Mesa (10.0): i965: Always reserve binding table space for at least one render target.

[Ian Romanick]

Module: Mesa
Branch: 10.0
Commit: 44e38a878aef79b53dd10d45afeec7cc89729f80
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=44e38a878aef79b53dd10d45afeec7cc89729f80

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Tue Nov 26 00:30:19 2013 -0800

i965: Always reserve binding table space for at least one render target.

In brw_update_renderbuffer_surfaces(), if there are no color draw
buffers, we always set up a null render target at surface index 0 so we
have something to use with the FB write marking the end of thread.

However, when we recently began computing surface indexes dynamically,
we failed to reserve space for it.  This meant that the first texture
would be assigned surface index 0, and our closing FB write would
clobber the texture.

Fixes Piglit's EXT_packed_depth_stencil/fbo-blit-d24s8 test on Gen4-5,
which regressed as of commit 4e5306453da6a1c076309e543ec92d999e02f67a
("i965/fs: Dynamically set up the WM binding table offsets.")

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70605
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Chris Forbes <chrisf at ijw.co.nz>
Tested-by: lu hua <huax.lu at intel.com>
Cc: "10.0" mesa-stable at lists.freedesktop.org
(cherry picked from commit c4815f6cd6f659acd361f1b4cf63473a46ca7de9)

---

 src/mesa/drivers/dri/i965/brw_fs.cpp |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index f89390c..25731fb 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -3192,8 +3192,11 @@ fs_visitor::assign_binding_table_offsets()
 {
    uint32_t next_binding_table_offset = 0;
 
+   /* If there are no color regions, we still perform an FB write to a null
+    * renderbuffer, which we place at surface index 0.
+    */
    c->prog_data.binding_table.render_target_start = next_binding_table_offset;
-   next_binding_table_offset += c->key.nr_color_regions;
+   next_binding_table_offset += MAX2(c->key.nr_color_regions, 1);
 
    assign_common_binding_table_offsets(next_binding_table_offset);
 }