diff --git a/include/llvm/IR/Mangler.h b/include/llvm/IR/Mangler.h
index 9229dd8446c..07f4feda7e8 100644
--- a/include/llvm/IR/Mangler.h
+++ b/include/llvm/IR/Mangler.h
@@ -39,11 +39,11 @@ private:
   /// they are mangled.  This keeps track of the number we give to anonymous
   /// ones.
   ///
-  DenseMap<const GlobalValue*, unsigned> AnonGlobalIDs;
+  mutable DenseMap<const GlobalValue*, unsigned> AnonGlobalIDs;
 
   /// NextAnonGlobalID - This simple counter is used to unique value names.
   ///
-  unsigned NextAnonGlobalID;
+  mutable unsigned NextAnonGlobalID;
 
 public:
   Mangler(const DataLayout *DL) : DL(DL), NextAnonGlobalID(1) {}
@@ -51,15 +51,16 @@ public:
   /// Print the appropriate prefix and the specified global variable's name.
   /// If the global variable doesn't have a name, this fills in a unique name
   /// for the global.
-  void getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV);
-  void getNameWithPrefix(SmallVectorImpl<char> &OutName, const GlobalValue *GV);
+  void getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV) const;
+  void getNameWithPrefix(SmallVectorImpl<char> &OutName,
+                         const GlobalValue *GV) const;
 
   /// Print the appropriate prefix and the specified name as the global variable
   /// name. GVName must not be empty.
   void getNameWithPrefix(raw_ostream &OS, const Twine &GVName,
-                         ManglerPrefixTy PrefixTy = Mangler::Default);
+                         ManglerPrefixTy PrefixTy = Mangler::Default) const;
   void getNameWithPrefix(SmallVectorImpl<char> &OutName, const Twine &GVName,
-                         ManglerPrefixTy PrefixTy = Mangler::Default);
+                         ManglerPrefixTy PrefixTy = Mangler::Default) const;
 };
 
 } // End llvm namespace
diff --git a/lib/IR/Mangler.cpp b/lib/IR/Mangler.cpp
index bc1362dc80b..9c18e6f3001 100644
--- a/lib/IR/Mangler.cpp
+++ b/lib/IR/Mangler.cpp
@@ -44,13 +44,14 @@ static void getNameWithPrefixx(raw_ostream &OS, const Twine &GVName,
   OS << Name;
 }
 
-void Mangler::getNameWithPrefix(raw_ostream &OS,
-                                const Twine &GVName, ManglerPrefixTy PrefixTy) {
+void Mangler::getNameWithPrefix(raw_ostream &OS, const Twine &GVName,
+                                ManglerPrefixTy PrefixTy) const {
   return getNameWithPrefixx(OS, GVName, PrefixTy, *DL, false);
 }
 
 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
-                                const Twine &GVName, ManglerPrefixTy PrefixTy) {
+                                const Twine &GVName,
+                                ManglerPrefixTy PrefixTy) const {
   raw_svector_ostream OS(OutName);
   return getNameWithPrefix(OS, GVName, PrefixTy);
 }
@@ -75,7 +76,7 @@ static void AddFastCallStdCallSuffix(raw_ostream &OS, const Function *F,
   OS << '@' << ArgWords;
 }
 
-void Mangler::getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV) {
+void Mangler::getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV) const {
   ManglerPrefixTy PrefixTy = Mangler::Default;
   if (GV->hasPrivateLinkage())
     PrefixTy = Mangler::Private;
@@ -133,7 +134,7 @@ void Mangler::getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV) {
 }
 
 void Mangler::getNameWithPrefix(SmallVectorImpl<char> &OutName,
-                                const GlobalValue *GV) {
+                                const GlobalValue *GV) const {
   raw_svector_ostream OS(OutName);
   getNameWithPrefix(OS, GV);
 }