Re-enable regular fast-clears (CCS_D) on gen9+

This reverts commit ee57b15ec764736e2d5360beaef9fb2045ed0f68, "i965:
Disable regular fast-clears (CCS_D) on gen9+".  How taht we've fixed the
issue with too many different aux usages in the render cache, it should
be safe to re-enable CCS_D for sRGB.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104163
Tested-by: Eero Tamminen <eero.t.tamminen@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "17.3" <mesa-stable@lists.freedesktop.org>

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

@@ -293,17 +293,7 @@ brw_is_color_fast_clear_compatible(struct brw_context *brw,
        brw->mesa_to_isl_render_format[mt->format])
       return false;
 
-   /* Gen9 doesn't support fast clear on single-sampled SRGB buffers. When
-    * GL_FRAMEBUFFER_SRGB is enabled any color renderbuffers will be
-    * resolved in intel_update_state. In that case it's pointless to do a
-    * fast clear because it's very likely to be immediately resolved.
-    */
    const bool srgb_rb = _mesa_get_srgb_format_linear(mt->format) != mt->format;
-   if (devinfo->gen >= 9 &&
-       mt->surf.samples == 1 &&
-       ctx->Color.sRGBEnabled && srgb_rb)
-      return false;
-
   /* Gen10 doesn't automatically decode the clear color of sRGB buffers. Since
    * we currently don't perform this decode in software, avoid a fast-clear
    * altogether. TODO: Do this in software.

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

@@ -211,13 +211,7 @@ intel_miptree_supports_ccs(struct brw_context *brw,
    if (!brw->mesa_format_supports_render[mt->format])
       return false;
 
-   if (devinfo->gen >= 9) {
-      mesa_format linear_format = _mesa_get_srgb_format_linear(mt->format);
-      const enum isl_format isl_format =
-         brw_isl_format_for_mesa_format(linear_format);
-      return isl_format_supports_ccs_e(&brw->screen->devinfo, isl_format);
-   } else
-      return true;
+   return true;
 }
 
 static bool
@@ -260,7 +254,7 @@ intel_miptree_supports_hiz(const struct brw_context *brw,
  * our HW tends to support more linear formats than sRGB ones, we use this
  * format variant for check for CCS_E compatibility.
  */
-MAYBE_UNUSED static bool
+static bool
 format_ccs_e_compat_with_miptree(const struct gen_device_info *devinfo,
                                  const struct intel_mipmap_tree *mt,
                                  enum isl_format access_format)
@@ -294,12 +288,13 @@ intel_miptree_supports_ccs_e(struct brw_context *brw,
    if (!intel_miptree_supports_ccs(brw, mt))
       return false;
 
-   /* Fast clear can be also used to clear srgb surfaces by using equivalent
-    * linear format. This trick, however, can't be extended to be used with
-    * lossless compression and therefore a check is needed to see if the format
-    * really is linear.
+   /* Many window system buffers are sRGB even if they are never rendered as
+    * sRGB.  For those, we want CCS_E for when sRGBEncode is false.  When the
+    * surface is used as sRGB, we fall back to CCS_D.
     */
-   return _mesa_get_srgb_format_linear(mt->format) == mt->format;
+   mesa_format linear_format = _mesa_get_srgb_format_linear(mt->format);
+   enum isl_format isl_format = brw_isl_format_for_mesa_format(linear_format);
+   return isl_format_supports_ccs_e(&brw->screen->devinfo, isl_format);
 }
 
 /**
@@ -2690,29 +2685,27 @@ intel_miptree_render_aux_usage(struct brw_context *brw,
       return ISL_AUX_USAGE_MCS;
 
    case ISL_AUX_USAGE_CCS_D:
-      /* If FRAMEBUFFER_SRGB is used on Gen9+ then we need to resolve any of
-       * the single-sampled color renderbuffers because the CCS buffer isn't
-       * supported for SRGB formats. This only matters if FRAMEBUFFER_SRGB is
-       * enabled because otherwise the surface state will be programmed with
-       * the linear equivalent format anyway.
-       */
-      if (isl_format_is_srgb(render_format) &&
-          _mesa_get_srgb_format_linear(mt->format) != mt->format) {
-         return ISL_AUX_USAGE_NONE;
-      } else if (!mt->mcs_buf) {
-         return ISL_AUX_USAGE_NONE;
-      } else {
-         return ISL_AUX_USAGE_CCS_D;
-      }
+      return mt->mcs_buf ? ISL_AUX_USAGE_CCS_D : ISL_AUX_USAGE_NONE;
 
    case ISL_AUX_USAGE_CCS_E: {
-      /* Lossless compression is not supported for SRGB formats, it
-       * should be impossible to get here with such surfaces.
+      /* If the format supports CCS_E and is compatible with the miptree,
+       * then we can use it.
        */
-      assert(!isl_format_is_srgb(render_format) ||
-             _mesa_get_srgb_format_linear(mt->format) == mt->format);
+      if (format_ccs_e_compat_with_miptree(&brw->screen->devinfo,
+                                           mt, render_format))
+         return ISL_AUX_USAGE_CCS_E;
+
+      /* Otherwise, we have to fall back to CCS_D */
+
+      /* gen9 hardware technically supports non-0/1 clear colors with sRGB
+       * formats.  However, there are issues with blending where it doesn't
+       * properly apply the sRGB curve to the clear color when blending.
+       */
+      if (blend_enabled && isl_format_is_srgb(render_format) &&
+          !isl_color_value_is_zero_one(mt->fast_clear_color, render_format))
+         return ISL_AUX_USAGE_NONE;
 
-      return ISL_AUX_USAGE_CCS_E;
+      return ISL_AUX_USAGE_CCS_D;
    }
 
    default: