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
lower_fragcoord_wtrans_filter(const nir_instr * instr,UNUSED const void * _options)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 *
lower_fragcoord_wtrans_impl(nir_builder * b,nir_instr * instr,UNUSED void * _options)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
nir_lower_fragcoord_wtrans(nir_shader * shader)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 }
76