RadeonSI Gets Another Handful Of OpenGL Extensions, Mirroring The PRO Driver's Behavior
Written by Michael Larabel in Mesa on 24 August 2018 at 04:42 AM EDT. 13 Comments
Prolific Mesa contributor Marek Olšák has landed support for more OpenGL / OpenGL ES extensions into the RadeonSI Gallium3D driver.

The latest batch of RadeonSI work merged by the AMD Linux developer overnight includes:

- KHR_texture_compression_astc_sliced_3d for RadeonSI. Marek recently landed the Gallium ASTC texture compression support while KHR_texture_compression_astc_sliced_3d exposes some additional ASTC capabilities.

- EXT_disjoint_timer_query for most Gallium3D drivers including RadeonSI and is exposed for OpenGL ES. EXT_disjoint_timer_query is important for WebGL and provides a means of measuring the duration of a set of OpenGL commands that doesn't block the rendering pipeline.

- EXT_vertex_attrib_64bit support, which is the same as the already supported ARB_vertex_attrib_64bit. Marek is exposing this to match the behavior of the closed-source AMD OpenGL driver. EXT_vertex_attrib_64bit gets flipped on for the Intel driver, Nouveau NVC0, and RadeonSI.

- AMD_query_buffer_object that is a subset of the ARB_query_buffer_object. This too gets flipped on for Intel and Nouveau and even R600g.

- AMD_multi_draw_indirect that matches the behavior of the ARB_multi_draw_indirect extension. This is another case of exposing it since "the PRO GL driver does it."

- AMD_gpu_shader_int64 that is the same as ARB_gpu_shader_int64 but again exposing this vendor extension since the AMDGPU-PRO OpenGL driver exposes it.

- Support for ARB_post_depth_coverage when in the OpenGL compatibility profile mode.

- Yesterday were also several commits by Marek adjusting the maximum capabilities exposed by RadeonSI for different OpenGL features to match what's exposed by the PRO driver.

Long story short, the work now in Mesa Git is namely about trying to hit OpenGL extension parity with the closed-source OpenGL driver and ironing out some of the remaining differences. As shown by yesterday's AMDGPU-PRO vs. All-Open vs. Upstream benchmarks, the PRO OpenGL driver for gaming remains much slower these days than the current Mesa driver stack namely for OpenGL titles with RadeonSI but also in a growing number of Vulkan games with RADV. This latest work by Marek will be part of next quarter's Mesa 18.3 stable release.
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