MS ABI: Implement copy-ctor closures, finish implementing throw

This adds support for copy-constructor closures.  These are generated
when the C++ runtime has to call a copy-constructor with a particular
calling convention or with default arguments substituted in to the call.

Because the runtime has no mechanism to call the function with a
different calling convention or know-how to evaluate the default
arguments at run-time, we create a thunk which will do all the
appropriate work and package it in a way the runtime can use.

Differential Revision: http://reviews.llvm.org/D8225

llvm-svn: 231952

10 files changed, 296 insertions, 29 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 20d2aa68187..e92b33509f7 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -8210,6 +8210,18 @@ void ASTContext::addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
       cast<CXXConstructorDecl>(CD->getFirstDecl()));
 }
 
+void ASTContext::addDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                                 unsigned ParmIdx, Expr *DAE) {
+  ABI->addDefaultArgExprForConstructor(
+      cast<CXXConstructorDecl>(CD->getFirstDecl()), ParmIdx, DAE);
+}
+
+Expr *ASTContext::getDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                                  unsigned ParmIdx) {
+  return ABI->getDefaultArgExprForConstructor(
+      cast<CXXConstructorDecl>(CD->getFirstDecl()), ParmIdx);
+}
+
 void ASTContext::setParameterIndex(const ParmVarDecl *D, unsigned int index) {
   ParamIndices[D] = index;
 }
diff --git a/clang/lib/AST/CXXABI.h b/clang/lib/AST/CXXABI.h
index 62c96f901e6..dad226474fa 100644
--- a/clang/lib/AST/CXXABI.h
+++ b/clang/lib/AST/CXXABI.h
@@ -21,6 +21,7 @@ namespace clang {
 
 class ASTContext;
 class CXXConstructorDecl;
+class Expr;
 class MemberPointerType;
 class MangleNumberingContext;
 
@@ -50,6 +51,12 @@ public:
   /// Retrieves the mapping from class to copy constructor for this C++ ABI.
   virtual const CXXConstructorDecl *
   getCopyConstructorForExceptionObject(CXXRecordDecl *) = 0;
+
+  virtual void addDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                               unsigned ParmIdx, Expr *DAE) = 0;
+
+  virtual Expr *getDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                                unsigned ParmIdx) = 0;
 };
 
 /// Creates an instance of a C++ ABI class.
diff --git a/clang/lib/AST/ItaniumCXXABI.cpp b/clang/lib/AST/ItaniumCXXABI.cpp
index 13d4dbf1f46..74207820b3a 100644
--- a/clang/lib/AST/ItaniumCXXABI.cpp
+++ b/clang/lib/AST/ItaniumCXXABI.cpp
@@ -141,6 +141,14 @@ public:
   void addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
                                             CXXConstructorDecl *CD) override {}
 
+  void addDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                       unsigned ParmIdx, Expr *DAE) override {}
+
+  Expr *getDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                        unsigned ParmIdx) override {
+    return nullptr;
+  }
+
   MangleNumberingContext *createMangleNumberingContext() const override {
     return new ItaniumNumberingContext();
   }
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 13136b36236..f890719c209 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -3442,6 +3442,9 @@ void CXXNameMangler::mangleCXXCtorType(CXXCtorType T) {
   case Ctor_Comdat:
     Out << "C5";
     break;
+  case Ctor_DefaultClosure:
+  case Ctor_CopyingClosure:
+    llvm_unreachable("closure constructors don't exist for the Itanium ABI!");
   }
 }
 
diff --git a/clang/lib/AST/MicrosoftCXXABI.cpp b/clang/lib/AST/MicrosoftCXXABI.cpp
index 71b21bff77c..fb3beff4beb 100644
--- a/clang/lib/AST/MicrosoftCXXABI.cpp
+++ b/clang/lib/AST/MicrosoftCXXABI.cpp
@@ -64,6 +64,8 @@ public:
 class MicrosoftCXXABI : public CXXABI {
   ASTContext &Context;
   llvm::SmallDenseMap<CXXRecordDecl *, CXXConstructorDecl *> RecordToCopyCtor;
+  llvm::SmallDenseMap<std::pair<const CXXConstructorDecl *, unsigned>, Expr *>
+      CtorToDefaultArgExpr;
 
 public:
   MicrosoftCXXABI(ASTContext &Ctx) : Context(Ctx) { }
@@ -92,6 +94,16 @@ public:
       Layout.getNonVirtualSize() == PointerSize * 2;
   }
 
