Re: [PATCH] Add __builtin_popcountl

[Al Viro <viro@ftp.linux.org.uk>]

On Thu, Oct 26, 2006 at 11:56:00AM -0700, Linus Torvalds wrote:
> 
> 
> On Thu, 26 Oct 2006, Al Viro wrote:
> > 
> > AFAICS, that's way over the top.  That kind of stuff is needed only
> > when builtin can't be described as a normal function.  This, OTOH...
> 
> On the other hand, adding "true" builtin functions is actually a lot 
> cheaper than adding bogus code to be parsed explicitly.
> 
> So I'd actually prefer a way to have a table to describe and initialize 
> these things, as a way to make it a lot more efficient, and without the 
> silly preprocessor buffer hacks..
> 
> The preprocessor hack is certainly simple, but it's not what you really 
> want in real life.

Well...  Keep in mind that those _are_ functions; i.e. unlike something
like __builtin_choose_expr() you can pass such puppy to a function
expecting a callback, etc.

So it's not enough to special-case them; we really need types for those
symbols.  I don't think that it will be more efficient in the end.