Question

Convert each of the below C code snippet to LEGv8 assembly code. Assume the variables a, b, and c are stored in registers X19, X20, and X21 respectively. Base address of d is stored in register X22. Comment your assembly code.

a. if (a > b) d[a] = b + 8;

else d[a] = b - 16;

b. for (i=0;i 0) i++;

a = d[i] + c;

c. i = 0;

while (d[i] == b)

if ((a - i) > 0) i++;

(P.S. I am relatively new to this material so please use beginner instructions only)

Answer 1

let a= s0, b= s1, d[a]= s2, whileb is not considered let c= s1

a) bgez $s0, $s1, greater \\ if (a > b)

blez $s0, $s1, smaller \\ if (a < b)

greater: addu $s2, $s1, 8 \\ d[a] = b + 8

smaller: sub $s2, $s1,16 \\ d[a] = b - 16

b) ori $s5, $s0, 0 \\ i=0

la $s6, d \\ $s6= d;

l1: bge $s5, $s1, done \\ i<a   

lw s7 ,0($s6) \\ $s7= d[i]

addu $s0, $s7, $s1 \\ a = d[i] + c

j update

update: addi $s5, $s5, 1 \\ i++

addi $s6, $s6, 4

j l1

done: .data \\ initialize data

c) ori $s5, $s0, 0 \\ i=0

lw $s7 ,0($s6)​ \\ $s7= d[i]

l1: bne $s7, $s1, done

sub $s4, $s0, $s5

ble $s4, done

add $s1, $s1, 1

j l1

done: exit