[AVR] Add instruction selection lowering code

[dylanmckay]

Summary

This adds AVRISelLowering.cpp

[dylanmckay]

I accidentally committed this and immediately reverted.

[arsenm]

llvm/trunk/lib/Target/AVR/AVRISelLowering.cpp

97–98 ↗

(On Diff #72968)

Setting these to Expand should be unnecessary since you don't add i32/i64 as legal types (same for all of the other operations)

100 ↗

(On Diff #72968)

Capitalize

844–846 ↗

(On Diff #72968)

Don't repeat the documentation

849 ↗

(On Diff #72968)

Comment doesn't make sense to me here

1134 ↗

(On Diff #72968)

nullptr

1136–1140 ↗

(On Diff #72968)

Why not just immediately cast to Function and then remove GV variable

1321–1326 ↗

(On Diff #72968)

Formatting

1509 ↗

(On Diff #72968)

static, no inline

1674 ↗

(On Diff #72968)

!CallOperandVal

1782–1783 ↗

(On Diff #72968)

You should be able to avoid a cast with getSubtarget<AVRSubtarget>

[dylanmckay]

Code review from Matt

• Don't both setting operations to expand on already illegal types
• Clean up some comments
• Use nullptr rather than 0

[dylanmckay]

llvm/trunk/lib/Target/AVR/AVRISelLowering.cpp

1136–1140 ↗

(On Diff #72968)

We need the GV variable in the call to getTargetGlobalAddress

1782–1783 ↗

(On Diff #72968)

We don't have access to a Function object needed to call that functions.

[dylanmckay]

Ping

[kparzysz]

LGTM with a few comments.

lib/Target/AVR/AVRISelLowering.cpp

885

Else after return, same below.

1803

Same here.

lib/Target/AVR/AVRISelLowering.h

 // This file defines the interfaces that AVR uses to lower LLVM code into a
 // selection DAG.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_AVR_ISEL_LOWERING_H
 #define LLVM_AVR_ISEL_LOWERING_H
 
+#include "llvm/CodeGen/CallingConvLower.h"
 #include "llvm/Target/TargetLowering.h"
 
 namespace llvm {
 
 namespace AVRISD {
 
 /// AVR Specific DAG Nodes
 enum NodeType {
bool getPreIndexedAddressParts(SDNode *N, SDValue &Base, SDValue &Offset,
                                  SelectionDAG &DAG) const override;
 
   bool getPostIndexedAddressParts(SDNode *N, SDNode *Op, SDValue &Base,
                                   SDValue &Offset, ISD::MemIndexedMode &AM,
                                   SelectionDAG &DAG) const override;
 
   bool isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const override;
 
+  EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Context,
+                         EVT VT) const override;
+
   MachineBasicBlock *
   EmitInstrWithCustomInserter(MachineInstr &MI,
                               MachineBasicBlock *MBB) const override;
 
   ConstraintType getConstraintType(StringRef Constraint) const override;
 
   ConstraintWeight
   getSingleConstraintMatchWeight(AsmOperandInfo &info,
private:
   SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerBlockAddress(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerBR_CC(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerINLINEASM(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerSETCC(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerVASTART(SDValue Op, SelectionDAG &DAG) const;
 
+  CCAssignFn *CCAssignFnForReturn(CallingConv::ID CC) const;
+
+  bool CanLowerReturn(CallingConv::ID CallConv,
+                      MachineFunction &MF, bool isVarArg,
+                      const SmallVectorImpl<ISD::OutputArg> &Outs,
+                      LLVMContext &Context) const override;
+
   SDValue LowerReturn(SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
                       const SmallVectorImpl<ISD::OutputArg> &Outs,
                       const SmallVectorImpl<SDValue> &OutVals, const SDLoc &dl,
                       SelectionDAG &DAG) const override;
   SDValue LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv,
                                bool isVarArg,
                                const SmallVectorImpl<ISD::InputArg> &Ins,
                                const SDLoc &dl, SelectionDAG &DAG,
                                SmallVectorImpl<SDValue> &InVals) const override;
   SDValue LowerCall(TargetLowering::CallLoweringInfo &CLI,
                     SmallVectorImpl<SDValue> &InVals) const override;
   SDValue LowerCallResult(SDValue Chain, SDValue InFlag,
                           CallingConv::ID CallConv, bool isVarArg,
                           const SmallVectorImpl<ISD::InputArg> &Ins,
                           const SDLoc &dl, SelectionDAG &DAG,
                           SmallVectorImpl<SDValue> &InVals) const;
 
 private:
-  MachineBasicBlock *insertShift(MachineInstr *MI, MachineBasicBlock *BB) const;
-  MachineBasicBlock *insertMul(MachineInstr *MI, MachineBasicBlock *BB) const;
+  MachineBasicBlock *insertShift(MachineInstr &MI, MachineBasicBlock *BB) const;
+  MachineBasicBlock *insertMul(MachineInstr &MI, MachineBasicBlock *BB) const;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_AVR_ISEL_LOWERING_H

