diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4315,8 +4315,8 @@
                         return Ops[0].getValueType() == Op.getValueType();
                       }) &&
          "Concatenation of vectors with inconsistent value types!");
-  assert((Ops.size() * Ops[0].getValueType().getVectorNumElements()) ==
-             VT.getVectorNumElements() &&
+  assert((Ops[0].getValueType().getVectorElementCount() * Ops.size()) ==
+             VT.getVectorElementCount() &&
          "Incorrect element count in vector concatenation!");
 
   if (Ops.size() == 1)
@@ -4333,7 +4333,7 @@
   bool IsIdentity = true;
   for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
     SDValue Op = Ops[i];
-    unsigned IdentityIndex = i * Op.getValueType().getVectorNumElements();
+    unsigned IdentityIndex = i * Op.getValueType().getVectorMinNumElements();
     if (Op.getOpcode() != ISD::EXTRACT_SUBVECTOR ||
         Op.getOperand(0).getValueType() != VT ||
         (IdentitySrc && Op.getOperand(0) != IdentitySrc) ||
@@ -4350,6 +4350,11 @@
     return IdentitySrc;
   }
 
+  // The code below this point is only designed to work for fixed width
+  // vectors, so we bail out for now.
+  if (VT.isScalableVector())
+    return SDValue();
+
   // A CONCAT_VECTOR with all UNDEF/BUILD_VECTOR operands can be
   // simplified to one big BUILD_VECTOR.
   // FIXME: Add support for SCALAR_TO_VECTOR as well.