Samuli Suominen posted on Thu, 22 Dec 2011 21:03:41 +0200 as excerpted:

> i'll add USE=neon to use.desc and punt the local descriptions if nobody
> objects
> 
> media-libs/libpng: support ARM NEON cpu instruction set
> media-libs/vo-aacenc: Enable neon cpu instructions
> media-video/ffmpeg: Enables NEON optimizations for arm processors.
> media-video/libav: Enable NEON optimizations for arm processors.
> media-video/vlc: Enables NEON optimizations for arm processors.
> x11-libs/pixman: Enables NEON optimizations for ARM processors.

For users not familiar with the ARM arch, neon is arguably more likely to 
be associated with net-libs/neon.  Certainly that's what I would have 
immediately thought, tho my only familiarity with the library is as a 
dependency that IIRC used to trigger lots of subversion rebuilds, etc 
(now days I don't even have subversion on the system, it's all git, but 
according to equery d, neon is still required by musicbrainz).

As such, to avoid confusion I'd suggest arch-neon or arm-neon (or armneon/
archneon) if it's to be a global flag.

YMMV...

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman