[Mesa-dev] [PATCH 2/2] Revert "i965: Implement guardband clipping on Ivybridge."

[Oliver McFadden]

On Tue, Oct 02, 2012 at 02:00:40PM +0300, Oliver McFadden wrote:
> This reverts commit 610910a66d1a97ca51ad8a003bdeadfe9563d721.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=55523
> Signed-off-by: Oliver McFadden <oliver.mcfadden at linux.intel.com>
> CC: Kenneth Graunke <kenneth at whitecape.org>
> ---
> v1: note that I have not actually verified this bug exists on IvyBridge, however
> given the severity of the bug (major rendering errors in prominent benchmark
> applications) I believe it's safer to simply revert both on master and all
> stable/release branches.  I am open for discussion on this second patch.
> 
> I have verified that SandyBridge suffers badly from this bug on multiple OpenGL
> ES2.0 programs/benchmarks.

NOTE: This is a candidate for the 9.0 branch.

> 
>  src/mesa/drivers/dri/i965/gen7_clip_state.c     |    1 -
>  src/mesa/drivers/dri/i965/gen7_viewport_state.c |   19 +++++--------------
>  2 files changed, 5 insertions(+), 15 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/gen7_clip_state.c b/src/mesa/drivers/dri/i965/gen7_clip_state.c
> index 3bc6de0..15de042 100644
> --- a/src/mesa/drivers/dri/i965/gen7_clip_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_clip_state.c
> @@ -101,7 +101,6 @@ upload_clip_state(struct brw_context *brw)
>  	     GEN6_CLIP_MODE_NORMAL |
>               nonperspective_barycentric_enable_flag |
>  	     GEN6_CLIP_XY_TEST |
> -	     GEN6_CLIP_GB_TEST |
>  	     userclip << GEN6_USER_CLIP_CLIP_DISTANCES_SHIFT |
>  	     depth_clamp |
>  	     provoking);
> diff --git a/src/mesa/drivers/dri/i965/gen7_viewport_state.c b/src/mesa/drivers/dri/i965/gen7_viewport_state.c
> index 7036ef6..2bcf338 100644
> --- a/src/mesa/drivers/dri/i965/gen7_viewport_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_viewport_state.c
> @@ -43,20 +43,11 @@ gen7_upload_sf_clip_viewport(struct brw_context *brw)
>     /* Also assign to clip.vp_offset in case something uses it. */
>     brw->clip.vp_offset = brw->sf.vp_offset;
>  
> -   /* According to the "Vertex X,Y Clamping and Quantization" section of the
> -    * Strips and Fans documentation, Ivybridge and later don't have a maximum
> -    * post-clamp delta.  However, the guardband extent must fit in [-32K, 32K)
> -    * which gives us a maximum size of 64K.  Use 65000 rather than 65536 to be
> -    * somewhat cautious---make the guardband slightly smaller than the maximum.
> -    */
> -   const float maximum_guardband_extent = 65000;
> -   float gbx = maximum_guardband_extent / (float) ctx->Viewport.Width;
> -   float gby = maximum_guardband_extent / (float) ctx->Viewport.Height;
> -
> -   vp->guardband.xmin = -gbx;
> -   vp->guardband.xmax = gbx;
> -   vp->guardband.ymin = -gby;
> -   vp->guardband.ymax = gby;
> +   /* Disable guardband clipping (see gen6_viewport_state.c for rationale). */
> +   vp->guardband.xmin = -1.0;
> +   vp->guardband.xmax = 1.0;
> +   vp->guardband.ymin = -1.0;
> +   vp->guardband.ymax = 1.0;
>  
>     /* _NEW_BUFFERS */
>     if (render_to_fbo) {
> -- 
> 1.7.8.6
> 

-- 
Oliver McFadden.