public override OperatorOutput GenerateBinary(AssemblerState assemblerState, AsmLine asmLine)
{
if (instructions == null)
{
instructions = ReflectionUtilities.FindExtendingClasses <mmix.Instructions.AbstractInstruction>().ToArray();
}
var instruction = instructions.SingleOrDefault(i => i.Symbol == asmLine.Op);
if (instruction == null)
{
throw new Exception("Unknown OP code.");
}
var hex = new byte[] {
instruction.OpCode,
assemblerState.ParseExprToken(asmLine.X).FetchByte(),
assemblerState.ParseExprToken(asmLine.Y).FetchByte(),
assemblerState.ParseExprToken(asmLine.Z).FetchByte(),
};
return(new OperatorOutput()
{
Output = hex
});
}
public override OperatorOutput GenerateBinary(AssemblerState assemblerState, AsmLine asmLine)
{
if (asmLine.ArgCount != 2)
{
throw new Exception("GETA must have exactly two arguments.");
}
// TODO don't forget GETAB[ackwards]
bool backward = false;
var destinationToken = assemblerState.ParseExprToken(asmLine.X);
if (destinationToken.TokenType != ExprToken.ExprTokenType.REGISTER)
{
throw new Exception($"GETA X argument must be a register. {destinationToken.TokenType} received.");
}
ushort relativePointer;
var pointerToken = assemblerState.ParseExprToken(asmLine.Y);
if (pointerToken.TokenType == ExprToken.ExprTokenType.VARIABLE)
{
var octaVar = pointerToken.AssemblerVariable as OctaConstantAssemblerVariable;
if (octaVar == null)
{
throw new Exception($"GETA reference must be an OCTA.");
}
// calculate relative pointer
// TODO a different instruction is emitted if pointer points backwards. Care must be taken with unsigned weirdness.
// divide by 4 for tetra alignment.
relativePointer = (ushort)((octaVar.Constant - assemblerState.ProgramCounter).ToULong() / 4);
}
else if (pointerToken.TokenType == ExprToken.ExprTokenType.CONSTANT)
{
relativePointer = pointerToken.Value;
}
else
{
throw new Exception("GETA RA must be an OCTA reference or a constant.");
}
// GETA code.
byte opCode = 0xF4;
if (backward)
{
// GETAB code.
opCode = 0xF5;
}
var hex = new byte[] {
opCode,
destinationToken.Value
}
.Concat(relativePointer.ToBytes())
.ToArray();
return(new OperatorOutput()
{
Output = hex
});
}