Mesa's Rusticl Lands Experimental FP16 OpenCL Support

Mesa's Rust-written OpenCL implementation Rusticl for Gallium3D drivers has now added experimental FP16 to its feature set.

Red Hat's Karol Herbst who has led work on this modern OpenCL implementation that is superior to the former "Clover" Gallium3D state tracker has been tackling FP16 among the latest features. Merged this week for Mesa 23.2's release next quarter is an experimental option for exposing the cl_khr_fp16 extension for FP16 data type support.

Karol commented though in the merge request, "This is most likely very broken, just adding it so we can start looking into issues."

This experimental support currently relies on the RUSTICL_ENABLE=fp16 environment variable being set. Part of the problem for it being experimental and possibly even broken is over the lack of OpenCL conformance test suite (CTS) cases around the FP16 data type. The libclc code also has some missing elements of FP16 support.