[Mesa-dev] [PATCH 1/8] mesa: Record transform feedback stride in linker output.

[Kenneth Graunke]

On 12/13/2011 03:35 PM, Paul Berry wrote:
> This patch adds the field gl_transform_feedback_info::BufferStride,
> which records the total number of components (per vertex) that
> transform feedback is being instructed to store in each buffer.  The
> i965 gen6 back-end needs this information in order to set up binding
> tables, and it seems better to have the linker provide this
> information rather than force the back-end to recompute it.
> ---
>  src/glsl/linker.cpp    |    4 +++-
>  src/mesa/main/mtypes.h |    5 +++++
>  2 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
> index b8a7126..5eb2a20 100644
> --- a/src/glsl/linker.cpp
> +++ b/src/glsl/linker.cpp
> @@ -1599,6 +1599,7 @@ tfeedback_decl::store(struct gl_shader_program *prog,
>        info->Outputs[info->NumOutputs].NumComponents = this->vector_elements;
>        info->Outputs[info->NumOutputs].OutputBuffer = buffer;
>        ++info->NumOutputs;
> +      info->BufferStride[buffer] += this->vector_elements;
>     }
>     return true;
>  }
> @@ -1863,7 +1864,8 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
>                       tfeedback_decl *tfeedback_decls)
>  {
>     unsigned total_tfeedback_components = 0;
> -   prog->LinkedTransformFeedback.NumOutputs = 0;
> +   memset(&prog->LinkedTransformFeedback, 0,
> +          sizeof(prog->LinkedTransformFeedback));
>     for (unsigned i = 0; i < num_tfeedback_decls; ++i) {
>        unsigned buffer =
>           prog->TransformFeedback.BufferMode == GL_SEPARATE_ATTRIBS ? i : 0;
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index 1934349..d4c600a 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -1822,6 +1822,11 @@ struct gl_transform_feedback_info {
>        unsigned OutputBuffer;
>        unsigned NumComponents;
>     } Outputs[MAX_PROGRAM_OUTPUTS];
> +
> +   /**
> +    * Number of components stored in each buffer.
> +    */
> +   unsigned BufferStride[MAX_FEEDBACK_ATTRIBS];
>  };
>  
>  /**

I must confess that, looking at this structure alone, I wasn't sure what
the difference between NumComponents (above) and BufferStride was.

But this is definitely useful.  With or without improved comments:
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>