Geometry Shader Support For RadeonSI's NIR Back-End

[bridgman]

https://gallium.readthedocs.io/en/latest/

https://dri.freedesktop.org/docs/gallium/

[stalkerg]

> That said, non-TGSI shaders have been feeding into Gallium3D drivers for at least 6 years (we passed LLVM IR into the r600 and radeonsi drivers to support CLover) and I expect other drivers also have done that in the past.

I think I should refresh my knowledge. But "feeding into Gallium3D" it does not mean convert from TGSI to LLVM IR?

[smitty3268]

Do you? I'd certainly love a link some documentation. Last time I looked for that (3 years ago or something) I only ended up on some Chinese websites where those parts that were in English never went into any kind of detail …

http://lmgtfy.com/?q=mesa+gallium+documentation

Very first link.

It doesn't mention TGSI at all. What it does say, just for a start, is

The Gallium3D Interface

The public interface of a Gallium3D driver is described by the src/gallium/include/*.h header files.

The pipe_context structure (in p_context.h) is an abstract base class with per-context methods for:

• Setting rendering state (texture sampler state, blending state, rasterization state, vertex array info, drawing surfaces, etc.)
• Setting shader state, using the TGSI binary shader representation.
• Vertex array and indexed vertex array drawing.

The p_state.h file defines data structures for things such as:

• Graphics state (blending, texture sampling, rasterization)
• Texture and surface resources
• Vertex array layout

The pipe_screen structure is an abstract base class with context-independent methods for:

• Creating textures (and drawing surfaces)
• Getting "views" into textures
• Hardware queries (number of texture units, max texture size, etc).
• Creating generic memory buffers
• Mapping/unmapping buffers
• Fencing

By abstracting OS and window system services, pipe drivers are portable to other platforms (e.g. embedded devices).

Additional Gallium3D interface information.

[bridgman]

I think I should refresh my knowledge. But "feeding into Gallium3D" it does not mean convert from TGSI to LLVM IR?

It only does for drivers which use an LLVM-based shader compiler, which is probably less than half of the actively maintained drivers.

Other drivers either convert TGSI into the native IR of whatever they are using for a shader compiler (typically something written specifically for that GPU) or directly translate each TGSI operation into native hardware instructions.