[AST] Introduce a new DecayedType sugar node

The goal of this sugar node is to be able to look at an arbitrary
FunctionType and tell if any of the parameters were decayed from an
array or function type.  Ultimately this is necessary to implement
Microsoft's C++ name mangling scheme, which mangles decayed arrays
differently from normal pointers.

Reviewers: rsmith

Differential Revision: http://llvm-reviews.chandlerc.com/D1014

llvm-svn: 184763

24 files changed, 246 insertions, 27 deletions

diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index ebbf6c99e66..ae7a8f14d44 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -82,6 +82,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
   mutable llvm::FoldingSet<ExtQuals> ExtQualNodes;
   mutable llvm::FoldingSet<ComplexType> ComplexTypes;
   mutable llvm::FoldingSet<PointerType> PointerTypes;
+  mutable llvm::FoldingSet<DecayedType> DecayedTypes;
   mutable llvm::FoldingSet<BlockPointerType> BlockPointerTypes;
   mutable llvm::FoldingSet<LValueReferenceType> LValueReferenceTypes;
   mutable llvm::FoldingSet<RValueReferenceType> RValueReferenceTypes;
@@ -889,6 +890,14 @@ public:
     return CanQualType::CreateUnsafe(getPointerType((QualType) T));
   }
 
+  /// \brief Return the uniqued reference to the decayed version of the given
+  /// type.  Can only be called on array and function types which decay to
+  /// pointer types.
+  QualType getDecayedType(QualType T) const;
+  CanQualType getDecayedType(CanQualType T) const {
+    return CanQualType::CreateUnsafe(getDecayedType((QualType) T));
+  }
+
   /// \brief Return the uniqued reference to the atomic type for the specified
   /// type.
   QualType getAtomicType(QualType T) const;
diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index 5d94278e99d..25e37099f88 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -1337,11 +1337,7 @@ public:
     ParmVarDeclBits.HasInheritedDefaultArg = I;
   }
 
-  QualType getOriginalType() const {
-    if (getTypeSourceInfo())
-      return getTypeSourceInfo()->getType();
-    return getType();
-  }
+  QualType getOriginalType() const;
 
   /// \brief Determine whether this parameter is actually a function
   /// parameter pack.
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index 1072b97a14a..df71bffe850 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -847,6 +847,10 @@ DEF_TRAVERSE_TYPE(MemberPointerType, {
     TRY_TO(TraverseType(T->getPointeeType()));
   })
 
+DEF_TRAVERSE_TYPE(DecayedType, {
+    TRY_TO(TraverseType(T->getOriginalType()));
+  })
+
 DEF_TRAVERSE_TYPE(ConstantArrayType, {
     TRY_TO(TraverseType(T->getElementType()));
   })
@@ -1053,6 +1057,10 @@ DEF_TRAVERSE_TYPELOC(MemberPointerType, {
     TRY_TO(TraverseTypeLoc(TL.getPointeeLoc()));
   })
 
+DEF_TRAVERSE_TYPELOC(DecayedType, {
+    TRY_TO(TraverseTypeLoc(TL.getOriginalLoc()));
+  })
+
 template<typename Derived>
 bool RecursiveASTVisitor<Derived>::TraverseArrayTypeLocHelper(ArrayTypeLoc TL) {
   // This isn't available for ArrayType, but is for the ArrayTypeLoc.
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index bd2e18878ee..2566268a626 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -1991,6 +1991,44 @@ public:
   static bool classof(const Type *T) { return T->getTypeClass() == Pointer; }
 };
 
