[Solved] What happens to the link register (LR) during a nested subroutine call in ARM architecture? — Ans: It stores the return address of the current subroutine before calling the next | ARM Architecture

ARM Architecture - Subroutines and Stack

What happens to the link register (LR) during a nested subroutine call in ARM architecture?

AIt holds the address of the nested subroutine permanently

BIt is cleared to zero

CIt is ignored during nested calls

DIt stores the return address of the current subroutine before calling the next

Step-by-Step Solution

Solution:

Step 1: Understand the role of LR in subroutine calls
The link register (LR) holds the return address so the program knows where to continue after a subroutine finishes.
Step 2: Analyze nested calls effect on LR
During nested calls, LR is updated to store the return address of the current subroutine before jumping to the next one, preserving the call chain.
Final Answer:
It stores the return address of the current subroutine before calling the next -> Option D
Quick Check:
LR usage in nested calls = store return address [OK]

Quick Trick: LR always saves return address before next call [OK]

Common Mistakes:

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What happens to the link register (LR) during a nested subroutine call in ARM architecture?