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
28 /**
29 * This pass adds <0.5, 0.5> to all uses of gl_FragCoord.
30 *
31 * Run before nir_lower_io().
32 *
33 * For a more full featured pass, consider using nir_lower_wpos_ytransform(),
34 * which can handle pixel center integer / half integer, and origin lower
35 * left / upper left transformations.
36 *
37 * This simple pass is primarily intended for use by Vulkan drivers on
38 * hardware which provides an integer pixel center. Vulkan mandates that
39 * the pixel center must be half-integer, and also that the coordinate
40 * system's origin must be upper left. This means that there's no need
41 * for a uniform - we can always just add a constant. In the case that
42 * sample shading is enabled, Vulkan expects FragCoord to include sample
43 * positions.
44 */
45
46 static void
update_fragcoord(nir_builder * b,nir_intrinsic_instr * intr)47 update_fragcoord(nir_builder *b, nir_intrinsic_instr *intr)
48 {
49 nir_def *wpos = &intr->def;
50
51 b->cursor = nir_after_instr(&intr->instr);
52
53 nir_def *spos = nir_load_sample_pos_or_center(b);
54
55 wpos = nir_fadd(b, wpos,
56 nir_vec4(b,
57 nir_channel(b, spos, 0),
58 nir_channel(b, spos, 1),
59 nir_imm_float(b, 0.0f),
60 nir_imm_float(b, 0.0f)));
61
62 nir_def_rewrite_uses_after(&intr->def, wpos,
63 wpos->parent_instr);
64 }
65
66 static bool
lower_wpos_center_instr(nir_builder * b,nir_intrinsic_instr * intr,void * data)67 lower_wpos_center_instr(nir_builder *b, nir_intrinsic_instr *intr, void *data)
68 {
69 if (intr->intrinsic != nir_intrinsic_load_frag_coord)
70 return false;
71
72 update_fragcoord(b, intr);
73 return true;
74 }
75
76 bool
nir_lower_wpos_center(nir_shader * shader)77 nir_lower_wpos_center(nir_shader *shader)
78 {
79 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
80
81 return nir_shader_intrinsics_pass(shader, lower_wpos_center_instr,
82 nir_metadata_block_index |
83 nir_metadata_dominance,
84 NULL);
85 }
86