[Intel-gfx] [PATCH 0/3] Support 64 bpp half float formats

Strasser, Kevin kevin.strasser at intel.com
Thu Nov 29 21:39:52 UTC 2018

Ville Syrjälä wrote:
> On Wed, Nov 28, 2018 at 10:38:10PM -0800, Kevin Strasser wrote:
>> This series defines new formats and adds a plane property to be used for
>> floating point framebuffer content. Implementation is then added to i915.
>> I have shared an IGT branch which adds test coverage for the new formats:
>>   https://github.com/strassek/xorg-intel-gpu-tools/tree/fp16
> Looks about similar as what I had written. I wrote my half<->full
> conversion thing from scratch which probably means it has more rounding
> errors and whatnot. The speed of mine wasn't exactly stellar and looks
> like your version probably has the same issue. So I was actually
> thinking of using the sse<something> instructions meant for this
> could provide a nice speedup. I guess we might want the pure c version
> as a backup though. Hmm. Now I also seem to recall that I noticed
> there being a compiler intrinsic even for single value half<->full
> precision conversion. Did you look into using that (if I didn't imagine
> it)?

You are thinking of vcvtps2ph and vcvtph2ps, I haven't yet had a chance to 
give them a try, but I agree it seems like a good idea.

> BTW I just rebased my fp16 for pre-icl platforms:
> git://github.com/vsyrjala/linux.git fp16_scanout_2
> Apart from the ivb/hsw w/a there isn't all that much unexpected
> when it comes to fp16 on those platforms either.

I don't mean to step on your toes with this series, were you waiting for /  
working on a real usecase before pushing that code?


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