[Bug tree-optimization/8681] Generates unneeded test

[dnovillo at redhat dot com]

------- Additional Comments From dnovillo at redhat dot com  2005-04-24 18:07 -------
Subject: Re:  Generates unneeded test

On Sun, Apr 24, 2005 at 05:56:50PM -0000, pinskia at gcc dot gnu dot org wrote:
> 
> i_15: [1, 2147483647]
> i_16: [0, 2147483647]
> i_20: VARYING 
> 
>   # i_20 = PHI <i_15(3), 0(0)>;
> 
> 
> Looks like VRP does not understand PHI functions or it just gives up too often.
> 
i_15 and 0 have a non-empty intersection and so vrp_meet returns
VARYING.  VRP does not handle multiple ranges, but in this case
it should not be hard to merge the two adjacent ranges [1, +INF]
and [0, 0].  

What is the type of 'i'?  If it's unsigned, then we would be
wasting our time.


Diego.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=8681