Consider making use of efficient implementations of popcount, ctz and clz if they become available.

[modulovalue]

For reference: dart-lang/sdk#52673

[modulovalue]

Here's a blogpost that discusses how to use ctz to implement efficient iteration: https://lemire.me/blog/2018/03/08/iterating-over-set-bits-quickly-simd-edition/

[isoos]

Feel free to open a PR once it is available, I'm happy to take such changes.