RadeonSI Driver Switches To NIR, Thereby Enabling OpenGL 4.6 By Default For AMD GPUs

Mesa 20.0 due out in Q1'2020 is now the magical release that is set to switch on RadeonSI NIR usage by default in place of the TGSI intermediate representation. What makes this IR switch-over prominent is that OpenGL 4.6 is then enabled by default on this open-source Gallium3D driver supporting Radeon HD 7000 series GPUs and newer.

Recently in Mesa 20.0-devel, RadeonSI plumbed in OpenGL 4.6 support but it was contingent upon enabling NIR due to sharing some code-paths with the NIR-built RADV Vulkan driver around the SPIR-V code. NIR is the intermediate representation that most Mesa OpenGL/Vulkan drivers are focusing on and is more versatile than the likes of TGSI, the traditional IR of Gallium3D that has been around a decade.

As explained in that earlier article, "RadeonSI has long supported most extensions of OpenGL 4.6 like ARB_indirect_parameters, ARB_shader_draw_parameters, ARB_shader_group_vote, ARB_texture_filter_anisotropic, KHR_no_error, and others, but like the Intel driver had been held up by the ARB_gl_spirv and related ARB_spirv_extensions due to all of that work involved in opening up SPIR-V support to OpenGL drivers."

As shown a few days ago, the RadeonSI NIR performance is now very good and at least in our testing haven't encountered any glaring bugs. As such, AMD's Marek Olšák has now decided to enable this NIR usage by default in Mesa 20.0-devel and thus also providing OpenGL 4.6 out-of-the-box finally for RadeonSI / AMD HD 7000 series and newer. Switching to NIR by default now still gives plenty of time for more widespread testing of habitual Git users for uncovering any corner cases that need to be addressed ahead of the Mesa 20.0 feature freeze and release process.

This is for Mesa 20.0 due out around late February or March and not the Mesa 19.3 release due out any day now. Pull down the latest Mesa Git master to today enjoy this significant change to the open-source RadeonSI driver.