Index: include/clang/AST/ASTContext.h
===================================================================
--- include/clang/AST/ASTContext.h
+++ include/clang/AST/ASTContext.h
@@ -168,6 +168,7 @@
   mutable llvm::FoldingSet<DependentAddressSpaceType>
       DependentAddressSpaceTypes;
   mutable llvm::FoldingSet<VectorType> VectorTypes;
+  mutable llvm::FoldingSet<DependentVectorType> DependentVectorTypes;
   mutable llvm::FoldingSet<FunctionNoProtoType> FunctionNoProtoTypes;
   mutable llvm::ContextualFoldingSet<FunctionProtoType, ASTContext&>
     FunctionProtoTypes;
@@ -1321,6 +1322,11 @@
   /// \pre \p VectorType must be a built-in type.
   QualType getVectorType(QualType VectorType, unsigned NumElts,
                          VectorType::VectorKind VecKind) const;
+  /// Return the unique reference to the type for a dependently sized vector of
+  /// the specified element type.
+  QualType getDependentVectorType(QualType VectorType, Expr *SizeExpr,
+                                  SourceLocation AttrLoc,
+                                  VectorType::VectorKind VecKind) const;
 
   /// Return the unique reference to an extended vector type
   /// of the specified element type and size.
Index: include/clang/AST/RecursiveASTVisitor.h
===================================================================
--- include/clang/AST/RecursiveASTVisitor.h
+++ include/clang/AST/RecursiveASTVisitor.h
@@ -993,6 +993,12 @@
   TRY_TO(TraverseType(T->getPointeeType()));
 })
 
+DEF_TRAVERSE_TYPE(DependentVectorType, {
+  if (T->getSizeExpr())
+    TRY_TO(TraverseStmt(T->getSizeExpr()));
+  TRY_TO(TraverseType(T->getElementType()));
+})
+
 DEF_TRAVERSE_TYPE(DependentSizedExtVectorType, {
   if (T->getSizeExpr())
     TRY_TO(TraverseStmt(T->getSizeExpr()));
@@ -1221,6 +1227,12 @@
   TRY_TO(TraverseType(TL.getTypePtr()->getElementType()));
 })
 
+DEF_TRAVERSE_TYPELOC(DependentVectorType, {
+  if (TL.getTypePtr()->getSizeExpr())
+    TRY_TO(TraverseStmt(const_cast<Expr*>(TL.getTypePtr()->getSizeExpr())));
+  TRY_TO(TraverseType(TL.getTypePtr()->getElementType()));
+})
+
 // FIXME: size and attributes
 // FIXME: base VectorTypeLoc is unfinished
 DEF_TRAVERSE_TYPELOC(ExtVectorType, {
Index: include/clang/AST/Type.h
===================================================================
--- include/clang/AST/Type.h
+++ include/clang/AST/Type.h
@@ -1590,6 +1590,7 @@
 
   class VectorTypeBitfields {
     friend class VectorType;
+    friend class DependentVectorType;
 
     unsigned : NumTypeBits;
 
@@ -3079,6 +3080,52 @@
   }
 };
 
+/// Represents a vector type where either the type or size is dependent.
+////
+/// For example:
+/// \code
+/// template<typename T, int Size>
+/// class vector {
+///   typedef T __attribute__((vector_size(Size))) type;
+/// }
+/// \endcode
+class DependentVectorType : public Type, public llvm::FoldingSetNode {
+  friend class ASTContext;
+
+  const ASTContext &Context;
+  QualType ElementType;
+  Expr *SizeExpr;
+  SourceLocation Loc;
+
+  DependentVectorType(const ASTContext &Context, QualType ElementType,
+                           QualType CanonType, Expr *SizeExpr,
+                           SourceLocation Loc, VectorType::VectorKind vecKind);
+
+public:
+  const Expr *getSizeExpr() const { return SizeExpr; }
+  Expr *getSizeExpr() { return SizeExpr; }
+  QualType getElementType() const { return ElementType; }
+  SourceLocation getAttributeLoc() const { return Loc; }
+  VectorType::VectorKind getVectorKind() const {
+    return VectorType::VectorKind(VectorTypeBits.VecKind);
+  }
+
+  bool isSugared() const { return false; }
+  QualType desugar() const { return QualType(this, 0); }
+
+  static bool classof(const Type *T) {
+    return T->getTypeClass() == DependentVector;
+  }
+
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    Profile(ID, Context, getElementType(), getSizeExpr(), getVectorKind());
+  }
+
+  static void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Context,
+                      QualType ElementType, const Expr *SizeExpr,
+                      VectorType::VectorKind VecKind);
+};
+
 /// ExtVectorType - Extended vector type. This type is created using
 /// __attribute__((ext_vector_type(n)), where "n" is the number of elements.
 /// Unlike vector_size, ext_vector_type is only allowed on typedef's. This
Index: include/clang/AST/TypeLoc.h
===================================================================
--- include/clang/AST/TypeLoc.h
+++ include/clang/AST/TypeLoc.h
@@ -1798,6 +1798,13 @@
                                                        VectorType> {
 };
 
