[Bug middle-end/84756] Multiplication done twice just to get upper and lower parts of product

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84756

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-09-05
          Component|target                      |middle-end
             Status|UNCONFIRMED                 |NEW
           Severity|normal                      |enhancement
     Ever confirmed|0                           |1

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, we should be able to do part (all?) of this at the gimple level:
  _3 = a_6(D) w* b_7(D);
  _4 = _3 >> 64;
  _5 = (long unsigned int) _4;
  *upper_9(D) = _5;
  _11 = a_6(D) * b_7(D);
  return _11;

(long unsigned int)_3 is the same as _11.