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/*
* 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->info.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, util_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 (util_bitcount(state->view_mask) == 1) {
/* Set the view index directly. */
state->view_index = nir_imm_int(b, ffs(state->view_mask) - 1);
} else if (state->builder.shader->info.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, util_bitcount(state->view_mask)));
if (util_is_power_of_two_or_zero(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->info.stage == MESA_SHADER_TESS_CTRL ||
b->shader->info.stage == MESA_SHADER_GEOMETRY)
type = glsl_array_type(type, 1, 0);
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->info.stage == MESA_SHADER_FRAGMENT)
idx_var->data.interpolation = INTERP_MODE_FLAT;
nir_deref_instr *deref = nir_build_deref_var(b, idx_var);
if (glsl_type_is_array(type))
deref = nir_build_deref_array_imm(b, deref, 0);
state->view_index = nir_load_deref(b, deref);
}
}
return state->view_index;
}
bool
anv_nir_lower_multiview(nir_shader *shader, uint32_t view_mask)
{
assert(shader->info.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->info.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);
/* Unless there is only one possible view index (that would be set
* directly), pass it to the next stage. */
if (util_bitcount(state.view_mask) != 1) {
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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