+// FIXME: size expression and attribute locations (or keyword if we
+// ever fully support altivec syntax).
+class DependentVectorTypeLoc
+    : public InheritingConcreteTypeLoc<TypeSpecTypeLoc,
+                                       DependentVectorTypeLoc,
+                                       DependentVectorType> {};
+
 // FIXME: size expression and attribute locations.
 class ExtVectorTypeLoc : public InheritingConcreteTypeLoc<VectorTypeLoc,
                                                           ExtVectorTypeLoc,
Index: include/clang/AST/TypeNodes.def
===================================================================
--- include/clang/AST/TypeNodes.def
+++ include/clang/AST/TypeNodes.def
@@ -75,6 +75,7 @@
 DEPENDENT_TYPE(DependentSizedExtVector, Type)
 DEPENDENT_TYPE(DependentAddressSpace, Type)
 TYPE(Vector, Type)
+DEPENDENT_TYPE(DependentVector, Type)
 TYPE(ExtVector, VectorType)
 ABSTRACT_TYPE(Function, Type)
 TYPE(FunctionProto, FunctionType)
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -1377,6 +1377,7 @@
   QualType BuildArrayType(QualType T, ArrayType::ArraySizeModifier ASM,
                           Expr *ArraySize, unsigned Quals,
                           SourceRange Brackets, DeclarationName Entity);
+  QualType BuildVectorType(QualType T, Expr *VecSize, SourceLocation AttrLoc);
   QualType BuildExtVectorType(QualType T, Expr *ArraySize,
                               SourceLocation AttrLoc);
   QualType BuildAddressSpaceAttr(QualType &T, Expr *AddrSpace,
Index: include/clang/Serialization/ASTBitCodes.h
===================================================================
--- include/clang/Serialization/ASTBitCodes.h
+++ include/clang/Serialization/ASTBitCodes.h
@@ -1032,133 +1032,133 @@
     /// AST. Note that DeclCode values share this code space.
     enum TypeCode {
       /// An ExtQualType record.
-      TYPE_EXT_QUAL                 = 1,
+      TYPE_EXT_QUAL = 1,
 
       /// A ComplexType record.
-      TYPE_COMPLEX                  = 3,
+      TYPE_COMPLEX = 3,
 
       /// A PointerType record.
-      TYPE_POINTER                  = 4,
+      TYPE_POINTER = 4,
 
       /// A BlockPointerType record.
-      TYPE_BLOCK_POINTER            = 5,
+      TYPE_BLOCK_POINTER = 5,
 
       /// An LValueReferenceType record.
-      TYPE_LVALUE_REFERENCE         = 6,
+      TYPE_LVALUE_REFERENCE = 6,
 
       /// An RValueReferenceType record.
-      TYPE_RVALUE_REFERENCE         = 7,
+      TYPE_RVALUE_REFERENCE = 7,
 
       /// A MemberPointerType record.
-      TYPE_MEMBER_POINTER           = 8,
+      TYPE_MEMBER_POINTER = 8,
 
       /// A ConstantArrayType record.
-      TYPE_CONSTANT_ARRAY           = 9,
+      TYPE_CONSTANT_ARRAY = 9,
 
       /// An IncompleteArrayType record.
-      TYPE_INCOMPLETE_ARRAY         = 10,
+      TYPE_INCOMPLETE_ARRAY = 10,
 
       /// A VariableArrayType record.
-      TYPE_VARIABLE_ARRAY           = 11,
+      TYPE_VARIABLE_ARRAY = 11,
 
       /// A VectorType record.
-      TYPE_VECTOR                   = 12,
+      TYPE_VECTOR = 12,
 
       /// An ExtVectorType record.
-      TYPE_EXT_VECTOR               = 13,
+      TYPE_EXT_VECTOR = 13,
 
       /// A FunctionNoProtoType record.
-      TYPE_FUNCTION_NO_PROTO        = 14,
+      TYPE_FUNCTION_NO_PROTO = 14,
 
       /// A FunctionProtoType record.
-      TYPE_FUNCTION_PROTO           = 15,
+      TYPE_FUNCTION_PROTO = 15,
 
       /// A TypedefType record.
-      TYPE_TYPEDEF                  = 16,
+      TYPE_TYPEDEF = 16,
 
       /// A TypeOfExprType record.
-      TYPE_TYPEOF_EXPR              = 17,
+      TYPE_TYPEOF_EXPR = 17,
 
       /// A TypeOfType record.
-      TYPE_TYPEOF                   = 18,
+      TYPE_TYPEOF = 18,
 
       /// A RecordType record.
-      TYPE_RECORD                   = 19,
+      TYPE_RECORD = 19,
 
       /// An EnumType record.
-      TYPE_ENUM                     = 20,
+      TYPE_ENUM = 20,
 
       /// An ObjCInterfaceType record.
-      TYPE_OBJC_INTERFACE           = 21,
+      TYPE_OBJC_INTERFACE = 21,
 
       /// An ObjCObjectPointerType record.
-      TYPE_OBJC_OBJECT_POINTER      = 22,
+      TYPE_OBJC_OBJECT_POINTER = 22,
 
       /// a DecltypeType record.
-      TYPE_DECLTYPE                 = 23,
+      TYPE_DECLTYPE = 23,
 
       /// An ElaboratedType record.
-      TYPE_ELABORATED               = 24,
+      TYPE_ELABORATED = 24,
 
       /// A SubstTemplateTypeParmType record.
       TYPE_SUBST_TEMPLATE_TYPE_PARM = 25,
 
       /// An UnresolvedUsingType record.
-      TYPE_UNRESOLVED_USING         = 26,
+      TYPE_UNRESOLVED_USING = 26,
 
       /// An InjectedClassNameType record.
-      TYPE_INJECTED_CLASS_NAME      = 27,
+      TYPE_INJECTED_CLASS_NAME = 27,
 
       /// An ObjCObjectType record.
-      TYPE_OBJC_OBJECT              = 28,
+      TYPE_OBJC_OBJECT = 28,
 
       /// An TemplateTypeParmType record.
-      TYPE_TEMPLATE_TYPE_PARM       = 29,
+      TYPE_TEMPLATE_TYPE_PARM = 29,
 
       /// An TemplateSpecializationType record.
-      TYPE_TEMPLATE_SPECIALIZATION  = 30,
+      TYPE_TEMPLATE_SPECIALIZATION = 30,
 
