//===-- Mips16ISelDAGToDAG.cpp - A Dag to Dag Inst Selector for Mips16 ----===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Subclass of MipsDAGToDAGISel specialized for mips16.
//
//===----------------------------------------------------------------------===//

#include "Mips16ISelDAGToDAG.h"
#include "MCTargetDesc/MipsBaseInfo.h"
#include "Mips.h"
#include "MipsAnalyzeImmediate.h"
#include "MipsMachineFunction.h"
#include "MipsRegisterInfo.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;

#define DEBUG_TYPE "mips-isel"

bool Mips16DAGToDAGISel::runOnMachineFunction(MachineFunction &MF) {
  Subtarget = &static_cast<const MipsSubtarget &>(MF.getSubtarget());
  if (!Subtarget->inMips16Mode())
    return false;
  return MipsDAGToDAGISel::runOnMachineFunction(MF);
}
/// Select multiply instructions.
std::pair<SDNode*, SDNode*>
Mips16DAGToDAGISel::selectMULT(SDNode *N, unsigned Opc, SDLoc DL, EVT Ty,
                               bool HasLo, bool HasHi) {
  SDNode *Lo = nullptr, *Hi = nullptr;
  SDNode *Mul = CurDAG->getMachineNode(Opc, DL, MVT::Glue, N->getOperand(0),
                                       N->getOperand(1));
  SDValue InFlag = SDValue(Mul, 0);

  if (HasLo) {
    unsigned Opcode = Mips::Mflo16;
    Lo = CurDAG->getMachineNode(Opcode, DL, Ty, MVT::Glue, InFlag);
    InFlag = SDValue(Lo, 1);
  }
  if (HasHi) {
    unsigned Opcode = Mips::Mfhi16;
    Hi = CurDAG->getMachineNode(Opcode, DL, Ty, InFlag);
  }
  return std::make_pair(Lo, Hi);
}

void Mips16DAGToDAGISel::initGlobalBaseReg(MachineFunction &MF) {
  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();

  if (!MipsFI->globalBaseRegSet())
    return;

  MachineBasicBlock &MBB = MF.front();
  MachineBasicBlock::iterator I = MBB.begin();
  MachineRegisterInfo &RegInfo = MF.getRegInfo();
  const TargetInstrInfo &TII = *Subtarget->getInstrInfo();
  DebugLoc DL;
  unsigned V0, V1, V2, GlobalBaseReg = MipsFI->getGlobalBaseReg();
  const TargetRegisterClass *RC = &Mips::CPU16RegsRegClass;

  V0 = RegInfo.createVirtualRegister(RC);
  V1 = RegInfo.createVirtualRegister(RC);
  V2 = RegInfo.createVirtualRegister(RC);

  BuildMI(MBB, I, DL, TII.get(Mips::GotPrologue16), V0).
    addReg(V1, RegState::Define).
    addExternalSymbol("_gp_disp", MipsII::MO_ABS_HI).
    addExternalSymbol("_gp_disp", MipsII::MO_ABS_LO);

  BuildMI(MBB, I, DL, TII.get(Mips::SllX16), V2).addReg(V0).addImm(16);
  BuildMI(MBB, I, DL, TII.get(Mips::AdduRxRyRz16), GlobalBaseReg)
    .addReg(V1).addReg(V2);
}

// Insert instructions to initialize the Mips16 SP Alias register in the
// first MBB of the function.
//
void Mips16DAGToDAGISel::initMips16SPAliasReg(MachineFunction &MF) {
  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();

  if (!MipsFI->mips16SPAliasRegSet())
    return;

  MachineBasicBlock &MBB = MF.front();
  MachineBasicBlock::iterator I = MBB.begin();
  const TargetInstrInfo &TII = *Subtarget->getInstrInfo();
  DebugLoc DL = I != MBB.end() ? I->getDebugLoc() : DebugLoc();
  unsigned Mips16SPAliasReg = MipsFI->getMips16SPAliasReg();

  BuildMI(MBB, I, DL, TII.get(Mips::MoveR3216), Mips16SPAliasReg)
    .addReg(Mips::SP);
}

void Mips16DAGToDAGISel::processFunctionAfterISel(MachineFunction &MF) {
  initGlobalBaseReg(MF);
  initMips16SPAliasReg(MF);
}

