Don't dllimport/export destructor variants implemented by thunks.

[hans]

Summary

MSVC doesn't export these functions, so trying to import them doesn't work.
Also, don't let any dll attributes on the CXXDestructorDecl influence the
thunk's linkage -- it should always be linkonce_odr.

This takes care of the FIXME's for this in Nico's tests.

[rnk]

lib/CodeGen/CodeGenModule.cpp

1396–1397

This belongs after the call to setLinkageAndVisibilityForGV() in CodeGenModule::SetFunctionAttributes(), to keep all the dllstorage class code closer together.

1925

I don't like how this hyper-specific bool got threaded all the way into getLLVMLinkageForDeclarator in r207451. I think with this change we can handle dtor thunks as a special case in CodeGenModule::getFunctionLinkage() with something like:

if (isa<CXXDestructorDecl>(D) &&
    getCXXABI().useThunkForDtorVariant(cast<CXXDestructorDecl>(D),
                                       GD.getDtorType())) {
  return Linkage == GVA_Internal ? llvm::GlobalValue::InternalLinkage
                                 : llvm::GlobalValue::LinkOnceODRLinkage;
}

I don't think having the 'weak' attribute on a dtor should affect the linkage of its thunks.

[hans]

lib/CodeGen/CodeGenModule.cpp

1396–1397

Done.

1925

Done.

[hans]

Addressing Reid's comments.

[rnk]

lgtm

[hans]

Closed by commit rL209706 (authored by @hans).

lib/CodeGen/CodeGenModule.cpp

CodeGenModule::GetOrCreateLLVMFunction(StringRef MangledName,
   if (ExtraAttrs.hasAttributes(llvm::AttributeSet::FunctionIndex)) {
     llvm::AttrBuilder B(ExtraAttrs, llvm::AttributeSet::FunctionIndex);
     F->addAttributes(llvm::AttributeSet::FunctionIndex,
                      llvm::AttributeSet::get(VMContext,
                                              llvm::AttributeSet::FunctionIndex,
                                              B));
   }
 
+  if (const auto *Dtor = dyn_cast_or_null<CXXDestructorDecl>(D)) {
+    if (getCXXABI().useThunkForDtorVariant(Dtor, GD.getDtorType())) {
+      // Don't dllexport/import destructor thunks.
+      F->setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass);
+    }
+  }
+
   if (!DontDefer) {
     // All MSVC dtors other than the base dtor are linkonce_odr and delegate to
     // each other bottoming out with the base dtor.  Therefore we emit non-base
     // dtors on usage, even if there is no dtor definition in the TU.
     if (D && isa<CXXDestructorDecl>(D) &&
         getCXXABI().useThunkForDtorVariant(cast<CXXDestructorDecl>(D),
                                            GD.getDtorType()))
       addDeferredDeclToEmit(F, GD);
static bool isVarDeclStrongDefinition(const VarDecl *D, bool NoCommon) {
   if (D->hasAttr<WeakImportAttr>())
     return true;
 
   return false;
 }
 
 llvm::GlobalValue::LinkageTypes CodeGenModule::getLLVMLinkageForDeclarator(
     const DeclaratorDecl *D, GVALinkage Linkage, bool IsConstantVariable,
     bool UseThunkForDtorVariant) {
   if (Linkage == GVA_Internal)
     return llvm::Function::InternalLinkage;
 
   if (D->hasAttr<WeakAttr>()) {
     if (IsConstantVariable)
       return llvm::GlobalVariable::WeakODRLinkage;
     else
       return llvm::GlobalVariable::WeakAnyLinkage;
   }
 
+  // Destructor variants in the Microsoft C++ ABI are always linkonce_odr thunks
+  // emitted on an as-needed basis.
+  if (UseThunkForDtorVariant)
+    return llvm::GlobalValue::LinkOnceODRLinkage;
+
   // We are guaranteed to have a strong definition somewhere else,
   // so we can use available_externally linkage.
   if (Linkage == GVA_AvailableExternally)
     return llvm::Function::AvailableExternallyLinkage;
 
