From: Eli Friedman <eli.friedman@gmail.com>
Date: Wed, 26 Sep 2012 02:36:12 +0000 (+0000)
Subject: Fix the AST representation for non-type template arguments to encode
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d7a6b1640e565487d163023a6a2e83f55476ae96;p=clang

Fix the AST representation for non-type template arguments to encode
enough information so we can mangle them correctly in cases involving
dependent parameter types. (This specifically impacts cases involving
null pointers and cases involving parameters of reference type.)
Fix the mangler to use this information instead of trying to scavenge
it out of the parameter declaration.

<rdar://problem/12296776>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164656 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/clang/AST/RecursiveASTVisitor.h b/include/clang/AST/RecursiveASTVisitor.h
index 22cd290858..f96e067978 100644
--- a/include/clang/AST/RecursiveASTVisitor.h
+++ b/include/clang/AST/RecursiveASTVisitor.h
@@ -721,6 +721,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgument(
   case TemplateArgument::Null:
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
+  case TemplateArgument::NullPtr:
     return true;
 
   case TemplateArgument::Type:
@@ -753,6 +754,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgumentLoc(
   case TemplateArgument::Null:
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
+  case TemplateArgument::NullPtr:
     return true;
 
   case TemplateArgument::Type: {
diff --git a/include/clang/AST/TemplateBase.h b/include/clang/AST/TemplateBase.h
index 5047028e5e..1c0abde5b7 100644
--- a/include/clang/AST/TemplateBase.h
+++ b/include/clang/AST/TemplateBase.h
@@ -28,11 +28,11 @@ namespace llvm {
 
 namespace clang {
 
-class Decl;
 class DiagnosticBuilder;
 class Expr;
 struct PrintingPolicy;
 class TypeSourceInfo;
+class ValueDecl;
 
 /// \brief Represents a template argument within a class template
 /// specialization.
@@ -43,12 +43,14 @@ public:
     /// \brief Represents an empty template argument, e.g., one that has not
     /// been deduced.
     Null = 0,
-    /// The template argument is a type. Its value is stored in the
-    /// TypeOrValue field.
+    /// The template argument is a type.
     Type,
-    /// The template argument is a declaration that was provided for a pointer
-    /// or reference non-type template parameter.
+    /// The template argument is a declaration that was provided for a pointer,
+    /// reference, or pointer to member non-type template parameter.
     Declaration,
+    /// The template argument is a null pointer or null pointer to member that
+    /// was provided for a non-type template parameter.
+    NullPtr,
     /// The template argument is an integral value stored in an llvm::APSInt
     /// that was provided for an integral non-type template parameter. 
     Integral,
@@ -72,6 +74,10 @@ private:
 
   union {
     uintptr_t TypeOrValue;
+    struct {
+      ValueDecl *D;
+      bool ForRefParam;
+    } DeclArg;
     struct {
       // We store a decomposed APSInt with the data allocated by ASTContext if
       // BitWidth > 64. The memory may be shared between multiple
@@ -101,15 +107,18 @@ public:
   TemplateArgument() : Kind(Null), TypeOrValue(0) { }
 
   /// \brief Construct a template type argument.
-  TemplateArgument(QualType T) : Kind(Type) {
+  TemplateArgument(QualType T, bool isNullPtr = false)
+    : Kind(isNullPtr ? NullPtr : Type) {
     TypeOrValue = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());
   }
 
   /// \brief Construct a template argument that refers to a
   /// declaration, which is either an external declaration or a
   /// template declaration.
-  TemplateArgument(Decl *D) : Kind(Declaration) {
-    TypeOrValue = reinterpret_cast<uintptr_t>(D);
+  TemplateArgument(ValueDecl *D, bool ForRefParam) : Kind(Declaration) {
+    assert(D && "Expected decl");
+    DeclArg.D = D;
+    DeclArg.ForRefParam = ForRefParam;
   }
 
   /// \brief Construct an integral constant template argument. The memory to
@@ -177,6 +186,10 @@ public:
     this->Args.NumArgs = NumArgs;
   }
 
+  static TemplateArgument getEmptyPack() {
+    return TemplateArgument((TemplateArgument*)0, 0);
+  }
+
   /// \brief Create a new template argument pack by copying the given set of
   /// template arguments.
   static TemplateArgument CreatePackCopy(ASTContext &Context,
@@ -205,34 +218,43 @@ public:
   /// \brief Determine whether this template argument is a pack expansion.
   bool isPackExpansion() const;
   
-  /// \brief Retrieve the template argument as a type.
+  /// \brief Retrieve the type for a type template argument.
   QualType getAsType() const {
-    if (Kind != Type)
-      return QualType();
-
+    assert(Kind == Type && "Unexpected kind");
     return QualType::getFromOpaquePtr(reinterpret_cast<void*>(TypeOrValue));
   }
 
-  /// \brief Retrieve the template argument as a declaration.
-  Decl *getAsDecl() const {
-    if (Kind != Declaration)
-      return 0;
-    return reinterpret_cast<Decl *>(TypeOrValue);
+  /// \brief Retrieve the declaration for a declaration non-type
+  /// template argument.
+  ValueDecl *getAsDecl() const {
+    assert(Kind == Declaration && "Unexpected kind");
+    return DeclArg.D;
+  }
+
+  /// \brief Retrieve whether a declaration is binding to a
+  /// reference parameter in a declaration non-type template argument.
+  bool isDeclForReferenceParam() const {
+    assert(Kind == Declaration && "Unexpected kind");
+    return DeclArg.ForRefParam;
   }
 
-  /// \brief Retrieve the template argument as a template name.
+  /// \brief Retrieve the type for null non-type template argument.
+  QualType getNullPtrType() const {
+    assert(Kind == NullPtr && "Unexpected kind");
+    return QualType::getFromOpaquePtr(reinterpret_cast<void*>(TypeOrValue));
+  }
+
+  /// \brief Retrieve the template name for a template name argument.
   TemplateName getAsTemplate() const {
-    if (Kind != Template)
-      return TemplateName();
-    
+    assert(Kind == Template && "Unexpected kind");
     return TemplateName::getFromVoidPointer(TemplateArg.Name);
   }
 
   /// \brief Retrieve the template argument as a template name; if the argument
   /// is a pack expansion, return the pattern as a template name.
   TemplateName getAsTemplateOrTemplatePattern() const {
-    if (Kind != Template && Kind != TemplateExpansion)
-      return TemplateName();
+    assert((Kind == Template || Kind == TemplateExpansion) &&
+           "Unexpected kind");
     
     return TemplateName::getFromVoidPointer(TemplateArg.Name);
   }
@@ -244,6 +266,7 @@ public:
   /// \brief Retrieve the template argument as an integral value.
   // FIXME: Provide a way to read the integral data without copying the value.
   llvm::APSInt getAsIntegral() const {
+    assert(Kind == Integral && "Unexpected kind");
     using namespace llvm;
     if (Integer.BitWidth <= 64)
       return APSInt(APInt(Integer.BitWidth, Integer.VAL), Integer.IsUnsigned);
@@ -255,23 +278,18 @@ public:
 
   /// \brief Retrieve the type of the integral value.
   QualType getIntegralType() const {
-    if (Kind != Integral)
-      return QualType();
-
+    assert(Kind == Integral && "Unexpected kind");
     return QualType::getFromOpaquePtr(Integer.Type);
   }
 
   void setIntegralType(QualType T) {
-    assert(Kind == Integral &&
-           "Cannot set the integral type of a non-integral template argument");
+    assert(Kind == Integral && "Unexpected kind");
     Integer.Type = T.getAsOpaquePtr();
   }
 