       /// A DependentNameType record.
-      TYPE_DEPENDENT_NAME           = 31,
+      TYPE_DEPENDENT_NAME = 31,
 
       /// A DependentTemplateSpecializationType record.
       TYPE_DEPENDENT_TEMPLATE_SPECIALIZATION = 32,
 
       /// A DependentSizedArrayType record.
-      TYPE_DEPENDENT_SIZED_ARRAY    = 33,
+      TYPE_DEPENDENT_SIZED_ARRAY = 33,
 
       /// A ParenType record.
-      TYPE_PAREN                    = 34,
+      TYPE_PAREN = 34,
 
       /// A PackExpansionType record.
-      TYPE_PACK_EXPANSION           = 35,
+      TYPE_PACK_EXPANSION = 35,
 
       /// An AttributedType record.
-      TYPE_ATTRIBUTED               = 36,
+      TYPE_ATTRIBUTED = 36,
 
       /// A SubstTemplateTypeParmPackType record.
       TYPE_SUBST_TEMPLATE_TYPE_PARM_PACK = 37,
 
       /// A AutoType record.
-      TYPE_AUTO                  = 38,
+      TYPE_AUTO = 38,
 
       /// A UnaryTransformType record.
-      TYPE_UNARY_TRANSFORM       = 39,
+      TYPE_UNARY_TRANSFORM = 39,
 
       /// An AtomicType record.
-      TYPE_ATOMIC                = 40,
+      TYPE_ATOMIC = 40,
 
       /// A DecayedType record.
-      TYPE_DECAYED               = 41,
+      TYPE_DECAYED = 41,
 
       /// An AdjustedType record.
-      TYPE_ADJUSTED              = 42,
+      TYPE_ADJUSTED = 42,
 
       /// A PipeType record.
-      TYPE_PIPE                  = 43,
+      TYPE_PIPE = 43,
 
       /// An ObjCTypeParamType record.
-      TYPE_OBJC_TYPE_PARAM       = 44,
+      TYPE_OBJC_TYPE_PARAM = 44,
 
       /// A DeducedTemplateSpecializationType record.
       TYPE_DEDUCED_TEMPLATE_SPECIALIZATION = 45,
@@ -1167,7 +1167,10 @@
       TYPE_DEPENDENT_SIZED_EXT_VECTOR = 46,
 
       /// A DependentAddressSpaceType record.
-      TYPE_DEPENDENT_ADDRESS_SPACE = 47
+      TYPE_DEPENDENT_ADDRESS_SPACE = 47,
+
+      /// A dependentSizedVectorType record.
+      TYPE_DEPENDENT_SIZED_VECTOR = 48
     };
 
     /// The type IDs for special types constructed by semantic
Index: lib/AST/ASTContext.cpp
===================================================================
--- lib/AST/ASTContext.cpp
+++ lib/AST/ASTContext.cpp
@@ -3035,6 +3035,7 @@
   case Type::Builtin:
   case Type::Complex:
   case Type::Vector:
+  case Type::DependentVector:
   case Type::ExtVector:
   case Type::DependentSizedExtVector:
   case Type::DependentAddressSpace:
@@ -3313,6 +3314,45 @@
   return QualType(New, 0);
 }
 
+QualType
+ASTContext::getDependentVectorType(QualType VecType, Expr *SizeExpr,
+                                   SourceLocation AttrLoc,
+                                   VectorType::VectorKind VecKind) const {
+  llvm::FoldingSetNodeID ID;
+  DependentVectorType::Profile(ID, *this, getCanonicalType(VecType), SizeExpr,
+                               VecKind);
+  void *InsertPos = nullptr;
+  DependentVectorType *Canon =
+      DependentVectorTypes.FindNodeOrInsertPos(ID, InsertPos);
+  DependentVectorType *New;
+
+  if (Canon) {
+    New = new (*this, TypeAlignment) DependentVectorType(
+        *this, VecType, QualType(Canon, 0), SizeExpr, AttrLoc, VecKind);
+  } else {
+    QualType CanonVecTy = getCanonicalType(VecType);
+    if (CanonVecTy == VecType) {
+      New = new (*this, TypeAlignment) DependentVectorType(
+          *this, VecType, QualType(), SizeExpr, AttrLoc, VecKind);
+
+      DependentVectorType *CanonCheck =
+          DependentVectorTypes.FindNodeOrInsertPos(ID, InsertPos);
+      assert(!CanonCheck &&
+             "Dependent-sized vector_size canonical type broken");
+      (void)CanonCheck;
+      DependentVectorTypes.InsertNode(New, InsertPos);
+    } else {
+      QualType Canon = getDependentSizedExtVectorType(CanonVecTy, SizeExpr,
+                                                      SourceLocation());
+      New = new (*this, TypeAlignment) DependentVectorType(
+          *this, VecType, Canon, SizeExpr, AttrLoc, VecKind);
+    }
+  }
+
+  Types.push_back(New);
+  return QualType(New, 0);
+}
+
 /// getExtVectorType - Return the unique reference to an extended vector type of
 /// the specified element type and size. VectorType must be a built-in type.
 QualType
Index: lib/AST/ASTStructuralEquivalence.cpp
===================================================================
--- lib/AST/ASTStructuralEquivalence.cpp
+++ lib/AST/ASTStructuralEquivalence.cpp
@@ -51,7 +51,7 @@
 
 /// Determine structural equivalence of two expressions.
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
-                                     Expr *E1, Expr *E2) {
+                                     const Expr *E1, const Expr *E2) {
   if (!E1 || !E2)
     return E1 == E2;
 
