Question

Assembly lang

multiple choice

Suppose we have the following pseudo-instruction in our program:

push {r0, r2, r4}

.....

Which of the following instructions would be the appropriate instruction to use when cleaning up the stack space used by the three register values that were pushed onto the stack?

Group of answer choices

sub sp, #12

add sp, #12

add lr, #12

2)

Suppose we are comparing registers R1 and R2 and we want to branch if equal to the label named next, would the following code snippet achieve this for us?

cmp r1, r2

be next

...

...

next:

True

or

False

3)

The following Assembly Code snippet will divide the contents of register R2 by sixteen and add it to the contents of register R1; storing the result of 9 in R1?

mov r1, #5

mov r2, #64

add r1, r2, asr #4

true or false

Answer 1

1. Option b is correct because stack is growing with decreasing address. Hence adding value 12 in stack pointer is equivalent to ignoring top 3 elements.

2. True , this code is correct for that.

3.True because in the last instruction , asr #4 will shift the content of R2 by 4 bit right, which is equivalent to diving content of R2 by 2⁴ = 16 and hence content of R2 will become 64/16 = 4 and hence content of R1 will become 5+4 = 9

Please comment for any clarification