[clang] [C++20] [Modules] [Itanium ABI] Generate the vtable in the module unit of dynamic classes (PR #75912)

[Eli Friedman via cfe-commits]

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@@ -1830,6 +1830,9 @@ void ItaniumCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
   if (VTable->hasInitializer())
     return;
 
+  if (RD->shouldEmitInExternalSource())
+    return;
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efriedma-quic wrote:

This check seems like it's at the wrong level; if we don't want a vtable, why are we calling this in the first place?

Also, even if the vtable is getting emitted somewhere else, we might want an available_externally vtable.

https://github.com/llvm/llvm-project/pull/75912