https://bugzilla.redhat.com/show_bug.cgi?id=992362
--- Comment #4 from Jens Petersen petersen@redhat.com --- As far as I can tell this is fixed upstream in the current ghc-7.7 tree (tested with a bootstrap build of ghc-7.7.20130828).
I may try to test later with a non-perf build of ghc-7.6.3 in case that could be related.