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 {
  51    nir_variable *var = rzalloc(shader, nir_variable);
  52
  53    var->data.driver_location = drvloc;
  54    var->type = glsl_vec4_type();
  55    var->data.mode = nir_var_shader_in;
  56    var->name = ralloc_asprintf(var, "in_%d", drvloc);
  57    var->data.index = 0;
  58    var->data.location = slot;
  59
  60    exec_list_push_tail(&shader->inputs, &var->node);
  61
  62    shader->num_inputs++;     /* TODO use type_size() */
  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    int maxloc = -1;
  86
  87    /* find color 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 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       }
 104    }
 105
 106    /* if we don't have any color inputs, nothing to do: */
 107    if (state->colors_count == 0)
 108       return -1;
 109
 110    /* add required back-face color inputs: */
 111    for (int i = 0; i < state->colors_count; i++) {
 112       gl_varying_slot slot;
 113
 114       if (state->colors[i].front->data.location == VARYING_SLOT_COL0)
 115          slot = VARYING_SLOT_BFC0;
 116       else
 117          slot = VARYING_SLOT_BFC1;
 118
 119       state->colors[i].back = create_input(state->shader, ++maxloc, slot);
 120    }
 121
 122    return 0;
 123 }
 124
 125 static bool
 126 nir_lower_two_sided_color_block(nir_block *block,
 127                                 lower_2side_state *state)
 128 {
 129    nir_builder *b = &state->b;
 130
 131    nir_foreach_instr_safe(instr, block) {
 132       if (instr->type != nir_instr_type_intrinsic)
 133          continue;
 134
 135       nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
 136
 137       if (intr->intrinsic != nir_intrinsic_load_input)
 138          continue;
 139
 140       int idx;
 141       for (idx = 0; idx < state->colors_count; idx++) {
 142          unsigned drvloc =
 143             state->colors[idx].front->data.driver_location;
 144          if (nir_intrinsic_base(intr) == drvloc) {
 145             assert(nir_src_as_const_value(intr->src[0]));
 146             break;
 147          }
 148       }
 149
 150       if (idx == state->colors_count)
 151          continue;
 152
 153       /* replace load_input(COLn) with
 154        * bcsel(load_system_value(FACE), load_input(COLn), load_input(BFCn))
 155        */
 156       b->cursor = nir_before_instr(&intr->instr);
 157       nir_ssa_def *face  = nir_load_system_value(b,
 158                                                  nir_intrinsic_load_front_face,
 159                                                  0);
 160       nir_ssa_def *front = load_input(b, state->colors[idx].front);
 161       nir_ssa_def *back  = load_input(b, state->colors[idx].back);
 162       nir_ssa_def *color = nir_bcsel(b, face, front, back);
 163
 164       assert(intr->dest.is_ssa);
 165       nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(color));
 166    }
 167
 168    return true;
 169 }
 170
 171 static void
 172 nir_lower_two_sided_color_impl(nir_function_impl *impl,
 173                                lower_2side_state *state)
 174 {
 175    nir_builder *b = &state->b;
 176
 177    nir_builder_init(b, impl);
 178
 179    nir_foreach_block(block, impl) {
 180       nir_lower_two_sided_color_block(block, state);
 181    }
 182
 183    nir_metadata_preserve(impl, nir_metadata_block_index |
 184                                nir_metadata_dominance);
 185 }
 186
 187 void
 188 nir_lower_two_sided_color(nir_shader *shader)
 189 {
 190    lower_2side_state state = {
 191       .shader = shader,
 192    };
 193
 194    if (shader->stage != MESA_SHADER_FRAGMENT)
 195       return;
 196
 197    if (setup_inputs(&state) != 0)
 198       return;
 199
 200    nir_foreach_function(function, shader) {
 201       if (function->impl)
 202          nir_lower_two_sided_color_impl(function->impl, &state);
 203    }
 204
 205 }