lib/Target/AVR/AVRISelLowering.cpp

+//===-- AVRISelLowering.cpp - AVR DAG Lowering Implementation -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the interfaces that AVR uses to lower LLVM code into a
+// selection DAG.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AVRISelLowering.h"
+
+#include "llvm/CodeGen/CallingConvLower.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/SelectionDAG.h"
+#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
+#include "llvm/IR/Function.h"
+#include "llvm/Support/ErrorHandling.h"
+
+#include "AVR.h"
+#include "AVRMachineFunctionInfo.h"
+#include "AVRTargetMachine.h"
+#include "MCTargetDesc/AVRMCTargetDesc.h"
+
+namespace llvm {
+
+AVRTargetLowering::AVRTargetLowering(AVRTargetMachine &tm)
+    : TargetLowering(tm) {
+  // Set up the register classes.
+  addRegisterClass(MVT::i8, &AVR::GPR8RegClass);
+  addRegisterClass(MVT::i16, &AVR::DREGSRegClass);
+
+  // Compute derived properties from the register classes.
+  computeRegisterProperties(tm.getSubtargetImpl()->getRegisterInfo());
+
+  setBooleanContents(ZeroOrOneBooleanContent);
+  setBooleanVectorContents(ZeroOrOneBooleanContent);
+  setSchedulingPreference(Sched::RegPressure);
+  setStackPointerRegisterToSaveRestore(AVR::SP);
+
+  setOperationAction(ISD::GlobalAddress, MVT::i16, Custom);
+  setOperationAction(ISD::BlockAddress, MVT::i16, Custom);
+
+  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i8, Expand);
+  setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i16, Expand);
+
+  for (MVT VT : MVT::integer_valuetypes()) {
+    for (auto N : {ISD::EXTLOAD, ISD::SEXTLOAD, ISD::ZEXTLOAD}) {
+      setLoadExtAction(N, VT, MVT::i1, Promote);
+      setLoadExtAction(N, VT, MVT::i8, Expand);
+    }
+  }
+
+  setTruncStoreAction(MVT::i16, MVT::i8, Expand);
+
+  // sub (x, imm) gets canonicalized to add (x, -imm), so for illegal types
+  // revert into a sub since we don't have an add with immediate instruction.
+  setOperationAction(ISD::ADD, MVT::i32, Custom);
+  setOperationAction(ISD::ADD, MVT::i64, Custom);
+
+  // our shift instructions are only able to shift 1 bit at a time, so handle
+  // this in a custom way.
+  setOperationAction(ISD::SRA, MVT::i8, Custom);
+  setOperationAction(ISD::SHL, MVT::i8, Custom);
+  setOperationAction(ISD::SRL, MVT::i8, Custom);
+  setOperationAction(ISD::SRA, MVT::i16, Custom);
+  setOperationAction(ISD::SHL, MVT::i16, Custom);
+  setOperationAction(ISD::SRL, MVT::i16, Custom);
+  setOperationAction(ISD::SHL_PARTS, MVT::i16, Expand);
+  setOperationAction(ISD::SRA_PARTS, MVT::i16, Expand);
+  setOperationAction(ISD::SRL_PARTS, MVT::i16, Expand);
+
+  setOperationAction(ISD::BR_CC, MVT::i8, Custom);
+  setOperationAction(ISD::BR_CC, MVT::i16, Custom);
+  setOperationAction(ISD::BR_CC, MVT::i32, Custom);
+  setOperationAction(ISD::BR_CC, MVT::i64, Custom);
+  setOperationAction(ISD::BRCOND, MVT::Other, Expand);
+
+  setOperationAction(ISD::SELECT_CC, MVT::i8, Custom);
+  setOperationAction(ISD::SELECT_CC, MVT::i16, Custom);
+  setOperationAction(ISD::SELECT_CC, MVT::i32, Custom);
+  setOperationAction(ISD::SELECT_CC, MVT::i64, Custom);
+  setOperationAction(ISD::SETCC, MVT::i8, Custom);
+  setOperationAction(ISD::SETCC, MVT::i16, Custom);
+  setOperationAction(ISD::SETCC, MVT::i32, Custom);
+  setOperationAction(ISD::SETCC, MVT::i64, Custom);
+  setOperationAction(ISD::SELECT, MVT::i8, Expand);
+  setOperationAction(ISD::SELECT, MVT::i16, Expand);
+
+  setOperationAction(ISD::BSWAP, MVT::i16, Expand);
+  setOperationAction(ISD::BSWAP, MVT::i32, Expand);
+  setOperationAction(ISD::BSWAP, MVT::i64, Expand);
+
+  // add support for postincrement and predecrement load/stores.
+  setIndexedLoadAction(ISD::POST_INC, MVT::i8, Legal);
+  setIndexedLoadAction(ISD::POST_INC, MVT::i16, Legal);
+  setIndexedLoadAction(ISD::PRE_DEC, MVT::i8, Legal);
+  setIndexedLoadAction(ISD::PRE_DEC, MVT::i16, Legal);
+  setIndexedStoreAction(ISD::POST_INC, MVT::i8, Legal);
+  setIndexedStoreAction(ISD::POST_INC, MVT::i16, Legal);
+  setIndexedStoreAction(ISD::PRE_DEC, MVT::i8, Legal);
+  setIndexedStoreAction(ISD::PRE_DEC, MVT::i16, Legal);
+
+  setOperationAction(ISD::BR_JT, MVT::Other, Expand);
+
+  setOperationAction(ISD::VASTART, MVT::Other, Custom);
+  setOperationAction(ISD::VAEND, MVT::Other, Expand);
+  setOperationAction(ISD::VAARG, MVT::Other, Expand);
+  setOperationAction(ISD::VACOPY, MVT::Other, Expand);
+
+  // Atomic operations which must be lowered to rtlib calls
+  for (MVT VT : MVT::integer_valuetypes()) {
+    setOperationAction(ISD::ATOMIC_SWAP, VT, Expand);
+    setOperationAction(ISD::ATOMIC_CMP_SWAP, VT, Expand);
+    setOperationAction(ISD::ATOMIC_LOAD_NAND, VT, Expand);
+    setOperationAction(ISD::ATOMIC_LOAD_MAX, VT, Expand);
+    setOperationAction(ISD::ATOMIC_LOAD_MIN, VT, Expand);
+    setOperationAction(ISD::ATOMIC_LOAD_UMAX, VT, Expand);
+    setOperationAction(ISD::ATOMIC_LOAD_UMIN, VT, Expand);
+  }
+
+  // Division/remainder
+  setOperationAction(ISD::UDIV, MVT::i8, Expand);
+  setOperationAction(ISD::UDIV, MVT::i16, Expand);
+  setOperationAction(ISD::UREM, MVT::i8, Expand);
+  setOperationAction(ISD::UREM, MVT::i16, Expand);
+  setOperationAction(ISD::SDIV, MVT::i8, Expand);
+  setOperationAction(ISD::SDIV, MVT::i16, Expand);
+  setOperationAction(ISD::SREM, MVT::i8, Expand);
+  setOperationAction(ISD::SREM, MVT::i16, Expand);
+
+  // Make division and modulus custom
+  for (MVT VT : MVT::integer_valuetypes()) {
+    setOperationAction(ISD::UDIVREM, VT, Custom);
+    setOperationAction(ISD::SDIVREM, VT, Custom);
+  }
+
+  // Do not use MUL. The AVR instructions are closer to SMUL_LOHI &co.
+  setOperationAction(ISD::MUL, MVT::i8, Expand);
+  setOperationAction(ISD::MUL, MVT::i16, Expand);
+
+  // Expand 16 bit multiplications.
+  setOperationAction(ISD::SMUL_LOHI, MVT::i16, Expand);
+  setOperationAction(ISD::UMUL_LOHI, MVT::i16, Expand);
+
+  for (MVT VT : MVT::integer_valuetypes()) {
+    setOperationAction(ISD::MULHS, VT, Expand);
+    setOperationAction(ISD::MULHU, VT, Expand);
+  }
+
+  for (MVT VT : MVT::integer_valuetypes()) {
+    setOperationAction(ISD::CTPOP, VT, Expand);
+    setOperationAction(ISD::CTLZ, VT, Expand);
+    setOperationAction(ISD::CTTZ, VT, Expand);
+  }
+
+  for (MVT VT : MVT::integer_valuetypes()) {
+    setOperationAction(ISD::SIGN_EXTEND_INREG, VT, Expand);
+    // TODO: The generated code is pretty poor. Investigate using the
+    // same "shift and subtract with carry" trick that we do for
+    // extending 8-bit to 16-bit. This may require infrastructure
+    // improvements in how we treat 16-bit "registers" to be feasible.
+  }
+
+  // Division rtlib functions (not supported)
+  setLibcallName(RTLIB::SDIV_I8, nullptr);
+  setLibcallName(RTLIB::SDIV_I16, nullptr);
+  setLibcallName(RTLIB::SDIV_I32, nullptr);
+  setLibcallName(RTLIB::SDIV_I64, nullptr);
+  setLibcallName(RTLIB::SDIV_I128, nullptr);
+  setLibcallName(RTLIB::UDIV_I8, nullptr);
+  setLibcallName(RTLIB::UDIV_I16, nullptr);
+  setLibcallName(RTLIB::UDIV_I32, nullptr);
+  setLibcallName(RTLIB::UDIV_I64, nullptr);
+  setLibcallName(RTLIB::UDIV_I128, nullptr);
+
+  // Modulus rtlib functions (not supported)
+  setLibcallName(RTLIB::SREM_I8, nullptr);
+  setLibcallName(RTLIB::SREM_I16, nullptr);
+  setLibcallName(RTLIB::SREM_I32, nullptr);
+  setLibcallName(RTLIB::SREM_I64, nullptr);
+  setLibcallName(RTLIB::SREM_I128, nullptr);
+  setLibcallName(RTLIB::UREM_I8, nullptr);
+  setLibcallName(RTLIB::UREM_I16, nullptr);
+  setLibcallName(RTLIB::UREM_I32, nullptr);
+  setLibcallName(RTLIB::UREM_I64, nullptr);
+  setLibcallName(RTLIB::UREM_I128, nullptr);
+
+  // Division and modulus rtlib functions
+  setLibcallName(RTLIB::SDIVREM_I8, "__divmodqi4");
+  setLibcallName(RTLIB::SDIVREM_I16, "__divmodhi4");
+  setLibcallName(RTLIB::SDIVREM_I32, "__divmodsi4");
+  setLibcallName(RTLIB::SDIVREM_I64, "__divmoddi4");
+  setLibcallName(RTLIB::SDIVREM_I128, "__divmodti4");
+  setLibcallName(RTLIB::UDIVREM_I8, "__udivmodqi4");
+  setLibcallName(RTLIB::UDIVREM_I16, "__udivmodhi4");
+  setLibcallName(RTLIB::UDIVREM_I32, "__udivmodsi4");
+  setLibcallName(RTLIB::UDIVREM_I64, "__udivmoddi4");
+  setLibcallName(RTLIB::UDIVREM_I128, "__udivmodti4");
+
+  // Several of the runtime library functions use a special calling conv
+  setLibcallCallingConv(RTLIB::SDIVREM_I8, CallingConv::AVR_BUILTIN);
+  setLibcallCallingConv(RTLIB::SDIVREM_I16, CallingConv::AVR_BUILTIN);
+  setLibcallCallingConv(RTLIB::UDIVREM_I8, CallingConv::AVR_BUILTIN);
+  setLibcallCallingConv(RTLIB::UDIVREM_I16, CallingConv::AVR_BUILTIN);
+
+  // Trigonometric rtlib functions
+  setLibcallName(RTLIB::SIN_F32, "sin");
+  setLibcallName(RTLIB::COS_F32, "cos");
+
+  setMinFunctionAlignment(1);
+  setMinimumJumpTableEntries(INT_MAX);
+}
+
+const char *AVRTargetLowering::getTargetNodeName(unsigned Opcode) const {
+#define NODE(name)       \
+  case AVRISD::name:     \
+    return #name
+
+  switch (Opcode) {
+  default:
+    return nullptr;
+    NODE(RET_FLAG);
+    NODE(RETI_FLAG);
+    NODE(CALL);
+    NODE(WRAPPER);
+    NODE(LSL);
+    NODE(LSR);
+    NODE(ROL);
+    NODE(ROR);
+    NODE(ASR);
+    NODE(LSLLOOP);
+    NODE(LSRLOOP);
+    NODE(ASRLOOP);
+    NODE(BRCOND);
+    NODE(CMP);
+    NODE(CMPC);
+    NODE(TST);
+    NODE(SELECT_CC);
+#undef NODE
+  }
+}
+
+EVT AVRTargetLowering::getSetCCResultType(const DataLayout &DL, LLVMContext &,
+                                          EVT VT) const {
+  assert(!VT.isVector() && "No AVR SetCC type for vectors!");
+  return MVT::i8;
+}
+
+SDValue AVRTargetLowering::LowerShifts(SDValue Op, SelectionDAG &DAG) const {
+  //:TODO: this function has to be completely rewritten to produce optimal
+  // code, for now it's producing very long but correct code.
+  unsigned Opc8;
