Here are the performance numbers about Qt4.5’s improvement in JavaScript performance that I mentioned in yesterday’s post. It offers about a seven times performance improvement on ix86 processors. From Lightning-fast JavaScript:

For Qt 4.5, the JavaScript engine is powered by a new bytecode interpreter, along with optional JIT (just-in-time) compile support. They are often referred as SquirrelFish and SquirrelFish Extreme, respectively. This interpreter has been developed by Apple engineers working on WebKit in order to speed-up JavaScriptCore, the backbone of WebKit’s JavaScript engine. The interpreter makes its first appearance in the recent Safari 4 Public Beta, where it is dubbed as Nitro JavaScript Engine.

Longer is better: