[C++20] [Modules] Handling template declare with debug info

It looks an overlook that debug info can't play well with
explicit template instantiation. Tested in donwstream for years. I just
forgot to upstream it.

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index 2897ccd..0b6e830 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -1138,7 +1138,9 @@ CodeGenModule::getVTableLinkage(const CXXRecordDecl *RD) {
                  llvm::Function::InternalLinkage;
 
       case TSK_ExplicitInstantiationDeclaration:
-        llvm_unreachable("Should not have been asked to emit this");
+        return IsExternalDefinition
+                   ? llvm::GlobalVariable::AvailableExternallyLinkage
+                   : llvm::GlobalVariable::ExternalLinkage;
       }
   }