i965: Rework the unlit centroid workaround.

Previously, for every input, we moved the dispatch mask to the flag
register, then emitted two predicated PLN instructions, one with
centroid barycentric coordinates (for normal pixels), and one with
pixel barycentric coordinates (for unlit helper pixels).

Instead, we can simply emit a set of predicated MOVs at the top of
the program which copy the pixel barycentric coordinates over the
centroid ones for unlit helper pixel channels.  Then, we can just
use normal PLNs.

On Sandybridge:

total instructions in shared programs: 7538470 -> 7534500 (-0.05%)
instructions in affected programs: 101268 -> 97298 (-3.92%)
helped: 705
HURT: 9 (all of which are SIMD16 programs)

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>
Reviewed-by: Matt Turner <[email protected]>

2 files changed, 33 insertions, 25 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index c1f413b366a..e1655a4c141 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -3422,31 +3422,7 @@ fs_visitor::nir_emit_fs_intrinsic(const fs_builder &bld,
          interp.type = BRW_REGISTER_TYPE_F;
          dest.type = BRW_REGISTER_TYPE_F;
 
-         if (devinfo->needs_unlit_centroid_workaround &&
-             bary_intrin == nir_intrinsic_load_barycentric_centroid) {
-
-            /* Get the pixel/sample mask into f0 so that we know which
-             * pixels are lit.  Then, for each channel that is unlit,
-             * replace the centroid data with non-centroid data.
-             */
-            bld.emit(FS_OPCODE_MOV_DISPATCH_TO_FLAGS);
-
-            fs_reg dest_i = offset(dest, bld, i);
-            fs_reg dst_xy_pixel =
-               delta_xy[brw_barycentric_mode(interp_mode,
-                  nir_intrinsic_load_barycentric_pixel)];
-
-            fs_inst *inst;
-            inst = bld.emit(FS_OPCODE_LINTERP, dest_i, dst_xy_pixel, interp);
-            inst->predicate = BRW_PREDICATE_NORMAL;
-            inst->predicate_inverse = true;
-            inst->no_dd_clear = true;
-
-            inst = bld.emit(FS_OPCODE_LINTERP, dest_i, dst_xy, interp);
-            inst->predicate = BRW_PREDICATE_NORMAL;
-            inst->predicate_inverse = false;
-            inst->no_dd_check = true;
-         } else if (devinfo->gen < 6 && interp_mode == INTERP_MODE_SMOOTH) {
+         if (devinfo->gen < 6 && interp_mode == INTERP_MODE_SMOOTH) {
             fs_reg tmp = vgrf(glsl_type::float_type);
             bld.emit(FS_OPCODE_LINTERP, tmp, dst_xy, interp);
             bld.MUL(offset(dest, bld, i), tmp, this->pixel_w);
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 6d843749f44..4e0db06ca62 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -308,9 +308,41 @@ fs_visitor::emit_interpolation_setup_gen6()
    this->wpos_w = vgrf(glsl_type::float_type);
    abld.emit(SHADER_OPCODE_RCP, this->wpos_w, this->pixel_w);
 
+   brw_wm_prog_data *wm_prog_data = (brw_wm_prog_data *) prog_data;
+   uint32_t centroid_modes = wm_prog_data->barycentric_interp_modes &
+      (1 << BRW_BARYCENTRIC_PERSPECTIVE_CENTROID |
+       1 << BRW_BARYCENTRIC_NONPERSPECTIVE_CENTROID);
+
    for (int i = 0; i < BRW_BARYCENTRIC_MODE_COUNT; ++i) {
       uint8_t reg = payload.barycentric_coord_reg[i];
       this->delta_xy[i] = fs_reg(brw_vec16_grf(reg, 0));
+
+      if (devinfo->needs_unlit_centroid_workaround &&
+          (centroid_modes & (1 << i))) {
+         /* Get the pixel/sample mask into f0 so that we know which
+          * pixels are lit.  Then, for each channel that is unlit,
+          * replace the centroid data with non-centroid data.
+          */
+         bld.emit(FS_OPCODE_MOV_DISPATCH_TO_FLAGS);
+
+         uint8_t pixel_reg = payload.barycentric_coord_reg[i - 1];
+
+         set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                           bld.half(0).MOV(brw_vec8_grf(reg, 0),
+                                           brw_vec8_grf(pixel_reg, 0)));
+         set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                           bld.half(0).MOV(brw_vec8_grf(reg + 1, 0),
+                                           brw_vec8_grf(pixel_reg + 1, 0)));
+         if (dispatch_width == 16) {
+            set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                              bld.half(1).MOV(brw_vec8_grf(reg + 2, 0),
+                                              brw_vec8_grf(pixel_reg + 2, 0)));
+            set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                              bld.half(1).MOV(brw_vec8_grf(reg + 3, 0),
+                                              brw_vec8_grf(pixel_reg + 3, 0)));
+         }
+         assert(dispatch_width != 32); /* not implemented yet */
+      }
    }
 }