[llvm] [LV][NFC] Refactor structures used to maintain uncountable exit info (PR #123219)

[Florian Hahn via llvm-commits]

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@@ -391,25 +391,22 @@ class LoopVectorizationLegality {
 
   /// Returns true if the loop has an uncountable early exit, i.e. an
   /// uncountable exit that isn't the latch block.
-  bool hasUncountableEarlyExit() const { return HasUncountableEarlyExit; }
+  bool hasUncountableEarlyExit() const {
+    return getUncountableEdge().has_value();
+  }
 
   /// Returns the uncountable early exiting block.
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fhahn wrote:

```suggestion
  /// Returns the uncountable early exiting block, if there is a single one.
```

https://github.com/llvm/llvm-project/pull/123219