[llvm] [Utils][UnifyLoopExits] Avoid costly updates if nothing changed (PR #129179)

[Matt Arsenault via llvm-commits]

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@@ -110,7 +110,9 @@ struct ControlFlowHub {
     Branches.emplace_back(BB, Succ0, Succ1);
   }
 
-  BasicBlock *
+  /// Return the unified loop exist block and a flag indicating if the CFG was
+  /// changed at all.
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arsenm wrote:

"exist block"?

https://github.com/llvm/llvm-project/pull/129179