[Bug middle-end/31029] Fold does not fold a + C == a

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2008-11-02 16:08 -------
This is because fold doesn't fold ig_1 == 1 - ig_1 to a constant.  Which is
just because it doesn't handle this canonical form but expects X +- CST always.

Fixing that makes the first forwprop pass optimize the comparison to false.

I have a patch, queued for 4.5.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rguenth at gcc dot gnu dot
                   |dot org                     |org
           Severity|normal                      |enhancement
             Status|NEW                         |ASSIGNED
          Component|tree-optimization           |middle-end
   Last reconfirmed|2008-08-28 15:40:02         |2008-11-02 16:08:21
               date|                            |
            Summary|missed optimization         |Fold does not fold a + C ==
                   |                            |a


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31029