[LV] Use getMask() when printing recipe [NFCI]

[gilr]

Summary

Use dedicated API for getting the mask instead of duplicating it.

[fhahn]

LGTM

[gilr]

In D71964#1798095, @fhahn wrote:

LGTM

Thanks @fhahn !

llvm/lib/Transforms/Vectorize/VPlan.h

public:
 
   /// Method to support type inquiry through isa, cast, and dyn_cast.
   static inline bool classof(const VPRecipeBase *V) {
     return V->getVPRecipeID() == VPRecipeBase::VPWidenMemoryInstructionSC;
   }
 
   /// Return the mask used by this recipe. Note that a full mask is represented
   /// by a nullptr.
-  VPValue *getMask() {
+  VPValue *getMask() const {
     // Mask is the last operand.
     return User ? User->getOperand(User->getNumOperands() - 1) : nullptr;
   }
 
   /// Generate the wide load/store.
   void execute(VPTransformState &State) override;
 
   /// Print the recipe.

llvm/lib/Transforms/Vectorize/VPlan.cpp

void VPPredInstPHIRecipe::print(raw_ostream &O, const Twine &Indent) const {
   O << " +\n"
     << Indent << "\"PHI-PREDICATED-INSTRUCTION " << VPlanIngredient(PredInst)
     << "\\l\"";
 }
 
 void VPWidenMemoryInstructionRecipe::print(raw_ostream &O,
                                            const Twine &Indent) const {
   O << " +\n" << Indent << "\"WIDEN " << VPlanIngredient(&Instr);
-  if (User) {
+  VPValue *Mask = getMask();
+  if (Mask) {
     O << ", ";
-    User->getOperand(0)->printAsOperand(O);
+    Mask->printAsOperand(O);
   }
   O << "\\l\"";
 }
 
 template void DomTreeBuilder::Calculate<VPDominatorTree>(VPDominatorTree &DT);
 
 void VPValue::replaceAllUsesWith(VPValue *New) {
   for (VPUser *User : users())