/* * 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" #include "util/u_debug.h" /** * This file implements the lowering required for VK_KHR_multiview. * * When possible, Primitive Replication is used and the shader is modified to * make gl_Position an array and fill it with values for each view. * * Otherwise 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_def *instance_id_with_views; nir_def *instance_id; nir_def *view_index; }; static nir_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_after_instr(state->instance_id_with_views->parent_instr); /* 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, state->instance_id_with_views, nir_imm_int(b, util_bitcount(state->view_mask))); } return state->instance_id; } static nir_def * build_view_index(struct lower_multiview_state *state) { assert(state->builder.shader->info.stage != MESA_SHADER_FRAGMENT); if (state->view_index == NULL) { nir_builder *b = &state->builder; b->cursor = nir_after_instr(state->instance_id_with_views->parent_instr); 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_def *compacted = nir_umod_imm(b, state->instance_id_with_views, 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 i = 0; u_foreach_bit(bit, state->view_mask) { assert(bit < 16); remap |= (uint64_t)bit << (i++ * 4); } nir_def *shift = nir_imul_imm(b, compacted, 4); /* One of these days, when we have int64 everywhere, this will be * easier. */ nir_def *shifted; if (remap <= UINT32_MAX) { shifted = nir_ushr(b, nir_imm_int(b, remap), shift); } else { nir_def *shifted_low = nir_ushr(b, nir_imm_int(b, remap), shift); nir_def *shifted_high = nir_ushr(b, nir_imm_int(b, remap >> 32), nir_iadd_imm(b, shift, -32)); shifted = nir_bcsel(b, nir_ilt_imm(b, shift, 32), shifted_low, shifted_high); } state->view_index = nir_iand_imm(b, shifted, 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; } static bool is_load_view_index(const nir_instr *instr, const void *data) { return instr->type == nir_instr_type_intrinsic && nir_instr_as_intrinsic(instr)->intrinsic == nir_intrinsic_load_view_index; } static nir_def * replace_load_view_index_with_zero(struct nir_builder *b, nir_instr *instr, void *data) { assert(is_load_view_index(instr, data)); return nir_imm_zero(b, 1, 32); } static nir_def * replace_load_view_index_with_layer_id(struct nir_builder *b, nir_instr *instr, void *data) { assert(is_load_view_index(instr, data)); return nir_load_layer_id(b); } bool anv_nir_lower_multiview(nir_shader *shader, uint32_t view_mask, bool use_primitive_replication) { assert(shader->info.stage != MESA_SHADER_COMPUTE); /* If multiview isn't enabled, just lower the ViewIndex builtin to zero. */ if (view_mask == 0) { return nir_shader_lower_instructions(shader, is_load_view_index, replace_load_view_index_with_zero, NULL); } if (shader->info.stage == MESA_SHADER_FRAGMENT) { return nir_shader_lower_instructions(shader, is_load_view_index, replace_load_view_index_with_layer_id, NULL); } /* This pass assumes a single entrypoint */ nir_function_impl *entrypoint = nir_shader_get_entrypoint(shader); /* Primitive Replication allows a shader to write different positions for * each view in the same execution. If only the position depends on the * view, then it is possible to use the feature instead of instancing to * implement multiview. */ if (use_primitive_replication) { bool progress = nir_lower_multiview(shader, view_mask); if (progress) { nir_builder b = nir_builder_at(nir_before_impl(entrypoint)); /* Fill Layer ID with zero. Replication will use that as base to * apply the RTAI offsets. */ 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, nir_imm_zero(&b, 1, 32), 0x1); } return progress; } struct lower_multiview_state state = { .view_mask = view_mask, }; state.builder = nir_builder_at(nir_before_impl(entrypoint)); nir_builder *b = &state.builder; /* Save the original "instance ID" which is the actual instance ID * multiplied by the number of views. */ state.instance_id_with_views = nir_load_instance_id(b); /* 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. */ nir_def *view_index = build_view_index(&state); 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. */ nir_variable *view_index_out = NULL; if (util_bitcount(state.view_mask) != 1) { 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_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; if (shader->info.stage != MESA_SHADER_GEOMETRY) { if (view_index_out) nir_store_var(b, view_index_out, view_index, 0x1); nir_store_var(b, layer_id_out, view_index, 0x1); } 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); switch (load->intrinsic) { case nir_intrinsic_load_instance_id: if (&load->def != state.instance_id_with_views) { nir_def_replace(&load->def, build_instance_id(&state)); } break; case nir_intrinsic_load_view_index: nir_def_replace(&load->def, view_index); break; case nir_intrinsic_emit_vertex_with_counter: /* In geometry shaders, outputs become undefined after every * EmitVertex() call. We need to re-emit them for each vertex. */ b->cursor = nir_before_instr(instr); if (view_index_out) nir_store_var(b, view_index_out, view_index, 0x1); nir_store_var(b, layer_id_out, view_index, 0x1); break; default: break; } } } nir_metadata_preserve(entrypoint, nir_metadata_control_flow); return true; } bool anv_check_for_primitive_replication(struct anv_device *device, VkShaderStageFlags stages, nir_shader **shaders, uint32_t view_mask) { assert(device->info->ver >= 12); static int primitive_replication_max_views = -1; if (primitive_replication_max_views < 0) { /* TODO: Figure out why we are not getting same benefits for larger than * 2 views. For now use Primitive Replication just for the 2-view case * by default. */ const unsigned default_max_views = 2; primitive_replication_max_views = MIN2(MAX_VIEWS_FOR_PRIMITIVE_REPLICATION, debug_get_num_option("ANV_PRIMITIVE_REPLICATION_MAX_VIEWS", default_max_views)); } /* TODO: We should be able to support replication at 'geometry' stages * later than Vertex. In that case only the last stage can refer to * gl_ViewIndex. */ if (stages & ~(VK_SHADER_STAGE_VERTEX_BIT | VK_SHADER_STAGE_FRAGMENT_BIT)) return false; /* It's possible we have no vertex shader yet (with pipeline libraries) */ if (!(stages & VK_SHADER_STAGE_VERTEX_BIT)) return false; int view_count = util_bitcount(view_mask); if (view_count == 1 || view_count > primitive_replication_max_views) return false; return nir_can_lower_multiview(shaders[MESA_SHADER_VERTEX]); }