[Mesa-dev] [PATCH v2 05/14] i965/gen8: Don't allocate hiz miptree structure

[Jordan Justen]

We now skip allocating a hiz miptree for gen8. Instead, we calculate
the required hiz buffer parameters and allocate a bo directly.

v2:
 * Update hz_height calculation as suggested by Topi

Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
---
 src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 95 +++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
index e3bcd8a..fed35d8 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
@@ -1462,6 +1462,99 @@ intel_gen7_hiz_buf_create(struct brw_context *brw,
 }
 
 
+/**
+ * Helper for intel_miptree_alloc_hiz() that determines the required hiz
+ * buffer dimensions and allocates a bo for the hiz buffer.
+ */
+static struct intel_miptree_aux_buffer *
+intel_gen8_hiz_buf_create(struct brw_context *brw,
+                          struct intel_mipmap_tree *mt)
+{
+   unsigned z_width = mt->logical_width0;
+   unsigned z_height = mt->logical_height0;
+   const unsigned z_depth = mt->logical_depth0;
+   unsigned hz_width, hz_height;
+   struct intel_miptree_aux_buffer *buf = calloc(sizeof(*buf), 1);
+
+   if (!buf)
+      return NULL;
+
+   /* Gen7 PRM Volume 2, Part 1, 11.5.3 "Hierarchical Depth Buffer" documents
+    * adjustments required for Z_Height and Z_Width based on multisampling.
+    */
+   switch(mt->num_samples) {
+   case 0:
+   case 1:
+      break;
+   case 2:
+   case 4:
+      z_width *= 2;
+      z_height *= 2;
+      break;
+   case 8:
+      z_width *= 4;
+      z_height *= 2;
+      break;
+   default:
+      assert(!"Unsupported sample count!");
+   }
+
+   const unsigned vertical_align = 8; /* 'j' in the docs */
+   const unsigned H0 = z_height;
+   const unsigned h0 = ALIGN(H0, vertical_align);
+   const unsigned h1 = ALIGN(minify(H0, 1), vertical_align);
+   const unsigned Z0 = z_depth;
+
+   /* HZ_Width (bytes) = ceiling(Z_Width / 16) * 16 */
+   hz_width = ALIGN(z_width, 16);
+
+   unsigned H_i = H0;
+   unsigned Z_i = Z0;
+   unsigned sum_h_i = 0;
+   unsigned hz_height_3d_sum = 0;
+   for (int level = mt->first_level; level <= mt->last_level; ++level) {
+      unsigned i = level - mt->first_level;
+      unsigned h_i = ALIGN(H_i, vertical_align);
+      /* sum(i=2 to m; h_i) */
+      if (i >= 2) {
+         sum_h_i += h_i;
+      }
+      /* sum(i=0 to m; h_i * max(1, floor(Z_Depth/2**i))) */
+      hz_height_3d_sum += h_i * Z_i;
+      H_i = minify(H_i, 1);
+      Z_i = minify(Z_i, 1);
+   }
+   /* HZ_QPitch = h0 + max(h1, sum(i=2 to m; h_i)) */
+   buf->qpitch = h0 + MAX2(h1, sum_h_i);
+
+   if (mt->target == GL_TEXTURE_3D) {
+      /* (1/2) * sum(i=0 to m; h_i * max(1, floor(Z_Depth/2**i))) */
+      hz_height = CEILING(hz_height_3d_sum, 2);
+   } else {
+      /* HZ_Height (rows) = ceiling( (HZ_QPitch/2)/8) *8 * Z_Depth */
+      hz_height = CEILING(buf->qpitch, 2 * 8) * 8 * Z0;
+      if (mt->target == GL_TEXTURE_CUBE_MAP_ARRAY ||
+          mt->target == GL_TEXTURE_CUBE_MAP) {
+         /* HZ_Height (rows) = ceiling( (HZ_QPitch/2)/8) *8 * 6
+          *
+          * Assumption: the doc meant to multiply by Z_Depth as well.
+          */
+         hz_height *= 6;
+      }
+   }
+
+   unsigned long pitch;
+   uint32_t tiling = I915_TILING_Y;
+   buf->bo = drm_intel_bo_alloc_tiled(brw->bufmgr, "hiz",
+                                      hz_width, hz_height, 1,
+                                      &tiling, &pitch,
+                                      BO_ALLOC_FOR_RENDER);
+   buf->pitch = pitch;
+
+   return buf;
+}
+
+
 static struct intel_miptree_aux_buffer *
 intel_hiz_miptree_buf_create(struct brw_context *brw,
                              struct intel_mipmap_tree *mt)
@@ -1503,6 +1596,8 @@ intel_miptree_alloc_hiz(struct brw_context *brw,
 
    if (brw->gen == 7) {
       mt->hiz_buf = intel_gen7_hiz_buf_create(brw, mt);
+   } else if (brw->gen >= 8) {
+      mt->hiz_buf = intel_gen8_hiz_buf_create(brw, mt);
    } else {
       mt->hiz_buf = intel_hiz_miptree_buf_create(brw, mt);
    }
-- 
2.0.1