[Solved] Given the following ARM assembly snippet following AAPCS, what will be the value in R0 after the subroutine returns?MOV R0, #5 MOV R1, #3 BL add_two_numbers ; | ARM Architecture

ARM Architecture - Subroutines and Stack

Given the following ARM assembly snippet following AAPCS, what will be the value in R0 after the subroutine returns?

MOV R0, #5
MOV R1, #3
BL add_two_numbers

; Subroutine add_two_numbers:
; Adds R0 and R1, returns result in R0
add_two_numbers:
ADD R0, R0, R1
BX LR

A3

B8

C5

D0

Step-by-Step Solution

Solution:

Step 1: Analyze initial register values before call
R0 = 5, R1 = 3 before calling add_two_numbers.
Step 2: Understand subroutine operation
Subroutine adds R0 and R1, stores result in R0, then returns.
Step 3: Calculate result
5 + 3 = 8, so R0 will hold 8 after return.
Final Answer:
R0 contains 8 after subroutine -> Option B
Quick Check:
Return value = 5 + 3 = 8 [OK]

Quick Trick: Return value is sum stored in R0 after subroutine [OK]

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Given the following ARM assembly snippet following AAPCS, what will be the value in R0 after the subroutine returns?