Mesa's LLVMpipe Software OpenGL Driver Now Uses NIR By Default

Joining the NIR driver bandwagon recently was LLVMpipe adding support for this new intermediate representation. Now with that support having matured, Mesa 20.0-devel's LLVMpipe software OpenGL driver is switching to NIR by default in place of TGSI.

As of today, David Airlie switched LLVMpipe over to using NIR by default rather than Gallium3D's default IR format, TGSI. The TGSI code-path can still be activated via the LP_DEBUG=tgsi_ir environment variable.

NIR is the intermediate representation most of Mesa's OpenGL and Vulkan drivers have been migrating to for being a modern IR designed for today's APIs and also allowing for greater code sharing between these drivers and optimization passes, among other design improvements over older IRs like TGSI.

I've been meaning to run some fresh LLVMpipe vs. OpenSWR software rasterizer benchmarks on an AMD EPYC Rome 2P box, so this is a great opportunity for some fun holiday benchmarking... Stay tuned and this change will formally be introduced when Mesa 20.0 goes stable around the end of February.