+/// \brief Represents a pointer type decayed from an array or function type.
+class DecayedType : public Type, public llvm::FoldingSetNode {
+  QualType OriginalType;
+  QualType DecayedPointer;
+
+  DecayedType(QualType OriginalType, QualType DecayedPointer,
+              QualType CanonicalPtr)
+      : Type(Decayed, CanonicalPtr, OriginalType->isDependentType(),
+             OriginalType->isInstantiationDependentType(),
+             OriginalType->isVariablyModifiedType(),
+             OriginalType->containsUnexpandedParameterPack()),
+        OriginalType(OriginalType), DecayedPointer(DecayedPointer) {
+    assert(isa<PointerType>(DecayedPointer));
+  }
+
+  friend class ASTContext;  // ASTContext creates these.
+
+public:
+  QualType getDecayedType() const { return DecayedPointer; }
+  QualType getOriginalType() const { return OriginalType; }
+
+  QualType getPointeeType() const {
+    return cast<PointerType>(DecayedPointer)->getPointeeType();
+  }
+
+  bool isSugared() const { return true; }
+  QualType desugar() const { return DecayedPointer; }
+
+  void Profile(llvm::FoldingSetNodeID &ID) {
+    Profile(ID, OriginalType);
+  }
+  static void Profile(llvm::FoldingSetNodeID &ID, QualType OriginalType) {
+    ID.AddPointer(OriginalType.getAsOpaquePtr());
+  }
+
+  static bool classof(const Type *T) { return T->getTypeClass() == Decayed; }
+};
+
 /// BlockPointerType - pointer to a block type.
 /// This type is to represent types syntactically represented as
 /// "void (^)(int)", etc. Pointee is required to always be a function type.
diff --git a/clang/include/clang/AST/TypeLoc.h b/clang/include/clang/AST/TypeLoc.h
index 1eb8835f4d6..a028a6f35c8 100644
--- a/clang/include/clang/AST/TypeLoc.h
+++ b/clang/include/clang/AST/TypeLoc.h
@@ -974,6 +974,40 @@ inline TypeLoc TypeLoc::IgnoreParens() const {
   return *this;
 }
 
+
+struct DecayedLocInfo { }; // Nothing.
+
+/// \brief Wrapper for source info for pointers decayed from arrays and
+/// funcitons.
+class DecayedTypeLoc : public ConcreteTypeLoc<UnqualTypeLoc, DecayedTypeLoc,
+                                              DecayedType, DecayedLocInfo> {
+public:
+  TypeLoc getOriginalLoc() const {
+    return getInnerTypeLoc();
+  }
+
+  void initializeLocal(ASTContext &Context, SourceLocation Loc) {
+    // do nothing
+  }
+
+  QualType getInnerType() const {
+    // The inner type is the undecayed type, since that's what we have source
+    // location information for.
+    return getTypePtr()->getOriginalType();
+  }
+
+  SourceRange getLocalSourceRange() const {
+    return SourceRange();
+  }
+
+  unsigned getLocalDataSize() const {
+    // sizeof(DecayedLocInfo) is 1, but we don't need its address to be unique
+    // anyway.  TypeLocBuilder can't handle data sizes of 1.
+    return 0;  // No data.
+  }
+};
+
+
 struct PointerLikeLocInfo {
   SourceLocation StarLoc;
 };
diff --git a/clang/include/clang/AST/TypeNodes.def b/clang/include/clang/AST/TypeNodes.def
index 840e07d94a0..a29ae231e94 100644
--- a/clang/include/clang/AST/TypeNodes.def
+++ b/clang/include/clang/AST/TypeNodes.def
@@ -81,6 +81,7 @@ TYPE(FunctionNoProto, FunctionType)
 DEPENDENT_TYPE(UnresolvedUsing, Type)
 NON_CANONICAL_TYPE(Paren, Type)
 NON_CANONICAL_TYPE(Typedef, Type)
+NON_CANONICAL_TYPE(Decayed, Type)
 NON_CANONICAL_UNLESS_DEPENDENT_TYPE(TypeOfExpr, Type)
 NON_CANONICAL_UNLESS_DEPENDENT_TYPE(TypeOf, Type)
 NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Decltype, Type)
diff --git a/clang/include/clang/Serialization/ASTBitCodes.h b/clang/include/clang/Serialization/ASTBitCodes.h
index 651b4a9df2d..ec05cc216bf 100644
--- a/clang/include/clang/Serialization/ASTBitCodes.h
+++ b/clang/include/clang/Serialization/ASTBitCodes.h
@@ -836,7 +836,9 @@ namespace clang {
       /// \brief A UnaryTransformType record.
       TYPE_UNARY_TRANSFORM       = 39,
       /// \brief An AtomicType record.
-      TYPE_ATOMIC                = 40
+      TYPE_ATOMIC                = 40,
+      /// \brief A DecayedType record.
+      TYPE_DECAYED               = 41
     };
 
     /// \brief The type IDs for special types constructed by semantic
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 70c933e7521..91059400761 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -1615,6 +1615,8 @@ ASTContext::getTypeInfoImpl(const Type *T) const {
   }
   case Type::ObjCObject:
     return getTypeInfo(cast<ObjCObjectType>(T)->getBaseType().getTypePtr());
+  case Type::Decayed:
+    return getTypeInfo(cast<DecayedType>(T)->getDecayedType().getTypePtr());
   case Type::ObjCInterface: {
     const ObjCInterfaceType *ObjCI = cast<ObjCInterfaceType>(T);
     const ASTRecordLayout &Layout = getASTObjCInterfaceLayout(ObjCI->getDecl());
@@ -2167,6 +2169,45 @@ QualType ASTContext::getPointerType(QualType T) const {
   return QualType(New, 0);
 }
 
