Compare and branch patterns in ARM Architecture - Mini Project: Build & Apply

Compare and Branch Patterns in ARM Assembly

📖 Scenario: You are learning how ARM processors decide what to do next based on comparing values. This is important for making decisions in programs, like choosing between two options.

🎯 Goal: Build a simple ARM assembly code snippet that compares two numbers and branches (jumps) to different parts of the code depending on the comparison result.

📋 What You'll Learn

Create two registers with specific values

Set up a comparison instruction between the two registers

Use a conditional branch instruction based on the comparison

Add labels to mark the branch destinations

💡 Why This Matters

🌍 Real World

ARM processors use compare and branch instructions to make decisions in embedded systems, mobile devices, and many electronics.

💼 Career

Understanding compare and branch patterns is essential for embedded software developers and anyone working with low-level ARM assembly programming.

1

Set up registers with values

Write ARM assembly code to load the value 5 into register r0 and the value 10 into register r1.

ARM Architecture

# Load 5 into r0 and 10 into r1
# Your code here

Need a hint?

Use the MOV instruction to put numbers into registers.

2

Compare the two registers

Add an ARM assembly instruction to compare the value in r0 with the value in r1 using the CMP instruction.

ARM Architecture

MOV r0, #5
MOV r1, #10
# Compare r0 and r1
# Your code here

Need a hint?

The CMP instruction subtracts the second register from the first and sets flags for branching.

3

Branch if less than

Write a conditional branch instruction BLT that jumps to the label less_than if r0 is less than r1.

ARM Architecture

MOV r0, #5
MOV r1, #10
CMP r0, r1
# Branch to less_than if r0 < r1
# Your code here

Need a hint?

The BLT instruction branches if the previous comparison shows the first value is less than the second.

4

Add branch labels and final instructions

After the BLT, add MOV r2, #0 (for when r0 >= r1) followed by B end to skip the less_than block. Then add the label less_than: followed by MOV r2, #1. Finally, add the label end:.

ARM Architecture

MOV r0, #5
MOV r1, #10
CMP r0, r1
BLT less_than
# Add labels less_than and end with MOV instructions
# Your code here

Need a hint?

Labels mark places to jump to. Use B to jump unconditionally to end after the branch.