There are two separate issues here. Can an x86 be made nearly as efficient as an ARM chip with unbounded effort? Sure. But it's a lot easier to make a compet

There are two separate issues here. Can an x86 be made nearly as efficient as an ARM chip with unbounded effort? Sure. But it's a lot easier to make a competent ARM design than a competent x86 design because there's so much more to the later and the front end has to be a lot more complicated to deal with the unsynchronized encoding.