It might help to read a bit more closely. A lot of the optimisations being discussed were already added years ago; the point is that they are not as useful in real-world usage as they are in benchmarks (or, in fact, disadvantageous).

JIT compiling a highly dynamic language is quite a different task than AOT compiling a statically typed language. Bit-twiddling tricks are unlikely to be the biggest concern. Try starting with the obvious like https://en.wikipedia.org/wiki/Just-in-time_compilation