TenFourFox Feature Parity Release 22 beta 1 is now available (downloads, hashes, release notes). I have abandoned trying to write that AltiVec GCM routine because it really needs 64-bit elements, something that 32-bit AltiVec obviously doesn't have, and the 32-bit version I attempted to throw together ended up being not much faster (if at all) than a scalar approach. Since this seemed like a lot of risk for no gain, I just threw in the towel. Instead, this release has a syntactic update to JavaScript and also improves the performance of H.264 streams using the MP4 Enabler, especially on multiprocessor systems. This now by default uses the lower "fast" quality mode of ffmpeg and because it is not spec-compliant may cause odd behaviour on a few videos. If you notice this, advise which URL, and then set tenfourfox.mp4.high_quality to true (you may need to add this preference). TenFourFox FPR22 final will come out parallel with Firefox 76/68.8 on or around May 5.

http://tenfourfox.blogspot.com/2020/04/tenfourfox-fpr22b1-available.html