[llvm] [LV] Allow setting scalable VFs for `-epilogue-vectorization-force-VF` (PR #205081)

[Benjamin Maxwell via llvm-commits]

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@@ -178,8 +178,9 @@ static cl::opt<bool> EnableEpilogueVectorization(
     "enable-epilogue-vectorization", cl::init(true), cl::Hidden,
     cl::desc("Enable vectorization of epilogue loops."));
 
-static cl::opt<unsigned> EpilogueVectorizationForceVF(
-    "epilogue-vectorization-force-VF", cl::init(1), cl::Hidden,
+static cl::opt<ElementCount> EpilogueVectorizationForceVF(
+    "epilogue-vectorization-force-VF", cl::init(ElementCount::getFixed(1)),
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MacDue wrote:

I've gone back to the previous check (i.e., don't allow `--epilogue-vectorization-force-VF=1`), as it does just duplicate the scalar loop. 

https://github.com/llvm/llvm-project/pull/205081