Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -5020,6 +5020,12 @@
   if (!VT.isVector())
     return SDValue();
 
+  // TODO: All the folds below are performed lane-by-lane and assume a fixed
+  // vector width, however we should be able to do constant folds involving
+  // splat vector nodes too.
+  if (VT.isScalableVector())
+    return SDValue();
+
   unsigned NumElts = VT.getVectorNumElements();
 
   auto IsScalarOrSameVectorSize = [&](const SDValue &Op) {