Dead code elimination in Compiler Design - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is dead code in programming?

Dead code refers to parts of a program that are never executed or whose results are never used. These code sections do not affect the program's output.

beginner

What is the purpose of dead code elimination in compilers?

Dead code elimination removes unnecessary code that does not affect the program's behavior, making the program smaller and faster.

intermediate

How does dead code elimination improve program performance?

By removing unused code, the program uses less memory and runs faster because the processor executes fewer instructions.

beginner

Give an example of dead code.

If a variable is assigned a value but never used later, the assignment is dead code. For example:<br>int x = 5; // x is never used

intermediate

Can dead code elimination affect program correctness?

No, dead code elimination only removes code that does not change the program's output or behavior, so it keeps the program correct.

What does dead code elimination do?

A Changes program logic to improve results

B Adds extra code for debugging

C Removes code that never runs or affects output

D Encrypts the program code

Dead code elimination removes code that does not run or affect the program's output.

Which of these is an example of dead code?

A A function called multiple times

B A print statement showing output

C A loop that runs 10 times

D A variable assigned but never used

Assigning a variable that is never used is dead code.

Why do compilers perform dead code elimination?

A To make programs smaller and faster

B To add comments automatically

C To change program results

D To increase program size

Removing dead code reduces program size and improves speed.

Can dead code elimination remove code that changes program output?

A No, it adds extra code instead

B No, it only removes code that does not affect output

C Yes, to fix bugs

D Yes, it changes program logic

Dead code elimination preserves program correctness by only removing unused code.

Which of the following is NOT a benefit of dead code elimination?

A Adds new features

B Reduces program size

C Improves program speed

D Simplifies code

Dead code elimination does not add features; it removes unnecessary code.

Explain what dead code elimination is and why it is important in compilers.

Think about code that never runs or affects the program.

Describe an example of dead code and how a compiler might remove it.

Consider code that assigns a value but never uses it.