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

[Ihor Radchenko]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> I suspect that the patch below might fix the immediate problem.

I confirm that it does fix the problem. But why not `with-temp-buffer'?

Also, how come `setq' changes the global variable value despite it is
let-bound?

> Of course, setting `parse-sexp-lookup-properties` should not have such
> a major performance impact, so maybe we should keep digging into
> the problem.

Agree. I was considering `parse-sexp-lookup-properties' in Org, but this
issue will be a blocker.

To improve the performance, the two obvious ways are reducing the number
of SYNTAX_TABLE_BYTE_TO_CHAR calls in re_match_2_internal and speeding
up buf_bytepos_to_charpos. I'd prefer the latter as it is used
ubiquitously across Emacs and making point lookup faster will thus
benefit other places as well.

-- 
Ihor Radchenko // yantar92,
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