Gallium3D's Software Rasterizers Are Close To Having OpenGL Tessellation Support

Mesa 20.0 continues getting more interesting with the infrastructure around the Gallium3D LLVM "Gallivm" and TGSI IR now supporting tessellation.

Thanks to Intel's Jan Zielinski, tessellation shader support was wired up for the TGSI IR with Gallivm code. This is one step away from enabling OpenGL tessellation shader support within their OpenSWR software rasterizer.

It's also then just a stone throw away as well from having OpenGL tessellation support flipped on too for LLVMpipe, when using TGSI over its new NIR code-path.

The Intel work was merged over night for Mesa 20.0-devel. ARB_tessellation_shader is mandated by OpenGL 4.0 and is one of the few extensions still left to be supported by SWR/OpenSWR and LLVMpipe for crossing the GL4 milestone. The other work remaining for these drivers are ARB_gpu_shader5 and ARB_sample_shading.

Here's to hoping these OpenGL software rasterizers see full OpenGL 4.0 support in 2020.