Mozilla people have been working on SpiderMonkey performance already: https://jandemooij.nl/blog/2017/12/06/some-spidermonkey-optimizations-in-firefox-quantum/

Mozilla people have been working on SpiderMonkey performance already: https://jandemooij.nl/blog/2017/12/06/some-spidermonkey-optimizations-in-firefox-quantum/ https://jandemooij.nl/blog/2017/12/06/some-spidermonkey-opti..., it's just not some wholesale replacement, so it probably never makes the top of the list for what they shout about. It also sounds like it has been a steady progression rather than a big jump, so maybe not quite as noticeable.