Index: llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -2179,13 +2179,18 @@
   SDValue Idx = N->getOperand(1);
   SDLoc dl(N);
   SDValue Lo, Hi;
+
+  assert(SubVT.isScalableVector() ==
+             N->getOperand(0).getValueType().isScalableVector() &&
+         "We only support extracting fixed length vectors from legal scalable "
+         "vector types");
   GetSplitVector(N->getOperand(0), Lo, Hi);
 
-  uint64_t LoElts = Lo.getValueType().getVectorNumElements();
+  uint64_t LoElts = Lo.getValueType().getVectorMinNumElements();
   uint64_t IdxVal = cast<ConstantSDNode>(Idx)->getZExtValue();
 
   if (IdxVal < LoElts) {
-    assert(IdxVal + SubVT.getVectorNumElements() <= LoElts &&
+    assert(IdxVal + SubVT.getVectorMinNumElements() <= LoElts &&
            "Extracted subvector crosses vector split!");
     return DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, SubVT, Lo, Idx);
   } else {