4 files changed, 11 insertions, 3 deletions
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index fdfd6c07059..19ffe1a720b 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -71,8 +71,8 @@ CXXRecordDecl::DefinitionData::DefinitionData(CXXRecordDecl *D)
       ImplicitCopyAssignmentHasConstParam(true),
       HasDeclaredCopyConstructorWithConstParam(false),
       HasDeclaredCopyAssignmentWithConstParam(false), IsLambda(false),
-      IsParsingBaseSpecifiers(false), NumBases(0), NumVBases(0), Bases(),
-      VBases(), Definition(D), FirstFriend() {}
+      IsParsingBaseSpecifiers(false), ODRHash(0), NumBases(0), NumVBases(0),
+      Bases(), VBases(), Definition(D), FirstFriend() {}
 
 CXXBaseSpecifier *CXXRecordDecl::DefinitionData::getBasesSlowCase() const {
   return Bases.get(Definition->getASTContext().getExternalSource());
@@ -371,6 +371,8 @@ CXXRecordDecl::setBases(CXXBaseSpecifier const * const *Bases,
   data().IsParsingBaseSpecifiers = false;
 }
 
+void CXXRecordDecl::computeODRHash() {}
+
 void CXXRecordDecl::addedClassSubobject(CXXRecordDecl *Subobj) {
   // C++11 [class.copy]p11:
   //   A defaulted copy/move constructor for a class X is defined as
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 77d74983028..e96860a294e 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -13771,8 +13771,11 @@ void Sema::ActOnTagFinishDefinition(Scope *S, Decl *TagD,
       RD->completeDefinition();
   }
 
-  if (isa<CXXRecordDecl>(Tag))
+  if (auto *RD = dyn_cast<CXXRecordDecl>(Tag)) {
     FieldCollector->FinishClass();
+    if (Context.getLangOpts().Modules)
+      RD->computeODRHash();
+  }
 
   // Exit this scope of this tag's definition.
   PopDeclContext();
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index add3b3e828e..0f43e9fcf64 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1528,6 +1528,7 @@ void ASTDeclReader::ReadCXXDefinitionData(
   Data.ImplicitCopyAssignmentHasConstParam = Record.readInt();
   Data.HasDeclaredCopyConstructorWithConstParam = Record.readInt();
   Data.HasDeclaredCopyAssignmentWithConstParam = Record.readInt();
+  Data.ODRHash = Record.readInt();
 
   Data.NumBases = Record.readInt();
   if (Data.NumBases)
@@ -1658,6 +1659,7 @@ void ASTDeclReader::MergeDefinitionData(
   OR_FIELD(HasDeclaredCopyConstructorWithConstParam)
   OR_FIELD(HasDeclaredCopyAssignmentWithConstParam)
   MATCH_FIELD(IsLambda)
+  MATCH_FIELD(ODRHash)
 #undef OR_FIELD
 #undef MATCH_FIELD
 
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 5dee86c1419..5fe693ba8e1 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -5707,6 +5707,7 @@ void ASTRecordWriter::AddCXXDefinitionData(const CXXRecordDecl *D) {
   Record->push_back(Data.ImplicitCopyAssignmentHasConstParam);
   Record->push_back(Data.HasDeclaredCopyConstructorWithConstParam);
   Record->push_back(Data.HasDeclaredCopyAssignmentWithConstParam);
+  Record->push_back(Data.ODRHash);
   // IsLambda bit is already saved.
 
   Record->push_back(Data.NumBases);