Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -4816,6 +4816,12 @@
              (CXXC && CXXC->isMoveConstructor())) &&
             !getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015))
           continue;
+
+        // MSVC2015 doesn't export trivial defaulted x-tor but copy assign
+        // operator is exported anyway.
+        if (getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015) &&
+            (CXXC || isa<CXXDestructorDecl>(MD)) && MD->isTrivial())
+          continue;
       }
     }
 
@@ -13057,28 +13063,42 @@
 
     // If the method was defaulted on its first declaration, we will have
     // already performed the checking in CheckCompletedCXXClass. Such a
-    // declaration doesn't trigger an implicit definition.
-    if (Primary == Primary->getCanonicalDecl())
+    // declaration doesn't trigger an implicit definition. But defaulted methods
+    // marked with dllexport do need implicit definition.
+    bool InClassDef = Primary == Primary->getCanonicalDecl();
+    bool HasDllexport = MD->hasAttr<DLLExportAttr>();
+    if (InClassDef && !HasDllexport)
       return;
 
-    CheckExplicitlyDefaultedSpecialMember(MD);
+    if (!InClassDef)
+      CheckExplicitlyDefaultedSpecialMember(MD);
 
     if (MD->isInvalidDecl())
       return;
 
+    auto PostAction = [=]{
+      if (InClassDef &&
+          (Member == CXXCopyAssignment ||
+           !getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015)))
+        ActOnFinishInlineFunctionDef(MD);
+    };
     switch (Member) {
     case CXXDefaultConstructor:
       DefineImplicitDefaultConstructor(DefaultLoc,
                                        cast<CXXConstructorDecl>(MD));
+      PostAction();
       break;
     case CXXCopyConstructor:
       DefineImplicitCopyConstructor(DefaultLoc, cast<CXXConstructorDecl>(MD));
+      PostAction();
       break;
     case CXXCopyAssignment:
       DefineImplicitCopyAssignment(DefaultLoc, MD);
+      PostAction();
       break;
     case CXXDestructor:
       DefineImplicitDestructor(DefaultLoc, cast<CXXDestructorDecl>(MD));
+      PostAction();
       break;
     case CXXMoveConstructor:
       DefineImplicitMoveConstructor(DefaultLoc, cast<CXXConstructorDecl>(MD));
Index: test/CodeGenCXX/dllexport-members.cpp
===================================================================
--- test/CodeGenCXX/dllexport-members.cpp
+++ test/CodeGenCXX/dllexport-members.cpp
@@ -1,5 +1,7 @@
-// RUN: %clang_cc1 -triple i686-windows-msvc -fms-compatibility   -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=MSC --check-prefix=M32 %s
-// RUN: %clang_cc1 -triple x86_64-windows-msvc -fms-compatibility -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=MSC --check-prefix=M64 %s
+// RUN: %clang_cc1 -triple i686-windows-msvc   -fms-compatibility -fms-compatibility-version=18 -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=MSC --check-prefix=M32 %s
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -fms-compatibility -fms-compatibility-version=18 -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=MSC --check-prefix=M64 %s
+// RUN: %clang_cc1 -triple i686-windows-msvc   -fms-compatibility -fms-compatibility-version=19 -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=M32VS2015 %s
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -fms-compatibility -fms-compatibility-version=19 -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=M64VS2015 %s
 // RUN: %clang_cc1 -triple i686-windows-gnu                       -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=GNU --check-prefix=G32 %s
 // RUN: %clang_cc1 -triple x86_64-windows-gnu                     -emit-llvm -std=c++1y -O0 -o - %s | FileCheck --check-prefix=GNU --check-prefix=G64 %s
 
@@ -427,6 +429,32 @@
 ExportDefaultedDefs& ExportDefaultedDefs::operator=(ExportDefaultedDefs&&) = default;
 
