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@intel.com>
Cc: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9667>

diff --git a/src/intel/compiler/brw_schedule_instructions.cpp b/src/intel/compiler/brw_schedule_instructions.cpp
index e516af5..d848f0b 100644 (file)
--- 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);