The barrel shifter was one of the things I loved about writing assembly code for the ARM. Shift anything, any amount for free! There is a nice writeup about wh

The barrel shifter was one of the things I loved about writing assembly code for the ARM. Shift anything, any amount for free! There is a nice writeup about what it could do for you here: https://www.davespace.co.uk/arm/introduction-to-arm/barrel-shifter.html https://www.davespace.co.uk/arm/introduction-to-arm/barrel-s... Back in the ARM2 days (I never coded for ARM1 - they made very few of them) you knew exactly how long each instruction would take to execute (1 cycle for arithmetic, 4 cycles for load/save single value and 4 cycles + 1 for each location for load/save multiple if I remember correctly). You could use the barrel shifter to shift/rotate arguments as part of those 1 cycle instructions, using up a whole zero extra cycles! Nowadays with superscalar ARMs with branch prediction and onboard caches things aren't nearly so straight forward.