Revert "[ThinLTO] Do not duplicate import a function that is actually defined in the current module" (#111919)

Reverts #110064

Author: huangjd

llvm/lib/Linker/IRMover.cpp

@@ -595,15 +595,11 @@ Value *IRLinker::materialize(Value *V, bool ForIndirectSymbol) {
   if (!SGV)
     return nullptr;
 
-  // If SGV is from dest, it was already materialized when dest was loaded.
-  if (SGV->getParent() == &DstM)
-    return nullptr;
-
   // When linking a global from other modules than source & dest, skip
   // materializing it because it would be mapped later when its containing
   // module is linked. Linking it now would potentially pull in many types that
   // may not be mapped properly.
-  if (SGV->getParent() != SrcM.get())
+  if (SGV->getParent() != &DstM && SGV->getParent() != SrcM.get())
     return nullptr;
 
   Expected<Constant *> NewProto = linkGlobalValueProto(SGV, ForIndirectSymbol);