//===-- Mos6502InstrInfo.cpp - Mos6502 Instruction Information ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the Mos6502 implementation of the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//

#include "Mos6502InstrInfo.h"
#include "Mos6502.h"
#include "Mos6502MachineFunctionInfo.h"
#include "Mos6502Subtarget.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TargetRegistry.h"

using namespace llvm;

#define GET_INSTRINFO_CTOR_DTOR
#include "Mos6502GenInstrInfo.inc"

// Pin the vtable to this file.
void Mos6502InstrInfo::anchor() {}

Mos6502InstrInfo::Mos6502InstrInfo(Mos6502Subtarget &ST)
    : Mos6502GenInstrInfo(M6502::ADJCALLSTACKDOWN, M6502::ADJCALLSTACKUP), RI(),
      Subtarget(ST) {}

/// isLoadFromStackSlot - If the specified machine instruction is a direct
/// load from a stack slot, return the virtual or physical register number of
/// the destination along with the FrameIndex of the loaded stack slot.  If
/// not, return 0.  This predicate must return 0 if the instruction has
/// any side effects other than loading from the stack slot.
unsigned Mos6502InstrInfo::isLoadFromStackSlot(const MachineInstr *MI,
                                             int &FrameIndex) const {
  if (MI->getOpcode() == M6502::LDri ||
      MI->getOpcode() == M6502::LDXri ||
      MI->getOpcode() == M6502::LDFri ||
      MI->getOpcode() == M6502::LDDFri ||
      MI->getOpcode() == M6502::LDQFri) {
    if (MI->getOperand(1).isFI() && MI->getOperand(2).isImm() &&
        MI->getOperand(2).getImm() == 0) {
      FrameIndex = MI->getOperand(1).getIndex();
      return MI->getOperand(0).getReg();
    }
  }
  return 0;
}

/// isStoreToStackSlot - If the specified machine instruction is a direct
/// store to a stack slot, return the virtual or physical register number of
/// the source reg along with the FrameIndex of the loaded stack slot.  If
/// not, return 0.  This predicate must return 0 if the instruction has
/// any side effects other than storing to the stack slot.
unsigned Mos6502InstrInfo::isStoreToStackSlot(const MachineInstr *MI,
                                            int &FrameIndex) const {
  if (MI->getOpcode() == M6502::STri ||
      MI->getOpcode() == M6502::STXri ||
      MI->getOpcode() == M6502::STFri ||
      MI->getOpcode() == M6502::STDFri ||
      MI->getOpcode() == M6502::STQFri) {
    if (MI->getOperand(0).isFI() && MI->getOperand(1).isImm() &&
        MI->getOperand(1).getImm() == 0) {
      FrameIndex = MI->getOperand(0).getIndex();
      return MI->getOperand(2).getReg();
    }
  }
  return 0;
}

static bool IsIntegerCC(unsigned CC)
{
  return  (CC <= SPCC::ICC_VC);
}


static SPCC::CondCodes GetOppositeBranchCondition(SPCC::CondCodes CC)
{
  switch(CC) {
  case SPCC::ICC_A:    return SPCC::ICC_N;
  case SPCC::ICC_N:    return SPCC::ICC_A;
  case SPCC::ICC_NE:   return SPCC::ICC_E;
  case SPCC::ICC_E:    return SPCC::ICC_NE;
  case SPCC::ICC_G:    return SPCC::ICC_LE;
  case SPCC::ICC_LE:   return SPCC::ICC_G;
  case SPCC::ICC_GE:   return SPCC::ICC_L;
  case SPCC::ICC_L:    return SPCC::ICC_GE;
  case SPCC::ICC_GU:   return SPCC::ICC_LEU;
  case SPCC::ICC_LEU:  return SPCC::ICC_GU;
  case SPCC::ICC_CC:   return SPCC::ICC_CS;
  case SPCC::ICC_CS:   return SPCC::ICC_CC;
  case SPCC::ICC_POS:  return SPCC::ICC_NEG;
  case SPCC::ICC_NEG:  return SPCC::ICC_POS;
  case SPCC::ICC_VC:   return SPCC::ICC_VS;
  case SPCC::ICC_VS:   return SPCC::ICC_VC;

