[FFmpeg-devel] [PATCH 1/2] x86inc: Extend FMA_INSTR functionality
jamrial at gmail.com
Sat Feb 15 20:05:34 CET 2014
On 14/02/14 10:46 PM, Michael Niedermayer wrote:
> On Fri, Feb 14, 2014 at 11:50:15AM -0300, James Almer wrote:
>> On 14/02/14 5:57 AM, Christophe Gisquet wrote:
>>> 2014-02-13 James Almer <jamrial at gmail.com>:
>>>> You're right, a fifth parameter is probably the proper way. See
>>>> FMULADD_PS in x86util. It would allow actual non-destructive emulation
>>>> of these XOP instructions if it's ever needed.
>>>> It's not for now, but changing it will not hurt and it will probably have
>>>> to be done at some point anyway.
>>> You can probably make it optional (haven't looked at FMULADD_PS), ie
>>> make the macro use 4-8 arguments, and if %0 == 8, use %8, otherwise
>>> use %2.
>> Someone else committed the opposite to x264, making the %1 = %2 * %3 + %1 case
>> unsupported instead, so I'm not sure at this point if this should be on x86inc
>> or added as a local macro on a given asm file like i originally did.
> <michaelni> Skyler_, should i revert 23a8c63452009df21b3f184936b343593d4ccb04 (x86inc: Extend FMA_INSTR functionality) and apply "Warn about not supported emulation of some XOP instructions. Also add pmacsdql emulation." from x264 ?
> <michaelni> i think it would be best if a 5th argument, that is a temporary for emulation could be specified
> <Skyler_> yeah, that might be a better solution than both, but in that case we should move it out of x86inc and into x86util and capitalize it
> <Skyler_> because its semantics don't match the original instruction
> <Skyler_> e.g. like PALIGNR vs palignr
Sounds good to me.
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