Dart VM
Warning This document is work in progress. Please contact Vyacheslav Egorov (by mail or @mraleph) if you have any questions, suggestions, bug reports. Last update: Oct 6 2022 This document is intended as a reference for new members of the Dart VM team, potential external contributors or just anybody interested in VM internals. It starts with a high-level overview of the Dart VM and then proceeds t
Maybe you don't need Rust and WASM to speed up your JS
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
Crankshaft vs arguments object
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
new Fn(...) vs. Object.create(P)
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
Do not Measure the Weather
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)
Browser as an Interactive Disassembler
[The title of this post is intentionally a bit misleading - it should be Browser as an Interactive Disassembly Exploration Tool but that’s way too confusing] Due to the nature of my work I often have to dig through disassembly listings. Usually these are spat out by a compiler I’m working or worked on, which makes it easy to recognize familiar patterns and reconstruct the flow of the program. Asse
IRHydra2
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
The Black Cat of Microbenchmarks
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
JIT compilation - TechTalksNSU - March 2014
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
V8 Resources
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)
Why asm.js bothers me
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
Release the IRHydra!
Compilers are not magical beasts. They are steampunk machines grinding your perfectly structured source into incomprehensible mess of native code. The better the compiler - the finer the grind and stronger our performance espresso. What’s not to like? When however something clogs compiler’s pipes, we find ourselves staring at square meters of intermediate representation printouts and deoptimizatio
microbenchmarks fairy tale
Imagine for a moment that you are a modern day hero. A prince or a princess adept in JavaScript programming traveling through enchanted world and searching for the World’s Salvation, the Ultimate Love or the well guarded recipe of Siberian dumplings. Sooner or later you encounter a merciless Sphinx who asks you the simplest question you’ve ever heard in your life: “What is the cost of accessing th
Grokking V8 closures for fun (and profit?)
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
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