Modern compilers are extremely powerful tools that have built-in optimization logic far outpacing the abilities of ordinary programmers. They are intimately familiar with the internal states of the processor at any given time and can optimize register usage, cache pipelines, core states, and performance bottlenecks better than most of us mere mortals.

Also, remember that your job is not to try and outsmart the compiler. Your job is to ensure you get the implementation right. The compiler’s jo...