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I recently came across this awesome article and presentation about Breaking the JavaScript Speed Limit with V8. This is awesome!

However, I'm a Firefox fan and wondering if there's a way to profile the JIT for Mozilla's tools. Mostly I'd like to see if a compilation has to bail or is missing out on some kind of optimization that could otherwise be had.

Is this possible? Thanks!

jocull
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It's possible in debug Firefox builds to some extent. In an opt build you can install https://addons.mozilla.org/en-US/firefox/addon/jit-inspector/ which will tell you what the JIT is doing, but not what it could have done....

Boris Zbarsky
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  • Cool! Any tips or blogs on how to use it effectively or read the output? – jocull Jan 10 '14 at 13:40
  • I don't know of any offhand. :( I mostly use it to easily read the generated assembly on hot codepaths, but that's not all that useful for someone who's not actually hacking on the JIT... – Boris Zbarsky Jan 10 '14 at 15:51