[LV][NFC] Rename getNumUsers to getNumUses

The Users list in VPValue is really just a Use list because the
same User can appear several times in the list, reflecting the fact
the VPValue can be used for more than one operand of a recipe. In
such a scenario there is really just one *user* with multiple
*uses* of a given Value. See the documentation for the IR routine
Value::hasOneUser():

---
  /// Return true if there is exactly one user of this value.
  ///
  /// Note that this is not the same as "has one use". If a value has one use,
  /// then there certainly is a single user. But if value has several uses,
  /// it is possible that all uses are in a single user, or not.
  ///
  /// This check is potentially costly, since it requires traversing,
  /// in the worst case, the whole use list of a value.
  LLVM_ABI bool hasOneUser() const;
---

I've renamed this function, along with removeUser to more accurately
reflect what the code is doing.

Author: david-arm

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -4207,7 +4207,7 @@ VectorizationFactor LoopVectorizationPlanner::selectVectorizationFactor() {
           // divisors.
           case Instruction::Select: {
             VPValue *VPV = VPI->getVPSingleValue();
-            if (VPV->getNumUsers() == 1) {
+            if (VPV->getNumUses() == 1) {
               if (auto *WR = dyn_cast<VPWidenRecipe>(*VPV->user_begin())) {
                 switch (WR->getOpcode()) {
                 case Instruction::UDiv:

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -1056,25 +1056,25 @@ const VPRegionBlock *VPlan::getVectorLoopRegion() const {
 void VPlan::printLiveIns(raw_ostream &O) const {
   VPSlotTracker SlotTracker(this);
 
-  if (VF.getNumUsers() > 0) {
+  if (VF.getNumUses() > 0) {
     O << "\nLive-in ";
     VF.printAsOperand(O, SlotTracker);
     O << " = VF";
   }
 
-  if (VFxUF.getNumUsers() > 0) {
+  if (VFxUF.getNumUses() > 0) {
     O << "\nLive-in ";
     VFxUF.printAsOperand(O, SlotTracker);
     O << " = VF * UF";
   }
 
-  if (VectorTripCount.getNumUsers() > 0) {
+  if (VectorTripCount.getNumUses() > 0) {
     O << "\nLive-in ";
     VectorTripCount.printAsOperand(O, SlotTracker);
     O << " = vector-trip-count";
   }
 
-  if (BackedgeTakenCount && BackedgeTakenCount->getNumUsers()) {
+  if (BackedgeTakenCount && BackedgeTakenCount->getNumUses()) {
     O << "\nLive-in ";
     BackedgeTakenCount->printAsOperand(O, SlotTracker);
     O << " = backedge-taken count";
@@ -1416,7 +1416,7 @@ void VPValue::replaceUsesWithIf(
   if (this == New)
     return;
 
-  for (unsigned J = 0; J < getNumUsers();) {
+  for (unsigned J = 0; J < getNumUses();) {
     VPUser *User = Users[J];
     bool RemovedUser = false;
     for (unsigned I = 0, E = User->getNumOperands(); I < E; ++I) {
@@ -1492,9 +1492,9 @@ void VPSlotTracker::assignName(const VPValue *V) {
 }
 
 void VPSlotTracker::assignNames(const VPlan &Plan) {
-  if (Plan.VF.getNumUsers() > 0)
+  if (Plan.VF.getNumUses() > 0)
     assignName(&Plan.VF);
-  if (Plan.VFxUF.getNumUsers() > 0)
+  if (Plan.VFxUF.getNumUses() > 0)
     assignName(&Plan.VFxUF);
   assignName(&Plan.VectorTripCount);
   if (Plan.BackedgeTakenCount)

