, const IdentifierInfo *Id,
+    ObjCInterfaceDecl *ClassInterface, SourceLocation nameLoc,
+    SourceLocation atStartLoc, SourceLocation CategoryNameLoc) {
   if (ClassInterface && ClassInterface->hasDefinition())
     ClassInterface = ClassInterface->getDefinition();
   return new (C, DC) ObjCCategoryImplDecl(DC, Id, ClassInterface, nameLoc,
@@ -2365,14 +2350,11 @@ ObjCCompatibleAliasDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
 
 void ObjCPropertyDecl::anchor() {}
 
-ObjCPropertyDecl *ObjCPropertyDecl::Create(ASTContext &C, DeclContext *DC,
-                                           SourceLocation L,
-                                           IdentifierInfo *Id,
-                                           SourceLocation AtLoc,
-                                           SourceLocation LParenLoc,
-                                           QualType T,
-                                           TypeSourceInfo *TSI,
-                                           PropertyControl propControl) {
+ObjCPropertyDecl *
+ObjCPropertyDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
+                         const IdentifierInfo *Id, SourceLocation AtLoc,
+                         SourceLocation LParenLoc, QualType T,
+                         TypeSourceInfo *TSI, PropertyControl propControl) {
   return new (C, DC) ObjCPropertyDecl(DC, L, Id, AtLoc, LParenLoc, T, TSI,
                                       propControl);
 }

diff --git a/clang/lib/AST/DeclPrinter.cpp b/clang/lib/AST/DeclPrinter.cpp
@@ -1218,7 +1218,10 @@ void DeclPrinter::VisitTemplateDecl(const TemplateDecl *D) {
 
   if (const TemplateTemplateParmDecl *TTP =
         dyn_cast<TemplateTemplateParmDecl>(D)) {
-    Out << "class";
+    if (TTP->wasDeclaredWithTypename())
+      Out << "typename";
+    else
+      Out << "class";
 
     if (TTP->isParameterPack())
       Out << " ...";

diff --git a/clang/lib/AST/DeclTemplate.cpp b/clang/lib/AST/DeclTemplate.cpp
@@ -715,7 +715,7 @@ void TemplateTypeParmDecl::setTypeConstraint(
 
 NonTypeTemplateParmDecl::NonTypeTemplateParmDecl(
     DeclContext *DC, SourceLocation StartLoc, SourceLocation IdLoc, unsigned D,
-    unsigned P, IdentifierInfo *Id, QualType T, TypeSourceInfo *TInfo,
+    unsigned P, const IdentifierInfo *Id, QualType T, TypeSourceInfo *TInfo,
     ArrayRef<QualType> ExpandedTypes, ArrayRef<TypeSourceInfo *> ExpandedTInfos)
     : DeclaratorDecl(NonTypeTemplateParm, DC, IdLoc, Id, T, TInfo, StartLoc),
       TemplateParmPosition(D, P), ParameterPack(true),
@@ -730,12 +730,10 @@ NonTypeTemplateParmDecl::NonTypeTemplateParmDecl(
   }
 }
 
-NonTypeTemplateParmDecl *
-NonTypeTemplateParmDecl::Create(const ASTContext &C, DeclContext *DC,
-                                SourceLocation StartLoc, SourceLocation IdLoc,
-                                unsigned D, unsigned P, IdentifierInfo *Id,
-                                QualType T, bool ParameterPack,
-                                TypeSourceInfo *TInfo) {
+NonTypeTemplateParmDecl *NonTypeTemplateParmDecl::Create(
+    const ASTContext &C, DeclContext *DC, SourceLocation StartLoc,
+    SourceLocation IdLoc, unsigned D, unsigned P, const IdentifierInfo *Id,
+    QualType T, bool ParameterPack, TypeSourceInfo *TInfo) {
   AutoType *AT =
       C.getLangOpts().CPlusPlus20 ? T->getContainedAutoType() : nullptr;
   return new (C, DC,
@@ -748,7 +746,7 @@ NonTypeTemplateParmDecl::Create(const ASTContext &C, DeclContext *DC,
 
 NonTypeTemplateParmDecl *NonTypeTemplateParmDecl::Create(
     const ASTContext &C, DeclContext *DC, SourceLocation StartLoc,
-    SourceLocation IdLoc, unsigned D, unsigned P, IdentifierInfo *Id,
+    SourceLocation IdLoc, unsigned D, unsigned P, const IdentifierInfo *Id,
     QualType T, TypeSourceInfo *TInfo, ArrayRef<QualType> ExpandedTypes,
     ArrayRef<TypeSourceInfo *> ExpandedTInfos) {
   AutoType *AT = TInfo->getType()->getContainedAutoType();
@@ -807,10 +805,10 @@ void TemplateTemplateParmDecl::anchor() {}
 
 TemplateTemplateParmDecl::TemplateTemplateParmDecl(
     DeclContext *DC, SourceLocation L, unsigned D, unsigned P,
-    IdentifierInfo *Id, TemplateParameterList *Params,
+    IdentifierInfo *Id, bool Typename, TemplateParameterList *Params,
     ArrayRef<TemplateParameterList *> Expansions)
     : TemplateDecl(TemplateTemplateParm, DC, L, Id, Params),
-      TemplateParmPosition(D, P), ParameterPack(true),
+      TemplateParmPosition(D, P), Typename(Typename), ParameterPack(true),
       ExpandedParameterPack(true), NumExpandedParams(Expansions.size()) {
   if (!Expansions.empty())
     std::uninitialized_copy(Expansions.begin(), Expansions.end(),
@@ -821,26 +819,26 @@ TemplateTemplateParmDecl *
 TemplateTemplateParmDecl::Create(const ASTContext &C, DeclContext *DC,
                                  SourceLocation L, unsigned D, unsigned P,
                                  bool ParameterPack, IdentifierInfo *Id,
-                                 TemplateParameterList *Params) {
+                                 bool Typename, TemplateParameterList *Params) {
   return new (C, DC) TemplateTemplateParmDecl(DC, L, D, P, ParameterPack, Id,
-                                              Params);
+                                              Typename, Params);
 }
 
 TemplateTemplateParmDecl *
 TemplateTemplateParmDecl::Create(const ASTContext &C, DeclContext *DC,
                                  SourceLocation L, unsigned D, unsigned P,
-                                 IdentifierInfo *Id,
+                                 IdentifierInfo *Id, bool Typename,
                                  TemplateParameterList *Params,
                                  ArrayRef<TemplateParameterList *> Expansions) {
   return new (C, DC,
               additionalSizeToAlloc<TemplateParameterList *>(Expansions.size()))
-      TemplateTemplateParmDecl(DC, L, D, P, Id, Params, Expansions);
+      TemplateTemplateParmDecl(DC, L, D, P, Id, Typename, Params, Expansions);
 }
 
 TemplateTemplateParmDecl *
 TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
   return new (C, ID) TemplateTemplateParmDecl(nullptr, SourceLocation(), 0, 0,
-                                              false, nullptr, nullptr);
+                                              false, nullptr, false, nullptr);
 }
 
 TemplateTemplateParmDecl *
@@ -849,7 +847,7 @@ TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, unsigned ID,
   auto *TTP =
       new (C, ID, additionalSizeToAlloc<TemplateParameterList *>(NumExpansions))
           TemplateTemplateParmDecl(nullptr, SourceLocation(), 0, 0, nullptr,
-                                   nullptr, std::nullopt);
+                                   false, nullptr, std::nullopt);
   TTP->NumExpandedParams = NumExpansions;
   return TTP;
 }
@@ -1471,7 +1469,7 @@ createMakeIntegerSeqParameterList(const ASTContext &C, DeclContext *DC) {
   // template <typename T, ...Ints> class IntSeq
   auto *TemplateTemplateParm = TemplateTemplateParmDecl::Create(
       C, DC, SourceLocation(), /*Depth=*/0, /*Position=*/0,
-      /*ParameterPack=*/false, /*Id=*/nullptr, TPL);
+      /*ParameterPack=*/false, /*Id=*/nullptr, /*Typename=*/false, TPL);
   TemplateTemplateParm->setImplicit(true);
 
