There is already an LLVM backend in WebKit. I think the whole intention of the Bare Bones Backend is that it isn&#x27;t LLVM. I can&#x27;t find the link now, but I believe there are some design documents behind this where they critique the performance and output of LLVM, so they&#x27;re trying something new.<p>LLVM does seem to struggle to support dynamic languages like JS well. For example Unladen Swallow (Python) and Rubinius (Ruby) were both commercially-backed efforts to use LLVM and neither achieved much performance.