fix: optimize using constexpr and templates

[GermanAizek]

@variar,
I'm not sure of course, but maybe you're interested in rewriting some parameters of functions to create guaranteed C++17 metafunctions that are more optimized due to constant conditions and variables.
I doubt that the functions I fixed have a big impact on performance, but this is a step towards using such a method for functions that are frequently called.

More info here: https://stackoverflow.com/a/57211067
My tests on godbolt here: https://godbolt.org/z/4qq9n38Tz

[variar]

As far as I understand, this removes a branch from code path at the expense of compiling separate versions of the function for different conditions. The approach might be useful. However, I'd apply it only for hot-path and after doing some measurements that justify increase in complexity/compilation time.

[GermanAizek]

@variar, should I run benchmark using std::chrono?

[GermanAizek]

@variar, is this pull request still relevant?