[VPlan] Compute cost of scalar (U|S)Div, (U|S)Rem in computeCost (NFCI).

Directly compute the cost of UDiv, SDiv, URem, SRem in VPlan.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -3151,9 +3151,23 @@ InstructionCost VPReplicateRecipe::computeCost(ElementCount VF,
   case Instruction::Xor:
   case Instruction::ICmp:
   case Instruction::FCmp:
+  case Instruction::Select:
     return *getCostForRecipeWithOpcode(getOpcode(), ElementCount::getFixed(1),
                                        Ctx) *
            (isSingleScalar() ? 1 : VF.getFixedValue());
+  case Instruction::SDiv:
+  case Instruction::UDiv:
+  case Instruction::SRem:
+  case Instruction::URem: {
+    InstructionCost ScalarCost = *getCostForRecipeWithOpcode(
+        getOpcode(), ElementCount::getFixed(1), Ctx);
+    if (isSingleScalar())
+      return ScalarCost;
+
+    return ScalarCost * VF.getFixedValue() +
+           Ctx.getScalarizationOverhead(Ctx.Types.inferScalarType(this),
+                                        to_vector(operands()), VF);
+  }
   case Instruction::Load:
   case Instruction::Store: {
     if (isSingleScalar()) {