>> 1362a9fec4 improvement from 130s to 119s (8%) Mattias Engdegård Make 
>> lambda-lifting work again
>
> That just fixed a typo introduced a week or so before, which should 
> cancel it out.
>

Indeed.  The typo in which that typo was introduced was

a350ae058c deterioration from 108s to 129s (19%) Stefan Monnier 
<monnier@iro.umontreal.ca> * lisp/emacs-lisp/cconv.el: Improve line-nb 
info of unused var warnings

And I just checked that fixing that typo in that commit removes the 19% 
slowdown.  This answers one of Lars' questions:

>> a350ae058c deterioration from 108s to 129s (19%) Stefan Monnier 
>> <monnier@iro.umontreal.ca> * lisp/emacs-lisp/cconv.el: Improve line-nb 
>> info of unused var warnings
>
> Hm...  is that something that can be improved (if that code is still 
> there, that is)?
>