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[Bug tree-optimization/18595] [4.0 Regression] IV-OPTS is O(N^3)
- From: "belyshev at lubercy dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 25 Nov 2004 11:16:31 -0000
- Subject: [Bug tree-optimization/18595] [4.0 Regression] IV-OPTS is O(N^3)
- References: <20041121145949.18595.pinskia@gcc.gnu.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From belyshev at lubercy dot com 2004-11-25 11:16 -------
use this awk script to generate testcase (first arg is number of loops):
----------------------------------------------------------------------------------------
BEGIN {
ORS=""
print "int f ()\n{\tint "
for (j = 0; j < ARGV [1]; j++)
print "j" j ", "
print "a;\n\ta = 0;\n"
print "\tfor (j0 = 0; j0 < 2; j0 ++)\n"
for (j = 1; j < ARGV [1]; j++)
print "\tfor (j" j " = j" j-1 "; j" j " < 2; j" j" ++)\n"
print "\ta += "
for (j = 0; j < ARGV [1]-1; j++)
print "j" j " + "
print "j" j ";\n\treturn a;\n}\n"
}
----------------------------------------------------------------------------------------
N loops Time, s
5 0.05
10 0.17
15 0.38
20 1.14
25 2.81
30 4.68
35 7.52
40 13.6
45 21.8
50 25.6
55 33.9
--
What |Removed |Added
----------------------------------------------------------------------------
Severity|minor |normal
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Keywords| |memory-hog
Known to fail| |4.0.0
Last reconfirmed|0000-00-00 00:00:00 |2004-11-25 11:16:30
date| |
Summary|IV-OPTS is slow (and does |[4.0 Regression] IV-OPTS is
|not scale) |O(N^3)
Target Milestone|--- |4.0.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18595