[llvm] [LoopInfo] Do not enqueue unreachable nodes; fix infinite loop (PR #214832)

[Alexis Engelke via llvm-commits]

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@@ -664,7 +664,9 @@ void LoopInfoBase<BlockT, LoopT>::analyze(
       // Whatever reaches a latch without passing the header is in the loop.
       for (unsigned I = 0; I != Worklist.size(); ++I)
         for (BlockT *Pred : inverse_children<BlockT *>(Worklist[I]))
-          enqueue(Pred);
+          //  Do not enqueue any unreachable nodes
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aengelke wrote:

```suggestion
          // Do not enqueue any unreachable nodes.
```

https://github.com/llvm/llvm-project/pull/214832