[Mesa-dev] [PATCH] i965/vec4: select predicate based on writemask for sel emissions

[Alejandro Piñeiro]

Equivalent to commit 4eebeb but with sel operations. In this case
we select the PredCtrl based on the writemask.

This change allows cmod propagation to optimize out several
instructions.

Shader-db numbers:
total instructions in shared programs: 6235835 -> 6228008 (-0.13%)
instructions in affected programs:     219850 -> 212023 (-3.56%)
total loops in shared programs:        1979 -> 1979 (0.00%)
helped:                                1192
HURT:                                  0
---
 src/mesa/drivers/dri/i965/brw_vec4_nir.cpp | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
index 0f04f65..bc86be6 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
@@ -1437,8 +1437,24 @@ vec4_visitor::nir_emit_alu(nir_alu_instr *instr)
    case nir_op_bcsel:
       emit(CMP(dst_null_d(), op[0], src_reg(0), BRW_CONDITIONAL_NZ));
       inst = emit(BRW_OPCODE_SEL, dst, op[1], op[2]);
-      inst->predicate = BRW_PREDICATE_NORMAL;
+      switch (dst.writemask) {
+      case WRITEMASK_X:
+         inst->predicate = BRW_PREDICATE_ALIGN16_REPLICATE_X;
+         break;
+      case WRITEMASK_Y:
+         inst->predicate = BRW_PREDICATE_ALIGN16_REPLICATE_Y;
+         break;
+      case WRITEMASK_Z:
+         inst->predicate = BRW_PREDICATE_ALIGN16_REPLICATE_Z;
+         break;
+      case WRITEMASK_W:
+         inst->predicate = BRW_PREDICATE_ALIGN16_REPLICATE_W;
+         break;
+      default:
+         inst->predicate = BRW_PREDICATE_NORMAL;
       break;
+      }
+   break;
 
    case nir_op_fdot_replicated2:
       inst = emit(BRW_OPCODE_DP2, dst, op[0], op[1]);
-- 
2.1.4