[Bug tree-optimization/96929] Failure to optimize right shift of -1 to -1

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96929

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 49603
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49603&action=edit
gcc11-pr96929.patch

Untested fix.