  case SPCC::FCC_A:    return SPCC::FCC_N;
  case SPCC::FCC_N:    return SPCC::FCC_A;
  case SPCC::FCC_U:    return SPCC::FCC_O;
  case SPCC::FCC_O:    return SPCC::FCC_U;
  case SPCC::FCC_G:    return SPCC::FCC_ULE;
  case SPCC::FCC_LE:   return SPCC::FCC_UG;
  case SPCC::FCC_UG:   return SPCC::FCC_LE;
  case SPCC::FCC_ULE:  return SPCC::FCC_G;
  case SPCC::FCC_L:    return SPCC::FCC_UGE;
  case SPCC::FCC_GE:   return SPCC::FCC_UL;
  case SPCC::FCC_UL:   return SPCC::FCC_GE;
  case SPCC::FCC_UGE:  return SPCC::FCC_L;
  case SPCC::FCC_LG:   return SPCC::FCC_UE;
  case SPCC::FCC_UE:   return SPCC::FCC_LG;
  case SPCC::FCC_NE:   return SPCC::FCC_E;
  case SPCC::FCC_E:    return SPCC::FCC_NE;
  }
  llvm_unreachable("Invalid cond code");
}

bool Mos6502InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
                                   MachineBasicBlock *&TBB,
                                   MachineBasicBlock *&FBB,
                                   SmallVectorImpl<MachineOperand> &Cond,
                                   bool AllowModify) const
{

  MachineBasicBlock::iterator I = MBB.end();
  MachineBasicBlock::iterator UnCondBrIter = MBB.end();
  while (I != MBB.begin()) {
    --I;

    if (I->isDebugValue())
      continue;

    // When we see a non-terminator, we are done.
    if (!isUnpredicatedTerminator(I))
      break;

    // Terminator is not a branch.
    if (!I->isBranch())
      return true;

    // Handle Unconditional branches.
    if (I->getOpcode() == M6502::BA) {
      UnCondBrIter = I;

      if (!AllowModify) {
        TBB = I->getOperand(0).getMBB();
        continue;
      }

      while (std::next(I) != MBB.end())
        std::next(I)->eraseFromParent();

      Cond.clear();
      FBB = nullptr;

      if (MBB.isLayoutSuccessor(I->getOperand(0).getMBB())) {
        TBB = nullptr;
        I->eraseFromParent();
        I = MBB.end();
        UnCondBrIter = MBB.end();
        continue;
      }

      TBB = I->getOperand(0).getMBB();
      continue;
    }

    unsigned Opcode = I->getOpcode();
    if (Opcode != M6502::BCOND && Opcode != M6502::FBCOND)
      return true; // Unknown Opcode.

    SPCC::CondCodes BranchCode = (SPCC::CondCodes)I->getOperand(1).getImm();

    if (Cond.empty()) {
      MachineBasicBlock *TargetBB = I->getOperand(0).getMBB();
      if (AllowModify && UnCondBrIter != MBB.end() &&
          MBB.isLayoutSuccessor(TargetBB)) {

        // Transform the code
        //
        //    brCC L1
        //    ba L2
        // L1:
        //    ..
        // L2:
        //
        // into
        //
        //   brnCC L2
        // L1:
        //   ...
        // L2:
        //
        BranchCode = GetOppositeBranchCondition(BranchCode);
        MachineBasicBlock::iterator OldInst = I;
        BuildMI(MBB, UnCondBrIter, MBB.findDebugLoc(I), get(Opcode))
          .addMBB(UnCondBrIter->getOperand(0).getMBB()).addImm(BranchCode);
        BuildMI(MBB, UnCondBrIter, MBB.findDebugLoc(I), get(M6502::BA))
          .addMBB(TargetBB);

