[Bug target/127502] `neg (a ? x : 0)` -> (a ? -x : 0) not happening on the rtl level

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127502

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
LLVM's Canonical form is with the neg afterwards from what I can tell.


A few more testcases:
```

signed
f_ (signed x, signed tt)
{
    int t = 0;
    if (tt != 10)
      t = x;
    return -t;
}

signed
f_1 (signed x, signed tt)
{
    int t = 0;
    if (tt != 10)
      t = -x;
    return t;
}
```

For -O1, f_1 is done as csneg while f_2 is not.