Question

Write assembly codes to make the number in register $s1 doubles its original value.

Answer 1

Greetings!

We can double the value of register $s1 by one of the following methods:

1. Multiplying it by 2

2. Bitwise logically shift its content by 1 place

3. Add it to itself

Note:

Refer following assembly code in MIPS for more clarity:

#typed MIPS Assembly Code

.data

message1: .asciiz "initial value of register $s1 = "

message2: .asciiz "\nvalue of register $s1 after multiplying by 2= "

message3: .asciiz "\nvalue of register $s1 after shifting logically left 1 place= "

message4: .asciiz "\nvalue of register $s1 after adding it to itself= "

.text

.globl main

main:

#print message1

li $v0, 4

la $a0, message1

syscall

#$s1 will contain 5, $s1= 0+5 =5

addi $s1, $zero, 5

#print $s1 value

li $v0,1

move $a0, $s1

syscall

#print message2

li $v0, 4

la $a0, message2

syscall

# $s1 = $s1*2 = 5*2 =10

mul $s1, $s1, 2

#print $s1 value

li $v0,1

move $a0, $s1

syscall

#print message3

li $v0, 4

la $a0, message3

syscall

# bitwise shift $s1 content towards left 1 position

# i.e. $s1 = 10 = 01010 after shifting left $s1 = 10100 = 20

sll $s1, $s1, 1

#print $s1 value

li $v0,1

move $a0, $s1

syscall

#print message4

li $v0, 4

la $a0, message4

syscall

#$s1= $s1 + $s1 i.e $s1 = 20+20 =40

add $s1, $s1, $s1

#print $s1 value

li $v0,1

move $a0, $s1

syscall

#end program

li $v0, 10

syscall

#screenshot of the code with output