Curry On
July 15-16th, 2019

A compact bytecode format for JavaScriptCore
Tadeu Zagallo


JavaScriptCore (JSC) is the multi-tiered JavaScript virtual machine in WebKit. The bytecode is a central piece in JSC: it’s executed by the interpreter and the source of truth for all of JSC’s compilers. In this talk we’ll look at the recent redesign of our bytecode format, which cut its size in half and enabled persisting the bytecode on disk without impacting the overall performance of the system.


I’m a Software Engineer at Apple, working on JavaScriptCore. I like to spend my spare time studying about programming languages, type systems and virtual machines.