   // Note that Apple's kernel linker doesn't support symbol
   // coalescing, so we need to avoid linkonce and weak linkages there.
   // Normally, this means we just map to internal, but for explicit
llvm::GlobalValue::LinkageTypes CodeGenModule::getLLVMLinkageForDeclarator(
   // An explicit instantiation of a template has weak linkage, since
   // explicit instantiations can occur in multiple translation units
   // and must all be equivalent. However, we are not allowed to
   // throw away these explicit instantiations.
   if (Linkage == GVA_StrongODR)
     return !Context.getLangOpts().AppleKext ? llvm::Function::WeakODRLinkage
                                             : llvm::Function::ExternalLinkage;
 
-  // Destructor variants in the Microsoft C++ ABI are always linkonce_odr thunks
-  // emitted on an as-needed basis.
-  if (UseThunkForDtorVariant)
-    return llvm::GlobalValue::LinkOnceODRLinkage;
-
   // If required by the ABI, give definitions of static data members with inline
   // initializers at least linkonce_odr linkage.
   if (getCXXABI().isInlineInitializedStaticDataMemberLinkOnce() &&
       isa<VarDecl>(D) &&
       isVarDeclInlineInitializedStaticDataMember(cast<VarDecl>(D)))
     return llvm::GlobalValue::LinkOnceODRLinkage;
 
   // C++ doesn't have tentative definitions and thus cannot have common

test/CodeGenCXX/dllimport-members.cpp

 // Import special member functions.
 struct ImportSpecials {
   // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportSpecials* @"\01??0ImportSpecials@@QAE@XZ"(%struct.ImportSpecials* returned)
   // M64-DAG: declare dllimport                %struct.ImportSpecials* @"\01??0ImportSpecials@@QEAA@XZ"(%struct.ImportSpecials* returned)
   // G32-DAG: declare dllimport x86_thiscallcc void                    @_ZN14ImportSpecialsC1Ev(%struct.ImportSpecials*)
   // G64-DAG: declare dllimport                void                    @_ZN14ImportSpecialsC1Ev(%struct.ImportSpecials*)
   __declspec(dllimport) ImportSpecials();
 
-  // FIXME: MSVC emits ??1ImportSpecials@@{{QAE|QEAA}}@XZ here.
-  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportSpecials@@QAE@XZ"(%struct.ImportSpecials*)
-  // M64-DAG: declare dllimport                void @"\01??_DImportSpecials@@QEAA@XZ"(%struct.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*)
   // G32-DAG: declare dllimport x86_thiscallcc void                    @_ZN14ImportSpecialsD1Ev(%struct.ImportSpecials*)
   // G64-DAG: declare dllimport                void                    @_ZN14ImportSpecialsD1Ev(%struct.ImportSpecials*)
   __declspec(dllimport) ~ImportSpecials() {}
 
   // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportSpecials* @"\01??0ImportSpecials@@QAE@ABU0@@Z"(%struct.ImportSpecials* returned, %struct.ImportSpecials*)
   // M64-DAG: declare dllimport                %struct.ImportSpecials* @"\01??0ImportSpecials@@QEAA@AEBU0@@Z"(%struct.ImportSpecials* returned, %struct.ImportSpecials*)
   // G32-DAG: declare dllimport x86_thiscallcc void                    @_ZN14ImportSpecialsC1ERKS_(%struct.ImportSpecials*, %struct.ImportSpecials*)
   // G64-DAG: declare dllimport                void                    @_ZN14ImportSpecialsC1ERKS_(%struct.ImportSpecials*, %struct.ImportSpecials*)
struct ImportInlineSpecials {
   // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportInlineSpecials* @"\01??0ImportInlineSpecials@@QAE@XZ"(%struct.ImportInlineSpecials* returned)
   // M64-DAG: declare dllimport                %struct.ImportInlineSpecials* @"\01??0ImportInlineSpecials@@QEAA@XZ"(%struct.ImportInlineSpecials* returned)
   // G32-DAG: declare dllimport x86_thiscallcc void @_ZN20ImportInlineSpecialsC1Ev(%struct.ImportInlineSpecials*)
   // G64-DAG: declare dllimport                void @_ZN20ImportInlineSpecialsC1Ev(%struct.ImportInlineSpecials*)
   // MO1-DAG: define available_externally dllimport x86_thiscallcc %struct.ImportInlineSpecials* @"\01??0ImportInlineSpecials@@QAE@XZ"(
   // GO1-DAG: define available_externally dllimport x86_thiscallcc void @_ZN20ImportInlineSpecialsC1Ev(
   __declspec(dllimport) ImportInlineSpecials() {}
 
