It's been useful to me in one very specific place so far: to remove a range-check in front of the jump-table lookup in a big switch-case statement. For 'very ho

It's been useful to me in one very specific place so far: to remove a range-check in front of the jump-table lookup in a big switch-case statement. For 'very hot' code paths like in the instruction decoder of an emulator or interpreting byte-code VM this might actually translate to a measurable difference. In debug mode it makes a lot of sense to replace the __builtin_unreachable with an abort() though.