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<amartinson at codeweavers.com>  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.