Question

2.4 For the MIPS assembly instructions below, what is the corresponding C statement? Assume that the variables f, g, h, i, and j are assigned to registers $s0, $s1, $s2, $s3, and $s4, respectively. Assume that the base address of the arrays A and B are in registers $s6 and $s7, respectively.

sll $t0, $s0, 2               # $t0 = f * 4

add $t0, $s6, $t0         # $t0 = &A[f]

sll $t1, $s1, 2               # $t1 = g * 4

add $t1, $s7, $t1         # $t1 = &B[g]

lw $s0, 0($t0)              # f = A[f]

addi $t2, $t0, 4

lw $t0, 0($t2)

add $t0, $t0, $s0

sw $t0, 0($t1)

Answer 1

sll $t0, $s0, 2     # $t0 = f * 4
add $t0, $s6, $t0   # $t0 = &A[f]
sll $t1, $s1, 2     # $t1 = g * 4
add $t1, $s7, $t1   # $t1 = &B[g]
lw $s0, 0($t0)      # f = A[f]
addi $t2, $t0, 4    # $t2 = &A[f+1]
lw $t0, 0($t2)      # $t0 = A[f+1]
add $t0, $t0, $s0   # $t0 = A[f+1] + A[f]
sw $t0, 0($t1)      # B[g] = A[f+1] + A[f]

Answer: B[g] = A[f+1] + A[f]