diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index f0fd6ce7ae50..30866518a48a 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -5721,11 +5721,16 @@ static SDValue insert1BitVector(SDValue Op, SelectionDAG &DAG,
   return DAG.getNode(ISD::EXTRACT_SUBVECTOR, dl, OpVT, Op, ZeroIdx);
 }
 
-static SDValue concatSubVectors(SDValue V1, SDValue V2, EVT VT,
-                                unsigned NumElems, SelectionDAG &DAG,
-                                const SDLoc &dl, unsigned VectorWidth) {
-  SDValue V = insertSubVector(DAG.getUNDEF(VT), V1, 0, DAG, dl, VectorWidth);
-  return insertSubVector(V, V2, NumElems / 2, DAG, dl, VectorWidth);
+static SDValue concatSubVectors(SDValue V1, SDValue V2, SelectionDAG &DAG,
+                                const SDLoc &dl) {
+  assert(V1.getValueType() == V2.getValueType() && "subvector type mismatch");
+  EVT SubVT = V1.getValueType();
+  EVT SubSVT = SubVT.getScalarType();
+  unsigned SubNumElts = SubVT.getVectorNumElements();
+  unsigned SubVectorWidth = SubVT.getSizeInBits();
+  EVT VT = EVT::getVectorVT(*DAG.getContext(), SubSVT, 2 * SubNumElts);
+  SDValue V = insertSubVector(DAG.getUNDEF(VT), V1, 0, DAG, dl, SubVectorWidth);
+  return insertSubVector(V, V2, SubNumElts, DAG, dl, SubVectorWidth);
 }
 
 /// Returns a vector of specified type with all bits set.
@@ -9633,8 +9638,7 @@ X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
         HVT, dl, Op->ops().slice(NumElems / 2, NumElems /2));
 
     // Recreate the wider vector with the lower and upper part.
-    return concatSubVectors(Lower, Upper, VT, NumElems, DAG, dl,
-                            VT.getSizeInBits() / 2);
+    return concatSubVectors(Lower, Upper, DAG, dl);
   }
 
   // Let legalizer expand 2-wide build_vectors.
@@ -42222,12 +42226,11 @@ static SDValue combineZext(SDNode *N, SelectionDAG &DAG,
       VT.getScalarSizeInBits() == N0.getOperand(0).getScalarValueSizeInBits()) {
     SDValue N00 = N0.getOperand(0);
     SDValue N01 = N0.getOperand(1);
-    unsigned NumSrcElts = N00.getValueType().getVectorNumElements();
     unsigned NumSrcEltBits = N00.getScalarValueSizeInBits();
     APInt ZeroMask = APInt::getHighBitsSet(NumSrcEltBits, NumSrcEltBits / 2);
     if ((N00.isUndef() || DAG.MaskedValueIsZero(N00, ZeroMask)) &&
         (N01.isUndef() || DAG.MaskedValueIsZero(N01, ZeroMask))) {
-      return concatSubVectors(N00, N01, VT, NumSrcElts * 2, DAG, dl, 128);
+      return concatSubVectors(N00, N01, DAG, dl);
     }
   }