> This has to be done at a granularity coarse enough that the function call overhead doesn't kill the performance. It has to be entire loops, for example, not

> This has to be done at a granularity coarse enough that the function call overhead doesn't kill the performance. It has to be entire loops, for example, not just some primitive operation like a dot product. Yes, You are right! I understood, that they wanted to add the branch to _every_ SIMD instruction. I concur with branching outside of loops. Re Rust: I expect that one could use a macro around the function (or annotate it, if the macro system is good enough) that generates these different functions and branches to the right one.