   /// \brief Retrieve the template argument as an expression.
   Expr *getAsExpr() const {
-    if (Kind != Expression)
-      return 0;
-
+    assert(Kind == Expression && "Unexpected kind");
     return reinterpret_cast<Expr *>(TypeOrValue);
   }
 
@@ -436,7 +454,17 @@ public:
     assert(Argument.getKind() == TemplateArgument::Declaration);
     return LocInfo.getAsExpr();
   }
-  
+
+  Expr *getSourceNullPtrExpression() const {
+    assert(Argument.getKind() == TemplateArgument::NullPtr);
+    return LocInfo.getAsExpr();
+  }
+
+  Expr *getSourceIntegralExpression() const {
+    assert(Argument.getKind() == TemplateArgument::Integral);
+    return LocInfo.getAsExpr();
+  }
+
   NestedNameSpecifierLoc getTemplateQualifierLoc() const {
     assert(Argument.getKind() == TemplateArgument::Template ||
            Argument.getKind() == TemplateArgument::TemplateExpansion);
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 9fd40b206d..f19a2aaaf7 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -3684,11 +3684,14 @@ ASTContext::getCanonicalTemplateArgument(const TemplateArgument &Arg) const {
       return Arg;
 
     case TemplateArgument::Declaration: {
-      if (Decl *D = Arg.getAsDecl())
-          return TemplateArgument(D->getCanonicalDecl());
-      return TemplateArgument((Decl*)0);
+      ValueDecl *D = cast<ValueDecl>(Arg.getAsDecl()->getCanonicalDecl());
+      return TemplateArgument(D, Arg.isDeclForReferenceParam());
     }
 
+    case TemplateArgument::NullPtr:
+      return TemplateArgument(getCanonicalType(Arg.getNullPtrType()),
+                              /*isNullPtr*/true);
+
     case TemplateArgument::Template:
       return TemplateArgument(getCanonicalTemplateName(Arg.getAsTemplate()));
 
diff --git a/lib/AST/ASTDiagnostic.cpp b/lib/AST/ASTDiagnostic.cpp
index a605f1a40c..411c337321 100644
--- a/lib/AST/ASTDiagnostic.cpp
+++ b/lib/AST/ASTDiagnostic.cpp
@@ -923,7 +923,9 @@ class TemplateDiff {
     bool isVariadic = DefaultTTPD->isParameterPack();
 
     TemplateArgument TA = DefaultTTPD->getDefaultArgument().getArgument();
-    TemplateDecl *DefaultTD = TA.getAsTemplate().getAsTemplateDecl();
+    TemplateDecl *DefaultTD = 0;
+    if (TA.getKind() != TemplateArgument::Null)
+      DefaultTD = TA.getAsTemplate().getAsTemplateDecl();
 
     if (!Iter.isEnd())
       ArgDecl = Iter->getAsTemplate().getAsTemplateDecl();
diff --git a/lib/AST/ASTImporter.cpp b/lib/AST/ASTImporter.cpp
index 34e699496b..a90026072b 100644
--- a/lib/AST/ASTImporter.cpp
+++ b/lib/AST/ASTImporter.cpp
@@ -288,7 +288,7 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
       
   case TemplateArgument::Type:
     return Context.IsStructurallyEquivalent(Arg1.getAsType(), Arg2.getAsType());
-      
+
   case TemplateArgument::Integral:
     if (!Context.IsStructurallyEquivalent(Arg1.getIntegralType(), 
                                           Arg2.getIntegralType()))
@@ -297,10 +297,11 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     return llvm::APSInt::isSameValue(Arg1.getAsIntegral(), Arg2.getAsIntegral());
       
   case TemplateArgument::Declaration:
-    if (!Arg1.getAsDecl() || !Arg2.getAsDecl())
-      return !Arg1.getAsDecl() && !Arg2.getAsDecl();
     return Context.IsStructurallyEquivalent(Arg1.getAsDecl(), Arg2.getAsDecl());
-      
+
+  case TemplateArgument::NullPtr:
+    return true; // FIXME: Is this correct?
+
   case TemplateArgument::Template:
     return IsStructurallyEquivalent(Context, 
                                     Arg1.getAsTemplate(), 
@@ -1976,11 +1977,20 @@ ASTNodeImporter::ImportTemplateArgument(const TemplateArgument &From) {
     return TemplateArgument(From, ToType);
   }
 
-  case TemplateArgument::Declaration:
-    if (Decl *To = Importer.Import(From.getAsDecl()))
-      return TemplateArgument(To);
+  case TemplateArgument::Declaration: {
+    ValueDecl *FromD = From.getAsDecl();
+    if (ValueDecl *To = cast_or_null<ValueDecl>(Importer.Import(FromD)))
+      return TemplateArgument(To, From.isDeclForReferenceParam());
     return TemplateArgument();
-      
+  }
+
+  case TemplateArgument::NullPtr: {
+    QualType ToType = Importer.Import(From.getNullPtrType());
+    if (ToType.isNull())
+      return TemplateArgument();
+    return TemplateArgument(ToType, /*isNullPtr*/true);
+  }
+
   case TemplateArgument::Template: {
     TemplateName ToTemplate = Importer.Import(From.getAsTemplate());
     if (ToTemplate.isNull())
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 13f931ae0b..8553e030e2 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -126,12 +126,12 @@ static LinkageInfo getLVForTemplateArgumentList(const TemplateArgument *Args,
       break;
 
     case TemplateArgument::Declaration:
-      // The decl can validly be null as the representation of nullptr
-      // arguments, valid only in C++0x.
-      if (Decl *D = Args[I].getAsDecl()) {
-        if (NamedDecl *ND = dyn_cast<NamedDecl>(D))
-          LV.mergeWithMin(getLVForDecl(ND, OnlyTemplate));
-      }
+      if (NamedDecl *ND = dyn_cast<NamedDecl>(Args[I].getAsDecl()))
+        LV.mergeWithMin(getLVForDecl(ND, OnlyTemplate));
+      break;
+
+    case TemplateArgument::NullPtr:
+      LV.mergeWithMin(getLVForType(Args[I].getNullPtrType()));
       break;
 
     case TemplateArgument::Template:
diff --git a/lib/AST/DumpXML.cpp b/lib/AST/DumpXML.cpp
index 29d8c62c13..11e3b529a4 100644
--- a/lib/AST/DumpXML.cpp
+++ b/lib/AST/DumpXML.cpp
@@ -316,12 +316,12 @@ struct XMLDumper : public XMLDeclVisitor<XMLDumper>,
     }
     case TemplateArgument::Template:
     case TemplateArgument::TemplateExpansion:
+    case TemplateArgument::NullPtr:
       // FIXME: Implement!
       break;
         
     case TemplateArgument::Declaration: {
-      if (Decl *D = A.getAsDecl())
-        visitDeclRef(D);
+      visitDeclRef(A.getAsDecl());
       break;
     }
     case TemplateArgument::Integral: {
diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index 3a168017d7..d8c6594d02 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -343,17 +343,10 @@ private:
   void mangleCXXDtorType(CXXDtorType T);
 
   void mangleTemplateArgs(const ASTTemplateArgumentListInfo &TemplateArgs);
-  void mangleTemplateArgs(TemplateName Template,
-                          const TemplateArgument *TemplateArgs,
-                          unsigned NumTemplateArgs);  
-  void mangleTemplateArgs(const TemplateParameterList &PL,
-                          const TemplateArgument *TemplateArgs,
+  void mangleTemplateArgs(const TemplateArgument *TemplateArgs,
                           unsigned NumTemplateArgs);
-  void mangleTemplateArgs(const TemplateParameterList &PL,
-                          const TemplateArgumentList &AL);
-  void mangleTemplateArg(const NamedDecl *P, TemplateArgument A);
-  void mangleUnresolvedTemplateArgs(const TemplateArgument *args,
-                                    unsigned numArgs);
+  void mangleTemplateArgs(const TemplateArgumentList &AL);
+  void mangleTemplateArg(TemplateArgument A);
 
   void mangleTemplateParameter(unsigned Index);
 