        OldInst->eraseFromParent();
        UnCondBrIter->eraseFromParent();

        UnCondBrIter = MBB.end();
        I = MBB.end();
        continue;
      }
      FBB = TBB;
      TBB = I->getOperand(0).getMBB();
      Cond.push_back(MachineOperand::CreateImm(BranchCode));
      continue;
    }
    // FIXME: Handle subsequent conditional branches.
    // For now, we can't handle multiple conditional branches.
    return true;
  }
  return false;
}

unsigned
Mos6502InstrInfo::InsertBranch(MachineBasicBlock &MBB,MachineBasicBlock *TBB,
                             MachineBasicBlock *FBB,
                             ArrayRef<MachineOperand> Cond,
                             DebugLoc DL) const {
  assert(TBB && "InsertBranch must not be told to insert a fallthrough");
  assert((Cond.size() == 1 || Cond.size() == 0) &&
         "Mos6502 branch conditions should have one component!");

  if (Cond.empty()) {
    assert(!FBB && "Unconditional branch with multiple successors!");
    BuildMI(&MBB, DL, get(M6502::BA)).addMBB(TBB);
    return 1;
  }

  // Conditional branch
  unsigned CC = Cond[0].getImm();

  if (IsIntegerCC(CC))
    BuildMI(&MBB, DL, get(M6502::BCOND)).addMBB(TBB).addImm(CC);
  else
    BuildMI(&MBB, DL, get(M6502::FBCOND)).addMBB(TBB).addImm(CC);
  if (!FBB)
    return 1;

  BuildMI(&MBB, DL, get(M6502::BA)).addMBB(FBB);
  return 2;
}

unsigned Mos6502InstrInfo::RemoveBranch(MachineBasicBlock &MBB) const
{
  MachineBasicBlock::iterator I = MBB.end();
  unsigned Count = 0;
  while (I != MBB.begin()) {
    --I;

    if (I->isDebugValue())
      continue;

    if (I->getOpcode() != M6502::BA
        && I->getOpcode() != M6502::BCOND
        && I->getOpcode() != M6502::FBCOND)
      break; // Not a branch

    I->eraseFromParent();
    I = MBB.end();
    ++Count;
  }
  return Count;
}

void Mos6502InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
                                 MachineBasicBlock::iterator I, DebugLoc DL,
                                 unsigned DestReg, unsigned SrcReg,
                                 bool KillSrc) const {
  unsigned numSubRegs = 0;
  unsigned movOpc     = 0;
  const unsigned *subRegIdx = nullptr;

  const unsigned DFP_FP_SubRegsIdx[]  = { M6502::sub_even, M6502::sub_odd };
  const unsigned QFP_DFP_SubRegsIdx[] = { M6502::sub_even64, M6502::sub_odd64 };
  const unsigned QFP_FP_SubRegsIdx[]  = { M6502::sub_even, M6502::sub_odd,
                                          M6502::sub_odd64_then_sub_even,
                                          M6502::sub_odd64_then_sub_odd };

