[Bug tree-optimization/19792] New: Missed optimizations due to signedness in the way

["kazu at cs dot umass dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

Consider:

extern unsigned char size_lookup[257];

int
foo (unsigned int t)
{
  return (size_lookup [(int) t] == size_lookup[t]);
}

int
bar (unsigned int t)
{
  int a = t;
  return a == t;
}

Both functions should return 1, and in fact that's what the RTL optimizers
notice, but the tree optimizers don't.

This is somewhat related to PR 19790.

-- 
           Summary: Missed optimizations due to signedness in the way
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: missed-optimization, TREE
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kazu at cs dot umass dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19792