Performance regression on typechecking type families?

[Dr. ERDI Gergo]

Hi,

Prompted by this question: 
http://stackoverflow.com/questions/26538595/more-efficient-type-level-computations-using-type-families
I wrote some code today using closed type families and datakinds. Also, as 
a baseline, I typechecked the code using open type families from 
the original question.

The two files are here:

https://gist.github.com/gergoerdi/727f028e4c1ed158ac9a
https://gist.github.com/gergoerdi/f96d1a9a58f5e3dccc18

On GHC 7.8.3, typechecking took about 45 seconds for each. However, on a 
'perf' build of GHC 7.9 d8c437b3, with ghc-stage2, the first one took 1m3s 
and the second one 1m12s. A 40% and 60% increase in typechecking time, 
respectively!

Is this some known regression, something surprising, or is 'perf' simply 
not the right build flavour for this kind of comparison?

Bye,
 	Gergo