  if (M6502::IntRegsRegClass.contains(DestReg, SrcReg))
    BuildMI(MBB, I, DL, get(M6502::ORrr), DestReg).addReg(M6502::G0)
      .addReg(SrcReg, getKillRegState(KillSrc));
  else if (M6502::FPRegsRegClass.contains(DestReg, SrcReg))
    BuildMI(MBB, I, DL, get(M6502::FMOVS), DestReg)
      .addReg(SrcReg, getKillRegState(KillSrc));
  else if (M6502::DFPRegsRegClass.contains(DestReg, SrcReg)) {
    if (Subtarget.isV9()) {
      BuildMI(MBB, I, DL, get(M6502::FMOVD), DestReg)
        .addReg(SrcReg, getKillRegState(KillSrc));
    } else {
      // Use two FMOVS instructions.
      subRegIdx  = DFP_FP_SubRegsIdx;
      numSubRegs = 2;
      movOpc     = M6502::FMOVS;
    }
  } else if (M6502::QFPRegsRegClass.contains(DestReg, SrcReg)) {
    if (Subtarget.isV9()) {
      if (Subtarget.hasHardQuad()) {
        BuildMI(MBB, I, DL, get(M6502::FMOVQ), DestReg)
          .addReg(SrcReg, getKillRegState(KillSrc));
      } else {
        // Use two FMOVD instructions.
        subRegIdx  = QFP_DFP_SubRegsIdx;
        numSubRegs = 2;
        movOpc     = M6502::FMOVD;
      }
    } else {
      // Use four FMOVS instructions.
      subRegIdx  = QFP_FP_SubRegsIdx;
      numSubRegs = 4;
      movOpc     = M6502::FMOVS;
    }
  } else if (M6502::ASRRegsRegClass.contains(DestReg) &&
             M6502::IntRegsRegClass.contains(SrcReg)) {
    BuildMI(MBB, I, DL, get(M6502::WRASRrr), DestReg)
        .addReg(M6502::G0)
        .addReg(SrcReg, getKillRegState(KillSrc));
  } else if (M6502::IntRegsRegClass.contains(DestReg) &&
             M6502::ASRRegsRegClass.contains(SrcReg)) {
    BuildMI(MBB, I, DL, get(M6502::RDASR), DestReg)
        .addReg(SrcReg, getKillRegState(KillSrc));
  } else
    llvm_unreachable("Impossible reg-to-reg copy");

  if (numSubRegs == 0 || subRegIdx == nullptr || movOpc == 0)
    return;

  const TargetRegisterInfo *TRI = &getRegisterInfo();
  MachineInstr *MovMI = nullptr;

  for (unsigned i = 0; i != numSubRegs; ++i) {
    unsigned Dst = TRI->getSubReg(DestReg, subRegIdx[i]);
    unsigned Src = TRI->getSubReg(SrcReg,  subRegIdx[i]);
    assert(Dst && Src && "Bad sub-register");

    MovMI = BuildMI(MBB, I, DL, get(movOpc), Dst).addReg(Src);
  }
  // Add implicit super-register defs and kills to the last MovMI.
  MovMI->addRegisterDefined(DestReg, TRI);
  if (KillSrc)
    MovMI->addRegisterKilled(SrcReg, TRI);
}

void Mos6502InstrInfo::
storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
                    unsigned SrcReg, bool isKill, int FI,
                    const TargetRegisterClass *RC,
                    const TargetRegisterInfo *TRI) const {
  DebugLoc DL;
  if (I != MBB.end()) DL = I->getDebugLoc();

  MachineFunction *MF = MBB.getParent();
  const MachineFrameInfo &MFI = *MF->getFrameInfo();
  MachineMemOperand *MMO =
    MF->getMachineMemOperand(MachinePointerInfo::getFixedStack(FI),
                             MachineMemOperand::MOStore,
                             MFI.getObjectSize(FI),
                             MFI.getObjectAlignment(FI));

  // On the order of operands here: think "[FrameIdx + 0] = SrcReg".
 if (RC == &M6502::I64RegsRegClass)
    BuildMI(MBB, I, DL, get(M6502::STXri)).addFrameIndex(FI).addImm(0)
      .addReg(SrcReg, getKillRegState(isKill)).addMemOperand(MMO);
  else if (RC == &M6502::IntRegsRegClass)
    BuildMI(MBB, I, DL, get(M6502::STri)).addFrameIndex(FI).addImm(0)
      .addReg(SrcReg, getKillRegState(isKill)).addMemOperand(MMO);
  else if (RC == &M6502::FPRegsRegClass)
    BuildMI(MBB, I, DL, get(M6502::STFri)).addFrameIndex(FI).addImm(0)
      .addReg(SrcReg,  getKillRegState(isKill)).addMemOperand(MMO);
  else if (M6502::DFPRegsRegClass.hasSubClassEq(RC))
    BuildMI(MBB, I, DL, get(M6502::STDFri)).addFrameIndex(FI).addImm(0)
      .addReg(SrcReg,  getKillRegState(isKill)).addMemOperand(MMO);
  else if (M6502::QFPRegsRegClass.hasSubClassEq(RC))
    // Use STQFri irrespective of its legality. If STQ is not legal, it will be
    // lowered into two STDs in eliminateFrameIndex.
    BuildMI(MBB, I, DL, get(M6502::STQFri)).addFrameIndex(FI).addImm(0)
      .addReg(SrcReg,  getKillRegState(isKill)).addMemOperand(MMO);
  else
    llvm_unreachable("Can't store this register to stack slot");
}

