[Bug tree-optimization/43378] New: IVOPTs messes up code

[rguenth at gcc dot gnu dot org]

void bar(int, int, int);
void foo(int left, int rite, int element)
{
  while (left <= rite)
    {
      rite -= element;
      bar(left, rite, element);
      left += element;
    }
}

produces:

foo (int left, int rite, int element)
{
  unsigned int D.2741;
  unsigned int D.2742;
  unsigned int D.2743;
  unsigned int D.2737;
  int D.2738;
  unsigned int D.2739;
  unsigned int D.2740;

<bb 2>:
  if (left_3(D) <= rite_4(D))
    goto <bb 3>;
  else
    goto <bb 6>;

<bb 3>:

<bb 4>:
  # left_14 = PHI <left_7(5), left_3(D)(3)>
  # rite_15 = PHI <rite_6(5), rite_4(D)(3)>
  D.2737_8 = (unsigned int) rite_15;
  D.2738_2 = -element_5(D);
  D.2739_1 = (unsigned int) D.2738_2;
  D.2740_13 = D.2737_8 + D.2739_1;
  rite_12 = (int) D.2740_13;
  rite_6 = rite_12;
  bar (left_14, rite_6, element_5(D));
  D.2741_11 = (unsigned int) left_14;
  D.2742_17 = (unsigned int) element_5(D);
  D.2743_18 = D.2741_11 + D.2742_17;
  left_19 = (int) D.2743_18;
  left_7 = left_19;
  if (rite_6 >= left_7)
    goto <bb 5>;
  else
    goto <bb 6>;

<bb 5>:
  goto <bb 4>;

from

foo (int left, int rite, int element)
{
<bb 2>:
  if (left_3(D) <= rite_4(D))
    goto <bb 3>;
  else
    goto <bb 6>;

<bb 3>:

<bb 4>:
  # left_14 = PHI <left_7(5), left_3(D)(3)>
  # rite_15 = PHI <rite_6(5), rite_4(D)(3)>
  rite_6 = rite_15 - element_5(D);
  bar (left_14, rite_6, element_5(D));
  left_7 = left_14 + element_5(D);
  if (rite_6 >= left_7)
    goto <bb 5>;
  else
    goto <bb 6>;

<bb 5>:
  goto <bb 4>;

as you can see it doesn't even create new induction variables.


-- 
           Summary: IVOPTs messes up code
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
        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=43378