+  const SDNode *N = Op.getNode();
+  EVT VT = Op.getValueType();
+  SDLoc dl(N);
+
+  // Expand non-constant shifts to loops.
+  if (!isa<ConstantSDNode>(N->getOperand(1))) {
+    switch (Op.getOpcode()) {
+    default:
+      llvm_unreachable("Invalid shift opcode!");
+    case ISD::SHL:
+      return DAG.getNode(AVRISD::LSLLOOP, dl, VT, N->getOperand(0),
+                         N->getOperand(1));
+    case ISD::SRL:
+      return DAG.getNode(AVRISD::LSRLOOP, dl, VT, N->getOperand(0),
+                         N->getOperand(1));
+    case ISD::SRA:
+      return DAG.getNode(AVRISD::ASRLOOP, dl, VT, N->getOperand(0),
+                         N->getOperand(1));
+    }
+  }
+
+  uint64_t ShiftAmount = cast<ConstantSDNode>(N->getOperand(1))->getZExtValue();
+  SDValue Victim = N->getOperand(0);
+
+  switch (Op.getOpcode()) {
+  case ISD::SRA:
+    Opc8 = AVRISD::ASR;
+    break;
+  case ISD::ROTL:
+    Opc8 = AVRISD::ROL;
+    break;
+  case ISD::ROTR:
+    Opc8 = AVRISD::ROR;
+    break;
+  case ISD::SRL:
+    Opc8 = AVRISD::LSR;
+    break;
+  case ISD::SHL:
+    Opc8 = AVRISD::LSL;
+    break;
+  default:
+    llvm_unreachable("Invalid shift opcode");
+  }
+
+  while (ShiftAmount--) {
+    Victim = DAG.getNode(Opc8, dl, VT, Victim);
+  }
+
+  return Victim;
+}
+
+SDValue AVRTargetLowering::LowerDivRem(SDValue Op, SelectionDAG &DAG) const {
+  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;
+  switch (VT.getSimpleVT().SimpleTy) {
+  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;
+  }
+
+  SDValue InChain = DAG.getEntryNode();
+
+  TargetLowering::ArgListTy Args;
+  TargetLowering::ArgListEntry Entry;
+  for (SDValue const &Value : Op->op_values()) {
+    Entry.Node = Value;
+    Entry.Ty = Value.getValueType().getTypeForEVT(*DAG.getContext());
+    Entry.isSExt = isSigned;
+    Entry.isZExt = !isSigned;
+    Args.push_back(Entry);
+  }
+
+  SDValue Callee = DAG.getExternalSymbol(getLibcallName(LC),
+                                         getPointerTy(DAG.getDataLayout()));
+
+  Type *RetTy = (Type *)StructType::get(Ty, Ty, nullptr);
+
+  SDLoc dl(Op);
+  TargetLowering::CallLoweringInfo CLI(DAG);
+  CLI.setDebugLoc(dl)
+      .setChain(InChain)
+      .setCallee(getLibcallCallingConv(LC), RetTy, Callee, std::move(Args))
+      .setInRegister()
+      .setSExtResult(isSigned)
+      .setZExtResult(!isSigned);
+
+  std::pair<SDValue, SDValue> CallInfo = LowerCallTo(CLI);
+  return CallInfo.first;
+}
+
+SDValue AVRTargetLowering::LowerGlobalAddress(SDValue Op,
+                                              SelectionDAG &DAG) const {
+  auto DL = DAG.getDataLayout();
+
+  const GlobalValue *GV = cast<GlobalAddressSDNode>(Op)->getGlobal();
+  int64_t Offset = cast<GlobalAddressSDNode>(Op)->getOffset();
+
+  // Create the TargetGlobalAddress node, folding in the constant offset.
+  SDValue Result =
+      DAG.getTargetGlobalAddress(GV, SDLoc(Op), getPointerTy(DL), Offset);
+  return DAG.getNode(AVRISD::WRAPPER, SDLoc(Op), getPointerTy(DL), Result);
+}
+
+SDValue AVRTargetLowering::LowerBlockAddress(SDValue Op,
+                                             SelectionDAG &DAG) const {
+  auto DL = DAG.getDataLayout();
+  const BlockAddress *BA = cast<BlockAddressSDNode>(Op)->getBlockAddress();
+
+  SDValue Result = DAG.getTargetBlockAddress(BA, getPointerTy(DL));
+
+  return DAG.getNode(AVRISD::WRAPPER, SDLoc(Op), getPointerTy(DL), Result);
+}
+
+/// IntCCToAVRCC - Convert a DAG integer condition code to an AVR CC.
+static AVRCC::CondCodes intCCToAVRCC(ISD::CondCode CC) {
+  switch (CC) {
+  default:
+    llvm_unreachable("Unknown condition code!");
+  case ISD::SETEQ:
+    return AVRCC::COND_EQ;
+  case ISD::SETNE:
+    return AVRCC::COND_NE;
+  case ISD::SETGE:
+    return AVRCC::COND_GE;
+  case ISD::SETLT:
+    return AVRCC::COND_LT;
+  case ISD::SETUGE:
+    return AVRCC::COND_SH;
+  case ISD::SETULT:
+    return AVRCC::COND_LO;
+  }
+}
+
+/// Returns appropriate AVR CMP/CMPC nodes and corresponding condition code for
+/// the given operands.
+SDValue AVRTargetLowering::getAVRCmp(SDValue LHS, SDValue RHS, ISD::CondCode CC,
+                                     SDValue &AVRcc, SelectionDAG &DAG,
+                                     SDLoc DL) const {
+  SDValue Cmp;
+  EVT VT = LHS.getValueType();
+  bool UseTest = false;
+
+  switch (CC) {
+  default:
+    break;
+  case ISD::SETLE: {
+    // Swap operands and reverse the branching condition.
+    std::swap(LHS, RHS);
+    CC = ISD::SETGE;
+    break;
+  }
+  case ISD::SETGT: {
+    if (const ConstantSDNode *C = dyn_cast<ConstantSDNode>(RHS)) {
+      switch (C->getSExtValue()) {
+      case -1: {
+        // When doing lhs > -1 use a tst instruction on the top part of lhs
+        // and use brpl instead of using a chain of cp/cpc.
+        UseTest = true;
+        AVRcc = DAG.getConstant(AVRCC::COND_PL, DL, MVT::i8);
+        break;
+      }
+      case 0: {
+        // Turn lhs > 0 into 0 < lhs since 0 can be materialized with
+        // __zero_reg__ in lhs.
+        RHS = LHS;
+        LHS = DAG.getConstant(0, DL, VT);
+        CC = ISD::SETLT;
+        break;
+      }
+      default: {
+        // Turn lhs < rhs with lhs constant into rhs >= lhs+1, this allows
+        // us to  fold the constant into the cmp instruction.
+        RHS = DAG.getConstant(C->getSExtValue() + 1, DL, VT);
+        CC = ISD::SETGE;
+        break;
+      }
+      }
+      break;
+    }
+    // Swap operands and reverse the branching condition.
+    std::swap(LHS, RHS);
+    CC = ISD::SETLT;
+    break;
+  }
+  case ISD::SETLT: {
+    if (const ConstantSDNode *C = dyn_cast<ConstantSDNode>(RHS)) {
+      switch (C->getSExtValue()) {
+      case 1: {
+        // Turn lhs < 1 into 0 >= lhs since 0 can be materialized with
+        // __zero_reg__ in lhs.
+        RHS = LHS;
+        LHS = DAG.getConstant(0, DL, VT);
+        CC = ISD::SETGE;
+        break;
+      }
+      case 0: {
+        // When doing lhs < 0 use a tst instruction on the top part of lhs
+        // and use brmi instead of using a chain of cp/cpc.
+        UseTest = true;
+        AVRcc = DAG.getConstant(AVRCC::COND_MI, DL, MVT::i8);
+        break;
+      }
+      }
+    }
+    break;
+  }
+  case ISD::SETULE: {
+    // Swap operands and reverse the branching condition.
+    std::swap(LHS, RHS);
+    CC = ISD::SETUGE;
+    break;
+  }
+  case ISD::SETUGT: {
+    // Turn lhs < rhs with lhs constant into rhs >= lhs+1, this allows us to
+    // fold the constant into the cmp instruction.
+    if (const ConstantSDNode *C = dyn_cast<ConstantSDNode>(RHS)) {
+      RHS = DAG.getConstant(C->getSExtValue() + 1, DL, VT);
+      CC = ISD::SETUGE;
+      break;
+    }
+    // Swap operands and reverse the branching condition.
+    std::swap(LHS, RHS);
+    CC = ISD::SETULT;
+    break;
+  }
+  }
+
+  // Expand 32 and 64 bit comparisons with custom CMP and CMPC nodes instead of
+  // using the default and/or/xor expansion code which is much longer.
+  if (VT == MVT::i32) {
+    SDValue LHSlo = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, LHS,
+                                DAG.getIntPtrConstant(0, DL));
+    SDValue LHShi = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, LHS,
+                                DAG.getIntPtrConstant(1, DL));
+    SDValue RHSlo = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, RHS,
+                                DAG.getIntPtrConstant(0, DL));
+    SDValue RHShi = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, RHS,
+                                DAG.getIntPtrConstant(1, DL));
+
+    if (UseTest) {
+      // When using tst we only care about the highest part.
+      SDValue Top = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i8, LHShi,
+                                DAG.getIntPtrConstant(1, DL));
+      Cmp = DAG.getNode(AVRISD::TST, DL, MVT::Glue, Top);
+    } else {
+      Cmp = DAG.getNode(AVRISD::CMP, DL, MVT::Glue, LHSlo, RHSlo);
+      Cmp = DAG.getNode(AVRISD::CMPC, DL, MVT::Glue, LHShi, RHShi, Cmp);
+    }
+  } else if (VT == MVT::i64) {
+    SDValue LHS_0 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i32, LHS,
+                                DAG.getIntPtrConstant(0, DL));
+    SDValue LHS_1 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i32, LHS,
+                                DAG.getIntPtrConstant(1, DL));
+
+    SDValue LHS0 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, LHS_0,
+                               DAG.getIntPtrConstant(0, DL));
+    SDValue LHS1 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, LHS_0,
+                               DAG.getIntPtrConstant(1, DL));
+    SDValue LHS2 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, LHS_1,
+                               DAG.getIntPtrConstant(0, DL));
+    SDValue LHS3 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, LHS_1,
+                               DAG.getIntPtrConstant(1, DL));
+
+    SDValue RHS_0 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i32, RHS,
+                                DAG.getIntPtrConstant(0, DL));
+    SDValue RHS_1 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i32, RHS,
+                                DAG.getIntPtrConstant(1, DL));
+
+    SDValue RHS0 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, RHS_0,
+                               DAG.getIntPtrConstant(0, DL));
+    SDValue RHS1 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, RHS_0,
+                               DAG.getIntPtrConstant(1, DL));
+    SDValue RHS2 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, RHS_1,
+                               DAG.getIntPtrConstant(0, DL));
+    SDValue RHS3 = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i16, RHS_1,
+                               DAG.getIntPtrConstant(1, DL));