@@ -408,6 +408,20 @@
     break;
   }
 
+  case Type::DependentVector: {
+    const auto *Vec1 = cast<DependentVectorType>(T1);
+    const auto *Vec2 = cast<DependentVectorType>(T2);
+    if (Vec1->getVectorKind() != Vec2->getVectorKind())
+      return false;
+    if (!IsStructurallyEquivalent(Context, Vec1->getSizeExpr(),
+                                  Vec2->getSizeExpr()))
+      return false;
+    if (!IsStructurallyEquivalent(Context, Vec1->getElementType(),
+                                  Vec2->getElementType()))
+      return false;
+    break;
+  }
+
   case Type::Vector:
   case Type::ExtVector: {
     const auto *Vec1 = cast<VectorType>(T1);
Index: lib/AST/ItaniumMangle.cpp
===================================================================
--- lib/AST/ItaniumMangle.cpp
+++ lib/AST/ItaniumMangle.cpp
@@ -539,7 +539,9 @@
   void mangleBareFunctionType(const FunctionProtoType *T, bool MangleReturnType,
                               const FunctionDecl *FD = nullptr);
   void mangleNeonVectorType(const VectorType *T);
+  void mangleNeonVectorType(const DependentVectorType *T);
   void mangleAArch64NeonVectorType(const VectorType *T);
+  void mangleAArch64NeonVectorType(const DependentVectorType *T);
 
   void mangleIntegerLiteral(QualType T, const llvm::APSInt &Value);
   void mangleMemberExprBase(const Expr *base, bool isArrow);
@@ -1930,6 +1932,7 @@
   case Type::VariableArray:
   case Type::DependentSizedArray:
   case Type::DependentAddressSpace:
+  case Type::DependentVector:
   case Type::DependentSizedExtVector:
   case Type::Vector:
   case Type::ExtVector:
@@ -3000,6 +3003,14 @@
   Out << BaseName << EltName;
 }
 
+void CXXNameMangler::mangleNeonVectorType(const DependentVectorType *T) {
+  DiagnosticsEngine &Diags = Context.getDiags();
+  unsigned DiagID = Diags.getCustomDiagID(
+      DiagnosticsEngine::Error,
+      "cannot mangle this dependent neon vector type yet");
+  Diags.Report(T->getAttributeLoc(), DiagID);
+}
+
 static StringRef mangleAArch64VectorBase(const BuiltinType *EltType) {
   switch (EltType->getKind()) {
   case BuiltinType::SChar:
@@ -3067,6 +3078,13 @@
       ("__" + EltName + "x" + Twine(T->getNumElements()) + "_t").str();
   Out << TypeName.length() << TypeName;
 }
+void CXXNameMangler::mangleAArch64NeonVectorType(const DependentVectorType *T) {
+  DiagnosticsEngine &Diags = Context.getDiags();
+  unsigned DiagID = Diags.getCustomDiagID(
+      DiagnosticsEngine::Error,
+      "cannot mangle this dependent neon vector type yet");
+  Diags.Report(T->getAttributeLoc(), DiagID);
+}
 
 // GNU extension: vector types
 // <type>                  ::= <vector-type>
@@ -3097,6 +3115,32 @@
   else
     mangleType(T->getElementType());
 }
+
+void CXXNameMangler::mangleType(const DependentVectorType *T) {
+  if ((T->getVectorKind() == VectorType::NeonVector ||
+       T->getVectorKind() == VectorType::NeonPolyVector)) {
+    llvm::Triple Target = getASTContext().getTargetInfo().getTriple();
+    llvm::Triple::ArchType Arch =
+        getASTContext().getTargetInfo().getTriple().getArch();
+    if ((Arch == llvm::Triple::aarch64 || Arch == llvm::Triple::aarch64_be) &&
+        !Target.isOSDarwin())
+      mangleAArch64NeonVectorType(T);
+    else
+      mangleNeonVectorType(T);
+    return;
+  }
+
+  Out << "Dv";
+  mangleExpression(T->getSizeExpr());
+  Out << '_';
+  if (T->getVectorKind() == VectorType::AltiVecPixel)
+    Out << 'p';
+  else if (T->getVectorKind() == VectorType::AltiVecBool)
+    Out << 'b';
+  else
+    mangleType(T->getElementType());
+}
+
 void CXXNameMangler::mangleType(const ExtVectorType *T) {
   mangleType(static_cast<const VectorType*>(T));
 }
Index: lib/AST/MicrosoftMangle.cpp
===================================================================
--- lib/AST/MicrosoftMangle.cpp
+++ lib/AST/MicrosoftMangle.cpp
@@ -2514,6 +2514,16 @@
                                          Qualifiers Quals, SourceRange Range) {
   mangleType(static_cast<const VectorType *>(T), Quals, Range);
 }
+
+void MicrosoftCXXNameMangler::mangleType(const DependentVectorType *T,
+                                         Qualifiers, SourceRange Range) {
+  DiagnosticsEngine &Diags = Context.getDiags();
+  unsigned DiagID = Diags.getCustomDiagID(
+      DiagnosticsEngine::Error,
+      "cannot mangle this dependent-sized vector type yet");
+  Diags.Report(Range.getBegin(), DiagID) << Range;
+}
+
 void MicrosoftCXXNameMangler::mangleType(const DependentSizedExtVectorType *T,
                                          Qualifiers, SourceRange Range) {
   DiagnosticsEngine &Diags = Context.getDiags();
Index: lib/AST/Type.cpp
===================================================================
--- lib/AST/Type.cpp
+++ lib/AST/Type.cpp
@@ -177,6 +177,27 @@
   E->Profile(ID, Context, true);
 }
 
