Peeling loops at tree level?

[Richard Guenther <rguenth at tat dot physik dot uni-tuebingen dot de>]

Hi!

Do we (I suspect not) peel small loops at tree level yet?  This seems
to inhibit further (tree) optimization of inlined dimension-unaware
code like:

template <int Dim>
struct Vector
{
        int operator[](int i) const { return val[i]; }
        int val[Dim];
};

template <int Dim>
inline int foo(const Vector<Dim>& x)
{
        int res;
        for (int i=0; i<Dim; ++i)
                res += x[i];
        return res;
}

int bar(const Vector<3>& x)
{
        return foo(x);
}


where optimized tree dump for -O2 -funroll-loops looks like


;; Function int bar(const Vector<3>&) (_Z3barRK6VectorILi3EE)

int bar(const Vector<3>&) (x)
{
  struct Vector<3> & x.15;
  <unnamed type> D.1651;
  <unnamed type> D.1652;
  const int * ivtmp.8;
  int i.2;
  int D.1634;
  struct Vector<3> * const this;
  int i;
  int i;
  int res;
  int D.1625;
  int retval.1;
  int D.1623;
  bool retval.0;
  struct Vector<3> & x;
  int D.1591;
  int D.1590;

<bb 0>:
  ivtmp.8 = &x->val[0];
  i = 0;

Invalid sum of incoming frequencies 12233, should be 10000
<L0>:;
  res = *ivtmp.8 + res;
  D.1652 = (<unnamed type>) i + 1;
  i = (int) D.1652;
  ivtmp.8 = ivtmp.8 + 4B;
  if (D.1652 != 3) goto <L0>; else goto <L3>;

Invalid sum of incoming frequencies 1100, should be 3333
<L3>:;
  return res;

}

and only in the assembler dump the loop is unrolled (g++-3.5 (GCC) 4.0.0
20040913 (experimental)).

Is there some magic option to tell the tree-level loop-optimizer peel
constant running loops completely?

Thanks,
Richard.

--
Richard Guenther <richard dot guenther at uni-tuebingen dot de>
WWW: http://www.tat.physik.uni-tuebingen.de/~rguenth/