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    shader->num_inputs++;     /* TODO use type_size() */
  64
  65    return var;
  66 }
  67
  68 static nir_ssa_def *
  69 load_input(nir_builder *b, nir_variable *in)
  70 {
  71    nir_intrinsic_instr *load;
  72
  73    load = nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_input);
  74    load->num_components = 4;
  75    load->const_index[0] = in->data.driver_location;
  76    nir_ssa_dest_init(&load->instr, &load->dest, 4, 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    int maxloc = -1;
  86
  87    /* find color/face inputs: */
  88    nir_foreach_variable(var, &state->shader->inputs) {
  89       int loc = var->data.driver_location;
  90
  91       /* keep track of last used driver-location.. we'll be
  92        * appending BCLr/FACE after last existing input:
  93        */
  94       maxloc = MAX2(maxloc, loc);
  95
  96       switch (var->data.location) {
  97       case VARYING_SLOT_COL0:
  98       case VARYING_SLOT_COL1:
  99          assert(state->colors_count < ARRAY_SIZE(state->colors));
 100          state->colors[state->colors_count].front = var;
 101          state->colors_count++;
 102          break;
 103       case VARYING_SLOT_FACE:
 104          state->face = var;
 105          break;
 106       }
 107    }
 108
 109    /* if we don't have any color inputs, nothing to do: */
 110    if (state->colors_count == 0)
 111       return -1;
 112
 113    /* if we don't already have one, insert a FACE input: */
 114    if (!state->face) {
 115       state->face = create_input(state->shader, ++maxloc, VARYING_SLOT_FACE);
 116       state->face->data.interpolation = INTERP_QUALIFIER_FLAT;
 117    }
 118
 119    /* add required back-face color inputs: */
 120    for (int i = 0; i < state->colors_count; i++) {
 121       gl_varying_slot slot;
 122
 123       if (state->colors[i].front->data.location == VARYING_SLOT_COL0)
 124          slot = VARYING_SLOT_BFC0;
 125       else
 126          slot = VARYING_SLOT_BFC1;
 127
 128       state->colors[i].back = create_input(state->shader, ++maxloc, slot);
 129    }
 130
 131    return 0;
 132 }
 133
 134 static bool
 135 nir_lower_two_sided_color_block(nir_block *block, void *void_state)
 136 {
 137    lower_2side_state *state = void_state;
 138    nir_builder *b = &state->b;
 139
 140    nir_foreach_instr_safe(block, instr) {
 141       if (instr->type != nir_instr_type_intrinsic)
 142          continue;
 143
 144       nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 145
 146       if (intr->intrinsic != nir_intrinsic_load_input)
 147          continue;
 148
 149       int idx;
 150       for (idx = 0; idx < state->colors_count; idx++) {
 151          unsigned drvloc =
 152             state->colors[idx].front->data.driver_location;
 153          if (intr->const_index[0] == drvloc) {
 154             break;
 155          }
 156       }
 157
 158       if (idx == state->colors_count)
 159          continue;
 160
 161       /* replace load_input(COLn) with
 162        * bcsel(load_input(FACE), load_input(COLn), load_input(BFCn))
 163        */
 164       b->cursor = nir_before_instr(&intr->instr);
 165       nir_ssa_def *face  = nir_channel(b, load_input(b, state->face), 0);
 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 *cond  = nir_flt(b, face, nir_imm_float(b, 0.0));
 169       nir_ssa_def *color = nir_bcsel(b, cond, back, front);
 170
 171       assert(intr->dest.is_ssa);
 172       nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(color));
 173    }
 174
 175    return true;
 176 }
 177
 178 static void
 179 nir_lower_two_sided_color_impl(nir_function_impl *impl,
 180                                lower_2side_state *state)
 181 {
 182    nir_builder *b = &state->b;
 183
 184    nir_builder_init(b, impl);
 185
 186    nir_foreach_block(impl, nir_lower_two_sided_color_block, state);
 187
 188    nir_metadata_preserve(impl, nir_metadata_block_index |
 189                                nir_metadata_dominance);
 190 }
 191
 192 void
 193 nir_lower_two_sided_color(nir_shader *shader)
 194 {
 195    lower_2side_state state = {
 196       .shader = shader,
 197    };
 198
 199    if (shader->stage != MESA_SHADER_FRAGMENT)
 200       return;
 201
 202    if (setup_inputs(&state) != 0)
 203       return;
 204
 205    nir_foreach_overload(shader, overload) {
 206       if (overload->impl)
 207          nir_lower_two_sided_color_impl(overload->impl, &state);
 208    }
 209
 210 }