1 files changed, 33 insertions, 2 deletions
diff --git a/clang/lib/CIR/CodeGen/CIRGenVTables.cpp b/clang/lib/CIR/CodeGen/CIRGenVTables.cpp
index 94d856b..84f5977 100644
--- a/clang/lib/CIR/CodeGen/CIRGenVTables.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenVTables.cpp
@@ -327,9 +327,40 @@ cir::GlobalLinkageKind CIRGenModule::getVTableLinkage(const CXXRecordDecl *rd) {
       llvm_unreachable("Should not have been asked to emit this");
     }
   }
+  // -fapple-kext mode does not support weak linkage, so we must use
+  // internal linkage.
+  if (astContext.getLangOpts().AppleKext)
+    return cir::GlobalLinkageKind::InternalLinkage;
+
+  auto discardableODRLinkage = cir::GlobalLinkageKind::LinkOnceODRLinkage;
+  auto nonDiscardableODRLinkage = cir::GlobalLinkageKind::WeakODRLinkage;
+  if (rd->hasAttr<DLLExportAttr>()) {
+    // Cannot discard exported vtables.
+    discardableODRLinkage = nonDiscardableODRLinkage;
+  } else if (rd->hasAttr<DLLImportAttr>()) {
+    // Imported vtables are available externally.
+    discardableODRLinkage = cir::GlobalLinkageKind::AvailableExternallyLinkage;
+    nonDiscardableODRLinkage =
+        cir::GlobalLinkageKind::AvailableExternallyLinkage;
+  }
+
+  switch (rd->getTemplateSpecializationKind()) {
+  case TSK_Undeclared:
+  case TSK_ExplicitSpecialization:
+  case TSK_ImplicitInstantiation:
+    return discardableODRLinkage;
+
+  case TSK_ExplicitInstantiationDeclaration: {
+    errorNYI(rd->getSourceRange(),
+             "getVTableLinkage: explicit instantiation declaration");
+    return cir::GlobalLinkageKind::ExternalLinkage;
+  }
+
+  case TSK_ExplicitInstantiationDefinition:
+    return nonDiscardableODRLinkage;
+  }
 
-  errorNYI(rd->getSourceRange(), "getVTableLinkage: no key function");
-  return cir::GlobalLinkageKind::ExternalLinkage;
+  llvm_unreachable("Invalid TemplateSpecializationKind!");
 }
 
 cir::GlobalOp CIRGenVTables::getAddrOfVTT(const CXXRecordDecl *rd) {