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