  Language implementation frameworks, e.g., RPython and Truffle/Graal, are
practical tools for creating efficient virtual machines, including a
well-functioning just-in-time (JIT) compiler. It is demanding to support
multitier JIT compilation in such a framework for language developers. This
paper presents an idea to generate threaded code by reusing an existing
meta-tracing JIT compiler, as well as an interpreter design for it. Our
approach does not largely modify RPython itself but constructs an effective
interpreter definition to enable threaded code generation in RPython. We expect
our system to be extended to support multilevel JIT compilation in the RPython
framework. We measured the potential performance of our threaded code
generation by simulating its behavior in PyPy. We confirmed that our approach
reduced code sizes by 80 \% and compilation times by 60 \% compared to PyPy's
JIT compiler on average, and ran about 7 \% faster than the interpreter-only
execution.
