Exercise 1

Based on Patterson & Hennessy, pages 54–56. Step through the program below instruction by instruction and fill in the table, recording the PC value, the instruction being executed, and the value of the modified registers after each instruction.

Exercise

Assembly Code

# C expression: f = (g + h) - (i + j)

.text

main:
  addi t1, zero, 4      # g = 4
  addi t2, zero, 3      # h = 3
  addi t3, zero, 2      # i = 2
  addi t4, zero, 1      # j = 1

  add  t5, t1, t2       # t5 = g + h
  add  t6, t3, t4       # t6 = i + j
  sub  t0, t5, t6       # f = t5 - t6 (result in t0)

Fill in the table below

Before		After executing the instruction
PC	Instruction	R5	R6	R7	R28	R29	R30	R31
		(t0)	(t1)	(t2)	(t3)	(t4)	(t5)	(t6)
		0x00000000	0x00000000	0x00000000	0x00000000	0x00000000	0x00000000	0x00000000
0x00400000	addi t1 zero 4	0x00000000	0x00000004	0x00000000	0x00000000	0x00000000	0x00000000	0x00000000