[FFmpeg-devel] [PATCH] Yet more ALAC cleanup (#define removal)

[Vitor Sessak]

Hi

Aurelien Jacobs wrote:
>>> Reimar D?ffinger wrote:
>>>> On Wed, Aug 15, 2007 at 08:22:59PM +0200, Vitor Sessak wrote:
>>>>> -#define SIGN_ONLY(v) \
>>>>> -                     ((v < 0) ? (-1) : \
>>>>> -                                ((v > 0) ? (1) : \
>>>>> -                                           (0)))
>>>>> +static inline int sign_only(int v)
>>>>> +{
>>>>> +    if (v < 0)
>>>>> +        return -1;
>>>>> +    else if (v > 0)
>>>>> +        return 1;
>>>>> +    else
>>>>> +        return 0;
>>>>> +}
>>>> Since you change it anyway, I'd suggest
>>>> if (v == 0) return 0;
>>>> return FFSIGN(v);
>>>> Though benchmarking it might be a good idea unless it is really
>>>> uncritical.
>>>> Greetings,
>>>> Reimar D?ffinger
>>> Nice suggestion, but I don't think it is worth benchmarking. Unless the 
>>> compiler is very stupid, 
>> anyone did a IQ test with gcc lately?
>>
>> anyway, if you benchmark it, also try
>> (v>>31)-((-v)>>31)
> 
> And maybe also this similar solution:
>   !!v | v>>31


Interestingly, (v>>31)-((-v)>>31) is as fast as the FFSIGN 
implementation and the !!v is slower. I wonder if it's different for 
other architectures/compilers. I propose to apply the patch with the 
FFSIGN (which is easier to read). Ok to apply?

-Vitor