[kergonath]

> Complex compiler doing crazy optimizations, in my opinion, is not worth it.

For these optimisations that are in the back-end, they are used for other languages that can be higher-level or that cannot drop to assembler as easily. C is just one of the front-ends of modern compiler suites.

[ziml77]

Some of them even give you access to this stuff. C# has Vector<T> which picks implementations of various operations based on the current CPU's capabilities. But they also let you have complete control if you want by providing functions in the System.Runtime.Instrinsics namespace.