[kevincox]

The high-level view is that adding code that never gets executed causes the compiler to emit code that the CPU predicts better. IDK if this is the compiler assuming that the `print()` call is cold or the branch predictor getting luckier by chance but basically this tickles the CPU in the right way to get better performance.

It seems that this is mostly luck in a strange situation. And of course if you ever hit the `print()` it will be way slower than not. You can probably do better by adding something like a `__builtin_expect(...)` intrinsic in the right place to be more explicit about what the goal is here.