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

[sebastian dot pop at cri dot ensmp dot fr]

------- Additional Comments From sebastian dot pop at cri dot ensmp dot fr  2005-01-25 16:26 -------
Subject: Re:  [4.0 Regression] IV-OPTS is O(N^3)

> > If you decide to reconstruct the tree expression, there is no reason
> > to stop on a phi node that has a single argument.  Why would you like
> > to get this answer as the reconstructed tree?
> 
> because this answer preserves loop closed ssa form -- the answer x_1 + 1
> copy propagates the value outsied of the loop.  In some applications
> this choice could make sense.
> 

Okay, if it makes sense, you could modify the analyzer such that it
stops reconstructing the tree once it is on the phi following a loop.
This won't change the information provided after the instantiation.



-- 


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