[chii]

> not worry about optimising the stuff that happens under the hood.

no one is asking you to do this optimization all the time. But you need to know what and how, if you were to be tasked. Then as you get more senior, you will have to also be able to judge whether it is possible, or worth the effort to devote to the optimization, should a scenario arises.

> second guess the compiler.

you aint second guessing it, you're examining the output, and understanding it. Then potentially recognizing when or if the compiler is outputting bad stuff. That's not second guessing.