How do JIT compilers work?

01 Tem 04:47

JIT compilers are actually a pretty clever way to combine the performance benefits of running compiled code with the flexibility of interpreted code. They typically kick in at runtime, as the code is executing, identifying and optimizing the most frequently used paths (hot paths). A great example is V8's Ignition + TurboFan duo in JavaScript—they start with simple code generation, then eliminate asymmetric branches, apply inline caching, and even optimize register allocation, achieving significant performance gains. I've seen a similar optimization on the JS side when dealing with delegate functions in a massive React project. When function objects were being recreated constantly during component re-renders, dragging performance down, I used the `useCallback` hook to maintain stable references. In a way, the JIT compiler does something similar by inlining function calls and reducing branching to optimize the process.