[Bug tree-optimization/103509] New: ((-1u >> t) & b) != 0 is not optimized to b != 0

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103509

            Bug ID: 103509
           Summary: ((-1u >> t) & b) != 0 is not optimized to b != 0
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
bool f1(bool a, int t)
{
    unsigned tt = -1;
    tt >>= t;
    return (a&tt) != 0;
}

bool f2(bool a, int t)
{
    unsigned tt = -1;
    tt >>= t;
    return (tt) != 0;
}
As shown by the above, we know that (-1u>>t)!=0 is always true Therefore we
should be able to optimize f1 to just a!=0