Reusable inline caching for JavaScript performance

JavaScript performance is paramount to a user’s browsing experience. Browser vendors have gone to great lengths to improve JavaScript’s steady-state performance. This has led to sophisticated web applications. However, as users increasingly expect instantaneous page load times, another important goal for JavaScript engines is to attain minimal startup times. In this paper, we reduce the startup time of JavaScript programs by enhancing the reuse of compilation and optimization information across different executions. Specifically, we propose a new scheme to increase the startup performance of Inline Caching (IC), a key optimization for dynamic type systems. The idea is to represent a substantial portion of the IC information in an execution in a context-independent way, and reuse it in subsequent executions. We call our enhanced IC design Reusable Inline Caching (RIC). We integrate RIC into the state-of-the-art Google V8 JavaScript engine and measure its impact on the initialization time of popular JavaScript libraries. By recycling IC information collected from a previous execution, RIC reduces the average initialization time per library by 17%.