[Bug tree-optimization/18673] [4.0 Regression] Tree-PRE is O(N^4)

[dberlin at gcc dot gnu dot org]

------- Additional Comments From dberlin at gcc dot gnu dot org  2004-11-26 23:00 -------
Actually, Tree-PRE is provably O(n^2). We just have a larger constant than we'd
like.
On all the branches i have checked out (tcb, mainline) 150 loops takes 30
seconds, not 160.

THis includes the constification patch i had posted, however, on these branches.
I can solve this problem once and for all by using a scoped bitmap set
representation instead of copying the sets around.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18673