//===-- MBlazeMCCodeEmitter.cpp - Convert MBlaze code to machine code -----===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the MBlazeMCCodeEmitter class.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "mccodeemitter"
#include "MBlaze.h"
#include "MBlazeInstrInfo.h"
#include "MBlazeFixupKinds.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

STATISTIC(MCNumEmitted, "Number of MC instructions emitted");

namespace {
class MBlazeMCCodeEmitter : public MCCodeEmitter {
  MBlazeMCCodeEmitter(const MBlazeMCCodeEmitter &); // DO NOT IMPLEMENT
  void operator=(const MBlazeMCCodeEmitter &); // DO NOT IMPLEMENT
  const TargetMachine &TM;
  const TargetInstrInfo &TII;
  MCContext &Ctx;

public:
  MBlazeMCCodeEmitter(TargetMachine &tm, MCContext &ctx)
    : TM(tm), TII(*TM.getInstrInfo()), Ctx(ctx) {
  }

  ~MBlazeMCCodeEmitter() {}

  // getBinaryCodeForInstr - TableGen'erated function for getting the
  // binary encoding for an instruction.
  unsigned getBinaryCodeForInstr(const MCInst &MI) const;

  /// getMachineOpValue - Return binary encoding of operand. If the machine
  /// operand requires relocation, record the relocation and return zero.
  unsigned getMachineOpValue(const MCInst &MI,const MCOperand &MO) const;
  unsigned getMachineOpValue(const MCInst &MI, unsigned OpIdx) const {
    return getMachineOpValue(MI, MI.getOperand(OpIdx));
  }

  unsigned getNumFixupKinds() const {
    return 2;
  }

  const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const {
    const static MCFixupKindInfo Infos[] = {
      { "reloc_pcrel_4byte", 0, 4 * 8, MCFixupKindInfo::FKF_IsPCRel },
      { "reloc_pcrel_2byte", 0, 2 * 8, MCFixupKindInfo::FKF_IsPCRel } };

    if (Kind < FirstTargetFixupKind)
      return MCCodeEmitter::getFixupKindInfo(Kind);

    if (unsigned(Kind-FirstTargetFixupKind) < getNumFixupKinds())
      return Infos[Kind - FirstTargetFixupKind];

    assert(0 && "Invalid fixup kind.");
    return Infos[0];
  }

  static unsigned GetMBlazeRegNum(const MCOperand &MO) {
    // FIXME: getMBlazeRegisterNumbering() is sufficient?
    assert(0 && "MBlazeMCCodeEmitter::GetMBlazeRegNum() not yet implemented.");
    return 0;
  }

  void EmitByte(unsigned char C, unsigned &CurByte, raw_ostream &OS) const {
    // The MicroBlaze uses a bit reversed format so we need to reverse the
    // order of the bits. Taken from:
    // http://graphics.stanford.edu/~seander/bithacks.html
    C = ((C * 0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32;

    OS << (char)C;
    ++CurByte;
  }

  void EmitRawByte(unsigned char C, unsigned &CurByte, raw_ostream &OS) const {
    OS << (char)C;
    ++CurByte;
  }

  void EmitConstant(uint64_t Val, unsigned Size, unsigned &CurByte,
                    raw_ostream &OS) const {
    assert(Size <= 8 && "size too big in emit constant");

    for (unsigned i = 0; i != Size; ++i) {
      EmitByte(Val & 255, CurByte, OS);
      Val >>= 8;
    }
  }

  void EmitIMM(const MCOperand &imm, unsigned &CurByte, raw_ostream &OS) const;
  void EmitIMM(const MCInst &MI, unsigned op, unsigned &CurByte,
               raw_ostream &OS) const;

  void EmitImmediate(const MCInst &MI,
                     unsigned opNo, MCFixupKind FixupKind,
                     unsigned &CurByte, raw_ostream &OS,
                     SmallVectorImpl<MCFixup> &Fixups) const;

  void EncodeInstruction(const MCInst &MI, raw_ostream &OS,
                         SmallVectorImpl<MCFixup> &Fixups) const;
};

} // end anonymous namespace


MCCodeEmitter *llvm::createMBlazeMCCodeEmitter(const Target &,
                                               TargetMachine &TM,
                                               MCContext &Ctx) {
  return new MBlazeMCCodeEmitter(TM, Ctx);
}