   // typename T

diff --git a/clang/lib/AST/Interp/ByteCodeExprGen.cpp b/clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -2778,26 +2778,34 @@ bool ByteCodeExprGen<Emitter>::visitVarDecl(const VarDecl *VD) {
   std::optional<PrimType> VarT = classify(VD->getType());
 
   if (Context::shouldBeGloballyIndexed(VD)) {
-    // We've already seen and initialized this global.
-    if (P.getGlobal(VD))
-      return true;
-
-    std::optional<unsigned> GlobalIndex = P.createGlobal(VD, Init);
-
-    if (!GlobalIndex)
-      return false;
-
-    if (Init) {
+    auto initGlobal = [&](unsigned GlobalIndex) -> bool {
+      assert(Init);
       DeclScope<Emitter> LocalScope(this, VD);
 
       if (VarT) {
         if (!this->visit(Init))
           return false;
-        return this->emitInitGlobal(*VarT, *GlobalIndex, VD);
+        return this->emitInitGlobal(*VarT, GlobalIndex, VD);
       }
-      return this->visitGlobalInitializer(Init, *GlobalIndex);
+      return this->visitGlobalInitializer(Init, GlobalIndex);
+    };
+
+    // We've already seen and initialized this global.
+    if (std::optional<unsigned> GlobalIndex = P.getGlobal(VD)) {
+      if (P.getPtrGlobal(*GlobalIndex).isInitialized())
+        return true;
+
+      // The previous attempt at initialization might've been unsuccessful,
+      // so let's try this one.
+      return Init && initGlobal(*GlobalIndex);
     }
-    return true;
+
+    std::optional<unsigned> GlobalIndex = P.createGlobal(VD, Init);
+
+    if (!GlobalIndex)
+      return false;
+
+    return !Init || initGlobal(*GlobalIndex);
   } else {
     VariableScope<Emitter> LocalScope(this);
     if (VarT) {

diff --git a/clang/lib/AST/Interp/FunctionPointer.h b/clang/lib/AST/Interp/FunctionPointer.h
@@ -20,31 +20,45 @@ namespace interp {
 class FunctionPointer final {
 private:
   const Function *Func;
+  bool Valid;
 
 public:
-  // FIXME: We might want to track the fact that the Function pointer
-  // has been created from an integer and is most likely garbage anyway.
-  FunctionPointer(uintptr_t IntVal = 0, const Descriptor *Desc = nullptr)
-      : Func(reinterpret_cast<const Function *>(IntVal)) {}
+  FunctionPointer(const Function *Func) : Func(Func), Valid(true) {
+    assert(Func);
+  }
 
-  FunctionPointer(const Function *Func) : Func(Func) { assert(Func); }
+  FunctionPointer(uintptr_t IntVal = 0, const Descriptor *Desc = nullptr)
+      : Func(reinterpret_cast<const Function *>(IntVal)), Valid(false) {}
 
   const Function *getFunction() const { return Func; }
   bool isZero() const { return !Func; }
+  bool isWeak() const {
+    if (!Func || !Valid)
+      return false;
+
+    return Func->getDecl()->isWeak();
+  }
 
   APValue toAPValue() const {
     if (!Func)
       return APValue(static_cast<Expr *>(nullptr), CharUnits::Zero(), {},
                      /*OnePastTheEnd=*/false, /*IsNull=*/true);
 
+    if (!Valid)
+      return APValue(static_cast<Expr *>(nullptr),
+                     CharUnits::fromQuantity(getIntegerRepresentation()), {},
+                     /*OnePastTheEnd=*/false, /*IsNull=*/false);
+
     return APValue(Func->getDecl(), CharUnits::Zero(), {},
                    /*OnePastTheEnd=*/false, /*IsNull=*/false);
   }
 
   void print(llvm::raw_ostream &OS) const {
     OS << "FnPtr(";
-    if (Func)
+    if (Func && Valid)
       OS << Func->getName();
+    else if (Func)
+      OS << reinterpret_cast<uintptr_t>(Func);
     else
       OS << "nullptr";
     OS << ")";

diff --git a/clang/lib/AST/Interp/Interp.cpp b/clang/lib/AST/Interp/Interp.cpp
@@ -56,22 +56,65 @@ static bool Jf(InterpState &S, CodePtr &PC, int32_t Offset) {
   return true;
 }
 
+static void diagnoseMissingInitializer(InterpState &S, CodePtr OpPC,
+                                       const ValueDecl *VD) {
+  const SourceInfo &E = S.Current->getSource(OpPC);
+  S.FFDiag(E, diag::note_constexpr_var_init_unknown, 1) << VD;
+  S.Note(VD->getLocation(), diag::note_declared_at) << VD->getSourceRange();
+}
+
+static void diagnoseNonConstVariable(InterpState &S, CodePtr OpPC,
+                                     const ValueDecl *VD);
+static bool diagnoseUnknownDecl(InterpState &S, CodePtr OpPC,
+                                const ValueDecl *D) {
+  const SourceInfo &E = S.Current->getSource(OpPC);
+
+  if (isa<ParmVarDecl>(D)) {
+    if (S.getLangOpts().CPlusPlus11) {
+      S.FFDiag(E, diag::note_constexpr_function_param_value_unknown) << D;
+      S.Note(D->getLocation(), diag::note_declared_at) << D->getSourceRange();
+    } else {
+      S.FFDiag(E);
+    }
+  } else if (const auto *VD = dyn_cast<VarDecl>(D)) {
+    if (!VD->getType().isConstQualified()) {
+      diagnoseNonConstVariable(S, OpPC, VD);
+      return false;
+    }
+
+    // const, but no initializer.
+    if (!VD->getAnyInitializer()) {
+      diagnoseMissingInitializer(S, OpPC, VD);
+      return false;
+    }
+  }
+  return false;
+}
+
 static void diagnoseNonConstVariable(InterpState &S, CodePtr OpPC,
                                      const ValueDecl *VD) {
   if (!S.getLangOpts().CPlusPlus)
     return;
 
   const SourceInfo &Loc = S.Current->getSource(OpPC);
+  if (const auto *VarD = dyn_cast<VarDecl>(VD);
+      VarD && VarD->getType().isConstQualified() &&
+      !VarD->getAnyInitializer()) {
+    diagnoseMissingInitializer(S, OpPC, VD);
+    return;
+  }
 
-  if (VD->getType()->isIntegralOrEnumerationType())
+  if (VD->getType()->isIntegralOrEnumerationType()) {
     S.FFDiag(Loc, diag::note_constexpr_ltor_non_const_int, 1) << VD;
-  else
-    S.FFDiag(Loc,
-             S.getLangOpts().CPlusPlus11
-                 ? diag::note_constexpr_ltor_non_constexpr
-                 : diag::note_constexpr_ltor_non_integral,
-             1)
-        << VD << VD->getType();
+    S.Note(VD->getLocation(), diag::note_declared_at);
+    return;
+  }
+
+  S.FFDiag(Loc,
+           S.getLangOpts().CPlusPlus11 ? diag::note_constexpr_ltor_non_constexpr
+                                       : diag::note_constexpr_ltor_non_integral,
+           1)
+      << VD << VD->getType();
   S.Note(VD->getLocation(), diag::note_declared_at);
 }
 
@@ -202,6 +245,9 @@ bool CheckExtern(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
   if (!Ptr.isExtern())
     return true;
 
