The video explores how modern compiler optimizations can significantly enhance code performance without rewriting. It demonstrates this using the Fast Fourier Transform (FFT) and discusses various GCC optimization levels, including O1, O2, O3, and O Fast. While O Fast can boost performance, it may alter code behavior, especially with floating-point operations. The video concludes by highlighting the importance of benchmarking and previews the next topic on CPU design's impact on code performance.

What should programmers consider when choosing optimization levels for their code?

Describe how floating point optimizations can affect program behavior.

Summarize the main points discussed in the video regarding compiler optimizations.