+DependentVectorType::DependentVectorType(
+    const ASTContext &Context, QualType ElementType, QualType CanonType,
+    Expr *SizeExpr, SourceLocation Loc, VectorType::VectorKind VecKind)
+    : Type(DependentVector, CanonType, /*Dependent=*/true,
+           /*InstantiationDependent=*/true,
+           ElementType->isVariablyModifiedType(),
+           ElementType->containsUnexpandedParameterPack() ||
+               (SizeExpr && SizeExpr->containsUnexpandedParameterPack())),
+      Context(Context), ElementType(ElementType), SizeExpr(SizeExpr), Loc(Loc) {
+  VectorTypeBits.VecKind = VecKind;
+}
+
+void DependentVectorType::Profile(llvm::FoldingSetNodeID &ID,
+                                  const ASTContext &Context,
+                                  QualType ElementType, const Expr *SizeExpr,
+                                  VectorType::VectorKind VecKind) {
+  ID.AddPointer(ElementType.getAsOpaquePtr());
+  ID.AddInteger(VecKind);
+  SizeExpr->Profile(ID, Context, true);
+}
+
 DependentSizedExtVectorType::DependentSizedExtVectorType(const
                                                          ASTContext &Context,
                                                          QualType ElementType,
@@ -3783,6 +3804,7 @@
   case Type::IncompleteArray:
   case Type::VariableArray:
   case Type::DependentSizedArray:
+  case Type::DependentVector:
   case Type::DependentSizedExtVector:
   case Type::Vector:
   case Type::ExtVector:
Index: lib/AST/TypePrinter.cpp
===================================================================
--- lib/AST/TypePrinter.cpp
+++ lib/AST/TypePrinter.cpp
@@ -242,6 +242,7 @@
     case Type::RValueReference:
     case Type::MemberPointer:
     case Type::DependentAddressSpace:
+    case Type::DependentVector:
     case Type::DependentSizedExtVector:
     case Type::Vector:
     case Type::ExtVector:
@@ -640,7 +641,55 @@
 
 void TypePrinter::printVectorAfter(const VectorType *T, raw_ostream &OS) {
   printAfter(T->getElementType(), OS);
-} 
+}
+
+void TypePrinter::printDependentVectorBefore(
+    const DependentVectorType *T, raw_ostream &OS) {
+  switch (T->getVectorKind()) {
+  case VectorType::AltiVecPixel:
+    OS << "__vector __pixel ";
+    break;
+  case VectorType::AltiVecBool:
+    OS << "__vector __bool ";
+    printBefore(T->getElementType(), OS);
+    break;
+  case VectorType::AltiVecVector:
+    OS << "__vector ";
+    printBefore(T->getElementType(), OS);
+    break;
+  case VectorType::NeonVector:
+    OS << "__attribute__((neon_vector_type(";
+    if (T->getSizeExpr())
+      T->getSizeExpr()->printPretty(OS, nullptr, Policy);
+    OS << "))) ";
+    printBefore(T->getElementType(), OS);
+    break;
+  case VectorType::NeonPolyVector:
+    OS << "__attribute__((neon_polyvector_type(";
+    if (T->getSizeExpr())
+      T->getSizeExpr()->printPretty(OS, nullptr, Policy);
+    OS << "))) ";
+    printBefore(T->getElementType(), OS);
+    break;
+  case VectorType::GenericVector: {
+    // FIXME: We prefer to print the size directly here, but have no way
+    // to get the size of the type.
+    OS << "__attribute__((__vector_size__(";
+    if (T->getSizeExpr())
+      T->getSizeExpr()->printPretty(OS, nullptr, Policy);
+    OS << " * sizeof(";
+    print(T->getElementType(), OS, StringRef());
+    OS << ")))) ";
+    printBefore(T->getElementType(), OS);
+    break;
+  }
+  }
+}
+
+void TypePrinter::printDependentVectorAfter(
+    const DependentVectorType *T, raw_ostream &OS) {
+  printAfter(T->getElementType(), OS);
+}
 
 void TypePrinter::printExtVectorBefore(const ExtVectorType *T,
                                        raw_ostream &OS) { 
Index: lib/Sema/SemaTemplate.cpp
===================================================================
--- lib/Sema/SemaTemplate.cpp
+++ lib/Sema/SemaTemplate.cpp
@@ -5341,6 +5341,11 @@
   return Visit(T->getElementType());
 }
 
+bool UnnamedLocalNoLinkageFinder::VisitDependentVectorType(
+    const DependentVectorType *T) {
+  return Visit(T->getElementType());
+}
+
 bool UnnamedLocalNoLinkageFinder::VisitExtVectorType(const ExtVectorType* T) {
   return Visit(T->getElementType());
 }
Index: lib/Sema/SemaTemplateDeduction.cpp
===================================================================
--- lib/Sema/SemaTemplateDeduction.cpp
+++ lib/Sema/SemaTemplateDeduction.cpp
@@ -1870,6 +1870,55 @@
       return Sema::TDK_NonDeducedMismatch;
     }
 