+
+    if (UseTest) {
+      // When using tst we only care about the highest part.
+      SDValue Top = DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i8, LHS3,
+                                DAG.getIntPtrConstant(1, DL));
+      Cmp = DAG.getNode(AVRISD::TST, DL, MVT::Glue, Top);
+    } else {
+      Cmp = DAG.getNode(AVRISD::CMP, DL, MVT::Glue, LHS0, RHS0);
+      Cmp = DAG.getNode(AVRISD::CMPC, DL, MVT::Glue, LHS1, RHS1, Cmp);
+      Cmp = DAG.getNode(AVRISD::CMPC, DL, MVT::Glue, LHS2, RHS2, Cmp);
+      Cmp = DAG.getNode(AVRISD::CMPC, DL, MVT::Glue, LHS3, RHS3, Cmp);
+    }
+  } else if (VT == MVT::i8 || VT == MVT::i16) {
+    if (UseTest) {
+      // When using tst we only care about the highest part.
+      Cmp = DAG.getNode(AVRISD::TST, DL, MVT::Glue,
+                        (VT == MVT::i8)
+                            ? LHS
+                            : DAG.getNode(ISD::EXTRACT_ELEMENT, DL, MVT::i8,
+                                          LHS, DAG.getIntPtrConstant(1, DL)));
+    } else {
+      Cmp = DAG.getNode(AVRISD::CMP, DL, MVT::Glue, LHS, RHS);
+    }
+  } else {
+    llvm_unreachable("Invalid comparison size");
+  }
+
+  // When using a test instruction AVRcc is already set.
+  if (!UseTest) {
+    AVRcc = DAG.getConstant(intCCToAVRCC(CC), DL, MVT::i8);
+  }
+
+  return Cmp;
+}
+
+SDValue AVRTargetLowering::LowerBR_CC(SDValue Op, SelectionDAG &DAG) const {
+  SDValue Chain = Op.getOperand(0);
+  ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(1))->get();
+  SDValue LHS = Op.getOperand(2);
+  SDValue RHS = Op.getOperand(3);
+  SDValue Dest = Op.getOperand(4);
+  SDLoc dl(Op);
+
+  SDValue TargetCC;
+  SDValue Cmp = getAVRCmp(LHS, RHS, CC, TargetCC, DAG, dl);
+
+  return DAG.getNode(AVRISD::BRCOND, dl, MVT::Other, Chain, Dest, TargetCC,
+                     Cmp);
+}
+
+SDValue AVRTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
+  SDValue LHS = Op.getOperand(0);
+  SDValue RHS = Op.getOperand(1);
+  SDValue TrueV = Op.getOperand(2);
+  SDValue FalseV = Op.getOperand(3);
+  ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(4))->get();
+  SDLoc dl(Op);
+
+  SDValue TargetCC;
+  SDValue Cmp = getAVRCmp(LHS, RHS, CC, TargetCC, DAG, dl);
+
+  SDVTList VTs = DAG.getVTList(Op.getValueType(), MVT::Glue);
+  SDValue Ops[] = {TrueV, FalseV, TargetCC, Cmp};
+
+  return DAG.getNode(AVRISD::SELECT_CC, dl, VTs, Ops);
+}
+
+SDValue AVRTargetLowering::LowerSETCC(SDValue Op, SelectionDAG &DAG) const {
+  SDValue LHS = Op.getOperand(0);
+  SDValue RHS = Op.getOperand(1);
+  ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(2))->get();
+  SDLoc DL(Op);
+
+  SDValue TargetCC;
+  SDValue Cmp = getAVRCmp(LHS, RHS, CC, TargetCC, DAG, DL);
+
+  SDValue TrueV = DAG.getConstant(1, DL, Op.getValueType());
+  SDValue FalseV = DAG.getConstant(0, DL, Op.getValueType());
+  SDVTList VTs = DAG.getVTList(Op.getValueType(), MVT::Glue);
+  SDValue Ops[] = {TrueV, FalseV, TargetCC, Cmp};
+
+  return DAG.getNode(AVRISD::SELECT_CC, DL, VTs, Ops);
+}
+
+SDValue AVRTargetLowering::LowerVASTART(SDValue Op, SelectionDAG &DAG) const {
+  const MachineFunction &MF = DAG.getMachineFunction();
+  const AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();
+  const Value *SV = cast<SrcValueSDNode>(Op.getOperand(2))->getValue();
+  auto DL = DAG.getDataLayout();
+  SDLoc dl(Op);
+
+  // Vastart just stores the address of the VarArgsFrameIndex slot into the
+  // memory location argument.
+  SDValue FI = DAG.getFrameIndex(AFI->getVarArgsFrameIndex(), getPointerTy(DL));
+
+  return DAG.getStore(Op.getOperand(0), dl, FI, Op.getOperand(1),
+                      MachinePointerInfo(SV), 0);
+}
+
+SDValue AVRTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
+  switch (Op.getOpcode()) {
+  default:
+    llvm_unreachable("Don't know how to custom lower this!");
+  case ISD::SHL:
+  case ISD::SRA:
+  case ISD::SRL:
+  case ISD::ROTL:
+  case ISD::ROTR:
+    return LowerShifts(Op, DAG);
+  case ISD::GlobalAddress:
+    return LowerGlobalAddress(Op, DAG);
+  case ISD::BlockAddress:
+    return LowerBlockAddress(Op, DAG);
+  case ISD::BR_CC:
+    return LowerBR_CC(Op, DAG);
+  case ISD::SELECT_CC:
+    return LowerSELECT_CC(Op, DAG);
+  case ISD::SETCC:
+    return LowerSETCC(Op, DAG);
+  case ISD::VASTART:
+    return LowerVASTART(Op, DAG);
+  case ISD::SDIVREM:
+  case ISD::UDIVREM:
+    return LowerDivRem(Op, DAG);
+  }
+
+  return SDValue();
+}
+
+/// Replace a node with an illegal result type
+/// with a new node built out of custom code.
+void AVRTargetLowering::ReplaceNodeResults(SDNode *N,
+                                           SmallVectorImpl<SDValue> &Results,
+                                           SelectionDAG &DAG) const {
+  SDLoc DL(N);
+
+  switch (N->getOpcode()) {
+  case ISD::ADD: {
+    // Convert add (x, imm) into sub (x, -imm).
+    if (const ConstantSDNode *C = dyn_cast<ConstantSDNode>(N->getOperand(1))) {
+      SDValue Sub = DAG.getNode(
+          ISD::SUB, DL, N->getValueType(0), N->getOperand(0),
+          DAG.getConstant(-C->getAPIntValue(), DL, C->getValueType(0)));
+      Results.push_back(Sub);
+    }
+    break;
+  }
+  default: {
+    SDValue Res = LowerOperation(SDValue(N, 0), DAG);
+
+    for (unsigned I = 0, E = Res->getNumValues(); I != E; ++I)
+      Results.push_back(Res.getValue(I));
+
+    break;
+  }
+  }
+}
+
+/// Return true if the addressing mode represented
+/// by AM is legal for this target, for a load/store of the specified type.
+bool AVRTargetLowering::isLegalAddressingMode(const DataLayout &DL,
+                                              const AddrMode &AM, Type *Ty,
+                                              unsigned AS) const {
+  int64_t Offs = AM.BaseOffs;
+
+  // Allow absolute addresses.
+  if (AM.BaseGV && !AM.HasBaseReg && AM.Scale == 0 && Offs == 0) {
+    return true;
+  }
+
+  // Flash memory instructions only allow zero offsets.
+  if (isa<PointerType>(Ty) && AS == AVR::ProgramMemory) {
+    return false;
+  }
+
+  // Allow reg+<6bit> offset.
+  if (Offs < 0)
+    Offs = -Offs;
+  if (AM.BaseGV == 0 && AM.HasBaseReg && AM.Scale == 0 && isUInt<6>(Offs)) {
+    return true;
+  }
+
+  return false;
+}
+
+/// Returns true by value, base pointer and
+/// offset pointer and addressing mode by reference if the node's address
+/// can be legally represented as pre-indexed load / store address.
+bool AVRTargetLowering::getPreIndexedAddressParts(SDNode *N, SDValue &Base,
+                                                  SDValue &Offset,
+                                                  ISD::MemIndexedMode &AM,
+                                                  SelectionDAG &DAG) const {
+  EVT VT;
+  const SDNode *Op;
+  SDLoc DL(N);
+
+  if (const LoadSDNode *LD = dyn_cast<LoadSDNode>(N)) {
+    VT = LD->getMemoryVT();
+    Op = LD->getBasePtr().getNode();
+    if (LD->getExtensionType() != ISD::NON_EXTLOAD)
+      return false;
+    if (AVR::isProgramMemoryAccess(LD)) {
+      return false;
+    }
+  } else if (const StoreSDNode *ST = dyn_cast<StoreSDNode>(N)) {
+    VT = ST->getMemoryVT();
+    Op = ST->getBasePtr().getNode();
+    if (AVR::isProgramMemoryAccess(ST)) {
+      return false;
+    }
+  } else {
+    return false;
+  }
+
+  if (VT != MVT::i8 && VT != MVT::i16) {
+    return false;
+  }
+
+  if (Op->getOpcode() != ISD::ADD && Op->getOpcode() != ISD::SUB) {
+    return false;
+  }
+
+  if (const ConstantSDNode *RHS = dyn_cast<ConstantSDNode>(Op->getOperand(1))) {
+    int RHSC = RHS->getSExtValue();
+    if (Op->getOpcode() == ISD::SUB)
+      RHSC = -RHSC;
+
+    if ((VT == MVT::i16 && RHSC != -2) || (VT == MVT::i8 && RHSC != -1)) {
+      return false;
+    }
+
+    Base = Op->getOperand(0);
+    Offset = DAG.getConstant(RHSC, DL, MVT::i8);
+    AM = ISD::PRE_DEC;
+
+    return true;
+  }
+
+  return false;
+}
+
+/// Returns true by value, base pointer and
+/// offset pointer and addressing mode by reference if this node can be
+/// combined with a load / store to form a post-indexed load / store.
+bool AVRTargetLowering::getPostIndexedAddressParts(SDNode *N, SDNode *Op,
+                                                   SDValue &Base,
+                                                   SDValue &Offset,
+                                                   ISD::MemIndexedMode &AM,
+                                                   SelectionDAG &DAG) const {
+  EVT VT;
+  SDLoc DL(N);
+
+  if (const LoadSDNode *LD = dyn_cast<LoadSDNode>(N)) {
+    VT = LD->getMemoryVT();
+    if (LD->getExtensionType() != ISD::NON_EXTLOAD)
+      return false;
+  } else if (const StoreSDNode *ST = dyn_cast<StoreSDNode>(N)) {
+    VT = ST->getMemoryVT();
+    if (AVR::isProgramMemoryAccess(ST)) {
+      return false;
+    }
+  } else {
+    return false;
+  }
+
+  if (VT != MVT::i8 && VT != MVT::i16) {
+    return false;
+  }
+
+  if (Op->getOpcode() != ISD::ADD && Op->getOpcode() != ISD::SUB) {
+    return false;
+  }
+
+  if (const ConstantSDNode *RHS = dyn_cast<ConstantSDNode>(Op->getOperand(1))) {
+    int RHSC = RHS->getSExtValue();
+    if (Op->getOpcode() == ISD::SUB)
+      RHSC = -RHSC;
+    if ((VT == MVT::i16 && RHSC != 2) || (VT == MVT::i8 && RHSC != 1)) {
+      return false;
+    }
+
+    Base = Op->getOperand(0);
+    Offset = DAG.getConstant(RHSC, DL, MVT::i8);
+    AM = ISD::POST_INC;
+
+    return true;
+  }
+
+  return false;
+}
+
+/// Return true if folding a constant offset
+/// with the given GlobalAddress is legal.  It is frequently not legal in
+/// PIC relocation models.
+bool AVRTargetLowering::isOffsetFoldingLegal(
+    const GlobalAddressSDNode *GA) const {
+  //:TODO: consider folding other operators like or,and,xor,...
+  return true;
+}
+
+//===----------------------------------------------------------------------===//
