[FFmpeg-devel] [PATCH] ARM: NEON optimised simple_idct

Michael Niedermayer michaelni
Mon Aug 25 21:55:11 CEST 2008

On Mon, Aug 25, 2008 at 07:47:16PM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> >2. depending on the pattern of non zero / all zero rows one of 8
> > optimized column transforms is used.  This may be a bad idea though
> > for a CPU with a small code cache ...
> >
> > also maybe it would make sense to look at i386/idct_sse2_xvid.c
> > which uses SSE2 (128bit registers), this one uses only 16bit operations
> > for the column transform so it may be faster when the tricks of the simple
> > idct arent applicable
> Do you expect any sane person to be able to read that?  

well, a little insanity may be needed

> That's also
> not bitexact, right?

it is supposed to be bitexact, and i cannot remember a case where any
input lead to different output. Also the MMX one is used in the
regression tests and they match between MMX and non x86 cpus ...

> > also
> >
> >     Intel 64 and IA-32 Architectures
> >     Software Developers Manual
> >                               Volume 2A (and B)
> >            Instruction Set Reference
> >
> > contains very readable and unambigious explanations of what all the
> > MMX, SSE* instruction do, if you ever want to decypher mmx or sse code
> I have those documents, and reading Chinese is easier.

This is great, so you can help me communicate with zhentan who is a SOC
student and IIRC chinese.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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