@@ -570,8 +563,7 @@ void CXXNameMangler::mangleName(const NamedDecl *ND) {
     const TemplateArgumentList *TemplateArgs = 0;
     if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
       mangleUnscopedTemplateName(TD);
-      TemplateParameterList *TemplateParameters = TD->getTemplateParameters();
-      mangleTemplateArgs(*TemplateParameters, *TemplateArgs);
+      mangleTemplateArgs(*TemplateArgs);
       return;
     }
 
@@ -593,8 +585,7 @@ void CXXNameMangler::mangleName(const TemplateDecl *TD,
 
   if (DC->isTranslationUnit() || isStdNamespace(DC)) {
     mangleUnscopedTemplateName(TD);
-    TemplateParameterList *TemplateParameters = TD->getTemplateParameters();
-    mangleTemplateArgs(*TemplateParameters, TemplateArgs, NumTemplateArgs);
+    mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
   } else {
     mangleNestedName(TD, TemplateArgs, NumTemplateArgs);
   }
@@ -738,8 +729,7 @@ void CXXNameMangler::manglePrefix(QualType type) {
       // FIXME: GCC does not appear to mangle the template arguments when
       // the template in question is a dependent template name. Should we
       // emulate that badness?
-      mangleTemplateArgs(TST->getTemplateName(), TST->getArgs(),
-                         TST->getNumArgs());
+      mangleTemplateArgs(TST->getArgs(), TST->getNumArgs());
       addSubstitution(QualType(TST, 0));
     }
   } else if (const DependentTemplateSpecializationType *DTST
@@ -752,7 +742,7 @@ void CXXNameMangler::manglePrefix(QualType type) {
     // FIXME: GCC does not appear to mangle the template arguments when
     // the template in question is a dependent template name. Should we
     // emulate that badness?
-    mangleTemplateArgs(Template, DTST->getArgs(), DTST->getNumArgs());
+    mangleTemplateArgs(DTST->getArgs(), DTST->getNumArgs());
   } else {
     // We use the QualType mangle type variant here because it handles
     // substitutions.
@@ -943,7 +933,7 @@ void CXXNameMangler::mangleUnresolvedPrefix(NestedNameSpecifier *qualifier,
       }
       }
 
-      mangleUnresolvedTemplateArgs(tst->getArgs(), tst->getNumArgs());
+      mangleTemplateArgs(tst->getArgs(), tst->getNumArgs());
       break;
     }
 
@@ -960,7 +950,7 @@ void CXXNameMangler::mangleUnresolvedPrefix(NestedNameSpecifier *qualifier,
       const DependentTemplateSpecializationType *tst
         = cast<DependentTemplateSpecializationType>(type);
       mangleSourceName(tst->getIdentifier());
-      mangleUnresolvedTemplateArgs(tst->getArgs(), tst->getNumArgs());
+      mangleTemplateArgs(tst->getArgs(), tst->getNumArgs());
       break;
     }
     }
@@ -1229,8 +1219,7 @@ void CXXNameMangler::mangleNestedName(const NamedDecl *ND,
   const TemplateArgumentList *TemplateArgs = 0;
   if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
     mangleTemplatePrefix(TD);
-    TemplateParameterList *TemplateParameters = TD->getTemplateParameters();
-    mangleTemplateArgs(*TemplateParameters, *TemplateArgs);
+    mangleTemplateArgs(*TemplateArgs);
   }
   else {
     manglePrefix(DC, NoFunction);
@@ -1247,8 +1236,7 @@ void CXXNameMangler::mangleNestedName(const TemplateDecl *TD,
   Out << 'N';
 
   mangleTemplatePrefix(TD);
-  TemplateParameterList *TemplateParameters = TD->getTemplateParameters();
-  mangleTemplateArgs(*TemplateParameters, TemplateArgs, NumTemplateArgs);
+  mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
 
   Out << 'E';
 }
@@ -1421,8 +1409,7 @@ void CXXNameMangler::manglePrefix(const DeclContext *DC, bool NoFunction) {
   const TemplateArgumentList *TemplateArgs = 0;
   if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
     mangleTemplatePrefix(TD);
-    TemplateParameterList *TemplateParameters = TD->getTemplateParameters();
-    mangleTemplateArgs(*TemplateParameters, *TemplateArgs);
+    mangleTemplateArgs(*TemplateArgs);
   }
   else if(NoFunction && (isa<FunctionDecl>(ND) || isa<ObjCMethodDecl>(ND)))
     return;
@@ -2172,7 +2159,7 @@ void CXXNameMangler::mangleType(const TemplateSpecializationType *T) {
     // FIXME: GCC does not appear to mangle the template arguments when
     // the template in question is a dependent template name. Should we
     // emulate that badness?
-    mangleTemplateArgs(T->getTemplateName(), T->getArgs(), T->getNumArgs());
+    mangleTemplateArgs(T->getArgs(), T->getNumArgs());
     addSubstitution(QualType(T, 0));
   }
 }
@@ -2198,7 +2185,7 @@ void CXXNameMangler::mangleType(const DependentTemplateSpecializationType *T) {
   // FIXME: GCC does not appear to mangle the template arguments when
   // the template in question is a dependent template name. Should we
   // emulate that badness?
-  mangleTemplateArgs(Prefix, T->getArgs(), T->getNumArgs());    
+  mangleTemplateArgs(T->getArgs(), T->getNumArgs());    
   Out << 'E';
 }
 
@@ -3053,50 +3040,28 @@ void CXXNameMangler::mangleTemplateArgs(
   // <template-args> ::= I <template-arg>+ E
   Out << 'I';
   for (unsigned i = 0, e = TemplateArgs.NumTemplateArgs; i != e; ++i)
-    mangleTemplateArg(0, TemplateArgs.getTemplateArgs()[i].getArgument());
+    mangleTemplateArg(TemplateArgs.getTemplateArgs()[i].getArgument());
   Out << 'E';
 }
 
