Comment by alain94040

On modern cpus? Most likely. Those kinds of optimizations are done by the core with no compiler magic needed.

CPU implementation has become too complex to grasp. The only sure way to know how a CPU will behave for a given workload is to run the workload. It's good to have some basic expectations of performance, instructions/cycle, memory bandwidth, to detect if something is off. I guess I'm trying to say it's hard to keep in your head all the details of what ~1B transistors are doing together to run your code. It's just too big.