+/**
+ * Move load_interpolated_input with simple (payload-based) barycentric modes
+ * to the top of the program so we don't emit multiple PLNs for the same input.
+ *
+ * This works around CSE not being able to handle non-dominating cases
+ * such as:
+ *
+ * if (...) {
+ * interpolate input
+ * } else {
+ * interpolate the same exact input
+ * }
+ *
+ * This should be replaced by global value numbering someday.
+ */
+void
+move_interpolation_to_top(nir_shader *nir)
+{
+ nir_foreach_function(f, nir) {
+ if (!f->impl)
+ continue;
+
+ nir_block *top = nir_start_block(f->impl);
+ exec_node *cursor_node = NULL;
+
+ nir_foreach_block(block, f->impl) {
+ if (block == top)
+ continue;
+
+ nir_foreach_instr_safe(instr, block) {
+ if (instr->type != nir_instr_type_intrinsic)
+ continue;
+
+ nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+ if (intrin->intrinsic != nir_intrinsic_load_interpolated_input)
+ continue;
+ nir_intrinsic_instr *bary_intrinsic =
+ nir_instr_as_intrinsic(intrin->src[0].ssa->parent_instr);
+ nir_intrinsic_op op = bary_intrinsic->intrinsic;
+
+ /* Leave interpolateAtSample/Offset() where they are. */
+ if (op == nir_intrinsic_load_barycentric_at_sample ||
+ op == nir_intrinsic_load_barycentric_at_offset)
+ continue;
+
+ nir_instr *move[3] = {
+ &bary_intrinsic->instr,
+ intrin->src[1].ssa->parent_instr,
+ instr
+ };
+
+ for (unsigned i = 0; i < ARRAY_SIZE(move); i++) {
+ if (move[i]->block != top) {
+ move[i]->block = top;
+ exec_node_remove(&move[i]->node);
+ if (cursor_node) {
+ exec_node_insert_after(cursor_node, &move[i]->node);
+ } else {
+ exec_list_push_head(&top->instr_list, &move[i]->node);
+ }
+ cursor_node = &move[i]->node;
+ }
+ }
+ }
+ }
+ nir_metadata_preserve(f->impl, (nir_metadata)
+ ((unsigned) nir_metadata_block_index |
+ (unsigned) nir_metadata_dominance));
+ }
+}
+
+/**
+ * Apply default interpolation settings to FS inputs which don't specify any.
+ */
+static void
+brw_nir_set_default_interpolation(const struct gen_device_info *devinfo,
+ struct nir_shader *nir,
+ bool api_flat_shade,
+ bool per_sample_interpolation)
+{
+ assert(nir->stage == MESA_SHADER_FRAGMENT);
+
+ nir_foreach_variable(var, &nir->inputs) {
+ /* Apply default interpolation mode.
+ *
+ * Everything defaults to smooth except for the legacy GL color
+ * built-in variables, which might be flat depending on API state.
+ */
+ if (var->data.interpolation == INTERP_MODE_NONE) {
+ const bool flat = api_flat_shade &&
+ (var->data.location == VARYING_SLOT_COL0 ||
+ var->data.location == VARYING_SLOT_COL1);
+
+ var->data.interpolation = flat ? INTERP_MODE_FLAT
+ : INTERP_MODE_SMOOTH;
+ }
+
+ /* Apply 'sample' if necessary for API state. */
+ if (per_sample_interpolation &&
+ var->data.interpolation != INTERP_MODE_FLAT) {
+ var->data.centroid = false;
+ var->data.sample = true;
+ }
+
+ /* On Ironlake and below, there is only one interpolation mode.
+ * Centroid interpolation doesn't mean anything on this hardware --
+ * there is no multisampling.
+ */
+ if (devinfo->gen < 6) {
+ var->data.centroid = false;
+ var->data.sample = false;
+ }
+ }
+}
+
+/**
+ * Demote per-sample barycentric intrinsics to centroid.
+ *
+ * Useful when rendering to a non-multisampled buffer.
+ */
+static void
+demote_sample_qualifiers(nir_shader *nir)
+{
+ nir_foreach_function(f, nir) {
+ if (!f->impl)
+ continue;
+
+ nir_builder b;
+ nir_builder_init(&b, f->impl);
+
+ nir_foreach_block(block, f->impl) {
+ nir_foreach_instr_safe(instr, block) {
+ if (instr->type != nir_instr_type_intrinsic)
+ continue;
+
+ nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+ if (intrin->intrinsic != nir_intrinsic_load_barycentric_sample &&
+ intrin->intrinsic != nir_intrinsic_load_barycentric_at_sample)
+ continue;
+
+ b.cursor = nir_before_instr(instr);
+ nir_ssa_def *centroid =
+ nir_load_barycentric(&b, nir_intrinsic_load_barycentric_centroid,
+ nir_intrinsic_interp_mode(intrin));
+ nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
+ nir_src_for_ssa(centroid));
+ nir_instr_remove(instr);
+ }
+ }
+
+ nir_metadata_preserve(f->impl, (nir_metadata)
+ ((unsigned) nir_metadata_block_index |
+ (unsigned) nir_metadata_dominance));
+ }
+}
+