[Bug tree-optimization/21458] VRP does not remove a conditional in a loop

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2005-05-10 05:47 
-------
DOM leaves PHI nodes like

  # i_5 = PHI <1(0)>;

Then SCEV gives a symbolic initial value like i_5 with the step being 1.

So the information from SCEV is useless here.

With a tcb-like pass ordering (running VRP after CCP, COPY-PROP, etc
but before DOM), we don't see a degenerate PHI node like above.
Then it's just a matter of making vrp_meet slightly aggressive on
meeting two VR_RANGEs.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |kazu at cs dot umass dot edu
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21458