Libraries with NEON backends

[Konstantinos Margaritis]

On 28 March 2011 07:52, Jim Huang <jim.huang at linaro.org> wrote:
> - zlib
>  Using SIMD, we can optimize 'copy / repeat an existing sequence' in
> LZ-style encoding.
>  The reference Intel SSE2 optimization patch is attached in this mail.

Regarding zlib in particular, in 2005 I had done an altivec port of this,
apart from vectorizing Adler32 hashing function (which was ~2x faster than
the C version [1], there are ~6 functions that are worth optimizing -as I found
out during profiling the code. These functions are in deflate.c and
inflate.c iirc,
I have to search for the old tarball, it's here somewhere. Performance increase
was from 20% to 50%, using plain C altivec code. I guess it should be similar
with NEON. IMHO, it's worth it, but:

The problem is the zlib license, it forbids distributing compiled
versions that are modified from the original source, such optimizations
can go in the contrib folder, but it's of little use to the average user.

Konstantinos

[1]: http://www.freevec.org/old/whitepapers/Adler32-Altivec.pdf