//===-- MipsInstPrinter.cpp - Convert Mips MCInst to assembly syntax ------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This class prints an Mips MCInst to a .s file.
//
//===----------------------------------------------------------------------===//

#include "MipsInstPrinter.h"
#include "MipsInstrInfo.h"
#include "MipsMCExpr.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

#define DEBUG_TYPE "asm-printer"

#define PRINT_ALIAS_INSTR
#include "MipsGenAsmWriter.inc"

template<unsigned R>
static bool isReg(const MCInst &MI, unsigned OpNo) {
  assert(MI.getOperand(OpNo).isReg() && "Register operand expected.");
  return MI.getOperand(OpNo).getReg() == R;
}

const char* Mips::MipsFCCToString(Mips::CondCode CC) {
  switch (CC) {
  case FCOND_F:
  case FCOND_T:   return "f";
  case FCOND_UN:
  case FCOND_OR:  return "un";
  case FCOND_OEQ:
  case FCOND_UNE: return "eq";
  case FCOND_UEQ:
  case FCOND_ONE: return "ueq";
  case FCOND_OLT:
  case FCOND_UGE: return "olt";
  case FCOND_ULT:
  case FCOND_OGE: return "ult";
  case FCOND_OLE:
  case FCOND_UGT: return "ole";
  case FCOND_ULE:
  case FCOND_OGT: return "ule";
  case FCOND_SF:
  case FCOND_ST:  return "sf";
  case FCOND_NGLE:
  case FCOND_GLE: return "ngle";
  case FCOND_SEQ:
  case FCOND_SNE: return "seq";
  case FCOND_NGL:
  case FCOND_GL:  return "ngl";
  case FCOND_LT:
  case FCOND_NLT: return "lt";
  case FCOND_NGE:
  case FCOND_GE:  return "nge";
  case FCOND_LE:
  case FCOND_NLE: return "le";
  case FCOND_NGT:
  case FCOND_GT:  return "ngt";
  }
  llvm_unreachable("Impossible condition code!");
}

void MipsInstPrinter::printRegName(raw_ostream &OS, unsigned RegNo) const {
  OS << '$' << StringRef(getRegisterName(RegNo)).lower();
}

void MipsInstPrinter::printInst(const MCInst *MI, uint64_t Address,
                                StringRef Annot, const MCSubtargetInfo &STI,
                                raw_ostream &O) {
  switch (MI->getOpcode()) {
  default:
    break;
  case Mips::RDHWR:
  case Mips::RDHWR64:
    O << "\t.set\tpush\n";
    O << "\t.set\tmips32r2\n";
    break;
  case Mips::Save16:
    O << "\tsave\t";
    printSaveRestore(MI, O);
    O << " # 16 bit inst\n";
    return;
  case Mips::SaveX16:
    O << "\tsave\t";
    printSaveRestore(MI, O);
    O << "\n";
    return;
  case Mips::Restore16:
    O << "\trestore\t";
    printSaveRestore(MI, O);
    O << " # 16 bit inst\n";
    return;
  case Mips::RestoreX16:
    O << "\trestore\t";
    printSaveRestore(MI, O);
    O << "\n";
    return;
  }

  // Try to print any aliases first.
  if (!printAliasInstr(MI, Address, O) && !printAlias(*MI, O))
    printInstruction(MI, Address, O);
  printAnnotation(O, Annot);

  switch (MI->getOpcode()) {
  default:
    break;
  case Mips::RDHWR:
  case Mips::RDHWR64:
    O << "\n\t.set\tpop";
  }
}

void MipsInstPrinter::printOperand(const MCInst *MI, unsigned OpNo,
                                   raw_ostream &O) {
  const MCOperand &Op = MI->getOperand(OpNo);
  if (Op.isReg()) {
    printRegName(O, Op.getReg());
    return;
  }

  if (Op.isImm()) {
    O << formatImm(Op.getImm());
    return;
  }

  assert(Op.isExpr() && "unknown operand kind in printOperand");
  Op.getExpr()->print(O, &MAI, true);
}

template <unsigned Bits, unsigned Offset>
void MipsInstPrinter::printUImm(const MCInst *MI, int opNum, raw_ostream &O) {
  const MCOperand &MO = MI->getOperand(opNum);
  if (MO.isImm()) {
    uint64_t Imm = MO.getImm();
    Imm -= Offset;
    Imm &= (1 << Bits) - 1;
    Imm += Offset;
    O << formatImm(Imm);
    return;
  }

  printOperand(MI, opNum, O);
}

void MipsInstPrinter::
printMemOperand(const MCInst *MI, int opNum, raw_ostream &O) {
  // Load/Store memory operands -- imm($reg)
  // If PIC target the target is loaded as the
  // pattern lw $25,%call16($28)