 
+// Export defaulted member function definitions declared inside class.
+struct ExportDefaultedInclassDefs {
+  __declspec(dllexport) ExportDefaultedInclassDefs() = default;
+  // M32VS2013-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+  // M64VS2013-DAG: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+  // M32VS2015-NOT: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+  // M64VS2015-NOT: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+
+  __declspec(dllexport) ~ExportDefaultedInclassDefs() = default;
+  // M32VS2013-DAG: define weak_odr dllexport x86_thiscallcc void @"\01??1ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+  // M64VS2013-DAG: define weak_odr dllexport                void @"\01??1ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+  // M32VS2015-NOT: define weak_odr dllexport x86_thiscallcc void @"\01??1ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+  // M64VS2015-NOT: define weak_odr dllexport                void @"\01??1ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+
+  __declspec(dllexport) ExportDefaultedInclassDefs(const ExportDefaultedInclassDefs&) = default;
+  // M32VS2013-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@ABU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M64VS2013-DAG: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@AEBU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M32VS2015-NOT: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@ABU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M64VS2015-NOT: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@AEBU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+
+  __declspec(dllexport) ExportDefaultedInclassDefs& operator=(const ExportDefaultedInclassDefs&) = default;
+  // M32-DAG: define weak_odr dllexport x86_thiscallcc dereferenceable({{[0-9]+}}) %struct.ExportDefaultedInclassDefs* @"\01??4ExportDefaultedInclassDefs@@QAEAAU0@ABU0@@Z"(%struct.ExportDefaultedInclassDefs* %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M64-DAG: define weak_odr dllexport                dereferenceable({{[0-9]+}}) %struct.ExportDefaultedInclassDefs* @"\01??4ExportDefaultedInclassDefs@@QEAAAEAU0@AEBU0@@Z"(%struct.ExportDefaultedInclassDefs* %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+};
+
+
 // Export allocation functions.
 struct ExportAlloc {
   __declspec(dllexport) void* operator new(__SIZE_TYPE__);
Index: test/CodeGenCXX/dllexport.cpp
===================================================================
--- test/CodeGenCXX/dllexport.cpp
+++ test/CodeGenCXX/dllexport.cpp
@@ -1,8 +1,8 @@
-// RUN: %clang_cc1 -triple i686-windows-msvc   -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O1 -mconstructor-aliases -disable-llvm-optzns -o - %s -w -fms-compatibility-version=19.00 | FileCheck --check-prefix=MSC --check-prefix=M32 -check-prefix=MSVC2015 %s
-// RUN: %clang_cc1 -triple i686-windows-msvc   -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O1 -mconstructor-aliases -disable-llvm-optzns -o - %s -w -fms-compatibility-version=18.00 | FileCheck --check-prefix=MSC --check-prefix=M32 -check-prefix=MSVC2013 %s
+// RUN: %clang_cc1 -triple i686-windows-msvc   -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O1 -mconstructor-aliases -disable-llvm-optzns -o - %s -w -fms-compatibility-version=19.00 | FileCheck --check-prefix=MSC --check-prefix=M32 -check-prefix=MSVC2015 -check-prefix=M32MSVC2015 %s
+// RUN: %clang_cc1 -triple i686-windows-msvc   -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O1 -mconstructor-aliases -disable-llvm-optzns -o - %s -w -fms-compatibility-version=18.00 | FileCheck --check-prefix=MSC --check-prefix=M32 -check-prefix=MSVC2013 -check-prefix=M32MSVC2013 %s
 
-// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O0 -o - %s -w -fms-compatibility-version=19.00 | FileCheck --check-prefix=MSC --check-prefix=M64 -check-prefix=MSVC2015 %s
-// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O0 -o - %s -w -fms-compatibility-version=18.00 | FileCheck --check-prefix=MSC --check-prefix=M64 -check-prefix=MSVC2013 %s
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O0 -o - %s -w -fms-compatibility-version=19.00 | FileCheck --check-prefix=MSC --check-prefix=M64 -check-prefix=MSVC2015 -check-prefix=M64MSVC2015 %s
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O0 -o - %s -w -fms-compatibility-version=18.00 | FileCheck --check-prefix=MSC --check-prefix=M64 -check-prefix=MSVC2013 -check-prefix=M64MSVC2013 %s
 
 // RUN: %clang_cc1 -triple i686-windows-gnu    -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O0 -o - %s -w | FileCheck --check-prefix=GNU --check-prefix=G32 %s
 // RUN: %clang_cc1 -triple x86_64-windows-gnu  -emit-llvm -std=c++1y -fno-threadsafe-statics -fms-extensions -O0 -o - %s -w | FileCheck --check-prefix=GNU --check-prefix=G64 %s
@@ -561,7 +561,7 @@
 
