[VPlan] Add VPValue::replaceUsesWithIf (NFCI).

Add replaceUsesWithIf helper and use it in a few places.

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -1120,6 +1120,26 @@ void VPValue::replaceAllUsesWith(VPValue *New) {
   }
 }
 
+void VPValue::replaceUsesWithIf(
+    VPValue *New,
+    llvm::function_ref<bool(VPUser &U, unsigned Idx)> ShouldReplace) {
+  for (unsigned J = 0; J < getNumUsers();) {
+    VPUser *User = Users[J];
+    unsigned NumUsers = getNumUsers();
+    for (unsigned I = 0, E = User->getNumOperands(); I < E; ++I) {
+      if (User->getOperand(I) != this || !ShouldReplace(*User, I))
+        continue;
+
+      User->setOperand(I, New);
+    }
+    // If a user got removed after updating the current user, the next user to
+    // update will be moved to the current position, so we only need to
+    // increment the index if the number of users did not change.
+    if (NumUsers == getNumUsers())
+      J++;
+  }
+}
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void VPValue::printAsOperand(raw_ostream &OS, VPSlotTracker &Tracker) const {
   if (const Value *UV = getUnderlyingValue()) {

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -162,17 +162,10 @@ static bool sinkScalarOperands(VPlan &Plan) {
       // TODO: add ".cloned" suffix to name of Clone's VPValue.
 
       Clone->insertBefore(SinkCandidate);
-      for (auto *U : to_vector(SinkCandidate->getVPSingleValue()->users())) {
-        auto *UI = cast<VPRecipeBase>(U);
-        if (UI->getParent() == SinkTo)
-          continue;
-
-        for (unsigned Idx = 0; Idx != UI->getNumOperands(); Idx++) {
-          if (UI->getOperand(Idx) != SinkCandidate->getVPSingleValue())
-            continue;
-          UI->setOperand(Idx, Clone);
-        }
-      }
+      SinkCandidate->getVPSingleValue()->replaceUsesWithIf(
+          Clone, [SinkTo](VPUser &U, unsigned) {
+            return cast<VPRecipeBase>(&U)->getParent() != SinkTo;
+          });
     }
     SinkCandidate->moveBefore(*SinkTo, SinkTo->getFirstNonPhi());
     for (VPValue *Op : SinkCandidate->operands())
@@ -277,16 +270,10 @@ static bool mergeReplicateRegionsIntoSuccessors(VPlan &Plan) {
       VPValue *PredInst1 =
           cast<VPPredInstPHIRecipe>(&Phi1ToMove)->getOperand(0);
       VPValue *Phi1ToMoveV = Phi1ToMove.getVPSingleValue();
-      for (VPUser *U : to_vector(Phi1ToMoveV->users())) {
-        auto *UI = dyn_cast<VPRecipeBase>(U);
-        if (!UI || UI->getParent() != Then2)
-          continue;
-        for (unsigned I = 0, E = U->getNumOperands(); I != E; ++I) {
-          if (Phi1ToMoveV != U->getOperand(I))
-            continue;
-          U->setOperand(I, PredInst1);
-        }
-      }
+      Phi1ToMoveV->replaceUsesWithIf(PredInst1, [Then2](VPUser &U, unsigned) {
+        auto *UI = dyn_cast<VPRecipeBase>(&U);
+        return UI && UI->getParent() == Then2;
+      });
 
       Phi1ToMove.moveBefore(*Merge2, Merge2->begin());
     }
@@ -542,16 +529,10 @@ void VPlanTransforms::optimizeInductions(VPlan &Plan, ScalarEvolution &SE) {
 
     // Update scalar users of IV to use Step instead. Use SetVector to ensure
     // the list of users doesn't contain duplicates.
-    SetVector<VPUser *> Users(WideIV->user_begin(), WideIV->user_end());
-    for (VPUser *U : Users) {
-      if (HasOnlyVectorVFs && !U->usesScalars(WideIV))
-        continue;
-      for (unsigned I = 0, E = U->getNumOperands(); I != E; I++) {
-        if (U->getOperand(I) != WideIV)
-          continue;
-        U->setOperand(I, Steps);
-      }
-    }
+    WideIV->replaceUsesWithIf(
+        Steps, [HasOnlyVectorVFs, WideIV](VPUser &U, unsigned) {
+          return !HasOnlyVectorVFs || U.usesScalars(WideIV);
+        });
   }
 }
 

llvm/lib/Transforms/Vectorize/VPlanValue.h

@@ -163,6 +163,13 @@ public:
 
   void replaceAllUsesWith(VPValue *New);
 
+  /// Go through the uses list for this VPValue and make each use point to \p
+  /// New if the callback ShouldReplace returns true for the given use specified
+  /// by a pair of (VPUser, the use index).
+  void replaceUsesWithIf(
+      VPValue *New,
+      llvm::function_ref<bool(VPUser &U, unsigned Idx)> ShouldReplace);
+
   /// Returns the recipe defining this VPValue or nullptr if it is not defined
   /// by a recipe, i.e. is a live-in.
   VPRecipeBase *getDefiningRecipe();