[clang] [CodeGen] Add conditional to module cloning in bitcode linking (PR #72478)

[Jacob Lambert via cfe-commits]

================
@@ -251,32 +255,50 @@ bool BackendConsumer::LinkInModules(llvm::Module *M, bool ShouldLinkFiles) {
       }
 
     CurLinkModule = LM.Module.get();
-
-    // TODO: If CloneModule() is updated to support cloning of unmaterialized
-    // modules, we can remove this
     bool Err;
-    if (Error E = CurLinkModule->materializeAll())
-      return false;
 
     // Create a Clone to move to the linker, which preserves the original
     // linking modules, allowing them to be linked again in the future
-    // TODO: Add a ShouldCleanup option to make Cloning optional. When
-    // set, we can pass the original modules to the linker for cleanup
-    std::unique_ptr<llvm::Module> Clone = llvm::CloneModule(*LM.Module);
+    if (ClRelinkBuiltinBitcodePostop) {
----------------
lamb-j wrote:

Open to suggestions on a cleaner way to do this. Ideally we could do something like the following, instead of duplicating the functionality twice:

```
std::unique_ptr<llvm::Module> LinkMod;

if (ClRelinkBuiltinBitcodePostop)
  LinkMod = Clone
else
  LinkMod = Original

// Link with LinkMod
```

But due to `llvm::Module` not having a default constructor, I haven't figured out a way to do something like the above. That is, creating a single variable that can represent both the Original and the Clone, and set it depending on the provided boolean.

https://github.com/llvm/llvm-project/pull/72478