diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -265,7 +265,8 @@
   BackRefVec NameBackReferences;
 
   typedef llvm::DenseMap<const void *, unsigned> ArgBackRefMap;
-  ArgBackRefMap TypeBackReferences;
+  ArgBackRefMap FunArgBackReferences;
+  ArgBackRefMap TemplateArgBackReferences;
 
   typedef std::set<std::pair<int, bool>> PassObjectSizeArgsSet;
   PassObjectSizeArgsSet PassObjectSizeArgs;
@@ -343,7 +344,7 @@
                                   const TemplateArgumentList &TemplateArgs);
   void mangleObjCMethodName(const ObjCMethodDecl *MD);
 
-  void mangleArgumentType(QualType T, SourceRange Range);
+  void mangleFunctionArgumentType(QualType T, SourceRange Range);
   void manglePassObjectSizeArg(const PassObjectSizeAttr *POSA);
 
   bool isArtificialTagType(QualType T) const;
@@ -793,7 +794,7 @@
     // the X<Y> part is aliased. However, if you need to mangle
     //   void foo(A::X<A::Y>, A::X<B::Y>),
     // the A::X<> part is not aliased.
-    // That said, from the mangler's perspective we have a structure like this:
+    // That is, from the mangler's perspective we have a structure like this:
     //   namespace[s] -> type[ -> template-parameters]
     // but from the Clang perspective we have
     //   type [ -> template-parameters]
@@ -803,12 +804,30 @@
     // the mangled type name as a key to check the mangling of different types
     // for aliasing.
 
-    llvm::SmallString<64> TemplateMangling;
-    llvm::raw_svector_ostream Stream(TemplateMangling);
-    MicrosoftCXXNameMangler Extra(Context, Stream);
-    Extra.mangleTemplateInstantiationName(TD, *TemplateArgs);
-
-    mangleSourceName(TemplateMangling);
+    // It's important to key cache reads off ND, not TD -- the same TD can
+    // be used with different TemplateArgs, but ND uniquely identifies
+    // TD / TemplateArg pairs.
+    ArgBackRefMap::iterator Found = TemplateArgBackReferences.find(ND);
+    if (Found == TemplateArgBackReferences.end()) {
+      // Mangle full template name into temporary buffer.
+      llvm::SmallString<64> TemplateMangling;
+      llvm::raw_svector_ostream Stream(TemplateMangling);
+      MicrosoftCXXNameMangler Extra(Context, Stream);
+      Extra.mangleTemplateInstantiationName(TD, *TemplateArgs);
+
+      // Use the string backref vector to possibly get a back reference.
+      mangleSourceName(TemplateMangling);
+
+      // Memoize back reference for this type.
+      BackRefVec::iterator StringFound =
+          llvm::find(NameBackReferences, TemplateMangling);
+      if (StringFound != NameBackReferences.end()) {
+        TemplateArgBackReferences[ND] =
+            StringFound - NameBackReferences.begin();
+      }
+    } else {
+      Out << Found->second;
+    }
     return;
   }
 
@@ -1282,11 +1301,13 @@
   // Always start with the unqualified name.
 
   // Templates have their own context for back references.
-  ArgBackRefMap OuterArgsContext;
+  ArgBackRefMap OuterFunArgsContext;
+  ArgBackRefMap OuterTemplateArgsContext;
   BackRefVec OuterTemplateContext;
   PassObjectSizeArgsSet OuterPassObjectSizeArgs;
   NameBackReferences.swap(OuterTemplateContext);
-  TypeBackReferences.swap(OuterArgsContext);
+  FunArgBackReferences.swap(OuterFunArgsContext);
+  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
   PassObjectSizeArgs.swap(OuterPassObjectSizeArgs);
 
   mangleUnscopedTemplateName(TD);
@@ -1294,7 +1315,8 @@
 
   // Restore the previous back reference contexts.
   NameBackReferences.swap(OuterTemplateContext);
-  TypeBackReferences.swap(OuterArgsContext);
+  FunArgBackReferences.swap(OuterFunArgsContext);
+  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
   PassObjectSizeArgs.swap(OuterPassObjectSizeArgs);
 }
 
@@ -1699,8 +1721,8 @@
   }
 }
 
-void MicrosoftCXXNameMangler::mangleArgumentType(QualType T,
-                                                 SourceRange Range) {
+void MicrosoftCXXNameMangler::mangleFunctionArgumentType(QualType T,
+                                                         SourceRange Range) {
   // MSVC will backreference two canonically equivalent types that have slightly
   // different manglings when mangled alone.
 
