bug#58558: 29.0.50; re-search-forward is slow in some buffers

[Ihor Radchenko]

Eli Zaretskii <eliz@gnu.org> writes:

> I think we should first go back to using perf.  I don't think you
> compared profiles for Emacs which just started with one that was
> running long enough to show the slowdown.  Comparing such profiles
> should at least give us a hint where to look.

I now tried perf record -g.
I was able to narrow down the call tree of the problematic
buf_bytepos_to_charpos calls:

43.82%--Fre_search_forward
 --43.81%--search_command
  --43.78%--search_buffer
   --43.78%--search_buffer_re
    --43.33%--re_search_2
     --36.39%--re_match_2_internal
      --21.90%--SYNTAX_TABLE_BYTE_TO_CHAR
       --21.57%--BYTE_TO_CHAR
        --21.49%--buf_bytepos_to_charpos

Not sure if it is telling much.

I also looked into git history and I can only identify significant
changes in re_match_2_internal after Emacs 28 release.

-- 
Ihor Radchenko // yantar92,
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