diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources index 706a181c7ab..82a69e6c8af 100644 --- a/src/compiler/Makefile.sources +++ b/src/compiler/Makefile.sources @@ -274,6 +274,7 @@ NIR_FILES = \ nir/nir_lower_io_to_temporaries.c \ nir/nir_lower_io_to_scalar.c \ nir/nir_lower_io_to_vector.c \ + nir/nir_lower_multiview.c \ nir/nir_lower_mediump_outputs.c \ nir/nir_lower_memcpy.c \ nir/nir_lower_memory_model.c \ diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build index af633d87061..1600a02b159 100644 --- a/src/compiler/nir/meson.build +++ b/src/compiler/nir/meson.build @@ -154,6 +154,7 @@ files_libnir = files( 'nir_lower_io_to_temporaries.c', 'nir_lower_io_to_scalar.c', 'nir_lower_io_to_vector.c', + 'nir_lower_multiview.c', 'nir_lower_mediump_outputs.c', 'nir_lower_memcpy.c', 'nir_lower_memory_model.c', diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h index 0af5caef49d..054edf5dae3 100644 --- a/src/compiler/nir/nir.h +++ b/src/compiler/nir/nir.h @@ -4708,6 +4708,10 @@ bool nir_lower_memory_model(nir_shader *shader); bool nir_lower_goto_ifs(nir_shader *shader); +bool nir_shader_uses_view_index(nir_shader *shader); +bool nir_can_lower_multiview(nir_shader *shader); +bool nir_lower_multiview(nir_shader *shader, uint32_t view_mask); + bool nir_normalize_cubemap_coords(nir_shader *shader); void nir_live_ssa_defs_impl(nir_function_impl *impl); diff --git a/src/compiler/nir/nir_lower_multiview.c b/src/compiler/nir/nir_lower_multiview.c new file mode 100644 index 00000000000..ce273dc8c5e --- /dev/null +++ b/src/compiler/nir/nir_lower_multiview.c @@ -0,0 +1,348 @@ +/* + * Copyright © 2016 Intel Corporation + * Copyright © 2020 Valve 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 "nir_control_flow.h" +#include "nir_builder.h" + +/** + * This file implements an optimization for multiview. Some GPU's have a + * special mode which allows the vertex shader (or last stage in the geometry + * pipeline) to create multiple primitives in different layers of the + * framebuffer at once by writing multiple copies of gl_Position. The + * assumption is that in most uses of multiview, the only use of gl_ViewIndex + * is to change the position to implement the parallax effect, and other + * varyings will be the same between the different views. We put the body of + * the original vertex shader in a loop, writing to a different copy of + * gl_Position each loop iteration, and then let other optimizations clean up + * the mess. + */ + +static bool +shader_writes_to_memory(nir_shader *shader) +{ + /* With multiview, we would need to ensure that memory writes happen either + * once or once per view. Since combination of multiview and memory writes + * is not expected, we'll just skip this optimization in this case. + */ + + nir_function_impl *entrypoint = nir_shader_get_entrypoint(shader); + + nir_foreach_block(block, entrypoint) { + nir_foreach_instr(instr, block) { + if (instr->type != nir_instr_type_intrinsic) + continue; + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); + + switch (intrin->intrinsic) { + case nir_intrinsic_deref_atomic_add: + case nir_intrinsic_deref_atomic_imin: + case nir_intrinsic_deref_atomic_umin: + case nir_intrinsic_deref_atomic_imax: + case nir_intrinsic_deref_atomic_umax: + case nir_intrinsic_deref_atomic_and: + case nir_intrinsic_deref_atomic_or: + case nir_intrinsic_deref_atomic_xor: + case nir_intrinsic_deref_atomic_exchange: + case nir_intrinsic_deref_atomic_comp_swap: + case nir_intrinsic_store_ssbo: + case nir_intrinsic_ssbo_atomic_add: + case nir_intrinsic_ssbo_atomic_imin: + case nir_intrinsic_ssbo_atomic_umin: + case nir_intrinsic_ssbo_atomic_imax: + case nir_intrinsic_ssbo_atomic_umax: + case nir_intrinsic_ssbo_atomic_and: + case nir_intrinsic_ssbo_atomic_or: + case nir_intrinsic_ssbo_atomic_xor: + case nir_intrinsic_ssbo_atomic_exchange: + case