[Bug c/43423] New: gcc should vectorize this loop through "iteration range splitting"

[changpeng dot fang at amd dot com]

chf...@pathscale:~/gcc$ cat foo.c
int a[100], b[100], c[100];

void foo(int n, int mid)
{
  int i;
  for(i=0; i<n; i++)
    {
      if (i < mid)
        a[i] = a[i] + b[i];
      else
        a[i] = a[i] + c[i];
    }
}


chf...@pathscale:~/gcc$ gcc -O3 -ftree-vectorizer-verbose=7 -c foo.c

foo.c:6: note: not vectorized: control flow in loop.
foo.c:3: note: vectorized 0 loops in function.

This loop can be vectorized by icc.

For this case, I would expect to see two loops with iteration range
of [0, mid) and [mid, n). Then both loops can be vectorized.

I am not sure which pass in gcc should do this iteration range splitting.


-- 
           Summary: gcc should vectorize this loop through "iteration range
                    splitting"
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: changpeng dot fang at amd dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43423