// Copyright 2008 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#include "Common/x64Analyzer.h"

bool DisassembleMov(const unsigned char* codePtr, InstructionInfo* info)
{
  unsigned const char* startCodePtr = codePtr;
  u8 rex = 0;
  u32 opcode;
  int opcode_length;

  // Check for regular prefix
  info->operandSize = 4;
  info->zeroExtend = false;
  info->signExtend = false;
  info->hasImmediate = false;
  info->isMemoryWrite = false;
  info->byteSwap = false;

  u8 modRMbyte = 0;
  u8 sibByte = 0;
  bool hasModRM = false;

  int displacementSize = 0;

  if (*codePtr == 0x66)
  {
    info->operandSize = 2;
    codePtr++;
  }
  else if (*codePtr == 0x67)
  {
    codePtr++;
  }

  // Check for REX prefix
  if ((*codePtr & 0xF0) == 0x40)
  {
    rex = *codePtr;
    if (rex & 8)  // REX.W
    {
      info->operandSize = 8;
    }
    codePtr++;
  }

  opcode = *codePtr++;
  opcode_length = 1;
  if (opcode == 0x0F)
  {
    opcode = (opcode << 8) | *codePtr++;
    opcode_length = 2;
    if ((opcode & 0xFB) == 0x38)
    {
      opcode = (opcode << 8) | *codePtr++;
      opcode_length = 3;
    }
  }

  switch (opcode_length)
  {
  case 1:
    if ((opcode & 0xF0) == 0x80 || ((opcode & 0xF8) == 0xC0 && (opcode & 0x0E) != 0x02))
    {
      modRMbyte = *codePtr++;
      hasModRM = true;
    }
    break;
  case 2:
    if (((opcode & 0xF0) == 0x00 && (opcode & 0x0F) >= 0x04 && (opcode & 0x0D) != 0x0D) ||
        ((opcode & 0xF0) == 0xA0 && (opcode & 0x07) <= 0x02) || (opcode & 0xF0) == 0x30 ||
        (opcode & 0xFF) == 0x77 || (opcode & 0xF0) == 0x80 || (opcode & 0xF8) == 0xC8)
    {
      // No mod R/M byte
    }
    else
    {
      modRMbyte = *codePtr++;
      hasModRM = true;
    }
    break;
  case 3:
    // TODO: support more 3-byte opcode instructions
    if ((opcode & 0xFE) == 0xF0)
    {
      modRMbyte = *codePtr++;
      hasModRM = true;
    }
    break;
  }

  if (hasModRM)
  {
    ModRM mrm(modRMbyte, rex);
    info->regOperandReg = mrm.reg;
    if (mrm.mod < 3)
    {
      if (mrm.rm == 4)
      {
        // SIB byte
        sibByte = *codePtr++;
        info->scaledReg = (sibByte >> 3) & 7;
        info->otherReg = (sibByte & 7);
        if (rex & 2)
          info->scaledReg += 8;
        if (rex & 1)
          info->otherReg += 8;
      }
      else
      {
        // info->scaledReg =
      }
    }
    if (mrm.mod == 1 || mrm.mod == 2)
    {
      if (mrm.mod == 1)
        displacementSize = 1;
      else
        displacementSize = 4;
    }
  }

  if (displacementSize == 1)
    info->displacement = (s32)(s8)*codePtr;
  else
    info->displacement = *((s32*)codePtr);
  codePtr += displacementSize;

  switch (opcode)
  {
  case 0xC6:  // mem <- imm8
    info->isMemoryWrite = true;
    info->hasImmediate = true;
    info->immediate = *codePtr;
    info->operandSize = 1;
    codePtr++;
    break;

  case 0xC7:  // mem <- imm16/32
    info->isMemoryWrite = true;
    switch (info->operandSize)
    {
    case 2:
      info->hasImmediate = true;
      info->immediate = *(u16*)codePtr;
      codePtr += 2;
      break;

    case 4:
      info->hasImmediate = true;
      info->immediate = *(u32*)codePtr;
      codePtr += 4;
      break;

    case 8:
      info->zeroExtend = true;
      info->immediate = *(u32*)codePtr;
      codePtr += 4;
      break;
    }
    break;

  case 0x88:  // mem <- r8
    info->isMemoryWrite = true;
    if (info->operandSize != 4)
    {
      return false;
    }
    info->operandSize = 1;
    break;

  case 0x89:  // mem <- r16/32/64
    info->isMemoryWrite = true;
    break;

  case 0x8A:  // r8 <- mem
    if (info->operandSize != 4)
    {
      return false;
    }
    info->operandSize = 1;
    break;

  case 0x8B:  // r16/32/64 <- mem
    break;

  case 0x0FB6:  // movzx on byte
    info->zeroExtend = true;
    info->operandSize = 1;
    break;

  case 0x0FB7:  // movzx on short
    info->zeroExtend = true;
    info->operandSize = 2;
    break;

  case 0x0FBE:  // movsx on byte
    info->signExtend = true;
    info->operandSize = 1;
    break;

  case 0x0FBF:  // movsx on short
    info->signExtend = true;
    info->operandSize = 2;
    break;

  case 0x0F38F0:  // movbe read
    info->byteSwap = true;
    break;

  case 0x0F38F1:  // movbe write
    info->byteSwap = true;
    info->isMemoryWrite = true;
    break;

  default:
    return false;
  }
  info->instructionSize = (int)(codePtr - startCodePtr);
  return true;
}

bool InstructionInfo::operator==(const InstructionInfo& other) const
{
  return operandSize == other.operandSize && instructionSize == other.instructionSize &&
         regOperandReg == other.regOperandReg && otherReg == other.otherReg &&
         scaledReg == other.scaledReg && zeroExtend == other.zeroExtend &&
         signExtend == other.signExtend && hasImmediate == other.hasImmediate &&
         isMemoryWrite == other.isMemoryWrite && byteSwap == other.byteSwap &&
         immediate == other.immediate && displacement == other.displacement;
}