-  // FIXME: MSVC emits ??1ImportInlineSpecials@@{{QAE|QEAA}}@XZ here.
-  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportInlineSpecials@@QAE@XZ"(%struct.ImportInlineSpecials*)
-  // M64-DAG: declare dllimport                void @"\01??_DImportInlineSpecials@@QEAA@XZ"(%struct.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*)
   // G32-DAG: declare dllimport x86_thiscallcc void @_ZN20ImportInlineSpecialsD1Ev(%struct.ImportInlineSpecials*)
   // G64-DAG: declare dllimport                void @_ZN20ImportInlineSpecialsD1Ev(%struct.ImportInlineSpecials*)
-  // MO1-DAG: define available_externally dllimport x86_thiscallcc void @"\01??_DImportInlineSpecials@@QAE@XZ"(
+  // MO1-DAG: define available_externally dllimport x86_thiscallcc void @"\01??1ImportInlineSpecials@@QAE@XZ"(
   // GO1-DAG: define available_externally dllimport x86_thiscallcc void @_ZN20ImportInlineSpecialsD1Ev(
   __declspec(dllimport) ~ImportInlineSpecials() {}
 
   // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportInlineSpecials* @"\01??0ImportInlineSpecials@@QAE@ABU0@@Z"(%struct.ImportInlineSpecials* returned, %struct.ImportInlineSpecials*)
   // M64-DAG: declare dllimport                %struct.ImportInlineSpecials* @"\01??0ImportInlineSpecials@@QEAA@AEBU0@@Z"(%struct.ImportInlineSpecials* returned, %struct.ImportInlineSpecials*)
   // G32-DAG: declare dllimport x86_thiscallcc void @_ZN20ImportInlineSpecialsC1ERKS_(%struct.ImportInlineSpecials*, %struct.ImportInlineSpecials*)
   // G64-DAG: declare dllimport                void @_ZN20ImportInlineSpecialsC1ERKS_(%struct.ImportInlineSpecials*, %struct.ImportInlineSpecials*)
   // MO1-DAG: define available_externally dllimport x86_thiscallcc %struct.ImportInlineSpecials* @"\01??0ImportInlineSpecials@@QAE@ABU0@@Z"(
struct ImportDefaulted {
   // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportDefaulted* @"\01??0ImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted* returned)
   // M64-DAG: declare dllimport                %struct.ImportDefaulted* @"\01??0ImportDefaulted@@QEAA@XZ"(%struct.ImportDefaulted* returned)
   // G32-DAG: declare dllimport x86_thiscallcc void                     @_ZN15ImportDefaultedC1Ev(%struct.ImportDefaulted*)
   // G64-DAG: declare dllimport                void                     @_ZN15ImportDefaultedC1Ev(%struct.ImportDefaulted*)
   // MO1-DAG: define available_externally dllimport x86_thiscallcc %struct.ImportDefaulted* @"\01??0ImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted* returned %this)
   // GO1-DAG: define available_externally dllimport x86_thiscallcc void @_ZN15ImportDefaultedC1Ev(%struct.ImportDefaulted* %this)
   __declspec(dllimport) ImportDefaulted() = default;
 
-  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted*)
-  // M64-DAG: declare dllimport                void @"\01??_DImportDefaulted@@QEAA@XZ"(%struct.ImportDefaulted*)
+  // M32-DAG: declare dllimport x86_thiscallcc void @"\01??1ImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted*)
+  // M64-DAG: declare dllimport                void @"\01??1ImportDefaulted@@QEAA@XZ"(%struct.ImportDefaulted*)
   // G32-DAG: declare dllimport x86_thiscallcc void @_ZN15ImportDefaultedD1Ev(%struct.ImportDefaulted*)
   // G64-DAG: declare dllimport                void @_ZN15ImportDefaultedD1Ev(%struct.ImportDefaulted*)
-  // MO1-DAG: define available_externally dllimport x86_thiscallcc void @"\01??_DImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted* %this)
+  // MO1-DAG: define available_externally dllimport x86_thiscallcc void @"\01??1ImportDefaulted@@QAE@XZ"(%struct.ImportDefaulted* %this)
   // GO1-DAG: define available_externally dllimport x86_thiscallcc void @_ZN15ImportDefaultedD1Ev(%struct.ImportDefaulted* %this)
   __declspec(dllimport) ~ImportDefaulted() = default;
 
   // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportDefaulted* @"\01??0ImportDefaulted@@QAE@ABU0@@Z"(%struct.ImportDefaulted* returned, %struct.ImportDefaulted*)
   // M64-DAG: declare dllimport                %struct.ImportDefaulted* @"\01??0ImportDefaulted@@QEAA@AEBU0@@Z"(%struct.ImportDefaulted* returned, %struct.ImportDefaulted*)
   // G32-DAG: declare dllimport x86_thiscallcc void                     @_ZN15ImportDefaultedC1ERKS_(%struct.ImportDefaulted*, %struct.ImportDefaulted*)
   // G64-DAG: declare dllimport                void                     @_ZN15ImportDefaultedC1ERKS_(%struct.ImportDefaulted*, %struct.ImportDefaulted*)
   // MO1-DAG: define available_externally dllimport x86_thiscallcc %struct.ImportDefaulted* @"\01??0ImportDefaulted@@QAE@ABU0@@Z"(%struct.ImportDefaulted* returned %this, %struct.ImportDefaulted*)

 };
 
 // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportDefaultedDefs* @"\01??0ImportDefaultedDefs@@QAE@XZ"(%struct.ImportDefaultedDefs* returned)
 // M64-DAG: declare dllimport                %struct.ImportDefaultedDefs* @"\01??0ImportDefaultedDefs@@QEAA@XZ"(%struct.ImportDefaultedDefs* returned)
 // G32-DAG: declare dllimport x86_thiscallcc void                         @_ZN19ImportDefaultedDefsC1Ev(%struct.ImportDefaultedDefs*)
 // G64-DAG: declare dllimport                void                         @_ZN19ImportDefaultedDefsC1Ev(%struct.ImportDefaultedDefs*)
 __declspec(dllimport) ImportDefaultedDefs::ImportDefaultedDefs() = default;
 
-// FIXME: MSVC emits ??1ImportDefaultedDefs@@{{QAE|QEAA}}@XZ here.
-// M32-DAG: declare dllimport x86_thiscallcc void @"\01??_DImportDefaultedDefs@@QAE@XZ"(%struct.ImportDefaultedDefs*)
-// M64-DAG: declare dllimport                void @"\01??_DImportDefaultedDefs@@QEAA@XZ"(%struct.ImportDefaultedDefs*)
+// M32-DAG: declare dllimport x86_thiscallcc void @"\01??1ImportDefaultedDefs@@QAE@XZ"(%struct.ImportDefaultedDefs*)
+// M64-DAG: declare dllimport                void @"\01??1ImportDefaultedDefs@@QEAA@XZ"(%struct.ImportDefaultedDefs*)
 // G32-DAG: declare dllimport x86_thiscallcc void @_ZN19ImportDefaultedDefsD1Ev(%struct.ImportDefaultedDefs*)
 // G64-DAG: declare dllimport                void @_ZN19ImportDefaultedDefsD1Ev(%struct.ImportDefaultedDefs*)
 __declspec(dllimport) ImportDefaultedDefs::~ImportDefaultedDefs() = default;
 
 // M32-DAG: declare dllimport x86_thiscallcc %struct.ImportDefaultedDefs* @"\01??0ImportDefaultedDefs@@QAE@ABU0@@Z"(%struct.ImportDefaultedDefs* returned, %struct.ImportDefaultedDefs*)
 // M64-DAG: declare dllimport                %struct.ImportDefaultedDefs* @"\01??0ImportDefaultedDefs@@QEAA@AEBU0@@Z"(%struct.ImportDefaultedDefs* returned, %struct.ImportDefaultedDefs*)
 // G32-DAG: declare dllimport x86_thiscallcc void @_ZN19ImportDefaultedDefsC1ERKS_(%struct.ImportDefaultedDefs*, %struct.ImportDefaultedDefs*)
 // G64-DAG: declare dllimport                void @_ZN19ImportDefaultedDefsC1ERKS_(%struct.ImportDefaultedDefs*, %struct.ImportDefaultedDefs*)