+    case Type::DependentVector: {
+      const auto *VectorParam = cast<DependentVectorType>(Param);
+
+      if (const auto *VectorArg = dyn_cast<VectorType>(Arg)) {
+        // Perform deduction on the element types.
+        if (Sema::TemplateDeductionResult Result =
+                DeduceTemplateArgumentsByTypeMatch(
+                    S, TemplateParams, VectorParam->getElementType(),
+                    VectorArg->getElementType(), Info, Deduced, TDF))
+          return Result;
+
+        // Perform deduction on the vector size, if we can.
+        NonTypeTemplateParmDecl *NTTP = getDeducedParameterFromExpr(
+            Info, const_cast<Expr *>(VectorParam->getSizeExpr()));
+        if (!NTTP)
+          return Sema::TDK_Success;
+
+        llvm::APSInt ArgSize(S.Context.getTypeSize(S.Context.IntTy), false);
+        ArgSize = VectorArg->getNumElements();
+        // Note that we use the "array bound" rules here; just like in that
+        // case, we don't have any particular type for the vector size, but
+        // we can provide one if necessary.
+        return DeduceNonTypeTemplateArgument(S, TemplateParams, NTTP, ArgSize,
+                                             S.Context.UnsignedIntTy, true,
+                                             Info, Deduced);
+      }
+
+      if (const auto *VectorArg = dyn_cast<DependentVectorType>(Arg)) {
+        // Perform deduction on the element types.
+        if (Sema::TemplateDeductionResult Result =
+                DeduceTemplateArgumentsByTypeMatch(
+                    S, TemplateParams, VectorParam->getElementType(),
+                    VectorArg->getElementType(), Info, Deduced, TDF))
+          return Result;
+
+        // Perform deduction on the vector size, if we can.
+        NonTypeTemplateParmDecl *NTTP = getDeducedParameterFromExpr(
+            Info, const_cast<Expr *>(VectorParam->getSizeExpr()));
+        if (!NTTP)
+          return Sema::TDK_Success;
+
+        return DeduceNonTypeTemplateArgument(
+            S, TemplateParams, NTTP,
+            const_cast<Expr *>(VectorArg->getSizeExpr()), Info, Deduced);
+      }
+
+      return Sema::TDK_NonDeducedMismatch;
+    }
+
     //     (clang extension)
     //
     //     T __attribute__(((ext_vector_type(N))))
@@ -5264,6 +5313,14 @@
                                OnlyDeduced, Depth, Used);
     break;
 
+  case Type::DependentVector: {
+    const auto *VecType = cast<DependentVectorType>(T);
+    MarkUsedTemplateParameters(Ctx, VecType->getElementType(), OnlyDeduced,
+                               Depth, Used);
+    MarkUsedTemplateParameters(Ctx, VecType->getSizeExpr(), OnlyDeduced, Depth,
+                               Used);
+    break;
+  }
   case Type::DependentSizedExtVector: {
     const DependentSizedExtVectorType *VecType
       = cast<DependentSizedExtVectorType>(T);
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -2243,6 +2243,58 @@
   return T;
 }
 
+QualType Sema::BuildVectorType(QualType CurType, Expr *SizeExpr,
+                               SourceLocation AttrLoc) {
+  // The base type must be integer (not Boolean or enumeration) or float, and
+  // can't already be a vector.
+  if (!CurType->isDependentType() &&
+      (!CurType->isBuiltinType() || CurType->isBooleanType() ||
+       (!CurType->isIntegerType() && !CurType->isRealFloatingType()))) {
+    Diag(AttrLoc, diag::err_attribute_invalid_vector_type) << CurType;
+    return QualType();
+  }
+
+  if (SizeExpr->isTypeDependent() || SizeExpr->isValueDependent())
+    return Context.getDependentVectorType(CurType, SizeExpr, AttrLoc,
+                                               VectorType::GenericVector);
+
+  llvm::APSInt VecSize(32);
+  if (!SizeExpr->isIntegerConstantExpr(VecSize, Context)) {
+    Diag(AttrLoc, diag::err_attribute_argument_type)
+        << "vector_size" << AANT_ArgumentIntegerConstant
+        << SizeExpr->getSourceRange();
+    return QualType();
+  }
+
+  if (CurType->isDependentType())
+    return Context.getDependentVectorType(CurType, SizeExpr, AttrLoc,
+                                               VectorType::GenericVector);
+
+  unsigned VectorSize = static_cast<unsigned>(VecSize.getZExtValue() * 8);
+  unsigned TypeSize = static_cast<unsigned>(Context.getTypeSize(CurType));
+
+  if (VectorSize == 0) {
+    Diag(AttrLoc, diag::err_attribute_zero_size) << SizeExpr->getSourceRange();
+    return QualType();
+  }
+
+  // vecSize is specified in bytes - convert to bits.
+  if (VectorSize % TypeSize) {
+    Diag(AttrLoc, diag::err_attribute_invalid_size)
+        << SizeExpr->getSourceRange();
+    return QualType();
+  }
+
+  if (VectorType::isVectorSizeTooLarge(VectorSize / TypeSize)) {
+    Diag(AttrLoc, diag::err_attribute_size_too_large)
+        << SizeExpr->getSourceRange();
+    return QualType();
+  }
+
+  return Context.getVectorType(CurType, VectorSize / TypeSize,
+                               VectorType::GenericVector);
+}
+
 /// Build an ext-vector type.
 ///
 /// Run the required checks for the extended vector type.
@@ -6857,52 +6909,30 @@
     Attr.setInvalid();
     return;
   }
-  Expr *sizeExpr = static_cast<Expr *>(Attr.getArgAsExpr(0));
-  llvm::APSInt vecSize(32);
-  if (sizeExpr->isTypeDependent() || sizeExpr->isValueDependent() ||
-      !sizeExpr->isIntegerConstantExpr(vecSize, S.Context)) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_argument_type)
-      << Attr.getName() << AANT_ArgumentIntegerConstant
-      << sizeExpr->getSourceRange();
-    Attr.setInvalid();
-    return;
-  }
-  // The base type must be integer (not Boolean or enumeration) or float, and
-  // can't already be a vector.
-  if (!CurType->isBuiltinType() || CurType->isBooleanType() ||
-      (!CurType->isIntegerType() && !CurType->isRealFloatingType())) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_invalid_vector_type) << CurType;
-    Attr.setInvalid();
-    return;
-  }
-  unsigned typeSize = static_cast<unsigned>(S.Context.getTypeSize(CurType));
-  // vecSize is specified in bytes - convert to bits.
-  unsigned vectorSize = static_cast<unsigned>(vecSize.getZExtValue() * 8);
 
