i965: Fix fast depth clears for surfaces with a dimension of 16384.

I hadn't bothered to set this bit because I figured it would just
paper over us getting the rectangle wrong.  But it turns out that
there is a legitimate reason to use it, so let's do so.

The alternative would be to chop up 16k clears to multiple 8k clears,
which is pointlessly painful.

Cc: "17.0" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
(cherry picked from commit 5106df85da)

src/mesa/drivers/dri/i965/gen8_depth_state.c

@@ -477,6 +477,18 @@ gen8_hiz_exec(struct brw_context *brw, struct intel_mipmap_tree *mt,
       break;
    case BLORP_HIZ_OP_DEPTH_CLEAR:
       dw1 |= GEN8_WM_HZ_DEPTH_CLEAR;
+
+      /* The "Clear Rectangle X Max" (and Y Max) fields are exclusive,
+       * rather than inclusive, and limited to 16383.  This means that
+       * for a 16384x16384 render target, we would miss the last row
+       * or column of pixels along the edge.
+       *
+       * To work around this, we have to set the "Full Surface Depth
+       * and Stencil Clear" bit.  We can do this in all cases because
+       * we always clear the full rectangle anyway.  We'll need to
+       * change this if we ever add scissored clear support.
+       */
+      dw1 |= GEN8_WM_HZ_FULL_SURFACE_DEPTH_CLEAR;
       break;
    case BLORP_HIZ_OP_NONE:
       unreachable("Should not get here.");