+QualType ASTContext::getDecayedType(QualType T) const {
+  assert((T->isArrayType() || T->isFunctionType()) && "T does not decay");
+
+  llvm::FoldingSetNodeID ID;
+  DecayedType::Profile(ID, T);
+  void *InsertPos = 0;
+  if (DecayedType *DT = DecayedTypes.FindNodeOrInsertPos(ID, InsertPos))
+    return QualType(DT, 0);
+
+  QualType Decayed;
+
+  // C99 6.7.5.3p7:
+  //   A declaration of a parameter as "array of type" shall be
+  //   adjusted to "qualified pointer to type", where the type
+  //   qualifiers (if any) are those specified within the [ and ] of
+  //   the array type derivation.
+  if (T->isArrayType())
+    Decayed = getArrayDecayedType(T);
+
+  // C99 6.7.5.3p8:
+  //   A declaration of a parameter as "function returning type"
+  //   shall be adjusted to "pointer to function returning type", as
+  //   in 6.3.2.1.
+  if (T->isFunctionType())
+    Decayed = getPointerType(T);
+
+  QualType Canonical = getCanonicalType(Decayed);
+
+  // Get the new insert position for the node we care about.
+  DecayedType *NewIP = DecayedTypes.FindNodeOrInsertPos(ID, InsertPos);
+  assert(NewIP == 0 && "Shouldn't be in the map!"); (void)NewIP;
+
+  DecayedType *New =
+      new (*this, TypeAlignment) DecayedType(T, Decayed, Canonical);
+  Types.push_back(New);
+  DecayedTypes.InsertNode(New, InsertPos);
+  return QualType(New, 0);
+}
+
 /// getBlockPointerType - Return the uniqued reference to the type for
 /// a pointer to the specified block.
 QualType ASTContext::getBlockPointerType(QualType T) const {
@@ -4154,22 +4195,9 @@ const ArrayType *ASTContext::getAsArrayType(QualType T) const {
 }
 
 QualType ASTContext::getAdjustedParameterType(QualType T) const {
-  // C99 6.7.5.3p7:
-  //   A declaration of a parameter as "array of type" shall be
-  //   adjusted to "qualified pointer to type", where the type
-  //   qualifiers (if any) are those specified within the [ and ] of
-  //   the array type derivation.
-  if (T->isArrayType())
-    return getArrayDecayedType(T);
-  
-  // C99 6.7.5.3p8:
-  //   A declaration of a parameter as "function returning type"
-  //   shall be adjusted to "pointer to function returning type", as
-  //   in 6.3.2.1.
-  if (T->isFunctionType())
-    return getPointerType(T);
-  
-  return T;  
+  if (T->isArrayType() || T->isFunctionType())
+    return getDecayedType(T);
+  return T;
 }
 
 QualType ASTContext::getSignatureParameterType(QualType T) const {
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 41a67af64d6..84904580162 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -400,6 +400,13 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
       return false;
     break;
   
+  case Type::Decayed:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<DecayedType>(T1)->getPointeeType(),
+                                  cast<DecayedType>(T2)->getPointeeType()))
+      return false;
+    break;
+
   case Type::Pointer:
     if (!IsStructurallyEquivalent(Context,
                                   cast<PointerType>(T1)->getPointeeType(),
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index c799161e9b7..9702d032453 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1995,6 +1995,14 @@ ParmVarDecl *ParmVarDecl::Create(ASTContext &C, DeclContext *DC,
                              S, DefArg);
 }
 
+QualType ParmVarDecl::getOriginalType() const {
+  TypeSourceInfo *TSI = getTypeSourceInfo();
+  QualType T = TSI ? TSI->getType() : getType();
+  if (const DecayedType *DT = dyn_cast<DecayedType>(T))
+    return DT->getOriginalType();
+  return T;
+}
+
 ParmVarDecl *ParmVarDecl::CreateDeserialized(ASTContext &C, unsigned ID) {
   void *Mem = AllocateDeserializedDecl(C, ID, sizeof(ParmVarDecl));
   return new (Mem) ParmVarDecl(ParmVar, 0, SourceLocation(), SourceLocation(),
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 065465aa59e..7102bf349b2 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -828,6 +828,7 @@ void CXXNameMangler::mangleUnresolvedPrefix(NestedNameSpecifier *qualifier,
     switch (type->getTypeClass()) {
     case Type::Builtin:
     case Type::Complex:
+    case Type::Decayed:
     case Type::Pointer:
     case Type::BlockPointer:
     case Type::LValueReference:
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 2c439128f2d..d19c6a94508 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -201,6 +201,7 @@ bool TypePrinter::canPrefixQualifiers(const Type *T,
       NeedARCStrongQualifier = true;
       // Fall through
       
