Simple assembler for 12-bit data, 13-bit insrtuction ISA

assembler.py

una_ops = {
    'not': 0b0001,
    'inv': 0b0010,
    'sll': 0b0011,
    'srl': 0b0100,
    'sla': 0b0101,
    'sra': 0b0110,
    'cp' : 0b0110,
}

duo_ops = {
    'or' : 0b0001,
    'and': 0b0010,
    'add': 0b0011,
    'sub': 0b0100,
    'lt' : 0b0101,
    'gt' : 0b0110,
    'eq' : 0b0111,
    'neq': 0b1000,
}

def enc_op(op, rd, rs, rt):
     return op << 9 | rd << 6 | rs << 3 | rt

def dec_reg(reg: str):
    if reg[0] != 'r':
        raise Exception('not a register: ' + reg)
    return int(reg[1:])
 
def dec_mnem_args(mnem: str, args: [str]):
    if mnem == 'zero':
        o, d, s, t = 0, dec_reg(args[0]), 0, 0
    elif mnem in una_ops:
        o, d, s, t = 0, dec_reg(args[0]), dec_reg(args[1]), una_ops[mnem]
    elif mnem in duo_ops:
        o, d, s, t = duo_ops[mnem], dec_reg(args[0]), dec_reg(args[1]), dec_reg(args[2])
    elif mnem in ('lw', 'sw'):
        o = 0b1001 if mnem == 'lw' else 0b1010
        d, s, t = dec_reg(args[0]), dec_reg(args[1]), int(args[2])
    else:
        raise Exception('unknown mnemonic: ' + mnem)
    return enc_op(o, d, s, t)

def assemble(line):
    line = line.split()
    return dec_mnem_args(line[0], line[1:])


if __name__ == '__main__':
    try:
        while True:
            line = input()
            if line != '' and not line.isspace():
                print(hex(assemble(line))[2:].rjust(4, '0'))
    except EOFError:
        pass