+  if (Ptr.isInitialized())
+    return true;
+
   if (!S.checkingPotentialConstantExpression() && S.getLangOpts().CPlusPlus) {
     const auto *VD = Ptr.getDeclDesc()->asValueDecl();
     diagnoseNonConstVariable(S, OpPC, VD);
@@ -369,9 +415,15 @@ bool CheckInitialized(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
   if (const auto *VD = Ptr.getDeclDesc()->asVarDecl();
       VD && VD->hasGlobalStorage()) {
     const SourceInfo &Loc = S.Current->getSource(OpPC);
-    S.FFDiag(Loc, diag::note_constexpr_var_init_non_constant, 1) << VD;
-    S.Note(VD->getLocation(), diag::note_declared_at);
+    if (VD->getAnyInitializer()) {
+      S.FFDiag(Loc, diag::note_constexpr_var_init_non_constant, 1) << VD;
+      S.Note(VD->getLocation(), diag::note_declared_at);
+    } else {
+      diagnoseMissingInitializer(S, OpPC, VD);
+    }
+    return false;
   }
+
   if (!S.checkingPotentialConstantExpression()) {
     S.FFDiag(S.Current->getSource(OpPC), diag::note_constexpr_access_uninit)
         << AK << /*uninitialized=*/true << S.Current->getRange(OpPC);
@@ -598,33 +650,6 @@ bool CheckFloatResult(InterpState &S, CodePtr OpPC, const Floating &Result,
   return true;
 }
 
-static bool diagnoseUnknownDecl(InterpState &S, CodePtr OpPC,
-                                const ValueDecl *D) {
-  const SourceInfo &E = S.Current->getSource(OpPC);
-
-  if (isa<ParmVarDecl>(D)) {
-    if (S.getLangOpts().CPlusPlus11) {
-      S.FFDiag(E, diag::note_constexpr_function_param_value_unknown) << D;
-      S.Note(D->getLocation(), diag::note_declared_at) << D->getSourceRange();
-    } else {
-      S.FFDiag(E);
-    }
-  } else if (const auto *VD = dyn_cast<VarDecl>(D)) {
-    if (!VD->getType().isConstQualified()) {
-      diagnoseNonConstVariable(S, OpPC, VD);
-      return false;
-    }
-
-    // const, but no initializer.
-    if (!VD->getAnyInitializer()) {
-      S.FFDiag(E, diag::note_constexpr_var_init_unknown, 1) << VD;
-      S.Note(VD->getLocation(), diag::note_declared_at) << VD->getSourceRange();
-      return false;
-    }
-  }
-  return false;
-}
-
 /// We aleady know the given DeclRefExpr is invalid for some reason,
 /// now figure out why and print appropriate diagnostics.
 bool CheckDeclRef(InterpState &S, CodePtr OpPC, const DeclRefExpr *DR) {

diff --git a/clang/lib/AST/Interp/Interp.h b/clang/lib/AST/Interp/Interp.h
@@ -758,7 +758,7 @@ inline bool CmpHelperEQ<FunctionPointer>(InterpState &S, CodePtr OpPC,
 
   // We cannot compare against weak declarations at compile time.
   for (const auto &FP : {LHS, RHS}) {
-    if (!FP.isZero() && FP.getFunction()->getDecl()->isWeak()) {
+    if (FP.isWeak()) {
       const SourceInfo &Loc = S.Current->getSource(OpPC);
       S.FFDiag(Loc, diag::note_constexpr_pointer_weak_comparison)
           << FP.toDiagnosticString(S.getCtx());

diff --git a/clang/lib/AST/Interp/InterpState.h b/clang/lib/AST/Interp/InterpState.h
@@ -89,7 +89,11 @@ class InterpState final : public State, public SourceMapper {
 
   /// Delegates source mapping to the mapper.
   SourceInfo getSource(const Function *F, CodePtr PC) const override {
-    return M ? M->getSource(F, PC) : F->getSource(PC);
+    if (M)
+      return M->getSource(F, PC);
+
+    assert(F && "Function cannot be null");
+    return F->getSource(PC);
   }
 
   Context &getContext() const { return Ctx; }

diff --git a/clang/lib/AST/Interp/Program.cpp b/clang/lib/AST/Interp/Program.cpp
@@ -177,7 +177,7 @@ std::optional<unsigned> Program::createGlobal(const ValueDecl *VD,
   bool IsStatic, IsExtern;
   if (const auto *Var = dyn_cast<VarDecl>(VD)) {
     IsStatic = Context::shouldBeGloballyIndexed(VD);
-    IsExtern = !Var->getAnyInitializer();
+    IsExtern = Var->hasExternalStorage();
   } else if (isa<UnnamedGlobalConstantDecl, MSGuidDecl>(VD)) {
     IsStatic = true;
     IsExtern = false;

diff --git a/clang/lib/AST/JSONNodeDumper.cpp b/clang/lib/AST/JSONNodeDumper.cpp
@@ -1576,6 +1576,14 @@ void JSONNodeDumper::VisitMaterializeTemporaryExpr(
   attributeOnlyIfTrue("boundToLValueRef", MTE->isBoundToLvalueReference());
 }
 
+void JSONNodeDumper::VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *Node) {
+  attributeOnlyIfTrue("hasRewrittenInit", Node->hasRewrittenInit());
+}
+
+void JSONNodeDumper::VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *Node) {
+  attributeOnlyIfTrue("hasRewrittenInit", Node->hasRewrittenInit());
+}
+
 void JSONNodeDumper::VisitCXXDependentScopeMemberExpr(
     const CXXDependentScopeMemberExpr *DSME) {
   JOS.attribute("isArrow", DSME->isArrow());

