gcc/testsuite/gcc.dg/tree-ssa/ldist-1.c

/* { dg-do compile } */ 
/* { dg-options "-O2 -ftree-loop-distribution -fdump-tree-ldist-all" } */

void foo (int * __restrict__ ia,
	  int * __restrict__ ib,
	  int * __restrict__ oxa,
	  int * __restrict__ oxb,
	  int * __restrict__ oya,
	  int * __restrict__ oyb)
{
  int i;
  long int mya[52];
  long int myb[52];

  for (i=0; i < 52; i++)
    {
      mya[i] = ia[i] * oxa[i] + ib[i] * oxb[i];
      myb[i] = -ia[i] * oxb[i] + ib[i] * oxa[i];
      oya[i] = mya[i] >> 10;
      oyb[i] = myb[i] >> 10;
    }

  /* This loop was distributed, but it is not anymore due to the cost
     model changes: the result of a distribution would look like this:

     |  for (i=0; i < 52; i++)
     |    oya[i] = ia[i] * oxa[i] + ib[i] * oxb[i] >> 10;
     |
     |  for (i=0; i < 52; i++)
     |    oyb[i] = -ia[i] * oxb[i] + ib[i] * oxa[i] >> 10;

     and in this the array IA is read in both tasks.  For maximizing
     the cache reuse, ldist does not distributes this loop anymore.
  */
}

/* { dg-final { scan-tree-dump-times "distributed: split to 2 loops" 0 "ldist" } } */