-void CXXNameMangler::mangleTemplateArgs(TemplateName Template,
-                                        const TemplateArgument *TemplateArgs,
-                                        unsigned NumTemplateArgs) {
-  if (TemplateDecl *TD = Template.getAsTemplateDecl())
-    return mangleTemplateArgs(*TD->getTemplateParameters(), TemplateArgs,
-                              NumTemplateArgs);
-  
-  mangleUnresolvedTemplateArgs(TemplateArgs, NumTemplateArgs);
-}
-
-void CXXNameMangler::mangleUnresolvedTemplateArgs(const TemplateArgument *args,
-                                                  unsigned numArgs) {
-  // <template-args> ::= I <template-arg>+ E
-  Out << 'I';
-  for (unsigned i = 0; i != numArgs; ++i)
-    mangleTemplateArg(0, args[i]);
-  Out << 'E';
-}
-
-void CXXNameMangler::mangleTemplateArgs(const TemplateParameterList &PL,
-                                        const TemplateArgumentList &AL) {
+void CXXNameMangler::mangleTemplateArgs(const TemplateArgumentList &AL) {
   // <template-args> ::= I <template-arg>+ E
   Out << 'I';
   for (unsigned i = 0, e = AL.size(); i != e; ++i)
-    mangleTemplateArg(PL.getParam(i), AL[i]);
+    mangleTemplateArg(AL[i]);
   Out << 'E';
 }
 
-void CXXNameMangler::mangleTemplateArgs(const TemplateParameterList &PL,
-                                        const TemplateArgument *TemplateArgs,
+void CXXNameMangler::mangleTemplateArgs(const TemplateArgument *TemplateArgs,
                                         unsigned NumTemplateArgs) {
   // <template-args> ::= I <template-arg>+ E
   Out << 'I';
   for (unsigned i = 0; i != NumTemplateArgs; ++i)
-    mangleTemplateArg(PL.getParam(i), TemplateArgs[i]);
+    mangleTemplateArg(TemplateArgs[i]);
   Out << 'E';
 }
 
-void CXXNameMangler::mangleTemplateArg(const NamedDecl *P,
-                                       TemplateArgument A) {
+void CXXNameMangler::mangleTemplateArg(TemplateArgument A) {
   // <template-arg> ::= <type>              # type or template
   //                ::= X <expression> E    # expression
   //                ::= <expr-primary>      # simple expressions
@@ -3145,25 +3110,12 @@ void CXXNameMangler::mangleTemplateArg(const NamedDecl *P,
     mangleIntegerLiteral(A.getIntegralType(), A.getAsIntegral());
     break;
   case TemplateArgument::Declaration: {
-    assert(P && "Missing template parameter for declaration argument");
     //  <expr-primary> ::= L <mangled-name> E # external name
-    //  <expr-primary> ::= L <type> 0 E
     // Clang produces AST's where pointer-to-member-function expressions
     // and pointer-to-function expressions are represented as a declaration not
     // an expression. We compensate for it here to produce the correct mangling.
-    const NonTypeTemplateParmDecl *Parameter = cast<NonTypeTemplateParmDecl>(P);
-
-    // Handle NULL pointer arguments.
-    if (!A.getAsDecl()) {
-      Out << "L";
-      mangleType(Parameter->getType());
-      Out << "0E";
-      break;
-    }
-    
-
-    NamedDecl *D = cast<NamedDecl>(A.getAsDecl());
-    bool compensateMangling = !Parameter->getType()->isReferenceType();
+    ValueDecl *D = A.getAsDecl();
+    bool compensateMangling = !A.isDeclForReferenceParam();
     if (compensateMangling) {
       Out << 'X';
       mangleOperatorName(OO_Amp, 1);
@@ -3186,14 +3138,20 @@ void CXXNameMangler::mangleTemplateArg(const NamedDecl *P,
 
     break;
   }
-      
+  case TemplateArgument::NullPtr: {
+    //  <expr-primary> ::= L <type> 0 E
+    Out << 'L';
+    mangleType(A.getNullPtrType());
+    Out << "0E";
+    break;
+  }
   case TemplateArgument::Pack: {
     // Note: proposal by Mike Herrick on 12/20/10
     Out << 'J';
     for (TemplateArgument::pack_iterator PA = A.pack_begin(), 
                                       PAEnd = A.pack_end();
          PA != PAEnd; ++PA)
-      mangleTemplateArg(P, *PA);
+      mangleTemplateArg(*PA);
     Out << 'E';
   }
   }
diff --git a/lib/AST/StmtProfile.cpp b/lib/AST/StmtProfile.cpp
index 0c3186fec2..bfd3132506 100644
--- a/lib/AST/StmtProfile.cpp
+++ b/lib/AST/StmtProfile.cpp
@@ -1173,6 +1173,10 @@ void StmtProfiler::VisitTemplateArgument(const TemplateArgument &Arg) {
     VisitDecl(Arg.getAsDecl());
     break;
 
+  case TemplateArgument::NullPtr:
+    VisitType(Arg.getNullPtrType());
+    break;
+
   case TemplateArgument::Integral:
     Arg.getAsIntegral().Profile(ID);
     VisitType(Arg.getIntegralType());
diff --git a/lib/AST/TemplateBase.cpp b/lib/AST/TemplateBase.cpp
index 95ff4edf1d..968a6be16e 100644
--- a/lib/AST/TemplateBase.cpp
+++ b/lib/AST/TemplateBase.cpp
@@ -77,7 +77,7 @@ TemplateArgument TemplateArgument::CreatePackCopy(ASTContext &Context,
                                                   const TemplateArgument *Args,
                                                   unsigned NumArgs) {
   if (NumArgs == 0)
-    return TemplateArgument(0, 0);
+    return getEmptyPack();
   
   TemplateArgument *Storage = new (Context) TemplateArgument [NumArgs];
   std::copy(Args, Args + NumArgs, Storage);
@@ -99,12 +99,11 @@ bool TemplateArgument::isDependent() const {
     return true;
 
   case Declaration:
-    if (Decl *D = getAsDecl()) {
-      if (DeclContext *DC = dyn_cast<DeclContext>(D))
-        return DC->isDependentContext();
-      return D->getDeclContext()->isDependentContext();
-    }
-      
+    if (DeclContext *DC = dyn_cast<DeclContext>(getAsDecl()))
+      return DC->isDependentContext();
+    return getAsDecl()->getDeclContext()->isDependentContext();
+
+  case NullPtr:
     return false;
 
   case Integral:
@@ -141,11 +140,11 @@ bool TemplateArgument::isInstantiationDependent() const {
     return true;
     
   case Declaration:
-    if (Decl *D = getAsDecl()) {
-      if (DeclContext *DC = dyn_cast<DeclContext>(D))
-        return DC->isDependentContext();
-      return D->getDeclContext()->isDependentContext();
-    }
+    if (DeclContext *DC = dyn_cast<DeclContext>(getAsDecl()))
+      return DC->isDependentContext();
+    return getAsDecl()->getDeclContext()->isDependentContext();
+
+  case NullPtr:
     return false;
       
   case Integral:
@@ -174,6 +173,7 @@ bool TemplateArgument::isPackExpansion() const {
   case Integral:
   case Pack:    
   case Template:
+  case NullPtr:
     return false;
       
   case TemplateExpansion:
@@ -195,6 +195,7 @@ bool TemplateArgument::containsUnexpandedParameterPack() const {
   case Declaration:
   case Integral:
   case TemplateExpansion:
+  case NullPtr:
     break;
 
   case Type:
@@ -286,12 +287,16 @@ bool TemplateArgument::structurallyEquals(const TemplateArgument &Other) const {
   switch (getKind()) {
   case Null:
   case Type:
-  case Declaration:
   case Expression:      
   case Template:
   case TemplateExpansion:
+  case NullPtr:
     return TypeOrValue == Other.TypeOrValue;
 