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -4204,7 +4204,7 @@ class VPlan {
   /// Resets the trip count for the VPlan. The caller must make sure all uses of
   /// the original trip count have been replaced.
   void resetTripCount(VPValue *NewTripCount) {
-    assert(TripCount && NewTripCount && TripCount->getNumUsers() == 0 &&
+    assert(TripCount && NewTripCount && TripCount->getNumUses() == 0 &&
            "TripCount must be set when resetting");
     TripCount = NewTripCount;
   }

llvm/lib/Transforms/Vectorize/VPlanConstruction.cpp

@@ -885,7 +885,7 @@ bool VPlanTransforms::handleMaxMinNumReductions(VPlan &Plan) {
     if (VecV == RdxResult)
       continue;
     if (auto *DerivedIV = dyn_cast<VPDerivedIVRecipe>(VecV)) {
-      if (DerivedIV->getNumUsers() == 1 &&
+      if (DerivedIV->getNumUses() == 1 &&
           DerivedIV->getOperand(1) == &Plan.getVectorTripCount()) {
         auto *NewSel = Builder.createSelect(AnyNaN, Plan.getCanonicalIV(),
                                             &Plan.getVectorTripCount());

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -2249,7 +2249,7 @@ InstructionCost VPWidenCastRecipe::computeCost(ElementCount VF,
   TTI::CastContextHint CCH = TTI::CastContextHint::None;
   // For Trunc/FPTrunc, get the context from the only user.
   if ((Opcode == Instruction::Trunc || Opcode == Instruction::FPTrunc) &&
-      !hasMoreThanOneUniqueUser() && getNumUsers() > 0) {
+      !hasMoreThanOneUniqueUser() && getNumUses() > 0) {
     if (auto *StoreRecipe = dyn_cast<VPRecipeBase>(*user_begin()))
       CCH = ComputeCCH(StoreRecipe);
   }

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -316,7 +316,7 @@ static bool mergeReplicateRegionsIntoSuccessors(VPlan &Plan) {
       });
 
       // Remove phi recipes that are unused after merging the regions.
-      if (Phi1ToMove.getVPSingleValue()->getNumUsers() == 0) {
+      if (Phi1ToMove.getVPSingleValue()->getNumUses() == 0) {
         Phi1ToMove.eraseFromParent();
         continue;
       }
@@ -363,7 +363,7 @@ static VPRegionBlock *createReplicateRegion(VPReplicateRecipe *PredRecipe,
       Plan.createVPBasicBlock(Twine(RegionName) + ".if", RecipeWithoutMask);
 
   VPPredInstPHIRecipe *PHIRecipe = nullptr;
-  if (PredRecipe->getNumUsers() != 0) {
+  if (PredRecipe->getNumUses() != 0) {
     PHIRecipe = new VPPredInstPHIRecipe(RecipeWithoutMask,
                                         RecipeWithoutMask->getDebugLoc());
     PredRecipe->replaceAllUsesWith(PHIRecipe);
@@ -547,7 +547,7 @@ static bool isDeadRecipe(VPRecipeBase &R) {
 
   // Recipe is dead if no user keeps the recipe alive.
   return all_of(R.definedValues(),
-                [](VPValue *V) { return V->getNumUsers() == 0; });
+                [](VPValue *V) { return V->getNumUses() == 0; });
 }
 
 void VPlanTransforms::removeDeadRecipes(VPlan &Plan) {
@@ -563,11 +563,11 @@ void VPlanTransforms::removeDeadRecipes(VPlan &Plan) {
 
       // Check if R is a dead VPPhi <-> update cycle and remove it.
       auto *PhiR = dyn_cast<VPPhi>(&R);
-      if (!PhiR || PhiR->getNumOperands() != 2 || PhiR->getNumUsers() != 1)
+      if (!PhiR || PhiR->getNumOperands() != 2 || PhiR->getNumUses() != 1)
         continue;
       VPValue *Incoming = PhiR->getOperand(1);
       if (*PhiR->user_begin() != Incoming->getDefiningRecipe() ||
-          Incoming->getNumUsers() != 1)
+          Incoming->getNumUses() != 1)
         continue;
       PhiR->replaceAllUsesWith(PhiR->getOperand(0));
       PhiR->eraseFromParent();
@@ -658,7 +658,7 @@ static void legalizeAndOptimizeInductions(VPlan &Plan) {
       auto *RepR = dyn_cast<VPReplicateRecipe>(U);
       // Skip recipes that shouldn't be narrowed.
       if (!Def || !isa<VPReplicateRecipe, VPWidenRecipe>(Def) ||
-          Def->getNumUsers() == 0 || !Def->getUnderlyingValue() ||
+          Def->getNumUses() == 0 || !Def->getUnderlyingValue() ||
           (RepR && (RepR->isSingleScalar() || RepR->isPredicated())))
         continue;
 
