[clang-cl] Inherit dllexport to static locals also in template instantiations (PR39496)

In the course of D51340, @takuto.ikuta discovered that Clang fails to put
dllexport/import attributes on static locals during template instantiation.

For regular functions, this happens in Sema::FinalizeDeclaration(), however for
template instantiations we need to do something in or around
TemplateDeclInstantiator::VisitVarDecl(). This patch does that, and extracts
the code to a utility function.

Differential Revision: https://reviews.llvm.org/D53870

llvm-svn: 345699

clang/include/clang/Sema/Sema.h

@@ -2001,6 +2001,7 @@ public:
                                         SourceLocation AttrEnd);
   void SetDeclDeleted(Decl *dcl, SourceLocation DelLoc);
   void SetDeclDefaulted(Decl *dcl, SourceLocation DefaultLoc);
+  void CheckStaticLocalForDllExport(VarDecl *VD);
   void FinalizeDeclaration(Decl *D);
   DeclGroupPtrTy FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
                                          ArrayRef<Decl *> Group);

clang/lib/Sema/SemaDecl.cpp

@@ -11924,6 +11924,23 @@ static bool hasDependentAlignment(VarDecl *VD) {
   return false;
 }
 
+/// Check if VD needs to be dllexport/dllimport due to being in a
+/// dllexport/import function.
+void Sema::CheckStaticLocalForDllExport(VarDecl *VD) {
+  assert(VD->isStaticLocal());
+
+  auto *FD = dyn_cast_or_null<FunctionDecl>(VD->getParentFunctionOrMethod());
+  if (!FD)
+    return;
+
+  // Static locals inherit dll attributes from their function.
+  if (Attr *A = getDLLAttr(FD)) {
+    auto *NewAttr = cast<InheritableAttr>(A->clone(getASTContext()));
+    NewAttr->setInherited(true);
+    VD->addAttr(NewAttr);
+  }
+}
+
 /// FinalizeDeclaration - called by ParseDeclarationAfterDeclarator to perform
 /// any semantic actions necessary after any initializer has been attached.
 void Sema::FinalizeDeclaration(Decl *ThisDecl) {
@@ -11977,14 +11994,9 @@ void Sema::FinalizeDeclaration(Decl *ThisDecl) {
   }
 
   if (VD->isStaticLocal()) {
-    if (FunctionDecl *FD =
-            dyn_cast_or_null<FunctionDecl>(VD->getParentFunctionOrMethod())) {
-      // Static locals inherit dll attributes from their function.
-      if (Attr *A = getDLLAttr(FD)) {
-        auto *NewAttr = cast<InheritableAttr>(A->clone(getASTContext()));
-        NewAttr->setInherited(true);
-        VD->addAttr(NewAttr);
-      }
+    CheckStaticLocalForDllExport(VD);
+
+    if (dyn_cast_or_null<FunctionDecl>(VD->getParentFunctionOrMethod())) {
       // CUDA 8.0 E.3.9.4: Within the body of a __device__ or __global__
       // function, only __shared__ variables or variables without any device
       // memory qualifiers may be declared with static storage class.

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -728,6 +728,9 @@ Decl *TemplateDeclInstantiator::VisitVarDecl(VarDecl *D,
                           D->getLocation(), D->getIdentifier(), DI->getType(),
                           DI, D->getStorageClass());
 
+  if (Var->isStaticLocal())
+    SemaRef.CheckStaticLocalForDllExport(Var);
+
   // In ARC, infer 'retaining' for variables of retainable type.
   if (SemaRef.getLangOpts().ObjCAutoRefCount &&
       SemaRef.inferObjCARCLifetime(Var))

clang/test/CodeGenCXX/dllexport.cpp

@@ -1012,6 +1012,18 @@ struct __declspec(dllexport) LayerTreeImpl {
 // M32-DAG: define weak_odr dso_local dllexport x86_thiscallcc %"struct.LayerTreeImpl::ElementLayers"* @"??0ElementLayers@LayerTreeImpl@@QAE@XZ"
 // M64-DAG: define weak_odr dso_local dllexport %"struct.LayerTreeImpl::ElementLayers"* @"??0ElementLayers@LayerTreeImpl@@QEAA@XZ"
 
+namespace pr39496 {
+// Make sure dll attribute are inherited by static locals also in template
+// specializations.
+template <typename> struct __declspec(dllexport) S { int foo() { static int x; return x++; } };
+int foo() { S<int> s; return s.foo(); }
+// MSC-DAG: @"?x@?{{1|2}}??foo@?$S@H@pr39496@@Q{{[A-Z]*}}HXZ@4HA" = weak_odr dso_local dllexport global i32 0, comdat, align 4
+
+template <typename> struct T { int foo() { static int x; return x++; } };
+template struct __declspec(dllexport) T<int>;
+// MSC-DAG: @"?x@?{{1|2}}??foo@?$T@H@pr39496@@Q{{[A-Z]*}}HXZ@4HA" = weak_odr dso_local dllexport global i32 0, comdat, align 4
+}
+
 class __declspec(dllexport) ACE_Shared_Object {
 public:
   virtual ~ACE_Shared_Object();

clang/test/CodeGenCXX/dllimport.cpp

@@ -996,3 +996,16 @@ template struct __declspec(dllexport) ExplicitInstantiationDeclTemplateBase2<int
 USEMEMFUNC(ExplicitInstantiationDeclTemplateBase2<int>, func)
 // M32-DAG: declare dllimport x86_thiscallcc void @"?func@?$ExplicitInstantiationDeclTemplateBase2@H@@QAEXXZ"
 // G32-DAG: define weak_odr dso_local x86_thiscallcc void @_ZN38ExplicitInstantiationDeclTemplateBase2IiE4funcEv
+
+namespace pr39496 {
+// Make sure dll attribute are inherited by static locals also in template
+// specializations.
+template <typename> struct __declspec(dllimport) S { int foo() { static int x; return x++; } };
+int foo() { S<int> s; return s.foo(); }
+// MO1-DAG: @"?x@?{{1|2}}??foo@?$S@H@pr39496@@Q{{[A-Z]*}}HXZ@4HA" = available_externally dllimport global i32 0, align 4
+
+template <typename> struct T { int foo() { static int x; return x++; } };
+extern template struct __declspec(dllimport) T<int>;
+int bar() { T<int> t; return t.foo(); }
+// MO1-DAG: @"?x@?{{1|2}}??foo@?$T@H@pr39496@@Q{{[A-Z]*}}HXZ@4HA" = available_externally dllimport global i32 0, align 4
+}