[FFmpeg-devel] [PATCH]HE-AACv1 try 3 (all missing functionality added)

Michael Niedermayer michaelni
Sat Feb 13 17:42:39 CET 2010

On Sat, Feb 13, 2010 at 05:31:59PM +0100, Vitor Sessak wrote:
>> +
>> +static void vector_fmul_scalar_fadd_scalar_c(float *dst, const float 
>> *src,
>> +                                             float mul, float add, int 
>> len)
>> +{
>> +    int i;
>> +    for (i = 0; i < len; i++)
>> +        dst[i] = src[i] * mul + add;
>> +}
>> +
> Did you benchmark if hand-unrolling these loops give any benefit? You know 
> that len is a multiple of four, but the compiler don't.

assert(len>0 && len%4==0);
then the compiler knows it too :)
and after you looked at what gcc generates if forced to unroll
(theres a flag for that IIRC)
then post a code pessimization bug to the gcc-devels
-> only way to see gcc get better at these things


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Frequently ignored awnser#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
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