[Mesa-dev] [PATCH 2/3] i965: Only do depth resolves prior to clearing when needed

[Kenneth Graunke]

From: Jason Ekstrand <jason at jlekstrand.net>

When changing the clear value, we need to resolve any fast cleared data.

Previously, we were performing resolves on every slice with HiZ enabled.
We only need to resolve slices that a) have fast clear data, and b)
aren't about to be cleared to the new color.  In the latter case, we
were actually doing a resolve, and then a fast clear - when we could
skip both, causing the existing fast cleared area to be updated to the
new clear value for no additional work.

This patch stops using intel_miptree_prepare_access in favor of a more
optimal open coded loop that knows about our clear operation.

v2: (by Ken) Rebase on islification, write a real commit message.

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_clear.c | 39 ++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_clear.c b/src/mesa/drivers/dri/i965/brw_clear.c
index 772d7c33991..0429b3b6f51 100644
--- a/src/mesa/drivers/dri/i965/brw_clear.c
+++ b/src/mesa/drivers/dri/i965/brw_clear.c
@@ -165,9 +165,42 @@ brw_fast_clear_depth(struct gl_context *ctx)
     * flags out of the HiZ buffer into the real depth buffer.
     */
    if (mt->fast_clear_color.f32[0] != ctx->Depth.Clear) {
-      intel_miptree_prepare_access(brw, mt, 0, INTEL_REMAINING_LEVELS,
-                                   0, INTEL_REMAINING_LAYERS,
-                                   ISL_AUX_USAGE_HIZ, false);
+      for (uint32_t level = mt->first_level; level <= mt->last_level; level++) {
+         if (!intel_miptree_level_has_hiz(mt, level))
+            continue;
+
+         const unsigned level_layers = brw_get_num_logical_layers(mt, level);
+
+         for (uint32_t layer = 0; layer < level_layers; layer++) {
+            if (level == depth_irb->mt_level &&
+                layer >= depth_irb->mt_layer &&
+                layer < depth_irb->mt_layer + num_layers) {
+               /* We're going to clear this layer anyway.  Leave it alone. */
+               continue;
+            }
+
+            enum isl_aux_state aux_state =
+               intel_miptree_get_aux_state(mt, level, layer);
+
+            if (aux_state != ISL_AUX_STATE_CLEAR &&
+                aux_state != ISL_AUX_STATE_COMPRESSED_CLEAR) {
+               /* This slice doesn't have any fast-cleared bits. */
+               continue;
+            }
+
+            /* If we got here, then the level may have fast-clear bits that
+             * use the old clear value.  We need to do a depth resolve to get
+             * rid of their use of the clear value before we can change it.
+             * Fortunately, few applications ever change their depth clear
+             * value so this shouldn't happen often.
+             */
+            intel_hiz_exec(brw, mt, level, layer, 1,
+                           BLORP_HIZ_OP_DEPTH_RESOLVE);
+            intel_miptree_set_aux_state(brw, mt, level, layer, 1,
+                                        ISL_AUX_STATE_RESOLVED);
+         }
+      }
+
       mt->fast_clear_color.f32[0] = ctx->Depth.Clear;
    }
 
-- 
2.13.3