[libav-devel] prores micro-opt suggestion

[Janne Grunau]

On Thu, Nov 24, 2011 at 12:03:58PM +0100, Robert Nagy wrote:
> Just scrolling through the prores code. And found a possible minor
> optimization. Don't have a setup for compiling right now so I can't measure
> the perf diff.
> 
> In static inline int decode_vlc_codeword(GetBitContext *gb, uint8_t
> codebook)
> 
> Replace:
> 
> > log = 31 - av_log2(buf)  /* count prefix bits (zeroes) */
> 
> with something like:
> 
> > #ifdef X86
> >#define NLZ(x) // use BSR instruction

see how av_log2 is defined: this will only add clutter and won't be
faster

Janne