[Bug tree-optimization/51492] vectorizer does not support saturated arithmetic patterns

["pan2.li at intel dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51492

--- Comment #16 from Li Pan <pan2.li at intel dot com> ---
I have a try like below and finally have the Standard Name "SAT_ADD". Could you
please help to double-check if my understanding is correct?

Given below example code below:

typedef unsigned int uint32_t;

uint32_t
sat_add (uint32_t x, uint32_t y)
{
  return (x + y) | - ((x + y) < x);
}

And then add one simpify to match.pd and define new DEF_INTERNAL_OPTAB_FN for
it. Then we have the SAT_ADD representation after expand.

uint32_t sat_add (uint32_t x, uint32_t y)
{
  uint32_t _6;

;;   basic block 2, loop depth 0
;;    pred:       ENTRY
  _6 = .SAT_ADD (x_4(D), y_5(D)); [tail call]
  return _6;
;;    succ:       EXIT

}

If everything goes well, I will prepare the patch for it later. Thanks.