On Mon, Apr 09, 2018 at 03:00:17AM +0200, Michael Niedermayer wrote: > On Sun, Apr 08, 2018 at 03:33:17PM +0200, Martin Vignali wrote: > > Hello, > > > > Patchs in attach remove mmxext version of shufflebytes2103 and uyvyto422 > > > > Checkasm test show that mmxext version is slower than MMX version > > > > Also disable MMXext for "internal" func : extract_even2 > > (only use by uyvyto422) > > are you testing these functions with real image data in a real image > processing pipeline ? > > synthetic tests would likely not give correct results with non temporal > stores. > in a real processing pipeline the output image will generally not fit in > the L1 cache and will generally not be reused before other things overwrote > the cache. So it should be better not to waste cache for it in the first > place. > But a synthetic test which just repeatly filters a short line will > behave very differently. > Its thus expected that mmx2 performs poorly here in such a synthetic test > but that doesnt say anything about how it performs in a real use case
also IIRC all the really old SIMD code has been benchmarked when it was written in real use cases, so if a function that is favoured is slower thats "strange". And the question should be asked "why" its slower now [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB It is dangerous to be right in matters on which the established authorities are wrong. -- Voltaire
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