+  void addDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                       unsigned ParmIdx, Expr *DAE) override {
+    CtorToDefaultArgExpr[std::make_pair(CD, ParmIdx)] = DAE;
+  }
+
+  Expr *getDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
+                                        unsigned ParmIdx) override {
+    return CtorToDefaultArgExpr[std::make_pair(CD, ParmIdx)];
+  }
+
   const CXXConstructorDecl *
   getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
     return RecordToCopyCtor[RD];
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 073e798d11f..f56da26a09b 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -67,11 +67,15 @@ static const DeclContext *getEffectiveParentContext(const DeclContext *DC) {
   return getEffectiveDeclContext(cast<Decl>(DC));
 }
 
-static const FunctionDecl *getStructor(const FunctionDecl *fn) {
-  if (const FunctionTemplateDecl *ftd = fn->getPrimaryTemplate())
-    return ftd->getTemplatedDecl();
+static const FunctionDecl *getStructor(const NamedDecl *ND) {
+  if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(ND))
+    return FTD->getTemplatedDecl();
 
-  return fn;
+  const auto *FD = cast<FunctionDecl>(ND);
+  if (const auto *FTD = FD->getPrimaryTemplate())
+    return FTD->getTemplatedDecl();
+
+  return FD;
 }
 
 static bool isLambda(const NamedDecl *ND) {
@@ -115,7 +119,7 @@ public:
   void mangleCXXCatchableTypeArray(QualType T, uint32_t NumEntries,
                                    raw_ostream &Out) override;
   void mangleCXXCatchableType(QualType T, const CXXConstructorDecl *CD,
-                              uint32_t Size, uint32_t NVOffset,
+                              CXXCtorType CT, uint32_t Size, uint32_t NVOffset,
                               int32_t VBPtrOffset, uint32_t VBIndex,
                               raw_ostream &Out) override;
   void mangleCXXRTTI(QualType T, raw_ostream &Out) override;
@@ -224,6 +228,12 @@ public:
                          64) {}
 
   MicrosoftCXXNameMangler(MicrosoftMangleContextImpl &C, raw_ostream &Out_,
+                          const CXXConstructorDecl *D, CXXCtorType Type)
+      : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
+        PointersAre64Bit(C.getASTContext().getTargetInfo().getPointerWidth(0) ==
+                         64) {}
+
+  MicrosoftCXXNameMangler(MicrosoftMangleContextImpl &C, raw_ostream &Out_,
                           const CXXDestructorDecl *D, CXXDtorType Type)
       : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
         PointersAre64Bit(C.getASTContext().getTargetInfo().getPointerWidth(0) ==
@@ -284,6 +294,7 @@ private:
   void mangleDecayedArrayType(const ArrayType *T);
   void mangleArrayType(const ArrayType *T);
   void mangleFunctionClass(const FunctionDecl *FD);
+  void mangleCallingConvention(CallingConv CC);
   void mangleCallingConvention(const FunctionType *T);
   void mangleIntegerLiteral(const llvm::APSInt &Number, bool IsBoolean);
   void mangleExpression(const Expr *E);
@@ -770,12 +781,18 @@ void MicrosoftCXXNameMangler::mangleUnqualifiedName(const NamedDecl *ND,
       llvm_unreachable("Can't mangle Objective-C selector names here!");
 
     case DeclarationName::CXXConstructorName:
-      if (ND == Structor) {
-        assert(StructorType == Ctor_Complete &&
-               "Should never be asked to mangle a ctor other than complete");
+      if (Structor == getStructor(ND)) {
+        if (StructorType == Ctor_CopyingClosure) {
+          Out << "?_O";
+          return;
+        }
+        if (StructorType == Ctor_DefaultClosure) {
+          Out << "?_F";
+          return;
+        }
       }
       Out << "?0";
-      break;
+      return;
 
     case DeclarationName::CXXDestructorName:
       if (ND == Structor)
@@ -1566,12 +1583,22 @@ void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
   SourceRange Range;
   if (D) Range = D->getSourceRange();
 
