src/freedreno/ir3/ir3_nir_lower_load_barycentric_at_sample.c

   1 /*
   2  * Copyright © 2019 Google, Inc.
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include "ir3_nir.h"
  25 #include "compiler/nir/nir_builder.h"
  26
  27 /**
  28  * This pass lowers load_barycentric_at_sample to load_sample_pos_from_id
  29  * plus load_barycentric_at_offset.
  30  *
  31  * It also lowers load_sample_pos to load_sample_pos_from_id, mostly because
  32  * that needs to happen at the same early stage (before wpos_ytransform)
  33  */
  34
  35 static nir_ssa_def *
  36 load_sample_pos(nir_builder *b, nir_ssa_def *samp_id)
  37 {
  38         nir_intrinsic_instr *load_sp =
  39                         nir_intrinsic_instr_create(b->shader,
  40                                         nir_intrinsic_load_sample_pos_from_id);
  41         load_sp->src[0] = nir_src_for_ssa(samp_id);
  42         nir_ssa_dest_init(&load_sp->instr, &load_sp->dest, 2, 32, NULL);
  43         nir_builder_instr_insert(b, &load_sp->instr);
  44
  45         return &load_sp->dest.ssa;
  46 }
  47
  48 static nir_ssa_def *
  49 lower_load_barycentric_at_sample(nir_builder *b, nir_intrinsic_instr *intr)
  50 {
  51         nir_ssa_def *pos = load_sample_pos(b, intr->src[0].ssa);
  52
  53         nir_intrinsic_instr *load_bary_at_offset =
  54                         nir_intrinsic_instr_create(b->shader,
  55                                         nir_intrinsic_load_barycentric_at_offset);
  56         load_bary_at_offset->src[0] = nir_src_for_ssa(pos);
  57         nir_ssa_dest_init(&load_bary_at_offset->instr,
  58                         &load_bary_at_offset->dest, 2, 32, NULL);
  59         nir_builder_instr_insert(b, &load_bary_at_offset->instr);
  60
  61         return &load_bary_at_offset->dest.ssa;
  62 }
  63
  64 static nir_ssa_def *
  65 lower_load_sample_pos(nir_builder *b, nir_intrinsic_instr *intr)
  66 {
  67         nir_ssa_def *pos = load_sample_pos(b, nir_load_sample_id(b));
  68
  69         /* Note that gl_SamplePosition is offset by +vec2(0.5, 0.5) vs the
  70          * offset passed to interpolateAtOffset().   See
  71          * dEQP-GLES31.functional.shaders.multisample_interpolation.interpolate_at_offset.at_sample_position.default_framebuffer
  72          * for example.
  73          */
  74         nir_ssa_def *half = nir_imm_float(b, 0.5);
  75         return nir_fadd(b, pos, nir_vec2(b, half, half));
  76 }
  77
  78 static nir_ssa_def *
  79 ir3_nir_lower_load_barycentric_at_sample_instr(nir_builder *b,
  80                 nir_instr *instr, void *data)
  81 {
  82         nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
  83
  84         if (intr->intrinsic == nir_intrinsic_load_sample_pos)
  85                 return lower_load_sample_pos(b, intr);
  86         else
  87                 return lower_load_barycentric_at_sample(b, intr);
  88 }
  89
  90 static bool
  91 ir3_nir_lower_load_barycentric_at_sample_filter(const nir_instr *instr,
  92                 const void *data)
  93 {
  94         if (instr->type != nir_instr_type_intrinsic)
  95                 return false;
  96         nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
  97         return (intr->intrinsic == nir_intrinsic_load_barycentric_at_sample ||
  98                         intr->intrinsic == nir_intrinsic_load_sample_pos);
  99 }
 100
 101 bool
 102 ir3_nir_lower_load_barycentric_at_sample(nir_shader *shader)
 103 {
 104         debug_assert(shader->info.stage == MESA_SHADER_FRAGMENT);
 105
 106         return nir_shader_lower_instructions(shader,
 107                         ir3_nir_lower_load_barycentric_at_sample_filter,
 108                         ir3_nir_lower_load_barycentric_at_sample_instr,
 109                         NULL);
 110 }