[Mesa-dev] [PATCH v3 18/18] anv/cmd_buffer: Avoid unnecessary transitions before fast clears

[Jason Ekstrand]

Previously, we would always apply the layout transition at the beginning
of the subpass and then do the clear whether fast or slow.  This meant
that there were some cases, specifically when the initial layout is
VK_IMAGE_LAYOUT_UNDEFINED, where we would end up doing a fast-clear or
ambiguate followed immediately by a fast-clear.  This probably isn't
terribly expensive, but it is a waste that we can avoid easily enough
now that we're doing everything at the same time in begin_subpass.
---
 src/intel/vulkan/genX_cmd_buffer.c | 62 +++++++++++++++++++++++---------------
 1 file changed, 38 insertions(+), 24 deletions(-)

diff --git a/src/intel/vulkan/genX_cmd_buffer.c b/src/intel/vulkan/genX_cmd_buffer.c
index 7f06441..453aea8 100644
--- a/src/intel/vulkan/genX_cmd_buffer.c
+++ b/src/intel/vulkan/genX_cmd_buffer.c
@@ -3335,6 +3335,12 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
          target_layout = subpass->attachments[i].layout;
       }
 
+      /* Clears are based on the image view for 3D surfaces but transitions
+       * are done on an entire miplevel at a time.
+       */
+      uint32_t base_clear_layer = iview->planes[0].isl.base_array_layer;
+      uint32_t clear_layer_count = fb->layers;
+
       if (image->aspects & VK_IMAGE_ASPECT_ANY_COLOR_BIT_ANV) {
          assert(image->aspects == VK_IMAGE_ASPECT_COLOR_BIT);
 
@@ -3348,30 +3354,8 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
             layer_count = fb->layers;
          }
 
-         transition_color_buffer(cmd_buffer, image, VK_IMAGE_ASPECT_COLOR_BIT,
-                                 iview->planes[0].isl.base_level, 1,
-                                 base_layer, layer_count,
-                                 att_state->current_layout, target_layout);
-      } else if (image->aspects & VK_IMAGE_ASPECT_DEPTH_BIT) {
-         transition_depth_buffer(cmd_buffer, image,
-                                 att_state->current_layout, target_layout);
-         att_state->aux_usage =
-            anv_layout_to_aux_usage(&cmd_buffer->device->info, image,
-                                    VK_IMAGE_ASPECT_DEPTH_BIT, target_layout);
-      }
-      att_state->current_layout = target_layout;
-
-      if (att_state->pending_clear_aspects & VK_IMAGE_ASPECT_COLOR_BIT) {
-         assert(att_state->pending_clear_aspects == VK_IMAGE_ASPECT_COLOR_BIT);
-
-         /* Multi-planar images are not supported as attachments */
-         assert(image->aspects == VK_IMAGE_ASPECT_COLOR_BIT);
-         assert(image->n_planes == 1);
-
-         uint32_t base_clear_layer = iview->planes[0].isl.base_array_layer;
-         uint32_t clear_layer_count = fb->layers;
-
-         if (att_state->fast_clear) {
+         if ((att_state->pending_clear_aspects & VK_IMAGE_ASPECT_COLOR_BIT) &&
+             att_state->fast_clear) {
             /* We only support fast-clears on the first layer */
             assert(iview->planes[0].isl.base_level == 0);
             assert(iview->planes[0].isl.base_array_layer == 0);
@@ -3381,6 +3365,13 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
             base_clear_layer++;
             clear_layer_count--;
 
+            /* Performing a fast clear takes care of all our transition needs
+             * for the first slice.  Increment the base layer and layer count
+             * so that later transitions don't touch layer 0.
+             */
+            base_layer++;
+            layer_count--;
+
             genX(copy_fast_clear_dwords)(cmd_buffer, att_state->color.state,
                                          image, VK_IMAGE_ASPECT_COLOR_BIT,
                                          true /* copy from ss */);
@@ -3401,6 +3392,29 @@ cmd_buffer_begin_subpass(struct anv_cmd_buffer *cmd_buffer,
             }
          }
 
+         if (layer_count > 0) {
+            transition_color_buffer(cmd_buffer, image,
+                                    VK_IMAGE_ASPECT_COLOR_BIT,
+                                    iview->planes[0].isl.base_level, 1,
+                                    base_layer, layer_count,
+                                    att_state->current_layout, target_layout);
+         }
+      } else if (image->aspects & VK_IMAGE_ASPECT_DEPTH_BIT) {
+         transition_depth_buffer(cmd_buffer, image,
+                                 att_state->current_layout, target_layout);
+         att_state->aux_usage =
+            anv_layout_to_aux_usage(&cmd_buffer->device->info, image,
+                                    VK_IMAGE_ASPECT_DEPTH_BIT, target_layout);
+      }
+      att_state->current_layout = target_layout;
+
+      if (att_state->pending_clear_aspects & VK_IMAGE_ASPECT_COLOR_BIT) {
+         assert(att_state->pending_clear_aspects == VK_IMAGE_ASPECT_COLOR_BIT);
+
+         /* Multi-planar images are not supported as attachments */
+         assert(image->aspects == VK_IMAGE_ASPECT_COLOR_BIT);
+         assert(image->n_planes == 1);
+
          if (clear_layer_count > 0) {
             assert(image->n_planes == 1);
             anv_image_clear_color(cmd_buffer, image, VK_IMAGE_ASPECT_COLOR_BIT,
-- 
2.5.0.400.gff86faf