--- /dev/null
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "anv_nir.h"
+#include "nir/nir_builder.h"
+
+/**
+ * This file implements the lowering required for VK_KHR_multiview. We
+ * implement multiview using instanced rendering. The number of instances in
+ * each draw call is multiplied by the number of views in the subpass. Then,
+ * in the shader, we divide gl_InstanceId by the number of views and use
+ * gl_InstanceId % view_count to compute the actual ViewIndex.
+ */
+
+struct lower_multiview_state {
+ nir_builder builder;
+
+ uint32_t view_mask;
+
+ nir_ssa_def *instance_id;
+ nir_ssa_def *view_index;
+};
+
+static nir_ssa_def *
+build_instance_id(struct lower_multiview_state *state)
+{
+ assert(state->builder.shader->stage == MESA_SHADER_VERTEX);
+
+ if (state->instance_id == NULL) {
+ nir_builder *b = &state->builder;
+
+ b->cursor = nir_before_block(nir_start_block(b->impl));
+
+ /* We use instancing for implementing multiview. The actual instance id
+ * is given by dividing instance_id by the number of views in this
+ * subpass.
+ */
+ state->instance_id =
+ nir_idiv(b, nir_load_instance_id(b),
+ nir_imm_int(b, _mesa_bitcount(state->view_mask)));
+ }
+
+ return state->instance_id;
+}
+
+static nir_ssa_def *
+build_view_index(struct lower_multiview_state *state)
+{
+ if (state->view_index == NULL) {
+ nir_builder *b = &state->builder;
+
+ b->cursor = nir_before_block(nir_start_block(b->impl));
+
+ assert(state->view_mask != 0);
+ if (0 && _mesa_bitcount(state->view_mask) == 1) {
+ state->view_index = nir_imm_int(b, ffs(state->view_mask) - 1);
+ } else if (state->builder.shader->stage == MESA_SHADER_VERTEX) {
+ /* We only support 16 viewports */
+ assert((state->view_mask & 0xffff0000) == 0);
+
+ /* We use instancing for implementing multiview. The compacted view
+ * id is given by instance_id % view_count. We then have to convert
+ * that to an actual view id.
+ */
+ nir_ssa_def *compacted =
+ nir_umod(b, nir_load_instance_id(b),
+ nir_imm_int(b, _mesa_bitcount(state->view_mask)));
+
+ if (0 && util_is_power_of_two(state->view_mask + 1)) {
+ /* If we have a full view mask, then compacted is what we want */
+ state->view_index = compacted;
+ } else {
+ /* Now we define a map from compacted view index to the actual
+ * view index that's based on the view_mask. The map is given by
+ * 16 nibbles, each of which is a value from 0 to 15.
+ */
+ uint64_t remap = 0;
+ uint32_t bit, i = 0;
+ for_each_bit(bit, state->view_mask) {
+ assert(bit < 16);
+ remap |= (uint64_t)bit << (i++ * 4);
+ }
+
+ nir_ssa_def *shift = nir_imul(b, compacted, nir_imm_int(b, 4));
+
+ /* One of these days, when we have int64 everywhere, this will be
+ * easier.
