"I don't know anything about your work Lisp compiler, but making code written in a dynamically typed language run as fast as code written in a statically typed

"I don't know anything about your work Lisp compiler, but making code written in a dynamically typed language run as fast as code written in a statically typed language - outside of microbenchmarks - generally requires making a lot of assumptions about that code." Lisp supports a system of type "hints" to deal with that issue; with SBCL, those hints can be treated as assertions or can be assumed true, depending on compiler options (the "safety level"). A common suggestion for optimizing Lisp code is to use type hints, and the difference is usually pretty significant. You even get some amount of static type checking from this, in the form of warnings about declared types not matching inferred types. It's not as powerful as the ML type system, but it usually gives you what you need in terms of optimizing code.