"unhandled use" in vectorizing a dot product?

[Benjamin Redelings I <benjamin_redelings at ncsu dot edu>]

Hi,

    I noticed that (in gcc 4.5 as of Oct-18) the following code is not 
vectorized:

float sum=0;
int i;
for(i=0;i<16;i++)
  sum += f1[i]*f2[i];

The error is "unhandled use in statement"

However, the web page at 
http://gcc.gnu.org/projects/tree-ssa/vectorization.html says:

"Detection and vectorization of special idioms, such as dot-product and 
widening-summation: Incorporated into GCC 4.2."

Can you tell me if I am missing something?  Is the web page correct?

-BenRI
#define ALIGNED __attribute__((aligned(16)))

float* ALIGNED s1(int);
int s2(float);


int main(int argc, char* argv[])
{
  float* __restrict f1 ALIGNED = s1(0);
  float* __restrict f2 ALIGNED = s1(0);

  float sum=0;
  int i;
  for(i=0;i<16;i++)
    sum += f1[i]*f2[i];
  s2(sum);
  return 0;
}