[ARM] Refactor LowerDivRem before adding LowerREM (nfc)

lib/Target/ARM/ARMISelLowering.cpp

void ARMTargetLowering::LowerAsmOperandForConstraint(SDValue Op,
 
   if (Result.getNode()) {
     Ops.push_back(Result);
     return;
   }
   return TargetLowering::LowerAsmOperandForConstraint(Op, Constraint, Ops, DAG);
 }
 
-SDValue ARMTargetLowering::LowerDivRem(SDValue Op, SelectionDAG &DAG) const {
-  assert((Subtarget->isTargetAEABI() || Subtarget->isTargetAndroid()) &&
-         "Register-based DivRem lowering only");
-  unsigned Opcode = Op->getOpcode();
-  assert((Opcode == ISD::SDIVREM || Opcode == ISD::UDIVREM) &&
-         "Invalid opcode for Div/Rem lowering");
-  bool isSigned = (Opcode == ISD::SDIVREM);
-  EVT VT = Op->getValueType(0);
-  Type *Ty = VT.getTypeForEVT(*DAG.getContext());
-
+static RTLIB::Libcall getDivRemLibcall(
+    const SDNode *N, MVT::SimpleValueType SVT) {
+  assert((N->getOpcode() == ISD::SDIVREM || N->getOpcode() == ISD::UDIVREM) &&
+         "Unhandled Opcode in getDivRemLibcall");
+  bool isSigned = N->getOpcode() == ISD::SDIVREM;
   RTLIB::Libcall LC;
-  switch (VT.getSimpleVT().SimpleTy) {
+  switch (SVT) {
   default: llvm_unreachable("Unexpected request for libcall!");
   case MVT::i8:  LC = isSigned ? RTLIB::SDIVREM_I8  : RTLIB::UDIVREM_I8;  break;
   case MVT::i16: LC = isSigned ? RTLIB::SDIVREM_I16 : RTLIB::UDIVREM_I16; break;
   case MVT::i32: LC = isSigned ? RTLIB::SDIVREM_I32 : RTLIB::UDIVREM_I32; break;
   case MVT::i64: LC = isSigned ? RTLIB::SDIVREM_I64 : RTLIB::UDIVREM_I64; break;
   }
+  return LC;
+}
 
-  SDValue InChain = DAG.getEntryNode();
-
+static TargetLowering::ArgListTy getDivRemArgList(
+    const SDNode *N, LLVMContext *Context) {
+  assert((N->getOpcode() == ISD::SDIVREM || N->getOpcode() == ISD::UDIVREM) &&
+         "Unhandled Opcode in getDivRemArgList");
+  bool isSigned = N->getOpcode() == ISD::SDIVREM;
   TargetLowering::ArgListTy Args;
   TargetLowering::ArgListEntry Entry;
-  for (unsigned i = 0, e = Op->getNumOperands(); i != e; ++i) {
-    EVT ArgVT = Op->getOperand(i).getValueType();
-    Type *ArgTy = ArgVT.getTypeForEVT(*DAG.getContext());
-    Entry.Node = Op->getOperand(i);
+  for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
+    EVT ArgVT = N->getOperand(i).getValueType();
+    Type *ArgTy = ArgVT.getTypeForEVT(*Context);
+    Entry.Node = N->getOperand(i);
     Entry.Ty = ArgTy;
     Entry.isSExt = isSigned;
     Entry.isZExt = !isSigned;
     Args.push_back(Entry);
   }
+  return Args;
+}
+
+SDValue ARMTargetLowering::LowerDivRem(SDValue Op, SelectionDAG &DAG) const {
+  assert((Subtarget->isTargetAEABI() || Subtarget->isTargetAndroid()) &&
+         "Register-based DivRem lowering only");
+  unsigned Opcode = Op->getOpcode();
+  assert((Opcode == ISD::SDIVREM || Opcode == ISD::UDIVREM) &&
+         "Invalid opcode for Div/Rem lowering");
+  bool isSigned = (Opcode == ISD::SDIVREM);
+  EVT VT = Op->getValueType(0);
+  Type *Ty = VT.getTypeForEVT(*DAG.getContext());
+
+  RTLIB::Libcall LC = getDivRemLibcall(Op.getNode(),
+                                       VT.getSimpleVT().SimpleTy);
+  SDValue InChain = DAG.getEntryNode();
+
+  TargetLowering::ArgListTy Args = getDivRemArgList(Op.getNode(),
+                                                    DAG.getContext());
 
   SDValue Callee = DAG.getExternalSymbol(getLibcallName(LC),
                                          getPointerTy(DAG.getDataLayout()));
 
   Type *RetTy = (Type*)StructType::get(Ty, Ty, nullptr);
 
   SDLoc dl(Op);
   TargetLowering::CallLoweringInfo CLI(DAG);