The Bare Bones Backend, or B3 for short, is WebKit's optimizing JIT for procedures containing C-like code. It's currently used as the default backend for the FTL JIT inside JavaScriptCore. B3 comprises a C-like SSA IR known as "B3 IR", optimizations on B3 IR, an assembly IR known as "Air", optimizations on Air, an instruction selector that turns B3 IR into Air, and a code generator that assembles