+    case Type::Decayed:
     case Type::Pointer:
     case Type::BlockPointer:
     case Type::LValueReference:
@@ -468,6 +469,14 @@ void TypePrinter::printVariableArrayAfter(const VariableArrayType *T,
   printAfter(T->getElementType(), OS);
 }
 
+void TypePrinter::printDecayedBefore(const DecayedType *T, raw_ostream &OS) {
+  // Print as though it's a pointer.
+  printBefore(T->getDecayedType(), OS);
+}
+void TypePrinter::printDecayedAfter(const DecayedType *T, raw_ostream &OS) {
+  printAfter(T->getDecayedType(), OS);
+}
+
 void TypePrinter::printDependentSizedArrayBefore(
                                                const DependentSizedArrayType *T, 
                                                raw_ostream &OS) {
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index e38327a9270..9d2b23ed185 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2069,6 +2069,10 @@ llvm::DIType CGDebugInfo::CreateTypeNode(QualType Ty, llvm::DIFile Unit,
     return CreateType(cast<ComplexType>(Ty));
   case Type::Pointer:
     return CreateType(cast<PointerType>(Ty), Unit);
+  case Type::Decayed:
+    // Decayed types are just pointers in LLVM and DWARF.
+    return CreateType(
+        cast<PointerType>(cast<DecayedType>(Ty)->getDecayedType()), Unit);
   case Type::BlockPointer:
     return CreateType(cast<BlockPointerType>(Ty), Unit);
   case Type::Typedef:
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 297fc655e44..c6b498cd586 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -1273,6 +1273,10 @@ void CodeGenFunction::EmitVariablyModifiedType(QualType type) {
     case Type::ObjCObjectPointer:
       llvm_unreachable("type class is never variably-modified!");
 
+    case Type::Decayed:
+      type = cast<DecayedType>(ty)->getPointeeType();
+      break;
+
     case Type::Pointer:
       type = cast<PointerType>(ty)->getPointeeType();
       break;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 27e8962f71b..1d2f39c0da3 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -4021,6 +4021,8 @@ bool Sema::GatherArgumentsForCall(SourceLocation CallLoc,
 
 static void DiagnoseCalleeStaticArrayParam(Sema &S, ParmVarDecl *PVD) {
   TypeLoc TL = PVD->getTypeSourceInfo()->getTypeLoc();
+  if (DecayedTypeLoc DTL = TL.getAs<DecayedTypeLoc>())
+    TL = DTL.getOriginalLoc();
   if (ArrayTypeLoc ATL = TL.getAs<ArrayTypeLoc>())
     S.Diag(PVD->getLocation(), diag::note_callee_static_array)
       << ATL.getLocalSourceRange();
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index f5a28966f86..e1f0739aea7 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -2844,10 +2844,6 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
           QualType ArgTy = Param->getType();
           assert(!ArgTy.isNull() && "Couldn't parse type?");
 
-          // Adjust the parameter type.
-          assert((ArgTy == Context.getAdjustedParameterType(ArgTy)) &&
-                 "Unadjusted type?");
-
           // Look for 'void'.  void is allowed only as a single argument to a
           // function with no other parameters (C99 6.7.5.3p10).  We record
           // int(void) as a FunctionProtoType with an empty argument list.
@@ -3577,6 +3573,9 @@ namespace {
     void VisitQualifiedTypeLoc(QualifiedTypeLoc TL) {
       llvm_unreachable("qualified type locs not expected here!");
     }
+    void VisitDecayedTypeLoc(DecayedTypeLoc TL) {
+      llvm_unreachable("decayed type locs not expected here!");
+    }
 
     void VisitAttributedTypeLoc(AttributedTypeLoc TL) {
       fillAttributedTypeLoc(TL, Chunk.getAttrs());
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 86624c580e5..9fbbe2cf1d5 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -3586,6 +3586,22 @@ QualType TreeTransform<Derived>::TransformComplexType(TypeLocBuilder &TLB,
 }
 