-  // the vector size needs to be an integral multiple of the type size.
-  if (vectorSize % typeSize) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_invalid_size)
-      << sizeExpr->getSourceRange();
-    Attr.setInvalid();
-    return;
-  }
-  if (VectorType::isVectorSizeTooLarge(vectorSize / typeSize)) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_size_too_large)
-      << sizeExpr->getSourceRange();
-    Attr.setInvalid();
-    return;
-  }
-  if (vectorSize == 0) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_zero_size)
-      << sizeExpr->getSourceRange();
-    Attr.setInvalid();
-    return;
+  Expr *SizeExpr;
+  // Special case where the argument is a template id.
+  if (Attr.isArgIdent(0)) {
+    CXXScopeSpec SS;
+    SourceLocation TemplateKWLoc;
+    UnqualifiedId Id;
+    Id.setIdentifier(Attr.getArgAsIdent(0)->Ident, Attr.getLoc());
+
+    ExprResult Size = S.ActOnIdExpression(S.getCurScope(), SS, TemplateKWLoc,
+                                          Id, false, false);
+
+    if (Size.isInvalid())
+      return;
+    SizeExpr = Size.get();
+  } else {
+    SizeExpr = Attr.getArgAsExpr(0);
   }
 
-  // Success! Instantiate the vector type, the number of elements is > 0, and
-  // not required to be a power of 2, unlike GCC.
-  CurType = S.Context.getVectorType(CurType, vectorSize/typeSize,
-                                    VectorType::GenericVector);
+  QualType T = S.BuildVectorType(CurType, SizeExpr, Attr.getLoc());
+  if (!T.isNull())
+    CurType = T;
+  else
+    Attr.setInvalid();
 }
 
 /// Process the OpenCL-like ext_vector_type attribute when it occurs on
Index: lib/Sema/TreeTransform.h
===================================================================
--- lib/Sema/TreeTransform.h
+++ lib/Sema/TreeTransform.h
@@ -818,6 +818,15 @@
   QualType RebuildVectorType(QualType ElementType, unsigned NumElements,
                              VectorType::VectorKind VecKind);
 
+  /// Build a new potentially dependently-sized extended vector type
+  /// given the element type and number of elements.
+  ///
+  /// By default, performs semantic analysis when building the vector type.
+  /// Subclasses may override this routine to provide different behavior.
+  QualType RebuildDependentVectorType(QualType ElementType, Expr *SizeExpr,
+                                           SourceLocation AttributeLoc,
+                                           VectorType::VectorKind);
+
   /// Build a new extended vector type given the element type and
   /// number of elements.
   ///
@@ -4750,6 +4759,45 @@
   return Result;
 }
 
+template <typename Derived>
+QualType TreeTransform<Derived>::TransformDependentVectorType(
+    TypeLocBuilder &TLB, DependentVectorTypeLoc TL) {
+  const DependentVectorType *T = TL.getTypePtr();
+  QualType ElementType = getDerived().TransformType(T->getElementType());
+  if (ElementType.isNull())
+    return QualType();
+
+  EnterExpressionEvaluationContext Unevaluated(
+      SemaRef, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+
+  ExprResult Size =
+      getDerived().TransformExpr(const_cast<Expr *>(T->getSizeExpr()));
+  Size = SemaRef.ActOnConstantExpression(Size);
+  if (Size.isInvalid())
+    return QualType();
+
+  QualType Result = TL.getType();
+  if (getDerived().AlwaysRebuild() || ElementType != T->getElementType() ||
+      Size.get() != T->getSizeExpr()) {
+    Result = getDerived().RebuildDependentVectorType(
+        ElementType, Size.get(), T->getAttributeLoc(), T->getVectorKind());
+    if (Result.isNull())
+      return QualType();
+  }
+
+  // Result might be dependent or not.
+  if (isa<DependentVectorType>(Result)) {
+    DependentVectorTypeLoc NewTL =
+        TLB.push<DependentVectorTypeLoc>(Result);
+    NewTL.setNameLoc(TL.getNameLoc());
+  } else {
+    VectorTypeLoc NewTL = TLB.push<VectorTypeLoc>(Result);
+    NewTL.setNameLoc(TL.getNameLoc());
+  }
+
+  return Result;
+}
+
 template<typename Derived>
 QualType TreeTransform<Derived>::TransformDependentSizedExtVectorType(
                                       TypeLocBuilder &TLB,
@@ -12381,6 +12429,13 @@
   return SemaRef.Context.getVectorType(ElementType, NumElements, VecKind);
 }
 
+template <typename Derived>
+QualType TreeTransform<Derived>::RebuildDependentVectorType(
+    QualType ElementType, Expr *SizeExpr, SourceLocation AttributeLoc,
+    VectorType::VectorKind VecKind) {
+  return SemaRef.BuildVectorType(ElementType, SizeExpr, AttributeLoc);
+}
+
 template<typename Derived>
 QualType TreeTransform<Derived>::RebuildExtVectorType(QualType ElementType,
                                                       unsigned NumElements,
Index: lib/Serialization/ASTReader.cpp
===================================================================
--- lib/Serialization/ASTReader.cpp
+++ lib/Serialization/ASTReader.cpp
@@ -6369,6 +6369,17 @@
     return Context.getPipeType(ElementType, ReadOnly);
   }
 
+  case TYPE_DEPENDENT_SIZED_VECTOR: {
+    unsigned Idx = 0;
+    QualType ElementType = readType(*Loc.F, Record, Idx);
+    Expr *SizeExpr = ReadExpr(*Loc.F);
+    SourceLocation AttrLoc = ReadSourceLocation(*Loc.F, Record, Idx);
+    unsigned VecKind = Record[Idx];
+
+    return Context.getDependentVectorType(ElementType, SizeExpr, AttrLoc,
+                                               (VectorType::VectorKind)VecKind);
+  }
+
   case TYPE_DEPENDENT_SIZED_EXT_VECTOR: {
     unsigned Idx = 0;
 
