[Bug tree-optimization/23745] New: VRP does not get information from casts from a smaller precision

["pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

An example:
int f(_Bool a)
{
  int t = a;
  if (t != 2)
   return 0;
  return 1;
}
int f1(unsigned char a)
{
  int t = a;
  if (t != 256)
   return 0;
  return 1;
}

Both of these we can find that if statement is always true.  No other pass does this currently.

-- 
           Summary: VRP does not get information from casts from a smaller
                    precision
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23745