[Bug tree-optimization/111910] `a - b < 0` is not transformed into `a < b` for signed types

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111910

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Also this:
```
int f(int a, int b)
{
        if (a < b) return a - b; else return b - a;
}
int fa(int a, int b)
{
        return (a < b) ? (a - b) : (b - a);
}

int f1(int a, int b)
{
        int t = a - b;
        if (a < b) return t; else return -t;
}


int f2(int a, int b)
{
        int t = a - b;
        if (t < 0) return t; else return -t;
}

int f3a(int a, int b)
{
        return ((a - b) < 0) ? (a - b) : ( b - a);
}

int f3(int a, int b)
{
        int t = a - b;
        return t < 0 ? t : -t;
}
```

(note clang misses on the above for f and fa [f1 on x86_64]).