I think you're implicitly thinking that a sensible compiler targeting the JVM would compile whatever functions the source language has to JVM methods and call t

I think you're implicitly thinking that a sensible compiler targeting the JVM would compile whatever functions the source language has to JVM methods and call them via the usual JVM method call instruction. That's certainly a good thing to do if you want have simple Java interop and to reuse the JVM's call logic instead of simulating your own calling convention with other instructions. I was implicitly thinking there's nothing forcing you to use the JVM calling convention. For example your compiler could transform the source to CPS. That probably would generate slow code and interop would be awkward (because normal Java libraries aren't already in CPS).