[moregrist]

A byte code interpreter is, very approximately, a lookup table of byte code instructions that dispatches each instruction to highly optimized assembly.

This will almost certainly outperform a straight translation to poorly optimized machine code.

Compilers are structured in conceptual (and sometimes distinct) layers. In a classic statically-typed language will only compile-time optimizations, the compiler front-end will parse the language into a abstract syntax tree (AST) via a parse tree or directly, and then convert the AST into the first of what may be several intermediate representations (IRs). This is where a lot of optimization is done.

Finally the last IR is lowered to assembly, which includes register allocation and some other (peephole) optimization techniques. This is separate from the IT manipulation so you don’t have to write separate optimizers for different architectures.

There are aspects of a tracing JIT compiler that are quite different, but it will still use IR layers to optimize and have architecture-dependent layers for generating machine code.

[taeric]

Right, I guess my main surprise is that the PyPy byte code interpreter is as fast as it is. My understanding is obviously outdated on how it is implemented; but I thought its claim to fame was that it was purely written in python. I'm assuming the subset of python it is implemented in is fairly restricted? That or my understanding was wrong in other ways. :D

[pjmlp]

Yes, it is called RPython,

https://rpython.readthedocs.io/en/latest/getting-started.htm...