Examining generated C code, it works mostly well, but it does not provide optimal performance because not all class references and non of method and field IDs are cached.

All of these are invariants, hence should be loaded in cache_class_references(), so that the individual setter methods do not look them up, but rather reference cached value.

Implementing this caching will trim down the upcalls to JVM by at least a half, producing significantly more performant code.