i965/nir: Make use of nir_opt_undef

Shader-db result on Ivy Bridge:
total instructions in shared programs: 145484 -> 145445 (-0.03%)
instructions in affected programs:     225 -> 186 (-17.33%)
helped:                                5
HURT:                                  0

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Thomas Helland <thomashelland90@gmail.com>
Signed-off-by: Boyan Ding <boyan.j.ding@gmail.com>

diff --git a/src/mesa/drivers/dri/i965/brw_nir.c b/src/mesa/drivers/dri/i965/brw_nir.c
index 8c6d28a..247b223 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_nir.c
+++ b/src/mesa/drivers/dri/i965/brw_nir.c
@@ -63,6 +63,8 @@ nir_optimize(nir_shader *nir, bool is_scalar)
       nir_validate_shader(nir);
       progress |= nir_opt_remove_phis(nir);
       nir_validate_shader(nir);
+      progress |= nir_opt_undef(nir);
+      nir_validate_shader(nir);
    } while (progress);
 }