diff --git a/clang/lib/AST/NSAPI.cpp b/clang/lib/AST/NSAPI.cpp
@@ -56,10 +56,8 @@ Selector NSAPI::getNSStringSelector(NSStringMethodKind MK) const {
                                        &Ctx.Idents.get("initWithUTF8String"));
       break;
     case NSStr_stringWithCStringEncoding: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("stringWithCString"),
-        &Ctx.Idents.get("encoding")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("stringWithCString"),
+                                           &Ctx.Idents.get("encoding")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
@@ -93,10 +91,8 @@ Selector NSAPI::getNSArraySelector(NSArrayMethodKind MK) const {
       Sel = Ctx.Selectors.getUnarySelector(&Ctx.Idents.get("arrayWithObjects"));
       break;
     case NSArr_arrayWithObjectsCount: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("arrayWithObjects"),
-        &Ctx.Idents.get("count")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("arrayWithObjects"),
+                                           &Ctx.Idents.get("count")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
@@ -110,29 +106,24 @@ Selector NSAPI::getNSArraySelector(NSArrayMethodKind MK) const {
       Sel = Ctx.Selectors.getUnarySelector(&Ctx.Idents.get("objectAtIndex"));
       break;
     case NSMutableArr_replaceObjectAtIndex: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("replaceObjectAtIndex"),
-        &Ctx.Idents.get("withObject")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("replaceObjectAtIndex"),
+          &Ctx.Idents.get("withObject")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSMutableArr_addObject:
       Sel = Ctx.Selectors.getUnarySelector(&Ctx.Idents.get("addObject"));
       break;
     case NSMutableArr_insertObjectAtIndex: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("insertObject"),
-        &Ctx.Idents.get("atIndex")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("insertObject"),
+                                           &Ctx.Idents.get("atIndex")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSMutableArr_setObjectAtIndexedSubscript: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("setObject"),
-        &Ctx.Idents.get("atIndexedSubscript")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("setObject"), &Ctx.Idents.get("atIndexedSubscript")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
@@ -167,27 +158,21 @@ Selector NSAPI::getNSDictionarySelector(
                                    &Ctx.Idents.get("dictionaryWithDictionary"));
       break;
     case NSDict_dictionaryWithObjectForKey: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("dictionaryWithObject"),
-        &Ctx.Idents.get("forKey")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("dictionaryWithObject"), &Ctx.Idents.get("forKey")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSDict_dictionaryWithObjectsForKeys: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("dictionaryWithObjects"),
-        &Ctx.Idents.get("forKeys")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("dictionaryWithObjects"), &Ctx.Idents.get("forKeys")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSDict_dictionaryWithObjectsForKeysCount: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("dictionaryWithObjects"),
-        &Ctx.Idents.get("forKeys"),
-        &Ctx.Idents.get("count")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("dictionaryWithObjects"), &Ctx.Idents.get("forKeys"),
+          &Ctx.Idents.get("count")};
       Sel = Ctx.Selectors.getSelector(3, KeyIdents);
       break;
     }
@@ -204,37 +189,29 @@ Selector NSAPI::getNSDictionarySelector(
                                      &Ctx.Idents.get("initWithObjectsAndKeys"));
       break;
     case NSDict_initWithObjectsForKeys: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("initWithObjects"),
-        &Ctx.Idents.get("forKeys")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("initWithObjects"),
+                                           &Ctx.Idents.get("forKeys")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSDict_objectForKey:
       Sel = Ctx.Selectors.getUnarySelector(&Ctx.Idents.get("objectForKey"));
       break;
     case NSMutableDict_setObjectForKey: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("setObject"),
-        &Ctx.Idents.get("forKey")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("setObject"),
+                                           &Ctx.Idents.get("forKey")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSMutableDict_setObjectForKeyedSubscript: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("setObject"),
-        &Ctx.Idents.get("forKeyedSubscript")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("setObject"), &Ctx.Idents.get("forKeyedSubscript")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSMutableDict_setValueForKey: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("setValue"),
-        &Ctx.Idents.get("forKey")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("setValue"),
+                                           &Ctx.Idents.get("forKey")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
@@ -264,34 +241,27 @@ Selector NSAPI::getNSSetSelector(NSSetMethodKind MK) const {
       Sel = Ctx.Selectors.getUnarySelector(&Ctx.Idents.get("addObject"));
       break;
     case NSOrderedSet_insertObjectAtIndex: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("insertObject"),
-        &Ctx.Idents.get("atIndex")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("insertObject"),
+                                           &Ctx.Idents.get("atIndex")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSOrderedSet_setObjectAtIndex: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("setObject"),
-        &Ctx.Idents.get("atIndex")
-      };
+      const IdentifierInfo *KeyIdents[] = {&Ctx.Idents.get("setObject"),
+                                           &Ctx.Idents.get("atIndex")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSOrderedSet_setObjectAtIndexedSubscript: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("setObject"),
-        &Ctx.Idents.get("atIndexedSubscript")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("setObject"), &Ctx.Idents.get("atIndexedSubscript")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
     case NSOrderedSet_replaceObjectAtIndexWithObject: {
-      IdentifierInfo *KeyIdents[] = {
-        &Ctx.Idents.get("replaceObjectAtIndex"),
-        &Ctx.Idents.get("withObject")
-      };
+      const IdentifierInfo *KeyIdents[] = {
+          &Ctx.Idents.get("replaceObjectAtIndex"),
+          &Ctx.Idents.get("withObject")};
       Sel = Ctx.Selectors.getSelector(2, KeyIdents);
       break;
     }
@@ -606,7 +576,7 @@ bool NSAPI::isObjCEnumerator(const Expr *E,
 Selector NSAPI::getOrInitSelector(ArrayRef<StringRef> Ids,
                                   Selector &Sel) const {
   if (Sel.isNull()) {
-    SmallVector<IdentifierInfo *, 4> Idents;
+    SmallVector<const IdentifierInfo *, 4> Idents;
     for (ArrayRef<StringRef>::const_iterator
            I = Ids.begin(), E = Ids.end(); I != E; ++I)
       Idents.push_back(&Ctx.Idents.get(*I));
@@ -617,7 +587,7 @@ Selector NSAPI::getOrInitSelector(ArrayRef<StringRef> Ids,
 
 Selector NSAPI::getOrInitNullarySelector(StringRef Id, Selector &Sel) const {
   if (Sel.isNull()) {
-    IdentifierInfo *Ident = &Ctx.Idents.get(Id);
+    const IdentifierInfo *Ident = &Ctx.Idents.get(Id);
     Sel = Ctx.Selectors.getSelector(0, &Ident);
   }
   return Sel;

diff --git a/clang/lib/AST/NestedNameSpecifier.cpp b/clang/lib/AST/NestedNameSpecifier.cpp
@@ -55,16 +55,16 @@ NestedNameSpecifier::FindOrInsert(const ASTContext &Context,
   return NNS;
 }
 
-NestedNameSpecifier *
-NestedNameSpecifier::Create(const ASTContext &Context,
-                            NestedNameSpecifier *Prefix, IdentifierInfo *II) {
+NestedNameSpecifier *NestedNameSpecifier::Create(const ASTContext &Context,
+                                                 NestedNameSpecifier *Prefix,
+                                                 const IdentifierInfo *II) {
   assert(II && "Identifier cannot be NULL");
   assert((!Prefix || Prefix->isDependent()) && "Prefix must be dependent");
 
   NestedNameSpecifier Mockup;
   Mockup.Prefix.setPointer(Prefix);
   Mockup.Prefix.setInt(StoredIdentifier);
-  Mockup.Specifier = II;
+  Mockup.Specifier = const_cast<IdentifierInfo *>(II);
   return FindOrInsert(Context, Mockup);
 }
 
@@ -87,7 +87,7 @@ NestedNameSpecifier::Create(const ASTContext &Context,
 NestedNameSpecifier *
 NestedNameSpecifier::Create(const ASTContext &Context,
                             NestedNameSpecifier *Prefix,
-                            NamespaceAliasDecl *Alias) {
+                            const NamespaceAliasDecl *Alias) {
   assert(Alias && "Namespace alias cannot be NULL");
   assert((!Prefix ||
           (Prefix->getAsType() == nullptr &&
@@ -96,7 +96,7 @@ NestedNameSpecifier::Create(const ASTContext &Context,
   NestedNameSpecifier Mockup;
   Mockup.Prefix.setPointer(Prefix);
   Mockup.Prefix.setInt(StoredDecl);
-  Mockup.Specifier = Alias;
+  Mockup.Specifier = const_cast<NamespaceAliasDecl *>(Alias);
   return FindOrInsert(Context, Mockup);
 }
 
@@ -112,13 +112,13 @@ NestedNameSpecifier::Create(const ASTContext &Context,
   return FindOrInsert(Context, Mockup);
 }
 
-NestedNameSpecifier *
-NestedNameSpecifier::Create(const ASTContext &Context, IdentifierInfo *II) {
+NestedNameSpecifier *NestedNameSpecifier::Create(const ASTContext &Context,
+                                                 const IdentifierInfo *II) {
   assert(II && "Identifier cannot be NULL");
   NestedNameSpecifier Mockup;
   Mockup.Prefix.setPointer(nullptr);
   Mockup.Prefix.setInt(StoredIdentifier);
-  Mockup.Specifier = II;
+  Mockup.Specifier = const_cast<IdentifierInfo *>(II);
   return FindOrInsert(Context, Mockup);
 }
 

diff --git a/clang/lib/AST/OpenACCClause.cpp b/clang/lib/AST/OpenACCClause.cpp
@@ -13,6 +13,7 @@
 
 #include "clang/AST/OpenACCClause.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/Expr.h"
 
 using namespace clang;
 
@@ -27,10 +28,48 @@ OpenACCDefaultClause *OpenACCDefaultClause::Create(const ASTContext &C,
   return new (Mem) OpenACCDefaultClause(K, BeginLoc, LParenLoc, EndLoc);
 }
 
