bug#20887: 'make bootstrap' now verrrry slow due to recent isearch changes

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 24 Jun 2015 18:18:51 +0100
> From: Artur Malabarba <bruce.connor.am@gmail.com>
> Cc: 20887@debbugs.gnu.org
> 
> > Btw, did you try replacing a simple iteration through all the
> > characters with map-char-table?
> 
> Hadn't thought of that. Indeed, the second loop can be replaced by a
> map-char-table, and it speeds things up by about 30%.

Why only the second?  All you care about is decomposition, that is,
you need only loop over characters that have a non-nil value in the
decomposition property.  You will see in characters.el how you can use
map-char-table over a char-table loaded from uni-decomposition.el
(similar to what we do there with uni-bidi et.).  Won't that be much
faster?

(I didn't actually try that, so perhaps I'm talking nonsense.)