In cljs.analyzer/analyze-form the load-core fn is called. load-core guards against doing its work multiple times. It then always calls (intern-macros 'cljs.core), which also checks whether it was called before. This ends up doing the checks very often. load-core should probably be called in a less frequent manner.

Performance impact is very minimal but I did a quick test in my work project and load-core is called 416671 times there (without cache) when 1 would be enough.