Don't add irrelevant items to queue in DwarfCompileUnit::createScopeChildrenDIE (NFC)

Instead of popping them and then immediately throwing them away, we can
just filter out globals and items in different scopes before adding them
to WorkList. Shouldn't change anything but keep the queue smaller.

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D113864

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -980,9 +980,7 @@ sortLocalVars(SmallVectorImpl<DbgVariable *> &Input) {
     bool visitedAllDependencies = Item.getInt();
     WorkList.pop_back();
 
-    // Dependency is in a different lexical scope or a global.
-    if (!Var)
-      continue;
+    assert(Var);
 
     // Already handled.
     if (Visited.count(Var))
@@ -1006,8 +1004,10 @@ sortLocalVars(SmallVectorImpl<DbgVariable *> &Input) {
     // visited again after all of its dependencies are handled.
     WorkList.push_back({Var, 1});
     for (auto *Dependency : dependencies(Var)) {
-      auto Dep = dyn_cast_or_null<const DILocalVariable>(Dependency);
-      WorkList.push_back({DbgVar[Dep], 0});
+      // Don't add dependency if it is in a different lexical scope or a global.
+      if (const auto *Dep = dyn_cast<const DILocalVariable>(Dependency))
+        if (DbgVariable *Var = DbgVar.lookup(Dep))
+          WorkList.push_back({Var, 0});
     }
   }
   return Result;