This is a case of knowing the rules so well that you know when you can break them.

Its also a historical artifact from the days when many programmers wrote assembly yet compilers started getting good.

There’s also an element of avoiding premature optimization: don’t assume the compiler will product slower code or that if it does it will matter in your specific application.

At the very least you should give the compiler a chance, profile, then hand-tune after you’ve fixed all the low-hanging fruit.