[Bug middle-end/56719] missed optimization: i > 0xffff || i*4 > 0xffff

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56719

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-03-25
          Component|rtl-optimization            |middle-end
     Ever Confirmed|0                           |1

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-25 12:21:21 UTC ---
I don't think this has anything to do with VRP.  VRP does not propagate
"backwards", that is, optimize away the first compare in

  if (i > 0xffff)
    if (i*4 > 0xffff)

from ranges derived from a compare following it.

This is a missed optimization in fold instead.  Not sure if practically
relevant though.