[Bug tree-optimization/102888] missing case for combining / and % into one operation

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102888

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-10-22

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  The complication is that the loop is rotated to do { } while ()
form
and that puts div and mod of different iterations next to each other:

  <bb 2> [local count: 118111600]:
  _8 = a_3(D) % b_4(D);
  if (_8 == 0)
    goto <bb 5>; [89.00%]
  else
    goto <bb 4>; [11.00%]

  <bb 5> [local count: 105119324]:

  <bb 3> [local count: 955630225]:
  # a_9 = PHI <a_7(6), a_3(D)(5)>
  a_7 = a_9 / b_4(D);
  _1 = a_7 % b_4(D);
  if (_1 == 0)
    goto <bb 6>; [89.00%]
  else
    goto <bb 4>; [11.00%]

  <bb 6> [local count: 850510901]:
  goto <bb 3>; [100.00%]

  <bb 4> [local count: 118111600]:
  # a_10 = PHI <a_7(3), a_3(D)(2)>
  return a_10;