[llvm] [llvm] Replace unordered_{map,set} with Dense{Map,Set}/SmallPtrSet (PR #202222)

[Alexis Engelke via llvm-commits]

================
@@ -1636,9 +1636,9 @@ class DisplayNode : public DisplayElement {
       : DisplayElement(Colour), Content(Content) {}
 
   // Iterator to the child nodes.  Required by GraphWriter.
-  using ChildIterator = std::unordered_set<DisplayNode *>::const_iterator;
-  ChildIterator children_begin() const { return Children.cbegin(); }
-  ChildIterator children_end() const { return Children.cend(); }
+  using ChildIterator = SmallPtrSet<DisplayNode *, 0>::const_iterator;
----------------
aengelke wrote:

```suggestion
  using ChildIterator = SmallPtrSetImpl<DisplayNode *>::const_iterator;
```

https://github.com/llvm/llvm-project/pull/202222