http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54896
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |alias, compile-time-hog
Status|WAITING |NEW
CC| |rguenth at gcc dot gnu.org
Known to work| |4.3.2, 4.4.0
Summary|Some optimization slowness |[4.7/4.8 Regression] Some
|with GCC 4.7.2 |optimization slowness with
| |GCC 4.7.2
Known to fail| |4.7.2, 4.8.0
--- Comment #3 from Steven Bosscher <steven at gcc dot gnu.org> 2012-10-10
22:51:12 UTC ---
Thanks for the test case!
Bug is confirmed with GCC 4.8 (trunk revision 192219).
Problem areas at -O1:
alias stmt walking : 31.68 (36%) usr
tree DSE : 10.83 (12%) usr
CSE : 9.02 (10%) usr
reload CSE regs : 23.17 (26%) usr
TOTAL : 87.99
Problem areas at -O2 are pretty much the same:
alias stmt walking : 47.29 (28%) usr
tree DSE : 10.84 ( 7%) usr
CSE : 9.12 ( 5%) usr
CSE 2 : 34.66 (21%) usr
reload CSE regs : 45.37 (27%) usr
TOTAL : 166.12
GCC 4.3.2 has the same problems at the RTL level:
tree DSE : 11.60 (17%) usr
CSE : 19.74 (28%) usr
CSE 2 : 12.63 (18%) usr
reload CSE regs : 8.49 (12%) usr
TOTAL : 69.68
tree-DSE, CSE and reload-CSE are both quadratic in the number of
instructions per basic block, and all basic blocks in this test
case contain O(10^3) instructions.
The alias stmt walking slowness is a regression, but I suspect
there a dup that Rick Biener already knows about...
