This seems to be a complete forked repository.  Is it possible to show
a patch relative to the current master?
https://gitlab.com/atamariya/emacs/compare/v0.5...dev

Most relevant changes are in lisp/cedet/semantic/java.el . Other minor changes are for disabling jit-lock.
- Font lock setup : semantic-font-lock-mode()
- Fontify region function: extract()
- Helper function: semantic-fontify-tag()

you could run a benchmark of scrolling through a
large source file top to bottom, and show the results in terms of time
and number of GCs.
Not sure how to do this. If you can help me with steps, I can collect the data.