Instruction scheduling in Compiler Design - Mini Project: Build & Apply

Instruction Scheduling Basics

📖 Scenario: You are working on a simple compiler that needs to arrange instructions to run efficiently on a processor. Some instructions depend on the results of others, so they cannot run before their dependencies are ready.Your task is to organize a small set of instructions in an order that respects these dependencies.

🎯 Goal: Build a list of instructions and reorder them so that no instruction runs before the instructions it depends on.

📋 What You'll Learn

Create a dictionary of instructions with their dependencies

Create a list to hold the scheduled instructions

Implement a simple scheduling loop that respects dependencies

Complete the schedule by adding all instructions in a valid order

💡 Why This Matters

🌍 Real World

Instruction scheduling is used in compilers to arrange machine instructions so processors run them efficiently without waiting for data.

💼 Career

Understanding instruction scheduling helps compiler engineers optimize code performance and is valuable for roles in systems programming and hardware design.

1

Create the instruction dependency dictionary

Create a dictionary called instructions with these exact entries: 'I1': [], 'I2': ['I1'], 'I3': ['I1'], 'I4': ['I2', 'I3']

Compiler Design

# Create the instructions dictionary with dependencies
# Your code here

Need a hint?

Use a dictionary where keys are instruction names and values are lists of instructions they depend on.

2

Create an empty list for the scheduled instructions

Create an empty list called schedule to hold the instructions in the order they will run.

Compiler Design

instructions = {
    'I1': [],
    'I2': ['I1'],
    'I3': ['I1'],
    'I4': ['I2', 'I3']
}
# Create an empty list called schedule
# Your code here

Need a hint?

Use an empty list to store the final order of instructions.

3

Schedule instructions respecting dependencies

Write a while loop that continues until all instructions are scheduled. Inside the loop, use a for loop with variables instr and deps to iterate over instructions.items(). If instr is not in schedule and all dependencies in deps are in schedule, append instr to schedule.

Compiler Design

instructions = {
    'I1': [],
    'I2': ['I1'],
    'I3': ['I1'],
    'I4': ['I2', 'I3']
}
schedule = []
# Schedule instructions respecting dependencies
# Your code here

Need a hint?

Use a loop to add instructions only when their dependencies are already scheduled.

4

Complete the instruction scheduling

Add a final comment line # Instruction scheduling complete after the scheduling loop to mark the end of the process.

Compiler Design

instructions = {
    'I1': [],
    'I2': ['I1'],
    'I3': ['I1'],
    'I4': ['I2', 'I3']
}
schedule = []

while len(schedule) < len(instructions):
    for instr, deps in instructions.items():
        if instr not in schedule and all(dep in schedule for dep in deps):
            schedule.append(instr)
# Instruction scheduling complete

Need a hint?

Add a comment to show the scheduling process is done.