[Bug tree-optimization/125707] (~a)>>a should be simplified into -1 for signed types

[kaelfandrew at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125707

--- Comment #2 from Kael Franco <kaelfandrew at gmail dot com> ---
Created attachment 64700
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64700&action=edit
Proposed patch