Given that they are so close in your example, I was thinking that it's possible that both sides are being optimised out, but that since the map side is smaller,

Given that they are so close in your example, I was thinking that it's possible that both sides are being optimised out, but that since the map side is smaller, it runs faster (i.e. the optimisation is at run time and so it still has to interpret the code -- smaller code interprets faster). I haven't had time to revisit this since, but I think it's important. It is also possible that the profiling support in Chromium and Firefox is broken and I would very much like to know that if it is true.