bug#60953: The :match predicate with large regexp in tree-sitter font-lock seems inefficient

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Wed, 25 Jan 2023 23:17:25 -0800
> Cc: Dmitry Gutov <dgutov@yandex.ru>,
>  60953@debbugs.gnu.org
> 
> >> Switching to using :pred with function (like I did in commit 
> >> d94dc606a0934) which still uses buffer-substring inside is significantly 
> >> faster.
> > 
> > If the performance issue is fixed, then the only aspect that we should
> > perhaps try to improve is consing.  Consing a string each time you
> > need to fontify increases the GC pressure, so if there's a good way of
> > avoiding that without performance degradation, we should take it.  Is
> > it possible to use your :pred technique in a way that doesn't need to
> > produce strings from buffer text?
> 
> Why is :pred more performant though? They just use string-match-p. If 
> anything, the :pred predicates should be more expensive, since they execute 
> lisp functions and conses tree-sitter nodes into lisp objects.

Yes, exactly my thoughts.

Perhaps Dmitry could present comparison of profiles from perf which
would allow us to understand the reason(s)?