[vlc-devel] commit: contrib: turn off Thumb ISA for libavcodec and libmad ( Rémi Denis-Courmont )

[Måns Rullgård]

Rafaël Carré <rafael.carre at gmail.com> writes:

> On Sat, 29 Aug 2009 22:06:38 +0300
> "Rémi Denis-Courmont" <remi at remlab.net> wrote:
>
>> I guess avcodec uses fancy ASM instructions outside of Thumb-2.
>
> You can't use inline asm when asking GCC to build thumb because you
> don't know if it will use ARM or THUMB instruction set for a specific
> function.
>
> A solution would be to build the files containing inline ARM asm with
> -mno-thumb -mthumb-interwork but you'd have to check every file
>
> Last but not least: thumb is quite limited and considered slower than
> ARM code (note thumb-2 appears to be generally faster than thumb) so
> it's not advised for multimedia routines especially when you have loads
> of memory available and code size doesn't matter that much.

http://hardwarebug.org/2009/03/25/thumbs-up/

-- 
Måns Rullgård
mans at mansr.com