Ah, good point, I missed that my version became a tail call, good catch. Still, a C function call is pushing a couple of values onto the stack then performing a

Ah, good point, I missed that my version became a tail call, good catch. Still, a C function call is pushing a couple of values onto the stack then performing an unconditional jump, so it's not much worse. That site is indeed very neat! It just uses Google Benchmark in the background, but it's excellent for these kinds of discussions (and lovely to have it link directly to godbolt if you want). It's a shame that it doesn't give you the actual latency numbers like regular Google Benchmark, but I suppose that is to be expected when you're running in server VMs, those numbers aren't necessarily meaningful.