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(nir_builder * b,nir_intrinsic_instr * intr,UNUSED void * _options)36 lower_fragcoord_wtrans(nir_builder *b, nir_intrinsic_instr *intr,
37 UNUSED void *_options)
38 {
39 switch (intr->intrinsic) {
40 case nir_intrinsic_load_deref: {
41 nir_deref_instr *deref = nir_src_as_deref(intr->src[0]);
42 if (!nir_deref_mode_must_be(deref, nir_var_shader_in))
43 return false;
44 nir_variable *var = nir_intrinsic_get_var(intr, 0);
45 if (var->data.location != VARYING_SLOT_POS)
46 return false;
47 break;
48 }
49 case nir_intrinsic_load_frag_coord:
50 break;
51 default:
52 return false;
53 }
54
55 /* W is not read. */
56 if (intr->def.num_components < 4)
57 return false;
58
59 b->cursor = nir_after_instr(&intr->instr);
60
61 nir_def *invert = nir_frcp(b, nir_channel(b, &intr->def, 3));
62
63 nir_def *frag_coord = nir_vector_insert_imm(b, &intr->def, invert, 3);
64
65 nir_def_rewrite_uses_after(&intr->def, frag_coord,
66 frag_coord->parent_instr);
67
68 return true;
69 }
70
71 bool
nir_lower_fragcoord_wtrans(nir_shader * shader)72 nir_lower_fragcoord_wtrans(nir_shader *shader)
73 {
74 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
75
76 return nir_shader_intrinsics_pass(shader,
77 lower_fragcoord_wtrans,
78 nir_metadata_control_flow,
79 NULL);
80 }
81