[Mesa-dev] [PATCH 0/3] radeonsi: handle unaligned vertex buffers in hardware

[Nicolai Hähnle]

On 30.04.19 21:20, Marek Olšák wrote:
> Why can we not use tbuffer loads?

tbuffer_load_format has the exact same limitations as 
buffer_load_format. They both use the same hardware path, the only 
difference is that tbuffer_load_format gets the format information from 
the instruction, while buffer_load_format gets it from the resource 
descriptor.

Therefore, in all cases where we *can* use tbuffer_load_format, we may 
as well use buffer_load_format (because we can just initialize the 
descriptor for that vertex input / vertex element correctly).

The benefit that tbuffer_load_format could potentially give us in the 
future is that when multiple vertex elements reference the same vertex 
buffer, we could put a single buffer descriptor into the descriptor 
table (or into USER_SGPRs) instead of having one buffer descriptor for 
every element.

Cheers,
Nicolai


> 
> Marek
> 
> On Thu, Apr 25, 2019 at 7:18 AM Nicolai Hähnle <nhaehnle at gmail.com 
> <mailto:nhaehnle at gmail.com>> wrote:
> 
>     Hi all,
> 
>     the following patches contain code to implement all vertex fetches
>     using plain, non-format loads plus explicit shader arithmetic for
>     format conversion.
> 
>     This allows us to remove the software workaround for unaligned vertex
>     buffers on SI, because we can just load individual bytes on the GPU.
>     CI+ will still use short/dword loads even in the unaligned case.
> 
>     The format conversion code was tested by running with
>     radeonsi_vs_fetch_always_opencode=true on both Verde and Vega.
> 
>     Please review!
> 
>     Thanks,
>     Nicolai
>     --
>       src/amd/common/ac_llvm_build.c               | 313 +++++++++++++++++
>       src/amd/common/ac_llvm_build.h               |  30 ++
>       .../drivers/radeonsi/si_debug_options.h      |   1 +
>       src/gallium/drivers/radeonsi/si_get.c        |   2 +-
>       src/gallium/drivers/radeonsi/si_pipe.h       |   1 +
>       src/gallium/drivers/radeonsi/si_shader.c     | 249 +++++--------
>       src/gallium/drivers/radeonsi/si_shader.h     |  46 +--
>       src/gallium/drivers/radeonsi/si_state.c      | 233 +++++++-----
>       src/gallium/drivers/radeonsi/si_state.h      |  19 +
>       .../drivers/radeonsi/si_state_shaders.c      |  37 +-
>       10 files changed, 645 insertions(+), 286 deletions(-)
> 
> 
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