[Bug middle-end/13191] New: Redundant sign extends

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

The following testcase taken from lmbench shows gcc inserting needless sign
extends to convert intermediate results to ints (ppc64 logical operations are
done on full 64 bit registers).  Ideally, gcc could implement this function with
just one sign extend for the final result.  Different results, but still not
ideal, are seen when using an int for iter.

typedef long iter;

int
do_integer_bitwise (iter iterations, int r)
{
  int s = iterations;
#if 0
  while (iterations-- > 0)
#endif
    {
      r^=iterations; s^=r; r|=s;
      r^=iterations; s^=r; r|=s;
      r^=iterations; s^=r; r|=s;
      r^=iterations; s^=r; r|=s;
    }
  return r;
}

-- 
           Summary: Redundant sign extends
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: amodra at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13191