[llvm] [Support] Store dominator tree nodes in a vector (PR #101705)

[Nikita Popov via llvm-commits]

================
@@ -333,35 +336,71 @@ class DominatorTreeBase {
     if (!std::is_permutation(Roots.begin(), Roots.end(), Other.Roots.begin()))
       return true;
 
-    const DomTreeNodeMapType &OtherDomTreeNodes = Other.DomTreeNodes;
-    if (DomTreeNodes.size() != OtherDomTreeNodes.size())
-      return true;
-
-    for (const auto &DomTreeNode : DomTreeNodes) {
-      NodeT *BB = DomTreeNode.first;
-      typename DomTreeNodeMapType::const_iterator OI =
-          OtherDomTreeNodes.find(BB);
-      if (OI == OtherDomTreeNodes.end())
+    size_t NumNodes = 0;
+    // All node we have must exist and be equal in the other tree
----------------
nikic wrote:

```suggestion
    // All nodes we have must exist and be equal in the other tree.
```

https://github.com/llvm/llvm-project/pull/101705