[llvm] [LoopUnroll] Allow expensive trip count emitting which is estimated to be infinite (PR #79869)

[Mircea Trofin via llvm-commits]

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@@ -330,6 +330,10 @@ getLoopEstimatedTripCount(Loop *L,
 bool setLoopEstimatedTripCount(Loop *L, unsigned EstimatedTripCount,
                                unsigned EstimatedLoopInvocationWeight);
 
+// Return true if loop's estimated trip count based on branch weight metadata is
+// infinite, i.e. weight ratio is X:0.
+bool isInfiniteTripCount(Loop *L);
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mtrofin wrote:

`const Loop& L`. `const` because you shouldn't need to mutate `L`, pass-by-reference to signal `nullptr` isn't something we expect handling.

https://github.com/llvm/llvm-project/pull/79869