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[Bug tree-optimization/18595] [4.0/4.1 Regression] IV-OPTS is O(N^3)
- From: "sebastian dot pop at cri dot ensmp dot fr" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 3 Nov 2005 19:31:13 -0000
- Subject: [Bug tree-optimization/18595] [4.0/4.1 Regression] IV-OPTS is O(N^3)
- References: <bug-18595-6528@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #58 from sebastian dot pop at cri dot ensmp dot fr 2005-11-03 19:31 -------
Subject: Re: [4.0/4.1 Regression] IV-OPTS is O(N^3)
Here are again the numbers for mainline with no other patch:
time ./gcc/cc1 -O2 ~/ex/pr18595_10.c
real 0m0.164s
user 0m0.116s
sys 0m0.018s
time ./gcc/cc1 -O2 ~/ex/pr18595_100.c
tree PRE : 0.33 ( 3%) usr 0.01 ( 3%) sys 0.34 ( 3%) wall
7742 kB ( 2%) ggc
tree loop bounds : 0.77 ( 7%) usr 0.03 (10%) sys 0.80 ( 7%) wall
53463 kB (17%) ggc
tree iv optimization : 7.70 (74%) usr 0.19 (66%) sys 7.97 (73%) wall
220347 kB (71%) ggc
real 0m10.912s
user 0m10.448s
sys 0m0.317s
For 200 nested loops it begins to swap even with -fno-tree-pre, so
we'd need a patch for limiting this.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18595