[llvm] [NFC][LLVM][LoopVectorize] Change getSmallBestKnownTC to return an ElementCount. (PR #141793)

[David Sherwood via llvm-commits]

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@@ -823,6 +823,10 @@ class ScalarEvolution {
   /// than the backedge taken count for the loop.
   LLVM_ABI unsigned getSmallConstantTripCount(const Loop *L);
 
+  /// A version of getSmallConstantTripCount that returns as an ElementCount to
+  /// include loops whose trip count is a function of llvm.vscale().
+  ElementCount getSmallConstantRuntimeTripCount(const Loop *L);
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david-arm wrote:

I think this need the same `LLVM_ABI` prefix as above.

https://github.com/llvm/llvm-project/pull/141793