-  bool IsStructor = false, HasThisQuals = ForceThisQuals;
+  bool IsStructor = false, HasThisQuals = ForceThisQuals, IsCtorClosure = false;
+  CallingConv CC = T->getCallConv();
   if (const CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(D)) {
     if (MD->isInstance())
       HasThisQuals = true;
-    if (isa<CXXConstructorDecl>(MD) || isa<CXXDestructorDecl>(MD))
+    if (isa<CXXDestructorDecl>(MD)) {
+      IsStructor = true;
+    } else if (isa<CXXConstructorDecl>(MD)) {
       IsStructor = true;
+      IsCtorClosure = (StructorType == Ctor_CopyingClosure ||
+                       StructorType == Ctor_DefaultClosure) &&
+                      getStructor(MD) == Structor;
+      if (IsCtorClosure)
+        CC = getASTContext().getDefaultCallingConvention(
+            /*IsVariadic=*/false, /*IsCXXMethod=*/true);
+    }
   }
 
   // If this is a C++ instance method, mangle the CVR qualifiers for the
@@ -1583,7 +1610,7 @@ void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
     mangleQualifiers(Quals, /*IsMember=*/false);
   }
 
-  mangleCallingConvention(T);
+  mangleCallingConvention(CC);
 
   // <return-type> ::= <type>
   //               ::= @ # structors (they have no declared return type)
@@ -1597,6 +1624,28 @@ void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
       Out << (PointersAre64Bit ? "PEAXI@Z" : "PAXI@Z");
       return;
     }
+    if (IsCtorClosure) {
+      // Default constructor closure and copy constructor closure both return
+      // void.
+      Out << 'X';
+
+      if (StructorType == Ctor_DefaultClosure) {
+        // Default constructor closure always has no arguments.
+        Out << 'X';
+      } else if (StructorType == Ctor_CopyingClosure) {
+        // Copy constructor closure always takes an unqualified reference.
+        mangleArgumentType(getASTContext().getLValueReferenceType(
+                               Proto->getParamType(0)
+                                   ->getAs<LValueReferenceType>()
+                                   ->getPointeeType(),
+                               /*SpelledAsLValue=*/true),
+                           Range);
+      } else {
+        llvm_unreachable("unexpected constructor closure!");
+      }
+      Out << "@Z";
+      return;
+    }
     Out << '@';
   } else {
     QualType ResultType = Proto->getReturnType();
@@ -1689,7 +1738,7 @@ void MicrosoftCXXNameMangler::mangleFunctionClass(const FunctionDecl *FD) {
   } else
     Out << 'Y';
 }
-void MicrosoftCXXNameMangler::mangleCallingConvention(const FunctionType *T) {
+void MicrosoftCXXNameMangler::mangleCallingConvention(CallingConv CC) {
   // <calling-convention> ::= A # __cdecl
   //                      ::= B # __export __cdecl
   //                      ::= C # __pascal
@@ -1706,7 +1755,7 @@ void MicrosoftCXXNameMangler::mangleCallingConvention(const FunctionType *T) {
   // that keyword. (It didn't actually export them, it just made them so
   // that they could be in a DLL and somebody from another module could call
   // them.)
-  CallingConv CC = T->getCallConv();
+
   switch (CC) {
     default:
       llvm_unreachable("Unsupported CC for mangling");
@@ -1720,6 +1769,9 @@ void MicrosoftCXXNameMangler::mangleCallingConvention(const FunctionType *T) {
     case CC_X86VectorCall: Out << 'Q'; break;
   }
 }
+void MicrosoftCXXNameMangler::mangleCallingConvention(const FunctionType *T) {
+  mangleCallingConvention(T->getCallConv());
+}
 void MicrosoftCXXNameMangler::mangleThrowSpecification(
                                                 const FunctionProtoType *FT) {
   // <throw-spec> ::= Z # throw(...) (default)
@@ -2310,8 +2362,9 @@ void MicrosoftMangleContextImpl::mangleCXXCatchableTypeArray(
 }
 
 void MicrosoftMangleContextImpl::mangleCXXCatchableType(
-    QualType T, const CXXConstructorDecl *CD, uint32_t Size, uint32_t NVOffset,
-    int32_t VBPtrOffset, uint32_t VBIndex, raw_ostream &Out) {
+    QualType T, const CXXConstructorDecl *CD, CXXCtorType CT, uint32_t Size,
+    uint32_t NVOffset, int32_t VBPtrOffset, uint32_t VBIndex,
+    raw_ostream &Out) {
   MicrosoftCXXNameMangler Mangler(*this, Out);
   Mangler.getStream() << "_CT";
 
@@ -2328,7 +2381,7 @@ void MicrosoftMangleContextImpl::mangleCXXCatchableType(
   llvm::SmallString<64> CopyCtorMangling;
   if (CD) {
     llvm::raw_svector_ostream Stream(CopyCtorMangling);
-    mangleCXXCtor(CD, Ctor_Complete, Stream);
+    mangleCXXCtor(CD, CT, Stream);
   }
   Mangler.getStream() << CopyCtorMangling.substr(1);
 
@@ -2411,7 +2464,7 @@ void MicrosoftMangleContextImpl::mangleTypeName(QualType T, raw_ostream &Out) {
 void MicrosoftMangleContextImpl::mangleCXXCtor(const CXXConstructorDecl *D,
                                                CXXCtorType Type,
                                                raw_ostream &Out) {
-  MicrosoftCXXNameMangler mangler(*this, Out);
+  MicrosoftCXXNameMangler mangler(*this, Out, D, Type);
   mangler.mangle(D);
 }
 
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 0060c769c71..67849642118 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -346,6 +346,22 @@ CodeGenTypes::arrangeMSMemberPointerThunk(const CXXMethodDecl *MD) {
                                  FTP->getExtInfo(), RequiredArgs(1));
 }
 
+const CGFunctionInfo &
+CodeGenTypes::arrangeMSCopyCtorClosure(const CXXConstructorDecl *CD) {
+  CanQual<FunctionProtoType> FTP = GetFormalType(CD);
+  SmallVector<CanQualType, 2> ArgTys;
+  const CXXRecordDecl *RD = CD->getParent();
+  ArgTys.push_back(GetThisType(Context, RD));
+  ArgTys.push_back(*FTP->param_type_begin());
+  if (RD->getNumVBases() > 0)
+    ArgTys.push_back(Context.IntTy);
+  CallingConv CC = Context.getDefaultCallingConvention(
+      /*IsVariadic=*/false, /*IsCXXMethod=*/true);
+  return arrangeLLVMFunctionInfo(Context.VoidTy, /*instanceMethod=*/true,
+                                 /*chainCall=*/false, ArgTys,
+                                 FunctionType::ExtInfo(CC), RequiredArgs::All);
+}
+
 /// Arrange a call as unto a free function, except possibly with an
 /// additional number of formal parameters considered required.
 static const CGFunctionInfo &
diff --git a/clang/lib/CodeGen/CodeGenTypes.h b/clang/lib/CodeGen/CodeGenTypes.h
index 64c5799ccec..f9cd3837fe9 100644
--- a/clang/lib/CodeGen/CodeGenTypes.h
+++ b/clang/lib/CodeGen/CodeGenTypes.h
@@ -82,6 +82,9 @@ inline StructorType getFromCtorType(CXXCtorType T) {
     return StructorType::Base;
   case Ctor_Comdat:
     llvm_unreachable("not expecting a COMDAT");
+  case Ctor_CopyingClosure:
+  case Ctor_DefaultClosure:
+    llvm_unreachable("not expecting a closure");
   }
   llvm_unreachable("not a CXXCtorType");
 }
@@ -261,6 +264,7 @@ public:
                                              const FunctionProtoType *type,
                                              RequiredArgs required);
   const CGFunctionInfo &arrangeMSMemberPointerThunk(const CXXMethodDecl *MD);
+  const CGFunctionInfo &arrangeMSCopyCtorClosure(const CXXConstructorDecl *CD);
 