 template<typename Derived>
+QualType TreeTransform<Derived>::TransformDecayedType(TypeLocBuilder &TLB,
+                                                      DecayedTypeLoc TL) {
+  QualType OriginalType = getDerived().TransformType(TLB, TL.getOriginalLoc());
+  if (OriginalType.isNull())
+    return QualType();
+
+  QualType Result = TL.getType();
+  if (getDerived().AlwaysRebuild() ||
+      OriginalType != TL.getOriginalLoc().getType())
+    Result = SemaRef.Context.getDecayedType(OriginalType);
+  TLB.push<DecayedTypeLoc>(Result);
+  // Nothing to set for DecayedTypeLoc.
+  return Result;
+}
+
+template<typename Derived>
 QualType TreeTransform<Derived>::TransformPointerType(TypeLocBuilder &TLB,
                                                       PointerTypeLoc TL) {
   QualType PointeeType
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index f33e0e14cf6..052bef9e5be 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -4531,6 +4531,18 @@ QualType ASTReader::readTypeRecord(unsigned Index) {
     return Context.getPointerType(PointeeType);
   }
 
+  case TYPE_DECAYED: {
+    if (Record.size() != 1) {
+      Error("Incorrect encoding of decayed type");
+      return QualType();
+    }
+    QualType OriginalType = readType(*Loc.F, Record, Idx);
+    QualType DT = Context.getAdjustedParameterType(OriginalType);
+    if (!isa<DecayedType>(DT))
+      Error("Decayed type does not decay");
+    return DT;
+  }
+
   case TYPE_BLOCK_POINTER: {
     if (Record.size() != 1) {
       Error("Incorrect encoding of block pointer type");
@@ -4977,6 +4989,9 @@ void TypeLocReader::VisitComplexTypeLoc(ComplexTypeLoc TL) {
 void TypeLocReader::VisitPointerTypeLoc(PointerTypeLoc TL) {
   TL.setStarLoc(ReadSourceLocation(Record, Idx));
 }
+void TypeLocReader::VisitDecayedTypeLoc(DecayedTypeLoc TL) {
+  // nothing to do
+}
 void TypeLocReader::VisitBlockPointerTypeLoc(BlockPointerTypeLoc TL) {
   TL.setCaretLoc(ReadSourceLocation(Record, Idx));
 }
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 3654ec27f40..4a4128b4cfd 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -108,6 +108,11 @@ void ASTTypeWriter::VisitPointerType(const PointerType *T) {
   Code = TYPE_POINTER;
 }
 
+void ASTTypeWriter::VisitDecayedType(const DecayedType *T) {
+  Writer.AddTypeRef(T->getOriginalType(), Record);
+  Code = TYPE_DECAYED;
+}
+
 void ASTTypeWriter::VisitBlockPointerType(const BlockPointerType *T) {
   Writer.AddTypeRef(T->getPointeeType(), Record);
   Code = TYPE_BLOCK_POINTER;
@@ -447,6 +452,9 @@ void TypeLocWriter::VisitComplexTypeLoc(ComplexTypeLoc TL) {
 void TypeLocWriter::VisitPointerTypeLoc(PointerTypeLoc TL) {
   Writer.AddSourceLocation(TL.getStarLoc(), Record);
 }
+void TypeLocWriter::VisitDecayedTypeLoc(DecayedTypeLoc TL) {
+  // nothing to do
+}
 void TypeLocWriter::VisitBlockPointerTypeLoc(BlockPointerTypeLoc TL) {
   Writer.AddSourceLocation(TL.getCaretLoc(), Record);
 }
diff --git a/clang/test/Index/print-type.c b/clang/test/Index/print-type.c
index 4805f59f3fe..03f0b7c89ad 100644
--- a/clang/test/Index/print-type.c
+++ b/clang/test/Index/print-type.c
@@ -35,7 +35,7 @@ typedef int __attribute__((vector_size(16))) int4_t;
 // CHECK: DeclRefExpr=p:3:13 [type=int *] [typekind=Pointer] [isPOD=1]
 // CHECK: DeclRefExpr=z:3:33 [type=FooType] [typekind=Typedef] [canonicaltype=int] [canonicaltypekind=Int] [isPOD=1]
 // CHECK: ArraySubscriptExpr= [type=int] [typekind=Int] [isPOD=1]
-// CHECK: DeclRefExpr=arr:3:40 [type=int *] [typekind=Pointer] [isPOD=1]
+// CHECK: UnexposedExpr=arr:3:40 [type=int *] [typekind=Unexposed] [canonicaltype=int *] [canonicaltypekind=Pointer] [isPOD=1]
 // CHECK: IntegerLiteral= [type=int] [typekind=Int] [isPOD=1]
 // CHECK: TypedefDecl=OtherType:8:16 (Definition) [type=OtherType] [typekind=Typedef] [canonicaltype=double] [canonicaltypekind=Double] [isPOD=1]
 // CHECK: TypedefDecl=ArrayType:9:13 (Definition) [type=ArrayType] [typekind=Typedef] [canonicaltype=int [5]] [canonicaltypekind=ConstantArray] [isPOD=1]
diff --git a/clang/test/Sema/function.c b/clang/test/Sema/function.c
index bbf81a56cbb..81d303c27f6 100644
--- a/clang/test/Sema/function.c
+++ b/clang/test/Sema/function.c
@@ -103,3 +103,13 @@ int func_e(int x) {
   }
   return x + 3;
 }
+
+void decays(int a[3][3]);   // expected-note {{passing argument to parameter 'a' here}}
+void no_decay(int (*a)[3]); // expected-note {{passing argument to parameter 'a' here}}
+
+void t22(int *ptr, int (*array)[3]) {
+  decays(ptr);   // expected-warning {{incompatible pointer types passing 'int *' to parameter of type 'int (*)[3]'}}
+  no_decay(ptr); // expected-warning {{incompatible pointer types passing 'int *' to parameter of type 'int (*)[3]'}}
+  decays(array);
+  no_decay(array);
+}
diff --git a/clang/test/SemaCXX/function-type-qual.cpp b/clang/test/SemaCXX/function-type-qual.cpp
index ccb57472925..613ac9b200f 100644
--- a/clang/test/SemaCXX/function-type-qual.cpp
+++ b/clang/test/SemaCXX/function-type-qual.cpp
@@ -29,3 +29,11 @@ cfn C::*mpg;
 