@@ -1344,7 +1344,7 @@ static void simplifyBlends(VPlan &Plan) {
         // TODO: Find the most expensive mask that can be deadcoded, or a mask
         // that's used by multiple blends where it can be removed from them all.
         VPValue *Mask = Blend->getMask(I);
-        if (Mask->getNumUsers() == 1 && !match(Mask, m_False())) {
+        if (Mask->getNumUses() == 1 && !match(Mask, m_False())) {
           StartIndex = I;
           break;
         }
@@ -1380,7 +1380,7 @@ static void simplifyBlends(VPlan &Plan) {
         NewBlend->setOperand(0, Inc1);
         NewBlend->setOperand(1, Inc0);
         NewBlend->setOperand(2, NewMask);
-        if (OldMask->getNumUsers() == 0)
+        if (OldMask->getNumUses() == 0)
           cast<VPInstruction>(OldMask)->eraseFromParent();
       }
     }
@@ -2467,7 +2467,7 @@ static void transformRecipestoEVLRecipes(VPlan &Plan, VPValue &EVL) {
     ToErase.push_back(CurRecipe);
   }
   // Remove dead EVL mask.
-  if (EVLMask->getNumUsers() == 0)
+  if (EVLMask->getNumUses() == 0)
     ToErase.push_back(EVLMask->getDefiningRecipe());
 
   for (VPRecipeBase *R : reverse(ToErase)) {
@@ -3445,7 +3445,7 @@ void VPlanTransforms::materializeBroadcasts(VPlan &Plan) {
 #endif
 
   SmallVector<VPValue *> VPValues;
-  if (Plan.getOrCreateBackedgeTakenCount()->getNumUsers() > 0)
+  if (Plan.getOrCreateBackedgeTakenCount()->getNumUses() > 0)
     VPValues.push_back(Plan.getOrCreateBackedgeTakenCount());
   append_range(VPValues, Plan.getLiveIns());
   for (VPRecipeBase &R : *Plan.getEntry())
@@ -3514,7 +3514,7 @@ void VPlanTransforms::materializeConstantVectorTripCount(
 void VPlanTransforms::materializeBackedgeTakenCount(VPlan &Plan,
                                                     VPBasicBlock *VectorPH) {
   VPValue *BTC = Plan.getOrCreateBackedgeTakenCount();
-  if (BTC->getNumUsers() == 0)
+  if (BTC->getNumUses() == 0)
     return;
 
   VPBuilder Builder(VectorPH, VectorPH->begin());
@@ -3580,7 +3580,7 @@ void VPlanTransforms::materializeVectorTripCount(VPlan &Plan,
   assert(VectorTC.isLiveIn() && "vector-trip-count must be a live-in");
   // There's nothing to do if there are no users of the vector trip count or its
   // IR value has already been set.
-  if (VectorTC.getNumUsers() == 0 || VectorTC.getLiveInIRValue())
+  if (VectorTC.getNumUses() == 0 || VectorTC.getLiveInIRValue())
     return;
 
   VPValue *TC = Plan.getTripCount();
@@ -3645,7 +3645,7 @@ void VPlanTransforms::materializeVFAndVFxUF(VPlan &Plan, VPBasicBlock *VectorPH,
 
   // If there are no users of the runtime VF, compute VFxUF by constant folding
   // the multiplication of VF and UF.
-  if (VF.getNumUsers() == 0) {
+  if (VF.getNumUses() == 0) {
     VPValue *RuntimeVFxUF =
         Builder.createElementCount(TCTy, VFEC * Plan.getUF());
     VFxUF.replaceAllUsesWith(RuntimeVFxUF);

llvm/lib/Transforms/Vectorize/VPlanUnroll.cpp

@@ -535,7 +535,7 @@ void VPlanTransforms::replicateByVF(VPlan &Plan, ElementCount VF) {
         continue;
 
