[Mesa-dev] [PATCH 4/5] i965/ir: Pass identity mask to brw_find_live_channel() in the packed dispatch case.

[Francisco Jerez]

This avoids emitting a few extra instructions required to take the
dispatch mask into account when it's known to be tightly packed.
---
 src/mesa/drivers/dri/i965/brw_fs_generator.cpp   | 4 +++-
 src/mesa/drivers/dri/i965/brw_vec4_generator.cpp | 8 ++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
index c510f42..bdeda3b 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
@@ -2045,7 +2045,9 @@ fs_generator::generate_code(const cfg_t *cfg, int dispatch_width)
 
       case SHADER_OPCODE_FIND_LIVE_CHANNEL: {
          const struct brw_reg mask =
-            stage == MESA_SHADER_FRAGMENT ? brw_vmask_reg() : brw_dmask_reg();
+            brw_stage_has_packed_dispatch(stage, prog_data) ? brw_imm_ud(~0u) :
+            stage == MESA_SHADER_FRAGMENT ? brw_vmask_reg() :
+            brw_dmask_reg();
          brw_find_live_channel(p, dst, mask);
          break;
       }
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
index f9e6d1c..2bef549 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
@@ -1862,9 +1862,13 @@ generate_code(struct brw_codegen *p,
          brw_memory_fence(p, dst);
          break;
 
-      case SHADER_OPCODE_FIND_LIVE_CHANNEL:
-         brw_find_live_channel(p, dst, brw_dmask_reg());
+      case SHADER_OPCODE_FIND_LIVE_CHANNEL: {
+         const struct brw_reg mask =
+            brw_stage_has_packed_dispatch(nir->stage, &prog_data->base) ?
+            brw_imm_ud(~0u) : brw_dmask_reg();
+         brw_find_live_channel(p, dst, mask);
          break;
+      }
 
       case SHADER_OPCODE_BROADCAST:
          assert(inst->force_writemask_all);
-- 
2.9.0