+//             Formal Arguments Calling Convention Implementation
+//===----------------------------------------------------------------------===//
+
+#include "AVRGenCallingConv.inc"
+
+/// For each argument in a function store the number of pieces it is composed
+/// of.
+static void parseFunctionArgs(const Function *F, const DataLayout *TD,
+                              SmallVectorImpl<unsigned> &Out) {
+  for (Argument const &Arg : F->args()) {
+    unsigned Bytes = (TD->getTypeSizeInBits(Arg.getType()) + 7) / 8;
+    Out.push_back((Bytes + 1) / 2);
+  }
+}
+
+/// For external symbols there is no function prototype information so we
+/// have to rely directly on argument sizes.
+static void parseExternFuncCallArgs(const SmallVectorImpl<ISD::OutputArg> &In,
+                                    SmallVectorImpl<unsigned> &Out) {
+  for (unsigned i = 0, e = In.size(); i != e;) {
+    unsigned Size = 0;
+    unsigned Offset = 0;
+    while ((i != e) && (In[i].PartOffset == Offset)) {
+      Offset += In[i].VT.getStoreSize();
+      ++i;
+      ++Size;
+    }
+    Out.push_back(Size);
+  }
+}
+
+static StringRef getFunctionName(TargetLowering::CallLoweringInfo &CLI) {
+  SDValue Callee = CLI.Callee;
+
+  if (const ExternalSymbolSDNode *G = dyn_cast<ExternalSymbolSDNode>(Callee)) {
+    return G->getSymbol();
+  } else if (const GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
+    return G->getGlobal()->getName();
+  } else {
+    llvm_unreachable("don't know how to get the name for this callee");
+  }
+}
+
+/// Analyze incoming and outgoing function arguments. We need custom C++ code
+/// to handle special constraints in the ABI like reversing the order of the
+/// pieces of splitted arguments. In addition, all pieces of a certain argument
+/// have to be passed either using registers or the stack but never mixing both.
+static void analyzeStandardArguments(TargetLowering::CallLoweringInfo *CLI,
+                                     const Function *F, const DataLayout *TD,
+                                     const SmallVectorImpl<ISD::OutputArg> *Outs,
+                                     const SmallVectorImpl<ISD::InputArg> *Ins,
+                                     CallingConv::ID CallConv,
+                                     SmallVectorImpl<CCValAssign> &ArgLocs,
+                                     CCState &CCInfo, bool IsCall, bool IsVarArg) {
+  static const MCPhysReg RegList8[] = {AVR::R24, AVR::R22, AVR::R20,
+                                       AVR::R18, AVR::R16, AVR::R14,
+                                       AVR::R12, AVR::R10, AVR::R8};
+  static const MCPhysReg RegList16[] = {AVR::R25R24, AVR::R23R22, AVR::R21R20,
+                                        AVR::R19R18, AVR::R17R16, AVR::R15R14,
+                                        AVR::R13R12, AVR::R11R10, AVR::R9R8};
+  if (IsVarArg) {
+    // Variadic functions do not need all the analisys below.
+    if (IsCall) {
+      CCInfo.AnalyzeCallOperands(*Outs, ArgCC_AVR_Vararg);
+    } else {
+      CCInfo.AnalyzeFormalArguments(*Ins, ArgCC_AVR_Vararg);
+    }
+    return;
+  }
+
+  // Fill in the Args array which will contain original argument sizes.
+  SmallVector<unsigned, 8> Args;
+  if (IsCall) {
+    parseExternFuncCallArgs(*Outs, Args);
+  } else {
+    assert(F != nullptr && "function should not be null");
+    parseFunctionArgs(F, TD, Args);
+  }
+
+  unsigned RegsLeft = array_lengthof(RegList8), ValNo = 0;
+  // Variadic functions always use the stack.
+  bool UsesStack = false;
+  for (unsigned i = 0, pos = 0, e = Args.size(); i != e; ++i) {
+    unsigned Size = Args[i];
+    MVT LocVT = (IsCall) ? (*Outs)[pos].VT : (*Ins)[pos].VT;
+
+    // If we have plenty of regs to pass the whole argument do it.
+    if (!UsesStack && (Size <= RegsLeft)) {
+      const MCPhysReg *RegList = (LocVT == MVT::i16) ? RegList16 : RegList8;
+
+      for (unsigned j = 0; j != Size; ++j) {
+        unsigned Reg = CCInfo.AllocateReg(
+            ArrayRef<MCPhysReg>(RegList, array_lengthof(RegList8)));
+        CCInfo.addLoc(
+            CCValAssign::getReg(ValNo++, LocVT, Reg, LocVT, CCValAssign::Full));
+        --RegsLeft;
+      }
+
+      // Reverse the order of the pieces to agree with the "big endian" format
+      // required in the calling convention ABI.
+      std::reverse(ArgLocs.begin() + pos, ArgLocs.begin() + pos + Size);
+    } else {
+      // Pass the rest of arguments using the stack.
+      UsesStack = true;
+      for (unsigned j = 0; j != Size; ++j) {
+        unsigned Offset = CCInfo.AllocateStack(
+            TD->getTypeAllocSize(EVT(LocVT).getTypeForEVT(CCInfo.getContext())),
+            TD->getABITypeAlignment(
+                EVT(LocVT).getTypeForEVT(CCInfo.getContext())));
+        CCInfo.addLoc(CCValAssign::getMem(ValNo++, LocVT, Offset, LocVT,
+                                          CCValAssign::Full));
+      }
+    }
+    pos += Size;
+  }
+}
+
+static void analyzeBuiltinArguments(TargetLowering::CallLoweringInfo &CLI,
+                                    const Function *F, const DataLayout *TD,
+                                    const SmallVectorImpl<ISD::OutputArg> *Outs,
+                                    const SmallVectorImpl<ISD::InputArg> *Ins,
+                                    CallingConv::ID CallConv,
+                                    SmallVectorImpl<CCValAssign> &ArgLocs,
+                                    CCState &CCInfo, bool IsCall, bool IsVarArg) {
+  StringRef FuncName = getFunctionName(CLI);
+
+  if (FuncName.startswith("__udivmod") || FuncName.startswith("__divmod")) {
+    CCInfo.AnalyzeCallOperands(*Outs, ArgCC_AVR_BUILTIN_DIV);
+  } else {
+    analyzeStandardArguments(&CLI, F, TD, Outs, Ins,
+                             CallConv, ArgLocs, CCInfo,
+                             IsCall, IsVarArg);
+  }
+}
+
+static void analyzeArguments(TargetLowering::CallLoweringInfo *CLI,
+                             const Function *F, const DataLayout *TD,
+                             const SmallVectorImpl<ISD::OutputArg> *Outs,
+                             const SmallVectorImpl<ISD::InputArg> *Ins,
+                             CallingConv::ID CallConv,
+                             SmallVectorImpl<CCValAssign> &ArgLocs,
+                             CCState &CCInfo, bool IsCall, bool IsVarArg) {
+  switch (CallConv) {
+    case CallingConv::AVR_BUILTIN: {
+      analyzeBuiltinArguments(*CLI, F, TD, Outs, Ins,
+                              CallConv, ArgLocs, CCInfo,
+                              IsCall, IsVarArg);
+      return;
+    }
+    default: {
+      analyzeStandardArguments(CLI, F, TD, Outs, Ins,
+                               CallConv, ArgLocs, CCInfo,
+                               IsCall, IsVarArg);
+      return;
+    }
+  }
+}
+
+SDValue AVRTargetLowering::LowerFormalArguments(
+    SDValue Chain, CallingConv::ID CallConv, bool isVarArg,
+    const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &dl, SelectionDAG &DAG,
+    SmallVectorImpl<SDValue> &InVals) const {
+  MachineFunction &MF = DAG.getMachineFunction();
+  MachineFrameInfo &MFI = MF.getFrameInfo();
+  auto DL = DAG.getDataLayout();
+
+  // Assign locations to all of the incoming arguments.
+  SmallVector<CCValAssign, 16> ArgLocs;
+  CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(), ArgLocs,
+                 *DAG.getContext());
+
+  analyzeArguments(nullptr, MF.getFunction(), &DL, 0, &Ins, CallConv, ArgLocs, CCInfo,
+                   false, isVarArg);
+
+  SDValue ArgValue;
+  for (CCValAssign &VA : ArgLocs) {
+
+    // Arguments stored on registers.
+    if (VA.isRegLoc()) {
+      EVT RegVT = VA.getLocVT();
+      const TargetRegisterClass *RC;
+      if (RegVT == MVT::i8) {
+        RC = &AVR::GPR8RegClass;
+      } else if (RegVT == MVT::i16) {
+        RC = &AVR::DREGSRegClass;
+      } else {
+        llvm_unreachable("Unknown argument type!");
+      }
+
+      unsigned Reg = MF.addLiveIn(VA.getLocReg(), RC);
+      ArgValue = DAG.getCopyFromReg(Chain, dl, Reg, RegVT);
+
+      // :NOTE: Clang should not promote any i8 into i16 but for safety the
+      // following code will handle zexts or sexts generated by other
+      // front ends. Otherwise:
+      // If this is an 8 bit value, it is really passed promoted
+      // to 16 bits. Insert an assert[sz]ext to capture this, then
+      // truncate to the right size.
+      switch (VA.getLocInfo()) {
+      default:
+        llvm_unreachable("Unknown loc info!");
+      case CCValAssign::Full:
+        break;
+      case CCValAssign::BCvt:
+        ArgValue = DAG.getNode(ISD::BITCAST, dl, VA.getValVT(), ArgValue);
+        break;
+      case CCValAssign::SExt:
+        ArgValue = DAG.getNode(ISD::AssertSext, dl, RegVT, ArgValue,
+                               DAG.getValueType(VA.getValVT()));
+        ArgValue = DAG.getNode(ISD::TRUNCATE, dl, VA.getValVT(), ArgValue);
+        break;
+      case CCValAssign::ZExt:
+        ArgValue = DAG.getNode(ISD::AssertZext, dl, RegVT, ArgValue,
+                               DAG.getValueType(VA.getValVT()));
+        ArgValue = DAG.getNode(ISD::TRUNCATE, dl, VA.getValVT(), ArgValue);
+        break;
+      }
+
+      InVals.push_back(ArgValue);
+    } else {
+      // Sanity check.
+      assert(VA.isMemLoc());
+
+      EVT LocVT = VA.getLocVT();
+
+      // Create the frame index object for this incoming parameter.
+      int FI = MFI.CreateFixedObject(LocVT.getSizeInBits() / 8,
+                                     VA.getLocMemOffset(), true);
+
+      // Create the SelectionDAG nodes corresponding to a load
+      // from this parameter.
+      SDValue FIN = DAG.getFrameIndex(FI, getPointerTy(DL));
+      InVals.push_back(DAG.getLoad(LocVT, dl, Chain, FIN,
