[Bug middle-end/117169] Missed opportunity to combine sign and bitmask tests

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117169

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
as mentioned GCC is able to handle:
```
int f2(signed char x) { return (x&0x30) || (x & 0x03); }
```

in ifcombine.

Just we don't treat `<0` like the check on the sign bit.