+/// \brief Detect bitcasts between i32 to x86mmx low word. Since MMX types are
+/// special and don't usually play with other vector types, it's better to
+/// handle them early to be sure we emit efficient code by avoiding
+/// store-load conversions.
+static SDValue PerformBITCASTCombine(SDNode *N, SelectionDAG &DAG) {
+ if (N->getValueType(0) != MVT::x86mmx ||
+ N->getOperand(0)->getOpcode() != ISD::BUILD_VECTOR ||
+ N->getOperand(0)->getValueType(0) != MVT::v2i32)
+ return SDValue();
+
+ SDValue V = N->getOperand(0);
+ ConstantSDNode *C = dyn_cast<ConstantSDNode>(V.getOperand(1));
+ if (C && C->getZExtValue() == 0 && V.getOperand(0).getValueType() == MVT::i32)
+ return DAG.getNode(X86ISD::MMX_MOVW2D, SDLoc(V.getOperand(0)),
+ N->getValueType(0), V.getOperand(0));
+
+ return SDValue();
+}
+