[NFC][Cloning] Simplify the flow in FindDebugInfoToIdentityMap (#129144)

Summary:
The new flow should make it more clear what is happening in cases of
Different of Cloned modules.

Test Plan:
ninja check-llvm-unit check-llvm

Author: artempyanykh

llvm/lib/Transforms/Utils/CloneFunction.cpp

@@ -160,32 +160,32 @@ MetadataSetTy
 llvm::FindDebugInfoToIdentityMap(CloneFunctionChangeType Changes,
                                  DebugInfoFinder &DIFinder,
                                  DISubprogram *SPClonedWithinModule) {
+  if (Changes >= CloneFunctionChangeType::DifferentModule)
+    return {};
+
+  if (DIFinder.subprogram_count() == 0)
+    assert(!SPClonedWithinModule &&
+           "Subprogram should be in DIFinder->subprogram_count()...");
+
   MetadataSetTy MD;
 
-  if (Changes < CloneFunctionChangeType::DifferentModule &&
-      DIFinder.subprogram_count() > 0) {
-    // Avoid cloning types, compile units, and (other) subprograms.
-    for (DISubprogram *ISP : DIFinder.subprograms()) {
-      if (ISP != SPClonedWithinModule)
-        MD.insert(ISP);
-    }
+  // Avoid cloning types, compile units, and (other) subprograms.
+  for (DISubprogram *ISP : DIFinder.subprograms())
+    if (ISP != SPClonedWithinModule)
+      MD.insert(ISP);
 
-    // If a subprogram isn't going to be cloned skip its lexical blocks as well.
-    for (DIScope *S : DIFinder.scopes()) {
-      auto *LScope = dyn_cast<DILocalScope>(S);
-      if (LScope && LScope->getSubprogram() != SPClonedWithinModule)
-        MD.insert(S);
-    }
+  // If a subprogram isn't going to be cloned skip its lexical blocks as well.
+  for (DIScope *S : DIFinder.scopes()) {
+    auto *LScope = dyn_cast<DILocalScope>(S);
+    if (LScope && LScope->getSubprogram() != SPClonedWithinModule)
+      MD.insert(S);
+  }
 
     for (DICompileUnit *CU : DIFinder.compile_units())
       MD.insert(CU);
 
     for (DIType *Type : DIFinder.types())
       MD.insert(Type);
-  } else {
-    assert(!SPClonedWithinModule &&
-           "Subprogram should be in DIFinder->subprogram_count()...");
-  }
 
   return MD;
 }