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Optimising compilers do a lot more than drop code with no effect (and TBH most decent linter tools will pick that up for you anyway), I've seen them generate machine code that bore virtually no relationship to the C source, with loop unrolling, function call inlining, operation interleaving etc. etc. https://cacm.acm.org/magazines/2020/2/242347-optimizations-i... has some interesting examples.

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Yup, and that's exactly why we turn the optimizations off and keep them off, even for the shipped release.

Makes sense if safety is a priority over performance and/or concerns over reverse engineering.

For the mostly high-level C code that I write, I find that compiler optimisations give typically give speed-ups in the 1.5x - 3x range. A lot of code is bound by external bottlenecks that would completely mask such a speedup anyway.

For really performance-oriented code you probably want to drop to SIMD first, and play with compiler optimisations second.

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