i965: Add a flag telling color resolve pass to ignore CCS_E

v2 (Ben): Use combination of msaa_layout and number of samples
          instead of introducing explicit type for lossless
          compression (intel_miptree_is_lossless_compressed()).

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Ben Widawsky <benjamin.widawsky@intel.com>

src/mesa/drivers/dri/i965/brw_context.c

@@ -208,7 +208,11 @@ intel_update_state(struct gl_context * ctx, GLuint new_state)
       if (!tex_obj || !tex_obj->mt)
 	 continue;
       intel_miptree_all_slices_resolve_depth(brw, tex_obj->mt);
-      intel_miptree_resolve_color(brw, tex_obj->mt, 0);
+      /* Sampling engine understands lossless compression and resolving
+       * those surfaces should be skipped for performance reasons.
+       */
+      intel_miptree_resolve_color(brw, tex_obj->mt,
+                                  INTEL_MIPTREE_IGNORE_CCS_E);
       brw_render_cache_set_check_flush(brw, tex_obj->mt->bo);
    }
 
@@ -223,6 +227,12 @@ intel_update_state(struct gl_context * ctx, GLuint new_state)
             tex_obj = intel_texture_object(u->TexObj);
 
             if (tex_obj && tex_obj->mt) {
+               /* Access to images is implemented using indirect messages
+                * against data port. Normal render target write understands
+                * lossless compression but unfortunately the typed/untyped
+                * read/write interface doesn't. Therefore the compressed
+                * surfaces need to be resolved prior to accessing them.
+                */
                intel_miptree_resolve_color(brw, tex_obj->mt, 0);
                brw_render_cache_set_check_flush(brw, tex_obj->mt->bo);
             }

src/mesa/drivers/dri/i965/intel_mipmap_tree.c

@@ -2041,7 +2041,13 @@ intel_miptree_resolve_color(struct brw_context *brw,
                             struct intel_mipmap_tree *mt,
                             int flags)
 {
-   (void)flags;
+   /* From gen9 onwards there is new compression scheme for single sampled
+    * surfaces called "lossless compressed". These don't need to be always
+    * resolved.
+    */
+   if ((flags & INTEL_MIPTREE_IGNORE_CCS_E) &&
+       intel_miptree_is_lossless_compressed(brw, mt))
+      return;
 
    switch (mt->fast_clear_state) {
    case INTEL_FAST_CLEAR_STATE_NO_MCS:

src/mesa/drivers/dri/i965/intel_mipmap_tree.h

@@ -888,6 +888,15 @@ intel_miptree_used_for_rendering(struct intel_mipmap_tree *mt)
       mt->fast_clear_state = INTEL_FAST_CLEAR_STATE_UNRESOLVED;
 }
 
+/**
+ * Flag values telling color resolve pass which special types of buffers
+ * can be ignored.
+ *
+ * INTEL_MIPTREE_IGNORE_CCS_E:   Lossless compressed (single-sample
+ *                               compression scheme since gen9)
+ */
+#define INTEL_MIPTREE_IGNORE_CCS_E (1 << 0)
+
 void
 intel_miptree_resolve_color(struct brw_context *brw,
                             struct intel_mipmap_tree *mt,