   const CGFunctionInfo &arrangeFreeFunctionType(CanQual<FunctionProtoType> Ty);
   const CGFunctionInfo &arrangeFreeFunctionType(CanQual<FunctionNoProtoType> Ty);
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 7092e1803bd..1ec37f41311 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -635,6 +635,8 @@ public:
     return Fn;
   }
 
+  llvm::Function *getAddrOfCXXCopyCtorClosure(const CXXConstructorDecl *CD);
+
   llvm::Constant *getCatchableType(QualType T,
                                    uint32_t NVOffset = 0,
                                    int32_t VBPtrOffset = -1,
@@ -3220,6 +3222,103 @@ void MicrosoftCXXABI::emitCXXStructor(const CXXMethodDecl *MD,
   emitCXXDestructor(CGM, cast<CXXDestructorDecl>(MD), Type);
 }
 
+llvm::Function *
+MicrosoftCXXABI::getAddrOfCXXCopyCtorClosure(const CXXConstructorDecl *CD) {
+  // Calculate the mangled name.
+  SmallString<256> ThunkName;
+  llvm::raw_svector_ostream Out(ThunkName);
+  getMangleContext().mangleCXXCtor(CD, Ctor_CopyingClosure, Out);
+  Out.flush();
+
+  // If the thunk has been generated previously, just return it.
+  if (llvm::GlobalValue *GV = CGM.getModule().getNamedValue(ThunkName))
+    return cast<llvm::Function>(GV);
+
+  // Create the llvm::Function.
+  const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeMSCopyCtorClosure(CD);
+  llvm::FunctionType *ThunkTy = CGM.getTypes().GetFunctionType(FnInfo);
+  const CXXRecordDecl *RD = CD->getParent();
+  QualType RecordTy = getContext().getRecordType(RD);
+  llvm::Function *ThunkFn = llvm::Function::Create(
+      ThunkTy, getLinkageForRTTI(RecordTy), ThunkName.str(), &CGM.getModule());
+
+  // Start codegen.
+  CodeGenFunction CGF(CGM);
+  CGF.CurGD = GlobalDecl(CD, Ctor_Complete);
+
+  // Build FunctionArgs.
+  FunctionArgList FunctionArgs;
+
+  // A copy constructor always starts with a 'this' pointer as its first
+  // argument.
+  buildThisParam(CGF, FunctionArgs);
+
+  // Following the 'this' pointer is a reference to the source object that we
+  // are copying from.
+  ImplicitParamDecl SrcParam(
+      getContext(), nullptr, SourceLocation(), &getContext().Idents.get("src"),
+      getContext().getLValueReferenceType(RecordTy,
+                                          /*SpelledAsLValue=*/true));
+  FunctionArgs.push_back(&SrcParam);
+
+  // Copy constructors for classes which utilize virtual bases have an
+  // additional parameter which indicates whether or not it is being delegated
+  // to by a more derived constructor.
+  ImplicitParamDecl IsMostDerived(getContext(), nullptr, SourceLocation(),
+                                  &getContext().Idents.get("is_most_derived"),
+                                  getContext().IntTy);
+  // Only add the parameter to the list if thie class has virtual bases.
+  if (RD->getNumVBases() > 0)
+    FunctionArgs.push_back(&IsMostDerived);
+
+  // Start defining the function.
+  CGF.StartFunction(GlobalDecl(), FnInfo.getReturnType(), ThunkFn, FnInfo,
+                    FunctionArgs, CD->getLocation(), SourceLocation());
+  EmitThisParam(CGF);
+  llvm::Value *This = getThisValue(CGF);
+
+  llvm::Value *SrcVal =
