[Ffmpeg-devel] [PATCH] SSE counterpart of ff_imdct_calc_3dn2

[Rich Felker]

On Thu, Aug 24, 2006 at 11:16:19PM +0300, Uoti Urpala wrote:
> On Thu, 2006-08-24 at 13:28 -0400, Rich Felker wrote:
> > On Thu, Aug 24, 2006 at 07:47:12PM +0300, Uoti Urpala wrote:
> > > On Thu, 2006-08-24 at 12:15 -0400, Rich Felker wrote:
> > > > disabled.. Any viable compiler for high-performance needs to have full
> > > > inline asm available, not just a limited set of intrinsics for vector
> > > > ops.
> > > 
> > > Not necessarily, and certainly not gcc-compatible inline asm. How many
> > > asm routines are there in FFmpeg or MPlayer that could not achieve
> > > comparable speed with intrinsics only?
> > 
> > s/comparable/same or better/. 1-5% slowdown is not acceptable. And
> > with this correction I suspect the answer is _NONE_.
> 
> I don't know whether 1% slowdowns would occur (and apparently you don't
> know either), but I don't consider that unacceptable anyway. Bigger
> speedups than 1% are rather easy to achieve on a particular platform.

Then by all means do it...

> Didn't some of the workarounds for old gcc versions cause slowdowns in
> that range?

At worst they caused a 1% slowdown in a portion of the code that uses
maybe 5% of the overall cpu time, not a 1% overall slowdown, IIRC.

Rich