+ */
+ nir_ssa_def *shifted;
+ if (remap <= UINT32_MAX) {
+ shifted = nir_ushr(b, nir_imm_int(b, remap), shift);
+ } else {
+ nir_ssa_def *shifted_low =
+ nir_ushr(b, nir_imm_int(b, remap), shift);
+ nir_ssa_def *shifted_high =
+ nir_ushr(b, nir_imm_int(b, remap >> 32),
+ nir_isub(b, shift, nir_imm_int(b, 32)));
+ shifted = nir_bcsel(b, nir_ilt(b, shift, nir_imm_int(b, 32)),
+ shifted_low, shifted_high);
+ }
+ state->view_index = nir_iand(b, shifted, nir_imm_int(b, 0xf));
+ }
+ } else {
+ const struct glsl_type *type = glsl_int_type();
+ if (b->shader->stage == MESA_SHADER_TESS_CTRL ||
+ b->shader->stage == MESA_SHADER_GEOMETRY)
+ type = glsl_array_type(type, 1);
+
+ nir_variable *idx_var =
+ nir_variable_create(b->shader, nir_var_shader_in,
+ type, "view index");
+ idx_var->data.location = VARYING_SLOT_VIEW_INDEX;
+ if (b->shader->stage == MESA_SHADER_FRAGMENT)
+ idx_var->data.interpolation = INTERP_MODE_FLAT;
+
+ if (glsl_type_is_array(type)) {
+ nir_deref_var *deref = nir_deref_var_create(b->shader, idx_var);
+ nir_deref_array *arr = nir_deref_array_create(b->shader);
+ arr->deref.type = glsl_int_type();
+ arr->deref_array_type = nir_deref_array_type_direct;
+ arr->base_offset = 0;
+ deref->deref.child = &arr->deref;
+
+ state->view_index = nir_load_deref_var(b, deref);
+ } else {
+ state->view_index = nir_load_var(b, idx_var);
+ }
+ }
+ }
+
+ return state->view_index;
+}
+
+bool
+anv_nir_lower_multiview(nir_shader *shader, uint32_t view_mask)
+{
+ assert(shader->stage != MESA_SHADER_COMPUTE);
+
+ /* If multiview isn't enabled, we have nothing to do. */
+ if (view_mask == 0)
+ return false;
+
+ struct lower_multiview_state state = {
+ .view_mask = view_mask,
+ };
+
+ /* This pass assumes a single entrypoint */
+ nir_function_impl *entrypoint = nir_shader_get_entrypoint(shader);
+
+ nir_builder_init(&state.builder, entrypoint);
+
+ bool progress = false;
+ nir_foreach_block(block, entrypoint) {
+ nir_foreach_instr_safe(instr, block) {
+ if (instr->type != nir_instr_type_intrinsic)
+ continue;
+
+ nir_intrinsic_instr *load = nir_instr_as_intrinsic(instr);
+
+ if (load->intrinsic != nir_intrinsic_load_instance_id &&
+ load->intrinsic != nir_intrinsic_load_view_index)
+ continue;
+
+ assert(load->dest.is_ssa);
+
+ nir_ssa_def *value;
+ if (load->intrinsic == nir_intrinsic_load_instance_id) {
+ value = build_instance_id(&state);
+ } else {
+ assert(load->intrinsic == nir_intrinsic_load_view_index);
+ value = build_view_index(&state);
+ }
+
+ nir_ssa_def_rewrite_uses(&load->dest.ssa, nir_src_for_ssa(value));
+
+ nir_instr_remove(&load->instr);
+ progress = true;
+ }
+ }
+
+ /* The view index is available in all stages but the instance id is only
+ * available in the VS. If it's not a fragment shader, we need to pass
+ * the view index on to the next stage.
+ */
+ if (shader->stage != MESA_SHADER_FRAGMENT) {
+ nir_ssa_def *view_index = build_view_index(&state);
+
+ nir_builder *b = &state.builder;
+
+ assert(view_index->parent_instr->block == nir_start_block(entrypoint));
+ b->cursor = nir_after_instr(view_index->parent_instr);
+
+ nir_variable *view_index_out =
+ nir_variable_create(shader, nir_var_shader_out,
+ glsl_int_type(), "view index");
+ view_index_out->data.location = VARYING_SLOT_VIEW_INDEX;
+ nir_store_var(b, view_index_out, view_index, 0x1);
+
+ nir_variable *layer_id_out =
+ nir_variable_create(shader, nir_var_shader_out,
+ glsl_int_type(), "layer ID");
+ layer_id_out->data.location = VARYING_SLOT_LAYER;
+ nir_store_var(b, layer_id_out, view_index, 0x1);
+
+ progress = true;
+ }
+
+ if (progress) {
+ nir_metadata_preserve(entrypoint, nir_metadata_block_index |
+ nir_metadata_dominance);
+ }
+
+ return progress;
+}
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