       VPBuilder Builder(RepR);
-      if (RepR->getNumUsers() == 0) {
+      if (RepR->getNumUses() == 0) {
         if (isa<StoreInst>(RepR->getUnderlyingInstr()) &&
             vputils::isSingleScalar(RepR->getOperand(1))) {
           // Stores to invariant addresses need to store the last lane only.

llvm/lib/Transforms/Vectorize/VPlanValue.h

@@ -110,13 +110,18 @@ class LLVM_ABI_FOR_TEST VPValue {
   void dump() const;
 #endif
 
-  unsigned getNumUsers() const { return Users.size(); }
+  /// Returns the number of uses of this VPValue. The same user could appear
+  /// more than once in the list due to this value being used for multiple
+  /// operands in a recipe.
+  unsigned getNumUses() const { return Users.size(); }
+
+  /// Adds a user of this value to the list.
   void addUser(VPUser &User) { Users.push_back(&User); }
 
-  /// Remove a single \p User from the list of users.
-  void removeUser(VPUser &User) {
+  /// Remove the first instance of \p User from the list of uses.
+  void removeFirstUse(VPUser &User) {
     // The same user can be added multiple times, e.g. because the same VPValue
-    // is used twice by the same VPUser. Remove a single one.
+    // is used twice by the same VPUser. Remove the first one.
     auto *I = find(Users, &User);
     if (I != Users.end())
       Users.erase(I);
@@ -138,7 +143,7 @@ class LLVM_ABI_FOR_TEST VPValue {
 
   /// Returns true if the value has more than one unique user.
   bool hasMoreThanOneUniqueUser() const {
-    if (getNumUsers() == 0)
+    if (getNumUses() == 0)
       return false;
 
     // Check if all users match the first user.
@@ -203,7 +208,7 @@ class VPUser {
   /// Removes the operand at index \p Idx. This also removes the VPUser from the
   /// use-list of the operand.
   void removeOperand(unsigned Idx) {
-    getOperand(Idx)->removeUser(*this);
+    getOperand(Idx)->removeFirstUse(*this);
     Operands.erase(Operands.begin() + Idx);
   }
 
@@ -224,7 +229,7 @@ class VPUser {
   VPUser &operator=(const VPUser &) = delete;
   virtual ~VPUser() {
     for (VPValue *Op : operands())
-      Op->removeUser(*this);
+      Op->removeFirstUse(*this);
   }
 
   void addOperand(VPValue *Operand) {
@@ -239,7 +244,7 @@ class VPUser {
   }
 
   void setOperand(unsigned I, VPValue *New) {
-    Operands[I]->removeUser(*this);
+    Operands[I]->removeFirstUse(*this);
     Operands[I] = New;
     New->addUser(*this);
   }
@@ -383,7 +388,7 @@ class VPDef {
     for (VPValue *D : make_early_inc_range(DefinedValues)) {
       assert(D->Def == this &&
              "all defined VPValues should point to the containing VPDef");
-      assert(D->getNumUsers() == 0 &&
+      assert(D->getNumUses() == 0 &&
              "all defined VPValues should have no more users");
       D->Def = nullptr;
       delete D;

llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp

@@ -198,8 +198,8 @@ bool VPlanVerifier::verifyEVLRecipe(const VPInstruction &EVL) const {
           }
           // EVLIVIncrement is only used by EVLIV & BranchOnCount.
           // Having more than two users is unexpected.
-          if ((I->getNumUsers() != 1) &&
-              (I->getNumUsers() != 2 || none_of(I->users(), [&I](VPUser *U) {
+          if ((I->getNumUses() != 1) &&
+              (I->getNumUses() != 2 || none_of(I->users(), [&I](VPUser *U) {
                  using namespace llvm::VPlanPatternMatch;
                  return match(U, m_BranchOnCount(m_Specific(I), m_VPValue()));
                }))) {