Great explanation of why a branchless approach results in such a speed up. I've never really had to deal with performance optimization at this level. Generally it's probably best not to get too involved letting the CPU black box do its thing.
I do wonder, would the performance characteristics of branchless vs branching be consistent across different CPUs/architectures? If you had a CPU that wasn't trying to be fancy with branch prediction, would the regular algo be faster?
Thanks for sharing, optimisations like these are what keeps the fun in programming. I have been optimising my JSONLogic evaluator in rust and used arena allocator and preallocation tricks that gave me good jump in tuning. Let me see if branchless programming techniques can get any further in my case
I do wonder, would the performance characteristics of branchless vs branching be consistent across different CPUs/architectures? If you had a CPU that wasn't trying to be fancy with branch prediction, would the regular algo be faster?