nir_intrinsic_ssbo_atomic_comp_swap: + case nir_intrinsic_store_shared: + case nir_intrinsic_shared_atomic_add: + case nir_intrinsic_shared_atomic_imin: + case nir_intrinsic_shared_atomic_umin: + case nir_intrinsic_shared_atomic_imax: + case nir_intrinsic_shared_atomic_umax: + case nir_intrinsic_shared_atomic_and: + case nir_intrinsic_shared_atomic_or: + case nir_intrinsic_shared_atomic_xor: + case nir_intrinsic_shared_atomic_exchange: + case nir_intrinsic_shared_atomic_comp_swap: + case nir_intrinsic_image_deref_store: + case nir_intrinsic_image_deref_atomic_add: + case nir_intrinsic_image_deref_atomic_umin: + case nir_intrinsic_image_deref_atomic_umax: + case nir_intrinsic_image_deref_atomic_imin: + case nir_intrinsic_image_deref_atomic_imax: + case nir_intrinsic_image_deref_atomic_and: + case nir_intrinsic_image_deref_atomic_or: + case nir_intrinsic_image_deref_atomic_xor: + case nir_intrinsic_image_deref_atomic_exchange: + case nir_intrinsic_image_deref_atomic_comp_swap: + return true; + + default: + /* Keep walking. */ + break; + } + } + } + + return false; +} + +bool +nir_shader_uses_view_index(nir_shader *shader) +{ + nir_function_impl *entrypoint = nir_shader_get_entrypoint(shader); + + nir_foreach_block(block, entrypoint) { + nir_foreach_instr(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_view_index) + return true; + } + } + + return false; +} + +static bool +shader_only_position_uses_view_index(nir_shader *shader) +{ + nir_shader *shader_no_position = nir_shader_clone(NULL, shader); + nir_function_impl *entrypoint = nir_shader_get_entrypoint(shader_no_position); + + /* Remove the store position from a cloned shader. */ + nir_foreach_block(block, entrypoint) { + nir_foreach_instr_safe(instr, block) { + if (instr->type != nir_instr_type_intrinsic) + continue; + + nir_intrinsic_instr *store = nir_instr_as_intrinsic(instr); + if (store->intrinsic != nir_intrinsic_store_deref) + continue; + + nir_variable *var = nir_intrinsic_get_var(store, 0); + if (var->data.location != VARYING_SLOT_POS) + continue; + + nir_instr_remove(&store->instr); + } + } + + /* Clean up shader so unused load_view_index intrinsics are removed. */ + bool progress; + do { + progress = false; + progress |= nir_opt_dead_cf(shader_no_position); + + /* Peephole select will drop if-blocks that have then and else empty, + * which will remove the usage of an SSA in the condition. + */ + progress |= nir_opt_peephole_select(shader_no_position, 0, false, false); + + progress |= nir_opt_dce(shader_no_position); + } while (progress); + + bool uses_view_index = nir_shader_uses_view_index(shader_no_position); + + ralloc_free(shader_no_position); + return !uses_view_index; +} + +/* Return true if it's safe to call nir_lower_multiview() on this vertex + * shader. Note that this only handles driver-agnostic checks, i.e. things + * which would make nir_lower_multiview() incorrect. Any driver-specific + * checks, e.g. for sufficient varying space or performance considerations, + * should be handled in the driver. + * + * Note that we don't handle the more complex checks needed for lowering + * pipelines with geometry or tessellation shaders. + */ + +bool +nir_can_lower_multiview(nir_shader *shader) +{ + bool writes_position = false; + nir_foreach_shader_out_variable(var, shader) { + if (var->data.location == VARYING_SLOT_POS) { + writes_position = true; + break; + } + } + + /* Don't bother handling this edge case. */ + if (!writes_position) + return false; + + return !shader_writes_to_memory(shader) && + shader_only_position_uses_view_index(shader); +} + +/** + * The lowering. Call with the last active geometry stage. + */ + +bool +nir_lower_multiview(nir_shader *shader, uint32_t view_mask) +{ + assert(shader->info.stage != MESA_SHADER_FRAGMENT); + int view_count = util_bitcount(view_mask); + + nir_function_impl *entrypoint = nir_shader_get_entrypoint(shader); + + /* Update position to refer to an array. */ + nir_variable *pos_var = NULL; + nir_foreach_shader_out_variable(var, shader) { + if (var->data.location == VARYING_SLOT_POS) { + assert(var->type == glsl_vec4_type()); + var->type = glsl_array_type(glsl_vec4_type(), view_count, 0); + var->data.per_view = true; + pos_var = var; + break; + } + } + + assert(pos_var); + + nir_cf_list body; + nir_cf_list_extract(&body, &entrypoint->body); + + nir_builder b; + nir_builder_init(&b, entrypoint); + b.cursor = nir_after_cf_list(&entrypoint->body); + + /* Loop Index will go from 0 to view_count. */ + nir_variable *loop_index_var = + nir_local_variable_create(entrypoint, glsl_uint_type(), "loop_index"); + nir_deref_instr *loop_index_deref = nir_build_deref_var(&b, loop_index_var); + nir_store_deref(&b, loop_index_deref, nir_imm_int(&b, 0), 1); + + /* Array of view index values that are active in the loop. Note that the + * loop index only matches the view index if there are no gaps in the + * view_mask. + */ + nir_variable *view_index_var = nir_local_variable_create( + entrypoint, glsl_array_type(glsl_uint_type(), view_count, 0), "view_index"); + nir_deref_instr *view_index_deref = nir_build_deref_var(&b, view_index_var); + { + int array_position = 0; + uint32_t view_mask_temp = view_mask; + while (view_mask_temp) { + uint32_t view_index = u_bit_scan(&view_mask_temp); + nir_store_deref(&b, nir_build_deref_array_imm(&b, view_index_deref, array_position), + nir_imm_int(&b, view_index), 1); + array_position++; + } + } + + /* Create the equivalent of + * + * while (true): + * if (loop_index >= view_count): + * break + * + * view_index = active_indices[loop_index] + * pos_deref = &pos[loop_index] + * + * # Placeholder for the body to be reinserted. + * + * loop_index += 1 + * + * Later both `view_index` and `pos_deref` will be used to rewrite the + * original shader body. + */ + + nir_loop* loop = nir_push_loop(&b); + + nir_ssa_def *loop_index = nir_load_deref(&b, loop_index_deref); + nir_ssa_def *cmp = nir_ige(&b, loop_index, nir_imm_int(&b, view_count)); + nir_if *loop_check = nir_push_if(&b, cmp); + nir_jump(&b, nir_jump_break); + nir_pop_if(&b, loop_check); + + nir_ssa_def *view_index = + nir_load_deref(&b, nir_build_deref_array(&b, view_index_deref, loop_index)); + nir_deref_instr *pos_deref = + nir_build_deref_array(&b, nir_build_deref_var(&b, pos_var), loop_index); + + nir_store_deref(&b, loop_index_deref, nir_iadd_imm(&b, loop_index, 1), 1); + nir_pop_loop(&b, loop); + + /* Reinsert the body. */ + b.cursor = nir_after_instr(&pos_deref->instr); + nir_cf_reinsert(&body, b.cursor); + + nir_foreach_block(block, entrypoint) { + nir_foreach_instr_safe(instr, block) { + if (instr->type != nir_instr_type_intrinsic) + continue; + + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); + + switch (intrin->intrinsic) { + case nir_intrinsic_load_view_index: { + assert(intrin->dest.is_ssa); + nir_ssa_def_rewrite_uses(&intrin->dest.ssa, nir_src_for_ssa(view_index)); + break; + } + + case nir_intrinsic_store_deref: { + nir_variable *var = nir_intrinsic_get_var(intrin, 0); + if (var == pos_var) { + nir_deref_instr *old_deref = nir_src_as_deref(intrin->src[0]); + + nir_instr_rewrite_src(instr, &intrin->src[0], + nir_src_for_ssa(&pos_deref->dest.ssa)); + + /* Remove old deref since it has the wrong type. */ + nir_deref_instr_remove_if_unused(old_deref); + } + break; + } + + case nir_intrinsic_load_deref: + if (nir_intrinsic_get_var(intrin, 0) == pos_var) { + unreachable("Should have lowered I/O to temporaries " + "so no load_deref on position output is expected."); + } + break; + + case nir_intrinsic_copy_deref: + unreachable("Should have lowered copy_derefs at this point"); + break; + + default: + /* Do nothing. */ + break; + } + } + } + + nir_metadata_preserve(entrypoint, nir_metadata_none); + return true; +} +