anv: Use blorp_ccs_ambiguate instead of fast-clears

Even though the blorp pass looks a bit on the sketchy side, the end
result in the Vulkan driver is very nice.  Instead of having this weird
case where you do a fast clear and then maybe have to resolve, we just
do the ambiguate and are done with it.  The ambiguate does exactly what
we want of setting all the CCS values to 0 which puts it into the
pass-through state.

This should also improve performance a bit in certain cases.  For
instance, if we did a transition from UNDEFINED to GENERAL for a surface
that doesn't have CCS enabled all the time, we would end up doing a
fast-clear and then a full resolve which ends up touching every byte in
the main surface as well as the CCS.  With the ambiguate pass, that
transition only touches the CCS.

Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>

2 files changed, 40 insertions, 50 deletions

diff --git a/src/intel/vulkan/anv_blorp.c b/src/intel/vulkan/anv_blorp.c
index 012cb073a4..497ae6fd49 100644
--- a/src/intel/vulkan/anv_blorp.c
+++ b/src/intel/vulkan/anv_blorp.c
@@ -1793,6 +1793,11 @@ anv_image_ccs_op(struct anv_cmd_buffer *cmd_buffer,
                         surf.surf->format, isl_to_blorp_fast_clear_op(ccs_op));
       break;
    case ISL_AUX_OP_AMBIGUATE:
+      for (uint32_t a = 0; a < layer_count; a++) {
+         const uint32_t layer = base_layer + a;
+         blorp_ccs_ambiguate(&batch, &surf, level, layer);
+      }
+      break;
    default:
       unreachable("Unsupported CCS operation");
    }
diff --git a/src/intel/vulkan/genX_cmd_buffer.c b/src/intel/vulkan/genX_cmd_buffer.c
index 39f93c44d9..6d2e282b51 100644
--- a/src/intel/vulkan/genX_cmd_buffer.c
+++ b/src/intel/vulkan/genX_cmd_buffer.c
@@ -486,15 +486,6 @@ init_fast_clear_state_entry(struct anv_cmd_buffer *cmd_buffer,
    uint32_t plane = anv_image_aspect_to_plane(image->aspects, aspect);
    enum isl_aux_usage aux_usage = image->planes[plane].aux_usage;
 
-   /* The resolve flag should updated to signify that fast-clear/compression
-    * data needs to be removed when leaving the undefined layout. Such data
-    * may need to be removed if it would cause accesses to the color buffer
-    * to return incorrect data. The fast clear data in CCS_D buffers should
-    * be removed because CCS_D isn't enabled all the time.
-    */
-   genX(set_image_needs_resolve)(cmd_buffer, image, aspect, level,
-                                 aux_usage == ISL_AUX_USAGE_NONE);
-
    /* The fast clear value dword(s) will be copied into a surface state object.
     * Ensure that the restrictions of the fields in the dword(s) are followed.
     *
@@ -677,31 +668,51 @@ transition_color_buffer(struct anv_cmd_buffer *cmd_buffer,
       for (unsigned level = base_level; level < last_level_num; level++)
          init_fast_clear_state_entry(cmd_buffer, image, aspect, level);
 
