Re: wineport: Add fast builtin & asm versions of ffs() + ctz() where supported.

[Adam Martinson]

On 03/11/2011 07:28 AM, Alexandre Julliard wrote:
> Adam Martinson  writes:
> > @@ -236,7 +241,40 @@ extern int getopt_long_only (int ___argc, char *const *___argv,
> >   #endif  /* HAVE_GETOPT_LONG */
> >
> > #ifndef HAVE_FFS
> > -int ffs( int x );
> > - #if defined(__i386__) || defined(__x86_64__)
> > -
> >    #define HAVE_FFS
> > -
> >    static inline int ffs( int x )
> > -
> >    {
> > -
> >        if (!x)
> > -
> >        {
> > -
> >            return 0;
> > -
> >        }
> > -
> >        else
> > -
> >        {
> > -
> >            int ret;
> > -
> >            __asm__("bsfl %1, %0; incl %0" : "=r" (ret) : "r" (x));
> > -
> >            return ret;
> > -
> >        }
> > -
> >    }
> > - #elif defined(__GNUC__)&&  GCC_VERSION>= 29503
> > -
> >    #define HAVE_FFS
> > -
> >    #define ffs(x) __builtin_ffs(x)
> > - #else
> > -
> >    int ffs( int x );
> > - #endif
> >
> > +#endif
>
> You'd have to show benchmarks to prove that this complexity is
> necessary. Given that ffs() should already be inlined on all decent
> platforms, I doubt you'd be able to demonstrate a difference (if
> anything, your version would be slower because of the extra increment).

I did this because it was easy and I was doing ctz() anyhow; I don't 
actually need these versions of ffs() for anything.  On any system with 
HAVE_FFS the system version takes precedence.