[Bug tree-optimization/18595] [4.0/4.1 Regression] IV-OPTS is O(N^3)

[sebastian dot pop at cri dot ensmp dot fr]

------- 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.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18595