iris should use native 3D sampler support for planar images
iris currently relies on st/mesa to perform fallbacks for YUV format sampling:
/* Rely on gallium fallbacks for better YUV format support. */
if (util_format_is_yuv(pformat))
return false;
Skylake and later hardware supposedly support native planar image sampling (though not YUV colorspace conversion IIRC), so we ought to be able to sample from planar formats using a single message rather than emulating it via multiple messages. This may also have cache impacts as well. It would probably be faster.
Currently we have no plans to work on this, but it could be done. I am not certain whether anv uses this sampler feature or not.