4 files changed, 43 insertions, 2 deletions
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index 3bf79bba8fd..624a1118b73 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -1760,6 +1760,11 @@ protected:
   unsigned IsCopyDeductionCandidate : 1;
 
 private:
+
+  /// Store the ODRHash after first calculation.
+  unsigned HasODRHash : 1;
+  unsigned ODRHash;
+
   /// \brief End part of this FunctionDecl's source range.
   ///
   /// We could compute the full range in getSourceRange(). However, when we're
@@ -1842,8 +1847,9 @@ protected:
         IsExplicitlyDefaulted(false), HasImplicitReturnZero(false),
         IsLateTemplateParsed(false), IsConstexpr(isConstexprSpecified),
         InstantiationIsPending(false), UsesSEHTry(false), HasSkippedBody(false),
-        WillHaveBody(false), IsCopyDeductionCandidate(false),
-        EndRangeLoc(NameInfo.getEndLoc()), DNLoc(NameInfo.getInfo()) {}
+        WillHaveBody(false), IsCopyDeductionCandidate(false), HasODRHash(false),
+        ODRHash(0), EndRangeLoc(NameInfo.getEndLoc()),
+        DNLoc(NameInfo.getInfo()) {}
 
   using redeclarable_base = Redeclarable<FunctionDecl>;
 
@@ -2443,6 +2449,10 @@ public:
   /// returns 0.
   unsigned getMemoryFunctionKind() const;
 
+  /// \brief Returns ODRHash of the function.  This value is calculated and
+  /// stored on first call, then the stored value returned on the other calls.
+  unsigned getODRHash();
+
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
   static bool classofKind(Kind K) {
diff --git a/clang/include/clang/AST/ODRHash.h b/clang/include/clang/AST/ODRHash.h
index e4cc12d3589..ed648bb8afb 100644
--- a/clang/include/clang/AST/ODRHash.h
+++ b/clang/include/clang/AST/ODRHash.h
@@ -53,6 +53,10 @@ public:
   // more information than the AddDecl class.
   void AddCXXRecordDecl(const CXXRecordDecl *Record);
 
+  // Use this for ODR checking functions between modules.  This method compares
+  // more information than the AddDecl class.
+  void AddFunctionDecl(const FunctionDecl *Function);
+
   // Process SubDecls of the main Decl.  This method calls the DeclVisitor
   // while AddDecl does not.
   void AddSubDecl(const Decl *D);
diff --git a/clang/include/clang/Basic/DiagnosticSerializationKinds.td b/clang/include/clang/Basic/DiagnosticSerializationKinds.td
index 3949bc2146f..250b49f2cac 100644
--- a/clang/include/clang/Basic/DiagnosticSerializationKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSerializationKinds.td
@@ -270,6 +270,29 @@ def note_module_odr_violation_mismatch_decl_diff : Note<"but in '%0' found "
   "friend function %2|"
   "}1">;
 
+def err_module_odr_violation_function : Error<
+  "%q0 has different definitions in different modules; "
+  "%select{definition in module '%2'|defined here}1 "
+  "first difference is "
+  "%select{"
+  "return type is %4|"
+  "%ordinal4 parameter with name %5|"
+  "%ordinal4 parameter with type %5%select{| decayed from %7}6|"
+  "%ordinal4 parameter with%select{out|}5 a default argument|"
+  "%ordinal4 parameter with a default argument|"
+  "function body"
+  "}3">;
+
+def note_module_odr_violation_function : Note<"but in '%0' found "
+  "%select{"
+  "different return type %2|"
+  "%ordinal2 parameter with name %3|"
+  "%ordinal2 parameter with type %3%select{| decayed from %5}4|"
+  "%ordinal2 parameter with%select{out|}3 a default argument|"
+  "%ordinal2 parameter with a different default argument|"
+  "a different body"
+  "}1">;
+
 def err_module_odr_violation_mismatch_decl_unknown : Error<
   "%q0 %select{with definition in module '%2'|defined here}1 has different "
   "definitions in different modules; first difference is this "
diff --git a/clang/include/clang/Serialization/ASTReader.h b/clang/include/clang/Serialization/ASTReader.h
index 7b71fee95de..37920fc143e 100644
--- a/clang/include/clang/Serialization/ASTReader.h
+++ b/clang/include/clang/Serialization/ASTReader.h
@@ -1092,6 +1092,10 @@ private:
   llvm::SmallDenseMap<CXXRecordDecl *, llvm::SmallVector<DataPointers, 2>, 2>
       PendingOdrMergeFailures;
 
+  /// \brief Function definitions in which we found an ODR violation.
+  llvm::SmallDenseMap<FunctionDecl *, llvm::SmallVector<FunctionDecl *, 2>, 2>
+      PendingFunctionOdrMergeFailures;
+
   /// \brief DeclContexts in which we have diagnosed an ODR violation.
   llvm::SmallPtrSet<DeclContext*, 2> DiagnosedOdrMergeFailures;