[FFmpeg-devel] [PATCH] lavu/x86/lls: add fma3 optimizations for update_lls

[Henrik Gramner]

On Thu, Jan 14, 2016 at 11:47 PM, Ganesh Ajjanagadde <gajjanag at mit.edu> wrote:
> BTW, this is why I personally don't like the macro:
> so I was moving along, replacing one after the other, till I came to this line
>     vfmadd213pd ymm1, ymm5, COVAR(iq  ,1)
> I naturally replace by
>     fmaddpd ymm1, ymm1, ymm5, COVAR(iq,1)
> giving error "invalid combination of opcode and operand"
> I could spend the time seeing why it is broken, but frankly don't
> care. The point is, the macro is broken, and the lack of documentation
> just bit back.

Then that's a bug and it should be fixed. For the record I gave the
code a quick glance and I'm pretty sure I know what the underlying
problem is, I'll try to make a fix for it when I have the time to do
so.

The documentation basically states that it's an FMA3-emulation of
FMA4-syntax, I'm personally not sure how much there is to expand on
that but if you do have some concrete suggestions on what kind of
documentation would be beneficial feel free to make your voice heard
and maybe someone with knowledge of the code will improve it.

Just complaining that something is absurd and broken and how you don't
care doesn't really accomplish much however.