https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101175
--- Comment #4 from Mikael Pettersson <mikpelinux at gmail dot com> ---
(In reply to Uroš Bizjak from comment #3)
> (In reply to Mikael Pettersson from comment #2)
> > (In reply to Iru Cai from comment #0)
> > > Built with '-march=x86-64-v3 -O1', the following code generates a bsr
> > > instruction, which has undefined behavior when the source operand is zero,
> > > thus gives wrong result
> >
> > The documentation for __builtin_clz(x) states "If x is 0, the result is
> > undefined".
>
> The testcase from Comment #0 does:
>
> if (value != 0) {
> return __builtin_clz(value);
Yes I just noticed. My mistake.
