[Bug tree-optimization/46590] [4.6/4.7/4.8 Regression] long compile time with -O2 and many loops

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46590

--- Comment #32 from Steven Bosscher <steven at gcc dot gnu.org> 2012-08-23 13:44:53 UTC ---
(In reply to comment #31)
> which helps reducing the time spent in computing dominance frontiers.  But
> as we no longer have bitmaps but bitmap_heads in dfs it's hard to verify
> we only ever access dfs for entries we computed ... but we should,
> looking at how compute_idf works(?).

I don't understand this comment. You can still always do:
bitmap_empty_p (&dfs[bb->index]) to see if something was
computed for bb.