Newhouse: Because you need the ****ysis p*** and interpreting IR.

Gieser: C or c++ code that you actually spend time optimizing is faster than javascript code that you’ve spent time optimizing. and java, for that matter.

Mollo: Gajus: it’s possible with ES6 modules

Trucchi: Yamasaki: I’m genuinely curious, what’s your argument citations aside that Java would be faster than C++?

Pelchat: Ok guys can you help me figure out what in the parllax code is preventing my code http://www.casumon.com/viewport/px2.html from working like this example http://jsfiddle.net/ns20rkms/

Standen: It’s not possible with CommonJS ones

Pelchat: I want it to stretch to window height but go offscreen

Trucchi: Because all else being equal, C++ tends to be faster though there are always specific use-cases where one thing wins over the other

Buchheit: Dekok: Right. That ***umes that all of the code is using ES6 modules down the dependency chain

Mischke: Granted, PyPy is written in PyPy itself. It’s a self hosted JIT. It’s quite neat

Marek: Ie. lodash should be using that too

Walters: Gajus: import only works with ES6 modules.

Litzau: And since npm packages are being distributed with ES5 code in /dist/ which is different from /src/ that wouldn’t work.

Krites: Anything else is a deviation of the spec

Fisher: Java can be faster than c++, for unoptimized c++ or java, and ***uming you’ve spent the time tuning the vm and gc parameters to your wo***oad, and that your code doesn’t hit an edge case in the vm. etc.

Yamasaki: Trucchi: Well, isn’t javscript making the same claim, because it has a trace-jit, it produces much faster code than any static compiler could do. the compiler cannot predict the hotspots, hence the optimizations are more generic and not really focused on what gets executed the most

Trucchi: Eh? but the C++ compiler does focus on what gets executed the most in some situations

Pennacchio: Yamasaki: you can do PGO

Yamasaki: But then it seems strange that these vms and jits are not written in their own language for performance reasons, like they are e.g in Lisp

Trucchi: Yamasaki: anyway, this isn’t necessarily a hypothetical – you can compare nashorn written in Java and v8

Mulkins: This channel is amazing

Schirpke: But, you actually have control over the performance in c++, and hand optimized c++ can hit, or come very close to the limits of the machine in many cases

Rowand: And PGO doesn’t have the problem of being limited in time, like most JITs do.

Trucchi: Though nashorn is still being worked on and is a newer product

Trucchi: I think whether you want a vm/jit written in its own language very much depends on the language and what your needs are

Raitt: Yamasaki: the amount of work you’d need for writing a self-hosted JIT is quite a lot. For JS, you’d need to come up with a restricted subset, just like PyPy uses RPython

Prutt: Because full JS is too dynamic

Trucchi: In theory you could do something like that with WASM or ASM.js

Chevas: WASM still needs to support platform-independent JIT’ing for that to be efficient though

Mcgath: Yamasaki: the thing about c++ is that you have very little or no runtime overhead essentially none if you turn off rtti and exceptions, and can use compiler intrinsics or even inline ***embly to ensure the code you want is executed.

Trucchi: Besides which, there’s a benefit to having it in another language, at least when it comes to javascript

Yamasaki: Trucchi: vtune from intel did also hotspot ****ysis/tracing, but clang/gcc do not. they judge just from the code what to optimize and from the programmers hints. e.g. Linux uses unlikely to tell the compiler what it should ***ume about the likelihood of branching. a tracing jit will find that out by itself

Trucchi: Which is the ability to do native extensions and integrations

Trucchi: Oh, you’re talking about JIT on the C++ code, not on the JS code being compiled