[FFmpeg-devel] [PATCH] runtime cpu detection for emms

[Alex Converse]

2010/8/29 M?ns Rullg?rd <mans at mansr.com>:
> Aurelien Jacobs <aurel at gnuage.org> writes:
>
>> Hi,
>>
>> Recent change to emms() made it the only MMX dependent function which
>> don't support runtime cpu detection.
>> Attached patch restore this feature without the need for a global
>> mm_flags, and without the overhead of a mm_support() call for each
>> emms().
>>
>> Aurel
>>
>> diff --git a/libavcodec/dsputil.h b/libavcodec/dsputil.h
>> index 3b5ca12..1584b89 100644
>> --- a/libavcodec/dsputil.h
>> +++ b/libavcodec/dsputil.h
>> @@ -627,14 +627,9 @@ void ff_mlp_init_x86(DSPContext* c, AVCodecContext *avctx);
>>
>> ?#if HAVE_MMX
>>
>> +extern void (*ff_emms)(void);
>> ?#undef emms_c
>> -
>> -static inline void emms(void)
>> -{
>> - ? ?__asm__ volatile ("emms;":::"memory");
>> -}
>> -
>> -#define emms_c() emms()
>> +#define emms_c() ff_emms()
>>
>> ?#elif ARCH_ARM
>>
>> diff --git a/libavcodec/x86/dsputil_mmx.c b/libavcodec/x86/dsputil_mmx.c
>> index a24ed62..0b7de41 100644
>> --- a/libavcodec/x86/dsputil_mmx.c
>> +++ b/libavcodec/x86/dsputil_mmx.c
>> @@ -228,6 +228,15 @@ DECLARE_ALIGNED(16, const double, ff_pd_2)[2] = { 2.0, 2.0 };
>> ?/***********************************/
>> ?/* standard MMX */
>>
>> +static void emms_null(void) ?{ }
>> +static void emms_mmx(void) ? { __asm__ volatile ("emms;":::"memory"); }
>> +static void emms_init(void)
>> +{
>> + ? ?ff_emms = mm_support() & FF_MM_MMX ? emms_mmx : emms_null;
>> + ? ?ff_emms();
>> +}
>> +void (*ff_emms)(void) = emms_init;
>
> This is worse than the original.
>

Suppose we put emms() in the DSP context and put the onus of calling
it on codecs that actually use MMX accelerated video functions?