[Modules] Handle tag types and complain about bad merges in C/Objective-C mode

clang/include/clang/AST/Decl.h

@@ -3716,6 +3716,7 @@ class RecordDecl : public TagDecl {
   // to save some space. Use the provided accessors to access it.
 public:
   friend class DeclContext;
+  friend class ASTDeclReader;
   /// Enum that represents the different ways arguments are passed to and
   /// returned from function calls. This takes into account the target-specific
   /// and version-specific rules along with the rules determined by the
@@ -3960,9 +3961,19 @@ class RecordDecl : public TagDecl {
   /// nullptr is returned if no named data member exists.
   const FieldDecl *findFirstNamedDataMember() const;
 
+  /// Get precomputed ODRHash or add a new one.
+  unsigned getODRHash();
+
 private:
   /// Deserialize just the fields.
   void LoadFieldsFromExternalStorage() const;
+
+  /// True if a valid hash is stored in ODRHash.
+  bool hasODRHash() const { return RecordDeclBits.HasODRHash; }
+  void setHasODRHash(bool Hash = true) { RecordDeclBits.HasODRHash = Hash; }
+
+  /// Store the ODR hash for this decl.
+  unsigned ODRHash;
 };
 
 class FileScopeAsmDecl : public Decl {

clang/include/clang/AST/DeclBase.h

@@ -1452,10 +1452,13 @@ class DeclContext {
 
     /// Represents the way this type is passed to a function.
     uint64_t ArgPassingRestrictions : 2;
+
+    /// True if a valid hash is stored in ODRHash.
+    uint64_t HasODRHash : 1;
   };
 
   /// Number of non-inherited bits in RecordDeclBitfields.
-  enum { NumRecordDeclBits = 14 };
+  enum { NumRecordDeclBits = 15 };
 
   /// Stores the bits used by OMPDeclareReductionDecl.
   /// If modified NumOMPDeclareReductionDeclBits and the accessor

clang/include/clang/AST/ODRHash.h

@@ -55,6 +55,10 @@ class ODRHash {
   // more information than the AddDecl class.
   void AddCXXRecordDecl(const CXXRecordDecl *Record);
 
+  // Use this for ODR checking records in C/Objective-C between modules. This
+  // method compares more information than the AddDecl class.
+  void AddRecordDecl(const RecordDecl *Record);
+
   // Use this for ODR checking functions between modules.  This method compares
   // more information than the AddDecl class.  SkipBody will process the
   // hash as if the function has no body.

clang/include/clang/Serialization/ASTReader.h

@@ -1100,6 +1100,10 @@ class ASTReader
   llvm::SmallDenseMap<EnumDecl *, llvm::SmallVector<EnumDecl *, 2>, 2>
       PendingEnumOdrMergeFailures;
 
+  /// C/ObjC definitions in which the structural equivalence check fails
+  llvm::SmallDenseMap<RecordDecl *, llvm::SmallVector<RecordDecl *, 2>, 2>
+      PendingRecordOdrMergeFailures;
+
   /// DeclContexts in which we have diagnosed an ODR violation.
   llvm::SmallPtrSet<DeclContext*, 2> DiagnosedOdrMergeFailures;
 

clang/lib/AST/Decl.cpp

@@ -4360,6 +4360,8 @@ RecordDecl::RecordDecl(Kind DK, TagKind TK, const ASTContext &C,
   setHasNonTrivialToPrimitiveCopyCUnion(false);
   setParamDestroyedInCallee(false);
   setArgPassingRestrictions(APK_CanPassInRegs);
+  setHasODRHash(false);
+  ODRHash = 0;
 }
 
 RecordDecl *RecordDecl::Create(const ASTContext &C, TagKind TK, DeclContext *DC,
@@ -4507,6 +4509,19 @@ const FieldDecl *RecordDecl::findFirstNamedDataMember() const {
   return nullptr;
 }
 
+unsigned RecordDecl::getODRHash() {
+  if (hasODRHash())
+    return ODRHash;
+
+  // Only calculate hash on first call of getODRHash per record.
+  class ODRHash Hash;
+  Hash.AddRecordDecl(this);
+  setHasODRHash();
+  ODRHash = Hash.CalculateHash();
+
+  return ODRHash;
+}
+
 //===----------------------------------------------------------------------===//
 // BlockDecl Implementation
 //===----------------------------------------------------------------------===//

clang/lib/AST/DeclCXX.cpp

@@ -484,7 +484,7 @@ unsigned CXXRecordDecl::getODRHash() const {
     return DefinitionData->ODRHash;
 
   // Only calculate hash on first call of getODRHash per record.
-  ODRHash Hash;
+  class ODRHash Hash;
   Hash.AddCXXRecordDecl(getDefinition());
   DefinitionData->HasODRHash = true;
   DefinitionData->ODRHash = Hash.CalculateHash();

clang/lib/AST/ODRHash.cpp

@@ -464,6 +464,21 @@ void ODRHash::AddSubDecl(const Decl *D) {
   ODRDeclVisitor(ID, *this).Visit(D);
 }
 
+void ODRHash::AddRecordDecl(const RecordDecl *Record) {
+  AddDecl(Record);
+
+  // Filter out sub-Decls which will not be processed in order to get an
+  // accurate count of Decl's.
+  llvm::SmallVector<const Decl *, 16> Decls;
+  for (Decl *SubDecl : Record->decls())
+    if (isWhitelistedDecl(SubDecl, Record))
+      Decls.push_back(SubDecl);
+
+  ID.AddInteger(Decls.size());
+  for (auto SubDecl : Decls)
+    AddSubDecl(SubDecl);
+}
+
 void ODRHash::AddCXXRecordDecl(const CXXRecordDecl *Record) {
   assert(Record && Record->hasDefinition() &&
          "Expected non-null record to be a definition.");