void Mos6502InstrInfo::
loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
                     unsigned DestReg, int FI,
                     const TargetRegisterClass *RC,
                     const TargetRegisterInfo *TRI) const {
  DebugLoc DL;
  if (I != MBB.end()) DL = I->getDebugLoc();

  MachineFunction *MF = MBB.getParent();
  const MachineFrameInfo &MFI = *MF->getFrameInfo();
  MachineMemOperand *MMO =
    MF->getMachineMemOperand(MachinePointerInfo::getFixedStack(FI),
                             MachineMemOperand::MOLoad,
                             MFI.getObjectSize(FI),
                             MFI.getObjectAlignment(FI));

  if (RC == &M6502::I64RegsRegClass)
    BuildMI(MBB, I, DL, get(M6502::LDXri), DestReg).addFrameIndex(FI).addImm(0)
      .addMemOperand(MMO);
  else if (RC == &M6502::IntRegsRegClass)
    BuildMI(MBB, I, DL, get(M6502::LDri), DestReg).addFrameIndex(FI).addImm(0)
      .addMemOperand(MMO);
  else if (RC == &M6502::FPRegsRegClass)
    BuildMI(MBB, I, DL, get(M6502::LDFri), DestReg).addFrameIndex(FI).addImm(0)
      .addMemOperand(MMO);
  else if (M6502::DFPRegsRegClass.hasSubClassEq(RC))
    BuildMI(MBB, I, DL, get(M6502::LDDFri), DestReg).addFrameIndex(FI).addImm(0)
      .addMemOperand(MMO);
  else if (M6502::QFPRegsRegClass.hasSubClassEq(RC))
    // Use LDQFri irrespective of its legality. If LDQ is not legal, it will be
    // lowered into two LDDs in eliminateFrameIndex.
    BuildMI(MBB, I, DL, get(M6502::LDQFri), DestReg).addFrameIndex(FI).addImm(0)
      .addMemOperand(MMO);
  else
    llvm_unreachable("Can't load this register from stack slot");
}

unsigned Mos6502InstrInfo::getGlobalBaseReg(MachineFunction *MF) const
{
  Mos6502MachineFunctionInfo *Mos6502FI = MF->getInfo<Mos6502MachineFunctionInfo>();
  unsigned GlobalBaseReg = Mos6502FI->getGlobalBaseReg();
  if (GlobalBaseReg != 0)
    return GlobalBaseReg;

  // Insert the set of GlobalBaseReg into the first MBB of the function
  MachineBasicBlock &FirstMBB = MF->front();
  MachineBasicBlock::iterator MBBI = FirstMBB.begin();
  MachineRegisterInfo &RegInfo = MF->getRegInfo();

  const TargetRegisterClass *PtrRC =
    Subtarget.is64Bit() ? &M6502::I64RegsRegClass : &M6502::IntRegsRegClass;
  GlobalBaseReg = RegInfo.createVirtualRegister(PtrRC);

  DebugLoc dl;

  BuildMI(FirstMBB, MBBI, dl, get(M6502::GETPCX), GlobalBaseReg);
  Mos6502FI->setGlobalBaseReg(GlobalBaseReg);
  return GlobalBaseReg;
}