luajit-remake VS LuaJIT

It's really cool that Haoran Xu copy-and-patch technique is catching on, I remember discovering it through his blog posts on applying these techniques to his own LuaJIT remake project[0][1] (and I probably found those through a post here). I highly recommend them if you're into that sort of thing, BTW. They're incredible deep dives, but he uses the details-element to keep the metaphorical descents into Mariana Trench optional so it doesn't get too overwhelming.

I even had the privilege of congratulating him the 1000th star of the GH repo[2], where he reassured me and others that he's still working on it despite the long pause after the last blog post, and that this mainly has to do with behind-the-scenes rewrites that make no sense to publish in part.

[0] https://sillycross.github.io/2022/11/22/2022-11-22/

[1] https://sillycross.github.io/2023/05/12/2023-05-12/

[2] https://github.com/luajit-remake/luajit-remake/issues/11

This seems like an awesome way of writing faster interpreters – i.e. not in assembly, but in C++ snippets you stitch together with a tool.

I did peek at the deegen tool a bit, and it seems quite large? https://github.com/luajit-remake/luajit-remake/tree/master/d...

I would be interested in an overview of all the analysis it has to do, which as I understand is basically “automated Mike Pall”

FWIW I think this is the hand-written equivalent with LuaJIT’s dynasm tool: https://github.com/LuaJIT/LuaJIT/blob/v2.1/src/vm_x64.dasc (just under 5000 lines)

Also there are several of these files with no apparent sharing, as you would get with deegen:

https://github.com/LuaJIT/LuaJIT/blob/v2.1/src/vm_x86.dasc

https://github.com/LuaJIT/LuaJIT/blob/v2.1/src/vm_ppc.dasc

Unfortunately things aren't so simple, as when doing JIT compilation, LuaJIT _will_ try to shorten the lifetimes of local variables. Using the latest available version of LuaJIT (https://github.com/LuaJIT/LuaJIT/commit/0d313b243194a0b8d239...), the following reliably fails for me:

  local ffi = require"ffi"

I am using https://luajit.org/ in my GCC C++ project.

Can I use this faster Lua JIT in my project as a replacement? And if so, how so?

The existing luajit doesn't do v5.1, so it would be nice to use this newer engine at the newer baseline lua version level.

The commit history looks pretty active...

https://github.com/LuaJIT/LuaJIT/commits/v2.1/

I think https://github.com/LuaJIT/LuaJIT/commit/6a2163a6b45d6d251599... improved things a bit, notably making automatic tarballs work again.

There is nothing on luajit.org, so I assume that 2.0 doesn't have the extensions added (think the site is still on 2.0). However I found some proof in the mirrored git repo, that they do exist and also my luajit interpreter (2.1.0-beta3) shows them as builtins.

If you absolutely want a performant scripting runtime, I'd recommend taking a look at LuaJit, DaScript or AngelScript.

If you don't like that - look towards JIT-compilers. Lua has one