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

["sebastian dot pop at cri dot ensmp dot fr" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From sebastian dot pop at cri dot ensmp dot fr  2005-01-25 11:02 -------
Subject: Re:  [4.0 Regression] IV-OPTS is O(N^3)

rakdver at atrey dot karlin dot mff dot cuni dot cz wrote:
> 
> (*) I hope; scev is a mess of mutualy recursive functions --
> analyze_scalar_evolution calling number_of_iterations calling
> instantiate_parameters calling analyze_scalar_evolution again, with
> instantiate_parameters hacked so that the infinite cycle cannot occur is
> my favourite one.  Nobody can say anything sure about behavior of scev
> -- it is not even well defined what analyze_scalar_evolutions will
> return to you, 

It returns to you an evolution that might contain SSA_NAMEs.

> unless you call instantiate_parameters or resolve_mixers
> on the result.
> 

And once you call instantiate_parameters on the result you're
guaranteed that what you get does contain only determined constants,
or otherwise the result is chrec_dont_know.



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