public static OpcodeEncoder AppendRM(this OpcodeEncoder encoder, Operand operand)
{
if (operand.IsCPURegister)
return encoder.AppendRM(operand.Register);
else
return encoder.AppendRM(Bits.b101);
}
public static OpcodeEncoder ModRegRMSIBDisplacement(this OpcodeEncoder encoder, bool offsetDestination, Operand destination, Operand source, Operand offset)
{
if (offsetDestination && source.IsConstant)
{
var baseEBP = destination.Register == GeneralPurposeRegister.EBP;
if (baseEBP)
{
if (offset.IsCPURegister || Is8BitDisplacement(offset))
{
encoder.AppendMod(Bits.b01); // 2:mod
}
else
{
encoder.AppendMod(Bits.b10); // 2:mod
}
}
else
{
encoder.AppendMod(true, offset); // 2:mod
}
encoder.AppendRegister(Bits.b000); // 3:register (destination)
if (offset.IsCPURegister)
{
encoder.AppendRM(Bits.b100); // 3:r/m (source)
encoder.AppendSIB(1, offset.Register, destination.Register); // 8:sib (scale, index, base)
if (baseEBP)
{
encoder.AppendByteValue(0x0); // 8:displacement value
}
}
else if (destination.Register == GeneralPurposeRegister.ESP)
{
// When destination is ESP we must use SIB
encoder.AppendRM(Bits.b100); // 3:r/m (source)
encoder.AppendSIB(1, destination.Register, destination.Register); // 8:sib (scale, index, base)
encoder.AppendConditionalDisplacement(offset); // 8/32:displacement value
}
else
{
encoder.AppendRM(destination); // 3:r/m (source)
if (baseEBP)
{
encoder.AppendConditionalDisplacement(true, offset); // 8/32:displacement value
}
else
{
encoder.AppendConditionalDisplacement(offset); // 8/32:displacement value
}
}
}
else if (offset.IsConstant)
{
// When source is ESP we must use SIB
encoder.AppendMod(true, offset); // 2:mod
encoder.AppendRegister(destination.Register); // 3:register (destination)
if (source.Register == GeneralPurposeRegister.ESP)
{
encoder.AppendRM(Bits.b100); // 3:r/m (source)
encoder.AppendSIB(1, source.Register, source.Register); // 8:sib (scale, index, base)
}
else
{
encoder.AppendRM(source); // 3:r/m (source)
}
encoder.AppendConditionalDisplacement(offset); // 8/32:displacement value
}
else
{
// When EBP is the base we must set the mod to either:
// b01 with a 1 byte displacement
// b10 with a 4 byte displacement
var @base = offsetDestination ? destination : source;
var baseEBP = @base.Register == GeneralPurposeRegister.EBP;
encoder.AppendMod(baseEBP ? Bits.b01 : Bits.b00); // 2:mod
encoder.AppendRegister(destination.Register); // 3:register (destination)
encoder.AppendRM(Bits.b100); // 3:r/m (source)
encoder.AppendSIB(1, offset.Register, @base.Register); // 8:sib (scale, index, base)
if (baseEBP)
{
encoder.AppendByteValue(0x0); // 8:displacement value
}
}
return encoder;
}
public static OpcodeEncoder ModRegRMSIBDisplacement(this OpcodeEncoder encoder, Operand result, Operand op1, Operand op2)
{
if (op2.IsConstant)
{
encoder.AppendMod(true, op2); // 2:mod
encoder.AppendRegister(result.Register); // 3:register (destination)
encoder.AppendRM(op1); // 3:r/m (source)
encoder.AppendConditionalDisplacement(op2); // 8/32:displacement value
}
else
{
encoder.AppendMod(Bits.b00); // 2:mod
encoder.AppendRegister(result.Register); // 3:register (destination)
encoder.AppendRM(Bits.b100); // 3:r/m (source)
encoder.AppendSIB(1, op2.Register, op1.Register); // 8:sib (scale, index, base)
}
return encoder;
}