Hello, JIT World: The Joy of Simple JITs (2012) | Hacker News Reader

Hello, JIT World: The Joy of Simple JITs (2012)

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I remember a decade ago there were awesome blog posts about programming languages all the time... Andy Wingo talking about Scheme, Ola Bini talking about Iota, Steve Dekorte about Io, Slava Pestov on Factor, _why had potion, Ruby was "fresh", and Steve Yegge writing long posts about languages as well...

I hate twitter..

Wingo is Still at it, and recently there has been a flow of interesting JIT posts since guile 3.0 will have a JIT.

I played with JITs in Nim recently I found it quite enjoyable.

Here is my mandatory Brainfuck VM[1] and this is my opcode tables and probably what I like best about Nim metaprogramming[2]

[1]: https://github.com/numforge/laser/blob/9fbb8d2a/examples/ex0...

[2]: https://github.com/numforge/laser/blob/9fbb8d2a/laser/photon...

For rustaceans out there who are interested, check out https://github.com/CensoredUsername/dynasm-rs as a nice rust replacement for dynasm.

I submitted a bunch of stream of consciousness JIT and related posts today, if this interests you, check out these too:

Basic JIT: https://news.ycombinator.com/item?id=18708410 (even simpler version of the above post)

Cult of the Bound Variable: https://news.ycombinator.com/item?id=18708366 (just pure insanity [pdf])

Do you know of anything that goes over tracing JIT?

Nope. Not yet.

Tangentially, here is one way to think about how tracing JIT works:

1. Set a breakpoint at the start of a loop that you want to compile.

2. Single-step one iteration of the loop, stepping down into every function call, logging everything that the code does.

3. Compile the log into native code.

Now any time you need to run this loop again, in the same way, you just branch to the generated code to efficiently "replay" the log of how it ran before.

The rest, as they say, is details...

Not sure if you were thinking specifically of blog-posts, but there's a research paper on converting Java HotSpot's 'client' JIT to tracing. (Apparently they managed it!) It gives a description of what 'tracing JIT' means. Perhaps not as approachable as a blog post but it's not too bad.

http://www.ssw.jku.at/Research/Papers/Haeubl11/ (There's a link to the PDF at the bottom which seems to sometimes bypass the ACM paywall, for whatever reason.)

& on a bit of a tangent, Cranelift now builds on stable Rust if you want to write your JIT in not-C

https://github.com/CraneStation/simplejit-demo

Cranelift hopes to become the WASM JIT for Firefox & the debug-mode compiler for rustc

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