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> This gets said a lot,

No, this actually doesn't get said a lot, however the simplicity of C compilation semantics is one of its biggest strengths.

> ... but unless you're writing C code for a microcontroller (or a PDP11), that isn't even close to being true.

Do humor us with an example of a C code that compiles into something that is "not even close" to what you'd reasonably expect.



For example: https://godbolt.org/z/m3xSse


How is basic loop unrolling is "not even close" to the expected result when you explicitly ask for optimization with O3?


This isn’t basic loop unrolling; it’s replacing an entire loop with a closed form mathematical formula.


It's a form of loop unrolling. Regardless of the term, this is still very much in the ballpark of what you'd expect when asking for optimization.




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