+      CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(&SrcParam), "src");
+
+  CallArgList Args;
+
+  // Push the this ptr.
+  Args.add(RValue::get(This), CD->getThisType(getContext()));
+
+  // Push the src ptr.
+  Args.add(RValue::get(SrcVal), SrcParam.getType());
+
+  // Add the rest of the default arguments.
+  std::vector<Stmt *> ArgVec;
+  for (unsigned I = 1, E = CD->getNumParams(); I != E; ++I)
+    ArgVec.push_back(getContext().getDefaultArgExprForConstructor(CD, I));
+
+  CodeGenFunction::RunCleanupsScope Cleanups(CGF);
+
+  const auto *FPT = CD->getType()->castAs<FunctionProtoType>();
+  ConstExprIterator ArgBegin(ArgVec.data()), ArgEnd(&*ArgVec.end());
+  CGF.EmitCallArgs(Args, FPT, ArgBegin, ArgEnd, CD, 1);
+
+  // Insert any ABI-specific implicit constructor arguments.
+  unsigned ExtraArgs = addImplicitConstructorArgs(CGF, CD, Ctor_Complete,
+                                                  /*ForVirtualBase=*/false,
+                                                  /*Delegating=*/false, Args);
+
+  // Call the destructor with our arguments.
+  llvm::Value *CalleeFn = CGM.getAddrOfCXXStructor(CD, StructorType::Complete);
+  const CGFunctionInfo &CalleeInfo = CGM.getTypes().arrangeCXXConstructorCall(
+      Args, CD, Ctor_Complete, ExtraArgs);
+  CGF.EmitCall(CalleeInfo, CalleeFn, ReturnValueSlot(), Args, CD);
+
+  Cleanups.ForceCleanup();
+
+  // Emit the ret instruction, remove any temporary instructions created for the
+  // aid of CodeGen.
+  CGF.FinishFunction(SourceLocation());
+
+  return ThunkFn;
+}
+
 llvm::Constant *MicrosoftCXXABI::getCatchableType(QualType T,
                                                   uint32_t NVOffset,
                                                   int32_t VBPtrOffset,
@@ -3229,27 +3328,43 @@ llvm::Constant *MicrosoftCXXABI::getCatchableType(QualType T,
   CXXRecordDecl *RD = T->getAsCXXRecordDecl();
   const CXXConstructorDecl *CD =
       RD ? CGM.getContext().getCopyConstructorForExceptionObject(RD) : nullptr;
+  CXXCtorType CT = Ctor_Complete;
+  if (CD) {
+    CallingConv ExpectedCallingConv = getContext().getDefaultCallingConvention(
+        /*IsVariadic=*/false, /*IsCXXMethod=*/true);
+    CallingConv ActualCallingConv =
+        CD->getType()->getAs<FunctionProtoType>()->getCallConv();
+    if (ExpectedCallingConv != ActualCallingConv || CD->getNumParams() != 1)
+      CT = Ctor_CopyingClosure;
+  }
+
   uint32_t Size = getContext().getTypeSizeInChars(T).getQuantity();
   SmallString<256> MangledName;
   {
     llvm::raw_svector_ostream Out(MangledName);
-    getMangleContext().mangleCXXCatchableType(T, CD, Size, NVOffset,
+    getMangleContext().mangleCXXCatchableType(T, CD, CT, Size, NVOffset,
                                               VBPtrOffset, VBIndex, Out);
   }
   if (llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(MangledName))
     return getImageRelativeConstant(GV);
 
-  // The TypeDescriptor is used by the runtime to determine of a catch handler
+  // The TypeDescriptor is used by the runtime to determine if a catch handler
   // is appropriate for the exception object.
   llvm::Constant *TD = getImageRelativeConstant(getAddrOfRTTIDescriptor(T));
 
