[llvm] [VPlan] Impl VPlan-based pattern match for ExtendedRed and MulAccRed (PR #113903)

[Florian Hahn via llvm-commits]

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@@ -9549,6 +9488,21 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
   // Adjust the recipes for any inloop reductions.
   adjustRecipesForReductions(Plan, RecipeBuilder, Range.Start);
 
+  // Transform recipes to abstract recipes if it is leagal and beneficial and
+  // clamp the range for better cost estimation.
+  // TODO: Enable following transform when the EVL-version of extended-reduction
+  // and mulacc-reduction are implemented.
+  if (!CM.foldTailWithEVL()) {
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fhahn wrote:

Why do we need to special case this for EVL? Shouldn't the cost-model tell us that the combined reductions aren't profitable?

https://github.com/llvm/llvm-project/pull/113903