[Mesa-dev] [PATCH V2 10/10] i965/Gen7: Allow CMS layout for multisample textures

[Anuj Phogat]

On Sat, Nov 30, 2013 at 3:30 PM, Chris Forbes <chrisf at ijw.co.nz> wrote:
> Now that all the pieces are in place, this should provide
> a nice performance boost for apps using multisample textures.
>
> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
> ---
>  src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 18 +-----------------
>  1 file changed, 1 insertion(+), 17 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> index 4a389b9..165cc6b 100644
> --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> @@ -99,23 +99,7 @@ intel_compute_msaa_layout(struct brw_context *brw, gl_format format, GLenum targ
>           assert(brw->gen == 7);
>           return INTEL_MSAA_LAYOUT_UMS;
>        } else {
> -         /* For now, if we're going to be texturing from this surface,
> -          * force UMS, so that the shader doesn't have to do different things
> -          * based on whether there's a multisample control surface needing sampled first.
> -          * We can't just blindly read the MCS surface in all cases because:
> -          *
> -          * From the Ivy Bridge PRM, Vol4 Part1 p77 ("MCS Enable"):
> -          *
> -          *    If this field is disabled and the sampling engine <ld_mcs> message
> -          *    is issued on this surface, the MCS surface may be accessed. Software
> -          *    must ensure that the surface is defined to avoid GTT errors.
> -          */
> -         if (target == GL_TEXTURE_2D_MULTISAMPLE ||
> -             target == GL_TEXTURE_2D_MULTISAMPLE_ARRAY) {
> -            return INTEL_MSAA_LAYOUT_UMS;
> -         } else {
> -            return INTEL_MSAA_LAYOUT_CMS;
> -         }
> +         return INTEL_MSAA_LAYOUT_CMS;
>        }
>     }
>  }
> --
> 1.8.4.2
>
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I noticed this issue last week and reported on IRC:
This commit (83b83fb on mesa master) causes the
arb_sample_shading-builtin-gl-sample-id test to fail on IVB.
I haven't tested on HSW. Raised a bug to keep track of issue:
https://bugs.freedesktop.org/show_bug.cgi?id=72859