diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -7113,7 +7113,6 @@
     // into a vector and can be represented as a permutation elements in a
     // single input vector or of 2 input vectors.
     Cost += computeExtractCost(VL, Mask, ShuffleKind);
-    InVectors.assign(1, E);
     return VecBase;
   }
   void add(const TreeEntry *E1, const TreeEntry *E2, ArrayRef<int> Mask) {
@@ -7124,18 +7123,57 @@
     CommonMask.assign(Mask.begin(), Mask.end());
     InVectors.assign(1, E1);
   }
-  void gather(ArrayRef<Value *> VL, Value *Root = nullptr) {
+  /// Adds another one input vector and the mask for the shuffling.
+  void add(Value *V1, ArrayRef<int> Mask) {
+    assert(CommonMask.empty() && InVectors.empty() &&
+           "Expected empty input mask/vectors.");
+    CommonMask.assign(Mask.begin(), Mask.end());
+    InVectors.assign(1, V1);
+  }
+  Value *gather(ArrayRef<Value *> VL, Value *Root = nullptr) {
     Cost += getBuildVectorCost(VL, Root);
     if (!Root) {
       assert(InVectors.empty() && "Unexpected input vectors for buildvector.");
       // FIXME: Need to find a way to avoid use of getNullValue here.
-      InVectors.assign(1, Constant::getNullValue(FixedVectorType::get(
-                              VL.front()->getType(), VL.size())));
+      SmallVector<Constant *> Vals;
+      for (Value *V : VL) {
+        if (isa<UndefValue>(V)) {
+          Vals.push_back(cast<Constant>(V));
+          continue;
+        }
+        Vals.push_back(Constant::getNullValue(V->getType()));
+      }
+      return ConstantVector::get(Vals);
     }
+    return ConstantVector::getSplat(
+        ElementCount::getFixed(VL.size()),
+        Constant::getNullValue(VL.front()->getType()));
   }
   /// Finalize emission of the shuffles.
-  InstructionCost finalize(ArrayRef<int> ExtMask) {
+  InstructionCost
+  finalize(ArrayRef<int> ExtMask, unsigned VF = 0,
+           function_ref<void(Value *&, SmallVectorImpl<int> &)> Action = {}) {
     IsFinalized = true;
+    if (Action) {
+      const PointerUnion<Value *, const TreeEntry *> &Vec = InVectors.front();
+      if (InVectors.size() == 2) {
+        Cost += createShuffle(Vec, InVectors.back(), CommonMask);
+        InVectors.pop_back();
+      } else {
+        Cost += createShuffle(Vec, nullptr, CommonMask);
+      }
+      for (unsigned Idx = 0, Sz = CommonMask.size(); Idx < Sz; ++Idx)
+        if (CommonMask[Idx] != PoisonMaskElem)
+          CommonMask[Idx] = Idx;
+      assert(VF > 0 &&
+             "Expected vector length for the final value before action.");
+      Value *V = Vec.dyn_cast<Value *>();
+      if (!Vec.isNull() && !V)
+        V = Constant::getNullValue(FixedVectorType::get(
+            Vec.get<const TreeEntry *>()->Scalars.front()->getType(),
+            CommonMask.size()));
+      Action(V, CommonMask);
+    }
     ::addMask(CommonMask, ExtMask, /*ExtendingManyInputs=*/true);
     if (CommonMask.empty())
       return Cost;
@@ -7259,18 +7297,31 @@
         Estimator.add(Entries.front(), Mask);
       else
         Estimator.add(Entries.front(), Entries.back(), Mask);
-      Estimator.gather(
-          GatheredScalars,
-          Constant::getNullValue(FixedVectorType::get(
-              GatheredScalars.front()->getType(), GatheredScalars.size())));
-      return Estimator.finalize(E->ReuseShuffleIndices);
-    }
-    Estimator.gather(
-        GatheredScalars,
-        VL.equals(GatheredScalars)
-            ? nullptr
-            : Constant::getNullValue(FixedVectorType::get(
-                  GatheredScalars.front()->getType(), GatheredScalars.size())));
+      if (all_of(GatheredScalars, PoisonValue ::classof))
+        return Estimator.finalize(E->ReuseShuffleIndices);
+      return Estimator.finalize(
+          E->ReuseShuffleIndices, E->Scalars.size(),
+          [&](Value *&Vec, SmallVectorImpl<int> &Mask) {
+            Vec = Estimator.gather(GatheredScalars,
+                                   Constant::getNullValue(FixedVectorType::get(
+                                       GatheredScalars.front()->getType(),
+                                       GatheredScalars.size())));
+          });
+    }
+    if (!all_of(GatheredScalars, PoisonValue::classof)) {
+      auto Gathers = ArrayRef(GatheredScalars).take_front(VL.size());
+      bool SameGathers = VL.equals(Gathers);
+      Value *BV = Estimator.gather(
+          Gathers, SameGathers ? nullptr
+                               : Constant::getNullValue(FixedVectorType::get(
+                                     GatheredScalars.front()->getType(),
+                                     GatheredScalars.size())));
+      SmallVector<int> ReuseMask(Gathers.size(), PoisonMaskElem);
+      std::iota(ReuseMask.begin(), ReuseMask.end(), 0);
+      Estimator.add(BV, ReuseMask);
+    }
+    if (ExtractShuffle)
+      Estimator.add(E, std::nullopt);
     return Estimator.finalize(E->ReuseShuffleIndices);
   }
   InstructionCost CommonCost = 0;