[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 10:39 -------
Subject: Re:  [4.0 Regression] IV-OPTS is O(N^3)

rakdver at atrey dot karlin dot mff dot cuni dot cz wrote:
> 
> How?  If the reference is left in symbolic form, it means that you know
> nothing about its value, so the only thing you can do with it is to
> check its equality/inequality, in code like
> 
> while (...)
>   {
>     i = something_weird ();
> 
>     a[i] = ...;  (a)
>     a[i+1] = ...;  (b)
>     a[i] = ...;  (c)
>   }
> 

The following is probably a more frequent case:

i = 0
x = something_weird () or a function parameter
loop
  i = i + 1 
  a[i] = ...
  ... = a[i + x]
endloop

where you end with a symbolic distance vector.



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