+  case Declaration:
+    return getAsDecl() == Other.getAsDecl() && 
+           isDeclForReferenceParam() && Other.isDeclForReferenceParam();
+
   case Integral:
     return getIntegralType() == Other.getIntegralType() &&
            getAsIntegral() == Other.getAsIntegral();
@@ -319,12 +324,13 @@ TemplateArgument TemplateArgument::getPackExpansionPattern() const {
     
   case TemplateExpansion:
     return TemplateArgument(getAsTemplateOrTemplatePattern());
-    
+
   case Declaration:
   case Integral:
   case Pack:
   case Null:
   case Template:
+  case NullPtr:
     return TemplateArgument();
   }
 
@@ -348,18 +354,20 @@ void TemplateArgument::print(const PrintingPolicy &Policy,
   }
     
   case Declaration: {
-    if (NamedDecl *ND = dyn_cast_or_null<NamedDecl>(getAsDecl())) {
-      if (ND->getDeclName()) {
-        Out << *ND;
-      } else {
-        Out << "<anonymous>";
-      }
+    NamedDecl *ND = cast<NamedDecl>(getAsDecl());
+    if (ND->getDeclName()) {
+      // FIXME: distinguish between pointer and reference args?
+      Out << *ND;
     } else {
-      Out << "nullptr";
+      Out << "<anonymous>";
     }
     break;
   }
-    
+
+  case NullPtr: {
+    Out << "nullptr";
+  }
+
   case Template:
     getAsTemplate().print(Out, Policy);
     break;
@@ -411,6 +419,9 @@ SourceRange TemplateArgumentLoc::getSourceRange() const {
   case TemplateArgument::Declaration:
     return getSourceDeclExpression()->getSourceRange();
 
+  case TemplateArgument::NullPtr:
+    return getSourceNullPtrExpression()->getSourceRange();
+
   case TemplateArgument::Type:
     if (TypeSourceInfo *TSI = getTypeSourceInfo())
       return TSI->getTypeLoc().getSourceRange();
@@ -430,6 +441,8 @@ SourceRange TemplateArgumentLoc::getSourceRange() const {
     return SourceRange(getTemplateNameLoc(), getTemplateEllipsisLoc());
 
   case TemplateArgument::Integral:
+    return getSourceIntegralExpression()->getSourceRange();
+
   case TemplateArgument::Pack:
   case TemplateArgument::Null:
     return SourceRange();
@@ -490,6 +503,7 @@ TemplateArgumentLoc::getPackExpansionPattern(SourceLocation &Ellipsis,
                                getTemplateNameLoc());
     
   case TemplateArgument::Declaration:
+  case TemplateArgument::NullPtr:
   case TemplateArgument::Template:
   case TemplateArgument::Integral:
   case TemplateArgument::Pack:
@@ -512,8 +526,9 @@ const DiagnosticBuilder &clang::operator<<(const DiagnosticBuilder &DB,
     return DB << Arg.getAsType();
       
   case TemplateArgument::Declaration:
-    if (Decl *D = Arg.getAsDecl())
-      return DB << D;
+    return DB << Arg.getAsDecl();
+
+  case TemplateArgument::NullPtr:
     return DB << "nullptr";
       
   case TemplateArgument::Integral:
diff --git a/lib/AST/TypeLoc.cpp b/lib/AST/TypeLoc.cpp
index bd30a65259..945e783835 100644
--- a/lib/AST/TypeLoc.cpp
+++ b/lib/AST/TypeLoc.cpp
@@ -302,6 +302,9 @@ void TemplateSpecializationTypeLoc::initializeArgLocs(ASTContext &Context,
     case TemplateArgument::Declaration:
     case TemplateArgument::Integral:
     case TemplateArgument::Pack:
+    case TemplateArgument::NullPtr:
+      llvm_unreachable("Impossible TemplateArgument");
+
     case TemplateArgument::Expression:
       ArgInfos[i] = TemplateArgumentLocInfo(Args[i].getAsExpr());
       break;
@@ -311,7 +314,7 @@ void TemplateSpecializationTypeLoc::initializeArgLocs(ASTContext &Context,
                           Context.getTrivialTypeSourceInfo(Args[i].getAsType(), 
                                                            Loc));
       break;
-        
+
     case TemplateArgument::Template:
     case TemplateArgument::TemplateExpansion: {
       NestedNameSpecifierLocBuilder Builder;
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index 8da6f8da9c..d5efd757c8 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -1798,6 +1798,7 @@ addAssociatedClassesAndNamespaces(AssociatedLookup &Result,
     case TemplateArgument::Declaration:
     case TemplateArgument::Integral:
     case TemplateArgument::Expression:
+    case TemplateArgument::NullPtr:
       // [Note: non-type template arguments do not contribute to the set of
       //  associated namespaces. ]
       break;
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index bc40cbb8c9..0efe710acc 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -2843,6 +2843,7 @@ bool Sema::CheckTemplateArgument(NamedDecl *Param,
 
     case TemplateArgument::Declaration:
     case TemplateArgument::Integral:
+    case TemplateArgument::NullPtr:
       // We've already checked this template argument, so just copy
       // it to the list of converted arguments.
       Converted.push_back(Arg.getArgument());
@@ -2977,6 +2978,8 @@ bool Sema::CheckTemplateArgument(NamedDecl *Param,
     llvm_unreachable("Declaration argument with template template parameter");
   case TemplateArgument::Integral:
     llvm_unreachable("Integral argument with template template parameter");
+  case TemplateArgument::NullPtr:
+    llvm_unreachable("Null pointer argument with template template parameter");
 
   case TemplateArgument::Pack:
     llvm_unreachable("Caller must expand template argument packs");
@@ -3068,15 +3071,12 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
       if (*Expansions == ArgumentPack.size()) {
         // We're done with this parameter pack. Pack up its arguments and add
         // them to the list.
-        if (ArgumentPack.empty())
-          Converted.push_back(TemplateArgument(0, 0));
-        else {
-          Converted.push_back(
-            TemplateArgument::CreatePackCopy(Context,
-                                             ArgumentPack.data(),
-                                             ArgumentPack.size()));
-          ArgumentPack.clear();
-        }
+        Converted.push_back(
+          TemplateArgument::CreatePackCopy(Context,
+                                           ArgumentPack.data(),
+                                           ArgumentPack.size()));
+        ArgumentPack.clear();
+
         // This argument is assigned to the next parameter.
         ++Param;
         continue;
@@ -3143,15 +3143,11 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
 
         // Push the argument pack onto the list of converted arguments.
         if (InFinalParameterPack) {
-          if (ArgumentPack.empty())
-            Converted.push_back(TemplateArgument(0, 0));
-          else {
-            Converted.push_back(
-              TemplateArgument::CreatePackCopy(Context,
-                                               ArgumentPack.data(),
-                                               ArgumentPack.size()));
-            ArgumentPack.clear();
-          }
+          Converted.push_back(
+            TemplateArgument::CreatePackCopy(Context,
+                                             ArgumentPack.data(),
+                                             ArgumentPack.size()));
+          ArgumentPack.clear();
         } else if (ExpansionIntoFixedList) {
           // We have expanded a pack into a fixed list.
           *ExpansionIntoFixedList = true;
@@ -3185,14 +3181,10 @@ bool Sema::CheckTemplateArgumentList(TemplateDecl *Template,
       if (Param + 1 != ParamEnd)
         return true;
 
