[llvm] [LoopIdiom] Update strlen idiom body loop condition to be clean up by LoopDeletion (PR #134906)

[Michael Kruse via llvm-commits]

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@@ -1804,6 +1808,11 @@ bool LoopIdiomRecognize::recognizeAndInsertStrLen() {
   // up by later passes
   for (PHINode *PN : Cleanup)
     RecursivelyDeleteDeadPHINode(PN);
+
+  ConstantInt *NewLoopCond = LoopTerm->getSuccessor(0) == LoopBody
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Meinersbur wrote:

Consider adding a comment explaining that this intends to make the old code unreachable/dead.

Add `assert` that at least one of the successors is `LoopBody`?

https://github.com/llvm/llvm-project/pull/134906