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

[Matt Arsenault via llvm-commits]

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@@ -169,10 +169,16 @@ static bool unifyLoopExits(DominatorTree &DT, LoopInfo &LI, Loop *L) {
 
   SmallVector<BasicBlock *, 8> GuardBlocks;
   DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
-  BasicBlock *LoopExitBlock = CHub.finalize(
+  BasicBlock *LoopExitBlock;
+  bool ChangedCFG;
+  std::tie(LoopExitBlock, ChangedCFG) = CHub.finalize(
       &DTU, GuardBlocks, "loop.exit", MaxBooleansInControlFlowHub.getValue());
+//  if (!ChangedCFG)
+//    return false;
 
+  L->getHeader()->getParent()->dump();
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arsenm wrote:

leftover debug 

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