Well, it is necessary to expose this to language implementations to reach good performance. If we could reach the same performance otherwise, we would not expos

Well, it is necessary to expose this to language implementations to reach good performance. If we could reach the same performance otherwise, we would not expose it, as it makes implementing Truffle languages more complicated. Unfortunately automating the specializing part is an unsolved research question for a method based compiler (deserves its own PhD). Other trace based meta-compilation approaches (e.g. PyPy) have an advantage here, but disadvantages in other areas.