Sure, none of that is in doubt. But in my experience the performance cost of hot code getting deopted is so massive as to overwhelm virtually any other factor,

Sure, none of that is in doubt. But in my experience the performance cost of hot code getting deopted is so massive as to overwhelm virtually any other factor, so realistically, fixing the deopt is what solved TFA's problem. Of course getting rid of the switch statements was presumably an additional speedup, but since TFA doesn't compare those cases I guess that's neither here nor there.