  // opNum can be invalid if instruction had reglist as operand.
  // MemOperand is always last operand of instruction (base + offset).
  switch (MI->getOpcode()) {
  default:
    break;
  case Mips::SWM32_MM:
  case Mips::LWM32_MM:
  case Mips::SWM16_MM:
  case Mips::SWM16_MMR6:
  case Mips::LWM16_MM:
  case Mips::LWM16_MMR6:
    opNum = MI->getNumOperands() - 2;
    break;
  }

  printOperand(MI, opNum+1, O);
  O << "(";
  printOperand(MI, opNum, O);
  O << ")";
}

void MipsInstPrinter::
printMemOperandEA(const MCInst *MI, int opNum, raw_ostream &O) {
  // when using stack locations for not load/store instructions
  // print the same way as all normal 3 operand instructions.
  printOperand(MI, opNum, O);
  O << ", ";
  printOperand(MI, opNum+1, O);
}

void MipsInstPrinter::
printFCCOperand(const MCInst *MI, int opNum, raw_ostream &O) {
  const MCOperand& MO = MI->getOperand(opNum);
  O << MipsFCCToString((Mips::CondCode)MO.getImm());
}

void MipsInstPrinter::
printSHFMask(const MCInst *MI, int opNum, raw_ostream &O) {
  llvm_unreachable("TODO");
}

bool MipsInstPrinter::printAlias(const char *Str, const MCInst &MI,
                                 unsigned OpNo, raw_ostream &OS) {
  OS << "\t" << Str << "\t";
  printOperand(&MI, OpNo, OS);
  return true;
}

bool MipsInstPrinter::printAlias(const char *Str, const MCInst &MI,
                                 unsigned OpNo0, unsigned OpNo1,
                                 raw_ostream &OS) {
  printAlias(Str, MI, OpNo0, OS);
  OS << ", ";
  printOperand(&MI, OpNo1, OS);
  return true;
}

bool MipsInstPrinter::printAlias(const MCInst &MI, raw_ostream &OS) {
  switch (MI.getOpcode()) {
  case Mips::BEQ:
  case Mips::BEQ_MM:
    // beq $zero, $zero, $L2 => b $L2
    // beq $r0, $zero, $L2 => beqz $r0, $L2
    return (isReg<Mips::ZERO>(MI, 0) && isReg<Mips::ZERO>(MI, 1) &&
            printAlias("b", MI, 2, OS)) ||
           (isReg<Mips::ZERO>(MI, 1) && printAlias("beqz", MI, 0, 2, OS));
  case Mips::BEQ64:
    // beq $r0, $zero, $L2 => beqz $r0, $L2
    return isReg<Mips::ZERO_64>(MI, 1) && printAlias("beqz", MI, 0, 2, OS);
  case Mips::BNE:
  case Mips::BNE_MM:
    // bne $r0, $zero, $L2 => bnez $r0, $L2
    return isReg<Mips::ZERO>(MI, 1) && printAlias("bnez", MI, 0, 2, OS);
  case Mips::BNE64:
    // bne $r0, $zero, $L2 => bnez $r0, $L2
    return isReg<Mips::ZERO_64>(MI, 1) && printAlias("bnez", MI, 0, 2, OS);
  case Mips::BGEZAL:
    // bgezal $zero, $L1 => bal $L1
    return isReg<Mips::ZERO>(MI, 0) && printAlias("bal", MI, 1, OS);
  case Mips::BC1T:
    // bc1t $fcc0, $L1 => bc1t $L1
    return isReg<Mips::FCC0>(MI, 0) && printAlias("bc1t", MI, 1, OS);
  case Mips::BC1F:
    // bc1f $fcc0, $L1 => bc1f $L1
    return isReg<Mips::FCC0>(MI, 0) && printAlias("bc1f", MI, 1, OS);
  case Mips::JALR:
    // jalr $ra, $r1 => jalr $r1
    return isReg<Mips::RA>(MI, 0) && printAlias("jalr", MI, 1, OS);
  case Mips::JALR64:
    // jalr $ra, $r1 => jalr $r1
    return isReg<Mips::RA_64>(MI, 0) && printAlias("jalr", MI, 1, OS);
  case Mips::NOR:
  case Mips::NOR_MM:
  case Mips::NOR_MMR6:
    // nor $r0, $r1, $zero => not $r0, $r1
    return isReg<Mips::ZERO>(MI, 2) && printAlias("not", MI, 0, 1, OS);
  case Mips::NOR64:
    // nor $r0, $r1, $zero => not $r0, $r1
    return isReg<Mips::ZERO_64>(MI, 2) && printAlias("not", MI, 0, 1, OS);
  case Mips::OR:
    // or $r0, $r1, $zero => move $r0, $r1
    return isReg<Mips::ZERO>(MI, 2) && printAlias("move", MI, 0, 1, OS);
  default: return false;
  }
}

void MipsInstPrinter::printSaveRestore(const MCInst *MI, raw_ostream &O) {
  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
    if (i != 0) O << ", ";
    if (MI->getOperand(i).isReg())
      printRegName(O, MI->getOperand(i).getReg());
    else
      printUImm<16>(MI, i, O);
  }
}

void MipsInstPrinter::
printRegisterList(const MCInst *MI, int opNum, raw_ostream &O) {
  // - 2 because register List is always first operand of instruction and it is
  // always followed by memory operand (base + offset).
  for (int i = opNum, e = MI->getNumOperands() - 2; i != e; ++i) {
    if (i != opNum)
      O << ", ";
    printRegName(O, MI->getOperand(i).getReg());
  }
}