[lukefleed]

BEXTR basically does the same thing, yes. I'm sticking with the portable shift-and-mask, though. My bet is that LLVM is smart enough to see that pattern and emit a BEXTR on its own when the target supports BMI1.

Using the intrinsic directly would also kill portability. I'd need #[cfg] for ARM and runtime checks for older x86 CPUs, which adds complexity for a tiny, if any, gain. The current code just lets the compiler pick the best instruction on any architecture.