+OpenACCIfClause *OpenACCIfClause::Create(const ASTContext &C,
+                                         SourceLocation BeginLoc,
+                                         SourceLocation LParenLoc,
+                                         Expr *ConditionExpr,
+                                         SourceLocation EndLoc) {
+  void *Mem = C.Allocate(sizeof(OpenACCIfClause), alignof(OpenACCIfClause));
+  return new (Mem) OpenACCIfClause(BeginLoc, LParenLoc, ConditionExpr, EndLoc);
+}
+
+OpenACCIfClause::OpenACCIfClause(SourceLocation BeginLoc,
+                                 SourceLocation LParenLoc, Expr *ConditionExpr,
+                                 SourceLocation EndLoc)
+    : OpenACCClauseWithCondition(OpenACCClauseKind::If, BeginLoc, LParenLoc,
+                                 ConditionExpr, EndLoc) {
+  assert(ConditionExpr && "if clause requires condition expr");
+  assert((ConditionExpr->isInstantiationDependent() ||
+          ConditionExpr->getType()->isScalarType()) &&
+         "Condition expression type not scalar/dependent");
+}
+
+OpenACCClause::child_range OpenACCClause::children() {
+  switch (getClauseKind()) {
+  default:
+    assert(false && "Clause children function not implemented");
+    break;
+#define VISIT_CLAUSE(CLAUSE_NAME)                                              \
+  case OpenACCClauseKind::CLAUSE_NAME:                                         \
+    return cast<OpenACC##CLAUSE_NAME##Clause>(this)->children();
+
+#include "clang/Basic/OpenACCClauses.def"
+  }
+  return child_range(child_iterator(), child_iterator());
+}
+
 //===----------------------------------------------------------------------===//
 //  OpenACC clauses printing methods
 //===----------------------------------------------------------------------===//
 void OpenACCClausePrinter::VisitOpenACCDefaultClause(
     const OpenACCDefaultClause &C) {
   OS << "default(" << C.getDefaultClauseKind() << ")";
 }
+
+void OpenACCClausePrinter::VisitOpenACCIfClause(const OpenACCIfClause &C) {
+  OS << "if(" << C.getConditionExpr() << ")";
+}
diff --git a/clang/lib/AST/SelectorLocationsKind.cpp b/clang/lib/AST/SelectorLocationsKind.cpp
@@ -26,15 +26,15 @@ static SourceLocation getStandardSelLoc(unsigned Index,
     assert(Index == 0);
     if (EndLoc.isInvalid())
       return SourceLocation();
-    IdentifierInfo *II = Sel.getIdentifierInfoForSlot(0);
+    const IdentifierInfo *II = Sel.getIdentifierInfoForSlot(0);
     unsigned Len = II ? II->getLength() : 0;
     return EndLoc.getLocWithOffset(-Len);
   }
 
   assert(Index < NumSelArgs);
   if (ArgLoc.isInvalid())
     return SourceLocation();
-  IdentifierInfo *II = Sel.getIdentifierInfoForSlot(Index);
+  const IdentifierInfo *II = Sel.getIdentifierInfoForSlot(Index);
   unsigned Len = /* selector id */ (II ? II->getLength() : 0) + /* ':' */ 1;
   if (WithArgSpace)
     ++Len;

diff --git a/clang/lib/AST/StmtPrinter.cpp b/clang/lib/AST/StmtPrinter.cpp
@@ -1447,7 +1447,7 @@ void StmtPrinter::VisitOffsetOfExpr(OffsetOfExpr *Node) {
       continue;
 
     // Field or identifier node.
-    IdentifierInfo *Id = ON.getFieldName();
+    const IdentifierInfo *Id = ON.getFieldName();
     if (!Id)
       continue;
 
@@ -2348,7 +2348,7 @@ void StmtPrinter::VisitCXXPseudoDestructorExpr(CXXPseudoDestructorExpr *E) {
     E->getQualifier()->print(OS, Policy);
   OS << "~";
 
-  if (IdentifierInfo *II = E->getDestroyedTypeIdentifier())
+  if (const IdentifierInfo *II = E->getDestroyedTypeIdentifier())
     OS << II->getName();
   else
     E->getDestroyedType().print(OS, Policy);

diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
@@ -61,7 +61,7 @@ namespace {
     virtual void VisitName(DeclarationName Name, bool TreatAsDecl = false) = 0;
 
     /// Visit identifiers that are not in Decl's or Type's.
-    virtual void VisitIdentifierInfo(IdentifierInfo *II) = 0;
+    virtual void VisitIdentifierInfo(const IdentifierInfo *II) = 0;
 
     /// Visit a nested-name-specifier that occurs within an expression
     /// or statement.
@@ -163,7 +163,7 @@ namespace {
       ID.AddPointer(Name.getAsOpaquePtr());
     }
 
-    void VisitIdentifierInfo(IdentifierInfo *II) override {
+    void VisitIdentifierInfo(const IdentifierInfo *II) override {
       ID.AddPointer(II);
     }
 
@@ -211,7 +211,7 @@ namespace {
       }
       Hash.AddDeclarationName(Name, TreatAsDecl);
     }
-    void VisitIdentifierInfo(IdentifierInfo *II) override {
+    void VisitIdentifierInfo(const IdentifierInfo *II) override {
       ID.AddBoolean(II);
       if (II) {
         Hash.AddIdentifierInfo(II);
@@ -2445,9 +2445,10 @@ void StmtProfiler::VisitTemplateArgument(const TemplateArgument &Arg) {
 namespace {
 class OpenACCClauseProfiler
     : public OpenACCClauseVisitor<OpenACCClauseProfiler> {
+  StmtProfiler &Profiler;
 
 public:
-  OpenACCClauseProfiler() = default;
+  OpenACCClauseProfiler(StmtProfiler &P) : Profiler(P) {}
 
   void VisitOpenACCClauseList(ArrayRef<const OpenACCClause *> Clauses) {
     for (const OpenACCClause *Clause : Clauses) {
@@ -2456,20 +2457,32 @@ class OpenACCClauseProfiler
       Visit(Clause);
     }
   }
-  void VisitOpenACCDefaultClause(const OpenACCDefaultClause &Clause);
+
+#define VISIT_CLAUSE(CLAUSE_NAME)                                              \
+  void VisitOpenACC##CLAUSE_NAME##Clause(                                      \
+      const OpenACC##CLAUSE_NAME##Clause &Clause);
+
+#include "clang/Basic/OpenACCClauses.def"
 };
 
 /// Nothing to do here, there are no sub-statements.
 void OpenACCClauseProfiler::VisitOpenACCDefaultClause(
     const OpenACCDefaultClause &Clause) {}
+
+void OpenACCClauseProfiler::VisitOpenACCIfClause(
+    const OpenACCIfClause &Clause) {
+  assert(Clause.hasConditionExpr() &&
+         "if clause requires a valid condition expr");
+  Profiler.VisitStmt(Clause.getConditionExpr());
+}
 } // namespace
 
 void StmtProfiler::VisitOpenACCComputeConstruct(
     const OpenACCComputeConstruct *S) {
   // VisitStmt handles children, so the AssociatedStmt is handled.
   VisitStmt(S);
 
