[MS ABI] Don't emit RTTI descriptors for dllimport vtables

A dllimport'd vtable always points one past the RTTI data, this means
that the initializer will never end up referencing the data.  Our
emission is a harmless waste.

llvm-svn: 260062

2 files changed, 5 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 71fc207e595..4cd4f8533b7 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1567,7 +1567,9 @@ void MicrosoftCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
     if (VTable->hasInitializer())
       continue;
 
-    llvm::Constant *RTTI = getContext().getLangOpts().RTTIData
+    llvm::Constant *RTTI = getContext().getLangOpts().RTTIData &&
+                                   VTable->getDLLStorageClass() !=
+                                       llvm::GlobalValue::DLLImportStorageClass
                                ? getMSCompleteObjectLocator(RD, Info)
                                : nullptr;
 
diff --git a/clang/test/CodeGenCXX/microsoft-abi-vftables.cpp b/clang/test/CodeGenCXX/microsoft-abi-vftables.cpp
index 340675b188d..f32bff09a8a 100644
--- a/clang/test/CodeGenCXX/microsoft-abi-vftables.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-vftables.cpp
@@ -4,6 +4,8 @@
 // RTTI-DAG: $"\01??_7S@@6B@" = comdat largest
 // RTTI-DAG: $"\01??_7V@@6B@" = comdat largest
 
+// RTTI-NOT: @"\01??_R4U@@6B@"
+
 struct S {
   virtual ~S();
 } s;