Help understanding tree-affine.c

[Revital1 Eres <ERES at il dot ibm dot com>]

Hello,

I am trying to understand the usage of some functions in tree-affine.c
file and I appreciate your help.

For example; for the two memory accesses
 arr[b+8].X  and  arr[b+9].X, how does their affine combinations
will look like after executing the following sequence of operation?
(taken from http://gcc.gnu.org/ml/gcc-patches/2007-01/msg02605.html)

get_inner_reference_aff (mem1, &off1, &size1);
get_inner_reference_aff (mem2, &off2, &size2);
aff_combination_expand (&off1, ttae_cache);
aff_combination_expand (&off2, ttae_cache);
aff_combination_scale (&off1, double_int_minus_one);
aff_combination_add (&off2, &off1);

Also, why does diff->n is an indication for the fact that two memory
accesses can overlap in the following snippet taken from the above link?

static bool
cannot_overlap_p (aff_tree *diff, double_int size1, double_int size2)
{
  double_int d, bound;

  /* Unless the difference is a constant, we fail.  */
  if (diff->n != 0)
    return false;

Thanks in advance,
Revital