Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -846,14 +846,25 @@
   GVALinkage Linkage = getContext().GetGVALinkageForFunction(D);
 
   if (isa<CXXDestructorDecl>(D) &&
-      getCXXABI().useThunkForDtorVariant(cast<CXXDestructorDecl>(D),
-                                         GD.getDtorType())) {
-    // Destructor variants in the Microsoft C++ ABI are always internal or
-    // linkonce_odr thunks emitted on an as-needed basis.
-    return Linkage == GVA_Internal ? llvm::GlobalValue::InternalLinkage
-                                   : llvm::GlobalValue::LinkOnceODRLinkage;
+      Context.getTargetInfo().getCXXABI().isMicrosoft()) {
+    switch (GD.getDtorType()) {
+    case CXXDtorType::Dtor_Base:
+      break;
+    case CXXDtorType::Dtor_Comdat:
+    case CXXDtorType::Dtor_Complete:
+      if (D->hasAttr<DLLImportAttr>() &&
+	  (cast<CXXDestructorDecl>(D)->getParent()->getNumVBases() ||
+	   (Linkage == GVA_AvailableExternally ||
+	    Linkage == GVA_StrongExternal)))
+	return llvm::Function::AvailableExternallyLinkage;
+      else
+        return Linkage == GVA_Internal ? llvm::GlobalValue::InternalLinkage
+                                       : llvm::GlobalValue::LinkOnceODRLinkage;
+    case CXXDtorType::Dtor_Deleting:
+      return Linkage == GVA_Internal ? llvm::GlobalValue::InternalLinkage
+                                     : llvm::GlobalValue::LinkOnceODRLinkage;
+    }
   }
-
   if (isa<CXXConstructorDecl>(D) &&
       cast<CXXConstructorDecl>(D)->isInheritingConstructor() &&
       Context.getTargetInfo().getCXXABI().isMicrosoft()) {
@@ -869,12 +880,25 @@
 void CodeGenModule::setFunctionDLLStorageClass(GlobalDecl GD, llvm::Function *F) {
   const auto *FD = cast<FunctionDecl>(GD.getDecl());
 
-  if (const auto *Dtor = dyn_cast_or_null<CXXDestructorDecl>(FD)) {
-    if (getCXXABI().useThunkForDtorVariant(Dtor, GD.getDtorType())) {
+  if (dyn_cast_or_null<CXXDestructorDecl>(FD)) {
+    switch (GD.getDtorType()) {
+    case CXXDtorType::Dtor_Comdat:
+    case CXXDtorType::Dtor_Deleting: {
       // Don't dllexport/import destructor thunks.
       F->setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass);
       return;
     }
+    case CXXDtorType::Dtor_Complete:
+      if (FD->hasAttr<DLLImportAttr>())
+        F->setDLLStorageClass(llvm::GlobalVariable::DLLImportStorageClass);
+      else if (FD->hasAttr<DLLExportAttr>())
+        F->setDLLStorageClass(llvm::GlobalVariable::DLLExportStorageClass);
+      else
+        F->setDLLStorageClass(llvm::GlobalVariable::DefaultStorageClass);
+      return;
+    case CXXDtorType::Dtor_Base:
+      break;
+    }
   }
 
   if (FD->hasAttr<DLLImportAttr>())
Index: test/CodeGenCXX/dllimport-dtor-thunks.cpp
===================================================================
--- test/CodeGenCXX/dllimport-dtor-thunks.cpp
+++ test/CodeGenCXX/dllimport-dtor-thunks.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -mconstructor-aliases %s -triple x86_64-windows-msvc -fms-extensions -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -mconstructor-aliases %s -triple x86_64-windows-msvc -fms-extensions -emit-llvm -O1 -disable-llvm-passes -o - | FileCheck --check-prefix=MO1 %s
 
 // FIXME: We should really consider removing -mconstructor-aliases for MS C++
 // ABI. The risk of bugs introducing ABI incompatibility under
@@ -23,9 +24,7 @@
   virtual ~ImportOverrideVDtor() {}
 };
 
