src/compiler/nir/nir_lower_interpolation.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 /*
  25  * This lower pass lowers load_interpolated_input for various interpolation
  26  * modes (as configured via nir_lower_interpolation_options bitmask) into
  27  * load_attribute_deltas plus alu instructions:
  28  *
  29  *    vec3 ad = load_attribute_deltas(varying_slot)
  30  *    float result = ad.x + ad.y * j + ad.z * i
  31  *
  32  */
  33
  34 #include "nir.h"
  35 #include "nir_builder.h"
  36
  37 static bool
  38 nir_lower_interpolation_block(nir_block *block, nir_builder *b,
  39                               nir_lower_interpolation_options options)
  40 {
  41    bool progress = false;
  42
  43    nir_foreach_instr_safe(instr, block) {
  44       if (instr->type != nir_instr_type_intrinsic)
  45          continue;
  46
  47       nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
  48
  49       if (intr->intrinsic != nir_intrinsic_load_interpolated_input)
  50          continue;
  51
  52       assert(intr->dest.is_ssa);
  53       assert(intr->src[0].is_ssa);
  54       assert(intr->src[1].is_ssa);
  55
  56       nir_intrinsic_instr *bary_intrinsic =
  57          nir_instr_as_intrinsic(intr->src[0].ssa->parent_instr);
  58
  59       /* Leave VARYING_SLOT_POS alone */
  60       if (nir_intrinsic_base(intr) == VARYING_SLOT_POS)
  61          continue;
  62
  63       const enum glsl_interp_mode interp_mode =
  64          nir_intrinsic_interp_mode(bary_intrinsic);
  65
  66       /* We need actual interpolation modes by the time we get here */
  67       assert(interp_mode != INTERP_MODE_NONE);
  68
  69       /* Only lower for inputs that need interpolation */
  70       if (interp_mode != INTERP_MODE_SMOOTH &&
  71           interp_mode != INTERP_MODE_NOPERSPECTIVE)
  72          continue;
  73
  74       nir_intrinsic_op op = bary_intrinsic->intrinsic;
  75
  76       switch (op) {
  77       case nir_intrinsic_load_barycentric_at_sample:
  78          if (options & nir_lower_interpolation_at_sample)
  79             break;
  80          continue;
  81       case nir_intrinsic_load_barycentric_at_offset:
  82          if (options & nir_lower_interpolation_at_offset)
  83             break;
  84          continue;
  85       case nir_intrinsic_load_barycentric_centroid:
  86          if (options & nir_lower_interpolation_centroid)
  87             break;
  88          continue;
  89       case nir_intrinsic_load_barycentric_pixel:
  90          if (options & nir_lower_interpolation_pixel)
  91             break;
  92          continue;
  93       case nir_intrinsic_load_barycentric_sample:
  94          if (options & nir_lower_interpolation_sample)
  95             break;
  96          continue;
  97       default:
  98          continue;
  99       }
 100
 101       b->cursor = nir_before_instr(instr);
 102
 103       nir_ssa_def *comps[NIR_MAX_VEC_COMPONENTS];
 104       for (int i = 0; i < intr->num_components; i++) {
 105          nir_intrinsic_instr *load_iid =
 106             nir_intrinsic_instr_create(b->shader,
 107                                        nir_intrinsic_load_fs_input_interp_deltas);
 108          load_iid->src[0] = nir_src_for_ssa(intr->src[1].ssa);
 109          nir_ssa_dest_init(&load_iid->instr, &load_iid->dest,
 110                            3, 32, NULL);
 111          nir_intrinsic_set_base(load_iid, nir_intrinsic_base(intr));
 112          nir_intrinsic_set_component(load_iid,
 113                                      nir_intrinsic_component(intr) + i);
 114          nir_intrinsic_set_io_semantics(load_iid,
 115                                         nir_intrinsic_io_semantics(intr));
 116          nir_builder_instr_insert(b, &load_iid->instr);
 117
 118          nir_ssa_def *iid = &load_iid->dest.ssa;
 119          nir_ssa_def *bary = intr->src[0].ssa;
 120          nir_ssa_def *val;
 121
 122          val = nir_ffma(b, nir_channel(b, bary, 1),
 123                            nir_channel(b, iid, 1),
 124                            nir_channel(b, iid, 0));
 125          val = nir_ffma(b, nir_channel(b, bary, 0),
 126                            nir_channel(b, iid, 2),
 127                            val);
 128
 129          comps[i] = val;
 130       }
 131       nir_ssa_def *vec = nir_vec(b, comps, intr->num_components);
 132       nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(vec));
 133
 134       progress = true;
 135    }
 136
 137    return progress;
 138 }
 139
 140 static bool
 141 nir_lower_interpolation_impl(nir_function_impl *impl,
 142                              nir_lower_interpolation_options options)
 143 {
 144    bool progress = false;
 145    nir_builder builder;
 146    nir_builder_init(&builder, impl);
 147
 148    nir_foreach_block(block, impl) {
 149       progress |= nir_lower_interpolation_block(block, &builder, options);
 150    }
 151
 152    nir_metadata_preserve(impl, nir_metadata_block_index |
 153                                nir_metadata_dominance);
 154    return progress;
 155 }
 156
 157 bool
 158 nir_lower_interpolation(nir_shader *shader, nir_lower_interpolation_options options)
 159 {
 160    bool progress = false;
 161
 162    nir_foreach_function(function, shader) {
 163       if (function->impl)
 164          progress |= nir_lower_interpolation_impl(function->impl, options);
 165    }
 166
 167    return progress;
 168 }