-      /* Initialize the aux buffers to enable correct rendering. This operation
-       * requires up to two steps: one to rid the aux buffer of data that may
-       * cause GPU hangs, and another to ensure that writes done without aux
-       * will be visible to reads done with aux.
+      /* Initialize the aux buffers to enable correct rendering.  In order to
+       * ensure that things such as storage images work correctly, aux buffers
+       * need to be initialized to valid data.
+       *
+       * Having an aux buffer with invalid data is a problem for two reasons:
+       *
+       *  1) Having an invalid value in the buffer can confuse the hardware.
+       *     For instance, with CCS_E on SKL, a two-bit CCS value of 2 is
+       *     invalid and leads to the hardware doing strange things.  It
+       *     doesn't hang as far as we can tell but rendering corruption can
+       *     occur.
+       *
+       *  2) If this transition is into the GENERAL layout and we then use the
+       *     image as a storage image, then we must have the aux buffer in the
+       *     pass-through state so that, if we then go to texture from the
+       *     image, we get the results of our storage image writes and not the
+       *     fast clear color or other random data.
        *
-       * Having an aux buffer with invalid data is possible for CCS buffers
-       * SKL+ and for MCS buffers with certain sample counts (2x and 8x). One
-       * easy way to get to a valid state is to fast-clear the specified range.
+       * For CCS both of the problems above are real demonstrable issues.  In
+       * that case, the only thing we can do is to perform an ambiguate to
+       * transition the aux surface into the pass-through state.
        *
-       * Even for MCS buffers that have sample counts that don't require
-       * certain bits to be reserved (4x and 8x), we're unsure if the hardware
-       * will be okay with the sample mappings given by the undefined buffer.
-       * We don't have any data to show that this is a problem, but we want to
-       * avoid causing difficult-to-debug problems.
+       * For MCS, (2) is never an issue because we don't support multisampled
+       * storage images.  In theory, issue (1) is a problem with MCS but we've
+       * never seen it in the wild.  For 4x and 16x, all bit patters could, in
+       * theory, be interpreted as something but we don't know that all bit
+       * patterns are actually valid.  For 2x and 8x, you could easily end up
+       * with the MCS referring to an invalid plane because not all bits of
+       * the MCS value are actually used.  Even though we've never seen issues
+       * in the wild, it's best to play it safe and initialize the MCS.  We
+       * can use a fast-clear for MCS because we only ever touch from render
+       * and texture (no image load store).
        */
-      if (GEN_GEN >= 9 && image->samples == 1) {
+      if (image->samples == 1) {
          for (uint32_t l = 0; l < level_count; l++) {
             const uint32_t level = base_level + l;
             const uint32_t level_layer_count =
                MIN2(layer_count, anv_image_aux_layers(image, aspect, level));
             anv_image_ccs_op(cmd_buffer, image, aspect, level,
                              base_layer, level_layer_count,
-                             ISL_AUX_OP_FAST_CLEAR, false);
+                             ISL_AUX_OP_AMBIGUATE, false);
+            genX(set_image_needs_resolve)(cmd_buffer, image,
+                                          aspect, level, false);
          }
-      } else if (image->samples > 1) {
+      } else {
          if (image->samples == 4 || image->samples == 16) {
             anv_perf_warn(cmd_buffer->device->instance, image,
                           "Doing a potentially unnecessary fast-clear to "
@@ -713,32 +724,6 @@ transition_color_buffer(struct anv_cmd_buffer *cmd_buffer,
                           base_layer, layer_count,
                           ISL_AUX_OP_FAST_CLEAR, false);
       }
-      /* At this point, some elements of the CCS buffer may have the fast-clear
-       * bit-arrangement. As the user writes to a subresource, we need to have
-       * the associated CCS elements enter the ambiguated state. This enables
-       * reads (implicit or explicit) to reflect the user-written data instead
-       * of the clear color. The only time such elements will not change their
-       * state as described above, is in a final layout that doesn't have CCS
-       * enabled. In this case, we must force the associated CCS buffers of the
-       * specified range to enter the ambiguated state in advance.
-       */
-      if (image->samples == 1 &&
-          image->planes[plane].aux_usage != ISL_AUX_USAGE_CCS_E &&
-          final_layout != VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL) {
-         /* The CCS_D buffer may not be enabled in the final layout. Call this
-          * function again with a initial layout of COLOR_ATTACHMENT_OPTIMAL
-          * to perform a resolve.
-          */
-          anv_perf_warn(cmd_buffer->device->instance, image,
-                        "Performing an additional resolve for CCS_D layout "
-                        "transition. Consider always leaving it on or "
-                        "performing an ambiguation pass.");
-         transition_color_buffer(cmd_buffer, image, aspect,
-                                 base_level, level_count,
-                                 base_layer, layer_count,
-                                 VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL,
-                                 final_layout);
-      }
       return;
    }