-      if (ArgumentPack.empty())
-        Converted.push_back(TemplateArgument(0, 0));
-      else {
-        Converted.push_back(TemplateArgument::CreatePackCopy(Context,
-                                                         ArgumentPack.data(),
-                                                         ArgumentPack.size()));
-        ArgumentPack.clear();
-      }
+      Converted.push_back(TemplateArgument::CreatePackCopy(Context,
+                                                       ArgumentPack.data(),
+                                                       ArgumentPack.size()));
+      ArgumentPack.clear();
 
       ++Param;
       continue;
@@ -3679,7 +3671,7 @@ CheckTemplateArgumentAddressOfObjectOrFunction(Sema &S,
     switch (isNullPointerValueTemplateArgument(S, Param, ParamType, Arg)) {
     case NPV_NullPointer:
       S.Diag(Arg->getExprLoc(), diag::warn_cxx98_compat_template_arg_null);
-      Converted = TemplateArgument((Decl *)0);
+      Converted = TemplateArgument(ParamType, /*isNullPtr*/true);
       return false;
 
     case NPV_Error:
@@ -3767,7 +3759,7 @@ CheckTemplateArgumentAddressOfObjectOrFunction(Sema &S,
     return true;
   }
 
-  NamedDecl *Entity = DRE->getDecl();
+  ValueDecl *Entity = DRE->getDecl();
 
   // Cannot refer to non-static data members
   if (FieldDecl *Field = dyn_cast<FieldDecl>(Entity)) {
@@ -3955,7 +3947,8 @@ CheckTemplateArgumentAddressOfObjectOrFunction(Sema &S,
   }
 
   // Create the template argument.
-  Converted = TemplateArgument(Entity->getCanonicalDecl());
+  Converted = TemplateArgument(cast<ValueDecl>(Entity->getCanonicalDecl()),
+                               ParamType->isReferenceType());
   S.MarkAnyDeclReferenced(Arg->getLocStart(), Entity);
   return false;
 }
@@ -3976,7 +3969,7 @@ static bool CheckTemplateArgumentPointerToMember(Sema &S,
     return true;
   case NPV_NullPointer:
     S.Diag(Arg->getExprLoc(), diag::warn_cxx98_compat_template_arg_null);
-    Converted = TemplateArgument((Decl *)0);
+    Converted = TemplateArgument(ParamType, /*isNullPtr*/true);
     return false;
   case NPV_NotNullPointer:
     break;
@@ -4045,10 +4038,12 @@ static bool CheckTemplateArgumentPointerToMember(Sema &S,
         if (isa<NonTypeTemplateParmDecl>(VD) ||
             (isa<VarDecl>(VD) &&
              S.Context.getCanonicalType(VD->getType()).isConstQualified())) {
-          if (Arg->isTypeDependent() || Arg->isValueDependent())
+          if (Arg->isTypeDependent() || Arg->isValueDependent()) {
             Converted = TemplateArgument(Arg);
-          else
-            Converted = TemplateArgument(VD->getCanonicalDecl());
+          } else {
+            VD = cast<ValueDecl>(VD->getCanonicalDecl());
+            Converted = TemplateArgument(VD, /*isReferenceParam*/false);
+          }
           return Invalid;
         }
       }
@@ -4069,10 +4064,12 @@ static bool CheckTemplateArgumentPointerToMember(Sema &S,
 
     // Okay: this is the address of a non-static member, and therefore
     // a member pointer constant.
-    if (Arg->isTypeDependent() || Arg->isValueDependent())
+    if (Arg->isTypeDependent() || Arg->isValueDependent()) {
       Converted = TemplateArgument(Arg);
-    else
-      Converted = TemplateArgument(DRE->getDecl()->getCanonicalDecl());
+    } else {
+      ValueDecl *D = cast<ValueDecl>(DRE->getDecl()->getCanonicalDecl());
+      Converted = TemplateArgument(D, /*isReferenceParam*/false);
+    }
     return Invalid;
   }
 
@@ -4425,7 +4422,7 @@ ExprResult Sema::CheckTemplateArgument(NonTypeTemplateParmDecl *Param,
       
     case NPV_NullPointer:
       Diag(Arg->getExprLoc(), diag::warn_cxx98_compat_template_arg_null);
-      Converted = TemplateArgument((Decl *)0);
+      Converted = TemplateArgument(ParamType, /*isNullPtr*/true);
       return Owned(Arg);
     }
   }
@@ -4448,7 +4445,7 @@ ExprResult Sema::CheckTemplateArgument(NonTypeTemplateParmDecl *Param,
 bool Sema::CheckTemplateArgument(TemplateTemplateParmDecl *Param,
                                  const TemplateArgumentLoc &Arg,
                                  unsigned ArgumentPackIndex) {
-  TemplateName Name = Arg.getArgument().getAsTemplate();
+  TemplateName Name = Arg.getArgument().getAsTemplateOrTemplatePattern();
   TemplateDecl *Template = Name.getAsTemplateDecl();
   if (!Template) {
     // Any dependent template name is fine.
@@ -4497,12 +4494,9 @@ ExprResult
 Sema::BuildExpressionFromDeclTemplateArgument(const TemplateArgument &Arg,
                                               QualType ParamType,
                                               SourceLocation Loc) {
-  assert(Arg.getKind() == TemplateArgument::Declaration &&
-         "Only declaration template arguments permitted here");
-  
   // For a NULL non-type template argument, return nullptr casted to the
   // parameter's type.
-  if (!Arg.getAsDecl()) {
+  if (Arg.getKind() == TemplateArgument::NullPtr) {
     return ImpCastExprToType(
              new (Context) CXXNullPtrLiteralExpr(Context.NullPtrTy, Loc),
                              ParamType,
@@ -4510,7 +4504,9 @@ Sema::BuildExpressionFromDeclTemplateArgument(const TemplateArgument &Arg,
                                ? CK_NullToMemberPointer
                                : CK_NullToPointer);
   }
-  
+  assert(Arg.getKind() == TemplateArgument::Declaration &&
+         "Only declaration template arguments permitted here");
+
   ValueDecl *VD = cast<ValueDecl>(Arg.getAsDecl());
 
   if (VD->getDeclContext()->isRecord() &&
@@ -5105,10 +5101,10 @@ static bool CheckNonTypeClassTemplatePartialSpecializationArgs(Sema &S,
       continue;
     }
 
-    Expr *ArgExpr = Args[I].getAsExpr();
-    if (!ArgExpr) {
+    if (Args[I].getKind() != TemplateArgument::Expression)
       continue;
-    }
+
+    Expr *ArgExpr = Args[I].getAsExpr();
 
