Multiplication typically takes 3 cycles, so a total of 1+3+1=5 cycles of latency. A load from L1 takes 4-5 cycles on non-ancient x86 and Apple M1. So roughly on

Multiplication typically takes 3 cycles, so a total of 1+3+1=5 cycles of latency. A load from L1 takes 4-5 cycles on non-ancient x86 and Apple M1. So roughly on-par, perhaps a bit faster, at the cost of eating some ILP in the odd case that there's not still plenty left (also better if not already in-cache, though only significantly so if using that instead of the lzcnt directly as the threshold table index).