@@ -1730,9 +1752,9 @@
     TypePtr = T.getCanonicalType().getAsOpaquePtr();
   }
 
-  ArgBackRefMap::iterator Found = TypeBackReferences.find(TypePtr);
+  ArgBackRefMap::iterator Found = FunArgBackReferences.find(TypePtr);
 
-  if (Found == TypeBackReferences.end()) {
+  if (Found == FunArgBackReferences.end()) {
     size_t OutSizeBefore = Out.tell();
 
     mangleType(T, Range, QMM_Drop);
@@ -1741,9 +1763,9 @@
     // Only types longer than 1 character are considered
     // and only 10 back references slots are available:
     bool LongerThanOneChar = (Out.tell() - OutSizeBefore > 1);
-    if (LongerThanOneChar && TypeBackReferences.size() < 10) {
-      size_t Size = TypeBackReferences.size();
-      TypeBackReferences[TypePtr] = Size;
+    if (LongerThanOneChar && FunArgBackReferences.size() < 10) {
+      size_t Size = FunArgBackReferences.size();
+      FunArgBackReferences[TypePtr] = Size;
     }
   } else {
     Out << Found->second;
@@ -1757,16 +1779,16 @@
 
   auto Iter = PassObjectSizeArgs.insert({Type, Dynamic}).first;
   auto *TypePtr = (const void *)&*Iter;
-  ArgBackRefMap::iterator Found = TypeBackReferences.find(TypePtr);
+  ArgBackRefMap::iterator Found = FunArgBackReferences.find(TypePtr);
 
-  if (Found == TypeBackReferences.end()) {
+  if (Found == FunArgBackReferences.end()) {
     std::string Name =
         Dynamic ? "__pass_dynamic_object_size" : "__pass_object_size";
     mangleArtificialTagType(TTK_Enum, Name + llvm::utostr(Type), {"__clang"});
 
-    if (TypeBackReferences.size() < 10) {
-      size_t Size = TypeBackReferences.size();
-      TypeBackReferences[TypePtr] = Size;
+    if (FunArgBackReferences.size() < 10) {
+      size_t Size = FunArgBackReferences.size();
+      FunArgBackReferences[TypePtr] = Size;
     }
   } else {
     Out << Found->second;
@@ -2192,12 +2214,12 @@
         Out << 'X';
       } else if (StructorType == Ctor_CopyingClosure) {
         // Copy constructor closure always takes an unqualified reference.
-        mangleArgumentType(getASTContext().getLValueReferenceType(
-                               Proto->getParamType(0)
-                                   ->getAs<LValueReferenceType>()
-                                   ->getPointeeType(),
-                               /*SpelledAsLValue=*/true),
-                           Range);
+        mangleFunctionArgumentType(getASTContext().getLValueReferenceType(
+                                       Proto->getParamType(0)
+                                           ->getAs<LValueReferenceType>()
+                                           ->getPointeeType(),
+                                       /*SpelledAsLValue=*/true),
+                                   Range);
         Out << '@';
       } else {
         llvm_unreachable("unexpected constructor closure!");
@@ -2239,7 +2261,7 @@
   } else {
     // Happens for function pointer type arguments for example.
     for (unsigned I = 0, E = Proto->getNumParams(); I != E; ++I) {
-      mangleArgumentType(Proto->getParamType(I), Range);
+      mangleFunctionArgumentType(Proto->getParamType(I), Range);
       // Mangle each pass_object_size parameter as if it's a parameter of enum
       // type passed directly after the parameter with the pass_object_size
       // attribute. The aforementioned enum's name is __pass_object_size, and we
@@ -2731,10 +2753,12 @@
   if (T->qual_empty() && !T->isSpecialized())
     return mangleType(T->getBaseType(), Range, QMM_Drop);
 
-  ArgBackRefMap OuterArgsContext;
+  ArgBackRefMap OuterFunArgsContext;
+  ArgBackRefMap OuterTemplateArgsContext;
   BackRefVec OuterTemplateContext;
 
-  TypeBackReferences.swap(OuterArgsContext);
+  FunArgBackReferences.swap(OuterFunArgsContext);
+  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
   NameBackReferences.swap(OuterTemplateContext);
 
   mangleTagTypeKind(TTK_Struct);
@@ -2758,7 +2782,8 @@
 
   Out << '@';
 
