src/compiler/nir/nir_lower_two_sided_color.c

   1 /*
   2  * Copyright © 2015 Red Hat
   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  * Authors:
  24  *    Rob Clark <robclark@freedesktop.org>
  25  */
  26
  27 #include "nir.h"
  28 #include "nir_builder.h"
  29
  30 #define MAX_COLORS 2  /* VARYING_SLOT_COL0/COL1 */
  31
  32 typedef struct {
  33    nir_builder   b;
  34    nir_shader   *shader;
  35    bool face_sysval;
  36    struct {
  37       nir_variable *front;        /* COLn */
  38       nir_variable *back;         /* BFCn */
  39    } colors[MAX_COLORS];
  40    nir_variable *face;
  41    int colors_count;
  42 } lower_2side_state;
  43
  44
  45 /* Lowering pass for fragment shaders to emulated two-sided-color.  For
  46  * each COLOR input, a corresponding BCOLOR input is created, and bcsel
  47  * instruction used to select front or back color based on FACE.
  48  */
  49
  50 static nir_variable *
  51 create_input(nir_shader *shader, gl_varying_slot slot,
  52              enum glsl_interp_mode interpolation)
  53 {
  54    nir_variable *var = nir_variable_create(shader, nir_var_shader_in,
  55                                            glsl_vec4_type(), NULL);
  56
  57    var->data.driver_location = shader->num_inputs++;
  58    var->name = ralloc_asprintf(var, "in_%d", var->data.driver_location);
  59    var->data.index = 0;
  60    var->data.location = slot;
  61    var->data.interpolation = interpolation;
  62
  63    return var;
  64 }
  65
  66 static nir_variable *
  67 create_face_input(nir_shader *shader)
  68 {
  69    nir_variable *var =
  70       nir_find_variable_with_location(shader, nir_var_shader_in,
  71                                       VARYING_SLOT_FACE);
  72
  73    if (var == NULL) {
  74       var = nir_variable_create(shader, nir_var_shader_in,
  75                                 glsl_bool_type(), "gl_FrontFacing");
  76
  77       var->data.driver_location = shader->num_inputs++;
  78       var->data.index = 0;
  79       var->data.location = VARYING_SLOT_FACE;
  80       var->data.interpolation = INTERP_MODE_FLAT;
  81    }
  82
  83    return var;
  84 }
  85
  86 static nir_ssa_def *
  87 load_input(nir_builder *b, nir_variable *in)
  88 {
  89    nir_intrinsic_instr *load;
  90
  91    load = nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_input);
  92    load->num_components = 4;
  93    nir_intrinsic_set_base(load, in->data.driver_location);
  94    load->src[0] = nir_src_for_ssa(nir_imm_int(b, 0));
  95    nir_ssa_dest_init(&load->instr, &load->dest, 4, 32, NULL);
  96    nir_builder_instr_insert(b, &load->instr);
  97
  98    return &load->dest.ssa;
  99 }
 100
 101 static int
 102 setup_inputs(lower_2side_state *state)
 103 {
 104    /* find color inputs: */
 105    nir_foreach_shader_in_variable(var, state->shader) {
 106       switch (var->data.location) {
 107       case VARYING_SLOT_COL0:
 108       case VARYING_SLOT_COL1:
 109          assert(state->colors_count < ARRAY_SIZE(state->colors));
 110          state->colors[state->colors_count].front = var;
 111          state->colors_count++;
 112          break;
 113       }
 114    }
 115
 116    /* if we don't have any color inputs, nothing to do: */
 117    if (state->colors_count == 0)
 118       return -1;
 119
 120    /* add required back-face color inputs: */
 121    for (int i = 0; i < state->colors_count; i++) {
 122       gl_varying_slot slot;
 123
 124       if (state->colors[i].front->data.location == VARYING_SLOT_COL0)
 125          slot = VARYING_SLOT_BFC0;
 126       else
 127          slot = VARYING_SLOT_BFC1;
 128
 129       state->colors[i].back = create_input(
 130             state->shader, slot,
