[Bug rtl-optimization/127221] (A &mask) + (B & mask) -> (A+B) & mask for unsigned types or no overflow possible for `A+B`

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127221

Drea Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Another way this can show up:
```
unsigned ff2(unsigned f, unsigned m)
{
  unsigned char af = f;
  unsigned char am = m;
  unsigned t = af+am;
  return t;
}
unsigned ff3(unsigned f, unsigned m)
{
  unsigned char af = f;
  unsigned char am = m;
  unsigned char t = af+am;
  return t;
}
```

Here the mask is 0xff for ff2.

Actually wait there is an carry out that I missed.

 But will file a different related bug.