Simple diet tricks for asm.js

http://floooh.github.io/2016/08/27/asmjs-diet.html

by ingve • 10 years ago

53 26 10 years ago

floooh.github.io

_RPM3• 10 years ago

nit: the C style example, should use /* These kind of comments */ not // these kind of comments.

steveklabnik• 10 years ago

C99 supports //.

_RPM3• 10 years ago

C89 standard does not.

rbran• 10 years ago

asm.js really seem to be a good solution, I hope some day it will be used to do more than web games. But at the same time, the vision of the future of compiling everything in javascript is pretty scary.

nawitus2• 10 years ago

I think WebAssembly will replace asm.js soon.

hackcasual5• 10 years ago

Think of WebAssembly as a binary encoding of asm.js. You'll be able to deliver the same program in either format. Asm.js will still be around to support older browsers.

Exuma• 10 years ago

Can someone ELI5 what asm.js is? I've tried Googling it multiple times now and every time I basically give up because I can't relate to anything it's talking about when all they use is buzzwords.

kevinwang• 10 years ago

A language which is a strict subset of JavaScript. The purpose is to write compilers from C to asm.js, which then allows you to write C code and it compiles to something that can run on the browser

teamhappy• 10 years ago

... and that strict subset of JS can be compiled into very efficient native code.

Saltor• 10 years ago

This (funny and accessible, don't worry) talk by Gary Bernhardt is what helped me understand asm.js for the first time: https://www.destroyallsoftware.com/talks/the-birth-and-death...

hackcasual5• 10 years ago

The ELIMINATE_DUPLICATE_FUNCTIONS support was contributed by Tableau Software, by the team I'm on. It's quite expensive processing wise, but is worth a shot seeing if your code base benefits from it. Our usecase leverages a lot of shared pointer based templated classes, which tends to create a lot of delete functions that boil down to free(this);

2 other points I'd add to this overall:

1) Can't emphasize enough how bad exception support is for size, expect in the neighborhood of 30% size increase. This is due to needing to handle all of the possible ways functions can return. Even with exception support disabled, you can still throw them, you just can't catch them in C++ land.

2) goto's. There's a few good reasons to use these, especially in code that needs to make sure cleanup code always runs. Emscripten supports that with a couple different code constructs, pretty much all of which cause a significant amount of bloat. We've saved ~100k in some cases by specifically targeting some 3rd party code that made use of them and rewritting them to not have gotos.

vmorgulis2• 10 years ago

Even with exception support disabled, you can still throw them, you just can't catch them in C++ land.

Is something printed in the console under emscripten if an exception is thrown?

hackcasual5• 10 years ago

It gets converted into a Javascript exception, which will at least give you the Emscripten converted function it was thrown in.

jakub_h3• 10 years ago

Those recommendations together almost sound like "write C in C++".

TazeTSchnitzel• 10 years ago

A lot of C++ coding styles do something like that. I guess because C++ is so large.

olig15• 10 years ago

"The emscripten version is even smaller than the native version after compression, impossabru! I actually didn’t expect this myself (last time I did such comparisons the emscripten versions came out about 10..20% bigger)"

This is because JavaScript is alpha-numeric and is easier to compress than binary. There are a relatively 'small' number of characters in the alpha-numeric range, so they can be mapped together easier than the wider range of binary data.

Simple diet tricks for asm.js

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