Mesa (staging/21.0): intel/fs/vec4: add missing dependency in write-on-write fixed GRFs

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Module: Mesa
Branch: staging/21.0
Commit: b442f8cb7bc8b0be347eace65fc6c8e15b0f7d7e
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b442f8cb7bc8b0be347eace65fc6c8e15b0f7d7e

Author: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Date:   Wed Mar 17 21:30:52 2021 +0200

intel/fs/vec4: add missing dependency in write-on-write fixed GRFs

If we load constant data using pull constant SENDS, and we later load
that register with some other data, we can end up in a situation where
we don't track the initial fixed register write and therefore end up
using uninitialized registers.

This tracks write-on-write of fixed GRFs like we do for normal virtual
GRFs.

v2: Fix post_alloc_reg case (Jason)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Cc: <mesa-stable at lists.freedesktop.org>
Reviewed-by: Francisco Jerez <currojerez at riseup.net>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9667>
(cherry picked from commit 8b6d22109f452b05ab1ce2028f7e18e50edcf325)

---

 .pick_status.json                                | 2 +-
 src/intel/compiler/brw_schedule_instructions.cpp | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index a0706f3dbc2..3f78c79a9e3 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -373,7 +373,7 @@
         "description": "intel/fs/vec4: add missing dependency in write-on-write fixed GRFs",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": null
     },
diff --git a/src/intel/compiler/brw_schedule_instructions.cpp b/src/intel/compiler/brw_schedule_instructions.cpp
index 6207059dc82..dcef08ac041 100644
--- a/src/intel/compiler/brw_schedule_instructions.cpp
+++ b/src/intel/compiler/brw_schedule_instructions.cpp
@@ -1198,9 +1198,12 @@ fs_instruction_scheduler::calculate_deps()
          }
       } else if (inst->dst.file == FIXED_GRF) {
          if (post_reg_alloc) {
-            for (unsigned r = 0; r < regs_written(inst); r++)
+            for (unsigned r = 0; r < regs_written(inst); r++) {
+               add_dep(last_grf_write[inst->dst.nr + r], n);
                last_grf_write[inst->dst.nr + r] = n;
+            }
          } else {
+            add_dep(last_fixed_grf_write, n);
             last_fixed_grf_write = n;
          }
       } else if (inst->dst.is_accumulator()) {
@@ -1428,6 +1431,7 @@ vec4_instruction_scheduler::calculate_deps()
          add_dep(last_mrf_write[inst->dst.nr], n);
          last_mrf_write[inst->dst.nr] = n;
      } else if (inst->dst.file == FIXED_GRF) {
+         add_dep(last_fixed_grf_write, n);
          last_fixed_grf_write = n;
       } else if (inst->dst.is_accumulator()) {
          add_dep(last_accumulator_write, n);