[llvm] [VPlan] Compute interleave count for VPlan. (PR #149702)

[via llvm-commits]

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@@ -4686,15 +4679,20 @@ LoopVectorizationCostModel::selectInterleaveCount(VPlan &Plan, ElementCount VF,
   // We don't attempt to perform interleaving for loops with uncountable early
   // exits because the VPInstruction::AnyOf code cannot currently handle
   // multiple parts.
-  if (Legal->hasUncountableEarlyExit())
+  if (Plan.hasEarlyExit())
     return 1;
 
-  const bool HasReductions = !Legal->getReductionVars().empty();
+  const bool HasReductions =
+      any_of(Plan.getVectorLoopRegion()->getEntryBasicBlock()->phis(),
+             IsaPred<VPReductionPHIRecipe>);
 
   // If we did not calculate the cost for VF (because the user selected the VF)
   // then we calculate the cost of VF here.
   if (LoopCost == 0) {
-    LoopCost = expectedCost(VF);
+    if (VF.isScalar())
+      LoopCost = CM.expectedCost(VF);
+    else
+      LoopCost = cost(Plan, VF);
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ayalz wrote:

nit: trinary?

https://github.com/llvm/llvm-project/pull/149702