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The yk project enables automatic JIT compilation of existing C interpreters by applying meta-tracing at the LLVM IR level. By modifying only ~400 lines of code in PUC Lua, the team created yklua — a JIT-enabled fork that achieves roughly 2x geometric mean speedup over the reference interpreter. The approach uses a custom LLVM fork (ykllvm) that instruments basic blocks, serializes IR, and handles deoptimization via extended stackmaps and a shadow stack. Key optimization primitives exposed to interpreter authors include yk_promote (burning runtime values into traces as constants), yk_idempotent (marking pure-ish functions for call elimination), and yk_unroll (inlining loops). Code generation runs in reverse order (inspired by LuaJIT) for simpler register allocation and implicit dead code elimination. Unlike RPython or Truffle, yk works directly on existing C interpreters without requiring a rewrite, preserving full compatibility with the reference implementation. The system is alpha-stage, x64-only, and not yet production-ready, but already shows meaningful results on Lua and MicroPython.

Laurence Tratt: Retrofitting JIT Compilers into C Interpreters

Deriving a JIT compiler from C interpreters

From a C interpreter to a meta-tracing interpreter