jdmichaud

Optimizing javascript through speculative execution is to speculate on type and produce optimizations based on those speculation.

Profiling is the act of speculating and will allow you to optimize JS execution better.

There are various ways of doing that. You can speculate on the type of variables on each appearance and then chose a path to an optimized code for that type of the slow path if the speculation fails (diamond speculation). The technique used by JavaSciptCore is OSR (On Stack Replacement). It will speculate and definitly exit a optimized path on failing. Exiting is fast and easy, reentry to the optimized path is slow and hard.

JavaScriptCore (the Safari JS VM) has a 4 tier interpreter/compiler infrastructure. JavaScriptCore (JSC) first compile the javascript into the VM bytecode. Then this bytecode get interpreted by LLint (Low Level Interpreter) which does not perfom optimization, just execute and profile the code for the next tier. The next tier is the basline JIT which will convert the bytec

jdmichaud

// rustc lexer.rs && curl -s https://norvig.com/big.txt | ./lexer

use std::io::{Read, Result, stdin};

#[derive(Debug)]
struct Token<'a> {
  s: &'a str,
  start_index: usize,
}

jdmichaud

// rustc lexer.rs && curl -s https://norvig.com/big.txt | ./lexer

use std::io::{Read, Result, stdin};

#[derive(Debug)]
struct Token<'a> {
  s: &'a str,
  start_index: usize,
}

jdmichaud

On a Ubuntu 19.04
## Install the necessary package:
```
sudo apt-get install \
  qemu-kvm \
  libvirt-daemon-system \
  libvirt-clients \
  bridge-utils \
  libosinfo-bin \
  libguestfs-tools

jdmichaud

use Obsevable;
use Observer;

fn main() {
  let observable = new Observable<u8>(|observer: &mut Observer<u8>| {
    observer.next(255);
    observer.complete();
  });
    
  let subscription1 = observable.subscribe({

jdmichaud

#!/bin/bash

# First download the page listing all the dumps, then extract, with some brittle xpath magic the list of dump files and curl them locally.
curl -sL https://dumps.wikimedia.org/commonswiki/20210420/ | \
  xidel --xpath '//li[./span[contains(@class, "title") and ./big/b/text() = "Articles, templates, media/file descriptions, and primary meta-pages."]]/ul/li/a/@href' - | \
  xargs -n 1 -i curl --progress-bar -OL -C - https://dumps.wikimedia.org/{}

jdmichaud

Vim grammar

Reload configuration after change: :so $MYVIMRC

navigate:

• hjkl: <v^>
• w: advance to beginning of next word
• b: rewind to beginning of next word
• e: advance to end of next word
• Ctrl-o: exit INSERT mode for one and only one command, then get back at it

jdmichaud

from functools import reduce
from datetime import datetime
from jours_feries_france import JoursFeries

def computeJoursFeries(year):
  return reduce(
    lambda acc, day: acc + 1 if day.isoweekday() != 6 and day.isoweekday() != 7 else acc,
    JoursFeries.for_year(year).values(),
    0,
  )

jdmichaud

Source ─(scanner)─► Tokens ─(parser)─► AST ─(binder)─► Symbol ─(checker)──(emitter)─► JS
                                        │                          ▲          ▲
                                        ╰──────────────────────────╯──────────╯

jdmichaud