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, unsigned drvloc, 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 = drvloc;
  55    var->type = glsl_vec4_type();
  56    var->data.mode = nir_var_shader_in;
  57    var->name = ralloc_asprintf(var, "in_%d", drvloc);
  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    shader->num_inputs++;     /* TODO use type_size() */
  65
  66    return var;
  67 }
  68
  69 static nir_ssa_def *
  70 load_input(nir_builder *b, nir_variable *in)
  71 {
  72    nir_intrinsic_instr *load;
  73
  74    load = nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_input);
  75    load->num_components = 4;
  76    nir_intrinsic_set_base(load, in->data.driver_location);
  77    load->src[0] = nir_src_for_ssa(nir_imm_int(b, 0));
  78    nir_ssa_dest_init(&load->instr, &load->dest, 4, 32, NULL);
  79    nir_builder_instr_insert(b, &load->instr);
  80
  81    return &load->dest.ssa;
  82 }
  83
  84 static int
  85 setup_inputs(lower_2side_state *state)
  86 {
  87    int maxloc = -1;
  88
  89    /* find color inputs: */
  90    nir_foreach_variable(var, &state->shader->inputs) {
  91       int loc = var->data.driver_location;
  92
  93       /* keep track of last used driver-location.. we'll be
  94        * appending BCLr after last existing input:
  95        */
  96       maxloc = MAX2(maxloc, loc);
  97
  98       switch (var->data.location) {
  99       case VARYING_SLOT_COL0:
 100       case VARYING_SLOT_COL1:
 101          assert(state->colors_count < ARRAY_SIZE(state->colors));
 102          state->colors[state->colors_count].front = var;
 103          state->colors_count++;
 104          break;
 105       }
 106    }
 107
 108    /* if we don't have any color inputs, nothing to do: */
 109    if (state->colors_count == 0)
 110       return -1;
 111
 112    /* add required back-face color inputs: */
 113    for (int i = 0; i < state->colors_count; i++) {
 114       gl_varying_slot slot;
 115
 116       if (state->colors[i].front->data.location == VARYING_SLOT_COL0)
 117          slot = VARYING_SLOT_BFC0;
 118       else
 119          slot = VARYING_SLOT_BFC1;
 120
 121       state->colors[i].back = create_input(
 122             state->shader, ++maxloc, slot,
 123             state->colors[i].front->data.interpolation);
 124    }
 125
 126    return 0;
 127 }
 128
 129 static bool
 130 nir_lower_two_sided_color_block(nir_block *block,
 131                                 lower_2side_state *state)
 132 {
 133    nir_builder *b = &state->b;
 134
 135    nir_foreach_instr_safe(instr, block) {
 136       if (instr->type != nir_instr_type_intrinsic)
 137          continue;
 138
 139       nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 140
 141       if (intr->intrinsic != nir_intrinsic_load_input)
 142          continue;
 143
 144       int idx;
 145       for (idx = 0; idx < state->colors_count; idx++) {
 146          unsigned drvloc =
 147             state->colors[idx].front->data.driver_location;
 148          if (nir_intrinsic_base(intr) == drvloc) {
 149             assert(nir_src_is_const(intr->src[0]));
 150             break;
 151          }
 152       }
 153
 154       if (idx == state->colors_count)
 155          continue;
 156
 157       /* replace load_input(COLn) with
 158        * bcsel(load_system_value(FACE), load_input(COLn), load_input(BFCn))
 159        */
 160       b->cursor = nir_before_instr(&intr->instr);
 161       nir_ssa_def *face = nir_load_front_face(b);
 162       /* gl_FrontFace is a boolean but the intrinsic constructor creates
 163        * 32-bit value by default.
 164        */
 165       face->bit_size = 1;
 166       nir_ssa_def *front = load_input(b, state->colors[idx].front);
 167       nir_ssa_def *back  = load_input(b, state->colors[idx].back);
 168       nir_ssa_def *color = nir_bcsel(b, face, front, back);
 169
 170       assert(intr->dest.is_ssa);
 171       nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(color));
 172    }
 173
 174    return true;
 175 }
 176
 177 static void
 178 nir_lower_two_sided_color_impl(nir_function_impl *impl,
 179                                lower_2side_state *state)
 180 {
 181    nir_builder *b = &state->b;
 182
 183    nir_builder_init(b, impl);
 184
 185    nir_foreach_block(block, impl) {
 186       nir_lower_two_sided_color_block(block, state);
 187    }
 188
 189    nir_metadata_preserve(impl, nir_metadata_block_index |
 190                                nir_metadata_dominance);
 191 }
 192
 193 void
 194 nir_lower_two_sided_color(nir_shader *shader)
 195 {
 196    lower_2side_state state = {
 197       .shader = shader,
 198    };
 199
 200    if (shader->info.stage != MESA_SHADER_FRAGMENT)
 201       return;
 202
 203    if (setup_inputs(&state) != 0)
 204       return;
 205
 206    nir_foreach_function(function, shader) {
 207       if (function->impl)
 208          nir_lower_two_sided_color_impl(function->impl, &state);
 209    }
 210
 211 }