http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39326
--- Comment #22 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-06 11:38:07 UTC --- 4.7.2 -O0 25s 2189981kB integrated RA : 8.96 (35%) usr 0.89 (28%) sys 9.89 (34%) wall 206439 kB (16%) ggc reload : 2.98 (12%) usr 0.07 ( 2%) sys 3.05 (11%) wall 43197 kB ( 3%) ggc 4.8.0 -O0 29s 2111318kB integrated RA : 8.88 (31%) usr 0.41 (13%) sys 9.32 (29%) wall 206439 kB (18%) ggc LRA non-specific : 5.50 (19%) usr 0.08 ( 3%) sys 5.59 (17%) wall 4600 kB ( 0%) ggc 4.8.0 -O2 (terminated after 9 minutes waiting, LIM being the offender, I suspect domwalk ...) >2.5GB applying domwalk fix ... 4.8.0 -O1 still awfully slow the smaller testcase is also tested on http://gcc.opensuse.org/c++bench/random/ but it runs OOM at -O1 and -O2 there (there is a virtual ulimit of 1GB due to lack of resources on the machine), but -O3 surprisingly works so you can see a recent time-report there (also for -O0). At -O3 you can see there (everything > 10%): tree loop invariant motion: 53.83 (13%) usr PRE : 116.26 (29%) usr LRA hard reg assignment : 73.68 (18%) usr load CSE after reload : 38.67 (10%) usr ISTR the testcases are not exactly exposing the same issues.