[Bug middle-end/82853] Optimize x % 3 == 0 without modulo

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82853

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #25 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 44657
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44657&action=edit
gcc9-pr82853.patch

Full untested patch.  For x % C1 == C2 it handles all unsigned cases where C1
is odd, if C1 is even, just cases where C2 <= -1U % C1, if signed modulo, just
x % C1 == 0 cases (where C1 is not INT_MIN).