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
@@ -587,11 +587,11 @@
 
   /// \returns the cost incurred by unwanted spills and fills, caused by
   /// holding live values over call sites.
-  int getSpillCost() const;
+  InstructionCost getSpillCost() const;
 
   /// \returns the vectorization cost of the subtree that starts at \p VL.
   /// A negative number means that this is profitable.
-  int getTreeCost();
+  InstructionCost getTreeCost();
 
   /// Construct a vectorizable tree that starts at \p Roots, ignoring users for
   /// the purpose of scheduling and extraction in the \p UserIgnoreLst.
@@ -3949,13 +3949,13 @@
   return true;
 }
 
-int BoUpSLP::getSpillCost() const {
+InstructionCost BoUpSLP::getSpillCost() const {
   // Walk from the bottom of the tree to the top, tracking which values are
   // live. When we see a call instruction that is not part of our tree,
   // query TTI to see if there is a cost to keeping values live over it
   // (for example, if spills and fills are required).
   unsigned BundleWidth = VectorizableTree.front()->Scalars.size();
-  int Cost = 0;
+  InstructionCost Cost = 0;
 
   SmallPtrSet<Instruction*, 4> LiveValues;
   Instruction *PrevInst = nullptr;
@@ -4031,8 +4031,8 @@
   return Cost;
 }
 
-int BoUpSLP::getTreeCost() {
-  int Cost = 0;
+InstructionCost BoUpSLP::getTreeCost() {
+  InstructionCost Cost = 0;
   LLVM_DEBUG(dbgs() << "SLP: Calculating cost for tree of size "
                     << VectorizableTree.size() << ".\n");
 
@@ -4062,7 +4062,7 @@
                     }))
       continue;
 
-    int C = getEntryCost(&TE);
+    InstructionCost C = getEntryCost(&TE);
     Cost += C;
     LLVM_DEBUG(dbgs() << "SLP: Adding cost " << C
                       << " for bundle that starts with " << *TE.Scalars[0]
@@ -4071,7 +4071,7 @@
   }
 
   SmallPtrSet<Value *, 16> ExtractCostCalculated;
-  int ExtractCost = 0;
+  InstructionCost ExtractCost = 0;
   for (ExternalUser &EU : ExternalUses) {
     // We only add extract cost once for the same scalar.
     if (!ExtractCostCalculated.insert(EU.Scalar).second)
@@ -4101,7 +4101,7 @@
     }
   }
 
-  int SpillCost = getSpillCost();
+  InstructionCost SpillCost = getSpillCost();
   Cost += SpillCost + ExtractCost;
 
 #ifndef NDEBUG
@@ -6009,10 +6009,10 @@
 
   R.computeMinimumValueSizes();
 
-  int Cost = R.getTreeCost();
+  InstructionCost Cost = R.getTreeCost();
 
   LLVM_DEBUG(dbgs() << "SLP: Found cost = " << Cost << " for VF =" << VF << "\n");
-  if (Cost < -SLPCostThreshold) {
+  if (Cost.isValid() && Cost < -SLPCostThreshold) {
     LLVM_DEBUG(dbgs() << "SLP: Decided to vectorize cost = " << Cost << "\n");
 
     using namespace ore;
@@ -6213,7 +6213,7 @@
 
   bool Changed = false;
   bool CandidateFound = false;
-  int MinCost = SLPCostThreshold;
+  InstructionCost MinCost = SLPCostThreshold.getValue();
 
   bool CompensateUseCost =
       !InsertUses.empty() && llvm::all_of(InsertUses, [](const Value *V) {
@@ -6269,7 +6269,7 @@
         continue;
 
       R.computeMinimumValueSizes();
-      int Cost = R.getTreeCost();
+      InstructionCost Cost = R.getTreeCost();
       CandidateFound = true;
       if (CompensateUseCost) {
         // TODO: Use TTI's getScalarizationOverhead for sequence of inserts
@@ -6299,7 +6299,7 @@
         // Switching to the TTI interface might help a bit.
         // Alternative solution could be pattern-match to detect a no-op or
         // shuffle.
-        unsigned UserCost = 0;
+        InstructionCost UserCost = 0;
         for (unsigned Lane = 0; Lane < OpsWidth; Lane++) {
           auto *IE = cast<InsertElementInst>(InsertUses[I + Lane]);
           if (auto *CI = dyn_cast<ConstantInt>(IE->getOperand(2)))
@@ -6311,9 +6311,9 @@
         Cost -= UserCost;
       }
 
-      MinCost = std::min(MinCost, Cost);
+      MinCost = InstructionCost::min(MinCost, Cost);
 
-      if (Cost < -SLPCostThreshold) {
+      if (Cost.isValid() && Cost < -SLPCostThreshold) {
         LLVM_DEBUG(dbgs() << "SLP: Vectorizing list at cost:" << Cost << ".\n");
         R.getORE()->emit(OptimizationRemark(SV_NAME, "VectorizedList",
                                                     cast<Instruction>(Ops[0]))
@@ -7088,9 +7088,14 @@
       V.computeMinimumValueSizes();
 
       // Estimate cost.
-      int TreeCost = V.getTreeCost();
-      int ReductionCost = getReductionCost(TTI, ReducedVals[i], ReduxWidth);
-      int Cost = TreeCost + ReductionCost;
+      InstructionCost TreeCost = V.getTreeCost();
+      InstructionCost ReductionCost =
+          getReductionCost(TTI, ReducedVals[i], ReduxWidth);
+      InstructionCost Cost = TreeCost + ReductionCost;
+      if (!Cost.isValid()) {
+        LLVM_DEBUG(dbgs() << "Encountered invalid baseline cost.\n");
+        return false;
+      }
       if (Cost >= -SLPCostThreshold) {
         V.getORE()->emit([&]() {
           return OptimizationRemarkMissed(SV_NAME, "HorSLPNotBeneficial",