Emit available_externally vtables opportunistically

Summary:
We can emit vtable definition having inline function
if they are all emitted.

Reviewers: rjmccall, rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D33437

llvm-svn: 304394
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 4cacf49..ff5aca8 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -3756,6 +3756,9 @@
   if (llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(MangledName))
     return llvm::ConstantExpr::getBitCast(GV, CGM.Int8PtrTy);
 
+  // Note for the future: If we would ever like to do deferred emission of
+  // RTTI, check if emitting vtables opportunistically need any adjustment.
+
   // Compute the fields for the TypeDescriptor.
   SmallString<256> TypeInfoString;
   {