[llvm] [LV] Vectorize Epilogues for loops with small VF but high IC (PR #108190)

[David Sherwood via llvm-commits]

================
@@ -4677,7 +4683,11 @@ VectorizationFactor LoopVectorizationPlanner::selectEpilogueVectorizationFactor(
     return Result;
   }
 
-  if (!CM.isEpilogueVectorizationProfitable(MainLoopVF)) {
+  unsigned Multiplier = IC;
+  if (MainLoopVF.isScalable())
+    Multiplier = getVScaleForTuning(OrigLoop, TTI).value_or(1);
----------------
david-arm wrote:

Hi @fhahn can you verify this as well? I think it should be one of the following:

```
  unsigned Multiplier = IC;
  if (MainLoopVF.isScalable())
    Multiplier *= getVScaleForTuning(OrigLoop, TTI).value_or(1);
```

or 

```
  unsigned Multiplier = 1;
  if (MainLoopVF.isScalable())
    Multiplier = getVScaleForTuning(OrigLoop, TTI).value_or(1);
```


https://github.com/llvm/llvm-project/pull/108190