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

[Eli Zaretskii]

> Date: Thu, 26 Jan 2023 01:21:08 +0200
> Cc: casouri@gmail.com, 60953@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> Thank you. Unfortunately, the performance improvement from this patch is 
> still fairly negligible.

This is quite strange, since all of the approaches basically use the
same primitives under the hood.  Perhaps the reason for the slowness
is that the code which computes the text span of a node is slow?
Otherwise, I must be missing something here, since the rest of the
code on the C level is basically the same, give or take some wrappers
that should not change the overall picture.

Yuan, do you have some insights here?

> 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?