[vlc-devel] [vlc-commits] Avcodec: set the dsp_mask for NEON too

Måns Rullgård mans at mansr.com
Tue Oct 2 00:45:40 CEST 2012

"Rémi Denis-Courmont" <remi at remlab.net> writes:

> Le lundi 1 octobre 2012 17:57:44, Jean-Baptiste Kempf a écrit :
>> > > Avcodec: set the dsp_mask for NEON too
>> > 
>> > Does it actually work now?
>> I think not. But it does not hurt.
> Sure, just being curious.
>> > At VDD, Måns implied there might be some inline
>> > assembler, such that run-time NEON was not (yet) entirely possible.
>> Indeed, and he re-explained it to us on IRC.
>> But at some point, maybe there won't be any inline asm left?
> I guess Android porters need to coax^Wincentivise^Wmotivate Måns to iron the 
> inline assembler out.

There is no ARM inline asm to be ironed out.

Because runtime CPU detection on ARM is not generally possible (some
systems expose a subset of the information we need), we rely on probing
the compiler settings to determine which code to build and use.

Furthermore, even if runtime detection is possible, you still want to
build with the compiler flags best matching the target device.  Compared
to x86, much greater gains are made in plain C code when building for
the actual target hardware rather than something less capable.

Måns Rullgård
mans at mansr.com

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