[Bug tree-optimization/46009] New: ?: vectorized, very similar if is not

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46009

           Summary: ?: vectorized, very similar if is not
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jakub@gcc.gnu.org
                CC: irar@gcc.gnu.org


void bar (int *);
void foo (int *a, int *b, int *c, int *d)
{
  int e[1024], i, g;
  for (i = 0; i < 1024; i++)
    {
      g = a[i] + b[i] + c[i] * d[i];;
#ifdef WORKS
      e[i] = g < 10 ? 1 : g;
#else
      if (g < 10)
        e[i] = 1;
      else
        e[i] = g;
#endif
    }
  bar (e);
}

is vectorized only if -DWORKS -O3, but not for -O3, although the code is really
identical.  Not sure if ifcvt should handle this, or instead some earlier pass
should detect that both bbs have the same memory destination and change
  if (g_25 <= 9)
    goto <bb 4>;
  else
    goto <bb 5>;

<bb 4>:
  e[i_14] = 1;
  goto <bb 6>;

<bb 5>:
  e[i_14] = g_25;

<bb 6>:

into an unconditional assignment of a PHI result into e[i].