[Mesa-dev] [PATCH] i965/vec4: dead_code_eliminate: update writemask on null_regs based on flag_live

[Alejandro Piñeiro]

---

This patch implements the idea proposed by Francisco Jerez. With this
change, even adding the new condition pointed by Matt Turner on the
"2/5 i965/vec4: adding vec4_cmod_propagation optimization", the shader-db
numbers remain the same. So this patch would go before the optimization
(so in this series it would be the patch 1.5).

Note: Im not resending the patch 2/5, as Matt pointed that he granted
the reviewed status with his suggested change. I can send it if needed
in any case.

 .../drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp    | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
index 8fc7a36..31ea128 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp
@@ -78,13 +78,19 @@ vec4_visitor::dead_code_eliminate()
              sizeof(BITSET_WORD));
 
       foreach_inst_in_block_reverse(vec4_instruction, inst, block) {
-         if (inst->dst.file == GRF && !inst->has_side_effects()) {
+         if ((inst->dst.file == GRF && !inst->has_side_effects()) ||
+             (inst->dst.is_null() && inst->writes_flag())){
             bool result_live[4] = { false };
 
-            for (unsigned i = 0; i < inst->regs_written; i++) {
-               for (int c = 0; c < 4; c++)
-                  result_live[c] |= BITSET_TEST(
-                     live, var_from_reg(alloc, offset(inst->dst, i), c));
+            if (inst->dst.file == GRF) {
+               for (unsigned i = 0; i < inst->regs_written; i++) {
+                  for (int c = 0; c < 4; c++)
+                     result_live[c] |= BITSET_TEST(
+                        live, var_from_reg(alloc, offset(inst->dst, i), c));
+               }
+            } else {
+               for (unsigned c = 0; c < 4; c++)
+                  result_live[c] |= BITSET_TEST(flag_live, c);
             }
 
             /* If the instruction can't do writemasking, then it's all or
-- 
2.1.4