OpenGL 4.6 Didn't Make It For Mesa 17.3, But It's Getting Close

Next month's Mesa 17.3 release won't have OpenGL 4.6 that debuted this summer, but they are getting close to supporting this latest version of the OpenGL graphics API.

OpenGL 4.6 was released back in July with the big addition being the Vulkan/SPIR-V ingestion support and that's what has held up OpenGL 4.6 from being officially supported by mainline Mesa.

OpenGL 4.6 functionality already supported by Mesa's Intel and RadeonSI drivers include ARB_indirect_parameters, pipeline_statistics_query, polygon_offset_clamp, shader_atomic_counter_ops, shader_draw_parameters, shader_group_vote, ARB_texture_filter_anisotropic, and ARB_transform_feedback_overflow_query. They're mostly just some minor OpenGL additions while having anisotropic filtering support in core Mesa is a notable albeit late addition.

The extensions not yet supported by RadeonSI and Intel i965 are ARB_gl_spirv, KHR_no_error, and ARB_spirv_extensions. KHR_no_error is in effect already supported thanks to all of the work done by Valve developers and others in plumbing this extension to allow for turning off some OpenGL validation/error handling code in the name of lower overhead. The two other extensions are both around SPIR-V and continue to be worked on by the Intel and AMD driver teams.

This OpenGL SPIR-V work is about allowing SPIR-V modules to be used as a shader rather than just GLSL and to allow for GLSL to be used as a source language for creating new SPIR-V modules for OpenGL consumption. This is a big ticket feature and important for better interoperability between Vulkan and OpenGL with allowing the same intermediate representation.

Some of Intel's latest work in this direction can be found via Ian Romanick's emit-spirv branch that is for allowing the i965 driver and Mesa to emit SPIR-V representation for shaders and related work.

AMD's path towards getting RadeonSI SPIR-V support has resulted in pulling in NIR support for code re-use with the NIR/RADV paths and is still working on the ARB_gl_spirv support.

Hopefully we'll see Mesa 18.0 early next year with OpenGL 4.6 support for RadeonSI and Intel i965. The Nouveau NVC0 driver supports most of the OpenGL 4.6 extensions but doesn't yet handle ARB_transform_feedback_overflow_query and there hasn't been any notable SPIR-V work due to lack of manpower and also not having any existing Vulkan/SPIR-V support to work from.