[Solved] What is wrong with this ARM code snippet?BL subroutine MOV R0, #3 subroutine: MOV R0, #4 BX R14 — Ans: BX R14 should be BX LR for clarity | ARM Architecture

ARM Architecture - Control Flow Instructions

What is wrong with this ARM code snippet?

BL subroutine
MOV R0, #3
subroutine:
MOV R0, #4
BX R14

ABL cannot be used before MOV instructions

BBX R14 should be BX LR for clarity

CBX R14 is correct to return from subroutine

DMOV R0, #3 should be after subroutine

Step-by-Step Solution

Solution:

Step 1: Understand BX instruction
BX R14 is functionally correct since LR is R14, but using BX LR is clearer and standard.
Step 2: Identify best practice
Using BX LR improves readability and avoids confusion.
Final Answer:
BX R14 should be BX LR for clarity -> Option B
Quick Check:
Use BX LR instead of BX R14 for clarity [OK]

Quick Trick: Use BX LR (not BX R14) for clearer return [OK]

Common Mistakes:

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