[Mesa-dev] [RFC PATCH 22/40] i965: Implement fine-grained uniform uploads

[Kenneth Graunke]

On Sunday, January 04, 2015 04:04:36 PM Abdiel Janulgue wrote:
> Determine which shader stage changed their uniforms and only upload
> uniforms which belong to it.
> 
> Signed-off-by: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
> ---
>  src/mesa/drivers/dri/i965/brw_context.h   | 2 ++
>  src/mesa/drivers/dri/i965/brw_program.c   | 9 +++++++++
>  src/mesa/drivers/dri/i965/gen7_vs_state.c | 4 ++++
>  3 files changed, 15 insertions(+)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
> index f384008..6706b4a 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.h
> +++ b/src/mesa/drivers/dri/i965/brw_context.h
> @@ -1357,6 +1357,8 @@ struct brw_context
>        uint32_t next_offset;
>     } constants;
>  
> +   uint64_t uniformstagemap[MAX_UNIFORMS];
> +
>     struct {
>        uint32_t state_offset;
>        uint32_t blend_state_offset;
> diff --git a/src/mesa/drivers/dri/i965/brw_program.c b/src/mesa/drivers/dri/i965/brw_program.c
> index d9a3f05..c1eec8a 100644
> --- a/src/mesa/drivers/dri/i965/brw_program.c
> +++ b/src/mesa/drivers/dri/i965/brw_program.c
> @@ -179,6 +179,14 @@ brwProgramStringNotify(struct gl_context *ctx,
>     return true;
>  }
>  
> +static void
> +brw_uniform_update(struct gl_context *ctx, GLint location)
> +{
> +   struct brw_context *brw = brw_context(ctx);
> +
> +   brw->state.dirty.mesa |= brw->uniformstagemap[location];
> +}
> +
>  void
>  brw_add_texrect_params(struct gl_program *prog)
>  {
> @@ -236,6 +244,7 @@ void brwInitFragProgFuncs( struct dd_function_table *functions )
>  
>     functions->NewShader = brw_new_shader;
>     functions->LinkShader = brw_link_shader;
> +   functions->UniformUpdate = brw_uniform_update;
>  }
>  
>  void
> diff --git a/src/mesa/drivers/dri/i965/gen7_vs_state.c b/src/mesa/drivers/dri/i965/gen7_vs_state.c
> index 85bd56f..269612b 100644
> --- a/src/mesa/drivers/dri/i965/gen7_vs_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_vs_state.c
> @@ -70,6 +70,10 @@ gen7_upload_constant_buffer_data(struct brw_context* brw,
>        _NEW_FRAGMENT_CONSTANTS
>     };
>  
> +   if (!(brw->state.dirty.brw & BRW_NEW_BATCH) &&
> +       (!prog_data->nr_params || !(brw->state.dirty.mesa & const_state_stage[stage_state->stage])))
> +      return;
> +
>     /* If current constant data does not fit in current constant buffer bank,
>      * move to next slot. 
>      */
> 

I'm not a huge fan of how i965-centric this is, nor having a driver hook on
every uniform update.

I think we should just make core Mesa track whether a uniform exists in a
particular stage or not.  My attempt to implement that is here:

http://cgit.freedesktop.org/~kwg/mesa/commit/?id=e4777f6b1baa7b1e32bc376ba140a3e827fb9808

Then in ctx->DriverFlags, I created a new field:

   uint64_t NewUniforms[MESA_SHADER_STAGES];

In update_program_constants, I flagged
   ctx->NewDriverState |= ctx->DriverFlags.NewUniforms[MESA_SHADER_FRAGMENT];
and so on...

in _mesa_uniform, I added:

   for (int i = 0; i < MESA_SHADER_STAGES; i++) {
      if (uni->active[i])
         ctx->NewDriverState |= ctx->DriverFlags.NewUniforms[i];
   }

That may be incomplete, but I think you get the idea.  This is useful generic
infrastructure to have for all drivers, IMO.

--Ken
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