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 <[email protected]>
Reviewed-by: Chris Forbes <[email protected]>
Tested-by: lu hua <[email protected]>
Cc: "10.0" [email protected]

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 d1b77129d0f..eecde6271d9 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -3181,8 +3181,11 @@ 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);
 }