Page 1

Question 1

• full credit for nop

Question 2

• full credit for mentioning condition codes
• half credit for nop
• none for incorrect statements

Page 2

Questions 3–6

• Full credit for getting the right answer.
• Partial for one of
  • having one extra modification
  • missing the modification
  • having the wrong value in the correct register
  • having the wrong register with the correct value
• No credit if have two or more of above problems

extraneous %, 0x, etc OK.

Correct answers:

• Q3
  • RDX = 0x100000009 (half for the 32-bit register answer 0x9)
• Q4
  • RSP = 28 (also accept 22)
• Q5
  • none (condition codes are not program registers)
• Q6
  • accept RSI = 1110 or RSI = 11110

Page 3

Question 7

This code (a) changes %rsp and (b) jumps to flub. Hence,

• Full credit for C or H
• Half credit for G or I
• No credit for the other options

Question 8

• full credit for 4
• half credit for 6

Question 9

• full for 16, half for 12

Question 10

• full for our

Page 4

The following errors are in the code:

• Line 1 does nothing (i.e., unused thereafter)
• Line 12 uses wrong sizeof
• Line 21 should be *array not *ans
• Line pair (12, 23) constitute a memory leak

Question 11

• full for 22
• half for any other not-in-loop before-return line (12 through 15)

Question 12

• full for ans

Question 13

• blank 1: 18; this is subtle enough, full credit for none as well
• blank 2: none
• blank 3: 13, 18, 19
• blank 4: none
• blank 5: none
• blank 6: 12

Page 5

Question 14

An example correct solution:

    int i = 0;
loop:
    if (i >= n) goto end;
    if (i % x == 0) y *= i;
    if (i % x != 0) z += 1;
    i += 1;
    goto loop;
end:

The if/else can be done as either of

    if (i % x == 0) y *= i;
    if (i % x != 0) z += 1;

or

    if (i % x == 0) goto ifcase;
    z += 1;
    goto endif
ifcase:
    y *= i;
endif:

And the loop can be done as either of

    int i = 0;
loop:
    if (i >= n) goto end;
    // if goes here
    i += 1;
    goto loop;
end:

or

    int i = 0;
    goto guard;
loop:
    // if goes here
    i += 1;
guard:
    if (i < n) goto loop;

Page 6

Question 15

• Should comment freeing a, b, and d (half if one left, 0 if all);
• Should not comment freeing c (all or nothing)

Question 16

• Full of L, half for R

Question 17

• Full of R, half for C

Question 18

• Full of C