[Mesa-dev] [PATCH 1/2] r600g: Support I2D/U2D/D2I/D2U

[Roland Scheidegger]

Am 11.09.2015 um 05:14 schrieb Dave Airlie:
> On 11 September 2015 at 12:37, Roland Scheidegger <sroland at vmware.com> wrote:
>> Just on a very quick glance, seems somewhat odd this function is named
>> "cypress" whereas the other 64bit ones are named "cayman".
>> In any case, saying enabling support for chips which have hative support
>> isn'quite correct, since there's a couple more which should be able to
>> do it (rv670, rv770, maybe more) as far as I know (no idea though how
>> complex it would be to implement, maybe they are missing some things...)
> 
> probably should say evergreen native,
> 
> I doubt anyone will care about rv670/770, their fp64 support is pretty lacking
> compared to evergreen. We really only care on evergreen because GL4.0,
> and none of the older gpus can do GL4.0
> 

True enough. I'm kind of surprised the blob gets away with the
uber-cheap cheated implementation of the int to double / double to int
conversion, needless to say that probably doesn't get you quite the
results you'd expect and doesn't look very conformant to me... At least
for int to double, a better implementation wouldn't be all that tricky,
just convert upper and lower bits separately and add them back together
(rescaled of course), albeit of course quite a few more instructions.
The reverse probably could work similarly too, but anyway if the blob is
happy with the cheat I guess that's good enough...

Roland