Hi Remi On Fri, May 30, 2025 at 09:58:48AM +0300, Rémi Denis-Courmont wrote: > > > Le 30 mai 2025 03:46:05 GMT+03:00, Michael Niedermayer > <mich...@niedermayer.cc> a écrit : > >On Mon, May 26, 2025 at 11:43:15AM +0300, Rémi Denis-Courmont wrote: > >> > >> > >> Le 26 mai 2025 00:37:08 GMT+03:00, Michael Niedermayer > >> <mich...@niedermayer.cc> a écrit : > >> >Hi Rémi > >> > > >> >On Sat, May 24, 2025 at 07:10:57PM +0300, Rémi Denis-Courmont wrote: > >> >> Le torstaina 22. toukokuuta 2025, 9.32.18 Itä-Euroopan kesäaika Jiawei > >> >> a écrit > >> >> : > >> >> > > The RISC-V autovectorised output looks like it has a warning "Odd > >> >> > > rotation angle" which is not present in the non-autovectorised > >> >> > > output. > >> >> > > >> >> > I found this occured when using '-ffast-math' in RISC-V, also occur in > >> >> > -O3 -ffast-math -fno-tree-vectorize case(much slower due to the > >> >> > -ffast-math)，supplementary more comparison results here: > >> >> > >> > > >> >> Unfortunately, the FFmpeg code is written with x87 semantics in mind. > >> > > >> >I dont remember ever writing code intentionally with x87 semantics. And i > >> >have doubts other people did. > >> > >> It doesn't have to be intentional. FFmpeg was started and mostly developed > >> with x86-32 then x86-64 in mind. It's entirely possible that this happened > >> innocently. > >> > >> Specifically, FFmpeg uses open-code for minimum, maximum, absolute value > >> and so on (see FFMIN, FFMAX, FFABS). They work nicely for integer maths. > >> They also work nicely on x87 with the current set of FPU optimisations, > >> but they differ from IEEE semantics because of NaNs, negative zeros and > >> such. > >> > >> Because of that the compiler will *not* use the native FPU instructions on > >> platforms with native IEEE floats. > > > >replace all FFMIN with fminf() / fmin() where the arguments are float or > >double, assuming that has no ill performance effects >
> That will harm performance on x87, whence fminf() and co are function calls > rather than single instructions. What we actually should do is define > separate macros for integer vs float vs double. ok > > But there are hundreds of use sites to patch. To be bluntly honest, I don't > have the motivation to carry that tedious repetitive work out in my free time. ok, can you review my patch ? thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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