I don't see that making a difference in the by-copy/by-reference use on the leaf functions? Since the copies are stack allocated all the data used there is go

I don't see that making a difference in the by-copy/by-reference use on the leaf functions? Since the copies are stack allocated all the data used there is going to be shuffling in and out of the same few cache lines and shouldn't make a perceptible difference in overall cache usage.