-  OpenACCClauseProfiler P;
+  OpenACCClauseProfiler P{*this};
   P.VisitOpenACCClauseList(S->clauses());
 }
 

diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
@@ -397,6 +397,11 @@ void TextNodeDumper::Visit(const OpenACCClause *C) {
     case OpenACCClauseKind::Default:
       OS << '(' << cast<OpenACCDefaultClause>(C)->getDefaultClauseKind() << ')';
       break;
+    case OpenACCClauseKind::If:
+      // The condition expression will be printed as a part of the 'children',
+      // but print 'clause' here so it is clear what is happening from the dump.
+      OS << " clause";
+      break;
     default:
       // Nothing to do here.
       break;
@@ -1450,23 +1455,13 @@ void TextNodeDumper::VisitExpressionTraitExpr(const ExpressionTraitExpr *Node) {
 }
 
 void TextNodeDumper::VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *Node) {
-  if (Node->hasRewrittenInit()) {
+  if (Node->hasRewrittenInit())
     OS << " has rewritten init";
-    AddChild([=] {
-      ColorScope Color(OS, ShowColors, StmtColor);
-      Visit(Node->getExpr());
-    });
-  }
 }
 
 void TextNodeDumper::VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *Node) {
-  if (Node->hasRewrittenInit()) {
+  if (Node->hasRewrittenInit())
     OS << " has rewritten init";
-    AddChild([=] {
-      ColorScope Color(OS, ShowColors, StmtColor);
-      Visit(Node->getExpr());
-    });
-  }
 }
 
 void TextNodeDumper::VisitMaterializeTemporaryExpr(

diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
diff --git a/clang/lib/Analysis/FlowSensitive/Transfer.cpp b/clang/lib/Analysis/FlowSensitive/Transfer.cpp
@@ -460,25 +460,41 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
     // So make sure we have a value if we didn't propagate one above.
     if (S->isPRValue() && S->getType()->isRecordType()) {
       if (Env.getValue(*S) == nullptr) {
-        Value *Val = Env.createValue(S->getType());
-        // We're guaranteed to always be able to create a value for record
-        // types.
-        assert(Val != nullptr);
-        Env.setValue(*S, *Val);
+        auto &Loc = Env.getResultObjectLocation(*S);
+        Env.initializeFieldsWithValues(Loc);
+        refreshRecordValue(Loc, Env);
       }
     }
   }
 
   void VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *S) {
     const Expr *InitExpr = S->getExpr();
     assert(InitExpr != nullptr);
+
+    // If this is a prvalue of record type, the handler for `*InitExpr` (if one
+    // exists) will initialize the result object; there is no value to propgate
+    // here.
+    if (S->getType()->isRecordType() && S->isPRValue())
+      return;
+
     propagateValueOrStorageLocation(*InitExpr, *S, Env);
   }
 
   void VisitCXXConstructExpr(const CXXConstructExpr *S) {
     const CXXConstructorDecl *ConstructorDecl = S->getConstructor();
     assert(ConstructorDecl != nullptr);
 
+    // `CXXConstructExpr` can have array type if default-initializing an array
+    // of records. We don't handle this specifically beyond potentially inlining
+    // the call.
+    if (!S->getType()->isRecordType()) {
+      transferInlineCall(S, ConstructorDecl);
+      return;
+    }
+
+    RecordStorageLocation &Loc = Env.getResultObjectLocation(*S);
+    Env.setValue(*S, refreshRecordValue(Loc, Env));
+
     if (ConstructorDecl->isCopyOrMoveConstructor()) {
       // It is permissible for a copy/move constructor to have additional
       // parameters as long as they have default arguments defined for them.
@@ -491,24 +507,14 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
       if (ArgLoc == nullptr)
         return;
 
-      if (S->isElidable()) {
-        if (Value *Val = Env.getValue(*ArgLoc))
-          Env.setValue(*S, *Val);
-      } else {
-        auto &Val = *cast<RecordValue>(Env.createValue(S->getType()));
-        Env.setValue(*S, Val);
-        copyRecord(*ArgLoc, Val.getLoc(), Env);
-      }
+      // Even if the copy/move constructor call is elidable, we choose to copy
+      // the record in all cases (which isn't wrong, just potentially not
+      // optimal).
+      copyRecord(*ArgLoc, Loc, Env);
       return;
     }
 
-    // `CXXConstructExpr` can have array type if default-initializing an array
-    // of records, and we currently can't create values for arrays. So check if
-    // we've got a record type.
-    if (S->getType()->isRecordType()) {
-      auto &InitialVal = *cast<RecordValue>(Env.createValue(S->getType()));
-      Env.setValue(*S, InitialVal);
-    }
+    Env.initializeFieldsWithValues(Loc, S->getType());
 
     transferInlineCall(S, ConstructorDecl);
   }
@@ -551,19 +557,15 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
       if (S->isGLValue()) {
         Env.setStorageLocation(*S, *LocDst);
       } else if (S->getType()->isRecordType()) {
-        // Make sure that we have a `RecordValue` for this expression so that
-        // `Environment::getResultObjectLocation()` is able to return a location
-        // for it.
-        if (Env.getValue(*S) == nullptr)
-          refreshRecordValue(*S, Env);
+        // Assume that the assignment returns the assigned value.
+        copyRecord(*LocDst, Env.getResultObjectLocation(*S), Env);
       }
 
       return;
     }
 
-    // CXXOperatorCallExpr can be prvalues. Call `VisitCallExpr`() to create
-    // a `RecordValue` for them so that `Environment::getResultObjectLocation()`
-    // can return a value.
+    // `CXXOperatorCallExpr` can be a prvalue. Call `VisitCallExpr`() to
+    // initialize the prvalue's fields with values.
     VisitCallExpr(S);
   }
 
@@ -580,11 +582,6 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
     }
   }
 
-  void VisitCXXTemporaryObjectExpr(const CXXTemporaryObjectExpr *S) {
-    if (Value *Val = Env.createValue(S->getType()))
-      Env.setValue(*S, *Val);
-  }
-
   void VisitCallExpr(const CallExpr *S) {
     // Of clang's builtins, only `__builtin_expect` is handled explicitly, since
     // others (like trap, debugtrap, and unreachable) are handled by CFG
@@ -612,13 +609,14 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
     } else if (const FunctionDecl *F = S->getDirectCallee()) {
       transferInlineCall(S, F);
 
-      // If this call produces a prvalue of record type, make sure that we have
-      // a `RecordValue` for it. This is required so that
-      // `Environment::getResultObjectLocation()` is able to return a location
-      // for this `CallExpr`.
+      // If this call produces a prvalue of record type, initialize its fields
+      // with values.
       if (S->getType()->isRecordType() && S->isPRValue())
-        if (Env.getValue(*S) == nullptr)
-          refreshRecordValue(*S, Env);
+        if (Env.getValue(*S) == nullptr) {
+          RecordStorageLocation &Loc = Env.getResultObjectLocation(*S);
+          Env.initializeFieldsWithValues(Loc);
+          Env.setValue(*S, refreshRecordValue(Loc, Env));
+        }
     }
   }
 
@@ -666,8 +664,10 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
     // `getLogicOperatorSubExprValue()`.
     if (S->isGLValue())
       Env.setStorageLocation(*S, Env.createObject(S->getType()));
-    else if (Value *Val = Env.createValue(S->getType()))
-      Env.setValue(*S, *Val);
+    else if (!S->getType()->isRecordType()) {
+      if (Value *Val = Env.createValue(S->getType()))
+        Env.setValue(*S, *Val);
+    }
   }
 
   void VisitInitListExpr(const InitListExpr *S) {
@@ -688,71 +688,51 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
       return;
     }
 
-    llvm::DenseMap<const ValueDecl *, StorageLocation *> FieldLocs;
-    RecordInitListHelper InitListHelper(S);
+    RecordStorageLocation &Loc = Env.getResultObjectLocation(*S);
+    Env.setValue(*S, refreshRecordValue(Loc, Env));
 
-    for (auto [Base, Init] : InitListHelper.base_inits()) {
-      assert(Base->getType().getCanonicalType() ==
-             Init->getType().getCanonicalType());
-      auto *BaseVal = Env.get<RecordValue>(*Init);
-      if (!BaseVal)
-        BaseVal = cast<RecordValue>(Env.createValue(Init->getType()));
-      // Take ownership of the fields of the `RecordValue` for the base class
-      // and incorporate them into the "flattened" set of fields for the
-      // derived class.
-      auto Children = BaseVal->getLoc().children();
-      FieldLocs.insert(Children.begin(), Children.end());
-    }
+    // Initialization of base classes and fields of record type happens when we
+    // visit the nested `CXXConstructExpr` or `InitListExpr` for that base class
+    // or field. We therefore only need to deal with fields of non-record type
+    // here.
 
