[clang] Don't emit type tests for dllexport/import classes

[aeubanks]

Summary

According to https://clang.llvm.org/docs/LTOVisibility.html, classes on
Windows with dllimport/export receive public LTO visibility and
therefore should not participate in WPD.

[aeubanks]

ping

[aeubanks]

ping

[aeubanks]

ping

[pcc]

Can't the code in CodeGenModule::HasHiddenLTOVisibility be moved here instead of duplicating it?

[aeubanks]

move HasHiddenLTOVisibility DLL code to AlwaysHasLTOVisibilityPublic

[aeubanks]

ping

[pcc]

LGTM

clang/lib/CodeGen/CGVTables.cpp

else if (shouldOpportunisticallyEmitVTables())
       OpportunisticVTables.push_back(RD);
 
   assert(savedSize == DeferredVTables.size() &&
          "deferred extra vtables during vtable emission?");
   DeferredVTables.clear();
 }
 
 bool CodeGenModule::AlwaysHasLTOVisibilityPublic(const CXXRecordDecl *RD) {
-  if (RD->hasAttr<LTOVisibilityPublicAttr>() || RD->hasAttr<UuidAttr>())
+  if (RD->hasAttr<LTOVisibilityPublicAttr>() || RD->hasAttr<UuidAttr>() ||
+      RD->hasAttr<DLLExportAttr>() || RD->hasAttr<DLLImportAttr>())
     return true;
 
   if (!getCodeGenOpts().LTOVisibilityPublicStd)
     return false;
 
   const DeclContext *DC = RD;
   while (true) {
     auto *D = cast<Decl>(DC);
bool CodeGenModule::AlwaysHasLTOVisibilityPublic(const CXXRecordDecl *RD) {
   return false;
 }
 
 bool CodeGenModule::HasHiddenLTOVisibility(const CXXRecordDecl *RD) {
   LinkageInfo LV = RD->getLinkageAndVisibility();
   if (!isExternallyVisible(LV.getLinkage()))
     return true;
 
-  if (getTriple().isOSBinFormatCOFF()) {
-    if (RD->hasAttr<DLLExportAttr>() || RD->hasAttr<DLLImportAttr>())
-      return false;
-  } else {
-    if (LV.getVisibility() != HiddenVisibility)
-      return false;
-  }
+  if (!getTriple().isOSBinFormatCOFF() &&
+      LV.getVisibility() != HiddenVisibility)
 
   return !AlwaysHasLTOVisibilityPublic(RD);
 }
 
 llvm::GlobalObject::VCallVisibility CodeGenModule::GetVCallVisibilityLevel(
     const CXXRecordDecl *RD, llvm::DenseSet<const CXXRecordDecl *> &Visited) {
   // If we have already visited this RD (which means this is a recursive call
   // since the initial call should have an empty Visited set), return the max

clang/test/CodeGenCXX/lto-visibility-inference.cpp

void f(C1 *c1, C2 *c2, C3 *c3, C4 *c4, C5 *c5, C6 *c6, std::C7 *c7,
        std::C7::C8 *c8, stdext::C9 *c9, other::C10 *c10) {
   // ITANIUM: type.test{{.*}}!"_ZTS2C1"
   // MS: type.test{{.*}}!"?AUC1@@"
   c1->f();
   // ITANIUM: type.test{{.*}}!"_ZTS2C2"
   // MS: type.test{{.*}}!"?AUC2@@"
   c2->f();
   // ITANIUM: type.test{{.*}}!"_ZTS2C3"
-  // MS: type.test{{.*}}!"?AUC3@@"
+  // MS-NOT: type.test{{.*}}!"?AUC3@@"
   c3->f();
   // ITANIUM: type.test{{.*}}!"_ZTS2C4"
-  // MS: type.test{{.*}}!"?AUC4@@"
+  // MS-NOT: type.test{{.*}}!"?AUC4@@"
   c4->f();
   // ITANIUM-NOT: type.test{{.*}}!"_ZTS2C5"
   // MS-NOT: type.test{{.*}}!"?AUC5@@"
   c5->f();
   // ITANIUM-NOT: type.test{{.*}}!"_ZTS2C6"
   // MS-NOT: type.test{{.*}}!"?AUC6@@"
   c6->f();
   // ITANIUM: type.test{{.*}}!"_ZTSSt2C7"