[llvm] [IR] Avoid self-referencing values caused by PHI node removal (PR #129501)

[Matt Arsenault via llvm-commits]

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@@ -381,6 +385,26 @@ bool JumpThreadingPass::runImpl(Function &F_, FunctionAnalysisManager *FAM_,
   return EverChanged;
 }
 
+SmallVector<BasicBlock *, 32>
+JumpThreadingPass::unreachableFromBB(BasicBlock *BB, DomTreeUpdater *DTU) {
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arsenm wrote:

This feels like a heavy hammer, than you also shouldn't need to reimplement. Can you just skip any block where !DT.isReachableFromEntry?

https://github.com/llvm/llvm-project/pull/129501