Julia does very little tracing, except to infer types, which it then passes on to LLVM. All the optimizations in Julia are because Julia stresses type stabilit

Julia does very little tracing, except to infer types, which it then passes on to LLVM. All the optimizations in Julia are because Julia stresses type stability, and once types are known, LLVM can generate very good code specific for those types. You can easily annotate functions with types in Julia, and pre-compile specialized functions. Julia does very little runtime magic to speed up code, especially compared to PyPy. The speed just comes from a very clever type system + LLVM.