[Bug tree-optimization/126705] `ctz(a*3)` should be simplified into `ctz(a)`

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126705

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
This is an example of what something which is not optimized on aarch64:
```
int f12(unsigned t)
{
    unsigned t1 = t *3;
    if (t1)
      return __builtin_ctz(t*3);
    return 32;
}
```