@kenshirriff A barrel shifter was the first thing we had to design in our silicon design class back in the early 1990s.

While doing that, my own home computer was running a very much simpler chip (an early ARM). You can see the barrel shifter and ALU in the ARM1 in the link below. Mine was running an ARM 2 initially (and latterly was upgraded to an ARM 3), but very similar to this design.

https://hackaday.com/2015/12/21/reverse-engineering-the-arm-alu/