1 /*
2 * Copyright © 2015 Red Hat
3 * Copyright © 2016 Intel Corporation
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
22 * IN THE SOFTWARE.
23 */
24
25 #include "nir.h"
26 #include "nir_builder.h"
27 #include "program/prog_instruction.h"
28
29 /**
30 * This pass adds <0.5, 0.5> to all uses of gl_FragCoord.
31 *
32 * Run before nir_lower_io().
33 *
34 * For a more full featured pass, consider using nir_lower_wpos_ytransform(),
35 * which can handle pixel center integer / half integer, and origin lower
36 * left / upper left transformations.
37 *
38 * This simple pass is primarily intended for use by Vulkan drivers on
39 * hardware which provides an integer pixel center. Vulkan mandates that
40 * the pixel center must be half-integer, and also that the coordinate
41 * system's origin must be upper left. This means that there's no need
42 * for a uniform - we can always just add a constant. In the case that
43 * sample shading is enabled, Vulkan expects FragCoord to include sample
44 * positions.
45 */
46
47 static void
update_fragcoord(nir_builder * b,nir_intrinsic_instr * intr)48 update_fragcoord(nir_builder *b, nir_intrinsic_instr *intr)
49 {
50 nir_ssa_def *wpos = &intr->dest.ssa;
51
52 assert(intr->dest.is_ssa);
53
54 b->cursor = nir_after_instr(&intr->instr);
55
56 nir_ssa_def *spos = nir_load_sample_pos_or_center(b);
57
58 wpos = nir_fadd(b, wpos,
59 nir_vec4(b,
60 nir_channel(b, spos, 0),
61 nir_channel(b, spos, 1),
62 nir_imm_float(b, 0.0f),
63 nir_imm_float(b, 0.0f)));
64
65 nir_ssa_def_rewrite_uses_after(&intr->dest.ssa, wpos,
66 wpos->parent_instr);
67 }
68
69 static bool
lower_wpos_center_block(nir_builder * b,nir_block * block)70 lower_wpos_center_block(nir_builder *b, nir_block *block)
71 {
72 bool progress = false;
73
74 nir_foreach_instr(instr, block) {
75 if (instr->type == nir_instr_type_intrinsic) {
76 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
77 if (intr->intrinsic == nir_intrinsic_load_frag_coord) {
78 update_fragcoord(b, intr);
79 progress = true;
80 }
81 }
82 }
83
84 return progress;
85 }
86
87 bool
nir_lower_wpos_center(nir_shader * shader)88 nir_lower_wpos_center(nir_shader *shader)
89 {
90 bool progress = false;
91 nir_builder b;
92
93 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
94
95 nir_foreach_function(function, shader) {
96 if (function->impl) {
97 nir_builder_init(&b, function->impl);
98
99 nir_foreach_block(block, function->impl) {
100 progress = lower_wpos_center_block(&b, block) ||
101 progress;
102 }
103 nir_metadata_preserve(function->impl, nir_metadata_block_index |
104 nir_metadata_dominance);
105 }
106 }
107
108 return progress;
109 }
110