Mesa (master): i965: For color clears, only disable writes to components that exist.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: eccad18bd89556608092278cf46a9aaa4605f163
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=eccad18bd89556608092278cf46a9aaa4605f163

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Fri Mar 21 03:47:16 2014 -0700

i965: For color clears, only disable writes to components that exist.

The SIMD16 replicated FB write message only works if we don't need the
color calculator to mask our framebuffer writes.  Previously, we bailed
on it if color_mask wasn't <true, true, true, true>.  However, this was
needlessly strict for formats with fewer than four components - only the
components that actually exist matter.

WebGL Aquarium attempts to clear a BGRX texture with the ColorMask set
to <true, true, true, false>.  This will work perfectly fine with the
replicated data message; we just bailed unnecessarily.

Improves performance of WebGL Aquarium on Iris Pro (at 1920x1080) by
abound 50%, and Bay Trail (at 1366x768) by over 70% (using Chrome 24).

v2: Use _mesa_format_has_color_component() to properly handle ALPHA
    formats (and generally be less fragile).

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Eric Anholt <eric at anholt.net>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
Tested-by: Dylan Baker <baker.dylan.c at gmail.com>

---

 src/mesa/drivers/dri/i965/brw_blorp_clear.cpp |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
index 3c6c57b..fd18b45 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
@@ -231,7 +231,8 @@ brw_blorp_clear_params::brw_blorp_clear_params(struct brw_context *brw,
     * state.  This is not documented.
     */
    for (int i = 0; i < 4; i++) {
-      if (!color_mask[i]) {
+      if (_mesa_format_has_color_component(irb->mt->format, i) &&
+          !color_mask[i]) {
          color_write_disable[i] = true;
          wm_prog_key.use_simd16_replicated_data = false;
       }