+                                   MachinePointerInfo::getFixedStack(MF, FI),
+                                   0));
+    }
+  }
+
+  // If the function takes variable number of arguments, make a frame index for
+  // the start of the first vararg value... for expansion of llvm.va_start.
+  if (isVarArg) {
+    unsigned StackSize = CCInfo.getNextStackOffset();
+    AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();
+
+    AFI->setVarArgsFrameIndex(MFI.CreateFixedObject(2, StackSize, true));
+  }
+
+  return Chain;
+}
+
+//===----------------------------------------------------------------------===//
+//                  Call Calling Convention Implementation
+//===----------------------------------------------------------------------===//
+
+SDValue AVRTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
+                                     SmallVectorImpl<SDValue> &InVals) const {
+  SelectionDAG &DAG = CLI.DAG;
+  SDLoc &DL = CLI.DL;
+  SmallVectorImpl<ISD::OutputArg> &Outs = CLI.Outs;
+  SmallVectorImpl<SDValue> &OutVals = CLI.OutVals;
+  SmallVectorImpl<ISD::InputArg> &Ins = CLI.Ins;
+  SDValue Chain = CLI.Chain;
+  SDValue Callee = CLI.Callee;
+  bool &isTailCall = CLI.IsTailCall;
+  CallingConv::ID CallConv = CLI.CallConv;
+  bool isVarArg = CLI.IsVarArg;
+
+  MachineFunction &MF = DAG.getMachineFunction();
+
+  // AVR does not yet support tail call optimization.
+  isTailCall = false;
+
+  // Analyze operands of the call, assigning locations to each operand.
+  SmallVector<CCValAssign, 16> ArgLocs;
+  CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(), ArgLocs,
+                 *DAG.getContext());
+
+  // If the callee is a GlobalAddress/ExternalSymbol node (quite common, every
+  // direct call is) turn it into a TargetGlobalAddress/TargetExternalSymbol
+  // node so that legalize doesn't hack it.
+  const Function *F = 0;
+  if (const GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
+    const GlobalValue *GV = G->getGlobal();
+
+    F = cast<Function>(GV);
+    Callee =
+        DAG.getTargetGlobalAddress(GV, DL, getPointerTy(DAG.getDataLayout()));
+  } else if (const ExternalSymbolSDNode *ES =
+                 dyn_cast<ExternalSymbolSDNode>(Callee)) {
+    Callee = DAG.getTargetExternalSymbol(ES->getSymbol(),
+                                         getPointerTy(DAG.getDataLayout()));
+  }
+
+  analyzeArguments(&CLI, F, &DAG.getDataLayout(), &Outs, 0, CallConv, ArgLocs, CCInfo,
+                   true, isVarArg);
+
+  // Get a count of how many bytes are to be pushed on the stack.
+  unsigned NumBytes = CCInfo.getNextStackOffset();
+
+  Chain = DAG.getCALLSEQ_START(Chain, DAG.getIntPtrConstant(NumBytes, DL, true),
+                               DL);
+
+  SmallVector<std::pair<unsigned, SDValue>, 8> RegsToPass;
+
+  // First, walk the register assignments, inserting copies.
+  unsigned AI, AE;
+  bool HasStackArgs = false;
+  for (AI = 0, AE = ArgLocs.size(); AI != AE; ++AI) {
+    CCValAssign &VA = ArgLocs[AI];
+    EVT RegVT = VA.getLocVT();
+    SDValue Arg = OutVals[AI];
+
+    // Promote the value if needed. With Clang this should not happen.
+    switch (VA.getLocInfo()) {
+    default:
+      llvm_unreachable("Unknown loc info!");
+    case CCValAssign::Full:
+      break;
+    case CCValAssign::SExt:
+      Arg = DAG.getNode(ISD::SIGN_EXTEND, DL, RegVT, Arg);
+      break;
+    case CCValAssign::ZExt:
+      Arg = DAG.getNode(ISD::ZERO_EXTEND, DL, RegVT, Arg);
+      break;
+    case CCValAssign::AExt:
+      Arg = DAG.getNode(ISD::ANY_EXTEND, DL, RegVT, Arg);
+      break;
+    case CCValAssign::BCvt:
+      Arg = DAG.getNode(ISD::BITCAST, DL, RegVT, Arg);
+      break;
+    }
+
+    // Stop when we encounter a stack argument, we need to process them
+    // in reverse order in the loop below.
+    if (VA.isMemLoc()) {
+      HasStackArgs = true;
+      break;
+    }
+
+    // Arguments that can be passed on registers must be kept in the RegsToPass
+    // vector.
+    RegsToPass.push_back(std::make_pair(VA.getLocReg(), Arg));
+  }
+
+  // Second, stack arguments have to walked in reverse order by inserting
+  // chained stores, this ensures their order is not changed by the scheduler
+  // and that the push instruction sequence generated is correct, otherwise they
+  // can be freely intermixed.
+  if (HasStackArgs) {
+    for (AE = AI, AI = ArgLocs.size(); AI != AE; --AI) {
+      unsigned Loc = AI - 1;
+      CCValAssign &VA = ArgLocs[Loc];
+      SDValue Arg = OutVals[Loc];
+
+      assert(VA.isMemLoc());
+
+      // SP points to one stack slot further so add one to adjust it.
+      SDValue PtrOff = DAG.getNode(
+          ISD::ADD, DL, getPointerTy(DAG.getDataLayout()),
+          DAG.getRegister(AVR::SP, getPointerTy(DAG.getDataLayout())),
+          DAG.getIntPtrConstant(VA.getLocMemOffset() + 1, DL));
+
+      Chain =
+          DAG.getStore(Chain, DL, Arg, PtrOff,
+                       MachinePointerInfo::getStack(MF, VA.getLocMemOffset()),
+                       0);
+    }
+  }
+
+  // Build a sequence of copy-to-reg nodes chained together with token chain and
+  // flag operands which copy the outgoing args into registers.  The InFlag in
+  // necessary since all emited instructions must be stuck together.
+  SDValue InFlag;
+  for (auto Reg : RegsToPass) {
+    Chain = DAG.getCopyToReg(Chain, DL, Reg.first, Reg.second, InFlag);
+    InFlag = Chain.getValue(1);
+  }
+
+  // Returns a chain & a flag for retval copy to use.
+  SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
+  SmallVector<SDValue, 8> Ops;
+  Ops.push_back(Chain);
+  Ops.push_back(Callee);
+
+  // Add argument registers to the end of the list so that they are known live
+  // into the call.
+  for (auto Reg : RegsToPass) {
+    Ops.push_back(DAG.getRegister(Reg.first, Reg.second.getValueType()));
+  }
+
+  // Add a register mask operand representing the call-preserved registers.
+  const AVRTargetMachine &TM = (const AVRTargetMachine &)getTargetMachine();
+  const TargetRegisterInfo *TRI = TM.getSubtargetImpl()->getRegisterInfo();
+  const uint32_t *Mask =
+      TRI->getCallPreservedMask(DAG.getMachineFunction(), CallConv);
+  assert(Mask && "Missing call preserved mask for calling convention");
+  Ops.push_back(DAG.getRegisterMask(Mask));
+
+  if (InFlag.getNode()) {
+    Ops.push_back(InFlag);
+  }
+
+  Chain = DAG.getNode(AVRISD::CALL, DL, NodeTys, Ops);
+  InFlag = Chain.getValue(1);
+
+  // Create the CALLSEQ_END node.
+  Chain = DAG.getCALLSEQ_END(Chain, DAG.getIntPtrConstant(NumBytes, DL, true),
+                             DAG.getIntPtrConstant(0, DL, true), InFlag, DL);
+
+  if (!Ins.empty()) {
+    InFlag = Chain.getValue(1);
+  }
+
+  // Handle result values, copying them out of physregs into vregs that we
+  // return.
+  return LowerCallResult(Chain, InFlag, CallConv, isVarArg, Ins, DL, DAG,
+                         InVals);
+}
+
+/// Lower the result values of a call into the
+/// appropriate copies out of appropriate physical registers.
+///
+SDValue AVRTargetLowering::LowerCallResult(
+    SDValue Chain, SDValue InFlag, CallingConv::ID CallConv, bool isVarArg,
+    const SmallVectorImpl<ISD::InputArg> &Ins, const SDLoc &dl, SelectionDAG &DAG,
+    SmallVectorImpl<SDValue> &InVals) const {
+
+  // Assign locations to each value returned by this call.
+  SmallVector<CCValAssign, 16> RVLocs;
+  CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(), RVLocs,
+                 *DAG.getContext());
+
+  // Handle runtime calling convs.
+  auto CCFunction = CCAssignFnForReturn(CallConv);
+  CCInfo.AnalyzeCallResult(Ins, CCFunction);
+
+  if (CallConv != CallingConv::AVR_BUILTIN && RVLocs.size() > 1) {
+    // Reverse splitted return values to get the "big endian" format required
+    // to agree with the calling convention ABI.
+    std::reverse(RVLocs.begin(), RVLocs.end());
+  }
+
+  // Copy all of the result registers out of their specified physreg.
+  for (CCValAssign const &RVLoc : RVLocs) {
+    Chain = DAG.getCopyFromReg(Chain, dl, RVLoc.getLocReg(), RVLoc.getValVT(),
+                               InFlag)
+                .getValue(1);
+    InFlag = Chain.getValue(2);
+    InVals.push_back(Chain.getValue(0));
+  }
+
+  return Chain;
+}
+
+//===----------------------------------------------------------------------===//
+//               Return Value Calling Convention Implementation
+//===----------------------------------------------------------------------===//
+
+CCAssignFn *AVRTargetLowering::CCAssignFnForReturn(CallingConv::ID CC) const {
+  switch (CC) {
+  case CallingConv::AVR_BUILTIN:
+    return RetCC_AVR_BUILTIN;
+  default:
+    return RetCC_AVR;
+  }
+}
+
+bool
+AVRTargetLowering::CanLowerReturn(CallingConv::ID CallConv,
+                                  MachineFunction &MF, bool isVarArg,
+                                  const SmallVectorImpl<ISD::OutputArg> &Outs,
+                                  LLVMContext &Context) const
+{
+  SmallVector<CCValAssign, 16> RVLocs;
+  CCState CCInfo(CallConv, isVarArg, MF, RVLocs, Context);
+  auto CCFunction = CCAssignFnForReturn(CallConv);
+  return CCInfo.CheckReturn(Outs, CCFunction);
+}
+
+SDValue
+AVRTargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
+                               bool isVarArg,
+                               const SmallVectorImpl<ISD::OutputArg> &Outs,
+                               const SmallVectorImpl<SDValue> &OutVals,
+                               const SDLoc &dl, SelectionDAG &DAG) const {
+  // CCValAssign - represent the assignment of the return value to locations.
+  SmallVector<CCValAssign, 16> RVLocs;
+
+  // CCState - Info about the registers and stack slot.
+  CCState CCInfo(CallConv, isVarArg, DAG.getMachineFunction(), RVLocs,
