Homework Assignment 1

Remember: You are encouraged to turn in individual problems as soon as possible, rather than turning in the whole assignment on the due date. Please mark each problem with the exercise number from the book.

• Do exercise 11.3 on page 347. You may want to test out your code in SLIME.
• Do exercise 11.17 on page 372.
  • For part (a) two opcodes can be eliminated; show how to rewrite each instruction using one of the eliminated opcodes in terms of a non-eliminated opcode.
  • For part (b) all but one opcode can be eliminated. To argue an individual opcode can be eliminated, give specific code fragments showing how an instruction using it can be rewritten in terms of any uneliminated opcodes. For example, assuming we have an otherwise unused register tmp at our disposal, we can start by eliminating sne, since

      sne s, a, b
    

    can be replaced by the sequence of instructions:

      seq s, a, b
      li tmp, 1
      sub s, tmp, s
    

    or with the sequence of instructions:

      sub, s, a, b
      li tmp, done-label
      jeqz s, tmp
      li s, 1
    done-label:
    

    Remember, that the instruction you are replacing could appear anywhere in a larger program, so (for example) your proposed replacement should not halt. (See how few auxiliary registers like tmp you can get away with.)

• Do exercise 11.18 on page 373. You may want to test out your code in SLIME.