/// getMachineOpValue - Return binary encoding of operand. If the machine
/// operand requires relocation, record the relocation and return zero.
unsigned MBlazeMCCodeEmitter::getMachineOpValue(const MCInst &MI,
                                             const MCOperand &MO) const {
  if (MO.isReg())
    return MBlazeRegisterInfo::getRegisterNumbering(MO.getReg());
  else if (MO.isImm())
    return static_cast<unsigned>(MO.getImm());
  else if (MO.isExpr())
      return 0; // The relocation has already been recorded at this point.
  else {
#ifndef NDEBUG
    errs() << MO;
#endif
    llvm_unreachable(0);
  }
  return 0;
}

void MBlazeMCCodeEmitter::
EmitIMM(const MCOperand &imm, unsigned &CurByte, raw_ostream &OS) const {
  int32_t val = (int32_t)imm.getImm();
  if (val > 32767 || val < -32768) {
    EmitByte(0x0D, CurByte, OS);
    EmitByte(0x00, CurByte, OS);
    EmitRawByte((val >> 24) & 0xFF, CurByte, OS);
    EmitRawByte((val >> 16) & 0xFF, CurByte, OS);
  }
}

void MBlazeMCCodeEmitter::
EmitIMM(const MCInst &MI, unsigned op, unsigned &CurByte,
        raw_ostream &OS) const {
    MCOperand mcop = MI.getOperand(op);
    if (mcop.isExpr()) {
        EmitByte(0x0D, CurByte, OS);
        EmitByte(0x00, CurByte, OS);
        EmitRawByte(0, CurByte, OS);
        EmitRawByte(0, CurByte, OS);
    }
}

void MBlazeMCCodeEmitter::
EmitImmediate(const MCInst &MI, unsigned opNo, MCFixupKind FixupKind,
              unsigned &CurByte, raw_ostream &OS,
              SmallVectorImpl<MCFixup> &Fixups) const {
  assert(MI.getNumOperands()>opNo && "Not enought operands for instruction");

  MCOperand oper = MI.getOperand(opNo);
  if (oper.isImm()) {
      EmitIMM(oper, CurByte, OS);
  } else if (oper.isExpr()) {
      Fixups.push_back(MCFixup::Create(0,oper.getExpr(),FixupKind));
  }
}



void MBlazeMCCodeEmitter::
EncodeInstruction(const MCInst &MI, raw_ostream &OS,
                  SmallVectorImpl<MCFixup> &Fixups) const {
  unsigned Opcode = MI.getOpcode();
  const TargetInstrDesc &Desc = TII.get(Opcode);
  uint64_t TSFlags = Desc.TSFlags;
  // Keep track of the current byte being emitted.
  unsigned CurByte = 0;

  switch ((TSFlags & MBlazeII::FormMask)) {
  default: break;
  case MBlazeII::FPseudo:
    // Pseudo instructions don't get encoded.
    return;

  case MBlazeII::FRRI:
    EmitImmediate(MI, 2, FK_Data_4, CurByte, OS, Fixups);
    break;

  case MBlazeII::FRIR:
    EmitImmediate(MI, 1, FK_Data_4, CurByte, OS, Fixups);
    break;

  case MBlazeII::FCRI:
    EmitImmediate(MI, 1, MCFixupKind(MBlaze::reloc_pcrel_2byte), CurByte, OS,
                  Fixups);
    break;

  case MBlazeII::FRCI:
    EmitImmediate(MI, 1, MCFixupKind(MBlaze::reloc_pcrel_4byte), CurByte, OS,
                  Fixups);

  case MBlazeII::FCCI:
    EmitImmediate(MI, 0, MCFixupKind(MBlaze::reloc_pcrel_4byte), CurByte, OS,
                  Fixups);
    break;
  }

  ++MCNumEmitted;  // Keep track of the # of mi's emitted
  unsigned Value = getBinaryCodeForInstr(MI);
  switch (Opcode) {
  default:
    EmitConstant(Value, 4, CurByte, OS);
    break;

  case MBlaze::BRLID:
  case MBlaze::BRALID:
    EmitIMM(MI,1,CurByte,OS);
    EmitConstant(Value, 4, CurByte, OS);
    break;

  case MBlaze::BRI:
  case MBlaze::BRAI:
  case MBlaze::BRID:
  case MBlaze::BRAID:
    EmitIMM(MI,0,CurByte,OS);
    EmitConstant(Value, 4, CurByte, OS);
    break;
  }
}

// FIXME: These #defines shouldn't be necessary. Instead, tblgen should
// be able to generate code emitter helpers for either variant, like it
// does for the AsmWriter.
#define MBlazeCodeEmitter MBlazeMCCodeEmitter
#define MachineInstr MCInst
#include "MBlazeGenCodeEmitter.inc"
#undef MBlazeCodeEmitter
#undef MachineInstr