[llvm] [NFC][LV] Introduce enums for uncountable exit detail and style (PR #184808)

[Graham Hunter via llvm-commits]

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@@ -77,6 +77,24 @@ typedef unsigned ID;
 
 using VPlanPtr = std::unique_ptr<VPlan>;
 
+// Different methods of handling early exits.
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huntergr-arm wrote:

done.

https://github.com/llvm/llvm-project/pull/184808