Builtin for consulting value analysis (better ffs() code gen)

[Andrew Cooper]

On 14/03/2024 11:02 am, Florian Weimer wrote:
> * Andrew Cooper via Gcc:
>
>> Anyway - is there a way of doing this that I've managed to overlook?
> Use __builtin_ffs?
>
> I think there's some concern for GCC that some of the alternative x86-64
> implementations do not follow the AMD and Intel behavior.

This is why I'm not asking "please improve the code gen of
__builtin_ffs()".  Its a can of worms I don't expect anyone wants to open.

But in the case that I can do better owing to a narrower scope, I'd like
to do so.

~Andrew