[Clang] Export inline move constructors in dllexport-ed template instantiations on non-MSVC targets (#168170)

Previously, even when MSVC compatibility was not requested, inline move
constructors in dllexport-ed templates were not exported, which was
seemingly unintended.
On non-MSVC targets (MinGW, Cygwin, and PS), such move constructors
should be exported consistently with copy constructors and with the
behavior of modern MSVC.

Author: kikairoya

clang/include/clang/Basic/LangOptions.h

@@ -623,6 +623,8 @@ class LangOptions : public LangOptionsBase {
            !ObjCSubscriptingLegacyRuntime;
   }
 
+  bool isCompatibleWithMSVC() const { return MSCompatibilityVersion > 0; }
+
   bool isCompatibleWithMSVC(MSVCMajorVersion MajorVersion) const {
     return MSCompatibilityVersion >= MajorVersion * 100000U;
   }

clang/lib/Sema/SemaDeclCXX.cpp

@@ -6627,6 +6627,7 @@ void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
         auto *Ctor = dyn_cast<CXXConstructorDecl>(MD);
         if ((MD->isMoveAssignmentOperator() ||
              (Ctor && Ctor->isMoveConstructor())) &&
+            getLangOpts().isCompatibleWithMSVC() &&
             !getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015))
           continue;
 

clang/test/CodeGenCXX/dllexport.cpp

@@ -1130,5 +1130,6 @@ class __declspec(dllexport) ACE_Shared_Object {
 class __declspec(dllexport) ACE_Service_Object : public ACE_Shared_Object {};
 // Implicit move constructor declaration.
 // MSVC2015-DAG: define weak_odr dso_local dllexport {{.+}}ACE_Service_Object@@Q{{.+}}@$$Q
+// PS-DAG: define weak_odr dllexport void @_ZN18ACE_Service_ObjectC1EOS_
 // The declarations should not be exported.
 // MSVC2013-NOT: define weak_odr dso_local dllexport {{.+}}ACE_Service_Object@@Q{{.+}}@$$Q

clang/test/CodeGenCXX/dllimport.cpp

@@ -35,7 +35,7 @@ struct ExplicitSpec_NotImported {};
 #define USEMEMFUNC(class, func) void (class::*UNIQ(use)())() { return &class::func; }
 #define USESTATICMEMFUNC(class, func) void (*UNIQ(use)())() { return &class::func; }
 #define USECLASS(class) void UNIQ(USE)() { class x; }
-#define USECOPYASSIGN(class) class& (class::*UNIQ(use)())(class&) { return &class::operator=; }
+#define USECOPYASSIGN(class) class& (class::*UNIQ(use)())(const class&) { return &class::operator=; }
 #define USEMOVEASSIGN(class) class& (class::*UNIQ(use)())(class&&) { return &class::operator=; }
 
 //===----------------------------------------------------------------------===//
@@ -649,13 +649,15 @@ struct __declspec(dllimport) T {
   static int b;
   // MO1-DAG: @"?b@T@@2HA" = external dllimport global i32
 
-  T& operator=(T&) = default;
-  // MO1-DAG: define available_externally dllimport x86_thiscallcc nonnull align {{[0-9]+}} dereferenceable({{[0-9]+}}) ptr @"??4T@@QAEAAU0@AAU0@@Z"
+  T& operator=(const T&) = default;
+  // MO1-DAG: define available_externally dllimport x86_thiscallcc nonnull align {{[0-9]+}} dereferenceable({{[0-9]+}}) ptr @"??4T@@QAEAAU0@ABU0@@Z"
+  // PS-DAG: declare dllimport nonnull align {{[0-9]+}} dereferenceable({{[0-9]+}}) ptr @_ZN1TaSERKS_
 
   T& operator=(T&&) = default;
-  // Note: Don't mark inline move operators dllimport because current MSVC versions don't export them.
+  // Note: Don't mark inline move operators dllimport because MSVC versions before 2015 don't export them.
   // M18-DAG: define linkonce_odr dso_local x86_thiscallcc nonnull align {{[0-9]+}} dereferenceable({{[0-9]+}}) ptr @"??4T@@QAEAAU0@$$QAU0@@Z"
   // M19-DAG: define available_externally dllimport x86_thiscallcc nonnull align {{[0-9]+}} dereferenceable({{[0-9]+}}) ptr @"??4T@@QAEAAU0@$$QAU0@@Z"
+  // PS-DAG: declare dllimport nonnull align {{[0-9]+}} dereferenceable({{[0-9]+}}) ptr @_ZN1TaSEOS_
 };
 USEMEMFUNC(T, a)
 USESTATICMEMFUNC(T, StaticMethod)

clang/test/CodeGenCXX/mingw-template-dllexport.cpp

@@ -10,11 +10,16 @@
 
 template <class T>
 class c {
+public:
+  c(const c &) {}
+  c(c &&) noexcept {}
   void f() {}
 };
 
 template class __declspec(dllexport) c<int>;
 
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiEC1ERKS0_
+// CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiEC1EOS0_
 // CHECK: define {{.*}} dllexport {{.*}} @_ZN1cIiE1fEv
 
 extern template class __declspec(dllexport) c<char>;
@@ -27,6 +32,18 @@ template class __declspec(dllexport) c<double>;
 
 // CHECK-NOT: define {{.*}} dllexport {{.*}} @_ZN1cIdE1fEv
 
+extern template class __declspec(dllimport) c<short>;
+
+// CHECK: declare dllimport {{.*}} @_ZN1cIsEC1ERKS0_
+// CHECK: declare dllimport {{.*}} @_ZN1cIsEC1EOS0_
+// CHECK: declare dllimport {{.*}} @_ZN1cIsE1fEv
+
+void use_ctors(c<short> &&x) {
+  c<short> y{x};
+  c<short> z{static_cast<c<short> &&>(x)};
+  z.f();
+}
+
 template <class T>
 struct outer {
   void f();