Mesa (master): i965: Fix predicated-send-based discards with MRT.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 171ec9585f214c2dff3cfc97acebf5286bb5001d
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=171ec9585f214c2dff3cfc97acebf5286bb5001d

Author: Eric Anholt <eric at anholt.net>
Date:   Tue Mar  4 15:12:40 2014 -0800

i965: Fix predicated-send-based discards with MRT.

We need the header setup to not be predicated on which pixels are
undiscarded.  I'm not sure originally if I had thought that the mask
disable implied predicate disable, or if I had just misread the mask
disable as predicate disable.  Either way, I know I had spent more time
thinking about this in the gen8 generator than the gen7 generator.

Plus, it turns out that I had mis-implemented the "the GPU will use the
predicate unless this header is present" comment, by skipping setting up
the pixel mask when the header was present.

Fixes GPU hangs in piglit glsl-fs-discard-mrt, Trine, Trine 2 and
preusmably MLL.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75207
Tested-by: Tapani Pälli <tapani.palli at intel.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

---

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

diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index 748a2e2..e590bdf 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -103,14 +103,14 @@ fs_generator::generate_fb_write(fs_inst *inst)
     */
    brw_push_insn_state(p);
    brw_set_mask_control(p, BRW_MASK_DISABLE);
+   brw_set_predicate_control(p, BRW_PREDICATE_NONE);
    brw_set_compression_control(p, BRW_COMPRESSION_NONE);
 
    if (inst->header_present) {
       /* On HSW, the GPU will use the predicate on SENDC, unless the header is
        * present.
        */
-      if (!brw->is_haswell && ((fp && fp->UsesKill) ||
-                               c->key.alpha_test_func)) {
+      if ((fp && fp->UsesKill) || c->key.alpha_test_func) {
          struct brw_reg pixel_mask;
 
          if (brw->gen >= 6)