[VPlan] Simplify code in single scalar transform code (NFC).

Adjust code as suggested post-commit 3b7b95f.

3b7b95f#r160997427

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -1220,9 +1220,9 @@ static void narrowToSingleScalarRecipes(VPlan &Plan) {
   for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
            vp_depth_first_shallow(Plan.getVectorLoopRegion()->getEntry()))) {
     for (VPRecipeBase &R : make_early_inc_range(reverse(*VPBB))) {
-      auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
-      if (!RepR && !isa<VPWidenRecipe, VPWidenSelectRecipe>(&R))
+      if (!isa<VPWidenRecipe, VPWidenSelectRecipe, VPReplicateRecipe>(&R))
         continue;
+      auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
       if (RepR && (RepR->isSingleScalar() || RepR->isPredicated()))
         continue;
 

llvm/lib/Transforms/Vectorize/VPlanUtils.h

@@ -69,14 +69,13 @@ inline bool isSingleScalar(const VPValue *VPV) {
     return Rep->isSingleScalar() || (PreservesUniformity(Rep->getOpcode()) &&
                                      all_of(Rep->operands(), isSingleScalar));
   }
-  if (isa<VPWidenGEPRecipe, VPDerivedIVRecipe, VPBlendRecipe>(VPV))
+  if (isa<VPWidenGEPRecipe, VPDerivedIVRecipe, VPBlendRecipe,
+          VPWidenSelectRecipe>(VPV))
     return all_of(VPV->getDefiningRecipe()->operands(), isSingleScalar);
   if (auto *WidenR = dyn_cast<VPWidenRecipe>(VPV)) {
     return PreservesUniformity(WidenR->getOpcode()) &&
            all_of(WidenR->operands(), isSingleScalar);
   }
-  if (auto *WidenR = dyn_cast<VPWidenSelectRecipe>(VPV))
-    return all_of(WidenR->operands(), isSingleScalar);
   if (auto *VPI = dyn_cast<VPInstruction>(VPV))
     return VPI->isSingleScalar() || VPI->isVectorToScalar() ||
            (PreservesUniformity(VPI->getOpcode()) &&