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Few weeks ago I noticed a blog post “Oxidizing Source Maps with Rust and WebAssembly” making rounds on Twitter - talking about performance benefits of replacing plain JavaScript in the core of source-map library with a Rust version compiled to WebAssembly. This post piqued my interest, not because I am a huge on either Rust or WASM, but rather because I am always curious about language features an

This is a note in reply to Kyle Simpson’s question Basics of object layout in V8 Each JavaScript object in V8 looks like this +-------+ | *---+-> hidden class (aka map) +-------+ | *---+-> out-of-object properties storage +-------+ | *---+-> elements storage +-------+ | 1 +-+ +-------+ | | 2 | | +-------+ > N slots reserved for in-object properties ~~~~~~~~~ | +-------+ | | N +-+ +-------+ There a

This is a note in reply to Victor Felder’s question who asked me what “Unsupported phi use of arguments” Crankshaft bailout means. What Crankshaft is trying to do is to completely avoid allocating arguments object when you write the code like this: function foo() { var sum = 0; for (var i = 0; i < arguments.length /* (1) */; i++) { sum += arguments[i]; /* (2) */ } } If one compiles this code naive

Java VM V8 Dart VM complexity ChaCha20 function getBlock(buffer) { var x = new Uint32Array(16); for (var i = 16; i--;) x[i] = input[i]; for (var i = 20; i > 0; i -= 2) { quarterRound(x, 0, 4, 8,12); quarterRound(x, 1, 5, 9,13); quarterRound(x, 2, 6,10,14); quarterRound(x, 3, 7,11,15); quarterRound(x, 0, 5,10,15); quarterRound(x, 1, 6,11,12); quarterRound(x, 2, 7, 8,13); quarterRound(x, 3, 4, 9,14)

Talks and blog posts about JavaScript performance often emphasize importance of monomorphic code. However they usually don’t provide any digestible explanation of what monomorphism/polymorhism is and why it matters. Even my own talks often boil down to Hulk-style «ONE TYPE GOOD. TWO TYPE BAD!!!» dichotomy. Unsurprisingly one of the most common requests I get when people reach out to me for a perfo

My favorite way to bootstrap a Christmas dinner conversation is asking people whether they cache array length accesses before their loops or not. Anybody preferring functional Array.prototype iteration methods to rusty old-school for(;;)-loops gets an additional piece of cake. Anybody choosing for(let x of y) will find a neatly wrapped ES6-to-ES5-compiler under their Christmas tree. But the people

Object subclass: #Vector instanceVariableNames: 'x y' classVariableNames: '' poolDictionaries: '' category: nil! !Vector class methodsFor: 'instance creation'! x: anXNumber y: anYNumber ^ self new x: anXNumber y: anYNumber!! !Vector methodsFor: 'math'! dot: aOther ^ (self x * aOther x) + (self y * aOther y)!! I'm Slava I like compiling things and ranting about that on @mraleph 𝔏 ⇒ 𝔑 𝔏 ∈ {Java,

IRHydra2 is deprecated. Supporting various V8 related features in IRHydra was always a race against the clock. V8 5.9 has switched to a new execution pipeline (TurboFan+Ignition) and modernizing IRHydra to properly work with it would be too much of a time investment for me, given that I don't need to dig into JavaScript performance anymore. Ultimately IRHydra was always just a stopgap solution I c

Sometimes when I search for “jsperf” on Twitter and click through to see some test cases I immediately remember a saying usually attributed to Confucius: “The hardest thing of all is to find a black cat in a dark room, especially if there is no cat.” I like to imagine him rephrasing this saying if Confucius were into JavaScript microbenchmarking himself: “The hardest thing of all is to find which

V8 & DartVM Вячеслав Егоров @mraleph, [email protected] Tech Talks NSU, March 2014 V8 - JS VM внутри Chrome и node.js Dart - новый язык для вебпрограммирования VM - это просто Быстрая VM - сложнее В чем проблема? // Adding integers. function add(a, b) { return a + b; } // Adding doubles. function add(a, b) { return a + b; } // Concatenating strings. function add(a, b) { return a + b; } // Arrays a

I have a thing for virtual machines that are implemented in the language (or a subset of the language) they are built to execute. If I were in the academia or just had a little bit more free time I would definitely start working on a JavaScript VM written in JavaScript. Actually this would not be a unique project for JavaScript because people from Université de Montréal kinda got there first with

Practical / optimization Talks Articles General Talks Other Fundamentals Talks Articles Miscellaneous Practical / optimization Talks Understanding V8 (me, nodecamp.eu 2011) [slides] V8 Performance Tuning Tricks (+Daniel Clifford, GDD2011 Berlin) [slides] Console to Chrome (+Lilli Thompson, GDC 2012) [slides] [video] Breaking the JavaScript Speed Barrier with V8 (+Daniel Clifford, Google I/O 2012)

mraleph a compiler engineer that loves giving talks. { [email protected] | @mraleph } A list of V8 related resources My work setup ▶ Micro​benchmarking Dart (Part 1) ▶ Maybe you don't need Rust and WASM to speed up your JS ▶ The fear of dart:mirrors ▶ Adventures in the land of substrings and RegExps. ▶ Crankshaft vs arguments object ▶ jsunderhood digest (in Russian) ▶ Browser as an Interactive Dis

Please note that this post expresses my personal opinion and mine alone, not those of my employer or my teammates. I am writing it because I can’t hold my opinion inside anymore. My head was starting to feel like a balloon that is going to burst any minute. I am writing my thoughts and feelings down to free myself from this pressure. When reading my ramblings below please keep in mind that I used

I was thinking about writing a smallish blog post summarizing my thoughts on closure variables vs. instance field performance as a reply to Marijn Haverbeke’s post which postulates initial mystery when I realized that this is an ideal candidate for a longer post that illustrates how V8 handles closures and how these design decisions affect performance. Contexts If you program JavaScript you probab