diff --git a/llvm/include/llvm/CodeGen/BasicTTIImpl.h b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
--- a/llvm/include/llvm/CodeGen/BasicTTIImpl.h
+++ b/llvm/include/llvm/CodeGen/BasicTTIImpl.h
@@ -195,6 +195,10 @@
                                               bool VariableMask,
                                               bool IsGatherScatter,
                                               TTI::TargetCostKind CostKind) {
+    // Cost for scalable type is Invalid, can't assume any num elements.
+    if (isa<ScalableVectorType>(DataTy))
+      return InstructionCost::getInvalid();
+
     auto *VT = cast<FixedVectorType>(DataTy);
     // Assume the target does not have support for gather/scatter operations
     // and provide a rough estimate.