[X86] combineConcatVectorOps - use ConcatSubOperand helper to concat VPERMV3 subvector operands together.

Shouldn't affect existing test coverage, but aggressively peeking through bitcasts before concatenation will help in a future patch.

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -57974,18 +57974,16 @@ static SDValue combineConcatVectorOps(const SDLoc &DL, MVT VT,
               int Src = M < NumSrcElts ? 0 : 2;
               M += M < NumSrcElts ? 0 : NumSrcElts;
 
-              // Reference the lowest sub if they upper sub is the same.
+              // Reference the lowest sub if the upper sub is the same.
               if (Ops[0].getOperand(Src) != Ops[i].getOperand(Src))
                 M += i * NumSrcElts;
             }
             ConcatMask.push_back(M);
           }
         }
         if (ConcatMask.size() == (NumOps * NumSrcElts)) {
-          SDValue Src0 = concatSubVectors(Ops[0].getOperand(0),
-                                          Ops[1].getOperand(0), DAG, DL);
-          SDValue Src1 = concatSubVectors(Ops[0].getOperand(2),
-                                          Ops[1].getOperand(2), DAG, DL);
+          SDValue Src0 = ConcatSubOperand(VT, Ops, 0);
+          SDValue Src1 = ConcatSubOperand(VT, Ops, 2);
           MVT IntMaskSVT = MVT::getIntegerVT(EltSizeInBits);
           MVT IntMaskVT = MVT::getVectorVT(IntMaskSVT, NumOps * NumSrcElts);
           SDValue Mask = getConstVector(ConcatMask, IntMaskVT, DAG, DL, true);