-// Virtually inherits from a non-dllimport base class. This time we need to call
-// the complete destructor and emit it inline. It's not exported from the DLL,
-// and it must be emitted.
+// Virtually inherits from a non-dllimport base class. Emit the vbase destructor.
 struct __declspec(dllimport) ImportVBaseOverrideVDtor
     : public virtual BaseClass {
   virtual ~ImportVBaseOverrideVDtor() {}
@@ -41,9 +40,11 @@
 // needs the complete destructor (_D).
 // CHECK-LABEL: define void @testit()
 // CHECK:  call void @"\01??_DImportVBaseOverrideVDtor@@QEAAXXZ"(%struct.ImportVBaseOverrideVDtor* %{{.*}})
-// CHECK:  call void @"\01??1ImportOverrideVDtor@@UEAA@XZ"(%struct.ImportOverrideVDtor* %{{.*}})
-// CHECK:  call void @"\01??1ImportIntroVDtor@@UEAA@XZ"(%struct.ImportIntroVDtor* %{{.*}})
+// CHECK:  call void @"\01??_DImportOverrideVDtor@@QEAAXXZ"(%struct.ImportOverrideVDtor* %{{.*}})
+// CHECK:  call void @"\01??_DImportIntroVDtor@@QEAAXXZ"(%struct.ImportIntroVDtor* %{{.*}})
 
-// CHECK-LABEL: define linkonce_odr void @"\01??_DImportVBaseOverrideVDtor@@QEAAXXZ"
-// CHECK-LABEL: declare dllimport void @"\01??1ImportOverrideVDtor@@UEAA@XZ"
-// CHECK-LABEL: declare dllimport void @"\01??1ImportIntroVDtor@@UEAA@XZ"
+// CHECK-LABEL: declare dllimport void @"\01??_DImportVBaseOverrideVDtor@@QEAAXXZ"(%struct.ImportVBaseOverrideVDtor*)
+// CHECK-LABEL: declare dllimport void @"\01??_DImportOverrideVDtor@@QEAAXXZ"(%struct.ImportOverrideVDtor*)
+// CHECK-LABEL: declare dllimport void @"\01??_DImportIntroVDtor@@QEAAXXZ"(%struct.ImportIntroVDtor*)
+
+// MO1-DAG: define available_externally dllimport void @"\01??_DImportIntroVDtor@@QEAAXXZ"
Index: test/CodeGenCXX/dllimport-members.cpp
===================================================================
--- test/CodeGenCXX/dllimport-members.cpp
+++ test/CodeGenCXX/dllimport-members.cpp
@@ -414,8 +414,7 @@
   // G64-DAG: declare dllimport                void                    @_ZN14ImportSpecialsC1Ev(%struct.ImportSpecials*)
   __declspec(dllimport) ImportSpecials();
 
-  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??1ImportSpecials@@QAE@XZ"(%struct.ImportSpecials*)
-  // M64-DAG: declare dllimport                void @"\01??1ImportSpecials@@QEAA@XZ"(%struct.ImportSpecials*)
+  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportSpecials@@QAEXXZ"(%struct.ImportSpecials*)
   // G32-DAG: declare dllimport x86_thiscallcc void                    @_ZN14ImportSpecialsD1Ev(%struct.ImportSpecials*)
   // G64-DAG: declare dllimport                void                    @_ZN14ImportSpecialsD1Ev(%struct.ImportSpecials*)
   __declspec(dllimport) ~ImportSpecials();
@@ -457,8 +456,7 @@
   // GO1-DAG: define linkonce_odr x86_thiscallcc void @_ZN20ImportInlineSpecialsC1Ev(
   __declspec(dllimport) ImportInlineSpecials() {}
 
