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

[Stefan Monnier]

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

I think it's for compatibility with TECO Emacs or something like that :-)

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

Because the `let` and the `setq` were not performed in the same buffer,
so if the var is buffer-local ...

> 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 think the behavior you experience doesn't require "speeding up" but it
requires "fixing a performance bug".  Technically it's the same, but still..

> I'd prefer the latter as it is used ubiquitously across Emacs and
> making point lookup faster will thus benefit other places as well.

Why choose?

For the former, we could probably extend the `b_property` and
`e_property` fields of `gl_state` (which hold charpos) to also store
their bytepos equivalent, which should significantly reduce the number
of conversions between bytepos and charpos.


        Stefan