@@ -6549,6 +6560,11 @@
   TL.setNameLoc(ReadSourceLocation());
 }
 
+void TypeLocReader::VisitDependentVectorTypeLoc(
+    DependentVectorTypeLoc TL) {
+  TL.setNameLoc(ReadSourceLocation());
+}
+
 void TypeLocReader::VisitExtVectorTypeLoc(ExtVectorTypeLoc TL) {
   TL.setNameLoc(ReadSourceLocation());
 }
Index: lib/Serialization/ASTWriter.cpp
===================================================================
--- lib/Serialization/ASTWriter.cpp
+++ lib/Serialization/ASTWriter.cpp
@@ -455,6 +455,14 @@
   Code = TYPE_DEPENDENT_SIZED_EXT_VECTOR;
 }
 
+void ASTTypeWriter::VisitDependentVectorType(const DependentVectorType *T) {
+  Record.AddTypeRef(T->getElementType());
+  Record.AddStmt(const_cast<Expr*>(T->getSizeExpr()));
+  Record.AddSourceLocation(T->getAttributeLoc());
+  Record.push_back(T->getVectorKind());
+  Code = TYPE_DEPENDENT_SIZED_VECTOR;
+}
+
 void
 ASTTypeWriter::VisitDependentAddressSpaceType(
     const DependentAddressSpaceType *T) {
@@ -676,6 +684,11 @@
   Record.AddSourceLocation(TL.getNameLoc());
 }
 
+void TypeLocWriter::VisitDependentVectorTypeLoc(
+    DependentVectorTypeLoc TL) {
+  Record.AddSourceLocation(TL.getNameLoc());
+}
+
 void TypeLocWriter::VisitExtVectorTypeLoc(ExtVectorTypeLoc TL) {
   Record.AddSourceLocation(TL.getNameLoc());
 }
Index: test/SemaCXX/vector.cpp
===================================================================
--- test/SemaCXX/vector.cpp
+++ test/SemaCXX/vector.cpp
@@ -291,3 +291,46 @@
 
 // PR12649
 typedef bool bad __attribute__((__vector_size__(16)));  // expected-error {{invalid vector element type 'bool'}}
+
+namespace Templates {
+template <typename Elt, unsigned Size>
+struct TemplateVectorType {
+  typedef Elt __attribute__((__vector_size__(Size))) type;
+};
+
+template <int N, typename T>
+struct PR15730 {
+  typedef T __attribute__((vector_size(N * sizeof(T)))) type;
+  typedef T __attribute__((vector_size(8192))) type2;
+  typedef T __attribute__((vector_size(3))) type3;
+};
+
+void Init() {
+  const TemplateVectorType<float, 32>::type Works = {};
+  const TemplateVectorType<int, 32>::type Works2 = {};
+  // expected-error@298 {{invalid vector element type 'bool'}}
+  // expected-note@+1 {{in instantiation of template class 'Templates::TemplateVectorType<bool, 32>' requested here}}
+  const TemplateVectorType<bool, 32>::type NoBool;
+  // expected-error@298 {{invalid vector element type 'int __attribute__((ext_vector_type(4)))' (vector of 4 'int' values)}}
+  // expected-note@+1 {{in instantiation of template class 'Templates::TemplateVectorType<int __attribute__((ext_vector_type(4))), 32>' requested here}}
+  const TemplateVectorType<vi4, 32>::type NoComplex;
+  // expected-error@298 {{vector size not an integral multiple of component size}}
+  // expected-note@+1 {{in instantiation of template class 'Templates::TemplateVectorType<int, 33>' requested here}}
+  const TemplateVectorType<int, 33>::type BadSize;
+  // expected-error@298 {{vector size too large}}
+  // expected-note@+1 {{in instantiation of template class 'Templates::TemplateVectorType<int, 8192>' requested here}}
+  const TemplateVectorType<int, 8192>::type TooLarge;
+  // expected-error@298 {{zero vector size}}
+  // expected-note@+1 {{in instantiation of template class 'Templates::TemplateVectorType<int, 0>' requested here}}
+  const TemplateVectorType<int, 0>::type Zero;
+
+  // expected-error@304 {{vector size too large}}
+  // expected-error@305 {{vector size not an integral multiple of component size}}
+  // expected-note@+1 {{in instantiation of template class 'Templates::PR15730<8, int>' requested here}}
+  const PR15730<8, int>::type PR15730_1 = {};
+  // expected-error@304 {{vector size too large}}
+  // expected-note@+1 {{in instantiation of template class 'Templates::PR15730<8, char>' requested here}}
+  const PR15730<8, char>::type2 PR15730_2 = {};
+}
+
+} // namespace Templates
Index: tools/libclang/CIndex.cpp
===================================================================
--- tools/libclang/CIndex.cpp
+++ tools/libclang/CIndex.cpp
@@ -1772,6 +1772,7 @@
 DEFAULT_TYPELOC_IMPL(VariableArray, ArrayType)
 DEFAULT_TYPELOC_IMPL(DependentSizedArray, ArrayType)
 DEFAULT_TYPELOC_IMPL(DependentAddressSpace, Type)
+DEFAULT_TYPELOC_IMPL(DependentVector, Type)
 DEFAULT_TYPELOC_IMPL(DependentSizedExtVector, Type)
 DEFAULT_TYPELOC_IMPL(Vector, Type)
 DEFAULT_TYPELOC_IMPL(ExtVector, VectorType)