/// getMips16SPAliasReg - Output the instructions required to put the
/// SP into a Mips16 accessible aliased register.
SDValue Mips16DAGToDAGISel::getMips16SPAliasReg() {
  unsigned Mips16SPAliasReg =
    MF->getInfo<MipsFunctionInfo>()->getMips16SPAliasReg();
  auto PtrVT = getTargetLowering()->getPointerTy(CurDAG->getDataLayout());
  return CurDAG->getRegister(Mips16SPAliasReg, PtrVT);
}

void Mips16DAGToDAGISel::getMips16SPRefReg(SDNode *Parent, SDValue &AliasReg) {
  auto PtrVT = getTargetLowering()->getPointerTy(CurDAG->getDataLayout());
  SDValue AliasFPReg = CurDAG->getRegister(Mips::S0, PtrVT);
  if (Parent) {
    switch (Parent->getOpcode()) {
      case ISD::LOAD: {
        LoadSDNode *SD = dyn_cast<LoadSDNode>(Parent);
        switch (SD->getMemoryVT().getSizeInBits()) {
        case 8:
        case 16:
          AliasReg = Subtarget->getFrameLowering()->hasFP(*MF)
                         ? AliasFPReg
                         : getMips16SPAliasReg();
          return;
        }
        break;
      }
      case ISD::STORE: {
        StoreSDNode *SD = dyn_cast<StoreSDNode>(Parent);
        switch (SD->getMemoryVT().getSizeInBits()) {
        case 8:
        case 16:
          AliasReg = Subtarget->getFrameLowering()->hasFP(*MF)
                         ? AliasFPReg
                         : getMips16SPAliasReg();
          return;
        }
        break;
      }
    }
  }
  AliasReg = CurDAG->getRegister(Mips::SP, PtrVT);
  return;

}

bool Mips16DAGToDAGISel::selectAddr16(
  SDNode *Parent, SDValue Addr, SDValue &Base, SDValue &Offset,
  SDValue &Alias) {
  SDLoc DL(Addr);
  EVT ValTy = Addr.getValueType();

  Alias = CurDAG->getTargetConstant(0, DL, ValTy);

  // if Address is FI, get the TargetFrameIndex.
  if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
    Base   = CurDAG->getTargetFrameIndex(FIN->getIndex(), ValTy);
    Offset = CurDAG->getTargetConstant(0, DL, ValTy);
    getMips16SPRefReg(Parent, Alias);
    return true;
  }
  // on PIC code Load GA
  if (Addr.getOpcode() == MipsISD::Wrapper) {
    Base   = Addr.getOperand(0);
    Offset = Addr.getOperand(1);
    return true;
  }
  if (TM.getRelocationModel() != Reloc::PIC_) {
    if ((Addr.getOpcode() == ISD::TargetExternalSymbol ||
        Addr.getOpcode() == ISD::TargetGlobalAddress))
      return false;
  }
  // Addresses of the form FI+const or FI|const
  if (CurDAG->isBaseWithConstantOffset(Addr)) {
    ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1));
    if (isInt<16>(CN->getSExtValue())) {

      // If the first operand is a FI, get the TargetFI Node
      if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>
                                  (Addr.getOperand(0))) {
        Base = CurDAG->getTargetFrameIndex(FIN->getIndex(), ValTy);
        getMips16SPRefReg(Parent, Alias);
      }
      else
        Base = Addr.getOperand(0);

      Offset = CurDAG->getTargetConstant(CN->getZExtValue(), DL, ValTy);
      return true;
    }
  }
  // Operand is a result from an ADD.
  if (Addr.getOpcode() == ISD::ADD) {
    // When loading from constant pools, load the lower address part in
    // the instruction itself. Example, instead of:
    //  lui $2, %hi($CPI1_0)
    //  addiu $2, $2, %lo($CPI1_0)
    //  lwc1 $f0, 0($2)
    // Generate:
    //  lui $2, %hi($CPI1_0)
    //  lwc1 $f0, %lo($CPI1_0)($2)
    if (Addr.getOperand(1).getOpcode() == MipsISD::Lo ||
        Addr.getOperand(1).getOpcode() == MipsISD::GPRel) {
      SDValue Opnd0 = Addr.getOperand(1).getOperand(0);
      if (isa<ConstantPoolSDNode>(Opnd0) || isa<GlobalAddressSDNode>(Opnd0) ||
          isa<JumpTableSDNode>(Opnd0)) {
        Base = Addr.getOperand(0);
        Offset = Opnd0;
        return true;
      }
    }

