[llvm] [LV] Update forced epilogue VF options to allow different VFs than main. (PR #190393)

[via llvm-commits]

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@@ -7181,7 +7196,19 @@ LoopVectorizationPlanner::computeBestVF() {
   // If there is a single VPlan with a single VF, return it directly.
   VPlan &FirstPlan = *VPlans[0];
   if (VPlans.size() == 1 && size(FirstPlan.vectorFactors()) == 1)
-    return {{*FirstPlan.vectorFactors().begin(), 0, 0}, &FirstPlan};
+    return {VectorizationFactor(*FirstPlan.vectorFactors().begin(), 0, 0),
+            &FirstPlan};
+
+  ElementCount UserVF = Hints.getWidth();
+  if (EpilogueVectorizationForceVF > 1 && UserVF && hasPlanWithVF(UserVF)) {
+    [[maybe_unused]] ElementCount EpilogueVF =
+        ElementCount::getFixed(EpilogueVectorizationForceVF);
+    assert(*VPlans[0]->vectorFactors().begin() == EpilogueVF &&
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ayalz wrote:

Should be useful to have `getSingleVF()`.

https://github.com/llvm/llvm-project/pull/190393