     // We can have a pack expansion of any of the bullets below.
     if (PackExpansionExpr *Expansion = dyn_cast<PackExpansionExpr>(ArgExpr))
diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index b97a12a2cb..6b58087819 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -158,9 +158,6 @@ static NonTypeTemplateParmDecl *getDeducedParameterFromExpr(Expr *E) {
 /// \brief Determine whether two declaration pointers refer to the same
 /// declaration.
 static bool isSameDeclaration(Decl *X, Decl *Y) {
-  if (!X || !Y)
-    return !X && !Y;
-
   if (NamedDecl *NX = dyn_cast<NamedDecl>(X))
     X = NX->getUnderlyingDecl();
   if (NamedDecl *NY = dyn_cast<NamedDecl>(Y))
@@ -262,7 +259,27 @@ checkDeducedTemplateArguments(ASTContext &Context,
     // If we deduced two declarations, make sure they they refer to the
     // same declaration.
     if (Y.getKind() == TemplateArgument::Declaration &&
-        isSameDeclaration(X.getAsDecl(), Y.getAsDecl()))
+        isSameDeclaration(X.getAsDecl(), Y.getAsDecl()) &&
+        X.isDeclForReferenceParam() == Y.isDeclForReferenceParam())
+      return X;
+
+    // All other combinations are incompatible.
+    return DeducedTemplateArgument();
+
+  case TemplateArgument::NullPtr:
+    // If we deduced a null pointer and a dependent expression, keep the
+    // null pointer.
+    if (Y.getKind() == TemplateArgument::Expression)
+      return X;
+
+    // If we deduced a null pointer and an integral constant, keep the
+    // integral constant.
+    if (Y.getKind() == TemplateArgument::Integral)
+      return Y;
+
+    // If we deduced two null pointers, make sure they have the same type.
+    if (Y.getKind() == TemplateArgument::NullPtr &&
+        Context.hasSameType(X.getNullPtrType(), Y.getNullPtrType()))
       return X;
 
     // All other combinations are incompatible.
@@ -356,13 +373,15 @@ DeduceNonTypeTemplateArgument(Sema &S,
 static Sema::TemplateDeductionResult
 DeduceNonTypeTemplateArgument(Sema &S,
                               NonTypeTemplateParmDecl *NTTP,
-                              Decl *D,
+                              ValueDecl *D,
                               TemplateDeductionInfo &Info,
                     SmallVectorImpl<DeducedTemplateArgument> &Deduced) {
   assert(NTTP->getDepth() == 0 &&
          "Cannot deduce non-type template argument with depth > 0");
 
-  DeducedTemplateArgument NewDeduced(D? D->getCanonicalDecl() : 0);
+  D = D ? cast<ValueDecl>(D->getCanonicalDecl()) : 0;
+  TemplateArgument New(D, NTTP->getType()->isReferenceType());
+  DeducedTemplateArgument NewDeduced(New);
   DeducedTemplateArgument Result = checkDeducedTemplateArguments(S.Context,
                                                      Deduced[NTTP->getIndex()],
                                                                  NewDeduced);
@@ -615,7 +634,7 @@ FinishArgumentPackDeduction(Sema &S,
 
     if (NewlyDeducedPacks[I].empty()) {
       // If we deduced an empty argument pack, create it now.
-      NewPack = DeducedTemplateArgument(TemplateArgument(0, 0));
+      NewPack = DeducedTemplateArgument(TemplateArgument::getEmptyPack());
     } else {
       TemplateArgument *ArgumentPack
         = new (S.Context) TemplateArgument [NewlyDeducedPacks[I].size()];
@@ -1599,7 +1618,17 @@ DeduceTemplateArguments(Sema &S,
 
   case TemplateArgument::Declaration:
     if (Arg.getKind() == TemplateArgument::Declaration &&
-        isSameDeclaration(Param.getAsDecl(), Arg.getAsDecl()))
+        isSameDeclaration(Param.getAsDecl(), Arg.getAsDecl()) &&
+        Param.isDeclForReferenceParam() == Arg.isDeclForReferenceParam())
+      return Sema::TDK_Success;
+
+    Info.FirstArg = Param;
+    Info.SecondArg = Arg;
+    return Sema::TDK_NonDeducedMismatch;
+
+  case TemplateArgument::NullPtr:
+    if (Arg.getKind() == TemplateArgument::NullPtr &&
+        S.Context.hasSameType(Param.getNullPtrType(), Arg.getNullPtrType()))
       return Sema::TDK_Success;
 
     Info.FirstArg = Param;
@@ -1870,7 +1899,11 @@ static bool isSameTemplateArg(ASTContext &Context,
              Context.getCanonicalType(Y.getAsType());
 
     case TemplateArgument::Declaration:
-      return isSameDeclaration(X.getAsDecl(), Y.getAsDecl());
+      return isSameDeclaration(X.getAsDecl(), Y.getAsDecl()) &&
+             X.isDeclForReferenceParam() == Y.isDeclForReferenceParam();
+
+    case TemplateArgument::NullPtr:
+      return Context.hasSameType(X.getNullPtrType(), Y.getNullPtrType());
 
     case TemplateArgument::Template:
     case TemplateArgument::TemplateExpansion:
@@ -1940,6 +1973,14 @@ getTrivialTemplateArgumentLoc(Sema &S,
     return TemplateArgumentLoc(TemplateArgument(E), E);
   }
 
+  case TemplateArgument::NullPtr: {
+    Expr *E
+      = S.BuildExpressionFromDeclTemplateArgument(Arg, NTTPType, Loc)
+          .takeAs<Expr>();
+    return TemplateArgumentLoc(TemplateArgument(NTTPType, /*isNullPtr*/true),
+                               E);
+  }
+
   case TemplateArgument::Integral: {
     Expr *E
       = S.BuildExpressionFromIntegralTemplateArgument(Arg, Loc).takeAs<Expr>();
@@ -2613,7 +2654,7 @@ Sema::FinishTemplateArgumentDeduction(FunctionTemplateDecl *FunctionTemplate,
           == Param)
         Builder.push_back(TemplateArgument(ExplicitArgs, NumExplicitArgs));
       else
-        Builder.push_back(TemplateArgument(0, 0));
+        Builder.push_back(TemplateArgument::getEmptyPack());
 
       continue;
     }
@@ -4510,6 +4551,11 @@ MarkUsedTemplateParameters(ASTContext &Ctx,
   case TemplateArgument::Declaration:
     break;
 
+  case TemplateArgument::NullPtr:
+    MarkUsedTemplateParameters(Ctx, TemplateArg.getNullPtrType(), OnlyDeduced,
+                               Depth, Used);
+    break;
+
   case TemplateArgument::Type:
     MarkUsedTemplateParameters(Ctx, TemplateArg.getAsType(), OnlyDeduced,
                                Depth, Used);
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index c44794e3e1..621f92bb67 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1174,10 +1174,11 @@ ExprResult TemplateInstantiator::transformNonTypeTemplateParmRef(
     result = SemaRef.Owned(argExpr);
     type = argExpr->getType();
 
-  } else if (arg.getKind() == TemplateArgument::Declaration) {
+  } else if (arg.getKind() == TemplateArgument::Declaration ||
+             arg.getKind() == TemplateArgument::NullPtr) {
     ValueDecl *VD;
-    if (Decl *D = arg.getAsDecl()) {
-      VD = cast<ValueDecl>(D);
+    if (arg.getKind() == TemplateArgument::Declaration) {
+      VD = cast<ValueDecl>(arg.getAsDecl());
 
