public Encoding Encode(AddressSize defaultAddressSize, byte modReg, DisplacementSize displacementSize)
{
if ((defaultAddressSize == AddressSize._16 && AddressSize == AddressSize._64)
|| (defaultAddressSize == AddressSize._64 && AddressSize == AddressSize._16))
throw new ArgumentException(nameof(defaultAddressSize));
if (modReg >= 8) throw new ArgumentException(nameof(modReg));
if (!IsEncodableWithDisplacementSize(displacementSize))
throw new ArgumentException(nameof(displacementSize));
var encoding = new Encoding()
{
Segment = RequiresSegmentOverride ? Segment : (SegmentRegister?)null,
AddressSizeOverride = AddressSize != defaultAddressSize,
BaseRegExtension = BaseAsGprCode >= GprCode.R8,
IndexRegExtension = IndexAsGprCode >= GprCode.R8,
Displacement = displacement
};
if (AddressSize == AddressSize._16) throw new NotImplementedException();
byte mod;
switch (displacementSize)
{
case DisplacementSize._0: mod = 0; break;
case DisplacementSize._8: mod = 1; break;
default: mod = 2; break;
}
var @base = Base;
bool needsSib = false;
if (AddressSize == AddressSize._64)
{
// Same as 32-bit except that [disp32] encodes [rip + disp32]
if ([email protected]) needsSib = true;
if (@base == AddressBaseRegister.Rip) @base = null;
}
if (@base == AddressBaseRegister.SP || (mod == 0 && @base == AddressBaseRegister.BP))
needsSib = true;
if (needsSib)
{
if (@base == AddressBaseRegister.BP) throw new NotImplementedException();
encoding.ModRM = ModRMEnum.FromComponents(mod, modReg, 0) | ModRM.RM_Sib;
encoding.Sib = SibEnum.FromComponents(
ss: (byte)((int)(flags & Flags.Scale_Mask) >> (int)Flags.Scale_Shift),
index: (IndexAsGprCode ?? GprCode.SP).GetLow3Bits(),
@base: (BaseAsGprCode ?? GprCode.BP).GetLow3Bits());
}
else
{
encoding.ModRM = ModRMEnum.FromComponents(mod, modReg, (byte)((byte)@base.Value & 0x7));
}
return encoding;
}
public bool IsEncodableWithDisplacementSize(DisplacementSize size)
{
return size >= MinimumDisplacementSize
&& (size == DisplacementSize._16) == (AddressSize == AddressSize._16);
}
