Question

For the MIPS assembly instructions below, what is the corresponding C statement? Assume that the variables f, g, h, and I are assigned to registers $s0 - $s3, respectively. Assume that the base address of arrays X, Y, and Z are in registers $s4 - $s6, respectively. Be conservative and use a single temp register as possible. It is a C arithmetic command with two source operands and a destination. Each part is 3 points.

Add	$t0, $s0, $s1
addi	$t0, $t0, -1
sll	$t0, $t0, 2
add	$t0, $s4, $t0
lw	$t0, 0($t0)
sub	$t1, $s2, $s3
addi	$t1, $t1, -1
sll	$t1, $t1, 2
add	$t1, $s5, $t1
lw	$t1, 0($t1)
add	$t0, $t0, $t1
add	$t1, $s1, $s2
sll	$t1, $t1, 2
add	$t1, $t1, $s6
sw	$t0, 0($t1)

Answer 1

f: $s0
g: $s1
h: $s2
i: $s3
X: $s4
Y: $s5
Z: $s6
Lets assume temp = $t0
           temp1 = $t1

ADD $t0, $s0, $s1   # Add $s0, $s1, and store in $t0: temp = f+g
ADDI $t0, $t0, -1 # Decrement $t0: $t0 = $t0 - 1, or temp--
SLL $t0, $t0, 2   # Shift Left $t0 by 2 bits: temp = temp << 2
ADD $t0, $s4, $t0   # Add $s4, $t0, and store in $t0: temp = temp + X[0], or temp += X[0]
LW $t0, 0($t0)   # Load from $t0 to $t0: temp = temp (This doesn't make much sense.)
SUB $t1, $s2, $s3 # Subtract $s3 from $s2, and store in $t1: temp1 = h - i
ADDI $t1, $t1, -1   # Decrement $t1: $t1 = $t1 - 1, or temp1--
SLL $t1, $t1, 2       # Shift Left $t1 by 2 bits: temp1 = temp1 << 2
ADD $t1, $s5, $t1   # Add $s5, $t1, and store in $t1: temp1 = temp1 + Y[0], or temp1 += Y[0]
LW $t1, 0($t1)       # Load from $t1 to $t1: temp1 = temp1 (This doesn't make much sense.)
ADD $t0, $t0, $t1   # Add $t0, $t1, and store in $t0: temp = temp + temp1, or temp += temp1
ADD $t1, $s1, $s2   # Add $s1, $s2, and store in $t1: temp1 = g + h
SLL $t1, $t1, 2       # Shift Left $t1 by 2 bits: temp1 = temp1 << 2
ADD $t1, $t1, $s6   # Add $t1, $s6, and store in $t1: temp1 = temp1 + Z[0], or temp1 += Z[0]
SW   $t0, 0($t1)       # Store Word $t1 into $t0: temp = temp1