src/compiler/nir/nir_lower_fragcolor.c

   1 /*
   2  * Copyright © 2020 Mike Blumenkrantz
   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  *    Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
  25  */
  26
  27 #include "nir.h"
  28 #include "nir_builder.h"
  29
  30 /**
  31  * This pass splits gl_FragColor into gl_FragData[0-7] for drivers which handle
  32  * the former but not the latter, e.g., zink.
  33  */
  34
  35 /*
  36  If a fragment shader writes to "gl_FragColor", DrawBuffersIndexedEXT
  37  specifies a set of draw buffers into which the color written to
  38  "gl_FragColor" is written. If a fragment shader writes to
  39  gl_FragData, DrawBuffersIndexedEXT specifies a set of draw buffers
  40  into which each of the multiple output colors defined by these
  41  variables are separately written. If a fragment shader writes to
  42  neither gl_FragColor nor gl_FragData, the values of the fragment
  43  colors following shader execution are undefined, and may differ
  44  for each fragment color.
  45
  46  - EXT_multiview_draw_buffers
  47
  48  */
  49
  50 static bool
  51 lower_fragcolor_instr(nir_intrinsic_instr *instr, nir_builder *b)
  52 {
  53    nir_variable *out;
  54    if (instr->intrinsic != nir_intrinsic_store_deref)
  55       return false;
  56
  57    out = nir_deref_instr_get_variable(nir_src_as_deref(instr->src[0]));
  58    if (out->data.location != FRAG_RESULT_COLOR || out->data.mode != nir_var_shader_out)
  59       return false;
  60    b->cursor = nir_after_instr(&instr->instr);
  61
  62    nir_ssa_def *frag_color = nir_load_var(b, out);
  63    ralloc_free(out->name);
  64    out->name = ralloc_strdup(out, "gl_FragData[0]");
  65
  66    /* translate gl_FragColor -> gl_FragData since this is already handled */
  67    out->data.location = FRAG_RESULT_DATA0;
  68    nir_component_mask_t writemask = nir_intrinsic_write_mask(instr);
  69
  70    for (unsigned i = 1; i < 8; i++) {
  71       char name[16];
  72       snprintf(name, sizeof(name), "gl_FragData[%u]", i);
  73       nir_variable *out_color = nir_variable_create(b->shader, nir_var_shader_out,
  74                                                    glsl_vec4_type(),
  75                                                    name);
  76       out_color->data.location = FRAG_RESULT_DATA0 + i;
  77       out_color->data.driver_location = i;
  78       out_color->data.index = out->data.index;
  79       nir_store_var(b, out_color, frag_color, writemask);
  80    }
  81    return true;
  82 }
  83
  84 bool
  85 nir_lower_fragcolor(nir_shader *shader)
  86 {
  87    bool progress = false;
  88
  89    if (shader->info.stage != MESA_SHADER_FRAGMENT)
  90       return false;
  91
  92    nir_foreach_function(function, shader) {
  93       if (function->impl) {
  94          nir_builder builder;
  95          nir_builder_init(&builder, function->impl);
  96          nir_foreach_block(block, function->impl) {
  97             nir_foreach_instr_safe(instr, block) {
  98                if (instr->type == nir_instr_type_intrinsic)
  99                   progress |= lower_fragcolor_instr(nir_instr_as_intrinsic(instr),
 100                                                     &builder);
 101             }
 102          }
 103
 104          nir_metadata_preserve(function->impl, nir_metadata_block_index | nir_metadata_dominance);
 105       }
 106    }
 107
 108    return progress;
 109 }