i965: allocate at least 1 BLEND_STATE element

When there are no color buffer render targets, gen6 and gen7 still
use the first BLEND_STATE element to determine alpha test.
gen6_upload_blend_state was allocating zero elements when
ctx->Color.AlphaEnabled was false.
That left _3DSTATE_CC_STATE_POINTERS or _3DSTATE_BLEND_STATE_POINTERS
pointing to random data from some previous brw_state_batch().
That sometimes suppressed depth rendering when those bits
happened to mean COMPAREFUNC_NEVER.
This produced flickering shadows for dota2 reborn.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80500
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

diff --git a/src/mesa/drivers/dri/i965/gen6_cc.c b/src/mesa/drivers/dri/i965/gen6_cc.c
index 2bfa271b5271f1623a1767abea02300d613e6605..2b76e241d1ae7be3adbe1ecb42136acf60310b68 100644 (file)
--- a/src/mesa/drivers/dri/i965/gen6_cc.c
+++ b/src/mesa/drivers/dri/i965/gen6_cc.c
@@ -51,7 +51,7 @@ gen6_upload_blend_state(struct brw_context *brw)
     * with render target 0, which will reference BLEND_STATE[0] for
     * alpha test enable.
     */
-   if (nr_draw_buffers == 0 && ctx->Color.AlphaEnabled)
+   if (nr_draw_buffers == 0)
       nr_draw_buffers = 1;
 
    size = sizeof(*blend) * nr_draw_buffers;