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

Ganesh Ajjanagadde gajjanag at mit.edu
Fri Jan 15 00:59:34 CET 2016

On Thu, Jan 14, 2016 at 6:54 PM, Henrik Gramner <henrik at gramner.com> wrote:
> 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.

Thank you.

> 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.

I think it is fine, assuming this bug (and possibly others) are fixed.
It may be good to update/add this to FATE; assuming there is infra for
these kinds of tings.

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

Sorry, it was a needless rant. I was just unhappy with the general
idea to use the macro, and was justifying my own lack of use of it.

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