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Researchers and practitioners are exploring practical ways to add JIT compilation to existing C-based interpreters without full rewrites. Laurence Tratt’s yk prototype demonstrates that modest code changes—hundreds of lines added, few altered—can retrofit JITs into interpreters like PUC Lua, delivering up to 4× speedups on some workloads and roughly 2× on average. Coverage varies by interpreter idioms, and retrofitted JITs don’t yet match hand-tuned engines like LuaJIT. Discussion centers on techniques (tracing, on-stack replacement, dynamic codegen), trade-offs in portability, debugging, and maintenance, and the promise of lowering the barrier to JIT-enable many legacy and embedded runtimes.
Retrofitting JIT into existing C interpreters can boost runtime performance without full rewrites, lowering migration cost and risk for language runtimes and embedded scripting engines. Tech professionals maintaining interpreters or embedding languages can use these techniques to get significant speedups with minimal code changes.
Dossier last updated: 2026-05-12 16:24:28
&#32; submitted by &#32; <a href="https://www.reddit.com/user/ltratt"> /u/ltratt </a> <br/> <span><a href="https://tratt.net/laurie/blog/2026/retrofitting_jit_compilers_into_c_interpreters.html">[link]</a></span> &#32; <span><a href="https://www.reddit.com/r/programming/comments/1sm4eof/retrofitting_jit_compilers_into_c_interpreters/">[comments]</a></span>
Laurence Tratt describes yk, an alpha-stage system that can retrofit JIT compilation into existing C-based language interpreters with minimal code changes. Using yk, the author transformed PUC Lua into yklua by adding ~400 lines and changing <50 lines, yielding up to ~4x speedups on selected demos and an average near 2x on a Lua benchmark suite—while remaining compatible with the reference implementation. yk has also been tested on MicroPython (ykmicropython) with mixed results due to unsupported interpreter idioms. Tratt emphasizes yk’s trade-off: it won’t match hand-optimized JITs like LuaJIT but enables easier, maintenance-friendly JITing for interpreters, aiming to lower the barrier for adding JITs to many C interpreters.
An article titled “Retrofitting JIT Compilers into C Interpreters” indicates a focus on adding just-in-time (JIT) compilation capabilities to existing C-based language interpreters. Based on the title alone, it likely discusses techniques for integrating a JIT into an interpreter architecture, such as identifying hot code paths, generating machine code at runtime, and managing execution transitions between interpreted and compiled code. The topic matters because JIT retrofits can improve performance without rewriting an interpreter as a full compiler, but they also introduce complexity around portability, security, debugging, and runtime memory management. No further details, dates, implementations, benchmarks, or specific projects are available because the article body was not provided.
A recent Hacker News post links to a blog by ltratt detailing techniques for adding Just-In-Time (JIT) compilation to existing C interpreters. The piece explains practical strategies for retrofitting JITs—including tracing, on-stack replacement, and code generation approaches—into interpreter architectures without rewriting them from scratch. Key players include the author (ltratt) and the broader systems programming community on Hacker News, with discussions highlighting the intellectual rigor and niche expertise required. This matters because enabling JITs in legacy C interpreters can yield major performance gains for language runtimes and embedded scripting environments, extending hardware efficiency and developer toolchains while avoiding full rewrites.