Created attachment 586712 [details] testcase (zlib) This testcase has become 10x slower with 83343:eaac85c4c05f http://hg.mozilla.org/mozilla-central/rev/eaac85c4c05f The regression is with |-m -n|. I guess this is because of additional analysis now done in switches. The bug mentions that bug 709614 will help here.
Err, that should have been bug 706914 in the last comment, sorry (I did get the "depends on" right though ;)
Bug 706914 has landed, but seems to not help here.
This appears to not be an issue anymore. -n makes it 17% slower but at least not 10x.