i965/blorp: Align rectangle primitive for hiz ops

The hardware docs and the simulator require that the rectangle primitive
emitted during fast depth clears and hiz resolves must be aligned to 8x4
pixels.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>

diff --git a/src/mesa/drivers/dri/i965/brw_blorp.cpp b/src/mesa/drivers/dri/i965/brw_blorp.cpp
index 5f72b5dce194756dd2dcdcd59a25e84a18893b30..ed966c6353f217ca258c87d510752c0d527736ea 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_blorp.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp.cpp
@@ -181,6 +181,35 @@ brw_hiz_op_params::brw_hiz_op_params(struct intel_mipmap_tree *mt,
    this->hiz_op = op;
 
    depth.set(mt, level, layer);
+
+   /* Align the rectangle primitive to 8x4 pixels.
+    *
+    * During fast depth clears, the emitted rectangle primitive  must be
+    * aligned to 8x4 pixels.  From the Ivybridge PRM, Vol 2 Part 1 Section
+    * 11.5.3.1 Depth Buffer Clear (and the matching section in the Sandybridge
+    * PRM):
+    *     If Number of Multisamples is NUMSAMPLES_1, the rectangle must be
+    *     aligned to an 8x4 pixel block relative to the upper left corner
+    *     of the depth buffer [...]
+    *
+    * For hiz resolves, the rectangle must also be 8x4 aligned. Item
+    * WaHizAmbiguate8x4Aligned from the Haswell workarounds page and the
+    * Ivybridge simulator require the alignment.
+    *
+    * To be safe, let's just align the rect for all hiz operations and all
+    * hardware generations.
+    *
+    * However, for some miptree slices of a Z24 texture, emitting an 8x4
+    * aligned rectangle that covers the slice may clobber adjacent slices if
+    * we strictly adhered to the texture alignments specified in the PRM.  The
+    * Ivybridge PRM, Section "Alignment Unit Size", states that
+    * SURFACE_STATE.Surface_Horizontal_Alignment should be 4 for Z24 surfaces,
+    * not 8. But commit 1f112cc increased the alignment from 4 to 8, which
+    * prevents the clobbering.
+    */
+   depth.width = ALIGN(depth.width, 8);
+   depth.height = ALIGN(depth.height, 4);
+
    x1 = depth.width;
    y1 = depth.height;