[Bug middle-end/30905] New: [dataflow] Fails to cross-jump

[rguenth at gcc dot gnu dot org]

static int a[30];
static int b[30];
int gen_int(int);
void kernel ()
{
  int i;

  i = gen_int (1);

  if (i != 0)
    {
      a[0] = a[0] + (a[0] & 3);
      b[0] = b[0] + (b[0] | 3);
    }
  else
    {
      a[0] = a[0] + (a[0] & 3);
      b[0] = b[0] + (b[0] | 3);
    }
  if (i != 1)
    {
      a[1] = a[1] + (a[1] & 3);
      b[1] = b[1] + (b[1] | 3);
    }
  else
    {
      a[1] = a[1] + (a[1] & 3);
      b[1] = b[1] + (b[1] | 3);
    }
}

is optimized by mainline to straight line code without compares and jumps at
-O2.  dataflow branch retains the comparisons with i and the duplicate
instructions.


-- 
           Summary: [dataflow] Fails to cross-jump
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30905