The LLVMpipe CPU-based software rasterizer OpenGL driver within Mesa's Gallium3D now has working tessellation shader support (ARB_tessellation_shader) and can even run Unigine Heaven demo properly, just don't expect good performance.

This LLVMpipe tessellation shader support is based on code pulled in from Microsoft's open-source tessellator designed for Direct3D. That Microsoft tessellator was pulled into Mesa last year by Intel's OpenSWR team and now wired up for LLVMpipe. The LLVMpipe tessellation code-path does also depend upon the recent work adding NIR intermediate representation support to LLVMpipe as opposed to the traditional TGSI.

This LLVMpipe tessellation shader support passes most Piglit and dEQP tests and can even render tessellation-heavy Unigine Heaven correctly, but don't expect good performance out of the CPU-based rendering.

The work was merged today into the Mesa 20.1 code-base.