src/compiler/nir/nir_lower_fragcoord_wtrans.c

   1 /*
   2  * Copyright (C) 2019 Andreas Baierl
   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
  24 #include "nir.h"
  25 #include "nir_builder.h"
  26
  27 /* Lower gl_FragCoord and transform the w component
  28  * according to the following pseudocode:
  29  *
  30  *    gl_FragCoord.xyz = gl_FragCoord_orig.xyz
  31  *    gl_FragCoord.w = 1.0 / gl_FragCoord_orig.w
  32  *
  33  */
  34
  35 static bool
  36 lower_fragcoord_wtrans_filter(const nir_instr *instr, UNUSED const void *_options)
  37 {
  38    if (instr->type != nir_instr_type_intrinsic)
  39       return false;
  40
  41    nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
  42    if (intr->intrinsic == nir_intrinsic_load_frag_coord)
  43       return true;
  44
  45    if (intr->intrinsic != nir_intrinsic_load_deref)
  46       return false;
  47
  48    nir_variable *var = nir_intrinsic_get_var(intr, 0);
  49    return var->data.location == VARYING_SLOT_POS;
  50 }
  51
  52 static nir_ssa_def *
  53 lower_fragcoord_wtrans_impl(nir_builder *b, nir_instr *instr,
  54                             UNUSED void *_options)
  55 {
  56    nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
  57
  58    return nir_vec4(b,
  59                    nir_channel(b, &intr->dest.ssa, 0),
  60                    nir_channel(b, &intr->dest.ssa, 1),
  61                    nir_channel(b, &intr->dest.ssa, 2),
  62                    nir_frcp(b, nir_channel(b, &intr->dest.ssa, 3)));
  63 }
  64
  65 bool
  66 nir_lower_fragcoord_wtrans(nir_shader *shader)
  67 {
  68    assert(shader->info.stage == MESA_SHADER_FRAGMENT);
  69
  70    return nir_shader_lower_instructions(shader,
  71                                         lower_fragcoord_wtrans_filter,
  72                                         lower_fragcoord_wtrans_impl,
  73                                         NULL);
  74
  75 }