   // Explicitly defaulted copy constructur:
   T(const T&) = default;
-  // M32-DAG: define weak_odr dllexport x86_thiscallcc %struct.T* @"\01??0T@@QAE@ABU0@@Z"
+  // M32MSVC2013-DAG: define weak_odr dllexport x86_thiscallcc %struct.T* @"\01??0T@@QAE@ABU0@@Z"
 
   void a() {}
   // M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?a@T@@QAEXXZ"
@@ -647,9 +647,34 @@
 
 struct __declspec(dllexport) DefaultedCtorsDtors {
   DefaultedCtorsDtors() = default;
-  // M32-DAG: define weak_odr dllexport x86_thiscallcc %struct.DefaultedCtorsDtors* @"\01??0DefaultedCtorsDtors@@QAE@XZ"
+  // M32MSVC2013-DAG: define weak_odr dllexport x86_thiscallcc %struct.DefaultedCtorsDtors* @"\01??0DefaultedCtorsDtors@@QAE@XZ"
   ~DefaultedCtorsDtors() = default;
-  // M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01??1DefaultedCtorsDtors@@QAE@XZ"
+  // M32MSVC2013-DAG: define weak_odr dllexport x86_thiscallcc void @"\01??1DefaultedCtorsDtors@@QAE@XZ"
+};
+
+// Export defaulted member function definitions declared inside class.
+struct __declspec(dllexport) ExportDefaultedInclassDefs {
+  ExportDefaultedInclassDefs() = default;
+  // M32VS2013-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+  // M64VS2013-DAG: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+  // M32VS2015-NOT: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+  // M64VS2015-NOT: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* returned %this)
+
+  ~ExportDefaultedInclassDefs() = default;
+  // M32VS2013-DAG: define weak_odr dllexport x86_thiscallcc void @"\01??1ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+  // M64VS2013-DAG: define weak_odr dllexport                void @"\01??1ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+  // M32VS2015-NOT: define weak_odr dllexport x86_thiscallcc void @"\01??1ExportDefaultedInclassDefs@@QAE@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+  // M64VS2015-NOT: define weak_odr dllexport                void @"\01??1ExportDefaultedInclassDefs@@QEAA@XZ"(%struct.ExportDefaultedInclassDefs* %this)
+
+  ExportDefaultedInclassDefs(const ExportDefaultedInclassDefs&) = default;
+  // M32VS2013-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@ABU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M64VS2013-DAG: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@AEBU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M32VS2015-NOT: define weak_odr dllexport x86_thiscallcc %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QAE@ABU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M64VS2015-NOT: define weak_odr dllexport                %struct.ExportDefaultedInclassDefs* @"\01??0ExportDefaultedInclassDefs@@QEAA@AEBU0@@Z"(%struct.ExportDefaultedInclassDefs* returned %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+
+  ExportDefaultedInclassDefs& operator=(const ExportDefaultedInclassDefs&) = default;
+  // M32-DAG: define weak_odr dllexport x86_thiscallcc dereferenceable({{[0-9]+}}) %struct.ExportDefaultedInclassDefs* @"\01??4ExportDefaultedInclassDefs@@QAEAAU0@ABU0@@Z"(%struct.ExportDefaultedInclassDefs* %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
+  // M64-DAG: define weak_odr dllexport                dereferenceable({{[0-9]+}}) %struct.ExportDefaultedInclassDefs* @"\01??4ExportDefaultedInclassDefs@@QEAAAEAU0@AEBU0@@Z"(%struct.ExportDefaultedInclassDefs* %this, %struct.ExportDefaultedInclassDefs* dereferenceable({{[0-9]+}}))
 };
 
 namespace ReferencedInlineMethodInNestedClass {
@@ -721,7 +746,7 @@
   // M32-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExplicitInstConstexprMembers* @"\01??0?$ExplicitInstConstexprMembers@X@@QAE@XZ"
 
   ExplicitInstConstexprMembers(const ExplicitInstConstexprMembers&) = default;
-  // M32-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExplicitInstConstexprMembers* @"\01??0?$ExplicitInstConstexprMembers@X@@QAE@ABU0@@Z"
+  // M32MSVC2013-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExplicitInstConstexprMembers* @"\01??0?$ExplicitInstConstexprMembers@X@@QAE@ABU0@@Z"
 
   constexpr int f() const { return 42; }
   // M32-DAG: define weak_odr dllexport x86_thiscallcc i32 @"\01?f@?$ExplicitInstConstexprMembers@X@@QBEHXZ"