[Bug tree-optimization/126523] New: `(si)~(ui)si_var` should be converted into just ~si_var

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126523

            Bug ID: 126523
           Summary: `(si)~(ui)si_var` should be converted into just
                    ~si_var
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, TREE
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
typedef int si;
typedef unsigned ui;

si f(si a)
{
    ui t = a;
    t = ~t;
    si a1 = t;
    return a1;
}

si f1(si a)
{
    return ~a;
}

int g(si a)
{
    return f(a) + f1(a) == (si)(2*(~a));
}
```
g should optimize to 1 which it does on the RTL level