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Compare -O0 vs -O1 vs -O2 vs -O3 Assembly Output

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Implementation

Compare compiler optimization levels by examining assembly output.

Requirements:

Implement simple functions (fibonacci, factorial, sum array)
Compile with -O0, -O1, -O2, -O3
Use objdump or gcc -S to examine assembly
Count instructions for each optimization level
Measure execution time for each level
Show code size differences
Print comparison and analysis
Explain which optimizations were applied
Demonstrate debugging difficulty at -O2/-O3
Use Compiler Explorer (godbolt.org) for visualization

Why This Matters

The Linux kernel build famously avoids -O3 in favor of -O2 precisely because of the code-bloat-versus-speed tradeoff this task explores, and Compiler Explorer (godbolt.org) exists as a dedicated tool purely because engineers need to see this -O0 vs -O2 assembly diff constantly. Debugging teams routinely rebuild with -O0 specifically to get GDB and Valgrind's line-level accuracy back after a bug only reproduces at -O2, which is exactly the debugging-versus-performance tension covered here.

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