Somewhat simplify "sub" instructions. Correctly sign extend operands for "mul". Put the correct half of the result in MDR for "mul" and "mulu". Implement remaining instructions. Tweak opcode for "syscall".
Somewhat simplify "sub" instructions. Correctly sign extend operands for "mul". Put the correct half of the result in MDR for "mul" and "mulu". Implement remaining instructions. Tweak opcode for "syscall".