https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113565
--- Comment #5 from Jan Schultke <janschultke at googlemail dot com> ---
You can reproduce this as follows:
> static_assert(__builtin_clz(0u) == 32);
>
> unsigned x = 0;
>
> int main() {
> return __builtin_clz(x);
> }
For base x86_64, GCC emits: (https://godbolt.org/z/nqzYrTWd1)
> main:
> bsr eax, DWORD PTR x[rip]
> xor eax, 31
> ret
> x:
> .zero 4
Even though __builtin_clz(0u) == 32 passes, this program returns 63. This is
obviously not in the interest of the developer, regardless of what the standard
mandates.
