Building a good VM for a dynamic language takes a ton of engineering. The best-performing VMs (e.g., JavaScriptCore, V8, SpiderMonkey) employ at least 3 VM tiers (interpreter, baseline JIT[1] and optimizing JIT), and pervasively use hand-coded assembly in every VM tier[2]. Optimizations such as inline caching and type speculation are required to get high performance, but they require high expertise and introduce additional engineering complexity. Deegen is my research meta-compiler to make high-...