177 lines
6.1 KiB
C
177 lines
6.1 KiB
C
/*
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* Copyright © 2020 Raspberry Pi Ltd
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#include "compiler/v3d_compiler.h"
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#include "compiler/nir/nir_builder.h"
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#include <math.h>
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/**
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* Lowers line smoothing by modifying the alpha component of fragment outputs
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* using the distance from the center of the line.
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*/
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struct lower_line_smooth_state {
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nir_shader *shader;
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nir_variable *coverage;
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};
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static void
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lower_line_smooth_intrinsic(struct lower_line_smooth_state *state,
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nir_builder *b,
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nir_intrinsic_instr *intr)
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{
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b->cursor = nir_before_instr(&intr->instr);
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nir_ssa_def *one = nir_imm_float(b, 1.0f);
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nir_ssa_def *coverage = nir_load_var(b, state->coverage);
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nir_ssa_def *new_val = nir_fmul(b, nir_vec4(b, one, one, one, coverage),
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intr->src[0].ssa);
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nir_instr_rewrite_src(&intr->instr,
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&intr->src[0],
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nir_src_for_ssa(new_val));
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}
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static bool
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lower_line_smooth_func(struct lower_line_smooth_state *state,
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nir_function_impl *impl)
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{
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bool progress = false;
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nir_builder b;
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nir_builder_init(&b, impl);
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nir_foreach_block(block, impl) {
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nir_foreach_instr_safe(instr, block) {
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if (instr->type != nir_instr_type_intrinsic)
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continue;
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nir_intrinsic_instr *intr =
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nir_instr_as_intrinsic(instr);
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if (intr->intrinsic != nir_intrinsic_store_output ||
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nir_intrinsic_base(intr) != 0 ||
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intr->num_components != 4 ||
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!intr->src[0].is_ssa)
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continue;
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lower_line_smooth_intrinsic(state, &b, intr);
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progress = true;
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}
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}
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return progress;
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}
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static void
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initialise_coverage_var(struct lower_line_smooth_state *state,
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nir_function_impl *impl)
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{
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nir_builder b;
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nir_builder_init(&b, impl);
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b.cursor = nir_before_block(nir_start_block(impl));
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nir_ssa_def *line_width = nir_load_line_width(&b);
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nir_ssa_def *real_line_width = nir_load_aa_line_width(&b);
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/* The line coord varies from 0.0 to 1.0 across the width of the line */
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nir_ssa_def *line_coord = nir_load_line_coord(&b);
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/* fabs(line_coord - 0.5) * real_line_width */
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nir_ssa_def *pixels_from_center =
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nir_fmul(&b, real_line_width,
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nir_fabs(&b, nir_fsub(&b, line_coord,
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nir_imm_float(&b, 0.5f))));
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/* 0.5 - 1/√2 * (pixels_from_center - line_width * 0.5) */
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nir_ssa_def *coverage =
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nir_fsub(&b,
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nir_imm_float(&b, 0.5f),
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nir_fmul(&b,
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nir_imm_float(&b, 1.0f / M_SQRT2),
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nir_fsub(&b, pixels_from_center,
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nir_fmul(&b,
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line_width,
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nir_imm_float(&b, 0.5f)))));
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/* Discard fragments that aren’t covered at all by the line */
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nir_ssa_def *outside = nir_fge(&b, nir_imm_float(&b, 0.0f), coverage);
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nir_discard_if(&b, outside);
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/* Clamp to at most 1.0. If it was less than 0.0 then the fragment will
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* be discarded so we don’t need to handle that.
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*/
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nir_ssa_def *clamped = nir_fmin(&b, coverage, nir_imm_float(&b, 1.0f));
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nir_store_var(&b, state->coverage, clamped, 0x1 /* writemask */);
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}
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static nir_variable *
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make_coverage_var(nir_shader *s)
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{
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nir_variable *var = nir_variable_create(s,
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nir_var_shader_temp,
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glsl_float_type(),
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"line_coverage");
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var->data.how_declared = nir_var_hidden;
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return var;
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}
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bool
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v3d_nir_lower_line_smooth(nir_shader *s)
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{
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bool progress = false;
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assert(s->info.stage == MESA_SHADER_FRAGMENT);
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struct lower_line_smooth_state state = {
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.shader = s,
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.coverage = make_coverage_var(s),
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};
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nir_foreach_function(function, s) {
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if (function->is_entrypoint)
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initialise_coverage_var(&state, function->impl);
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progress |= lower_line_smooth_func(&state, function->impl);
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if (progress) {
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nir_metadata_preserve(function->impl,
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nir_metadata_block_index |
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nir_metadata_dominance);
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} else {
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nir_metadata_preserve(function->impl, nir_metadata_all);
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}
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}
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return progress;
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}
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