nir: Add a lowering pass for point smoothing
When point smoothing is enabled then this lowering pass will modifies the alpha component of every write to fragment output. Anti-aliased points get rounded with respect to their radius instead of square. Reviewed-by: Marek Olšák <marek.olsak@amd.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15117>
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Marek Olšák

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cad4908fa0
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30865756db
@@ -187,6 +187,7 @@ files_libnir = files(
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'nir_lower_pntc_ytransform.c',
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'nir_lower_pntc_ytransform.c',
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'nir_lower_point_size.c',
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'nir_lower_point_size.c',
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'nir_lower_point_size_mov.c',
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'nir_lower_point_size_mov.c',
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'nir_lower_point_smooth.c',
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'nir_lower_poly_line_smooth.c',
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'nir_lower_poly_line_smooth.c',
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'nir_lower_printf.c',
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'nir_lower_printf.c',
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'nir_lower_regs_to_ssa.c',
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'nir_lower_regs_to_ssa.c',
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@@ -5680,8 +5680,8 @@ nir_opt_preamble(nir_shader *shader,
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nir_function_impl *nir_shader_get_preamble(nir_shader *shader);
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nir_function_impl *nir_shader_get_preamble(nir_shader *shader);
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bool
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bool nir_lower_point_smooth(nir_shader *shader);
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nir_lower_poly_line_smooth(nir_shader *shader, unsigned num_smooth_aa_sample);
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bool nir_lower_poly_line_smooth(nir_shader *shader, unsigned num_smooth_aa_sample);
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#include "nir_inline_helpers.h"
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#include "nir_inline_helpers.h"
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94
src/compiler/nir/nir_lower_point_smooth.c
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94
src/compiler/nir/nir_lower_point_smooth.c
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@@ -0,0 +1,94 @@
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/*
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* Copyright © 2022 Advanced Micro Devices, Inc.
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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 "nir.h"
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#include "nir_builder.h"
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#include "nir_builtin_builder.h"
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/**
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* This NIR lowers pass for point smoothing by modifying the alpha value of
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* fragment outputs using the distance from the center of the point.
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* Anti-aliased points get rounded with respect to their radius.
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*/
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static bool
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lower_point_smooth(nir_builder *b, nir_instr *instr, UNUSED void *_state)
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{
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if (instr->type != nir_instr_type_intrinsic)
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return false;
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nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
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if (intr->intrinsic != nir_intrinsic_store_output)
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return false;
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int location = nir_intrinsic_io_semantics(intr).location;
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if ((location != FRAG_RESULT_COLOR && location < FRAG_RESULT_DATA0) ||
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nir_intrinsic_src_type(intr) != nir_type_float32)
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return false;
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assert(intr->src[0].is_ssa);
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assert(intr->num_components == 4);
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b->cursor = nir_before_instr(&intr->instr);
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nir_ssa_def *coord = nir_build_load_point_coord_maybe_flipped(b);
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/* point_size = 1.0 / dFdx(gl_PointCoord.x); */
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nir_ssa_def *point_size = nir_frcp(b, nir_fddx(b, nir_channel(b, coord, 0)));
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/* radius = point_size * 0.5 */
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nir_ssa_def *radius = nir_fmul_imm(b, point_size, 0.5);;
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/**
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* Compute the distance of point from centre
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* distance = √ (x - 0.5)^2 + (y - 0.5)^2
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*/
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nir_ssa_def *distance = nir_fast_distance(b, coord,
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nir_imm_vec2(b, 0.5, 0.5));
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distance = nir_fmul(b, distance, point_size);
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/* alpha = min(max(radius - distance, 0.0), 1.0) */
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nir_ssa_def *coverage = nir_fsat(b, nir_fsub(b, radius, distance));
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/* Discard fragments that are not covered by the point */
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nir_discard_if(b, nir_feq(b, nir_imm_float(b, 0.0f), coverage));
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/* Write out the fragment color*vec4(1, 1, 1, coverage)*/
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nir_ssa_def *one = nir_imm_float(b, 1.0f);
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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(instr, &intr->src[0], nir_src_for_ssa(new_val));
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return true;
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}
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bool
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nir_lower_point_smooth(nir_shader *shader)
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{
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assert(shader->info.stage == MESA_SHADER_FRAGMENT);
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return nir_shader_instructions_pass(shader, lower_point_smooth,
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nir_metadata_loop_analysis |
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nir_metadata_block_index |
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nir_metadata_dominance, NULL);
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}
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