 131             state->colors[i].front->data.interpolation);
 132    }
 133
 134    if (!state->face_sysval)
 135       state->face = create_face_input(state->shader);
 136
 137    return 0;
 138 }
 139
 140 static bool
 141 nir_lower_two_sided_color_block(nir_block *block,
 142                                 lower_2side_state *state)
 143 {
 144    nir_builder *b = &state->b;
 145
 146    nir_foreach_instr_safe(instr, block) {
 147       if (instr->type != nir_instr_type_intrinsic)
 148          continue;
 149
 150       nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 151
 152       int idx;
 153       if (intr->intrinsic == nir_intrinsic_load_input) {
 154          for (idx = 0; idx < state->colors_count; idx++) {
 155             unsigned drvloc =
 156                state->colors[idx].front->data.driver_location;
 157             if (nir_intrinsic_base(intr) == drvloc) {
 158                assert(nir_src_is_const(intr->src[0]));
 159                break;
 160             }
 161          }
 162       } else if (intr->intrinsic == nir_intrinsic_load_deref) {
 163          nir_variable *var = nir_intrinsic_get_var(intr, 0);
 164          if (var->data.mode != nir_var_shader_in)
 165             continue;
 166
 167          for (idx = 0; idx < state->colors_count; idx++) {
 168             unsigned loc = state->colors[idx].front->data.location;
 169             if (var->data.location == loc)
 170                break;
 171          }
 172       } else
 173          continue;
 174
 175       if (idx == state->colors_count)
 176          continue;
 177
 178       /* replace load_input(COLn) with
 179        * bcsel(load_system_value(FACE), load_input(COLn), load_input(BFCn))
 180        */
 181       b->cursor = nir_before_instr(&intr->instr);
 182       /* gl_FrontFace is a boolean but the intrinsic constructor creates
 183        * 32-bit value by default.
 184        */
 185       nir_ssa_def *face;
 186       if (state->face_sysval)
 187          face = nir_load_front_face(b, 1);
 188       else
 189          face = nir_load_var(b, state->face);
 190
 191       nir_ssa_def *front, *back;
 192       if (intr->intrinsic == nir_intrinsic_load_deref) {
 193          front = nir_load_var(b, state->colors[idx].front);
 194          back  = nir_load_var(b, state->colors[idx].back);
 195       } else {
 196          front = load_input(b, state->colors[idx].front);
 197          back  = load_input(b, state->colors[idx].back);
 198       }
 199       nir_ssa_def *color = nir_bcsel(b, face, front, back);
 200
 201       assert(intr->dest.is_ssa);
 202       nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(color));
 203    }
 204
 205    return true;
 206 }
 207
 208 static void
 209 nir_lower_two_sided_color_impl(nir_function_impl *impl,
 210                                lower_2side_state *state)
 211 {
 212    nir_builder *b = &state->b;
 213
 214    nir_builder_init(b, impl);
 215
 216    nir_foreach_block(block, impl) {
 217       nir_lower_two_sided_color_block(block, state);
 218    }
 219
 220    nir_metadata_preserve(impl, nir_metadata_block_index |
 221                                nir_metadata_dominance);
 222 }
 223
 224 void
 225 nir_lower_two_sided_color(nir_shader *shader, bool face_sysval)
 226 {
 227    lower_2side_state state = {
 228       .shader = shader,
 229       .face_sysval = face_sysval,
 230    };
 231
 232    if (shader->info.stage != MESA_SHADER_FRAGMENT)
 233       return;
 234
 235    if (setup_inputs(&state) != 0)
 236       return;
 237
 238    nir_foreach_function(function, shader) {
 239       if (function->impl)
 240          nir_lower_two_sided_color_impl(function->impl, &state);
 241    }
 242
 243 }