> and adding a single line of code can completely change the way your program is compiled without you even noticing You cannot work on SIMD micro-optimization

> and adding a single line of code can completely change the way your program is compiled without you even noticing You cannot work on SIMD micro-optimizations without assessing the final compiler codegen. Compilers will easily cancel your optimizations effort once you move your code from an isolated test-case to an actual binary that is being released. Otherwise profilers don't really help much if you don't know what are you looking for. And to know what to look for you really need to understand how the CPU internals work. There's no way around it. May you switch to another CPU and you will find that your optimization scales differently.