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

[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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paperchalice wrote:

Currently all update operations are based on [`cfg::Update`](https://llvm.org/doxygen/classllvm_1_1cfg_1_1Update.html). If we extend `cfg::Update` directly e.g. add a new kind `UpdateKind::Split`, then it is duplicated with two insertions and deletion, and causes some compiler warnings.


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