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

[David Blaikie 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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dwblaikie wrote:

But this logic (using available externally definitions) is already built into the modules-codegen work (though it's probably only for functions, I guess it might not be in a place general enough to apply to variables as well - if it either can't be generalized in that way, or even if it just isn't suffiicently general now, I agree that it'd be a separate patch, but probably one worth doing) - again, if/where possible, it'd be nice if these things aligned/involved fewer special cases and inconsistencies.

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