   // The runtime is responsible for calling the copy constructor if the
   // exception is caught by value.
-  llvm::Constant *CopyCtor =
-      CD ? llvm::ConstantExpr::getBitCast(
-               CGM.getAddrOfCXXStructor(CD, StructorType::Complete),
-               CGM.Int8PtrTy)
-         : llvm::Constant::getNullValue(CGM.Int8PtrTy);
+  llvm::Constant *CopyCtor;
+  if (CD) {
+    if (CT == Ctor_CopyingClosure)
+      CopyCtor = getAddrOfCXXCopyCtorClosure(CD);
+    else
+      CopyCtor = CGM.getAddrOfCXXStructor(CD, StructorType::Complete);
+
+    CopyCtor = llvm::ConstantExpr::getBitCast(CopyCtor, CGM.Int8PtrTy);
+  } else {
+    CopyCtor = llvm::Constant::getNullValue(CGM.Int8PtrTy);
+  }
   CopyCtor = getImageRelativeConstant(CopyCtor);
 
   bool IsScalar = !RD;
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index b69ddf7aebe..c62ecc762bc 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -782,14 +782,51 @@ ExprResult Sema::CheckCXXThrowOperand(SourceLocation ThrowLoc, Expr *E,
     }
   }
 
+  // The MSVC ABI creates a list of all types which can catch the exception
+  // object.  This list also references the appropriate copy constructor to call
+  // if the object is caught by value and has a non-trivial copy constructor.
   if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
+    // We are only interested in the public, unambiguous bases contained within
+    // the exception object.  Bases which are ambiguous or otherwise
+    // inaccessible are not catchable types.
     llvm::SmallVector<CXXRecordDecl *, 2> UnambiguousPublicSubobjects;
     getUnambiguousPublicSubobjects(RD, UnambiguousPublicSubobjects);
+
     for (CXXRecordDecl *Subobject : UnambiguousPublicSubobjects) {
-      if (CXXConstructorDecl *CD = LookupCopyingConstructor(Subobject, 0)) {
-        MarkFunctionReferenced(E->getExprLoc(), CD);
-        if (!CD->isTrivial())
-          Context.addCopyConstructorForExceptionObject(Subobject, CD);
+      // Attempt to lookup the copy constructor.  Various pieces of machinery
+      // will spring into action, like template instantiation, which means this
+      // cannot be a simple walk of the class's decls.  Instead, we must perform
+      // lookup and overload resolution.
+      CXXConstructorDecl *CD = LookupCopyingConstructor(Subobject, 0);
+      if (!CD)
+        continue;
+
+      // Mark the constructor referenced as it is used by this throw expression.
+      MarkFunctionReferenced(E->getExprLoc(), CD);
+
+      // Skip this copy constructor if it is trivial, we don't need to record it
+      // in the catchable type data.
+      if (CD->isTrivial())
+        continue;
+
+      // The copy constructor is non-trivial, create a mapping from this class
+      // type to this constructor.
+      // N.B.  The selection of copy constructor is not sensitive to this
+      // particular throw-site.  Lookup will be performed at the catch-site to
+      // ensure that the copy constructor is, in fact, accessible (via
+      // friendship or any other means).
+      Context.addCopyConstructorForExceptionObject(Subobject, CD);
+
+      // We don't keep the instantiated default argument expressions around so
+      // we must rebuild them here.
+      for (unsigned I = 1, E = CD->getNumParams(); I != E; ++I) {
+        // Skip any default arguments that we've already instantiated.
+        if (Context.getDefaultArgExprForConstructor(CD, I))
+          continue;
+
+        Expr *DefaultArg =
+            BuildCXXDefaultArgExpr(ThrowLoc, CD, CD->getParamDecl(I)).get();
+        Context.addDefaultArgExprForConstructor(CD, I, DefaultArg);
       }
     }
   }