[Mesa-dev] [PATCH] i965: Don't make instructions with a null dest a barrier to scheduling.

[Matt Turner]

Now that we properly track accumulator dependencies, the scheduler is
able to schedule instructions between the mach and mov in the common
the integer multiplication pattern:

   mul  acc0, x, y
   mach null, x, y
   mov  dest, acc0

Since a null destination implies no dependency on the destination, we
can also safely schedule instructions (that don't write the accumulator)
between the mul and mach.
---
This depends on JP's accumulator series.

 src/mesa/drivers/dri/i965/brw_schedule_instructions.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_schedule_instructions.cpp 
b/src/mesa/drivers/dri/i965/brw_schedule_instructions.cpp
index 3538da5..910b73a 100644
--- a/src/mesa/drivers/dri/i965/brw_schedule_instructions.cpp
+++ b/src/mesa/drivers/dri/i965/brw_schedule_instructions.cpp
@@ -864,7 +864,8 @@ fs_instruction_scheduler::calculate_deps()
       } else if (inst->dst.is_accumulator()) {
          add_dep(last_accumulator_write, n);
          last_accumulator_write = n;
-      } else if (inst->dst.file != BAD_FILE) {
+      } else if (inst->dst.file != BAD_FILE &&
+                 !inst->dst.is_null()) {
         add_barrier_deps(n);
       }
 
@@ -983,7 +984,8 @@ fs_instruction_scheduler::calculate_deps()
          }
       } else if (inst->dst.is_accumulator()) {
          last_accumulator_write = n;
-      } else if (inst->dst.file != BAD_FILE) {
+      } else if (inst->dst.file != BAD_FILE &&
+                 !inst->dst.is_null()) {
         add_barrier_deps(n);
       }
 
@@ -1089,7 +1091,8 @@ vec4_instruction_scheduler::calculate_deps()
       } else if (inst->dst.is_accumulator()) {
          add_dep(last_accumulator_write, n);
          last_accumulator_write = n;
-      } else if (inst->dst.file != BAD_FILE) {
+      } else if (inst->dst.file != BAD_FILE &&
+                 !inst->dst.is_null()) {
          add_barrier_deps(n);
       }
 
@@ -1173,7 +1176,8 @@ vec4_instruction_scheduler::calculate_deps()
          last_fixed_grf_write = n;
       } else if (inst->dst.is_accumulator()) {
          last_accumulator_write = n;
-      } else if (inst->dst.file != BAD_FILE) {
+      } else if (inst->dst.file != BAD_FILE &&
+                 !inst->dst.is_null()) {
          add_barrier_deps(n);
       }
 
-- 
1.8.3.2

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