Mesa (master): i965/fs: Set LastRT on the final FB write on Broadwell.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: d4d886a0bc86eb2045b0327fe147eef3c400ffba
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d4d886a0bc86eb2045b0327fe147eef3c400ffba

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Mon Jul 21 16:17:46 2014 -0700

i965/fs: Set LastRT on the final FB write on Broadwell.

In Piglit's EXT_framebuffer_multisample/alpha-to-coverage-dual-src-blend
test, key->nr_color_regions == 2, but the dual source blend FB write has
ir->target set to 0.  So we failed to set "Last Render Target Select" on
any FB write message.

We only emit one FB write per render target, so my comment about setting
LastRT on every FB write directed at the last color region is a bit...
misinformed.  According to the documentation, depth buffer writes and
scoreboard updates happen on the FB write with LastRT set, so I believe
we want to set it only once.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Matt Turner <mattst88 at gmail.com>
Cc: "10.2" <mesa-stable at lists.freedesktop.org>

---

 src/mesa/drivers/dri/i965/gen8_fs_generator.cpp |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/gen8_fs_generator.cpp b/src/mesa/drivers/dri/i965/gen8_fs_generator.cpp
index 2d745fd..4f0cf70 100644
--- a/src/mesa/drivers/dri/i965/gen8_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/gen8_fs_generator.cpp
@@ -116,10 +116,8 @@ gen8_fs_generator::generate_fb_write(fs_inst *ir)
 
    uint32_t msg_control = msg_type;
 
-   /* "Last Render Target Select" must be set on all writes to the last of
-    * the render targets (if using MRT), or always for a single RT scenario.
-    */
-   if ((ir->target == key->nr_color_regions - 1) || !key->nr_color_regions)
+   /* Set "Last Render Target Select" on the final FB write. */
+   if (ir->eot)
       msg_control |= (1 << 4); /* Last Render Target Select */
 
    uint32_t surf_index =