Instruction scheduling in Compiler Design - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary goal of instruction scheduling in compilers?

Instruction scheduling is a technique used by compilers. What is its main purpose?

A To translate high-level code into machine code

B To reorder instructions to reduce pipeline stalls and improve CPU performance

C To allocate memory for variables during program execution

D To optimize the size of the compiled binary file

💡 Hint

Think about how CPUs execute instructions and what can slow them down.

Instruction scheduling rearranges instructions to avoid delays caused by data hazards or resource conflicts, improving CPU pipeline efficiency.

📋 Factual

intermediate

Which hazard does instruction scheduling primarily aim to mitigate?

Instruction scheduling helps reduce which type of hazard in CPU pipelines?

A Structural hazard

B Thermal hazard

C Data hazard

D Control hazard

💡 Hint

Consider hazards caused by dependencies between instructions.

Instruction scheduling mainly targets data hazards, which occur when instructions depend on the results of previous instructions.

🔍 Analysis

advanced

Analyze the effect of instruction scheduling on a sequence with dependent instructions

Given a sequence of instructions where each depends on the previous one, how does instruction scheduling improve performance?

A It duplicates instructions to speed up execution

B It removes dependencies to allow parallel execution

C It delays all instructions to avoid hazards

D It can reorder independent instructions between dependent ones to fill pipeline slots and reduce stalls

💡 Hint

Think about how independent instructions can be used to avoid waiting times.

Instruction scheduling rearranges instructions so independent ones execute while waiting for dependent results, reducing idle CPU cycles.

❓ Comparison

advanced

Compare static and dynamic instruction scheduling

Which statement correctly distinguishes static instruction scheduling from dynamic instruction scheduling?

A Static scheduling is done by the compiler before execution; dynamic scheduling is done by hardware during execution

B Static scheduling happens at runtime; dynamic scheduling happens at compile time

C Static scheduling requires no knowledge of instruction dependencies; dynamic scheduling does

D Static scheduling is slower than dynamic scheduling

💡 Hint

Consider when and where the scheduling decisions are made.

Static scheduling is performed by the compiler before the program runs, while dynamic scheduling is handled by the CPU hardware during execution.

❓ Reasoning

expert

What is the impact of instruction scheduling on out-of-order execution?

How does instruction scheduling relate to out-of-order execution in modern CPUs?

A Instruction scheduling by the compiler complements out-of-order execution by reducing hazards before runtime

B Instruction scheduling replaces the need for out-of-order execution entirely

C Instruction scheduling conflicts with out-of-order execution and reduces CPU efficiency

D Instruction scheduling only applies to single-core processors and is unrelated to out-of-order execution

💡 Hint

Think about how compiler and hardware optimizations work together.

Compiler instruction scheduling helps reduce hazards early, making out-of-order execution more efficient by lowering runtime conflicts.