-    for (auto [Field, Init] : InitListHelper.field_inits()) {
-      assert(
-          // The types are same, or
-          Field->getType().getCanonicalType().getUnqualifiedType() ==
-              Init->getType().getCanonicalType().getUnqualifiedType() ||
-          // The field's type is T&, and initializer is T
-          (Field->getType()->isReferenceType() &&
-           Field->getType().getCanonicalType()->getPointeeType() ==
-               Init->getType().getCanonicalType()));
-      auto& Loc = Env.createObject(Field->getType(), Init);
-      FieldLocs.insert({Field, &Loc});
-    }
+    RecordInitListHelper InitListHelper(S);
 
-    // In the case of a union, we don't in general have initializers for all
-    // of the fields. Create storage locations for the remaining fields (but
-    // don't associate them with values).
-    if (Type->isUnionType()) {
-      for (const FieldDecl *Field :
-           Env.getDataflowAnalysisContext().getModeledFields(Type)) {
-        if (auto [it, inserted] = FieldLocs.insert({Field, nullptr}); inserted)
-          it->second = &Env.createStorageLocation(Field->getType());
+    for (auto [Field, Init] : InitListHelper.field_inits()) {
+      if (Field->getType()->isRecordType())
+        continue;
+      if (Field->getType()->isReferenceType()) {
+        assert(Field->getType().getCanonicalType()->getPointeeType() ==
+               Init->getType().getCanonicalType());
+        Loc.setChild(*Field, &Env.createObject(Field->getType(), Init));
+        continue;
       }
+      assert(Field->getType().getCanonicalType().getUnqualifiedType() ==
+             Init->getType().getCanonicalType().getUnqualifiedType());
+      StorageLocation *FieldLoc = Loc.getChild(*Field);
+      // Locations for non-reference fields must always be non-null.
+      assert(FieldLoc != nullptr);
+      Value *Val = Env.getValue(*Init);
+      if (Val == nullptr && isa<ImplicitValueInitExpr>(Init) &&
+          Init->getType()->isPointerType())
+        Val =
+            &Env.getOrCreateNullPointerValue(Init->getType()->getPointeeType());
+      if (Val == nullptr)
+        Val = Env.createValue(Field->getType());
+      if (Val != nullptr)
+        Env.setValue(*FieldLoc, *Val);
     }
 
-    // Check that we satisfy the invariant that a `RecordStorageLoation`
-    // contains exactly the set of modeled fields for that type.
-    // `ModeledFields` includes fields from all the bases, but only the
-    // modeled ones. However, if a class type is initialized with an
-    // `InitListExpr`, all fields in the class, including those from base
-    // classes, are included in the set of modeled fields. The code above
-    // should therefore populate exactly the modeled fields.
-    assert(containsSameFields(
-        Env.getDataflowAnalysisContext().getModeledFields(Type), FieldLocs));
-
-    RecordStorageLocation::SyntheticFieldMap SyntheticFieldLocs;
-    for (const auto &Entry :
-         Env.getDataflowAnalysisContext().getSyntheticFields(Type)) {
-      SyntheticFieldLocs.insert(
-          {Entry.getKey(), &Env.createObject(Entry.getValue())});
+    for (const auto &[FieldName, FieldLoc] : Loc.synthetic_fields()) {
+      QualType FieldType = FieldLoc->getType();
+      if (FieldType->isRecordType()) {
+        Env.initializeFieldsWithValues(*cast<RecordStorageLocation>(FieldLoc));
+      } else {
+        if (Value *Val = Env.createValue(FieldType))
+          Env.setValue(*FieldLoc, *Val);
+      }
     }
 
-    auto &Loc = Env.getDataflowAnalysisContext().createRecordStorageLocation(
-        Type, std::move(FieldLocs), std::move(SyntheticFieldLocs));
-    RecordValue &RecordVal = Env.create<RecordValue>(Loc);
-
-    Env.setValue(Loc, RecordVal);
-
-    Env.setValue(*S, RecordVal);
-
     // FIXME: Implement array initialization.
   }
 

diff --git a/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp b/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
@@ -369,17 +369,10 @@ builtinTransferInitializer(const CFGInitializer &Elt,
     ParentLoc->setChild(*Member, InitExprLoc);
   } else if (auto *InitExprVal = Env.getValue(*InitExpr)) {
     assert(MemberLoc != nullptr);
-    if (Member->getType()->isRecordType()) {
-      auto *InitValStruct = cast<RecordValue>(InitExprVal);
-      // FIXME: Rather than performing a copy here, we should really be
-      // initializing the field in place. This would require us to propagate the
-      // storage location of the field to the AST node that creates the
-      // `RecordValue`.
-      copyRecord(InitValStruct->getLoc(),
-                 *cast<RecordStorageLocation>(MemberLoc), Env);
-    } else {
+    // Record-type initializers construct themselves directly into the result
+    // object, so there is no need to handle them here.
+    if (!Member->getType()->isRecordType())
       Env.setValue(*MemberLoc, *InitExprVal);
-    }
   }
 }
 

diff --git a/clang/lib/Analysis/ObjCNoReturn.cpp b/clang/lib/Analysis/ObjCNoReturn.cpp
@@ -17,7 +17,8 @@
 
 using namespace clang;
 
-static bool isSubclass(const ObjCInterfaceDecl *Class, IdentifierInfo *II) {
+static bool isSubclass(const ObjCInterfaceDecl *Class,
+                       const IdentifierInfo *II) {
   if (!Class)
     return false;
   if (Class->getIdentifier() == II)
@@ -30,7 +31,7 @@ ObjCNoReturn::ObjCNoReturn(ASTContext &C)
     NSExceptionII(&C.Idents.get("NSException"))
 {
   // Generate selectors.
-  SmallVector<IdentifierInfo*, 3> II;
+  SmallVector<const IdentifierInfo *, 3> II;
 
   // raise:format:
   II.push_back(&C.Idents.get("raise"));

diff --git a/clang/lib/Basic/IdentifierTable.cpp b/clang/lib/Basic/IdentifierTable.cpp
@@ -541,7 +541,8 @@ unsigned Selector::getNumArgs() const {
   return SI->getNumArgs();
 }
 
-IdentifierInfo *Selector::getIdentifierInfoForSlot(unsigned argIndex) const {
+const IdentifierInfo *
+Selector::getIdentifierInfoForSlot(unsigned argIndex) const {
   if (getIdentifierInfoFlag() < MultiArg) {
     assert(argIndex == 0 && "illegal keyword index");
     return getAsIdentifierInfo();
@@ -553,7 +554,7 @@ IdentifierInfo *Selector::getIdentifierInfoForSlot(unsigned argIndex) const {
 }
 
 StringRef Selector::getNameForSlot(unsigned int argIndex) const {
-  IdentifierInfo *II = getIdentifierInfoForSlot(argIndex);
+  const IdentifierInfo *II = getIdentifierInfoForSlot(argIndex);
   return II ? II->getName() : StringRef();
 }
 
@@ -574,7 +575,7 @@ std::string Selector::getAsString() const {
     return "<null selector>";
 
   if (getIdentifierInfoFlag() < MultiArg) {
-    IdentifierInfo *II = getAsIdentifierInfo();
+    const IdentifierInfo *II = getAsIdentifierInfo();
 
     if (getNumArgs() == 0) {
       assert(II && "If the number of arguments is 0 then II is guaranteed to "
@@ -608,7 +609,7 @@ static bool startsWithWord(StringRef name, StringRef word) {
 }
 
 ObjCMethodFamily Selector::getMethodFamilyImpl(Selector sel) {
-  IdentifierInfo *first = sel.getIdentifierInfoForSlot(0);
+  const IdentifierInfo *first = sel.getIdentifierInfoForSlot(0);
   if (!first) return OMF_None;
 
   StringRef name = first->getName();
@@ -655,7 +656,7 @@ ObjCMethodFamily Selector::getMethodFamilyImpl(Selector sel) {
 }
 
