Revert "Revert r260388 "[MS ABI] Never reference dllimport'd vtables""
This reverts commit r260449.
We would supress our emission of vftable definitions if we thought
another translation unit would provide the definition because we saw an
explicit instantiation declaration. This is not the case with
dllimport, we want to synthesize a definition of the vftable regardless.
This fixes PR26569.
llvm-svn: 260548
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 2870a91..2567aa9 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1673,7 +1673,16 @@
SmallString<256> VFTableName;
mangleVFTableName(getMangleContext(), RD, VFPtr, VFTableName);
- llvm::GlobalValue::LinkageTypes VFTableLinkage = CGM.getVTableLinkage(RD);
+ // Classes marked __declspec(dllimport) need vftables generated on the
+ // import-side in order to support features like constexpr. No other
+ // translation unit relies on the emission of the local vftable, translation
+ // units are expected to generate them as needed.
+ //
+ // Because of this unique behavior, we maintain this logic here instead of
+ // getVTableLinkage.
+ llvm::GlobalValue::LinkageTypes VFTableLinkage =
+ RD->hasAttr<DLLImportAttr>() ? llvm::GlobalValue::LinkOnceODRLinkage
+ : CGM.getVTableLinkage(RD);
bool VFTableComesFromAnotherTU =
llvm::GlobalValue::isAvailableExternallyLinkage(VFTableLinkage) ||
llvm::GlobalValue::isExternalLinkage(VFTableLinkage);
@@ -1746,9 +1755,7 @@
if (C)
VTable->setComdat(C);
- if (RD->hasAttr<DLLImportAttr>())
- VFTable->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
- else if (RD->hasAttr<DLLExportAttr>())
+ if (RD->hasAttr<DLLExportAttr>())
VFTable->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
VFTablesMap[ID] = VFTable;