-  TypeBackReferences.swap(OuterArgsContext);
+  FunArgBackReferences.swap(OuterFunArgsContext);
+  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
   NameBackReferences.swap(OuterTemplateContext);
 }
 
diff --git a/clang/test/CodeGenCXX/mangle-ms-back-references-pr13207.cpp b/clang/test/CodeGenCXX/mangle-ms-back-references-pr13207.cpp
--- a/clang/test/CodeGenCXX/mangle-ms-back-references-pr13207.cpp
+++ b/clang/test/CodeGenCXX/mangle-ms-back-references-pr13207.cpp
@@ -191,3 +191,44 @@
 // CHECK: "??$fun_tmpl_recurse@H$1??$fun_tmpl_recurse@H$1?ident@fn_space@@YA?AURetVal@2@H@Z@fn_space@@YA?AURetVal@1@H@Z@fn_space@@YA?AURetVal@0@H@Z"
 // CHECK: "??$fun_tmpl_recurse@H$1?ident@fn_space@@YA?AURetVal@2@H@Z@fn_space@@YA?AURetVal@0@H@Z"
 }
+
+
+template <class T1, class T2, class T3, class T4, class T5, class T6, class T7,
+          class T8, class T9, class T10>
+struct Fooob {};
+
+using A0 = Fooob<int, int, int, int, int, int, int, int, int, int>;
+using A1 = Fooob<A0, A0, A0, A0, A0, A0, A0, A0, A0, A0>;
+using A2 = Fooob<A1, A1, A1, A1, A1, A1, A1, A1, A1, A1>;
+using A3 = Fooob<A2, A2, A2, A2, A2, A2, A2, A2, A2, A2>;
+using A4 = Fooob<A3, A3, A3, A3, A3, A3, A3, A3, A3, A3>;
+using A5 = Fooob<A4, A4, A4, A4, A4, A4, A4, A4, A4, A4>;
+using A6 = Fooob<A5, A5, A5, A5, A5, A5, A5, A5, A5, A5>;
+using A7 = Fooob<A6, A6, A6, A6, A6, A6, A6, A6, A6, A6>;
+using A8 = Fooob<A7, A7, A7, A7, A7, A7, A7, A7, A7, A7>;
+using A9 = Fooob<A8, A8, A8, A8, A8, A8, A8, A8, A8, A8>;
+using A10 = Fooob<A9, A9, A9, A9, A9, A9, A9, A9, A9, A9>;
+
+// This should take milliseconds, not minutes.
+void f(A9 a) {}
+// CHECK: "?f@@YAXU?$Fooob@U?$Fooob@U?$Fooob@U?$Fooob@U?$Fooob@U?$Fooob@U?$Fooob@U?$Fooob@U?$Fooob@U?$Fooob@HHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@@Z"
+
+
+template <class T1, class T2, class T3, class T4, class T5, class T6, class T7,
+          class T8, class T9, class T10, class T11, class T12, class T13,
+          class T14, class T15, class T16, class T17, class T18, class T19,
+          class T20>
+struct Food {};
+
+using B0 = Food<int, int, int, int, int, int, int, int, int, int,  int, int, int, int, int, int, int, int, int, int>;
+using B1 = Food<B0, B0, B0, B0, B0, B0, B0, B0, B0, B0,  B0, B0, B0, B0, B0, B0, B0, B0, B0, B0>;
+using B2 = Food<B1, B0, B0, B0, B0, B0, B0, B0, B0, B0,  B1, B1, B1, B1, B1, B1, B1, B1, B1, B1>;
+using B3 = Food<B2, B1, B0, B0, B0, B0, B0, B0, B0, B0,  B2, B2, B2, B2, B2, B2, B2, B2, B2, B2>;
+using B4 = Food<B3, B2, B1, B0, B0, B0, B0, B0, B0, B0,  B3, B3, B3, B3, B3, B3, B3, B3, B3, B3>;
+using B5 = Food<B4, B3, B2, B1, B0, B0, B0, B0, B0, B0,  B4, B4, B4, B4, B4, B4, B4, B4, B4, B4>;
+using B6 = Food<B5, B4, B3, B2, B1, B0, B0, B0, B0, B0,  B5, B5, B5, B5, B5, B5, B5, B5, B5, B5>;
+
+// This too should take milliseconds, not minutes.
+void f(B6 a) {}
+
+// CHECK: "?f@@YAXU?$Food@U?$Food@U?$Food@U?$Food@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U3@U3@U3@U3@U3@U3@U3@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U4@U4@U4@U4@U4@U4@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U3@U3@U3@U3@U3@U3@U3@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U5@U5@U5@U5@U5@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U3@U3@U3@U3@U3@U3@U3@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U4@U4@U4@U4@U4@U4@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U3@U3@U3@U3@U3@U3@U3@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U2@U2@U2@U2@U2@U2@U2@U2@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@U?$Food@HHHHHHHHHHHHHHHHHHHH@@U6@U6@U6@U6@U1@U1@U1@U1@U1@U1@U1@U1@U1@U1@@@@Z"