bug#58342: 29.0.50; noverlay branch is O(N) for important calls

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: matt@rfc20.org,  bug-gnu-emacs@gnu.org,  mail@andreas-politz.de,
>   gerd.moellmann@gmail.com
> Date: Fri, 07 Oct 2022 09:36:50 -0400
> 
> Eli Zaretskii [2022-10-07 10:09:39] wrote:
> >> [ Site note: `previous-overlay-change` is probably not very important in
> >>   practice, but `next-overlay-change` OTOH is indeed important because
> >>   it's used during redisplay.
> > previous-overlay-change is also called by redisplay (but I didn't see
> > how frequently), at least if you look at the code from the static
> > analysis POV.
> 
> Do you happen to know via which path it can be called (beside the obvious
> ones when the redisplay ends up calling ELisp, such as via jit-lock)?

 pos_visible_p
  -> previous-single-char-property-change
      -> previous-char-property-change
          -> previous-overlay-change

Also:

 set_point_both
  -> previous-char-property-change
      -> previous-overlay-change