[Bug tree-optimization/101591] New: (a|b) ==/!= a -> (b & ~a) ==/!= 0 on gimple

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101591

            Bug ID: 101591
           Summary: (a|b) ==/!= a -> (b & ~a) ==/!= 0 on gimple
           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 f(unsigned a, unsigned b)
{
    return (a|b) == a;
}

This should be optimized to:
bool f(unsigned a, unsigned b)
{
    return (b & ~a) ==/!= 0;
}

It might be only best if you we do for constant b's though.