+                 *DAG.getContext());
+
+  // Analyze return values.
+  auto CCFunction = CCAssignFnForReturn(CallConv);
+  CCInfo.AnalyzeReturn(Outs, CCFunction);
+
+  // If this is the first return lowered for this function, add the regs to
+  // the liveout set for the function.
+  MachineFunction &MF = DAG.getMachineFunction();
+  unsigned e = RVLocs.size();
+
+  // Reverse splitted return values to get the "big endian" format required
+  // to agree with the calling convention ABI.
+  if (e > 1) {
+    std::reverse(RVLocs.begin(), RVLocs.end());
+  }
+
+  SDValue Flag;
+  SmallVector<SDValue, 4> RetOps(1, Chain);
+  // Copy the result values into the output registers.
+  for (unsigned i = 0; i != e; ++i) {
+    CCValAssign &VA = RVLocs[i];
+    assert(VA.isRegLoc() && "Can only return in registers!");
+
+    Chain = DAG.getCopyToReg(Chain, dl, VA.getLocReg(), OutVals[i], Flag);
+
+    // Guarantee that all emitted copies are stuck together with flags.
+    Flag = Chain.getValue(1);
+    RetOps.push_back(DAG.getRegister(VA.getLocReg(), VA.getLocVT()));
+  }
+
+  // Don't emit the ret/reti instruction when the naked attribute is present in
+  // the function being compiled.
+  if (MF.getFunction()->getAttributes().hasAttribute(
+          AttributeSet::FunctionIndex, Attribute::Naked)) {
+    return Chain;
+  }
+
+  unsigned RetOpc =
+      (CallConv == CallingConv::AVR_INTR || CallConv == CallingConv::AVR_SIGNAL)
+          ? AVRISD::RETI_FLAG
+          : AVRISD::RET_FLAG;
+
+  RetOps[0] = Chain; // Update chain.
+
+  if (Flag.getNode()) {
+    RetOps.push_back(Flag);
+  }
+
+  return DAG.getNode(RetOpc, dl, MVT::Other, RetOps);
+}
+
+//===----------------------------------------------------------------------===//
+//  Custom Inserters
+//===----------------------------------------------------------------------===//
+
+MachineBasicBlock *AVRTargetLowering::insertShift(MachineInstr &MI,
+                                                  MachineBasicBlock *BB) const {
+  unsigned Opc;
+  const TargetRegisterClass *RC;
+  MachineFunction *F = BB->getParent();
+  MachineRegisterInfo &RI = F->getRegInfo();
+  const AVRTargetMachine &TM = (const AVRTargetMachine &)getTargetMachine();
+  const TargetInstrInfo &TII = *TM.getSubtargetImpl()->getInstrInfo();
+  DebugLoc dl = MI.getDebugLoc();
+
+  switch (MI.getOpcode()) {
+  default:
+    llvm_unreachable("Invalid shift opcode!");
+  case AVR::Lsl8:
+    Opc = AVR::LSLRd;
+    RC = &AVR::GPR8RegClass;
+    break;
+  case AVR::Lsl16:
+    Opc = AVR::LSLWRd;
+    RC = &AVR::DREGSRegClass;
+    break;
+  case AVR::Asr8:
+    Opc = AVR::ASRRd;
+    RC = &AVR::GPR8RegClass;
+    break;
+  case AVR::Asr16:
+    Opc = AVR::ASRWRd;
+    RC = &AVR::DREGSRegClass;
+    break;
+  case AVR::Lsr8:
+    Opc = AVR::LSRRd;
+    RC = &AVR::GPR8RegClass;
+    break;
+  case AVR::Lsr16:
+    Opc = AVR::LSRWRd;
+    RC = &AVR::DREGSRegClass;
+    break;
+  }
+
+  const BasicBlock *LLVM_BB = BB->getBasicBlock();
+  MachineFunction::iterator I = BB->getParent()->begin();
+  ++I;
+
+  // Create loop block.
+  MachineBasicBlock *LoopBB = F->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *RemBB = F->CreateMachineBasicBlock(LLVM_BB);
+
+  F->insert(I, LoopBB);
+  F->insert(I, RemBB);
+
+  // Update machine-CFG edges by transferring all successors of the current
+  // block to the block containing instructions after shift.
+  RemBB->splice(RemBB->begin(), BB, std::next(MachineBasicBlock::iterator(MI)),
+                BB->end());
+  RemBB->transferSuccessorsAndUpdatePHIs(BB);
+
+  // Add adges BB => LoopBB => RemBB, BB => RemBB, LoopBB => LoopBB.
+  BB->addSuccessor(LoopBB);
+  BB->addSuccessor(RemBB);
+  LoopBB->addSuccessor(RemBB);
+  LoopBB->addSuccessor(LoopBB);
+
+  unsigned ShiftAmtReg = RI.createVirtualRegister(&AVR::LD8RegClass);
+  unsigned ShiftAmtReg2 = RI.createVirtualRegister(&AVR::LD8RegClass);
+  unsigned ShiftReg = RI.createVirtualRegister(RC);
+  unsigned ShiftReg2 = RI.createVirtualRegister(RC);
+  unsigned ShiftAmtSrcReg = MI.getOperand(2).getReg();
+  unsigned SrcReg = MI.getOperand(1).getReg();
+  unsigned DstReg = MI.getOperand(0).getReg();
+
+  // BB:
+  // cp 0, N
+  // breq RemBB
+  BuildMI(BB, dl, TII.get(AVR::CPRdRr)).addReg(ShiftAmtSrcReg).addReg(AVR::R0);
+  BuildMI(BB, dl, TII.get(AVR::BREQk)).addMBB(RemBB);
+
+  // LoopBB:
+  // ShiftReg = phi [%SrcReg, BB], [%ShiftReg2, LoopBB]
+  // ShiftAmt = phi [%N, BB],      [%ShiftAmt2, LoopBB]
+  // ShiftReg2 = shift ShiftReg
+  // ShiftAmt2 = ShiftAmt - 1;
+  BuildMI(LoopBB, dl, TII.get(AVR::PHI), ShiftReg)
+      .addReg(SrcReg)
+      .addMBB(BB)
+      .addReg(ShiftReg2)
+      .addMBB(LoopBB);
+  BuildMI(LoopBB, dl, TII.get(AVR::PHI), ShiftAmtReg)
+      .addReg(ShiftAmtSrcReg)
+      .addMBB(BB)
+      .addReg(ShiftAmtReg2)
+      .addMBB(LoopBB);
+  BuildMI(LoopBB, dl, TII.get(Opc), ShiftReg2).addReg(ShiftReg);
+  BuildMI(LoopBB, dl, TII.get(AVR::SUBIRdK), ShiftAmtReg2)
+      .addReg(ShiftAmtReg)
+      .addImm(1);
+  BuildMI(LoopBB, dl, TII.get(AVR::BRNEk)).addMBB(LoopBB);
+
+  // RemBB:
+  // DestReg = phi [%SrcReg, BB], [%ShiftReg, LoopBB]
+  BuildMI(*RemBB, RemBB->begin(), dl, TII.get(AVR::PHI), DstReg)
+      .addReg(SrcReg)
+      .addMBB(BB)
+      .addReg(ShiftReg2)
+      .addMBB(LoopBB);
+
+  MI.eraseFromParent(); // The pseudo instruction is gone now.
+  return RemBB;
+}
+
+inline bool isCopyMulResult(MachineBasicBlock::iterator const &I) {
+  if (I->getOpcode() == AVR::COPY) {
+    unsigned SrcReg = I->getOperand(1).getReg();
+    return (SrcReg == AVR::R0 || SrcReg == AVR::R1);
+  }
+
+  return false;
+}
+
+// The mul instructions wreak havock on our zero_reg R1. We need to clear it
+// after the result has been evacuated. This is probably not the best way to do
+// it, but it works for now.
+MachineBasicBlock *AVRTargetLowering::insertMul(MachineInstr &MI,
+                                                MachineBasicBlock *BB) const {
+  const AVRTargetMachine &TM = (const AVRTargetMachine &)getTargetMachine();
+  const TargetInstrInfo &TII = *TM.getSubtargetImpl()->getInstrInfo();
+  MachineBasicBlock::iterator I(MI);
+  ++I; // in any case insert *after* the mul instruction
+  if (isCopyMulResult(I))
+    ++I;
+  if (isCopyMulResult(I))
+    ++I;
+  BuildMI(*BB, I, MI.getDebugLoc(), TII.get(AVR::EORRdRr), AVR::R1)
+      .addReg(AVR::R1)
+      .addReg(AVR::R1);
+  return BB;
+}
+
+MachineBasicBlock *
+AVRTargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI,
+                                               MachineBasicBlock *MBB) const {
+  int Opc = MI.getOpcode();
+
+  // Pseudo shift instructions with a non constant shift amount are expanded
+  // into a loop.
+  switch (Opc) {
+  case AVR::Lsl8:
+  case AVR::Lsl16:
+  case AVR::Lsr8:
+  case AVR::Lsr16:
+  case AVR::Asr8:
+  case AVR::Asr16:
+    return insertShift(MI, MBB);
+  case AVR::MULRdRr:
+  case AVR::MULSRdRr:
+    return insertMul(MI, MBB);
+  }
+
+  assert((Opc == AVR::Select16 || Opc == AVR::Select8) &&
+         "Unexpected instr type to insert");
+
+  const AVRInstrInfo &TII = (const AVRInstrInfo &)*MI.getParent()
+                                ->getParent()
+                                ->getSubtarget()
+                                .getInstrInfo();
+  DebugLoc dl = MI.getDebugLoc();
+
+  // To "insert" a SELECT instruction, we insert the diamond
+  // control-flow pattern. The incoming instruction knows the
+  // destination vreg to set, the condition code register to branch
+  // on, the true/false values to select between, and a branch opcode
+  // to use.
+
+  MachineFunction *MF = MBB->getParent();
+  const BasicBlock *LLVM_BB = MBB->getBasicBlock();
+  MachineBasicBlock *trueMBB = MF->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *falseMBB = MF->CreateMachineBasicBlock(LLVM_BB);
+
+  MachineFunction::iterator I = MBB->getParent()->begin();
+  ++I;
+  MF->insert(I, trueMBB);
+  MF->insert(I, falseMBB);
+
+  // Transfer remaining instructions and all successors of the current
+  // block to the block which will contain the Phi node for the
+  // select.
+  trueMBB->splice(trueMBB->begin(), MBB,
+                  std::next(MachineBasicBlock::iterator(MI)), MBB->end());
+  trueMBB->transferSuccessorsAndUpdatePHIs(MBB);
+
+  AVRCC::CondCodes CC = (AVRCC::CondCodes)MI.getOperand(3).getImm();
+  BuildMI(MBB, dl, TII.getBrCond(CC)).addMBB(trueMBB);
+  BuildMI(MBB, dl, TII.get(AVR::RJMPk)).addMBB(falseMBB);
+  MBB->addSuccessor(falseMBB);
+  MBB->addSuccessor(trueMBB);
+
+  // Unconditionally flow back to the true block
+  BuildMI(falseMBB, dl, TII.get(AVR::RJMPk)).addMBB(trueMBB);
+  falseMBB->addSuccessor(trueMBB);
+
+  // Set up the Phi node to determine where we came from
+  BuildMI(*trueMBB, trueMBB->begin(), dl, TII.get(AVR::PHI), MI.getOperand(0).getReg())
+    .addReg(MI.getOperand(1).getReg())
+    .addMBB(MBB)
+    .addReg(MI.getOperand(2).getReg())
+    .addMBB(falseMBB) ;
+
+  MI.eraseFromParent(); // The pseudo instruction is gone now.
+  return trueMBB;
+}
+
+//===----------------------------------------------------------------------===//
+//  Inline Asm Support
+//===----------------------------------------------------------------------===//
+
+AVRTargetLowering::ConstraintType
+AVRTargetLowering::getConstraintType(StringRef Constraint) const {
+  if (Constraint.size() == 1) {
+    // See http://www.nongnu.org/avr-libc/user-manual/inline_asm.html
+    switch (Constraint[0]) {
+    case 'a': // Simple upper registers
+    case 'b': // Base pointer registers pairs
+    case 'd': // Upper register
+    case 'l': // Lower registers
+    case 'e': // Pointer register pairs
+    case 'q': // Stack pointer register
+    case 'r': // Any register
+    case 'w': // Special upper register pairs
