There are different forks of quickjs that implement bits and pieces of really awesome things around QuickJS. One such effort by @openwebf team implements support for Poly IC in quickjs which results in some significant improvement in performance by up to 40%.

https://github.com/openwebf/quickjs

And even a patch shared on freelists devel: https://www.freelists.org/post/quickjs-devel/Support-Poly-Inline-Cache-in-Get-and-Set-Property

Any thoughts about whether this could be something that is added here in future too?