As of r195562, WebKit’s FTL JIT (Faster Than Light Just In Time compiler) now uses a new backend on OS X. The Bare Bones Backend, or B3 for short, replaces LLVM as the low-level optimizer in the FTL JIT. While LLVM is an excellent optimizer, it isn’t specifically designed for the optimization challenges of dynamic languages like JavaScript. We felt that we could get a bigger speed-up if we combine