[Bug tree-optimization/108341] argument to `__builtin_ctz` should be assumed non-zero

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108341

--- Comment #2 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #1)
> May be an opportunity for Ranger?

Hmmm... I don't think so:

    <bb 2> :
    value.0_1 = (unsigned int) value_4(D);
    _2 = __builtin_ctz (value.0_1);
    r = _2;
    _3 = value_4(D) != 0;
    _7 = (int) _3;
    return _7;

We could add an op1_range operator to class cfn_clz to return nonzero for op1,
but that would only work if we knew _2 to be anything...and have no info on _2.