Compiling LLJS to asm.js

http://jlongster.com/Compiling-LLJS-to-asm.js,-Now-Available-?hn

by jlongster • 13 years ago

101 34 13 years ago

niggler3• 13 years ago

Has anyone built the entire stack in javascript (C to JS compiler in JS + standard library) so that you could write JS applications in C and compile and run in the browser?

EDIT: to clarify, the ideal solution would be an editor (like codemirror or ace) with a compile+run button that would compile the code down to JS and run it.

jevinskie• 13 years ago

https://github.com/kripken/emscripten/wiki

niggler3• 13 years ago

That's LLVM -> JS. Has anyone built Clang using emscripten (that would be the C -> LLVM piece)?

jlongster5• 13 years ago

That's exactly what emscripten does, and is very mature and being used to port massive 3d games to the web.

https://github.com/kripken/emscripten

See the BananaBread demo: https://developer.mozilla.org/en-US/demos/detail/bananabread

niggler3• 13 years ago

You have to use the command-line `emcc` tool to do this. I'm asking if that tool can be eliminated from the workflow.

The ideal solution would be an editor (like codemirror or ace) with a compile+run button that would compile the code down to JS and run it.

ihsw• 13 years ago

I think what the parent was asking was could libraries be written in C (for example jQuery) where performance is critical.

kayoone3• 13 years ago

Whats the use for LLJS ? I dont really get it. So its not meant to be used in web development but for things like games or complete VMs. But isnt it much simpler for those cases to compile existing C codebases with emscripten instead of rewriting everything in LLJS ? Even if you start today with writing a new game engine, wouldnt it make more sense to use C++ and be able to target any platform there is instead of just the browser?

jlongster5• 13 years ago

The main use for something like LLJS is to allow you to target asm.js with new code that you write. It's true that it's probably not the best idea to completely rewrite a 3d engine in it (right now), but it gives you a quick way to rewrite core parts of an intensive app (like a 3d game) for high performance. There are "inner loops" that could benefit from a small amount of LLJS.

As the post says, it's a proof of concept and a way to open up asm.js to people who want to tinker with it without compiling C code with emscripten.

kayoone3• 13 years ago

I see, so the main benefit vs compiling c to asm.js is that the development process is easier because you dont need to manually compile. Sounds interesting to use as a scripting language inside a c based game engine. So the core of the engine would be directly compiled to asm.js while the game logic scripting could be done in LLJS to be able to live-test your game.

azakai3• 13 years ago

For a big codebase, yes, compiling C/C++ using emscripten or such is a good idea. But if you want to write a tiny part of a normal JS application in something faster, lljs is convenient. Sort of like you would write inline assembly in C perhaps.

STRML• 13 years ago

LLJS, asm.js, & Emscripten are really moving Javascript forward at incredible speed. I wonder if these projects will affect the future of the JS spec (ECMAScript Harmony + above). It's an exciting time to be a web programmer.

samth• 13 years ago

These projects are already affecting the spec. Here's a very small example: https://mail.mozilla.org/pipermail/es-discuss/2012-November/... which is used in asm.js and already implemented in Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=808148

ahoge• 13 years ago

This was added to Gecko 20.0, but it isn't part of the specs.

V8 doesn't support it: http://code.google.com/p/v8/issues/detail?id=2455

NinjaWarrior• 13 years ago

Math.imul is just an ad-hoc patch to improve the performance of Emscripten. It's totally for Firefox. Is there a motivation to standardize and implement such a thing for other browser vendors? I'll star the V8 issue though...

abecedarius4• 13 years ago

Yesterday I rewrote a tiny Javascript demo in asm.js and also saw an order-of-magnitude speedup. (I thought at first it didn't help at all, apparently because the framerate was limited by setInterval().)

Code at http://wry.me/hacking/canvas_asm.html

simcop2387• 13 years ago

Doesn't appear to be doing anything for me,

    noasm 285
    asm 13
    asm 13
    noasm 269

That's all that appears in the console. Network and everything looks fine, no 404 or other errors.

abecedarius4• 13 years ago

Yes, I disabled display so that wouldn't get into the benchmark. The numbers are times in milliseconds.

Groxx2• 13 years ago

I wonder if most / all of that speedup is just using typed arrays (edit: nvm, they both do). I get similar speeds in Chrome, which afaik doesn't have any special handling for `"use asm";` functions.

srijs3• 13 years ago

Cool. I recently wrote a low-level sha1 implementation in pure javascript, trying to leverage asm.js (http://github.com/srijs/rusha).

Can you tell me, how did you confirm you wrote valid asm.js and there was no fallback-mechanism kicking in?

I benchmarked my implementation, of course, and noticed a 2x speedup. However, this seems quite less for the this type of low-level algorithm...

abecedarius4• 13 years ago

Open the error console (via the Web Developer menu item) and you'll see messages there. Success shows up as "Error: successfully compiled asm.js code." :-)

P.S. Looking at your code, I can tell it's not asm.js conformant yet, though it should just be a bunch of small tweaks (e.g. an expression like (a+b) will need to be (a+b)|0, etc.).

gruseom2• 13 years ago

That is the most exciting news I've heard in quite a while.

y0ghur7_xxx• 13 years ago

I am sure there is some reason this can't be done, but can we compile JavaScript to asm.js? If this can be done with C, it can be done with JS?

jlongster5• 13 years ago

Sure, but it's different because you need to compile a whole VM to asm.js and run javascript inside of it. You can't compile a dynamic language like javascript to low-level code because you need too much information at runtime.

See this project, which compiles SpiderMonkey to javascript via emscripten, which supports asm.js: https://github.com/jterrace/js.js/

azakai3• 13 years ago

qt-emscripten does something similar, it builds the JSC interpreter together with Qt.

gruseom2• 13 years ago

How far are we from being able to do meaningful text processing with typed arrays and (therefore, presumably) asm.js? Last I checked, there was work being done on a string encoding/decoding standard but it wasn't implemented in browsers yet. Can anyone say more about this?

Compiling LLJS to asm.js

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