-  // M32-DAG: declare dllimport   x86_thiscallcc void @"\01??1ImportInlineSpecials@@QAE@XZ"(%struct.ImportInlineSpecials*)
-  // M64-DAG: declare dllimport                  void @"\01??1ImportInlineSpecials@@QEAA@XZ"(%struct.ImportInlineSpecials*)
+  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportInlineSpecials@@QAEXXZ"(%struct.ImportInlineSpecials*)
   // G32-DAG: define linkonce_odr x86_thiscallcc void @_ZN20ImportInlineSpecialsD1Ev(%struct.ImportInlineSpecials* %this)
   // G64-DAG: define linkonce_odr                void @_ZN20ImportInlineSpecialsD1Ev(%struct.ImportInlineSpecials* %this)
   // MO1-DAG: define available_externally dllimport x86_thiscallcc void @"\01??1ImportInlineSpecials@@QAE@XZ"(
@@ -512,8 +510,7 @@
   // GO1-DAG: define linkonce_odr x86_thiscallcc void @_ZN15ImportDefaultedC1Ev(%struct.ImportDefaulted* %this)
   __declspec(dllimport) ImportDefaulted() = default;
 
-  // M32-DAG: declare dllimport   x86_thiscallcc void @"\01??1ImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted*)
-  // M64-DAG: declare dllimport                  void @"\01??1ImportDefaulted@@QEAA@XZ"(%struct.ImportDefaulted*)
+  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportDefaulted@@QAEXXZ"(%struct.ImportDefaulted*)
   // G32-DAG: define linkonce_odr x86_thiscallcc void @_ZN15ImportDefaultedD1Ev(%struct.ImportDefaulted* %this)
   // G64-DAG: define linkonce_odr                void @_ZN15ImportDefaultedD1Ev(%struct.ImportDefaulted* %this)
   // MO1-DAG: define available_externally dllimport x86_thiscallcc void @"\01??1ImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted* %this)
@@ -578,8 +575,7 @@
 
 #ifdef MSABI
 // For MinGW, the function will not be dllimport, and we cannot add the attribute now.
-// M32-DAG: declare dllimport x86_thiscallcc void @"\01??1ImportDefaultedDefs@@QAE@XZ"(%struct.ImportDefaultedDefs*)
-// M64-DAG: declare dllimport                void @"\01??1ImportDefaultedDefs@@QEAA@XZ"(%struct.ImportDefaultedDefs*)
+// M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportDefaulted@@QAEXXZ"(%struct.ImportDefaulted*)
 __declspec(dllimport) ImportDefaultedDefs::~ImportDefaultedDefs() = default;
 #endif
 
