[FFmpeg-devel] [PATCH] Remove global mm_flags variable

[Ivan Kalvachev]

On 8/24/10, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Tue, Aug 24, 2010 at 10:39:30PM +0300, Ivan Kalvachev wrote:
>> On 8/24/10, Mans Rullgard <mans at mansr.com> wrote:
>> > -
>> > -#define emms_c() \
>> > -{\
>> > -    if (mm_flags & FF_MM_MMX)\
>> > -        emms();\
>> > -}
>> > +#define emms_c() emms()
>>
>> Michael, are you really OK with that change?
>> The result would be illegal instruction on all pre-MMX CPUs.
>
> who still uses these?
> and how much pre mmx x86 asm do we have? and how much faster is
> that on pre mmx cpus?

I think this is actually taking the issue backwards.
You can build ffmpeg with optimizations for specific cpu. When
building generic one, you would expect to be able to run on any kind
of cpu.

We do have ./configure -cpu= "select the minimum required CPU (affects
selection, may crash on older CPUs)".
I think we should use it.


It's not only matter of convinience, it is also matter of principle.
When you obsolate one class of CPU, doing the same with the next one
would be logical step, going down the slippery slope.

And please don't ask _me_ for patches, I'm not the one breaking it.

Best Regards