[Mesa-dev] [PATCH] i965: Advertise 65536 for GL_MAX_UNIFORM_BLOCK_SIZE.

[Ian Romanick]

On 09/08/2015 06:04 PM, Kenneth Graunke wrote:
> Our old value of 16384 is the minimum value.  DirectX apparently
> requires 65536 at a minimum; that's also what nVidia and the Intel
> Windows driver advertise.  AMD advertises MAX_INT.
> 
> Ilia Mirkin noticed that "Shadow Warrior" uses UBOs larger than 16k
> on Nouveau, which advertises 65536 bytes for this limit.  Traces
> captured on Nouveau don't work on i965 because our lower limit causes
> the GLSL linker to reject the captured shaders.  While this isn't
> important in and of itself, it does suggest that raising the limit
> would be beneficial.
> 
> We can read linear buffers up to 2^27 bytes in size, so raising this
> should be safe; we could probably even go larger.  For now, matching
> nVidia and Intel/Windows seems like a good plan.
> 
> We have to reinitialize MaxCombinedUniformComponents as core Mesa will
> have set it based on a stale value for MaxUniformBlockSize.
> 
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/brw_context.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
> index 907b2a0..7c1c133 100644
> --- a/src/mesa/drivers/dri/i965/brw_context.c
> +++ b/src/mesa/drivers/dri/i965/brw_context.c
> @@ -323,6 +323,15 @@ brw_initialize_context_constants(struct brw_context *brw)
>  
>     ctx->Const.StripTextureBorder = true;
>  
> +   ctx->Const.MaxUniformBlockSize = 65536;
> +   for (int i = 0; i < MESA_SHADER_STAGES; i++) {
> +      struct gl_program_constants *prog = &ctx->Const.Program[i];
> +      prog->MaxUniformBlocks = 12;

Is this actually necessary?  It looks like this is that value already
set in init_program_limits.  Either way, this patch is

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

> +      prog->MaxCombinedUniformComponents =
> +         prog->MaxUniformComponents +
> +         ctx->Const.MaxUniformBlockSize / 4 * prog->MaxUniformBlocks;
> +   }
> +
>     ctx->Const.MaxDualSourceDrawBuffers = 1;
>     ctx->Const.MaxDrawBuffers = BRW_MAX_DRAW_BUFFERS;
>     ctx->Const.Program[MESA_SHADER_FRAGMENT].MaxTextureImageUnits = max_samplers;
>