 // Don't crash!
 void (PR14171)() const; // expected-error {{non-member function cannot have 'const' qualifier}}
+
+// Test template instantiation of decayed array types.  Not really related to
+// type quals.
+template <typename T> void arrayDecay(const T a[]) { }
+void instantiateArrayDecay() {
+  int a[1];
+  arrayDecay(a);
+}
diff --git a/clang/tools/libclang/CIndex.cpp b/clang/tools/libclang/CIndex.cpp
index 83b251968bc..09bb0eba8f5 100644
--- a/clang/tools/libclang/CIndex.cpp
+++ b/clang/tools/libclang/CIndex.cpp
@@ -1546,6 +1546,10 @@ bool CursorVisitor::VisitArrayTypeLoc(ArrayTypeLoc TL) {
   return false;
 }
 
+bool CursorVisitor::VisitDecayedTypeLoc(DecayedTypeLoc TL) {
+  return Visit(TL.getOriginalLoc());
+}
+
 bool CursorVisitor::VisitTemplateSpecializationTypeLoc(
                                              TemplateSpecializationTypeLoc TL) {
   // Visit the template name.
diff --git a/clang/tools/libclang/RecursiveASTVisitor.h b/clang/tools/libclang/RecursiveASTVisitor.h
index 0958d52e79c..17d70d6212e 100644
--- a/clang/tools/libclang/RecursiveASTVisitor.h
+++ b/clang/tools/libclang/RecursiveASTVisitor.h
@@ -786,6 +786,10 @@ DEF_TRAVERSE_TYPE(MemberPointerType, {
     TRY_TO(TraverseType(T->getPointeeType()));
   })
 
+DEF_TRAVERSE_TYPE(DecayedType, {
+    TRY_TO(TraverseType(T->getOriginalType()));
+  })
+
 DEF_TRAVERSE_TYPE(ConstantArrayType, {
     TRY_TO(TraverseType(T->getElementType()));
   })
@@ -992,6 +996,10 @@ DEF_TRAVERSE_TYPELOC(MemberPointerType, {
     TRY_TO(TraverseTypeLoc(TL.getPointeeLoc()));
   })
 
+DEF_TRAVERSE_TYPELOC(DecayedType, {
+    TRY_TO(TraverseTypeLoc(TL.getOriginalLoc()));
+  })
+
 template<typename Derived>
 bool RecursiveASTVisitor<Derived>::TraverseArrayTypeLocHelper(ArrayTypeLoc TL) {
   // This isn't available for ArrayType, but is for the ArrayTypeLoc.