Question

ARM on a raspberry pi 
1. Create a assembly program that branches based off the value of three different variables.

## Details

Task 1:
    I highly suggest reading the book and doing the practice before doing this.
    Name your file cp5.s.
    You need to initally start with the three variables.
        * the variables should be called max, t1, t2.
        * Set the values to whatever you would like.
        * max tells us the cut off for a value
        * if t1 or t2 greater than max we branch to a function that adds 2 to the register r0.
        * if t1 or t2 less than the max we branch to a function that adds 1 to the register r0.
    Your main should,
        1. load the addresses of the variables into a register.
        2. Load the values within the variables.
        3. Compare the variables and branch to the functions that do something to r0.
        4. Finally your program should return 2,3, or 4 depending on the values of t1 and t2.
    You will also need to create a makefile to build your assembly code as well.


## Gradding
    Task 1:
        I will first run your makefile.
        Your makfile should create files specified in the chapter. (1 point)
        I will run your code useing this command `./cp5 ; echo $?`.
        The output should be 2,3, or 4. (2 points)
        When I run `make clean` the files created by your make should be deleted. (1 point)
        Loading memory from variables will be worth 2 points.
        Do a comparison that branches to a new funtion depending on the comparison. (2 points)
        Return a correct value based on the values of the variables.

Answer 1

.data

.align 4
t1:
    .word 0

.align 4
t2:
    .word 0

.align 4
max:
    .word 0

.align 4

.global main

main:

    ldr r1, addr_of_t1
    mov r3, #5
    str r3, [r1]
    ldr r2, addr_of_t2
    mov r3, #8
    str r3, [r2]
    ldr r4, addr_of_max
    mov r3, #10
    str r3, [r4]

ldr r1, addr_of_t1

ldr r1, [r1]

ldr r2, addr_of_t2

ldr r2, [r2]

ldr r4, addr_of_max

ldr r4, [r4]

cmp r1, r4

blt r1_lower

cmp r2, r4

blt r2_lower

mov r0, #1




r1_lower:

    mov r0, #2

    b end

r2_lower:

    mov r0, #2

    b end


addr_of_t1: .word t1

addr_of_t2: .word t2

addr_of_max: .word max