IRGen: Do not set dllexport on declarations.

[pcc]

Summary

Setting dllexport on a declaration has no effect, as we do not emit export
directives for declarations.

Part of the fix for PR32334.

[rnk]

Lgtm

clang/lib/CodeGen/CodeGenModule.cpp

static void setLinkageAndVisibilityForGV(llvm::GlobalValue *GV,
   if (LV.getLinkage() != ExternalLinkage) {
     // Don't set internal linkage on declarations.
   } else {
     if (ND->hasAttr<DLLImportAttr>()) {
       GV->setLinkage(llvm::GlobalValue::ExternalLinkage);
       GV->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
     } else if (ND->hasAttr<DLLExportAttr>()) {
       GV->setLinkage(llvm::GlobalValue::ExternalLinkage);
-      GV->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
     } else if (ND->hasAttr<WeakAttr>() || ND->isWeakImported()) {
       // "extern_weak" is overloaded in LLVM; we probably should have
       // separate linkage types for this.
       GV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
     }
 
     // Set visibility on a declaration only if it's explicit.
     if (LV.isVisibilityExplicit())

clang/test/CodeGenCXX/dllexport.cpp

 // Declarations are not exported.
 
 // dllexport implies a definition.
 // MSC-NOT: @"\01??$VarTmplDef@UExplicitInst_Exported@@@@3HA"
 // GNU-NOT: @_Z10VarTmplDefI21ExplicitInst_ExportedE
 template<typename T> __declspec(dllexport) int VarTmplDef;
 INSTVAR(VarTmplDef<ExplicitInst_Exported>)
 
-// MSC-DAG: @"\01??$VarTmplImplicitDef@UImplicitInst_Exported@@@@3HA" = external dllexport global
-// GNU-DAG: @_Z18VarTmplImplicitDefI21ImplicitInst_ExportedE          = external dllexport global
+// MSC-DAG: @"\01??$VarTmplImplicitDef@UImplicitInst_Exported@@@@3HA" = external global
+// GNU-DAG: @_Z18VarTmplImplicitDefI21ImplicitInst_ExportedE          = external global
 template<typename T> __declspec(dllexport) int VarTmplImplicitDef;
 USEVAR(VarTmplImplicitDef<ImplicitInst_Exported>)
 
 // Export definition.
 // MSC-DAG: @"\01??$VarTmplInit1@UExplicitInst_Exported@@@@3HA" = weak_odr dllexport global i32 1, comdat, align 4
 // GNU-DAG: @_Z12VarTmplInit1I21ExplicitInst_ExportedE          = weak_odr dllexport global i32 1, comdat, align 4
 template<typename T> __declspec(dllexport) int VarTmplInit1 = 1;
 INSTVAR(VarTmplInit1<ExplicitInst_Exported>)
struct __declspec(dllexport) T {
   // Explicitly defaulted copy constructur:
   T(const T&) = default;
   // 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"
 
   static int b;
-  // M32-DAG: @"\01?b@T@@2HA" = external dllexport global i32
+  // M32-DAG: @"\01?b@T@@2HA" = external global i32
 
   static int c;
   // M32-DAG: @"\01?c@T@@2HA" = dllexport global i32 0, align 4
 };
 
 USEVAR(T::b)
 int T::c;