[Bug tree-optimization/54146] Very slow compile with attribute((flatten))

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54146

--- Comment #26 from Steven Bosscher <steven at gcc dot gnu.org> 2012-08-06 
22:58:22 UTC ---
(In reply to comment #25)
> 185939 is the number of basic blocks that end up in livein. That is a bitmap,
> so most time is spent in traversing bitmap linked lists.

Oh, and this doesn't happen just once, but several 100 times.
Only to prune the set to (livein & loop_exits) ...