A faster derived-mode-p

[Lars Ingebrigtsen]

There are only 11K commands in the Emacs tree, so I don't know whether
the current default completion predicate is going to turn out to be
problematically slow or not.

It basically calls `provided-mode-derived-p' for all annotated commands,
and this is a loop that chases mode parenthood back to its ultimate
ancestor.

It seems like this could done more efficiently by just resolving the
chain at `define-derived-mode' time.  That is, in addition to putting
`derived-mode-parent', it could put `derived-mode-parents', too, where
it chases the chain upwards.  Then we'd just have to look at a single
property list...

Does anybody see any disadvantages to doing it this way?  (This would
speed up `derived-mode-p', which we use all over Emacs, in general.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no