src/glsl/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    nir_variable *face;
  36    struct {
  37       nir_variable *front;        /* COLn */
  38       nir_variable *back;         /* BFCn */
  39    } colors[MAX_COLORS];
  40    int colors_count;
  41 } lower_2side_state;
  42
  43
  44 /* Lowering pass for fragment shaders to emulated two-sided-color.  For
  45  * each COLOR input, a corresponding BCOLOR input is created, and bcsel
  46  * instruction used to select front or back color based on FACE.
  47  */
  48
  49 static nir_variable *
  50 create_input(nir_shader *shader, unsigned drvloc, gl_varying_slot slot)
  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
  61    exec_list_push_tail(&shader->inputs, &var->node);
  62
  63    return var;
  64 }
  65
  66 static nir_ssa_def *
  67 load_input(nir_builder *b, nir_variable *in)
  68 {
  69    nir_intrinsic_instr *load;
  70
  71    load = nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_input);
  72    load->num_components = 4;
  73    load->const_index[0] = in->data.driver_location;
  74    nir_ssa_dest_init(&load->instr, &load->dest, 4, NULL);
  75    nir_builder_instr_insert(b, &load->instr);
  76
  77    return &load->dest.ssa;
  78 }
  79
  80 static int
  81 setup_inputs(lower_2side_state *state)
  82 {
  83    int maxloc = -1;
  84
  85    /* find color/face inputs: */
  86    foreach_list_typed(nir_variable, var, node, &state->shader->inputs) {
  87       int loc = var->data.driver_location;
  88
  89       /* keep track of last used driver-location.. we'll be
  90        * appending BCLr/FACE after last existing input:
  91        */
  92       maxloc = MAX2(maxloc, loc);
  93
  94       switch (var->data.location) {
  95       case VARYING_SLOT_COL0:
  96       case VARYING_SLOT_COL1:
  97          assert(state->colors_count < ARRAY_SIZE(state->colors));
  98          state->colors[state->colors_count].front = var;
  99          state->colors_count++;
 100          break;
 101       case VARYING_SLOT_FACE:
 102          state->face = var;
 103          break;
 104       }
 105    }
 106
 107    /* if we don't have any color inputs, nothing to do: */
 108    if (state->colors_count == 0)
 109       return -1;
 110
 111    /* if we don't already have one, insert a FACE input: */
 112    if (!state->face) {
 113       state->face = create_input(state->shader, ++maxloc, VARYING_SLOT_FACE);
 114       state->face->data.interpolation = INTERP_QUALIFIER_FLAT;
 115    }
 116
 117    /* add required back-face color inputs: */
 118    for (int i = 0; i < state->colors_count; i++) {
 119       gl_varying_slot slot;
 120
 121       if (state->colors[i].front->data.location == VARYING_SLOT_COL0)
 122          slot = VARYING_SLOT_BFC0;
 123       else
 124          slot = VARYING_SLOT_BFC1;
 125
 126       state->colors[i].back = create_input(state->shader, ++maxloc, slot);
 127    }
 128
 129    return 0;
 130 }
 131
 132 static bool
 133 nir_lower_two_sided_color_block(nir_block *block, void *void_state)
 134 {
 135    lower_2side_state *state = void_state;
 136    nir_builder *b = &state->b;
 137
 138    nir_foreach_instr_safe(block, instr) {
 139       if (instr->type != nir_instr_type_intrinsic)
 140          continue;
 141
 142       nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 143
 144       if (intr->intrinsic != nir_intrinsic_load_input)
 145          continue;
 146
 147       int idx;
 148       for (idx = 0; idx < state->colors_count; idx++) {
 149          unsigned drvloc =
 150             state->colors[idx].front->data.driver_location;
 151          if (intr->const_index[0] == drvloc) {
 152             break;
 153          }
 154       }
 155
 156       if (idx == state->colors_count)
 157          continue;
 158
 159       /* replace load_input(COLn) with
 160        * bcsel(load_input(FACE), load_input(COLn), load_input(BFCn))
 161        */
 162       b->cursor = nir_before_instr(&intr->instr);
 163       nir_ssa_def *face  = nir_channel(b, load_input(b, state->face), 0);
 164       nir_ssa_def *front = load_input(b, state->colors[idx].front);
 165       nir_ssa_def *back  = load_input(b, state->colors[idx].back);
 166       nir_ssa_def *cond  = nir_flt(b, face, nir_imm_float(b, 0.0));
 167       nir_ssa_def *color = nir_bcsel(b, cond, back, front);
 168
 169       assert(intr->dest.is_ssa);
 170       nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(color));
 171    }
 172
 173    return true;
 174 }
 175
 176 static void
 177 nir_lower_two_sided_color_impl(nir_function_impl *impl,
 178                                lower_2side_state *state)
 179 {
 180    nir_builder *b = &state->b;
 181
 182    nir_builder_init(b, impl);
 183
 184    nir_foreach_block(impl, nir_lower_two_sided_color_block, state);
 185
 186    nir_metadata_preserve(impl, nir_metadata_block_index |
 187                                nir_metadata_dominance);
 188 }
 189
 190 void
 191 nir_lower_two_sided_color(nir_shader *shader)
 192 {
 193    lower_2side_state state = {
 194       .shader = shader,
 195    };
 196
 197    if (shader->stage != MESA_SHADER_FRAGMENT)
 198       return;
 199
 200    if (setup_inputs(&state) != 0)
 201       return;
 202
 203    nir_foreach_overload(shader, overload) {
 204       if (overload->impl)
 205          nir_lower_two_sided_color_impl(overload->impl, &state);
 206    }
 207
 208 }