Mesa (master): i965/cnl: Avoid fast-clearing sRGB render buffers

[Nanley Chery]

Module: Mesa
Branch: master
Commit: 0a257b3fe4d184811c1ddab7afeda81459f36720
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=0a257b3fe4d184811c1ddab7afeda81459f36720

Author: Nanley Chery <nanley.g.chery at intel.com>
Date:   Fri Dec  1 14:18:21 2017 -0800

i965/cnl: Avoid fast-clearing sRGB render buffers

Gen10 doesn't automatically decode the clear color of sRGB buffers. To
get correct rendering, avoid fast-clearing such buffers for now.

The driver now passes the following piglit tests:
* spec at arb_framebuffer_srgb@msaa-fast-clear
* spec at ext_texture_srgb@multisample-fast-clear gl_ext_texture_srgb

Suggested-by: Kenneth Graunke <kenneth at whitecape.org>
Suggested-by: Jason Ekstrand <jason at jlekstrand.net>
Signed-off-by: Nanley Chery <nanley.g.chery at intel.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/mesa/drivers/dri/i965/brw_meta_util.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_meta_util.c b/src/mesa/drivers/dri/i965/brw_meta_util.c
index ba92168934..54dc6a5ff9 100644
--- a/src/mesa/drivers/dri/i965/brw_meta_util.c
+++ b/src/mesa/drivers/dri/i965/brw_meta_util.c
@@ -298,13 +298,23 @@ brw_is_color_fast_clear_compatible(struct brw_context *brw,
     * 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 &&
-       _mesa_get_srgb_format_linear(mt->format) != mt->format)
+       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.
+   */
    const mesa_format format = _mesa_get_render_format(ctx, mt->format);
+   if (devinfo->gen >= 10 && srgb_rb) {
+      perf_debug("sRGB fast clear not enabled for (%s)",
+                 _mesa_get_format_name(format));
+      return false;
+   }
+
    if (_mesa_is_format_integer_color(format)) {
       if (devinfo->gen >= 8) {
          perf_debug("Integer fast clear not enabled for (%s)",