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

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.

Reviewed By: pcc

Differential Revision: https://reviews.llvm.org/D129700

Author: aeubanks

clang/lib/CodeGen/CGVTables.cpp

@@ -1212,7 +1212,8 @@ void CodeGenModule::EmitDeferredVTables() {
 }
 
 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)
@@ -1239,13 +1240,9 @@ bool CodeGenModule::HasHiddenLTOVisibility(const CXXRecordDecl *RD) {
   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 false;
 
   return !AlwaysHasLTOVisibilityPublic(RD);
 }

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

@@ -74,10 +74,10 @@ void f(C1 *c1, C2 *c2, C3 *c3, C4 *c4, C5 *c5, C6 *c6, std::C7 *c7,
   // 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@@"