 ObjCInstanceTypeFamily Selector::getInstTypeMethodFamily(Selector sel) {
-  IdentifierInfo *first = sel.getIdentifierInfoForSlot(0);
+  const IdentifierInfo *first = sel.getIdentifierInfoForSlot(0);
   if (!first) return OIT_None;
 
   StringRef name = first->getName();
@@ -683,7 +684,7 @@ ObjCInstanceTypeFamily Selector::getInstTypeMethodFamily(Selector sel) {
 }
 
 ObjCStringFormatFamily Selector::getStringFormatFamilyImpl(Selector sel) {
-  IdentifierInfo *first = sel.getIdentifierInfoForSlot(0);
+  const IdentifierInfo *first = sel.getIdentifierInfoForSlot(0);
   if (!first) return SFF_None;
 
   StringRef name = first->getName();
@@ -750,7 +751,8 @@ size_t SelectorTable::getTotalMemory() const {
   return SelTabImpl.Allocator.getTotalMemory();
 }
 
-Selector SelectorTable::getSelector(unsigned nKeys, IdentifierInfo **IIV) {
+Selector SelectorTable::getSelector(unsigned nKeys,
+                                    const IdentifierInfo **IIV) {
   if (nKeys < 2)
     return Selector(IIV[0], nKeys);
 

diff --git a/clang/lib/Basic/Targets/X86.cpp b/clang/lib/Basic/Targets/X86.cpp
@@ -954,6 +954,9 @@ void X86TargetInfo::getTargetDefines(const LangOptions &Opts,
     Builder.defineMacro("__CCMP__");
   if (HasCF)
     Builder.defineMacro("__CF__");
+  // Condition here is aligned with the feature set of mapxf in Options.td
+  if (HasEGPR && HasPush2Pop2 && HasPPX && HasNDD)
+    Builder.defineMacro("__APX_F__");
 
   // Each case falls through to the previous one here.
   switch (SSELevel) {

diff --git a/clang/lib/CIR/CMakeLists.txt b/clang/lib/CIR/CMakeLists.txt
diff --git a/clang/lib/CMakeLists.txt b/clang/lib/CMakeLists.txt
@@ -31,3 +31,7 @@ if(CLANG_INCLUDE_TESTS)
 endif()
 add_subdirectory(Interpreter)
 add_subdirectory(Support)
+
+if(CLANG_ENABLE_CIR)
+  add_subdirectory(CIR)
+endif()
diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
@@ -1806,7 +1806,11 @@ void AtomicInfo::EmitAtomicUpdateOp(
                                              /*NumReservedValues=*/2);
   PHI->addIncoming(OldVal, CurBB);
   Address NewAtomicAddr = CreateTempAlloca();
-  Address NewAtomicIntAddr = castToAtomicIntPointer(NewAtomicAddr);
+  Address NewAtomicIntAddr =
+      shouldCastToInt(NewAtomicAddr.getElementType(), /*CmpXchg=*/true)
+          ? castToAtomicIntPointer(NewAtomicAddr)
+          : NewAtomicAddr;
+
   if ((LVal.isBitField() && BFI.Size != ValueSizeInBits) ||
       requiresMemSetZero(getAtomicAddress().getElementType())) {
     CGF.Builder.CreateStore(PHI, NewAtomicIntAddr);

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
@@ -1447,7 +1447,7 @@ llvm::Function *CodeGenFunction::GenerateBlockFunction(
     selfTy = getContext().getPointerType(getContext().getAddrSpaceQualType(
         getContext().VoidTy, LangAS::opencl_generic));
 
-  IdentifierInfo *II = &CGM.getContext().Idents.get(".block_descriptor");
+  const IdentifierInfo *II = &CGM.getContext().Idents.get(".block_descriptor");
 
   ImplicitParamDecl SelfDecl(getContext(), const_cast<BlockDecl *>(blockDecl),
                              SourceLocation(), II, selfTy,
@@ -2791,7 +2791,7 @@ static void configureBlocksRuntimeObject(CodeGenModule &CGM,
   auto *GV = cast<llvm::GlobalValue>(C->stripPointerCasts());
 
   if (CGM.getTarget().getTriple().isOSBinFormatCOFF()) {
-    IdentifierInfo &II = CGM.getContext().Idents.get(C->getName());
+    const IdentifierInfo &II = CGM.getContext().Idents.get(C->getName());
     TranslationUnitDecl *TUDecl = CGM.getContext().getTranslationUnitDecl();
     DeclContext *DC = TranslationUnitDecl::castToDeclContext(TUDecl);
 

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -18312,9 +18312,16 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
     Value *Op0 = EmitScalarExpr(E->getArg(0));
     if (!E->getArg(0)->getType()->hasFloatingRepresentation())
       llvm_unreachable("rcp operand must have a float representation");
-    return Builder.CreateIntrinsic(
-        /*ReturnType=*/Op0->getType(), Intrinsic::dx_rcp,
-        ArrayRef<Value *>{Op0}, nullptr, "dx.rcp");
+    llvm::Type *Ty = Op0->getType();
+    llvm::Type *EltTy = Ty->getScalarType();
+    Constant *One =
+        Ty->isVectorTy()
+            ? ConstantVector::getSplat(
+                  ElementCount::getFixed(
+                      dyn_cast<FixedVectorType>(Ty)->getNumElements()),
+                  ConstantFP::get(EltTy, 1.0))
+            : ConstantFP::get(EltTy, 1.0);
+    return Builder.CreateFDiv(One, Op0, "hlsl.rcp");
   }
   case Builtin::BI__builtin_hlsl_elementwise_rsqrt: {
     Value *Op0 = EmitScalarExpr(E->getArg(0));

diff --git a/clang/lib/CodeGen/CGCUDANV.cpp b/clang/lib/CodeGen/CGCUDANV.cpp
@@ -361,7 +361,7 @@ void CGNVCUDARuntime::emitDeviceStubBodyNew(CodeGenFunction &CGF,
       KernelLaunchAPI = KernelLaunchAPI + "_ptsz";
   }
   auto LaunchKernelName = addPrefixToName(KernelLaunchAPI);
-  IdentifierInfo &cudaLaunchKernelII =
+  const IdentifierInfo &cudaLaunchKernelII =
       CGM.getContext().Idents.get(LaunchKernelName);
   FunctionDecl *cudaLaunchKernelFD = nullptr;
   for (auto *Result : DC->lookup(&cudaLaunchKernelII)) {

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
@@ -4124,7 +4124,8 @@ static bool isProvablyNull(llvm::Value *addr) {
 }
 
 static bool isProvablyNonNull(Address Addr, CodeGenFunction &CGF) {
-  return llvm::isKnownNonZero(Addr.getBasePointer(), CGF.CGM.getDataLayout());
+  return llvm::isKnownNonZero(Addr.getBasePointer(), /*Depth=*/0,
+                              CGF.CGM.getDataLayout());
 }
 
 /// Emit the actual writing-back of a writeback.

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
@@ -1384,7 +1384,7 @@ void CodeGenFunction::EmitAndRegisterVariableArrayDimensions(
   // For each dimension stores its QualType and corresponding
   // size-expression Value.
   SmallVector<CodeGenFunction::VlaSizePair, 4> Dimensions;
-  SmallVector<IdentifierInfo *, 4> VLAExprNames;
+  SmallVector<const IdentifierInfo *, 4> VLAExprNames;
 
   // Break down the array into individual dimensions.
   QualType Type1D = D.getType();
@@ -1421,7 +1421,7 @@ void CodeGenFunction::EmitAndRegisterVariableArrayDimensions(
       MD = llvm::ConstantAsMetadata::get(C);
     else {
       // Create an artificial VarDecl to generate debug info for.
-      IdentifierInfo *NameIdent = VLAExprNames[NameIdx++];
+      const IdentifierInfo *NameIdent = VLAExprNames[NameIdx++];
       auto QT = getContext().getIntTypeForBitwidth(
           SizeTy->getScalarSizeInBits(), false);
       auto *ArtificialDecl = VarDecl::Create(