[Mesa-dev] [PATCH 4/4] i965: use cut index to handle primitive restart when possible

[Ian Romanick]

On 05/13/2012 07:06 AM, Jordan Justen wrote:
> If the primitive restart index and the primitive type can
> be handled by the cut index feature, then use the hardware
> to handle the primitive restart feature.
>
> The VBO module's software handling of primitive restart is
> used as a fall back.
>
> Signed-off-by: Jordan Justen<jordan.l.justen at intel.com>
> ---
>   src/mesa/drivers/dri/i965/brw_primitive_restart.c |   68 ++++++++++++++++++++-
>   1 file changed, 67 insertions(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_primitive_restart.c b/src/mesa/drivers/dri/i965/brw_primitive_restart.c
> index 20a9226..f4c8f4e 100644
> --- a/src/mesa/drivers/dri/i965/brw_primitive_restart.c
> +++ b/src/mesa/drivers/dri/i965/brw_primitive_restart.c
> @@ -31,6 +31,56 @@
>   #include "brw_context.h"
>   #include "brw_draw.h"
>
> +static bool can_cut_index_handle_restart_index(struct gl_context *ctx,
> +                                               const struct _mesa_index_buffer *ib)
> +{
> +   bool cut_index_will_work;
> +
> +   switch (ib->type) {
> +   case GL_UNSIGNED_BYTE:
> +      cut_index_will_work = (ctx->Array.RestartIndex&  0xff) == 0xff;
> +      break;
> +   case GL_UNSIGNED_SHORT:
> +      cut_index_will_work = (ctx->Array.RestartIndex&  0xffff) == 0xffff;
> +      break;
> +   case GL_UNSIGNED_INT:
> +      cut_index_will_work = ctx->Array.RestartIndex == 0xffffffff;
> +      break;
> +   default:
> +      cut_index_will_work = false;
> +      assert(0);
> +   }
> +
> +   return cut_index_will_work;
> +}
> +
> +static bool can_cut_index_handle_prims(struct gl_context *ctx,
> +                                       const struct _mesa_prim *prim,
> +                                       GLuint nr_prims)
> +{
> +   for ( ; nr_prims>  0; nr_prims--) {
> +      switch(prim->mode) {
> +      case GL_POINTS:
> +      case GL_LINES:
> +      case GL_LINE_STRIP:
> +      case GL_TRIANGLES:
> +      case GL_TRIANGLE_STRIP:
> +         /* Cut index supports these primitive types */
> +         break;
> +      default:
> +         /* Cut index does not support these primitive types */
> +      //case GL_LINE_LOOP:
> +      //case GL_TRIANGLE_FAN:
> +      //case GL_QUADS:
> +      //case GL_QUAD_STRIP:
> +      //case GL_POLYGON:
> +         return false;
> +      }
> +   }
> +
> +   return true;
> +}
> +
>   bool brw_handle_primitive_restart(struct gl_context *ctx,
>                                     const struct _mesa_prim *prim,
>                                     GLuint nr_prims,
> @@ -70,7 +120,23 @@ bool brw_handle_primitive_restart(struct gl_context *ctx,
>       */
>      brw->prim_restart.in_progress = true;
>
> -   vbo_sw_primitive_restart(ctx, prim, nr_prims, ib);
> +   if (!can_cut_index_handle_restart_index(ctx, ib)) {
> +      /* The primitive restart index can't be handled, so take
> +       * the software path
> +       */
> +      vbo_sw_primitive_restart(ctx, prim, nr_prims, ib);
> +   } else if (can_cut_index_handle_prims(ctx, prim, nr_prims)) {
> +      /* Cut index should work for primitive restart, so use it
> +       */
> +      brw->prim_restart.enable_cut_index = true;
> +      brw_draw_prims(ctx, prim, nr_prims, ib, GL_FALSE, -1, -1, NULL);
> +      brw->prim_restart.enable_cut_index = false;
> +   } else {
> +      /* Not all the primitive draw modes are supported by the cut index,
> +       * so take the software path
> +       */
> +      vbo_sw_primitive_restart(ctx, prim, nr_prims, ib);
> +   }

I think this is better as

     if (can_cut_index_handle_restart_index(ctx, ib)
         && can_cut_index_handle_prims(ctx, prim, nr_prims)) {
         ...
     } else {
         ...
     }

>      brw->prim_restart.in_progress = false;