    // If an indexed floating point load/store can be emitted, return false.
    const LSBaseSDNode *LS = dyn_cast<LSBaseSDNode>(Parent);

    if (LS) {
      if (LS->getMemoryVT() == MVT::f32 && Subtarget->hasMips4_32r2())
        return false;
      if (LS->getMemoryVT() == MVT::f64 && Subtarget->hasMips4_32r2())
        return false;
    }
  }
  Base   = Addr;
  Offset = CurDAG->getTargetConstant(0, DL, ValTy);
  return true;
}

/// Select instructions not customized! Used for
/// expanded, promoted and normal instructions
std::pair<bool, SDNode*> Mips16DAGToDAGISel::selectNode(SDNode *Node) {
  unsigned Opcode = Node->getOpcode();
  SDLoc DL(Node);

  ///
  // Instruction Selection not handled by the auto-generated
  // tablegen selection should be handled here.
  ///
  EVT NodeTy = Node->getValueType(0);
  unsigned MultOpc;

  switch(Opcode) {
  default: break;

  case ISD::SUBE:
  case ISD::ADDE: {
    SDValue InFlag = Node->getOperand(2), CmpLHS;
    unsigned Opc = InFlag.getOpcode(); (void)Opc;
    assert(((Opc == ISD::ADDC || Opc == ISD::ADDE) ||
            (Opc == ISD::SUBC || Opc == ISD::SUBE)) &&
           "(ADD|SUB)E flag operand must come from (ADD|SUB)C/E insn");

    unsigned MOp;
    if (Opcode == ISD::ADDE) {
      CmpLHS = InFlag.getValue(0);
      MOp = Mips::AdduRxRyRz16;
    } else {
      CmpLHS = InFlag.getOperand(0);
      MOp = Mips::SubuRxRyRz16;
    }

    SDValue Ops[] = { CmpLHS, InFlag.getOperand(1) };

    SDValue LHS = Node->getOperand(0);
    SDValue RHS = Node->getOperand(1);

    EVT VT = LHS.getValueType();

    unsigned Sltu_op = Mips::SltuRxRyRz16;
    SDNode *Carry = CurDAG->getMachineNode(Sltu_op, DL, VT, Ops);
    unsigned Addu_op = Mips::AdduRxRyRz16;
    SDNode *AddCarry = CurDAG->getMachineNode(Addu_op, DL, VT,
                                              SDValue(Carry,0), RHS);

    SDNode *Result = CurDAG->SelectNodeTo(Node, MOp, VT, MVT::Glue, LHS,
                                          SDValue(AddCarry,0));
    return std::make_pair(true, Result);
  }

  /// Mul with two results
  case ISD::SMUL_LOHI:
  case ISD::UMUL_LOHI: {
    MultOpc = (Opcode == ISD::UMUL_LOHI ? Mips::MultuRxRy16 : Mips::MultRxRy16);
    std::pair<SDNode*, SDNode*> LoHi = selectMULT(Node, MultOpc, DL, NodeTy,
                                                  true, true);
    if (!SDValue(Node, 0).use_empty())
      ReplaceUses(SDValue(Node, 0), SDValue(LoHi.first, 0));

    if (!SDValue(Node, 1).use_empty())
      ReplaceUses(SDValue(Node, 1), SDValue(LoHi.second, 0));

    return std::make_pair(true, nullptr);
  }

  case ISD::MULHS:
  case ISD::MULHU: {
    MultOpc = (Opcode == ISD::MULHU ? Mips::MultuRxRy16 : Mips::MultRxRy16);
    SDNode *Result = selectMULT(Node, MultOpc, DL, NodeTy, false, true).second;
    return std::make_pair(true, Result);
  }
  }

  return std::make_pair(false, nullptr);
}

FunctionPass *llvm::createMips16ISelDag(MipsTargetMachine &TM) {
  return new Mips16DAGToDAGISel(TM);
}