[Mesa-dev] [PATCH 5/7] i965/blorp: allow multisample blorp clears

[Paul Berry]

Previously, we didn't do multisample blorp clears because we couldn't
figure out how to get them to work.  The reason for this was because
we weren't setting the brw_blorp_params num_samples field consistently
with dst.num_samples.  Now that those two fields have been collapsed
down into one, we can do multisample blorp clears.

However, we need to do a few other pieces of bookkeeping to make them
work correctly in all circumstances:

- Since blorp clears may now operate on multisampled window system
  framebuffers, they need to call
  intel_renderbuffer_set_needs_downsample() to ensure that a
  downsample happens before buffer swap (or glReadPixels()).

- When clearing a layered multisample buffer attachment using UMS or
  CMS layout, we need to advance layer by multiples of num_samples
  (since each logical layer is associated with num_samples physical
  layers).

Note: we still don't do multisample fast color clears; more work needs
to be done to enable those.
---
 src/mesa/drivers/dri/i965/brw_blorp_clear.cpp | 31 +++++++++++----------------
 1 file changed, 13 insertions(+), 18 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
index ce6fcb2..308f49c 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
@@ -239,7 +239,8 @@ brw_blorp_clear_params::brw_blorp_clear_params(struct brw_context *brw,
    }
 
    /* If we can do this as a fast color clear, do so. */
-   if (irb->mt->fast_clear_state != INTEL_FAST_CLEAR_STATE_NO_MCS &&
+   if (irb->mt->msaa_layout == INTEL_MSAA_LAYOUT_NONE &&
+       irb->mt->fast_clear_state != INTEL_FAST_CLEAR_STATE_NO_MCS &&
        !partial_clear && wm_prog_key.use_simd16_replicated_data &&
        is_color_fast_clear_compatible(brw, format, &ctx->Color.ClearColor)) {
       memset(push_consts, 0xff, 4*sizeof(float));
@@ -503,21 +504,6 @@ bool
 brw_blorp_clear_color(struct brw_context *brw, struct gl_framebuffer *fb,
                       bool partial_clear)
 {
-   /* The constant color clear code doesn't work for multisampled surfaces, so
-    * we need to support falling back to other clear mechanisms.
-    * Unfortunately, our clear code is based on a bitmask that doesn't
-    * distinguish individual color attachments, so we walk the attachments to
-    * see if any require fallback, and fall back for all if any of them need
-    * to.
-    */
-   for (unsigned buf = 0; buf < fb->_NumColorDrawBuffers; buf++) {
-      struct gl_renderbuffer *rb = fb->_ColorDrawBuffers[buf];
-      struct intel_renderbuffer *irb = intel_renderbuffer(rb);
-
-      if (irb && irb->mt->msaa_layout != INTEL_MSAA_LAYOUT_NONE)
-         return false;
-   }
-
    for (unsigned buf = 0; buf < fb->_NumColorDrawBuffers; buf++) {
       struct gl_renderbuffer *rb = fb->_ColorDrawBuffers[buf];
       struct intel_renderbuffer *irb = intel_renderbuffer(rb);
@@ -530,16 +516,25 @@ brw_blorp_clear_color(struct brw_context *brw, struct gl_framebuffer *fb,
          continue;
 
       if (fb->NumLayers > 0) {
-         assert(fb->NumLayers == irb->mt->level[irb->mt_level].depth);
+         unsigned layer_multiplier =
+            (irb->mt->msaa_layout == INTEL_MSAA_LAYOUT_UMS ||
+             irb->mt->msaa_layout == INTEL_MSAA_LAYOUT_CMS) ?
+            irb->mt->num_samples : 1;
+         assert(fb->NumLayers * layer_multiplier ==
+                irb->mt->level[irb->mt_level].depth);
          for (unsigned layer = 0; layer < fb->NumLayers; layer++) {
-            if (!do_single_blorp_clear(brw, fb, rb, buf, partial_clear, layer))
+            if (!do_single_blorp_clear(brw, fb, rb, buf, partial_clear,
+                                       layer * layer_multiplier)) {
                return false;
+            }
          }
       } else {
          unsigned layer = irb->mt_layer;
          if (!do_single_blorp_clear(brw, fb, rb, buf, partial_clear, layer))
             return false;
       }
+
+      intel_renderbuffer_set_needs_downsample(irb);
    }
 
    return true;
-- 
1.8.4.2