[Bug tree-optimization/87287] Move signed (x % pow2) == 0 optimization to gimple

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87287

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 44681
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44681&action=edit
gcc9-pr87287.patch

Untested fix.