+      return C_RegisterClass;
+    case 't': // Temporary register
+    case 'x': case 'X': // Pointer register pair X
+    case 'y': case 'Y': // Pointer register pair Y
+    case 'z': case 'Z': // Pointer register pair Z
+      return C_Register;
+    case 'Q': // A memory address based on Y or Z pointer with displacement.
+      return C_Memory;
+    case 'G': // Floating point constant
+    case 'I': // 6-bit positive integer constant
+    case 'J': // 6-bit negative integer constant
+    case 'K': // Integer constant (Range: 2)
+    case 'L': // Integer constant (Range: 0)
+    case 'M': // 8-bit integer constant
+    case 'N': // Integer constant (Range: -1)
+    case 'O': // Integer constant (Range: 8, 16, 24)
+    case 'P': // Integer constant (Range: 1)
+    case 'R': // Integer constant (Range: -6 to 5)x
+      return C_Other;
+    default:
+      break;
+    }
+  }
+
+  return TargetLowering::getConstraintType(Constraint);
+}
+
+unsigned
+AVRTargetLowering::getInlineAsmMemConstraint(StringRef ConstraintCode) const {
+  // Not sure if this is actually the right thing to do, but we got to do
+  // *something* [agnat]
+  switch (ConstraintCode[0]) {
+  case 'Q':
+    return InlineAsm::Constraint_Q;
+  }
+  return TargetLowering::getInlineAsmMemConstraint(ConstraintCode);
+}
+
+AVRTargetLowering::ConstraintWeight
+AVRTargetLowering::getSingleConstraintMatchWeight(
+    AsmOperandInfo &info, const char *constraint) const {
+  ConstraintWeight weight = CW_Invalid;
+  Value *CallOperandVal = info.CallOperandVal;
+
+  // If we don't have a value, we can't do a match,
+  // but allow it at the lowest weight.
+  // (this behaviour has been copied from the ARM backend)
+  if (CallOperandVal == NULL) {
+    return CW_Default;
+  }
+
+  // Look at the constraint type.
+  switch (*constraint) {
+  default:
+    weight = TargetLowering::getSingleConstraintMatchWeight(info, constraint);
+    break;
+  case 'd':
+  case 'r':
+  case 'l':
+    weight = CW_Register;
+    break;
+  case 'a':
+  case 'b':
+  case 'e':
+  case 'q':
+  case 't':
+  case 'w':
+  case 'x': case 'X':
+  case 'y': case 'Y':
+  case 'z': case 'Z':
+    weight = CW_SpecificReg;
+    break;
+  case 'G':
+    if (const ConstantFP *C = dyn_cast<ConstantFP>(CallOperandVal)) {
+      if (C->isZero()) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'I':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if (isUInt<6>(C->getZExtValue())) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'J':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if ((C->getSExtValue() >= -63) && (C->getSExtValue() <= 0)) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'K':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if (C->getZExtValue() == 2) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'L':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if (C->getZExtValue() == 0) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'M':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if (isUInt<8>(C->getZExtValue())) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'N':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if (C->getSExtValue() == -1) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'O':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if ((C->getZExtValue() == 8) || (C->getZExtValue() == 16) ||
+          (C->getZExtValue() == 24)) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'P':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if (C->getZExtValue() == 1) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'R':
+    if (const ConstantInt *C = dyn_cast<ConstantInt>(CallOperandVal)) {
+      if ((C->getSExtValue() >= -6) && (C->getSExtValue() <= 5)) {
+        weight = CW_Constant;
+      }
+    }
+    break;
+  case 'Q':
+    weight = CW_Memory;
+    break;
+  }
+
+  return weight;
+}
+
+std::pair<unsigned, const TargetRegisterClass *>
+AVRTargetLowering::getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
+                                                StringRef Constraint,
+                                                MVT VT) const {
+  auto STI = static_cast<const AVRTargetMachine &>(this->getTargetMachine())
+                 .getSubtargetImpl();
+
+  // We only support i8 and i16.
+  //
+  //:FIXME: remove this assert for now since it gets sometimes executed
+  // assert((VT == MVT::i16 || VT == MVT::i8) && "Wrong operand type.");
+
+  if (Constraint.size() == 1) {
+    switch (Constraint[0]) {
+    case 'a': // Simple upper registers r16..r23.
+      return std::make_pair(0U, &AVR::LD8loRegClass);
+    case 'b': // Base pointer registers: y, z.
+      return std::make_pair(0U, &AVR::PTRDISPREGSRegClass);
+    case 'd': // Upper registers r16..r31.
+      return std::make_pair(0U, &AVR::LD8RegClass);
+    case 'l': // Lower registers r0..r15.
+      return std::make_pair(0U, &AVR::GPR8loRegClass);
+    case 'e': // Pointer register pairs: x, y, z.
+      return std::make_pair(0U, &AVR::PTRREGSRegClass);
+    case 'q': // Stack pointer register: SPH:SPL.
+      return std::make_pair(0U, &AVR::GPRSPRegClass);
+    case 'r': // Any register: r0..r31.
+      if (VT == MVT::i8) {
+        return std::make_pair(0U, &AVR::GPR8RegClass);
+      } else {
+        return std::make_pair(0U, &AVR::DREGSRegClass);
+      }
+    case 't': // Temporary register: r0.
+      return std::make_pair(unsigned(AVR::R0), &AVR::GPR8RegClass);
+    case 'w': // Special upper register pairs: r24, r26, r28, r30.
+      return std::make_pair(0U, &AVR::IWREGSRegClass);
+    case 'x': // Pointer register pair X: r27:r26.
+    case 'X':
+      return std::make_pair(unsigned(AVR::R27R26), &AVR::PTRREGSRegClass);
+    case 'y': // Pointer register pair Y: r29:r28.
+    case 'Y':
+      return std::make_pair(unsigned(AVR::R29R28), &AVR::PTRREGSRegClass);
+    case 'z': // Pointer register pair Z: r31:r30.
+    case 'Z':
+      return std::make_pair(unsigned(AVR::R31R30), &AVR::PTRREGSRegClass);
+    default:
+      break;
+    }
+  }
+
+  return TargetLowering::getRegForInlineAsmConstraint(STI->getRegisterInfo(),
+                                                      Constraint, VT);
+}
+
+void AVRTargetLowering::LowerAsmOperandForConstraint(SDValue Op,
+                                                     std::string &Constraint,
+                                                     std::vector<SDValue> &Ops,
+                                                     SelectionDAG &DAG) const {
+  SDValue Result(0, 0);
+  SDLoc DL(Op);
+  EVT Ty = Op.getValueType();
+
+  // Currently only support length 1 constraints.
+  if (Constraint.length() != 1) {
+    return;
+  }
+
+  char ConstraintLetter = Constraint[0];
+  switch (ConstraintLetter) {
+  default:
+    break;
+  // Deal with integers first:
+  case 'I':
+  case 'J':
+  case 'K':
+  case 'L':
+  case 'M':
+  case 'N':
+  case 'O':
+  case 'P':
+  case 'R': {
+    const ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op);
+    if (!C) {
+      return;
+    }
+
+    int64_t CVal64 = C->getSExtValue();
+    uint64_t CUVal64 = C->getZExtValue();
+    switch (ConstraintLetter) {
+    case 'I': // 0..63
+      if (!isUInt<6>(CUVal64))
+        return;
+      Result = DAG.getTargetConstant(CUVal64, DL, Ty);
+      break;
+    case 'J': // -63..0
+      if (CVal64 < -63 || CVal64 > 0)
+        return;
+      Result = DAG.getTargetConstant(CVal64, DL, Ty);
+      break;
+    case 'K': // 2
+      if (CUVal64 != 2)
+        return;
+      Result = DAG.getTargetConstant(CUVal64, DL, Ty);
+      break;
+    case 'L': // 0
+      if (CUVal64 != 0)
+        return;
+      Result = DAG.getTargetConstant(CUVal64, DL, Ty);
+      break;
+    case 'M': // 0..255
+      if (!isUInt<8>(CUVal64))
+        return;
+      // i8 type may be printed as a negative number,
+      // e.g. 254 would be printed as -2,
+      // so we force it to i16 at least.
+      if (Ty.getSimpleVT() == MVT::i8) {
+        Ty = MVT::i16;
+      }
+      Result = DAG.getTargetConstant(CUVal64, DL, Ty);
+      break;
+    case 'N': // -1
+      if (CVal64 != -1)
+        return;
+      Result = DAG.getTargetConstant(CVal64, DL, Ty);
+      break;
+    case 'O': // 8, 16, 24
+      if (CUVal64 != 8 && CUVal64 != 16 && CUVal64 != 24)
+        return;
+      Result = DAG.getTargetConstant(CUVal64, DL, Ty);
+      break;
+    case 'P': // 1
+      if (CUVal64 != 1)
+        return;
+      Result = DAG.getTargetConstant(CUVal64, DL, Ty);
+      break;
+    case 'R': // -6..5
+      if (CVal64 < -6 || CVal64 > 5)
+        return;
+      Result = DAG.getTargetConstant(CVal64, DL, Ty);
+      break;
+    }
+
+    break;
+  }
+  case 'G':
+    const ConstantFPSDNode *FC = dyn_cast<ConstantFPSDNode>(Op);
+    if (!FC || !FC->isZero())
+      return;
+    // Soften float to i8 0
+    Result = DAG.getTargetConstant(0, DL, MVT::i8);
+    break;
+  }
+
+  if (Result.getNode()) {
+    Ops.push_back(Result);
+    return;
+  }
+
+  return TargetLowering::LowerAsmOperandForConstraint(Op, Constraint, Ops, DAG);
+}
+
+} // end of namespace llvm
+

lib/Target/AVR/CMakeLists.txt

 set(LLVM_TARGET_DEFINITIONS AVR.td)
 
 tablegen(LLVM AVRGenAsmMatcher.inc -gen-asm-matcher)
 tablegen(LLVM AVRGenRegisterInfo.inc -gen-register-info)
 tablegen(LLVM AVRGenInstrInfo.inc -gen-instr-info)
 tablegen(LLVM AVRGenCallingConv.inc -gen-callingconv)
 tablegen(LLVM AVRGenSubtargetInfo.inc -gen-subtarget)
 add_public_tablegen_target(AVRCommonTableGen)
 
 add_llvm_target(AVRCodeGen
   AVRInstrInfo.cpp
+  AVRISelLowering.cpp
   AVRRegisterInfo.cpp
   AVRSubtarget.cpp
   AVRTargetMachine.cpp
   AVRTargetObjectFile.cpp
 )
 
 add_dependencies(LLVMAVRCodeGen intrinsics_gen)
 
 add_subdirectory(MCTargetDesc)
 add_subdirectory(TargetInfo)
 add_subdirectory(AsmParser)