[Bug tree-optimization/59209] builtin memcpy in inlined function is not optimized away if count is derived from src pointer difference

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59209

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
In test_copy2, we get:

  _2 = x_1(D) + 1;
  src_end.1_8 = (long int) _2;
  src_start.2_9 = (long int) x_1(D);
  _10 = src_end.1_8 - src_start.2_9;
  _11 = (long unsigned int) _10;

This reminds me of PR 58742: we are failing to simplify basic arithmetic on
pointers.