Index: test/CodeGenCXX/dllimport-virtual-base.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/dllimport-virtual-base.cpp
@@ -0,0 +1,73 @@
+// RUN: %clang_cc1 -triple i386-pc-windows -emit-llvm -fms-compatibility %s -x c++ -o - | FileCheck %s
+
+namespace test1 {
+struct BaseClass {
+  ~BaseClass();
+};
+
+struct __declspec(dllimport) Concrete : virtual BaseClass {
+};
+
+Concrete c;
+
+// CHECK-LABEL: declare dllimport x86_thiscallcc %"struct.test1::Concrete"* @"\01??0Concrete@test1@@QAE@XZ"
+// CHECK-LABEL: declare dllimport x86_thiscallcc void @"\01??_DConcrete@test1@@QAEXXZ"(%"struct.test1::Concrete"*) unnamed_addr #2
+
+} // namespace test1
+
+namespace test2 {
+class BaseClass {
+public:
+  virtual ~BaseClass(){};
+};
+
+class __declspec(dllimport) VirtualClass : public virtual BaseClass {
+public:
+  virtual ~VirtualClass(){};
+};
+
+int main() {
+  VirtualClass c;
+  return 0;
+}
+
+// CHECK-LABEL: declare dllimport x86_thiscallcc %"class.test2::VirtualClass"* @"\01??0VirtualClass@test2@@QAE@XZ"
+// CHECK-LABEL: declare dllimport x86_thiscallcc void @"\01??_DVirtualClass@test2@@QAEXXZ"(%"class.test2::VirtualClass"*)
+
+} // namespace test2
+
+namespace test3 {
+class IVirtualBase {
+public:
+  virtual ~IVirtualBase(){};
+  virtual void speak() = 0;
+};
+
+class VirtualClass : public virtual IVirtualBase {
+public:
+  virtual ~VirtualClass(){};
+  virtual void eat() = 0;
+};
+
+class __declspec(dllimport) ConcreteClass : public VirtualClass {
+public:
+  ConcreteClass(int nn);
+  void speak();
+  void eat();
+  virtual ~ConcreteClass();
+
+private:
+  int n;
+};
+
+int main() {
+  ConcreteClass c(10);
+  c.speak();
+  c.eat();
+  return 0;
+}
+
+// CHECK-LABEL: declare dllimport x86_thiscallcc %"class.test3::ConcreteClass"* @"\01??0ConcreteClass@test3@@QAE@H@Z"
+// CHECK-LABEL: declare dllimport x86_thiscallcc void @"\01??_DConcreteClass@test3@@QAEXXZ"(%"class.test3::ConcreteClass"*)
+
+} // namespace test3
Index: test/CodeGenCXX/dllimport.cpp
===================================================================
--- test/CodeGenCXX/dllimport.cpp
+++ test/CodeGenCXX/dllimport.cpp
@@ -362,8 +362,8 @@
 struct __declspec(dllimport) ClassWithNonDllImportBase : public ClassWithDtor { };
 USECLASS(ClassWithNonDllImportField);
 USECLASS(ClassWithNonDllImportBase);
-// MO1-DAG: declare dllimport x86_thiscallcc void @"\01??1ClassWithNonDllImportBase@@QAE@XZ"(%struct.ClassWithNonDllImportBase*)
-// MO1-DAG: declare dllimport x86_thiscallcc void @"\01??1ClassWithNonDllImportField@@QAE@XZ"(%struct.ClassWithNonDllImportField*)
+// MO1-DAG: declare dllimport x86_thiscallcc void @"\01??_DClassWithNonDllImportBase@@QAEXXZ"(%struct.ClassWithNonDllImportBase*)
+// MO1-DAG: declare dllimport x86_thiscallcc void @"\01??_DClassWithNonDllImportField@@QAEXXZ"(%struct.ClassWithNonDllImportField*)
 struct ClassWithCtor { ClassWithCtor() {} };
 struct __declspec(dllimport) ClassWithNonDllImportFieldWithCtor { ClassWithCtor t; };
 USECLASS(ClassWithNonDllImportFieldWithCtor);
Index: test/CodeGenCXX/external-linkage.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/external-linkage.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -triple i686-windows-msvc   -fno-rtti -fno-threadsafe-statics -fms-extensions -fms-compatibility-version=18.00 -emit-llvm -std=c++1y -O1 -disable-llvm-passes -o - %s -DMSABI -w | FileCheck --check-prefix=MO1 --check-prefix=MO2 %s
+
+// RUN: %clang_cc1 -triple i686-windows-msvc -fno-rtti -fno-threadsafe-statics -fms-extensions -fms-compatibility-version=18.00 -emit-llvm -std=c++1y -o - %s -DMSABI -w | FileCheck --check-prefix=MO3 --check-prefix=MO4 %s
+
+// MO1-DAG:@"\01??_8B@@7B@" = available_externally dllimport unnamed_addr constant [2 x i32] [i32 0, i32 4]
+// MO2-DAG: define available_externally dllimport x86_thiscallcc %struct.B* @"\01??0B@@QAE@XZ"
+
+struct __declspec(dllimport) A {
+  virtual ~A();
+};
+struct __declspec(dllimport) B : virtual A {
+  virtual ~B();
+};
+void f() { B b; }
+
+// MO3-DAG: declare dllimport x86_thiscallcc %struct.B* @"\01??0B@@QAE@XZ"
+// MO4-DAG: declare dllimport x86_thiscallcc void @"\01??_DB@@QAEXXZ"