Method DecodeModRM_64

FEXCore/Source/Interface/Core/Frontend.cpp:246–331

}

void Decoder::DecodeModRM_64(X86Tables::DecodedOperand* Operand, X86Tables::ModRMDecoded ModRM) {
  uint8_t Displacement {};
  // Do we have an offset?
  if (ModRM.mod == 0b01) {
    Displacement = 1;
  } else if (ModRM.mod == 0b10) {
    Displacement = 4;
  } else if (ModRM.mod == 0 && ModRM.rm == 0b101) {
    Displacement = 4;
  }

  // Calculate SIB
  bool HasSIB = ((ModRM.mod != 0b11) && (ModRM.rm == 0b100));

  if (HasSIB) {
    FEXCore::X86Tables::SIBDecoded SIB;
    if (DecodeInst->DecodedSIB) {
      SIB.Hex = DecodeInst->SIB;
    } else {
      // Haven't yet grabbed SIB, pull it now
      DecodeInst->SIB = ReadByte();
      SIB.Hex = DecodeInst->SIB;
      DecodeInst->DecodedSIB = true;
    }

    // If the SIB base is 0b101, aka BP or R13 then we have a 32bit displacement
    if (ModRM.mod == 0b00 && ModRM.rm == 0b100 && SIB.base == 0b101) {
      Displacement = 4;
    }

    // SIB
    Operand->Type = DecodedOperand::OpType::SIB;
    Operand->Data.SIB.Scale = 1 << SIB.scale;

    // The invalid encoding types are described at Table 1-12. "promoted nsigned is always non-zero"
    {
      // If we have a VSIB byte (as opposed to SIB), then the index register is a vector.
      // DecodeInst->TableInfo may be null in the case of 3DNow! ModRM decoding.
      const bool IsIndexVector = DecodeInst->TableInfo && (DecodeInst->TableInfo->Flags & InstFlags::FLAGS_VEX_VSIB) != 0;
      uint8_t InvalidSIBIndex = 0b100; ///< SIB Index where there is no register encoding.
      if (IsIndexVector) {
        DecodeInst->Flags |= X86Tables::DecodeFlags::FLAG_VSIB_BYTE;
        InvalidSIBIndex = ~0; ///< No Invalid SIB Index with Index Vectors.
      }

      const uint8_t IndexREX = (DecodeInst->Flags & DecodeFlags::FLAG_REX_XGPR_X) != 0 ? 1 : 0;
      const uint8_t BaseREX = (DecodeInst->Flags & DecodeFlags::FLAG_REX_XGPR_B) != 0 ? 1 : 0;

      Operand->Data.SIB.Index = MapModRMToReg(IndexREX, SIB.index, false, false, IsIndexVector, false, InvalidSIBIndex);
      Operand->Data.SIB.Base = MapModRMToReg(BaseREX, SIB.base, false, false, false, false, ModRM.mod == 0 ? 0b101 : 16);
    }

    LOGMAN_THROW_A_FMT(Displacement <= 4, "Number of bytes should be <= 4 for literal src");

    if (Displacement) {
      uint64_t Literal = ReadData(Displacement);
      if (Displacement == 1) {
        Literal = static_cast<int8_t>(Literal);