+/// \brief Handle lowering 2-lane 128-bit shuffles.
+static SDValue lowerV2X128VectorShuffle(SDLoc DL, MVT VT, SDValue V1,
+ SDValue V2, ArrayRef<int> Mask,
+ const X86Subtarget *Subtarget,
+ SelectionDAG &DAG) {
+ // Blends are faster and handle all the non-lane-crossing cases.
+ if (SDValue Blend = lowerVectorShuffleAsBlend(DL, VT, V1, V2, Mask,
+ Subtarget, DAG))
+ return Blend;
+
+ MVT SubVT = MVT::getVectorVT(VT.getVectorElementType(),
+ VT.getVectorNumElements() / 2);
+ // Check for patterns which can be matched with a single insert of a 128-bit
+ // subvector.
+ if (isShuffleEquivalent(Mask, 0, 1, 0, 1) ||
+ isShuffleEquivalent(Mask, 0, 1, 4, 5)) {
+ SDValue LoV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT, V1,
+ DAG.getIntPtrConstant(0));
+ SDValue HiV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT,
+ Mask[2] < 4 ? V1 : V2, DAG.getIntPtrConstant(0));
+ return DAG.getNode(ISD::CONCAT_VECTORS, DL, VT, LoV, HiV);
+ }
+ if (isShuffleEquivalent(Mask, 0, 1, 6, 7)) {
+ SDValue LoV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT, V1,
+ DAG.getIntPtrConstant(0));
+ SDValue HiV = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, SubVT, V2,
+ DAG.getIntPtrConstant(2));
+ return DAG.getNode(ISD::CONCAT_VECTORS, DL, VT, LoV, HiV);
+ }
+
+ // Otherwise form a 128-bit permutation.
+ // FIXME: Detect zero-vector inputs and use the VPERM2X128 to zero that half.
+ unsigned PermMask = Mask[0] / 2 | (Mask[2] / 2) << 4;
+ return DAG.getNode(X86ISD::VPERM2X128, DL, VT, V1, V2,
+ DAG.getConstant(PermMask, MVT::i8));
+}
+