       // Find the instantiation of the template argument.  This is
       // required for nested templates.
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index d3839c5a5c..975895dc8e 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -2464,6 +2464,7 @@ public:
     case TemplateArgument::Declaration:
     case TemplateArgument::Pack:
     case TemplateArgument::TemplateExpansion:
+    case TemplateArgument::NullPtr:
       llvm_unreachable("Pack expansion pattern has no parameter packs");
 
     case TemplateArgument::Type:
@@ -2946,6 +2947,7 @@ void TreeTransform<Derived>::InventTemplateArgumentLoc(
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
   case TemplateArgument::Pack:
+  case TemplateArgument::NullPtr:
     Output = TemplateArgumentLoc(Arg, TemplateArgumentLocInfo());
     break;
   }
@@ -2961,7 +2963,8 @@ bool TreeTransform<Derived>::TransformTemplateArgument(
   case TemplateArgument::Integral:
   case TemplateArgument::Pack:
   case TemplateArgument::Declaration:
-    llvm_unreachable("Cannot transform");
+  case TemplateArgument::NullPtr:
+    llvm_unreachable("Unexpected TemplateArgument");
 
   case TemplateArgument::Type: {
     TypeSourceInfo *DI = Input.getTypeSourceInfo();
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index c57e933668..17296685c4 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -4555,7 +4555,9 @@ ASTReader::GetTemplateArgumentLocInfo(ModuleFile &F,
   case TemplateArgument::Null:
   case TemplateArgument::Integral:
   case TemplateArgument::Declaration:
+  case TemplateArgument::NullPtr:
   case TemplateArgument::Pack:
+    // FIXME: Is this right?
     return TemplateArgumentLocInfo();
   }
   llvm_unreachable("unexpected template argument loc");
@@ -5944,8 +5946,13 @@ ASTReader::ReadTemplateArgument(ModuleFile &F,
     return TemplateArgument();
   case TemplateArgument::Type:
     return TemplateArgument(readType(F, Record, Idx));
-  case TemplateArgument::Declaration:
-    return TemplateArgument(ReadDecl(F, Record, Idx));
+  case TemplateArgument::Declaration: {
+    ValueDecl *D = ReadDeclAs<ValueDecl>(F, Record, Idx);
+    bool ForReferenceParam = Record[Idx++];
+    return TemplateArgument(D, ForReferenceParam);
+  }
+  case TemplateArgument::NullPtr:
+    return TemplateArgument(readType(F, Record, Idx), /*isNullPtr*/true);
   case TemplateArgument::Integral: {
     llvm::APSInt Value = ReadAPSInt(Record, Idx);
     QualType T = readType(F, Record, Idx);
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 5ec5936f64..4b2a8a7c79 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -3791,7 +3791,9 @@ void ASTWriter::AddTemplateArgumentLocInfo(TemplateArgument::ArgKind Kind,
   case TemplateArgument::Null:
   case TemplateArgument::Integral:
   case TemplateArgument::Declaration:
+  case TemplateArgument::NullPtr:
   case TemplateArgument::Pack:
+    // FIXME: Is this right?
     break;
   }
 }
@@ -4208,6 +4210,10 @@ void ASTWriter::AddTemplateArgument(const TemplateArgument &Arg,
     break;
   case TemplateArgument::Declaration:
     AddDeclRef(Arg.getAsDecl(), Record);
+    Record.push_back(Arg.isDeclForReferenceParam());
+    break;
+  case TemplateArgument::NullPtr:
+    AddTypeRef(Arg.getNullPtrType(), Record);
     break;
   case TemplateArgument::Integral:
     AddAPSInt(Arg.getAsIntegral(), Record);
diff --git a/test/CodeGenCXX/mangle-nullptr-arg.cpp b/test/CodeGenCXX/mangle-nullptr-arg.cpp
index 393de0b0ec..07bf52fc90 100644
--- a/test/CodeGenCXX/mangle-nullptr-arg.cpp
+++ b/test/CodeGenCXX/mangle-nullptr-arg.cpp
@@ -11,3 +11,6 @@ template<int X::*pm> struct PM {};
 // CHECK: define void @_Z5test22PMILM1Xi0EE
 void test2(PM<nullptr>) { }
 
+// CHECK: define void @_Z5test316DependentTypePtrIPiLS0_0EE
+template<typename T, T x> struct DependentTypePtr {};
+void test3(DependentTypePtr<int*,nullptr>) { }
diff --git a/test/CodeGenCXX/mangle-template.cpp b/test/CodeGenCXX/mangle-template.cpp
index 488f6f3bb1..15a85c7bd2 100644
--- a/test/CodeGenCXX/mangle-template.cpp
+++ b/test/CodeGenCXX/mangle-template.cpp
@@ -162,11 +162,11 @@ namespace test12 {
   void use() {
     // CHECK: define internal void @_ZN6test124testIFivEXadL_ZNS_L1fEvEEEEvv(
     test<int(), &f>();
-    // CHECK: define internal void @_ZN6test124testIRFivEXadL_ZNS_L1fEvEEEEvv(
+    // CHECK: define internal void @_ZN6test124testIRFivELZNS_L1fEvEEEvv(
     test<int(&)(), f>();
     // CHECK: define internal void @_ZN6test124testIPKiXadL_ZNS_L1nEEEEEvv(
     test<const int*, &n>();
-    // CHECK: define internal void @_ZN6test124testIRKiXadL_ZNS_L1nEEEEEvv(
+    // CHECK: define internal void @_ZN6test124testIRKiLZNS_L1nEEEEvv(
     test<const int&, n>();
   }
 }
diff --git a/tools/libclang/CIndex.cpp b/tools/libclang/CIndex.cpp
index 6cf40fd7f7..2ca5f10271 100644
--- a/tools/libclang/CIndex.cpp
+++ b/tools/libclang/CIndex.cpp
@@ -1327,7 +1327,12 @@ bool CursorVisitor::VisitTemplateArgumentLoc(const TemplateArgumentLoc &TAL) {
     if (Expr *E = TAL.getSourceDeclExpression())
       return Visit(MakeCXCursor(E, StmtParent, TU, RegionOfInterest));
     return false;
-      
+
+  case TemplateArgument::NullPtr:
+    if (Expr *E = TAL.getSourceNullPtrExpression())
+      return Visit(MakeCXCursor(E, StmtParent, TU, RegionOfInterest));
+    return false;
+
   case TemplateArgument::Expression:
     if (Expr *E = TAL.getSourceExpression())
       return Visit(MakeCXCursor(E, StmtParent, TU, RegionOfInterest));
diff --git a/tools/libclang/CIndexUSRs.cpp b/tools/libclang/CIndexUSRs.cpp
index 4858276f67..19b3f263a4 100644
--- a/tools/libclang/CIndexUSRs.cpp
+++ b/tools/libclang/CIndexUSRs.cpp
@@ -728,10 +728,12 @@ void USRGenerator::VisitTemplateArgument(const TemplateArgument &Arg) {
     break;
 
   case TemplateArgument::Declaration:
-    if (Decl *D = Arg.getAsDecl())
-      Visit(D);
+    Visit(Arg.getAsDecl());
     break;
-      
+
+  case TemplateArgument::NullPtr:
+    break;
+
   case TemplateArgument::TemplateExpansion:
     Out << 'P'; // pack expansion of...
     // Fall through
diff --git a/tools/libclang/RecursiveASTVisitor.h b/tools/libclang/RecursiveASTVisitor.h
index 571bb82082..4844204a5f 100644
--- a/tools/libclang/RecursiveASTVisitor.h
+++ b/tools/libclang/RecursiveASTVisitor.h
@@ -657,6 +657,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgument(
   case TemplateArgument::Null:
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
+  case TemplateArgument::NullPtr:
     return true;
 
   case TemplateArgument::Type:
@@ -689,6 +690,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgumentLoc(
   case TemplateArgument::Null:
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
+  case TemplateArgument::NullPtr:
     return true;
 
   case TemplateArgument::Type: {