Addressed Most Code Review Comments

Author: GrumpyPigSkin

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

@@ -2175,9 +2175,8 @@ SDValue DAGTypeLegalizer::PromoteIntOp_ATOMIC_STORE(AtomicSDNode *N) {
 
 SDValue DAGTypeLegalizer::PromoteIntOp_BITCAST(SDNode *N) {
   // Use the custom lowering.
-  if (const auto Res = LowerBitcast(N)) {
+  if (SDValue Res = LowerBitcast(N))
     return Res;
-  }
 
   // If it fails fall back to the default method
   return CreateStackStoreLoad(N->getOperand(0), N->getValueType(0));

llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.cpp

@@ -910,36 +910,32 @@ SDValue DAGTypeLegalizer::CreateStackStoreLoad(SDValue Op,
   return DAG.getLoad(DestVT, dl, Store, StackPtr, MachinePointerInfo(), Align);
 }
 
-static SDValue MaybeBitcast(SelectionDAG &DAG, SDLoc DL, EVT VT,
-                            SDValue Value) {
-  if (Value->getValueType(0) == VT)
-    return Value;
-  return DAG.getNode(ISD::BITCAST, DL, VT, Value);
-}
-
 SDValue DAGTypeLegalizer::LowerBitcast(SDNode *Node) const {
   assert(Node->getOpcode() == ISD::BITCAST && "Unexpected opcode!");
   // Handle bitcasting from v2i8 without hitting the default promotion
   // strategy which goes through stack memory.
   EVT FromVT = Node->getOperand(0)->getValueType(0);
-  if (FromVT != MVT::v2i8) {
+  if (FromVT != MVT::v2i8)
     return SDValue();
-  }
 
   // Pack vector elements into i16 and bitcast to final type
   SDLoc DL(Node);
   SDValue Vec0 = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, MVT::i8,
                              Node->getOperand(0), DAG.getIntPtrConstant(0, DL));
   SDValue Vec1 = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, MVT::i8,
                              Node->getOperand(0), DAG.getIntPtrConstant(1, DL));
+  
   SDValue Extend0 = DAG.getNode(ISD::ZERO_EXTEND, DL, MVT::i16, Vec0);
   SDValue Extend1 = DAG.getNode(ISD::ZERO_EXTEND, DL, MVT::i16, Vec1);
-  SDValue Const8 = DAG.getConstant(8, DL, MVT::i16);
+  
+  EVT ShiftAmtTy = TLI.getShiftAmountTy(Extend1.getValueType(), DAG.getDataLayout());
+  SDValue ShiftConst = DAG.getShiftAmountConstant(8, ShiftAmtTy, DL);
   SDValue AsInt = DAG.getNode(
-      ISD::OR, DL, MVT::i16,
-      {Extend0, DAG.getNode(ISD::SHL, DL, MVT::i16, {Extend1, Const8})});
+      ISD::OR, DL, MVT::i16, Extend0,
+      DAG.getNode(ISD::SHL, DL, Extend1.getValueType(), Extend1, ShiftConst));
   EVT ToVT = Node->getValueType(0);
-  return MaybeBitcast(DAG, DL, ToVT, AsInt);
+  
+  return DAG.getBitcast( ToVT, AsInt);
 }
 
 /// Replace the node's results with custom code provided by the target and