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In ARM assembly, which instruction is typically used to return from a nested subroutine call?

easy📝 Conceptual Q2 of 15
ARM Architecture - Subroutines and Stack
In ARM assembly, which instruction is typically used to return from a nested subroutine call?
ABL
BMOV PC, R0
CBX LR
DSTR LR, [SP]
Step-by-Step Solution
Solution:

  1. Step 1: Identify the return instruction in ARM

    To return from a subroutine, ARM uses the instruction that branches to the address in the link register (LR).

  2. Step 2: Match instruction to return action

    BX LR branches to the address stored in LR, effectively returning control to the caller.

  3. Final Answer:

    BX LR -> Option C

  4. Quick Check:

    Return from subroutine = BX LR [OK]
Quick Trick: Use BX LR to return from any subroutine call [OK]
Common Mistakes:
  • Confusing BL (branch with link) as return
  • Using MOV PC, R0 incorrectly for return

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