[llvm] [DomTreeUpdater] Handle critical edge splitting (PR #100856)

[Jakub Kuderski via llvm-commits]

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@@ -146,8 +152,25 @@ class GenericDomTreeUpdater {
   /// 2. It is illegal to submit any update that has already been submitted,
   /// i.e., you are supposed not to insert an existent edge or delete a
   /// nonexistent edge.
+  /// 3. This kind updates are incompatible with critical edge splitting
+  /// updates, call this method will apply all critical edge updates in
+  /// lazy mode. It is not recommended to interleave applyUpdates and
+  /// applyUpdatesForCriticalEdgeSplitting.
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kuhar wrote:

I can't parse this sentence. Could you explain it in a bit more detail?

Specifically, it is not clear to me how to reconcile 'incompatible' with 'not recommended'. What happens if we do add edge splitting updates in eager and lazy mode?

https://github.com/llvm/llvm-project/pull/100856